Note: Descriptions are shown in the official language in which they were submitted.
106~53Z
rhis ~nvention r~lates to no~el curable
compositions having ~mproved fabrication charact~ristic~
to a m~thod o~ producing such compo~ition~, ~nd to th~ u~e
o the compo~itions for mak~ng composite materlals which
S under certain circumstance~ possess desirable combinat~ons
of st~ffness, strength and ~oughness and may also possess
other useful properties such a~ good abra~lon resistance
and resistance to fire. ~ore particularly, the inv~ention
relates to stable fluid, curable compositions which
1~ c~mpr~se a ~ispersion of particles o~ one or m~re inorganic
materials in a polymerisable organic liquid precursor, to
a method of producing such compositions and to ~he production
by curing thereo~ o multi-component composite mater~als
which comprise an organic polymer matrix and a par~iculate
inorgan~c reinforcing phase d~spersed in9 and bonded to,
the matrix.
It is known to extend polymers by the
incorporation of non-fibrous particulate fillers in order
to cheapen th~m and/or to produce a stiffer materi~
Simple admixture of such a filler and a polymer usual}y
results, however, in a very weak and britt~e product~
More recently, it has been demon~trated that stronger composite
materials can be obtained if a strong bond i5 ensured
between the polymer matrix and the filler particles~ We
hava now found that by ~ploying filler particles which are
inely di~ided and are stably dispersed at hlgh particle
concentrations in a poly~er matrix with ~he aid of a
poly~eric disp~rsan~ it is possible ~o ob~ain comp~site
,~ ~
~LO1~;5532
materials of gr~at utility which can b~ simultaneously
stiffer, stronger and tougher than known composltes. We
haYe also found that the use o~ such a disp~rsant makes
it possible to ~ormulate highly fluid c:ompositions
comprising high concentrations of finely divided f~ller
particles in polymerisable liquids~ surh
compositions being capabie of beinq cured to yield directly
the improved composlte materials referred to.
According to one aspect of the present invention
there is pro~id2d a stable, fluid, mould~ble and curable
composition ~ompri~ing (A~ an organic liquid
which is polymerisable to ~orm a ~olid polymer and has a
viscosity not gr~ater than 50 poise at the temperature at
which the composition is to be moulded, (B) finely divided
particles as herelnafter de~ined of one or more inorganic
fillers, the said particle3 constituting at least 20X by
volume o~ the total compo~tion, and tC ) a polymeric
dispersant a~ her~inafter de~ine~ whereby the filler
par~lcles are m~intained in a state of stably de~locculated
dispersion in the polymer~sable liquid.
By "a poly~erisable organic liquid",
: as component (A) o~ the composition, ls meant harein one
of the following classes of material:-
~(a~ A liquid monom~r, or a liquid mixture o~ monomers,
which can be polymerise~ to form a solid polymer ln which
the repeat units in the polymer chain are linked through
carbon-carbon bonds or by such bonds int~rrupted by
het~ro atoms such as oxygen, ni~roge~ or silicon. Preferably
~L06553;Z
: the polymerisation o the monomer or monomers takes place
without the formation of any elimination product; in
other words, preferred monomers are those whlch polymerise
by bond rearrangement reactions.
S Such reactions may be of the followlng types:-
(i) addition polymerisations o~F v~nyl, vinylidene,or other s~milar unsaturated monomers, ln the
presence of conventional free radical
initiators such as peroxides or azo compounds,
or of conventional cationic or anionic
initlators;
(ii) addition polymerisation~ of ring~opening
cyclic monomers9 using cationic or anionic
initiators;
(iii) bond-rearrangement type condensation reactions,
if desired in the presence of conventional
; catalystsO
ExampIes of such preferred liquid monomers of type
~i) include the ethylenically unsaturated monomers such as the
esters of acrylic and methacrylic acids with aliphatic,
alicyclic or aromatic alcohols containing from 1 to 18 carbon
atoms, for example methyl methacrylate, ethyl methacrylate,
propyl methacrylate, butyl me~hacrylate, ethyl ~crylate~ butyl
; acrylate, 2~ethyl hexyl acrylate, ethylene glycol dimethacrylate,
trimethylolpropane trimethacrylate~ hydroxypropyl methacrylate,
: hydroxyethyl acrylate, dimethylaminoethyl methacrylate and
diethylaminoethyl methacrylate; vinyl aromatic compounds such
as styrene~ vinyl toluene and divinylbenzene, and mixtures of
- 4 -
..~
10~i532
these with mal~lc acid or fum2.ric acid derivatives
such as chlorophenylmaleimide and ~utyl hydrogen
maleate; allyl ethers and e~ters such as allyl diglycol
dicarbonate; and other monomers of this class including
S acrylonitrile, methacrylonitrile, ~inyl esters such as
vinylacetate, vinyl ethers~ vinyl chloride, vinylidene
chloride and vinyl pyrrolidone~
Examples of preferred liquid monomers of type (ii)
include cyclic ethers, in particular epoxides such as
glycidyl ethers, e.g. alkyl and aryl glycidyl ethers,
and glycidyl esters, such as "Cardura" E (Registered
Trade Mark) which is the reaction product of
epichlorohydrin and a mixture of branched Cg ~1
monocarboxylic acids known as "Versatic'1 acid
: lS (Registered Trade Mark)~ Other examples include formals
such as trioxane; lactones
__ _
/
-
/
/
/ , . --
.
_ 5 _
~i5S3Z
and cyclic esters such as ~-propiolactone,
-caprolactone; lactams and cyclic amide~ such as
~ -caprolactam, lauryl lactam, pyrrolidone; cyclic
: siloxanes such as octamethyl cyclotetrasiloxan~.
Further examples of tha preerred class of liquid
: monomers includes the following pairs of co-reactants
which poly~erise by reactions o~ type tili) referred to
above: polyamines and polyisocyanates, polyols and
polyisocyanates and polycarboxylic acids ~or their
anhydrides) and polyepoxldes. Suitable polyamines include
ethylene diamine, hexamethylene diamine, decamethylene
diamine, diethylene triamine, pipera~inet m- and p-xylylene
diamine and m and p-phenylene diamine. Suitable polyols
include ethylene glycol, diethylene glycol, trimethylene
glycol, tetranethylene glycol, hexamethylene glycol,
tetramethyl ethylene glycol, neopentyl glycol,
trlmethylolpropane, glycerolt 1, 2t 6~ hexa~etriol, 1, 3-
and 1, 4- cyclohexane diol and p-xylylene glycol. Suitable
, ~ polyisocyanates include hexamethylene diisocyanate, 2t 4
20 and 2, 6- tolylene diisocyanate and 4, 4'- diisocyanato-
: d1phenyl methane. Suitable polycarboxylic acids or their
anhydrides include succinic acid7 adipic acid, phthalic
anhydride, isophthalic acid, terephthalic acid, trimellitic
acid:, pyromellitic acid and 1, 3- and 1, 4- cyclohexane
dicarboxylic acids. Suitable polyepoxides include the
glycld~l ether~ of 19 4 butane diol 9 glycerol, re~orcinol
~ and bisphen~l A; bis-2, 3-epoxy cyclopenty~ ether.
; 6 _
.
,
;
.
~L~6SS3'~
~b) A mixture o~ one or more preformed polymers with one
or more monomers, the monomer constituent(s~ o~ which can be
polymerised so that a solid polymer product results. The
monomer or monomers may be the same as those described in (a)
above, those which undergo a bond-rearrangement type o~ poly-
merisation being again preferred. The pre~armed polymer or
polymers may be either in solution in the mo~omer constituent
or in a state of dispersion therein; the polymer may be either
the same asV or dif~erent from, the polymer which is pro-
duced by the polymerisation of the monomer constituent. Wherethe preformed polymer is soluble in the monomer constituent,
it may be either compatible or incompatible with the polymer
produced by the polymerisation of the monomer; it may also be
capable of undergoing grafting by the monomer.
The preformed polymer or ~olymers may be produced
by any polymerisation route and, ~or this purposet it is of
no consequen~e whether or not any by-produc~s are formed
during the polymerisation. Thus the polymers may be ma~e by
polymerLsation in the melt or in solution, by suspension
polymerisation or by aqueous or non-aquQous dispersio~ po~y-
merisation techniques, and isolated by conventional methods.
Where the preformed polymer is to be present in the poly-
merisable liquid in the form of dispersed colloidal parti-
cles which are insoluble in the llquid, these particles may
be made by grindin~ bulk pol~mer to the requisite degree or,
~ore conveniently~ they may be produced directly by employing
aqueous or non-aqueous dispersion pol~merisation procedures.
~queous dispersion polymerisation tech~iques are very fully
7 _
~065S32
described in the technical literature; non-aqueOus polymeri-
sation techni~ues are described, for example, in Specifications
Nos. 941,305; 1,052,241; 1,122,397; 1,123,6Ll; 1,143,404;
1,~31,614.
By employing a preformed polymer which is incom-
patible with the polymer formea by curing the monomeric consti-
tuent o~ the polymerisable liquid, one finally obtains a compo-
site material in which the polymer matrix is itself a modified
composite phase, generally having a continuous component
consisting o the polymer $ormed during curing and a disperse
component consisting of particles of the preformed polymer.
In this way, for example, a glassy polymer matrix may be
modified by the incorporation in it of preformed rubbery
polymer particles. Alternatively, the rubber may be initially
in a state of solution in the monomer and be caused to
phase-separate as the polymerisation proceeds. Alternatively,
it may be arranged that strong ionic bonding forces are
developed at the interface between the polymer phases. Such
techniq~ues are well-known in the polymer dispersion and
composites~art.
Examples of mixed polymer/monomer systems suitable
fo~ use in the invention include,
(1) syrups of reactive polymers such as (i) unsaturated
polyesters, vinyl or vinylidene group-terminated urethanes,
hydroxyalkyl acrylic or methacrylic ester adduats of amino-
pIast such as melamine-formaldehyde resins and acrYlic or
: : :
::
- 8 - -
553Z
methacrylic acid adducts of epoxy resins, ~n each
cas~ in combination with and dissolved in one or
more athylenically un~aturated mono~ers; (ii)
mixtures of polyhydroxylic polymers such as ~,~ -
S hydroxylic polyethers, polyesters or polybutadienes
with polyisocyanates; (lii) mixtures of
polyepoxide-containing polymers, such as epoxidised
polybutadienes and novolacs or oligomeric diglycidyl
~ - ethers o~ epichlorhydrin and bisphenol A, with
; 10 polyamines or anhydrides;
(2) syrups of non-reactive polymers dissolved in monomers;
those in which the polymer formed on curing is
compatible with the preformed polymer include
poly(methyl methacrylate)/msthyl methacrylate, and
poly (2, 6-dimethylphenylene ox$de)~styrene. Those
in which the two polymers are incom~atible include
~ polyisoprene~acrylonitrile, poly-(butylacrylate)/
; ~ : methyl methacrylate and cellulose aeetate butyratet
methyl methacrylate;
20 (3) dispersions of polymers in monomers in which they do
:~ ~ not dissolve, such as a polybutadiene microgel,
encapsulated with cross-linked poly(methyl methacrylate),
- : in methyl methacrylate monomer, polyacrylonitrile in
methyl methacrylate or butyl acrylate, cross-linked
: ~ 25 poly-(butyl acrylate) in acrylonitrile and polyvinyl
:
~'
~0~;553Z
chloride in methyl methacrylate.
(c) a partially polymerised material or a pre-polymer,
which is capable o~ polymerising to completion by any of
the known polymerisation mechanisms but preferably by a
bond-rearrangement mechanism as re~erred to in (a) above.
Such pre-polymers include low molecular weight unsaturated
oligomers such as l,2~unsaturated polybutadienes and vinyl-
terminated polyesters; polyepoxides such as epoxidised
novolacs and polybutadienes; and pre-polymers obtained by
partially reacting materials which undergo step-polymerisation,
i.e. those which only yield high molecular wei~ht products
at high degrees of conversion of monomer to polymer; examples
of these materials are the pairs of co-reactants mentioned
in ta~ above which polymerise by reactions of type (iii).
The polymerisable liquid A, whether of class (a),
(b) or ~c), may be such as to produce on polymerisation
either a crystalline polymer or an amorphous polymer, and
in the case of the latter the polymer may be either glassy
or rubbery, that is to say it may have a glass transition
temperature which is either above or below the environmental
temperature respectively. There may be incorporated in the
polymers non-reactive plasticisers such are normally used
with these polymers.
In defining that the polymer-sable organic liquid
should have a viscosity not greater than 50 poise at the
temperature at which the curable composition of the invention
is to be moulded, we have regard to the fact that this is
the temperature at which the viscosity is of greatest
-- 10 -
553Z
practical significance for the fabricatlon of composite
mater~als from the curable composition. If the vi~cosity
at this temperature is too high, the ease with which the
composition can be ~oulded will be diminlshed. However9
it is permissible or a monomer to h~ve a viscosity at room
temperature above the range stated, i~ the moulding is
carried out at an elevated temperature, since viscosity
normally falls with increasing temperature. The
temperatures at which moulding and curing respectively of
the compositions are carried out will not necessarily
coincide.
It is preferred that the viscosity of the
polymerlsable liquid should b~ not greater than 10 polse
at the moulding temperature, ~nd even more preerably
it is not greater than 1 poise at that temperature.
The particulate inorganic filler (~) which is
stably dispersed in ~he polymerisable organic liquid ~A)
according to the invention is characteristical}y a solld
material having a high elastic shear modulus, namely a
modulus of not less than 5 GN~m and pre~erably not less than
10 GN/m~. Alternatively, suitable solid materials may be
defined as those having a Knoop hardness of greater than 100.
Examples of suitable solids include a wide variety of
minerals such as aluminas, ~orms of silica such as quartz~
cristobalite and tridymite~ kaolin and its calcination
products, feldspar, kyanite, olivine, nepheline syenite,
sillimanite, zircon, wollastonite, apatite, aragonite, calcite 9
magnesite, barytes, gypsum and other metal silicates,
11 ~
36553~
aluminates, aluminosilicates, phosphates, sulphates, car-
bonates, sulphides, carbides and oxides; metals, which
may be either brittle ox ductile, such as cast iron, zinc
alloys, alu~inium, bronze ana steel; and arti.ficial materials
such as glasses, porcelain, slag ash and ~orms of carbon
such as coke.
In stating that the particles of the inorganic
filler are finely divided, we mean that the maximum size of
any particle present is 100 microns and that at least 95%
by number of the particles are of a size 10 microns or less..
Preferably more than 99% by number of the particles are of
a size lO microns or less, and in general the nearer the
number proportion o such particles approaches 100% the
better, e.g. a proportion of 99~.999% by number of a size
10 miorons or less g.ives very satisfactory results. It is
at the same time preferred that.the maximum size of any
~ particle present should be 75 microns,-even:more preferred
: that the maximum size should be 50 microns. The finely
divided partic}es:of inorganic filler, whilst conforming
20 to the foregoing definition of particle size, are further-
more defined herein as having a surace area of from 30~/cc
. tQ lm2/cc, preferably from 2~m2/cc to 2m~/cc, as determined
by the B.E.T. ~itrogen absorption method.
The particles of the inorganic filler may have
.broad or narrow size distributions and these may be either
monomodal or polymodal within the stated size ranges. The
particle size of the filler refers to the largest dimensions
of the particles, which may vary from being granular to
- 12 -
.
1065532
being plate-like~ cylindrical or rod-like~ or oblong in
shape. I~ is preferred that the particles be generally
granular in shape, as opposed to plate- or rod-like~ s~nce
the stiffness o composite materials made from the curable
compositions and the ease o~ fabrication o~ the latter into
composite materials are optimised thereby. However~ for
special applications~ particles with length-to-diameter or
length-to-thickness ratlos not greater than 25~1~ for example
certain particle~ o asbestos~ wollastonlte~ silicon carbide or
silicon ~itride "whiskers", kaolin or aluminium or mica
platelets, may be employed.
The particulate filler may consist of only one
of the materials referred to above, or it may consist of
a mixture of two or more such materials. The particles
may be produced by precipitation or atomisation, or ~rom
bulk material by conventional grinding or milling techniques~
This aspect of the invention~is discussed in more detail
below.
It is also preferred that the surfaces of the
particles are at least free of loosely bound water, as
achieved, ~or example, by heating them to lS0C. In some
cases, such as those in whic~ a silane interfacial bonding
agent is used as described ~elow~ t t may be advantageous
to calcine the p~rticle~ at temperatures abo~e 400C~ It is
important that the particles used are not aontaminated by
deliberately introduced low molecular weight sur~ac~_active
materials such a~ the ~atty acids or salt thereo~ with
_ 13 -
1~65S3Z
which fillers as sold commercially are commonly treated.
As already stated, the curable compositions
contain at least 20X by volume of the stably dispersed
particulate inorganic filler, and they may contain up to
90% by volume of that component~ Preferred volume
concentrations of filler, in order to achie~e the most
advantageous properties in the composite materials obtained
by curing the fluid compositions, depend to some extent on
the nature of the solid polymer which is produced ln the
curing process. Where the solid polymar i8 amorphous and
glassy, or where it is crystalline, a preferred concentra~ion
of filler is ~rom 35% to 85% by volume, more preferably
from 50% to 80% by volume, based on the total curable
composition. In cases where the filler particles become
strongly bonded to the solid polymer9 aa described in detail
below, such concentrations o fiIler can result in an
appreciable increase not only in stiffness but also in
strength of the composite materials obtalned on curinglas
compared with the unmodified solid polymer, without significant
loss of toughness. When the solid polymer is rubbery and
the filler particles are again strongly bonded thereto, the
preferred volume concentration of ~iller ranges from 20% to
50%, based on the total curable composition; the elongation
to break and the tear strength properties of the cu7~d
composites are significantly better than those of the
unmodified polymer, with only a moderate increase in lts
stiffness. Concentrations o~ filler above 50% by volume may,
howe~er, be useful in the case of rubbery polymers for
~ 14 ~
:~L0~532
applicatîon in suspension systems, as compression blocks
~or ~ridges or mounting blocks for machinery7 or as sealing
gaskets~
The polymeric dispersant tC) emp}oyed in the
curable compositions is an emphipathic substance containing
at least one chain-like component of molecular weight at
least 500 which is solvated by the polymerisable organic
liquid (A), in the sense that, if this component were
an independent molecule 9 the polymerisable lîquid would be
significantly better than a theta-solvent for it; the
nature of a theta-solvent is discussed in "Polymer Handbook"
(Ed. Brandrup and Immergut, Interscience, 1966)and in
~'Principles of Polymer Chemistry"~ Chapters 12 - 14, (Flory:
Cornell, 1953). More simply, the polymerisable liquid may
be described as being a "good" solvent for the chain-like
component. In addition, the dispersant contains one or
more groupings which are capable of associating with, and
effecting anchoring to, the particles of the inorganic filler
(B)~
Suitable polymeric dispersants may be divided
into the following types, o~ which illustrative but not
li~iting examples are given in the accompanying table:~
1. Simple polymer or copolymer chains solvatahle by
the polymerisable organic liquid and terminated by a single
particle-anchoring group. These may be generally
represented as Xn Ys where X denotes a monomer unit (not
necessarily identical throughout the chain), n is the degree
o~ polymerisation, and Y is a specific anchoring group.
- 15 _
-
~06SS32
The anchoring group may be~ for example t a carboxyl~ amino
sulphate or hydroxyl group, as discussed in more detail
below~ and may be derived either from a suitable ~co)monomer
Utlit or $rom a tran~er a~èn~ present during formation of
the polymer chain. The polymer chain will have a minimum
molecular weight of 500; preferably its molecular weight
is greater than 1500.
2. Random copolymers solvatable by the polymerisable
liquid, in which the mono~er units carry a plurality of
particle-anchoring groups. These may be represented 9 for
example~ by --- XXXYYXXXXY -~_, where X is a monomer unit
conferring on the polymer chain solubility in the
polymerlsable liquid and Y is a monomer unit bearing a
specifi~i anchoring group as in category (1). The copolymer
preerably has a molecular weight greater than 3000c The
monomer units carrying the anchoring groups constitute from
1 - 20% by weight, preferably from 1.5 15~ and more
preferably from 2 - 10%, of the total copolymer.
3. Block copolymers, which may be either simple or
20 multiple:
~i~ Simple AB block copolymers, where A represents a
polymer or copolymer chain sol~a-table by the polymerisable
li~uid and B represents a polymer chain which is not
thus solvatable and thereby functions as a particle-
anchoring group. The molecular weight of the A block
should be greater than 500, preferably greater than
1500, and the weight ratio of the A block to the B blok
is preferably between 3:1 and 1:3.
- 16 -
~06S~i32
tii) Multiple block copolymers, e-90 --- Am Bn Ao Bp
wh~re A and B have the same slgnlfi.ance as in (i)
and the suf~xe~ m, n, o, p --- denote differing
lengths of polymer chain in each sequence of the block.
The molecular weight o each A block is preferably
greater than 1j500 and that of each B block is
preferably not less than 500. The weight ratio of A
blocks to B blocks is preferably the same as in (i).
4. Graft copolymers. These may be of three t~pes,
10 represented by:
(i) Am An
;J ¦ l
-~--; CCCCCCC ------
(ii) Am An Ao
__- CCCDCCDCCC --
(iii) Am An
--__CCCCCCCC
~ I
~ Bo Bp
where A denotes a chain solvatable by the polymerisable
liquid~ and B denotes a chain non-solvatable by that liquid9
the suffixes m, n, o, p --- denoting differing lengths of
the chains A and ~; C is a monomer gi~ing rise to a
polymer backbone which:in (i) is non-solvatable by the
polymerisable 11quld and in (ii) and (iii) may be either
solvatable or non-solvatable by that Iiquid, and D is a
17 -
` ~)6553~
mono~ar unit bearing a speciflc particle-anchorinq group,
simila~ to the monomer units Y in ~2) above.
In these gra~t copolymers, the solvatable A
chains have a minimum molecular weight o~ 500. The weight
ratio of A chains to chains o C units in (1), or of A
chains to chains of C and D units combined in (ii), is
preferably between 3:1 and 1:3~ more preferably as close
as possible to 1:1. The D ~onomer units in (ii) should
be present in the proportions indicated in (2) above in
respect of the Y unitsO In ~iii), the molecular weight
of the B chains should be greater than 500; if the chains
of C units are solvatable, the weight ratio of (A + C)oB
should be from 3:1 to 1:3, whilst if the chains of C units
are non-solvatable the weight ratio of A:(B + C) should be
from 3:1 to 1:3 and the weight ratio o B:C should also
be within these limits9 preferably about 1:1.
In selecting the polymeric dispersant to be used,
it is important to avoid those amphipa~hic subs~ances,
partlcularly of types (2) and (4) above9 with solvatable
polymer chains containing several groupings capable of
, .
anchoring to the particulate filler which are so disposed
that the substances are in fact flocculants~ not dlspersants.
Polymeric dispersants are identified as those polymers
which, when in their normal coniguration at an interface
between an inorganic particle and the polymerisable liquid,
have a low concentration of anchor groupings towards the
outside of the sheath of polymer adsorbed on the particle7
whereas flocculants characteristically have a substantial or
high concentration of such groups on the outside of the sheath.
- 18 -
1065532
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i9 o U o h :~ ~ 0 ~ 0 11
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~65532
The exact conditions and molecular types which achieve
dispersion rather than flocculation will be recognised by
those skilled in the art.
It is an essential feature of the invention that
the solvated component of the polyme~ic dlspersant, or a
subsequent reaction product thereof obtained on curing
the fluid composltion, should remain solvated by9 or be
compatible with, the oligomeric or polymeric products
which result throughout the course of the curing operation,
so that flocculation or aggregation of the inorganic
particles present is prevented and the dispersant becomes
intimately incorporated or bound up in the matrix pol~mer
of the cured compo~itionD Whilst this requirement does
not necessarily mean that any part of the dispersant
molecule must be chemically the same as, or similar to,
any preformed polymer or ollgomeric constituent of the
polymerisable liquid (A), or even the same as, or similar
to, the solid polymer formed on curing, in practice such
compatibility can be achievad simply by selecting the
dispersant so that it h s a solvated pol~meric component
which in composition is the same as, or closely related to,
the ~inal solid polymerO However~ it may be arranged that
the solvated polymer chains of the dispersant contain
functional groupings through which grafting or
copolymerisation with the monomers present in the
polymerisable liquid (A) may take place durlng the curing
operation. Grafting may be provided for, in the case of
addition polymerisation of vinyl or vinylidene monomers,
- 22 -
~6S53'~
by incorporating in the dispersant molecule~ or example,
copolymerisable methacrylate groups in the manner descrlbed
in British Patent Specification No. 1,052,241, or groups
susceptible to hydrogen abstraction in the presence of
S active radicals obtained by decomposition of a peroxide.
In the case where thermosetting polymers are produced on
curing the polymerisable liquid, various chemically reactiva
groupings such as hydroxyl, amino9 carboxylic acid, epoxy
and methylol can be employed to achieve grafting or
copolymerisation~
The solvated component of the polymeric dispersant
should be of such a molecular wei~ht and/or co~reactability
that, when it becomes incorporated into the polymer matrix
following curing of the composition, it does not have any
deleterious effect on the mechanical properties o* that
polymer. If solvated components of molecular weight near
the lower limit indicated for effective stabilisation are
employed, it is preferred that the compone~t in question
should contain some polymerisable or other reactive
grouping so that it can become chemically, as well as
physically, incorporated into the polymer matrix.
It will accordingly be understood that the
suitability of the solvatable component of a particular
dispersant is dependent upon the choice of polymer matrix.
As already indicated, the particle-anchoring
groupings which are present in the polymeric dispersants may
broadly be of two types. The first type of groupings are
those having some specific affinity for the surface of the
_ 23 -
-
6~S3Z
inorganic ~articles, and these include polar groupings or
chemically reactive yroupings which are complementary to
polar or reactive groupings present on the particle
surface~ These may be defined in more detail as follows:-
S (i) those groupings whereby some form of ionic bondwith the inorganic particle is probably developed, for
example carboxylic or sulphonic acid groups which can form
salt-like bonds with metal ions or base-like centres in
the particles, or amino or quaternary ammonium groups which
can form such bonds wlth acidic centres in the particles;
(ii) thos~ which probably lead to the formation of a
covalent bond with the particles, e.g. isocyanate or
: alkoxysilane groups which can react with hy~roxylic centres
in the particles, or chromic chloride and other chelating
agents which can react with chelatable centres in the
particles;
(iil) those which probably lead to the ~ormation of
hydrogen bonds between the dispersant and the particle?
such as carboxylic acid groups which can interact with
hydroxyl groups in the particle;
(iv) those whereby some physical ad~orption on to the
particle surface takes place; for example through dipole-
dipole interactions or van der Waal forces; such groups
include nitro,~ cyano, ester, amide and betaine groups, the
weak interac~ions of which can be reinforced by attaching
the groups in sequence to a relatively insoluble polymer chain.
: The second type of anchoring groupings are polymeric chains
which, as compared with the solvated polymeric chains
_ 24 -
1~65S~Z
previously discussed, are relatively non-solvated hy the
polymerisable liquid (A) and each segment of which has at
least a small, if non-speciflc~ af~inity for the inorganic
particles~ Examples of such groupings are poly(acrylic
ester) or poly(me~hacrylic) ester chains ~where the
carboxylic ester groups are responsible collectively for
the anchoring ~unction, or polystyrene chains wh~re the
aromatic rings perform that function.
Th re may be used, if desired, anchoring groupings
of both the specific and the non-specific types mentioned
above.
By way of further illustration, some polymeric
dispersants which are suitable for use in specific situations
will be described in more detail.
lS Examples of dispersants which are particularly
suitable for use with addition polymers derived from one or
more unsaturated monomers, or syrups of high molecular weight
polymers dissolved in such monomers, are polymers of
similar molecular type to the matrix polymer, having a
molecular weight in the range 20,000 - 200,000, and having
a number of groups distributed along the polymer chain
which are substantive to the inorganic particle. Thus~
for a syrup of a 90~10 W/w copolymer of methyl methacrylate
and butyl acrylate in methyl methacrylate, a suitable
dispersant is a g5/5 W/w copolymer of methyl methacrylate and
methacrylic acid, or a metal salt of that acid~ Other
co-monomers which are polar and substantive to inorganic
materials are also useful9 sOg. dimethy}aminoethyl
methacrylate and quaternary ions or acid salts thereof,
_ 25
65532
methacrylamide, y-methacryloxypropyl trimethoxy silane~
adducts of glycidyl methacrylate with polar-substituted
aromatic acids such as p-aminobenzolc acid~ and adducts of
glycidyl methacrylate with y-am{nopropyl trimethoxysilane.
Another form o~ dispersant which ~s useful is a
copolymer consisting o~ solvated polymer chains which are
attached at random intervals along a relatively insoluble
polymer chain, the latter chain also having randomly
attached thereto groups capable of effecting anchoring to
the particles of inorganic filler. Such polymeric
dispersants can be made, for ~xample, by the methods described
in British Patent Specifications Nos. 1~052,241 and
1,122,3~7.
Examples of dispersants which are particularly
lS suitable for use with polymer matrices obtained by
polymerisation, chain-extension and cross-linking of
unsaturated oligomers and their solutions in unsaturated
monomers ? are oligomers of a similar molecular weight which
contain one or more similar unsaturated groups and one or
more pendant polar groupsO Thus a suitable dispersant for
use in a solution in styrene of an epoxy resin which has
been doubly terminally reacted with methacrylic acid to yield
a divinyl-unsaturated polymer tsuch materials are sold under
the trade name "Derakane"), is an oligomer which has been
reacted at only one end with methacrylic acid to give a
terminally unsaturated species and at the other end with
p-aminobenzoic acid or with y-aminopropyl trlmethoxysilane
to give a terminal grouping capable of adsorbing on to an
inorganic particle surface~ e.gO of silica.
- 26 -
1~553Z
Dispersants indicated as particularly suitable
for one type o~ polymerisa~le liquid are not necessarily
restricted to use with that type and are only illustrative
of what is possible. Thus the above terminally unsaturated
s dispersant could be equally useful in a simple methyl
methacrylate ~onomer-based compositlon.
A suitable dispersant for use in a polyurethane
derived from a polyol and a polyisocyanate is obtained by
grafting some of the polyol portion of the polymerisable
liquid on to an acr~lic polymer backbone which contains polar
substituentsr A ~uitable dispersant for use in an epoxy
resin system can be obtained by reacting p-nitrobenzoic acid
with some o~ the epoxy groups of the epoxy resinO For a
system incorporating a vinylidene-terminated urethane, a
dispersant can be made by reacting some of the urethane9
through free NC0 groups present therein, with ~-aminopropyl
trLmethoxysilane.
Although in the majority of cases the polymeric
dispersant (C) wilI be a separately produced and incorporated
constituent of the curable compositions of the invention, it
is not essential that it be so, that is to say it is possible
for some constituent of the polymerisable liquid (A) itself
to perform the function of polymeric dispersant~ Thus the
terminal carboxylic acid groups of an unsaturated poly-ester
chain can become adsorbed on to the inorganic particle
surface. Monocarboxylic acid-terminated chains will act as
a dispersant, but dicarboxylic acid chains may act as
flocculants and it i~ preferred that these be avoided in
- 27 ;
6S532
order to make a non~-Elocculated dispersion~ Polyesters
which are essentially devoid of such dicarboxylic acid
chains but contain s~gniicant amounts of monocarboxylic
acid chains can be made by using excess diol to make a low
acid value polyester and then further reducing the acid
content by reaction with a monoepoxide, as outlined or
example in ~ritish Patent Specifications Nos. 1,045,199 and
1,317,605. Equally, it is possible for t'he dispersant to
be formed in situ during the process of dispersing the
filler in the polymerisable liquid, for example in
consequence of there already being present a low molecuLar
weight substance, containing a potential filleranchoring
group, which can combine with a solvated polymer chain.
For example, epoxide-containiny solvatable polymer chains
can combine with the carboxyl group of a nitrobenzoic acid
during the dispersion step.
The proportion of polymeric dispersant (C) used
in the compositions of the ln~ention is sub~ect to wide
variation depending on the nature of the associating groupings
in the dispersant, the particulate inorganic material
selected, the part~cle surface area and concentration, and
the nature of the polymerisable liquid~ but in general a
satisfactory minimum proportion is O.Olg/m2 of the total
particle surface area, as determined by the ~.E.T. nitrogen
absorption method. An adequate minimum proportion of
polymeric dispersant is essential, in order to ensure that
the inorganic particles are free from aggregation ~n the
curable composition and remain so during the curing of the
compositionO In general~ higher concentrations of polymeric
- 2~ _
1~6S53Z
dispersant are required when the inorganic particle
concentration and total surface area are high, and also
when the polymerisable liquid contains a soluble, preformed
oligomer or polymer. Above a certain optimum level there
is no further advantage to be gained in terms of particle
stability by increasing the proportion of polymeric
dispersant.
Where the curable compositions of the invention
incorporate two or more types of finely divided particulate
material, or where there is present~ in addition to the
particulate inorganic filler~ a pigment as referred to
below, it may be advantageous to employ two or more different
polymeric dispersants. In these dispersants, the
"anchoring" components may be differently selected according
to the surface characteristics of the particles in question.
The solvatable components of the dispsrsants may be either
the same or different~ but if different they must nevertheless
be compatible with one another and with the other components
of the curable compositionl as previously discussed.
Although it is not essential in order to obtain
certain of the benefits of the invention, it is a preferred
feature of the curable compositions of the invention that,
~
_ ~9 _ ,
~06S53~
in addition to comprising the polymerisable organic liquid
~A~, the particulate ~norganic ~iller tB) and the
polymeric di~persant (C) already described9 they should
contain a substance providing active groupings whereby it
S may be ensured that the polymer matrix and the particles
are very strongly bonded together in the Final composite
material obtained after curing. Some degree of bonding
between the matrix and the particles is always present simply
by virtue of the presence of the polymeric dispersant, the
characteristics of which result in its becoming located at
the interface between these two phases and exh~biting an
af~inity for them both. However, in order to obtain composite
materials of optimum mechanical properties, it is necessary
that the strength of the bond between the polymer matrix
and the particles should be at least as great as the
internal cohesive strength of whichever of these two
con~tituents is the weaker.
In suitable cases, the required strong bond can be
produced through the use of an appropriately selected polymeric
dispersant, whereby the forces which associate the dispersant
with the particles are sufficiently strong and the solvated
component of the dispersant becomes fully integrated into
the polymer matrix after curing either through chemical
interaction or by virtue of its being a compatible polymer
of comparable molecular weight.
Preferably9 however, the production of a very
strong bond between the polymer matrix and the particles is
achieved or assisted by the inclusion in the curable
- 30 -
1(~65532
composition of a low molecular weight bonding agent ofthe type which contains one or more groups capable o~ inter-
acting with groups in the inorganlc material, and also one
or more groups which can copolymerise with, or otherwise
graft on to, the polymer forming the matrix in the finished
composite material. In using a low molecular weight bonding
agent o~ this type, care must be taken that the bonding agent
is, like the polymeric dispersant, present at the interface
between the two species to be bonded; this requires that
the proportions o~ dispersant and bonding agent used should
be controlled so that neither individually achieves saturated
coverage o~ the particle surface, thus leaving no space for
the other agent to become adsorbed.
The particular type of bonding agent to be used
will depend upon the nature of the inorganlc f~ller and of
the polymerisable organic liquid~ Suitable bondl~g
agents are in general substances containing groups which can
form a multiplicity of ionic, covalent or hydrogen bonds with
the particle, and also groups which can react to ~orm bonds
with the polymer matrix. Suitable groups for bonding to
particles having hydroxylic, metal oxide or silicaceous
sur~acés are, for example, the oligomeric hydrolysis products
of alkoxy silanes, chlorosilanes and alkyl titanates as
well as the trivalent chromium complexes of organic acids.
Where the particle surface is of a basic character, as for
example in the case of particles of alkaline earth metal
carbonates or of metals such as aluminium9 chromium and steel~
suitable bonding groups are carboxylic acid groups. In the
~ 31 -
~(~6~532
case of particles with acidic surfaces, such as those of
kaolin, amine salt groups are suitable for bonding to the
particles.
Groups suitable ~or bringing about bondlng with the
polymer matrix are typically those which co-react wlth the
polymerisable liquid during the polymerisation stage~ Thus
an interfacial bonding agent containing an ethylenically
unsaturated group is suitable for use with addition
polymerisation systems invol~ing vinyl, vinylidene and
similar unsaturated monomers. An agent containing an amino,
an oxirane or a carboxyl group is suitable for use with
epoxy-group-containing compounds. Examples of suitable
inter~acial bonding agents include:-
y-methacryloxypropyl trimethoxy silane
y-aminopropyl trimethoxysilane
y-glycidyloxypropyl trimethoxysilane
vlnyl triethoxysilane
vinyl triacetoxysilane
vinyl trichlorosilane
Acrylic and methacrylic acids and their metal
salts
Methacrylatochromic chloride
Maleimidopropionic acid
Succinimidopropionic acid
4-Aminomethylpiperidine
Tetraisopropyl and tetrabutyl titanates
_ 32 -
``" iOS5~ii32
The amounts of the interfacial bondin~ a~ent used are, in
- gelleral, those conventional in the art o polymeric mat~rials
rein~orced with inorganlc fillers. A su~table minimum
usage fDr most applicatlons is about O.OOlg of bonding
agent per square metre of filler particle sur*ace area.
I desired, a mixture of two or more interfacial bondlng
agents o~ the types described may be used.
The curable compositions of the invention may
incorporate dyestu~fs or pigments. These constituents may
be dissolved or dispersed in the complete mixture of the
- polymerisable liquid, 9 the finely divided inorganic filler
and the polymeric dispersant, or, in the case of pigments~
they may be added to that mixture as a preformed dispersion
in the polymerisable liquid which has been prepared with
the aid of a suitable pigment dispersant. for example a
dispersant of the type described in British Patent No.
1,108,26i or our Canadian Patent No. lQ2~035_~
There may also be incorporated in the curable
compositions coarse granular "iller" particles or coarse
fibrous material which are dispersed, but not stably
dispersed, in the other constltuentsO By "coarse" is here
meant that the average diame~er of the granules or the fibre
strands is at least ten times greater than the average
diameter of the fînely divided inorganic flller particles
~as hereinbefore defined. Under these circumstances~ the
stable dispersion of finely di~ded particles beha~es
essentially as a fluid towards the coarse particles, that is
to say the resistance to motion of the coarse particles
_ 33 - -
~ ' .
3Z
through the dispersion is the same as it would be throu~h
a pure liquid of equivalen-t ~iscosity and density. In the
composite materials obtained by subsequent curing, the
polymer produced9 together with the finely divided particles,
constitutes essentially a binder of high mechanical quality
for the coarse particulate material Becau~e there is no
interation between the coarse and the finely divided
particles, there is no need to modify the proportion of the
latter particles to the polymerisable organic liquid from
that which would apply in the absence of the coarse matexial.
According to another a~pect of the present
invention there is provided a method for producing stable,
fluid, mouldable and curable compositions as hereinbefore
defined which comprises dispersing, in an organic liquid (A)
which is polymerisable to orm a solid polymer and which
has a viscosity not greater than 50 poise at the temperature
at which the co~position ls to be moulded, finely divided
particles (B) as hereinbefore defined of an inorganlc filler,
in the presence of a polymeric dispersant (C) as hereinbefore
defined, so that the filler particles constltute not less
than 20X by volume of the total composition.
The polymerisable organic liquids, the inorganic
fillers and the polymeric dispersants suitable or use in
this me~hod are those discussed above. It will be
understood that the polymerisable liquid may optionally
contain some preformed polymer, which may be either identical
with or different from the polymer which is formed by the
curing of the polymerisable liquid $tself. It will also be
- 34 -
6~53~
understood that there may be present, in addition to the
polymeric dispersant, an int~r~acial bond~ng ag~nt as
described above. The process of dispersing the particles
of the inorganic filler in the polymerisable liquid may be
carrLed out by any of the techniques commonly used in the
pa~nt industry for making dispersions of pigments in liquid
vehicles~ if desired at a temperature above room temperature.
Thus, where the ~iller is already available in the required
primary particle size9 the process may conveniently be one
of dispersing the particlas in the polymerisable liquid,
using techniques such as bead milling? pug milling or other
methods whereby the dispersion is sheared and the particle
aggregates thereby loosed and wetted out by the liquid.
Alternatively, the finely divided particles may be produced
directly ln the presence of`the polymeri~able liquid, or in
a liquid component thereof, and also in the presence of the
polymeric dispersant, by comm~nution (~racturing) of coarse,
non-colloidal particles. By such a technique9 readily
available raw materials, such as the coarse sands used in
glass manufacture~ can be utilised~ the dlfficulties and
hazards of handling fine powders (e.g. risks of explosion
or of diseases such as silico5is) are avoided, and the degree
of drying which is required following the normal process
of manufacture in an aqueous medium is reducedO In additlon~
we have surprisingly found that the composite materials
obtained by curing fluid compositions made by this particular
method, where a low mol~cular welght bonding agent of the
type previously discussed is also present during the
_ 35 -
53Z
co~mînution operation, have superior properties to thosemade from fluid compositions incorporating the same inorganic
~iller particles made ~y pre-grinding in aqueous media and
then drying normally at lOO~C. It is beli.eved that these
advantages are attributable to (1) the relaLtively low initial
amounts of chemisorbed water which are introduced by using
coarse inorganic particles, (2) the reducecl likelihood of
contamination of freshly created particle surfaces by water
or other small molecules and the enhanced opportunity ~or
strong adsorption by those surfaces of the polymeric
dispersant and, i~ present, the interfacial bonding agent.
I~ desire~, however~ comminution of the inorganic flller
material may be carried out in some suitable non-aqueous
liquid other than the polymerisable liquid, after which the
liquid is removed by drying and the particles are then
re-dispersed in the polymerisable liquid.
Comminution of coarse material 5 in the size range
of one hundred to a few thousand mlcrons, to yield smaller-
size particles; is readily carried out by using conventional
ball mills, stirred ball mills (attritors) or vibratory mills
with preferably spherical or cylindrical grinding media which
are harder and denser than the filler material, employing
ratios of grinding media size to average initial particle
size of a~out 10~1, or up to 100:1 where the polymerlsable
liquid is highly viscous. Multi-stage processing with
different sized media, or the use of mixed media sizes and
shapes, may be required to achieve very fine particle sizes
or special particle size distributions.
_ 36 -
1~6553~
Where the curable compositions are to lncorporate
an interfacial bonding agent, this may be lntroduced either
during or after the process of re-dispers~on o the
inorganic particles in the polymerisable lLquid, or their
production by commin~tionl as the case may be. The bonding
agent may simply be blended into the dispersion, but it is
preferred to ensure in some way that the agent becomes
associated with the inorganic particles~ For example, where
the bonding agent is a silane derivatlve as previously
mentioned, it will be advantageous to arrang~ that sufficient
water is present in, or is added to, the system to bring about
complete hydrolysis of the silane derivative; this may be
assisted by heating and the addition of a suitable catalyst,
such as a n-alkylamine or a dlalkyltin dicarboxylate.
Curable compositions according to the invention
exhibit excellent stability on storage; any settlement is
easily redispersed. In cases where it is desired to prevent
settlement, this can be achieved by the addition of bentonite
clays ? fumed silicas, hydrogenated castor oil or other
materlals as is well-known in the palnt and colloid arts.
According to a further aspect of the present
invention, there is provided a process for the production of
a multi-component composite material comprising an organic
polymer matrix and a particulate inorganic reinforcing phase
dispersed therein and bonded theretoq the process comprising
subjecting to curing a curable fluid composition as
hereinbefore defined so as to convert the polymerisable organic
liquid component thçreof into solid polymer~
_ 37 -
" ~lO~;S532
This aspect of the invention includes the
production of composite materials by curing mixtures of two
or more ~luid compositions as hereinbefore ~efined.
It is a special feature of the invention, as already
mentioned, that the curable compositions contain high volume
loadings of the finely divided particulate inorganic iller
and yet retain a very low viscosity. For example, in
compositions containing 50 and 55 volume per cent of finely
divided granular particles, relative viscosities of only 10
times and 100 times that of the polymPrisable liquid viscosity
respectively are attainable. Such relative viscosities
approximate closely to the minimum attainable for non-
aggregated mono-dLspersed spheres (cf. J.S~ Chong, E.B.
Christiansen and A.D. ~aer, J. Applied Polym. Sci., Vol. 15,
2007 - 20?1 (1971)).
Thus, for a monomer such as methyl methacrylate
~with a viscosity of 0.5 centLpoise, filled dispersion
viscosities of 5 centipoise for 50% by volume and 50 centipoise
~for 55X by volume are attained. In the case of a resin/
monomer system with a viscosity of 5 poise, filled dispersion
viscosities of only 50 and 500 poise, for 50% and 55% by
volume respectively, are possible.
A further feature of the invention is the fact
that the viscosity of the compositions is low even at very
low shear rates, i.e. the compositions are Newtonian or
near-Newtonian Ln character at low shear rates and do not
have aggregated or flocculated filler-induced thixotropy (the
compositions may, however~ be somewhat thixotropic where an
_ 38 -
``" ~L06S53Z
anti-settling agent such as bentonlte has been included~ as
referred to above, or where the polymerisable liquid itself
has a thixotropic character). Also because of the fine
par~icle si~e, there is little tendency to settlement in the
S low viscosity media during the moulding anci curing process,
and no tendency to dilational cavitation when the
compositions are sheared such as commonly leads to voiding
with coarse slurries.
For most of the available techniques of fabricating
the curable compositions 9 it is preferred that the
composition should have a viscosity not greater than 1000
poise under the temperature and shear condltions under which
the composition is to be moulded. However, for certain
applications, viscosities higher than this limit may be
acceptable. On the other hand, where low pressure moulding
procedures are to be used, it may be desirable for the
viscosity of the composition not to exceed 100 poise. In
general, the adjustment of the various parameters such as
the viscosity of the polymerisable liquid, the filler loading,
the size distribution of the filler particles and the
efficiency and amount used of the polymeric dispersant, in
such a way as to obtain a curable composition of acceptable
viscosity for any given fabrication technique, will readily
~ be achieved by those skilled in the art.
These features render possible the fabrication
of articles from the curable compositions by procedures
.
- 39 -
~L~6S~3Z
which cannot be employed wi~h previously known, ine
particle-filled compositions, because of their high and
often non-ideal viscosity.
The pre~ence of the high proport,Lon of inorganic
material furthermore acilitates the castillg of large
objects directly from the curable fluid cornpositions at
pressures at or only slightly above atmospheric; the heat
of polymerisation generated by the polymerisable li~uid during
curing is absorbed and dissipated by the ~iller material.
This factor substantially reduces the chance of void
formation through boiling of monomer, and in cases where
sufficient inorganic filler is present the chance of void
formation can be completely eliminated, since the
temperature rise during polymerisation will not exceed the
monomer boiling temperature even if there is no heat loss
to the mouldj a condition which occurs in practice with
thick section mouldinys~ However, in those cases where
the '~heat sink" capacity of the composition is not
sufficient to prevent boiling9 eOg. when a fast polymerisation
is initiated at a temperature c}ose to the monomer boiling
point, void formation can be prevented by bringing about
early gelation of the composition through the introduction
of a cross-llnking reaction into the curing process. In
the case of a composition based on addition polymers, this
may be achieved by the presence of polyfunctional species
comprising part of the polymerlsable li~uid, such as ethylene
glycol dimethacrylate where the polymerisable liquid is mainly
based on methyl m~thacrylate. ~lternatively~ a separate
_ ~0 --
.
~6S~3Z
gelation rea~tion may be introduced, such as the reaction of a
polyisocyanate with oligomers containing a plurality of
hydroxyl groups present ln the polymerisable liquid, after
which the cure is completed by a free radica~-initiated
S addition polymerisation.
Curing of the compositions of the invention can,
if desired, be carried out using closed moulds at greater
than atmospheric pressure, and fast cures in the absence of
any cross-linking reaction are then possible without boiling
of monomer, but this involves expensive equipment and is
not convenient with very large mouldings.
A number of methods can be used for fabricating
articles from the curable compositions of the invention.
They can be moulded simply by casting the mixture into
moulds and initiating the polymerisation. Sheets, rods,
beams and other convenient shapes can thus readily be
obtalned. Initiation may be induced by heat-activated
cata1ysts, or ~y addition of catalysts immedlately prior to
moulding where curinq at room temperature or lower
temperatures is required. A preerred modification of the
simple casting technique is to inject the curable, fluid
composition under low pressure into closed, matched moulds;
pressures of less than 10 p.s~i., are required for this
process and hence cheap, ligh~-weight moulds can be used and
mouldings of very large surface area are practical, whereas
- much higher pressures are normally required for conventional
filled compositiQns. A further variant of this technique
is to fill the mould with fibre strands before in~ecting
_ 41 -
~6S53~
the dispersion into the mould so that it permeates through
the fibre strand mesh ("resin~ection"); again only low
pressures are required and large surface-area mouldin~s
are feasible. Whilst the in~ection of reactive resins
into closed moulds filled with ~ibre strands is known,
together with the associated advantages, e.g. the avoidance
of the difficulties o~ moulding fibre/resin dispersions,
better reproducibility than is possible with hand layup and
the production o~ two good faces with the potentiality of
moulding in bosses and ribs, it has not heretofore been
practical as a process for highly filled compositions.
The filled compositions known prior to this invention have
either been of too high a viscosity or have contained coarse
or aggregated particles which are filtered out by the fibre
mesh; both of these effects create a high back pressure
which prevents the mould from being filled. Many of the
compositions o the present in~ention are~ however, very low
in viscoslty and they also contain finely divlded non-
aggregated particles; thQy are, therefore, able to pa~
through and wet out the fibre mesh.
~ h~ fibr~ for use in this process can be ei~her
organ~c textile or inorganic (e.g. glass or metal)~ or a
mixture of these. They are most conveniently intmduc~d
into the mould in mat form, although loose chopped strands
and sprayed-up preforms, bound with a small amount of resin,
can also be used. In genera} the fibre mesh should contain
a ma]or proportion of pores which are 5 times greater,
preferably lO times greater, in diameter than the average
_ 42 -
" ~65532
filler particle si~e. This condition is most readily
attained for fibre volumes up to 40% by using fibre meshes
made up of fibre strands of thicknesses which are at least
5 times~ preferably at least 10 times, the iller particle
size. Suitable fibre meshes oE this type are commercially
a~ailable; in the case of glass fibres, these are
obtainable as multi-fibrillar strands containing from 20 to
1000 of 10 micron fibrils per strand. Meshes made up of
fibres which have a diameter the same as, or less than,
that of the particles can also be usedj but only at lower
fibre volumes.
Composite materials which contain fibres can also
be made by conventional techniques such as hand layup and
press-moulding of mixtures of the curable compositions and
chopped fibre mixtures. Here again the low viscosity can
be an advantage, leading to low mouldin~ pressures and ease
of wetting and de-aeration.
Composite sandwich mouldings can be made with
advantage by the injection technique. Thus~ one can
2Q totally encapsulate a core material which can be, for
example, a low density foam, the combination of which with
a skin of the high modulus, high strength composites of this
in~ention produces light-weight, very stiff and strong
structures~ The core is placed in the mould which is then
closed and the curable, fluid composition is injected around
it. Fibre mats may also ~e placed in the mould along with
the core; these serve to locate the core in the mould and
subsequently to toughen the skins of the finished moulding.
_ 43 -
:,
S~32
These techniques are generally described in our co-pending
Application No. 10551/72~
Core encapsulation can also be carried out by
spreading the fluid composition on either side o~ the core
before placing it in a mould and then closlng the mould so
that excess liquid is squeezed out. Fibre mats can also
be placed on either side before placing in the mould.
Another type of sandwich moulding is that in which
the compositions of this invention are bonded during the
10 curing operation to one side of a preshaped sheet or shell
moulding. Por example, a shell moulding is vacuum
thermoformed from a plastic sheet9 a matched mould is placed
behind it so as to form a sealed cavity, the curable
composition is in~ected into the cavity and then cured; in
this way a composite article ls obtained in which the cured
composites material of this invention is bonded to one side
of the plastic. By this means a thin plastic moulding
can be rigidised and reinforced, whilst combining the
simplicity of vacuum-forming of thermoplastics with the
20 convenience and ease OlC the low pressure in~ction of the
compositions of this invention ~
The curable compositions of the invention can
also be rotationally rnoulded to obtain complex hollow shapes
and pipes; the fluid composition is placed in a mould and
25 the mould is rotated on on or more axes t depending on the
complexity of the article9 whilst curing is effected.
Again, because of the absence of any boiling of monomer9
the ease of de-aeration and good flow characteristics of the
~ 4~ _
~06~53;2
fluid composition, flaw-~ree mouldin~s o~ large size can
readily be made. Optionally fibres can also be introduced
into the mould.
The cured mouldings ~s described above can, if
desired, be further ~abricated by machining and bonding.
We have also surprisingly found that the cured composite
materials of this invention can be thermoformed and are
capable of large extensions without fracture at a temperature
above the glass transition of the matrix polymer, where it
i~ amorphous, or above its melting point where it is
crystalline. Heated sheets can thus be ~ormed into shapes
by application of positive or negative pressure to the
sheet to draw it into a mould. Conventional composite
materials which contain coarse, poorly bonded, or aggregated
particulate fillers usually whiten and fracture at low
deformations and cannot normally be thermoformed in this way.
In all the above fabrication processes it is
advantageous to use internal or external release agents, to
~ prevent adhesion of the cured composite materials to the
mould and to obtain a good surface finish. The techniques
are well-known in the art. Examples of internal release
aids include alkali or alkaline earth metal salts of fatty
acids and alkyl phosphates and their neutralised derivatives.
Suitable external release agents include poly(tetrafluoroethy-
lene)~ silicone and polyvinyl alcohol coatings on the moulds~
Multi-component composite materials made according
to the preerred embodiment of the invention, in which the
polymer matrix and the inorganic particles are strongly
_ ~5 -
- " ~L065S3Z
bonded together, exhibit an unexpected and valuable
combination o~ mechanical and physical properties, inasmuch
as (contrary to accepted practice) not only the stif~ness
but also the strength continue to increase as the
concentration o~ inorganic particulate phase is raised,
ri~ht up to the maximum levels hereinbefore indicated. The
impact strength of the matrix polymer is ~lso largely retain~d
and in certain cases enhanced. The curecl composite
materials have ~ery good abrasion resist~ce if particles
of a high Moh hardness, such as quartz and alumina, are
used. They are also substantially more fire-resistant than
unfilled polymers9 and even when they burn their
contribution to the total fire load is small and the flame
si~e and rate of propagation is low. Compositions with
an especially high resistance to fire may be obtained by
using finely divided fillers which wholly or in part
contain hydrated water which is released on heating, e.g;
aluminium oxide trihydrate and calcium sulphate hemihydrate.
Products in which the composite materials
incorporate coarse fibresy as hereinbefore described, are
rendered significantly tougher. The use of a coarse,
granular constituent makes it possible to produce a composite
product having an inorganic content in excess of 95% W/w
which~ whilst being lower in strength than the unmodified
matrix polymer, is significantly stronger and more abrasion-
resistant than a conventional hydr~ulic cement.
As is eviden~ from the range of mechanical
properties and the potential fabrication processes h~reinabove
_ 46 -
1~655;32
describedt the composite materials o~ the invention are
suitable ~or a very wide ran~e of uses.
Articles which take advantage of the good surface
finish, abrasion resistance7 ease of pigme!ntation and fire
resistance obtainable include work surfaces, decorative wall
tlles, cabinet furniture, occasional tables and sanitary
ware. Articles which utilise the high st:iffness and
strength of the composites and the ease o fabricating
large, thin shell mouldings by the "resin~ection" process
are, for example, vehicle bodies, baths, boats and chair
shells. Articles which can be made by rotational moulding
include pipes, silos, vehicle bodies, toys and storage
tanks.
The invention is illustrated but not limited by
the following Examples, in which parts and percentages are by
weight unless otherwise stated~ The curable compositions
are, except where otherwise stated9 cast as approximately 5 mm-
thick sheets; the flexural modulus and strength of the
products are determined at 25 C by three-point bending, the
beam length being lOo 16 cm and the rate of bend 5mm/min. The
impact strengths are all determined at 25 C using the Charpy
Impact Testing Hachine as described in B.S. 2782: Part 3,
Method 306D (1970). The abrasion resistance is determined by
means of a Taber Abrader (Taber Instrument Corp.), using CS10
discs and a lOOOg load for 1000 cycles in each test. The
sample is weighed before and after the test and the weight loss
per 1000 cycIes is recorded. The particle size distributions
are determined by well-known Coulter counter techniques.
_ 47 -
.
106~532
hxample 1
This example illustrates the production of a ~luid,
curable composition from methyl methacrylate and quartz
silica, using as polymeric dispersant an acrylic copolymer
in which quaternary ammonium groupings effect anchoring to
the sur~ace of the particles.
A finely divided dry-group and air-classified
quartz silica tMinusil.5, ex Pensylvania Glass Sand Corpora-
tion) with a surface area as determined by nitrogen adsorp-
tion of 5.0m2/y and a particle size distribution as follows:
Particles of 10 microns or less 99.999% by number
. (97.5% by weight)
Particles of 50 microns or.less - (100.00~ by weight)
is dispersed in methyl methacrylate (containing 100 p.p.m.
of Topanol A* inhibitor) in the presenc~ of 1.7% by weight
based on the silica o a copolymer dispersant (methy~ metha-
crylate 81.4 parts, ethyl acrylate 9.6 parts, dimethyl amino- .
ethyl methacrylate 4.8 parts, quarternised with benzyl
chloride 4.2 parts) having Mw as determined by gel permeation
chromatography (G.P.C.) 20,000, and in the presence also of
1..8% by weight based on the silica o ~-methacryloxypropyl
trimethoxysilane, to give a very fluid~ non-flocculated
~dispersion (Ford No. 4 cup viscosity at 20C less than 15
secs.). The dispersion contains 67% by weight of silica.
100 parts by weight of this dispersion.is heated
to 100C and then cooled to room temperature, 0.6 part by
weight of Perkadox Y16** is added (2~ by weight on the
monomer~. The initiated dispersion is cast in a flat plate
mould lined with Melinex*** ilm and heated for 2 hours at
50C and 2 hours at 80C. The finished casting is very glossy
- 48 -
C " 1~55~ '
and ~lawless, contains 50% by volume o~ silica and has a
flexural modulus of 12.6 GN m , ~lexural strength 110 MN m
and Charpy unnotched impact strength of 6.0 K~ m
* "~opanol" A is a Registered Trade Mark o Imperial
Chemical Industries Limited for 2,4-dimethyl-6-tert-butyl
phenol~
** "Perkadox" Y15 is a Registered Tr.ade Mark o~ AKZ0-
Novadel for bist4-tert-butylcyclohexyl) peroxydicarbonate.
*** "Melinex" is a Registered Trade Mark of
Imperial Chemical Industries Limited for an biaxially orien-
tated poly(ethylene terephthalate) sheet.
: Exa~ple 2
Example 1 is repeated but with an increased level
of silica. Thus by using the same ingredients as before
but less methyl methacrylate a 69% by weight aispersion is
m~de which has a Ford ~o. 4 cup viscosity at 20C o~ 19 secs.
It is cured as described in Example 1 and gives a flaw-free,
glossy sheet, with a silica volume of 52.5%, a ~lexural modulus
of 12.4 GN m 2 and a flexural strength of 110 MN m 2
Example 3
: Example 2 is repeated but omitting the ~ilane deriva-
ti~e. A fluid dlspersi~n is obtained having a Ford No. 4 cup
viscosity at 20C of 16 secs. When cured as ~escribed in
~ Example 1 a flaw-free glossy sheet with a silica volume of- -
: 52.5% is obtained which is somewhat weaker and more brittle
than that obtained in Example 2.
: Example 4
In this ExamPle, the polymeric dispersant of
Exampl~s 1-3 is replaced by a different acrylic copolymer in
which caxboxylic acid groups are present to eect anchoring
49 -
!
-
~0~;553~
to the silica par-ticles.
Example 1 is repeated except that the dispersant
used in that Example is replaced by 3.4 parts by weight based
on the silica of a copolymer dispersant (methyl methacrylate
98 parts methacrylic acid 2 parts), having Mw (G.P.C.) 110,000.
A 1uid dispersion is obtained. The finished castin~ is
glossy and flaw-ree and has a flexural modulus of 10.4 GN m
a flexural strength of 127 MN m 2 and a Charpy impact strength
o 6.5 KJ m 2
Comparative Examples A-F
To illustrate the importance of having present a
polymeric dispersant, the attempted preparation is shown of a
number of compositions using the same quartz sillca in the
same concentration as before, but either omitting the poly-
meric dispersant altogether or replacing it by a conventional
dispersing agent.
Comparative Example A
The quartz silica as described in Example 1, ~67
parts by weight) is sheared into 33% by weight of methyl
methacrylate. A powdery cake is obtained having no
~l~idity at all.
Comparative Example B
The quart~ sili~a as described in Example 1, (67%
by weight) is sheared into a mixture of 31.2% by weight of
methyl methacrylate and 1.14% by weight of ~-methacryloxy-
propyl trimethoxysilane. ((1.7% by weight on silica). A
~ery thick, 10cculated mixture is obtained, which cannot
be cast~ It is pressed into a mould and cured as described
in Example 1 to give a cracked and flawed sheet.
- 50 -
~065532
Comparative Example C
The quartz silica as described in Example 1 (67% by
weight) is sheared into a mixture of 30 parts of methyl meth-
acrylate7 1.14~ by weight of ~-methacryloxypropyl trimethoxy-
silane and 1.2% by weight o~ sodium stearate. A thick ~loccu-
lated mixture is produced which cannot be cast and which when
pressed into a mould and cured as in Example 1 produceS a
cracked and flawed casting.
5~1~ .
Comparative Example C is repeated, replacing the
sodium stearate with a nonyl phenol/ethyleneoxide condensate.
A flocculated mix and a cracked and flawed casting
result.
Comparative Example E
Comparative Example C is repea ed, replacing the
sodium stearate with cetyl pyridinium bromide-.
A flocculated mix and a cracked and ~lawed casting
result.
Comparative Example F
20~ ~ To illustrate the improved mechanical properties of
the filled compositions described in Examples 1-4, as compared
with the properties of the matrix polymer, the methyl methacryl-
ate~used in Example 1 is polymerised under the same conditions
as are described in that Example. The polymer obtained has a
Iexural modulus of 3.0 GN.m 2, a flexural strength of 100 ~N m 2
and an impact streng~h of 6-8 KJ m 2.
~} .
: In.this series of Exa~ples dispersion of finely
divided ~-quartz sili~a are made by comminution (fracturing~
of coarse silica glass sand in the monomer.
- 51 -
365S3'~
Example 5
312 Grams of coarse glass-making quartz sand ~Harrison
Meyer 44431), 80-86~ b~ weight of which has a particle size
lying between 150 and 420 microns, 133 g of methyl methacrylate,
0.45 g ~0.15% by weight on silica) of y-methylacryloxypropyl
trimethoxysilane and 2~8 ~ of copolymer dispersant (98:2 methyl
methacrylate/methacrylic acid copolymer ~ ~w llo,aoo ~G.P.C.))
are charged together wi~h 1,050 g of 3/8" steatite balls to a
two gallon ballmill. The ratio of the charge to voids between
the balls is 1~1. The mill is rotated at 60 rpm for 24 hours.
: After separating the balls/ a dispersion consisting of 73~ by
weight of finely divided quartz silica in the.monomer is obtained
which has a Ford No. 4 cup viscosity of 58 secs. at 20C and a
viscosity of 0.4 poise at a shear rate of 20 secs. 1 and 25C.
The particle size distribution of the quartz so obtained is as
~ollows:
Particles of 10 microns or less 99.7% by number (55.0% by
weigh~)
Particles o~ 50 microns or less - (100.0~ by weight)
The surace area of the sand after comminution is a~out 2 m2/g;
the surface area before comminution is less than O.lQ m ~g.
~o 173.7 g of the above dispersions is addea 15.3 g
: of~methyl methacrylate and l.lB g of Perkadox yl6 initiator
:; (2~ by weight on total monomer). The disperison is then cast
~nd cured as described in Example 1. A glossy, flaw-free sheet
containing 6~ by weight (50% by volume~ of silica is o~tainea;
its mechanical properties are given in Table 1.
~xample 6
The comminution process described in Example 5 is
repeated but omi~tin~ the silane deriv~tive. A fluid di~,persion
of 73% by weight of colloidally fine silica in m~thyl methacryl
ate, having a similar viscosity and particle size rang~ to the
! - S2 -
10~;5~i3~
dispersion of Example 5 is obtained. To 173.3 g of this dis-
persion is added 15.3 g of methyl methacrylate and 1.18 g of
Perkadox Y16 initiator. The dispersion is then cast and cured
as described in Example 1. A glossy, flaw-free sheet contain-
ing 67% by weight t50~ by volume) of silica is obtained, the
mechanical properties of which are shown in Ta~le I.
Comparative Example G
The comminution process described in Example 6 is
repeated but omitting the copolymer stabiliser. A flocculated
mixture which cannot be separated from the steatite grinding
media is obtained.
Example 7
To 173.7 g of the dispersion prepared as described in
Example 6 is added 15.3 g of methyl methacrylate, 1.18 g of
Perkadox Yl~ initiatox, and 0.19 g of ~-methacryloxypropyl tri-
methoxysilane (0.15% dry weight on the silica). The dispersion
is allowed to stand for 24 hours, then cast and cured as de-
scribed in Example 1 to produce a glossy, flaw-free sheet con-
taining 50% by volume of silica and having mechanical proper
ties as reported in Table I~
Exam~le 8
Example 7 is repeated except that the dispersion is
heatea in the presence of the silane derivative to I00C for 5
mins. and then cooled to room temperature before adding the
initiator and curing. A glossy, flaw~free sheet containing 50%
by volume of silica and having the mechanical properties re-
ported in Ta~le I is obtained.
Example 9
Example 7 iR repeated but with 0.050 g of n-propyl
amine added. The mechanical properties of the cured product
are reported in Table I.
- 53 -
C` ` 1~6S53Z
Example 10
1560 Grams of the coarse silica sand ~escribed in
Example 5, 600 g of distilled water and 1.2 g of sodium hydrox-
ide are ~harged to a 1 gallon ball mill along with 5,300 g of
`3~8" steatite balls. The ball mill i5 rotated for 24 hours as
in Example 5 and when the balls are separatea from the charge
a fluid dispersion of ine silica sand in water is obtained.
The silica has a particle size after comminuti~n similar to
that recorded in Example 5. The dispersion is then treated
with~0.15% by weight of the s`and of ~-methacryloxypropyl tri-
methoxysilane as a 5% solution in water, the p~ of,which has
been adjusted to 3.5 with acetic acid. The. aispersion is air-
dried overnight and then dried in an oven at~185C for 2 hours.
To 312 g of the dry silane-treated silica so obtained is then
added 14g g of methyl methacrylate monomer and 2.8 g of the
copolymer dispersant described in Example 5. The dispersion
is sheared~or 1 hour to realsperse ~he particles and a fluid,
~stable dispersion is obtained, This dispersion is then initi-
ated, cast and curéd as described ln Example 1 to give a flaw-
~free sheet containing 50~by volume of sllica and having themechanical properties reported in Table I.
11
Example 5 is repeated but using 4.5 g of ~-aminopro-
: pyltrimethoxysilane instead of the ~-methacryloxypropyl tri-
:~ methoxysilane.
`
` :'~ . :
~:
: :
~ ~ ~4 -
.
( " ~0~53Z
Table I
Flex. Flex~ Charpy impact
Example Type o composition mod. 2 strengt2h, strength,
. . GN m MN m ~ KJ m ~2
Silane derivative 12.5 114 ~ 6 6.8
added before com-
minution.
6 No silane 12.0 60 + 3 2~5
. derivative
7 Silane.derivative 12.0 78 ~ 5 3~9
added after.com- .
. minution. .
8 Silane derivativ~ 13.0 120 ~ 4 6.4
added after com- _
minution, with sub-
sequent heatingO .
9 Silane derivative 13.0 ~20 ~ 9 6.3
added after commi- . _
nution with n-pro-
. pylamine catalyst.
Sand comminuted in 12.0 73 + 4 3.7
water, treated with _
. silane derivative,
dried then redis- .
persed in monomerr .
11 Dif~erent silane 13.0 74 1.8
derivative used . .
from that of
Examples 5-10 ~ .
20 Compara- Unilled polymer: 3 100 6-8
tive Ex.~ _matrix _ ~ - -
In the above Table, the results of Example 5 illustrate
the efficacy o~ ~dding the interfacial bonding agent during
the comminution step along with the polymeri~ dispersant, as
compared with merely addi~g it after~comminution ~Example 7) or
. pretreating the a~ueous-comminuted silica (Example 10). ~xamples
8 and 9 illustrate the advantages of heat-and catalytic treat-
ment to promote utilisation of the interfacial bonding agent.
The relatively poor properties of the pxoduct of Example 11
illustrate the importance of selecting an interfacial bonaing
agent which can react with the polymer matrix; ~xample 6 shows
- 55 -
(
:10~553Z
that omission of added bonding agent leads to a similar result.
Comparative Examples H-I
This pair o Examples illustrate the importance of
using ~inely divided particles of the inorganic filler.
Comparative Example H
The coarse silica sand (average particle siz0 250 microns~
of Example 5 is admixed with the methyl methacrylate, silane
derivative and polymeric stabiliser described in that Example
to give a slurry containing 67% by weight of silica which settles
too rapidly for casting to be possible. In order to obtain a
sàmple for comparison, the sand is slurried in a syrup of 7.8
parts of poly(methyl methacrylate) and 51,2 parts of methyl meth-
acrylate t together with the silane derivative and polymeric dis
persant described in Example 5. The syrupy slurry so obtained
is heated to 100C for 5 mins., cooled and then initiated and
~ast as described in Example 1. The mould is rotated during
curing ~o prevent settlement. The casting so obtained has a
rough surface due to the presence of the coarse particles of
:
~ silica. The mechanical properties of t~e product are reported
ao ~in Table II.
Comparative Example I
A ball mill is charged with coarse sand, monomer and
other ingredients as described in Example S, but the mixture
is comminuted for 2 hours only instead~of for 24 hours. A
slurry which ha~ particles with the following aistribution of
sizes is obtained:
Particles of 10 microns or less 98% by number (7% by weight)
Particles of 50 microns or less - 529% by weight)
Particles of 100 microns or less - (55% by weight)
Particles of 250 microns or less - ~96% by weight)
- - 56 - ~
553Z
The sur~ace area o the particles as determined by nitrogen
adsorption is 0.16 m ~g. Since the slurry settles too rapidly
for direct casting, poly(methyl methacrylate) is added and methyl
methacrylate monomer evaporated off to make a handleable syrup,
in which the polymer to monomer ratio by weight is 1 to 6.6.
The syrupy slurry is then heated to lOO~C for 5 minutes, cooled,
initiated, cast as in Example 1 and cured in a rotating mould
to prevent settlement. The finished sheet has a rough surface
due to the presence of the coarse sand particles. The mechani-
cal properties of the product are reported in Table II~
Table II
_ .__ -- _ . _ .
Flex Flex Impact
Particle size Modulus, strength, strength
(~ by weight) GN m~2 MN m~2 KJ m~2
. .
Example 8 55% ~10 microns 13.0 120 6 3
100% ~30 microns
_
Comparative 55% elO0 microns 10.9 71 3.2
ExampIe I 96~ ~250 microns
~ - ~ . ~, .
~C`omparitive ~ b% ~2oo microns 9~7 37 2.4
Example H 99% ~450 microns
_ . . . . ,. .
The above compositions illustrate that, in addition to
the problems of man-pulating coarse particle slurries, markedly
inferior mechanical properties result from the use of coarse
particles, as compared with the properties of products of the
invention as exemplified by Example 8.
Examples 12, 13 and 14
The procedure o~ Example 5 is repeated except that
the concentration of silane derivative is increased to 1.5% by
weight on silica. Before curing, the methyl methacrylate con-
centration is adjusted so that the final silica concentrations
in the cured castings are 50%, 55% and 60~ by volume (67%, 72%
and 78~ by weight) respectively. The mechanical properties of
- 57 -
(` ` 1~1165532
the cured products are reported in Table III.
Table tII
Example % vol. Flex~ ~ ___ Impact Taber
. silica Mod. 2 strength, ctrength abrasion*
GN m~ MN m-2 KJ m-2
_ . . - ,. _ __
12 50 12 128 l6.3 _
13 56 14.8135 l6.1
14 60 15.3lS0 l6.1 13
Comparative 0 3 100 6-8 99
Example F
_ - . . _ __ __
*weight removed in mg~1000 cycles at 1000 g weight~
The above results illustrate how the mechanical pro-
perties of the cured composites continue to increase as the
particle volume increases. Furthermore, the abrasion results
indicate a 7-fold improvement over the base polymer.
Comparative Example J
: An attempt to produce a composite material according
to the procedure described in Examples 12-14 at a 60% volume
~raction o silica, employing the silane derivative but omit-
~ ting the polymeric dispersant, results in a cracked and flawed
casting.
Example 15
. Following a similar comminution procedure to that o~
Example 5~ 2726.50 g of coarse ~-cristobalite silica sand,
average size 200 micronsJ 903.85 g of methyl methacrylate
(containing 100 p.p.m. Topanol A), 7.81 g of ~-methacryloxy-
propyl trimethoxy silane and 57.89 g of-a 98:2 methy~ metha-
crylate/methacrylic acid copolymer dispersant are charged to a
2 gallon ball mill with 9,700 g of steatite balls, The mill is
rotated for 2~ hours at 60 rpm and then 254.32 g of rutile
titanium dioxide pigment is added. The mill is rotated ~ox a
- S8 -
1~65S3;~ :
further 4 hours, then the dispersion is separated from the
balls. The ~luid dispersion contains 77.8% by weight cristo-
ballte silica ana pigment particles; the particle size aistri-
bution after comminution is:
Particles o 10 microns or less 99% by number (70~ by weight~
Particles o 50 microns or less - ~99~ by weight)
Particles of 75 micrvns or less - ~100~ by weight)
To ~09 parts of the dispersion is added 1.18 parts Perkadox ~16
initiator and then 9.64 parts of methyl methacrylate is evaporated.
The dispersion is cast in to a stainless steel sheet mould which
i~ coated with a release agent, and then cured as describe~ in
Example 1. A glossy, flaw-free sheet containing 64~ by volume
(81% by weight) of silica and rutile particles is obtained.
The mechanical properties of the product are:
. Flexural modulus, 16.60 GN m 2, Flexural strength
139.7 MN m 2, impact strength 4O9 KJ m 2,
Examples 16-17
In these Examples, the dispersio~ of the inorganic
filler in the polymerisable liquid is sta~ilise~ by the formation
"~n situ" of- the calcium salt of an acidic ~opolym~r dispersant.
A mixture of 1333.5 g of coarse ~ cristobalite sand,
as described in Example lS, 3.82 g of ~-methacrylyloxypropyltri-
methoxysilane, 120 g of rutile titanium dioxîde, 14.15 g of a
25:1 molar ratio copolymer of methyl methacrylate and methacrylic
acid, 0.36 g (1 molar equivalent on acid present in copol~mer
dispersant), of calci~m oxide, 556.7 g of methyl methacrylate
(containing 100 p.p.m. Topanol A) i5 charged to a 1 gallon ball
mill together with 5,200 g of steatite balls and the mill is
~0 rotated ~or 24 hours to yield a dispersion containing 73% by
` - 5g -
553~
weight of particles having a particle size distribution similar
to that of Example S. The dispersion has a Brookfield viscosity
at 2 rpm and 20C of 0.8 poiseO A similar d:ispersion made
without the calcium oxide has a viscosity of 33 poise at 2 rpm.
To 280 parts of the first-described dispersion is added 24
parts of methyl methacrylate and 2.0 parts oE Perkadox Y16
initiator; at this stage the Brookfield viscosity is 0.2 poise.
The dispersion is cast and cured as described in Example 1, to
yield a glossy sheet containing 50~ by volume of silica and
rutile and having the following mechanical properties:
Flexural modulus, 10.55 GN m 2; Flexural strength,
113 MN m 2; Impact strength, 5 KJ m 2.
Example 17
To 280 paxts of the ball-milled dispersion described
in ~xample 15 is added 22.32 parts of a 45% by weight solution
of a 90:10 weight ratio methyl methacrylate/butyl acrylate co-
polymex in methyl methacrylate monomer, and a further 1.78
parts of methyl methacrylate monomer together with 1.8 parts
of Perkadox Y16 initiator. At this stage the Brookfield vis-
cosity of the dispersion is 53 poise at 20 rpm.and 20C~
The dispersion i5 cast and curea as described in
Example 1 to yield a glossy sheet containing 50% by volume of
silica and rutile, and having mechanical properties as follows:
Flexural modulus, 10.80 GN m 2; Flexural strength,
112 MN m ; Impact strength, S KJ m 2
Example_18
The following are charged to a 25 gallon ball mill
:,,
containing 60% by volume of 3/8" steatite balls:
- 6~ -
f~ 55 3 ~
Coarse cristobalite sand 2609 par-ts
~as described in Example 15)
Methyl methacrylate ~containing 1045 parts
100 p.p.m. To~anol A)
95.5 weight ratio copolymer of 26.3 parts
~ethyl methacrylate and dimethyl-
amlnoethyl methacrylate, Mw 50,000
Y-methacryloxypropyl trimethoxy- 7.1 parts
silane
distilled water 1.5 parts
The ratio of the volume of the charge to voias between
0 the balls is 1/1.
The mill is rotated at 60 rpm for 6 1/2 hours, a
dispersion being obtained in greater than 98~ yield having a
cristobalite particle size distribution similar to that o
Example 5. It contains 70% by weight (50~ by volume) o~ finely
divided cristobalite and has a Brookfield viscosity at 2 rpm
and 20C of 0.05 poise. Evaporation of some of the methyl
methacrylate gives a 78% by weight (55.6% by ~olume~ dispersion
havlng a viscosi~y of 0.40 poise.
To the 70% weight solids dispersion is added as
2Q internal release agent 0~15% by weight on the dispersion of
an alkanolamine-neutralised fatty acid phosphate known ~ommer- -
cially as Zelec NE (du Pont) and 2% by weight on the methyl
methacrylate of Perkaaox Y16. The dispersion is cast in a
glas plate mould and cured as described in Example 1. A
glossy, flaw-free sheet containing 54% by volume of silica
is obtained~ having the following mechanical properties:
Flexural modulus, 12.1 GN m 2; Flexural strength,
-2 -2
140 MN m ; Impact strength, 8.0 KJ m
- 61 ~
-`` 106S5~
Example 19
To a quart mill is charged the follow.ing:
Coarse tunnel-calcined kaolin, average
particle si~e 200 microns ('Moloch.ite' 6~-80)* 324g
methyl methacrylate (100 ppm Topanol. A) 113g
~-methacryloxypropyl trimethoxysilane0.46g
98:2 - copolymer of methyl methacrylate and
methacrylic acid, Mw lOO,OOO(G.P.C.) 2.8g
3~8" steatite balls 1,050g
The mill is rotated for 24 ho~rs at 90 rpm to g.ive a
fluid dispersion containing 76.3% by weight of finely divided
calcined kaolin. The final particle size distribution of the
dispersion is:
Particles of 10 microns or less 99.5% by number
(70% by weight)
Particles of 50 microns or less - t~3% by weight)
Particles of 75 microns or less - (97.5% by weight)
Particles of 100 microns or less - ~1007 0 % by weight)
~he dispersion is diluted with further methyl methacrylate,
initiated, cast and cured as described in Example 1 to yield
a flaw-ree sheet containing 50% by volume of inorganic parti-
cles and having the following mechanical properties:
Flexural modulus~ 13.6 GN m 2; Flexural streng~h,
130 MN m ; Impact strength, 6.6 RJ m 2
* 'Molochite' is a Registered Trade Mark of ~nglish China Clay
Limited for a mixture of 56% mullite and 44% amorphous silica.
Example 20
To a 1 gallon ball mill is charged the following:
Coarse alumina trihydrate (80~BS sieve 1452g
300; com~ined water 34% by weight, free
water 0~ by weight)
y-methacryloxypropyl trimethoxysilane3.8g
dispersant copolymer as described in14~16g
Exampl~ 19
- 62
6553;Z
methyl methacrylate (100 ppm Topanol A) 556.84g
3~4" steatite balls 5200g
The mill is rotated for 10 hours at 60 rpm, to yield a finely
divided low viscosity dispersion containing 7~ by weight
o~ alumina trihydrate in methyl methacrylate. The dispersion
i9 initiated, cast and cured as described in Example 1 to
yield a glossy, flaw-free sheet with the following mechanical
properties:
Flexural modulus, 13.8 GN m 2; Flexural strength,
B0.7 MN m . The shee~ does not catch ~ire when placed in
contact with a bunsén~burner flame for one minute.
Example 21
The procedure of Example 5 is repeated~ but with
the following reactants charged to the mill:
Coarse ~-cristobalite sand as describad 2478.6g
in Example 15
Rutile titanium dioxide pigment 223.00g
- Methyl methacrylate (100 ppm Topanol A) 1045g
~-methacryloxypropyl trime hoxy silane 7.1 g
Dispersant copolymer as described in 26~3g
: Example 19
3/8" steatite ~alls ` 9,700g
After rotating the mill for 24 hours, a dispersion of 73.5~ by
weight of cristobalite and rutile in methyl methacrylate is
obt~ined, having a Brookfield viscosity of 3.5 poise at 20C
:
and ~0 rpmO The particle size distribution o~ the dispersion
is as follows:
: Particles of 10 microns or less 99.7% by number
t8a~ o% by weight)
Particles of 50 microns or less - (95.5% by weight)
Particles o 75 microns or less - ~100~0% by ~eight3
~ter diluting the dispersion with further monomer t~ a
- 63 -
(36~i3~
Brook~ield viscosity o~ 0.4 poise at 20 rpm and 20C, and
initiating and curing as described in Example 1, a sheet
containing 50% by volume of cristobalite and rutile is
obtained. The mechanical properties are:
Flexural modulus, 10.6 GN m 2; Flexural strength,
118.9 MN m ; Impact strength, 5.9 KJ m 2
EXAMPLE 22
The dispersions described in Examples 20 and 21
are mixed in the weight proportions o~ 2:1 respecti~ely,
then initiated and cured as described in Example 1. The
cured casting has the ~ollowing mechanical properties:
Flexural modulus, 12.4 GN m ; Flexural strength,
102 MN m 2. When one end o~ a 4 inch long by 1/2 inch wide
rod of the composition is held horizontally in contact with
a bunsen burner flame ~or 1 minute, the composition ignites
and buxns with a small blue flame which extinguishes itself
in a few seconds.
Example 23
To 1600 parts of the ball-milled dispersion o~
20 Example 21 ale . ~ _
,
.
.
- 64 -
~165532
added 43 p~r~s of polyvinyl chloride particles (Corvic P65/50 ~,
rollowed by the evaporation Or 43 parts of methyl methacrylate monomer.
me polyvinyl chloride particles ~orm an organosol dispersion in the methyl
methacrylate mQnomer. The dispersion is cast and cured as in Ex~mple
1 to yield a glossy, flaw-~ree sheet containing 53.6% by volume of
cristobalite and rutile in a matrix of polymethyl methacrylate and poly-
vinyl chloride. The product ha~ similar mechanical properties and
surface finish to that described in Example 21. In a buming test
carried out as in Example 22, a sample burns very much more slowly than
the product of Example 21
.
* Corv_c P65/50 is a Registered Trade Mark of Imperial Chemical
Industries Limited ~or a spray-dn ed emulsion-~polym,erised polyvinyl
chloride.
Exam~le 24
This Example illustrates the ef~ect of cross-linking in accelerating
the cure of the fluid composition and preventing boiling of Dnomer.
To 321g of the dispersion of Example 21 i~ added 24.2g of methyl
methacrylate, 6.og of ethylene glycol dimethacrylate and 2.36 p~rts o~
Perkadox Y16. The dispersion is cast in a preheated fla~ plate ~Quld
in an oven at 80C. A~ter 6~ minutes, a solid, flaw-free casting i~ -
removed from the mould. The temperature inside the m~ulding reaches a
maximum of 154C. The mechanical prDperties of the product are as
fbllows:-
Flexural modulus, 13 GN m 2; Flexural Strength~ 128 MN m 2;
Impact strength, 4.3 KJ m 2.Repeating the above pr~cedure but omitting the ethylene glycol dimethacrvlate
leads to the production o~ a bubbled and blown casting.
- 65
''''
. ~ ,
.
~6~i~3Z
Example 25
The procedure of Example 24 i9 repeated with a mould and
oven temperature of ~0C. After only 4 minutes, a solid, Maw-free
casting i~ removed from the mould; the peak temperature attained is 155C.
Example 26
~his Example illustrates the '~eat sink" effect of the inorganic
particles in preventing monomer boiling during the curing operation.
~he dispersion of Example 21 is adausted by removal of some
monomer so that after curing the volwme proport-on of cristobalite;and
rutile combined in the composite will be 60%. me dispersion is initiated
w~th 2% of Perkadox Y16, based on the free methyl methacrylate pre~ent,
and is cured at 80C as in Example 24. A solid cast sheet is remDved
from the mould after 10 minutes. In contrast, a sheet containing 50%
by volume of filler cured under these conditions is badly flawed and blown.
Examples 27-30
This series of Exa~ples illustrates the range of initiators that
can be u~ed for curing the fluid compositions and the absence of any large
effeot of initiator variation on the mechanical properties of the cured
~ products.
Example 24 is repeated, but using the initiators and quantities
shown below:-
~~~ex. ~ ~
Initiator ~emp. ¦ Cu~e time mod., str~ngth,
wJw on monom~r C. min. GN m~2 MN ~-~
~; Example 27 2% BP 2% DMPT 23& 30 mins. 10.6 116
Example 28 0.5~ Y16 0.5% ADI3 80& 10 mins. 10.16 109
Example 29 0.5% IPP 0.5% DCP~ ~0C 9 mins. 10.56 114
~0.~% IPP 0.9% BP ~ C13 mLns. 10.94 111
66 -
3L065532
~P - Benz~l peroxi~e
~MP~ - Dimethyl paratoluidine
Y16 - "Perkadox" Y16 - bis(4-tert-butylcyclohexyl) peroxydi-
carbonate.
ADIB -2~azo-bis-isobutyronitrile
IPP = Diisopropyl peroxydicarbonate
DCP - Dichloro benzoyl peroxide.
Exam~le 31
'Dhis Example ill~strates the use of a rotational moulding
procedure.
To 300g of the ball-milled dispersion described in Example
; ~ 21 is added a ~urther 11.3g of the ~ispersant described in Example 19,
5 5g of ethylene glycol dimethacrylate~ 8,7g of methyl methacrylate,
1.6 parts of benzoyl peroxide and 1.6 parts of dimethyl paratoluidine.
The Brookfield viscosity of the dispersion so obtained is 40 poise at
~20 r.p.m. and 20C. The dispersion is placed in a closed 1 pint
polypropylene truncated cone tub mould (top diameter 12 cm, bottom
diameter llcm, length 12cm). The tub is rotated about the axis of symmetry
at 7 rOp-m- and about the end-over-end axis at 16.5 r.p.m. at room
20~ temperature. After 30 minutes a flaw-free, thin-walled moulding which
reproduces exactly the internal con~ours of the mould is obtained.
~ple 3,?
~ This Example illustrates the production of a fibre-
mcdiff ed composlte material. ~ ~
~ ` The curable composition used is the dispersion described
in Example 21, of Brookfield v scosity 0.4 poise at 20 r.p.m. and 20& ,
with initiator added;and ready ~or casting so as to give a cured`sheet
with a 50% by volume content of cr~stobalite and rutlle. This dispers;on
~ . .
3L~6;553Z
is pumped at very low p~es~ure head (less than 10 p.s.i.), using a
peristaltic pump~ into the bottom of a vertically held 3/16" thick ~lat
plate nuld, which contains two layers of chopped ~trand gla~s fibre mat.
(Supra E Mat F`PL436) and two laye~ of glass ~lbre surface veils~
Pumping was continued until the dispersion issued from the top of the mould.
The inlet and outlet were then clanped 90 as to seal the mould and the
sample was cured in the mould for 2 hours at 50C ~ollowed by 2 hours
at 80C .
The final cured sample was free from entrained air and flaws,
~0 and contained 56% by weight of cristobalite and rutile and 15.6% by wei~ht
oP glass fibre strand. ~he mechanical properties were as follows:-
Flexural modulus~ 12.5 GN m 2; Flexural strength, 95.0 MN m 2;
Impact strength, 27.0 KJ m 2,
~ Supra E Mat i6 a Registered I~ade Mark oP Fibre Glass Limited
Por a polymer latex-bound chopped gla~s fibre strand mat with approximately
200 Pibres per strand; each fibre is approximately 10 microns in diameter.
Comparat~ve Example K
An attempt is made to inuect the slurry described in Conparative
Example I, which contains particles larger than 100 microns, into a glass
fibre-Pilled mould under the conditions described in Example 32. The
mould very quickly becomes blocked and no further slur~y can be injected.
A further attempt is made by reducing the concentration oP silica in
the slurry to 40% by v3lume, but the m~uld still becomes blocked.
Example 33
381 Grams oP the dispersion described in Example 24 (50%
by vvlume of cristobalite and rutile in the cured product) is initiated
with 2.5g of benzoyl peroxide and 2.5g o~ dimethyl para toluidine.
The dispersion, having a Brookfield viscosity less than 5 poise at
- 6~
~lal6553Z
20 ~.p.m.and 20C, was then placed in a tub mould as described in Example
31 which is lined with one layer of' surface veil and one layer of
continuous strand glass fibre mat (FPL455 ex~ Fib:reK~,ass Limited; each
strand contains about 20 fibres of 10 microns diameter). ~he clo~ed
mould is rotated at room temperature for 1 hour in the same way as
described in Example 31. A fibre-reinforced, thin-walled moulding
is obtained, with complete wetting ou~ of the ~ib:res and exact
reproduction of the mould conto~rs.
~7
.
69 -
1~165~ii~;2
A sheet o~ clear orientated lJ32" thick cast poly
methyl methacrylate (Perspex, ex I.C.I. Ltd) was placed
against one ~ace of a 3~1~" thick cavity sheet mould. Two
S layers of chopped strand mat as describ~d in E~ample 32 were
placed in the mould~ and the mould faces were then closed.
The dispersion of Example 32 is pumped into the mould in the
manner described in that Example. Aft~er curing for 10
minutes at room temperature and post-curing at 80QC.~ a high
quality 3/1~" thick moulding is produced which is cornposed
of a glass fibre-reinforced composite according to the
invention, bonded to the acrylic sheet. The mechanical
properties are as follows:-
_ __--~---------------~-- Acr7l~ Acrylic F~
in Tension in Compression
.. ~
Flexural Modulus~ GNm 2 6.5 6.3
Flexural Stre~gt~ MNm 2 115 109
~ t se.-~9~ 2~.5 _ _
- ~
The dispersion of Example 21 is modified by
addition of furth~r methyl methacrylate to yield a d$spersion
which after casting and curing as described ln Example 1 gives
a 3~3 mm thick sheet which contains 30% by volume of
cristobalite and rutile. This sh~et is heated to 180C in
an alr oven, a~d then clamped in place over a 10 cm-diameter
hole, compressed air is applied to one side of the hole and
a 9 cm high blister is blown without fracture o the composite
occurring. The thickness at the apex of the bli~ter i~
approximately 0~2 mm~
- 70 -
S3;2
~a~
A 3.3 mm-thick ~h~t ~s cast :Erom the dispersion
described in Example 21, containing 50% by volume of
cristobalite and rutile. The sheet is then heated to 180C
and blow moulded a~ described in ~xamplle 35. A 6cm-high
blister is formed without fracture o the material.
An unsaturated polyester resin, which contains
a proportion o mono-carboxylic aci~terminated polymer
chains capable o~ functioning as th~ polymer dispersant and
is free ~rom dicarboxylic acid-terminated chains which
would act as flocculants, is prepared (uslng excess glycol)
by condensing the following ingredients:
Isophthalic acid 26 parts
Maleic anhydride 32 parts
Propylene glycol 42 parts
toluene being present as a water-entrain~ng sol~ent. Glycol
loss is prev~nted by the use of a short Vigreux column.
Th~ reaction is continued until the acid value of the
mixture drops to 10 mg KO~g, when 11.5 parts of evolved
water have been collected. To reduce the chance of the
presence of a dicarboxylic acid-terminated chain still
further, 3.8 parts o Cardura E~ is added and the reaction
~ixture is held a~ about 230C until the acid value drops
~o about 1.0 mg KOH/g, when approximately one chain in every
twenty is terminated with acid groups. The batch is cooled
to below 80C, applying vacuum to remo~e as ~uch toluene as
possible, and the reaction mixture is thinned to about 70~
~65S3Z
solids with styrene to give a viscosity in the reglon of
13 pois~,a hydroxyl value around 25 mg KOH/g non-volatile
re~in and a polyester number average molecular weight of
approximately 2,000 - 39000- To this product is then
added 0~02~, based on solid resln, of Topanol 354~.
A 50~ by volume silica ~ispersion in a 50%
non-volatila-content solution of polyester in styrene is
made by charging the following to a pug mixer and mixing
for 2 hours:-
Finely divided silica
("Minusil" 30~) 312 parts
68% by weight solution of
polyester in styrene made
as described above 89.3 parts
Styrene 33.9 parts
r-Methacryloxy propyl
trimethoxy silane 2.gB parts
,
1% solution of hydroquino~
in styrene 1.0 part
A low viscosity, deflocculated dispersion contalning 71% by
weight silica ~s obtained1 which is self-de-aerating and self-
levelling. The dispersion is initiated with l.5X of benzoyl
: peroxide ba~ed on th~ resin and styrene present. After
casting in a glass plate mould and curing at 80C for 1 hour,
a high quality plaque is obtained. Viscosities and
m~chanical properties are reported in Table IV.
nCardura" E is a Registered Trade Mark of She}l
International for a glycidyl ester of a branched ~ ~ C13
saturated fatty acid, with epoxide value typlcally o~ 245.
~"Topanol" 354 is a Registered Trade Mark of
Imperial Chemical Industries ~imlted for 2, 6-di-tert-butyl-
4-methoxyphenol.
_ 72 -
~0~5S3Z
~"Mlnusll" 30 is a Registered Trade Mark of
Pennsylvania Glass Sand Company Limited for dry-groun~
air-classifled ~-quartz sllica having th~ following particle
size distribution:
Particles o~ 10 mlcrons
or less 9g.8 by number (52% by weight)
Particles of 50 microns
or less ~86% by weight)
Particles of 100 microns
or less (100~ by weight)
The follow~ng ingredienta are charged to a pug
mixer and mixed for 2 hours:-
Minusil 30~ 312 parts
~ Solution of polyester in
styrene (as described ~n
: Example 37) 50 parts
Styrene 65 parts
~-methacryloxypropyl
: : 20 trimethoxy silane 2.98 parts
1% hydroquinone solution
in sty~ene 1.0 part
A very low viscosity, deflocculated dispersion containing
72% by weight of silica is produced and, on curing as
described in Example 37, a high quality casting results.
Viscosities and mechanlcal properties are listed in Table IV.
'See reference in Example 37.
.~ ' ~
The procedure of Example 38 is repeated but omitting
the silane derivative. A very low viscosity disperslon and
a bigh quality castlng are again produced. Viscosities
and mechanical properties are shown in Table IV.
73 -
" ~0165~;3Z
The procedures of Examples 37 and 38 respecti~ely
are repeated uslng an lsQphthalic acid-based polyester of
similar composition but having an acid value of 25 mgm KOH/q
~o~volatile). The relatively high aci.d value of this
polyester, which is typical of commerciallly available
polyesters, indicates that it con~ains ~i substantial
proportion of short dicarboxylic acid terminated chains
which act as flocculants rather than dispersants. In each
case a dispersion is prepared containing SOX by volum~ o~
silica (Minusil 30). The considerably higher viscosities
of the dispersions obtained9 as shown in Table IV~
demonstrate clearly that the dispersions are ~locculatedO
Comparative Examl~les N - Q
These Examples illustrate th~ compositions
descrlbed in Examples 37 - 39 and Comparative Example M when
: the slllca filler is omitted; the curing conditions used
are those described in Example 37. Vlscosity data and
other results are shown in Table IV.
:~
- 74 -;
I-- a r~ a I ,1 N o
a~ t~ E ~ I I
U~ I I
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~ .. .. . .. _ ........ ,
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x ~ I ~ o a~ a) ,, a~
~d a) ~: E
U ~ " ~ C ~: ,1
. ~ ........ ....... _... . ..... .. _ q
O
: E ~ tn I I tn
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~1
. _ ~ ., _.. _ ........ .
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O
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,~ rl r~ tf~
rl~ O O O O O O ~`
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S~ S~ U Q~ ~ U S~
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r I ~) ~ i~ m lQ r l
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I r~ ~
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Q O rl O Z 11~rl P~ Z Orl O r~
C4 r1 ~ 4 r~ ~r l P- r
1~ ~ ---rl ~ --~
O ~ C,) m ~ 0 ~n ¢ - > aJ ~n ~ ~ ~n
.,, ~ c ¢ a) ~ ~ ~ c: ¢ ~: .
~-1 3 ~I r~ 3 0 ~ .4 r~~ (1) 3 $-1 r~ ~ 3 S~ r1
U~ O :~ O O O ~1 rl ~ O ~1) rl S~ O ~>1 0 0 O ~ O
O r~ r~ ~I S ~ > 1~ ,C ~ r~ r~ ~ >
Q. m td
E ~Se ~ rl ae ~n a~ ~ m ~ ~e r~
o o ~ o-rl o o s: o .~ o o ~ o rl o ~ o
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.rl Z rl ~1 rl O
aJ ~ ~ .IJ
r I d Q)td a~ Id a) a (11
~ h ~ h r~ rl r~
E ~ D. ~ p~~d Q, p,
~ Q- E C)~ EQ. ~ El E
x ~ la E ~
O X OX OX X X . ~
'U ~ ~ U ~ 1~1 ~
,
u~ o ~ o 1~65~i3~
- -
- -~
~ii553Z
I ~
ta , v
~ I a)
I~ h
~ ~ ~1
. O ~ ~ .
~a
. .~
_ , .
_U~
~.,1 ~~,~
O ~,O ~o
~:: . o o o
I~ O
_
U
~s~
E~~
.,1 U~ lA~rl
In ~
~0 ~ ~ ~0
O Z ~ O Z;
-
:
a) s~ s~
O ~ ~r~ ~ O
r~ S
i:: ~ C
." ~U~
_
a
o 0
~Ei ~E P.E~
O ~ O X O ~
UWt)~d VW .,
___
U~
J
~6SS3Z
From th~ results in qabl~ IV it is clear that the low acid value polyéster,
havLn~ a low probability of containing di-~unctional acid species,
gives rise to dispersions of much lower viscosity than does the hi~h
acid value polyester. On curing,the ~luid compositions o~ Examples
37, 38 and 39 yield composites stronger than the matrix polymer.
This ef~ect is most apparent with the 30%-non-volatile polyester
cQmpositions, for the unfilled 30%-NV polyester does not even cure to
an homogenous solid.
, . . .
/
/
~: .
_ 77 -
: ~.
~ii553Z
~xample 40
This'Example and Examples 41-42 illustrat~ the use
of a matrix polymer which is derived from methyl methacrylate
and the bis(methacrylic acid) adduct of an epoxy resin.
S 1640 parts of a flnely divided ~-crystobalite ~ilicat
having a surface area of 3m2/g and a particle si~e dlstribution
as follows:-
part~cles of S microns or less - (40~ by weight)
particles of 10 microns or less 99.9X by number (81% by weight)
particles of 50 microns or less - (100% by weight~
are dispersed in a ~ixture of 120 parts of methyl methacrylate
and 480 parts of a 50% solution in methyl methacrylate of a
bis~methacrylic acid) adduct of the epoxy resin known as
"Epikote" 1004 (Registered Trade Mark), which i5 a
condensation product of epichlorhydrin and diphenylolpropane
having a molecular weight of about 1800, in the presence of
40 parts of a solution of a dl~persant as d~scribed below.
The d~spersion i5 carried out u~ing a high speed laboratory
Torrance Cavitation Disperser, the silica being added gradually
whilst the monomer/adduct mixture is stirred, the disperser
finally being run at 1000 r.p.m. for 30 minutes to complete the
operation. A fluid dispersion is obtained~ the viscosity of
which is measured by means of a Brookfield Viscometer,
multispeed model RVF (Brookfie1d Engineering Laboratories IncD,
: 25 Massechusetts, US~). In a por~ion o the dispersion is dissolved
2% by weight, ~ased on the monomer/adduct content, of Perkadox
Y16 initiator, the material is dega~sed under reduced pressure
and is then moulded at 50C for 2 hours, and then at 80C for
2 hours, into a sheet of composite material containing 54%
- 7~ _
-`` lQ~55~
by volume o~ silica. Physical and mechanical data or this
Exampla are given in Table V. In this and the following
Examples, viscosities are expressed in poise at 20C. Where,
in the case of shear-thickening or shear-thinning compositions,
two viscosity values (a) and (b) are given, those marked (a)
are measured at 2 rpm using the Brookfield spindle size
stated and those maxked (b) are measured at 20 rpm, again
using the spindle size stated. Where, in the case of essen-
tially Newtonian compositions, only one viscosity value is
given, this is the value measured at 2 rpm.
The bis(methacrylic acid) adduct of the epoxy resin
used in the above procedure is made by heating under reflux
at 135-140C for 1 1/2 hours the following ingredients:
"Epikote`' 1004 720 parts
Butyl acetate 500 parts
Hydroquinone 0.1 part
Dimethylaminoethanol2 parts
Methacrylic acid 70 parts
In this~way, 90~ of the epoxide groups present in the epoxy
resin are converted to ester groups by the methacrylic acid,
as in~icated by acid value measurements. The solvent is
removed under reduced pressure at 70C and the residue dis-
solved in methyl methacrylate to provide a 50~ solution.
The dispersant solution used in the above proce-
dure is made as follows: The above-described preparation of
the epoxy resin adduct is followed, but with the quantity of
methacrylic acid reduced to 50 parts. To the product, without
removal of the solvent, is added 33 parts of p-nitrobenzoic
- 79 -
~tiS~i3Z
acid and 1 part of dimethylaminoethanol. The mixture is
heated at 135-140C under reflux ~or 2~ hours and then the
solvent is removed at 70~C under vacuum. The resulting
dispersant is dissolved in methyl methacrylate to give a
50X solution.
Comparative Example R
The procedure of Example ~0 is repeated, but
omitting the solution of the dispersant. Viscosity
measurements on`the dispersion obtained show it to exhibit
lQ substantial shear thickening. These data and properties of
the cured composite material are given in Table V.
The procedure of Example 40 is repeated, but with
the incorporation, just prior to the final stage of dispersing
the silica at 1000 r~p.m. for 30 minutes, of Y-methacryloxy-
propyl trimethoxysilane and water in the proportions o~ 4 parts
and l part respectlvely to 2240 parts of the silicafmonomer/adduct
mixture. The physical and mechanical properties recorded
are given in Table V~O
~ Table V
~ ~ __ __ , . . . - . , .
Example Type of Viscosity ~ QE~ osite
No. composition of fluid Modul~s Flex. Impact
composition GNm~ Strength Str~n~th
(a)~ ~b)~ MNm~Z KJm-~
~ ~ _ ___
40 ~ispersant 25 129 12.0 88.5 4~0
pre~ent
Comparative No 100 440 13.7 109 5.4
R Dispersant
41 Dispersant 22 89 12.5 130.7 6.6
and inter-
facial bond-
__ ~nsss~n~ _. . _ , _ ___, _
D--~30
106S53;~
(a) measured with Brookfield spindle No. 2
tb~ measured with arookfield spindle No~ 5 or 6
The results shown in Table V demonstrate the marked
improvement in the fluidity of the curable composition which
results from the use of the polymeric dispersant, and also
the further improvement in fluidity achieved by incorporatin~
an interfacial bonding agent during the process of dispersing
the filler.
Example 42
The procedure of Example 40 is repeated, but using a~
the starting materials 1640 parts of the finely divided silica,
120 parts o methyl methacrylate, 310 parts of the 50% solution
of the epoxy resin adduct, 170 parts of a dispersant solution as
described below, and 1 part of water. The dispersion obtained
has viscosities of (a) 66 poise (spindle No. 3) and (b~ 37~
poise ~spindle No. 6)~ The cured composite material, containing
54.0% by volume of silica, has modulus 15.1 GNm 2, flexural
strength 154 MNm and impact strength 7.9 KJm 2.
The dispersant solution used in this procedure is
obtained as follows. The procedure described in Example 40 for
the preparation of the epoxy resin adduct used therein is
ollowed, e~cept that the amount of methacrylic acid is reduced
to 50 parts. To the 50~ solublon of the adduct is added 35 parts
~ of Y-aminopropyl trimethoxysilane and the mixture is allowed to
~ 25 stand overnight to complete the reaction of the residual epoxide
groups of the adduct with the amino groups of the silane
derivative.
Exam~le 43
This Example illustrates the use of a polymerisable
- 81 -
55i3Z
system based on styrene and chlorophenylmaleimide.
~ 12 parts of chlorophenylmaleimide are dissolv~d
in 208 parts of styrene with sli9ht warming, glvlng a 1:3
molar comonomer mixture. To this are added 26 parts of a
50% solution of a dispersant as describr!d below, followed by
1410 parts of the finely divided silica described in Example
40. The silica is dispersed in the manner described in
Example 40, there being added, ~ust prior to the final
stage of dispersion at 1000 r.p.m. 3.5 parts of ~~methacry-
loxypropyl trimethoxysilane and 0~7 part of water. A fluiddispersion is obtained (viscosity 9 poise) which can be cured
as described in Example 40 to give a sheet of composite material
containing 53.7% of silica by volume.
The dispersant solution used in this Example is
obtained as follows. To a mixture of 0.85 part butanol, 2.0
part of glycidyl methacrylate and 17.8 parts of hydroxyisopropyl
methacrylate, warmed to 30C, there are added 2.5S parts of
methacrylamide, together with a little water to assist
dissolution. 13.2 Parts of styrene, 20.1 parts of 2-ethylhexyl
acrylate and 0O5 part of tertiarybutyl perbenzoate are then
added. 42.2 Parts of xylene are heated to reflux temperature
(140C) and the foregoing monomer mixture is fed in over a period
of 3 hours, with the addition of a further 0.1 part of tertiary-
- hutyl perbenzoate after 1 hour. Heating at reflux temperature
is continued until the mixture has a solids content of 43-51%.
The mixture is tnen cooled to 110C and 0.6 part of p-amino-
benzoic acid and 0.1 part of "Armeen" DMCD (Registered Trade
Mar~ for dimethyl cocoamine) is added. Heating at reflux
_ 82 -
~(~6;S53Z
is resumed and continu~d until the mixture has an acid value
below 0.5 mgKOH~g~ The xylene is then removed by vacuum
distillation and the residual solid polymer is dissolved in
styrene to give a 50% solids solution.
S Comparative Example S
The procedure of Example 43 i~3 repeated, but omitting
the dispersant solution. When only 32% by volume of the
silica has been added, the dispersion has already become highly
thixotropic and cannot be moulded.
~e~
This Example ~nd Example 45 illustrate the use of
a polymerisable system based on methyl methacrylate copolymerised
with a reaction product of hydroxyethyl methacrylate and a
melamine-formaldehyde resin.
A mixture of 180 parts of paraformaldehyde, 126 parts
of melamine, 185 parts of n-butanol and 200 parts of water
lS adjusted to pH 9.0 using 2 sodium hydroxide solution, and is
then heated under reflux for 30 minutes. To this mixture
is added 780 parts of hydroxyethyl methacrylate (this contains
sufficient free methacrylic acid to lower the pH of the mixtue
to 4.5), ~.5 part of hydroquinone and 200 parts of toluene.
The mixture is heated and water removed by distillation, using
a Dean and Stark separator. During distillation over 3 hours
the temperature of themiXtUre rises from 88 to 120C and 314 cc
of aqueous distillate are removed. The product is filtered,
giving a low viscosity syrup. A dispersion is then prepared,
by the method described in Example 40, from 1210 parts of the
finely divided silica described in Example 40, 125 parts of the
_ 83
:~0~553Z
abo~e-described syrup, 375 parts of methyl methacrylate arl~ 20
parts of the methyl meth~crylate-dimethylaminoethyl methacrylate
copolymer dispersant described in Example 18. A highly fluid
dispersion is obtained; the properties of the dispersion and
S of a composite material, containing 48.0~ by volume of silica,
produced therefrom by curing are given in Table VI.
Example 45
The procedure of Example 44 is repeated, but with
the addition, just prior to the final stage of dispersion at
1000 r.p.m. for 30 minutes of S parts of Y-methacryloxypropyl
trimethoxysilane and 1.25 parts of water. The properties
of the dispersion obtained and of the composite rnaterial
produced therefrom are given in Table VI.
Comparative Ex~ le T
The procedure of Example 44 is repeated, but
omitting the copolymer dispersant. The dispersion repidly
becomes thixotropic during the addition of the silica and
only 46~6% by volume of si7ica can be incorporated. The
properties of the dispersion and the derived composite are shown
in Table VI.
Table VI
Example Type of Viscosity ~ !S of con ~osite _
No. composition of fluid Modulus Flex. Impact
composition GNm~2 stren~th strength
~ ~ eS~Q______ - MNm ~ KJm~2
44 Dispersant 0.85 12.23 81.9 3.21
45 Dispersant 0.74 11.81 119 5.55
~ interfacial
30 1 ~ bonding L___________ _ _
_ ~34 -
iS53;~
Table VI (continued)
. _ ~ _ _ _
Example Type of Viscosity Pro~ert les of co
S No. ~omposition composition GNm~~ stren~kh Impact
_- . _ __ _ ~ _
Comparative No disper- 6.5 11.48 66.9 3.14
T sant or
_ bonding _ ~ ~ _
Here again the results show the progressive improvement
in the fluidity of the curable composition, and in the properties
of the derived composite material, resulting from the incorporation
of the polymeric dispersant and further of the interfacial bonding
agent.
Example 46
This Example illustrates the use, as the basis for
the polymer matrix, of a copolymer of methyl methacrylate
and a vinylidene-terminated urethane prepolymer.
A prepolymer is prepared by dissolving 400 parts of
"Desmodur" N (Registered Trade Mark for a trifunctional isocyanate)
in 686 parts by volume of methyl methacrylate, together with
: 0.1 part of hydroquinone and 1.0 part of dibutyltin dilaurate.
286 Parts o hydroxyethyl methacrylate are added slowly over
45 minutes? and the mixture allowed to stand for a further
90 minutes (during which time the temperature rises to about
5oo~
A dispersion is then prepared, by the method described
in Example 40, from 1340 parts of the finely divided silica
described in Example 40~ 220 parts of the above-described
- prepolymer, 220 parts of methyl methacrylate, 60 parts of a
_ 85 -
~ iS532
dispersant solution as described below and 1.2 parts of water.
The dispersion is highly fluid, with a viscosity of 2.0
poise only, and is easily fabricated into a composite material
containing 53.3~ by volume of silica and having the following
excellent mechanical properties: Modulus, 12~04 GNm 2;
1exural strength, 129.6 MNm 2; impact strength, 6.75 KJm 2.
The solution of dispersing ag~nt used in this
procedure is obtained by dissolvin~ 480 parts of "Desmodur" N
in 806 parts of methyl methacrylate, together with 0.1
part of hydroquinone and 1.0 part of dibutyltin dilaurate,
then adding 260 parts of hydroxyethyl methacrylate over a
period of 45 minutes and allowing the mixture to stand for a
further 1~ hours; ~inally, 72 parts of Y-aminopropyl
~ trimethoxysilane~are mixed in and the mixture allowed to
stand overnight.
Comparative Example U
The procedure of Example 46 is repèated, but omitting
the solution of the dispersing agent and increasing the amounts
.
of the~ prepolymer and the methyl methacrylate to 250 parts
each. The dispersion which results is very viscous and cannot
~ be moulded.
Example 4 ?
This Example illustrates the use of polymer matrix
based on polystyrene, with the filler having been produced by
comminution in the presence of a dispersant and an interfacial
bonding agent.
1264 Parts of coarse ~-crystobalite silica, 497
parts of styrene, 3.5 parts of ~-methacryloxypropyl trimethoxy-
silan~, 1.0 part of water and 50 parts of a 25% solution in
_ 86 -
~Qt~5~3~
styrene of a dispersant copolymer as described below are ground
in a ball mill according to the method described in Example 5.
A dispersion is obtained which contains 50.0% by volume of
silica and has a viscosity of only 0.6 poise.
S The dispersant used in a 1:1 by weight block copolymer
of cis-1~4-polyisoprene and poly(dimethylaminoethyl methacrylate)
in which both polymer blocks have a molecular weight of 10,000.
_L~
The procedure of Example 47 is repeated, but omitting
the dispersant solution and the silane derivative and increasing
the amount of styrene taken to 540 parts. The dispersion
obtained again contains SO.OX by volume of silica but it
is viscous and markedly thixotropic.
Example 48
This Example and Examples 49 and 50 illustrate the
use of barium sulphate as the inorganic filler in a methyl meth-
acrylate-based system.
1700 Parts of Blanc Fixe (a precipitated barium
sulphate of surface area 3.3 m2/g and an average particle size
of 0.5-O.~i microns) are dispersed in 500 parts of methyl
methacrylate and 20 parts of the copolymer dispersant described
in Example 5, using the procedure described in Example 40~
A very fluid dispersion is obtained (viscosity 2.5 poise),
containing 43.6% by volume of Blanc Fixe.
Example 49
The procedure of Example 48 is repeated, but
replacing the copolymer dispersant there described by 18 parts
of the copolymer dispersant described in Example 18 and
- 87
1~53Z
increasing the amount of Blanc Fixe to 2330 parts. The
dispersion obtained contains 50% by volume of the filler and
h~s viscosities of ta) 33 poise (spindle No. 4) and (b) 14Q
poise (spindle No. 7). A composite material obtained by
S curing the dispersion has modulus 12.04 GNm 2; flexural
stren~th ~4.1 MNm 2; impact strength 1.68 KJm 2
~e~
The procedure of Example 49 is repeated, but with
the addition o~ 5 parts of methacrylic acid after the Blanc
Fixe is fully incorporated. On making this addition, an
immediate and substantial increase in fluidity of the dispersion
becomes apparent. The dispersion has a viscosity of only 1.0
poise and a composite material obtained from it by curing
has modulus 8.98 GNm 2; flexural strength, 48u9 MNm 2; impact
strength, 1.93 KJm 2. The improved fluidity of the dispersion
may be attributable to conversion of the tertiary amine anchor
groups in the dispersant copolymer to the corresponding meth-
acrylic acid salt groups.
Comparative Example W
The procedure of Example ~8 is repeated, but omitting
the copolymer dispersant. After the addition to the methyl
methacrylate of only 15% by volume of Blanc Fixe, the dispersion
becomes so dilatant in character that further addition of filler
is impossible.
~
In this Example and Example 52, the polymer matrix
is derived from a styrene-divinylbenzene-butyl hydrogen
maleate copolymer.
- 88 -
~06S~z
1300 Parts of the finely divided sillca described
in Example 40 are dispersed, using the method described in
that Example, in 180 parts of styrene~ 20 parts of divinyl
benzene (as a 54% solution in ethylvinylbenzene), 340
parts o~ butyl hydrogen maleate and 9 parts of the copolymer
dispersant of Example 180 The properties of the dispersion
so obtained, containing 50X by volume of silic~ and of a
flaw-free, mouldPd sheet obtained by degassing and curing
the dispersion, are shown in Table VII.
~e~
The procedure of Example 51 is repeated, with the
addition of 5 parts of Y-methacryloxypropyl trimethoxysilane
and 1 part of water to the mixture just prior to the final
stage of dispersion at 1000 r.p.m. The properties of the
dispersion so obtaine~ again containing 50% by volume of
silica, and of the deriv d cured composite material are shown
in Table VII.
Comparative Example X
The procedure of Example 51 is repeated, but omitting
the copolymer dispersant. When only approximately 42% by
volume of silica has been incorporated, the dispersion is
found to be extremely viscous and cannot be moulded.
Table VII
, _ . ,, ~
. Properties of com~nosite
Example Type of Vlscoslty _
No. compositionOf fluid Modul~s Flex Impact
composition G~m Stren~th Stren~th
noise MNm-~ KJm~~
__ _ ~ ___ . , _ . ~
51 Dispersant 10 4.0 16~8 1.7
present
52 Dispersant + 10 2.0 13O5 2.8
interfacial
bonding agent
_ _ . . ._. __
- 89 -
~OS~53Z
Example 53
97Q Parts of calcium carbonate whiting No. 16, having
the following particle size distribution:-
Particles greater than 20 microns 17~ by weight
SPar~icles greater than 10 microns 30% by weight
Particles greater than S microns 53% by weight
Particles greater than 2 microns 72% by weight
are dispersed in 300 parts of methyl methacrylate containing
17 parts of the copolymer dispersant described in ~xample 18,
using the procedure described in Example 40. The resulting
dlspersion is fluid, having viscosities of (a) 124 poise
~spindle No. ~) and ~b) 31.5 poise (spindle No. 3). It can
be degassed and moulded into a composite sheet without
difficulty; the filler content is 55~4% by volume.
15Example 54
The procedure of Example 53 is repeated, with the
addition of S parts of m thacrylic acid after the calcium
carbonate is fully incorporated. This results in an increase
:
in fluidity of the dispersion, the viscosities being (a) 69 poise
(spindle No. 3) and (b) 13 poise (spindl~ No7 3)~ and in
easler degassing and moulding.
Comparative Example Y
The procedure of Example 53 is repeated~ but omitting
the copolymer dispersant. It is found possible to incorporate
only about 40~ by volume of the calcium carbonate, owing
to the high viscosity attained by the dispersion.
1600 Parts of the ~inely divided sil ica described
~: '
_ 90 --
~)6SS3Z
in Example 40 are dispersed, by the method described in that
Example~ in 500 parts of butyl acrylate~ 0~5 part of poly-
propyl~ne glycol dimethacrylate~ 3.5 parts of ~-methacryl-
oxypropyl trimethoxysilane, 0.7 part of water and 13 parts of
90~10 copolymer of butyl acrylate and dimethylaminoethyl
methacrylate as dispersant. A dispersion of viscosity
0.7 poise, containing 57.7% by volume of silica, is obtained,
which is easily degassed and moulded to form a sheet of
composite material.
~
This Example illustrates the production according
to the invention of a composite material in which the polymer
matrix is formed by the ring-opening addition polymerisation
of epoxide group-containing prepolymers.
40 Parts of "Epikote" 828 (Registered Trade Mark; a
diepoxide formed by the reaction of diphenylolpropane with
epichlorhydrin and marketed by Shell Chemical Co.) are mixed
with 60 parts of Epoxide No. 8 (a mixture of glycidyl ethers
of C12 14 monohydric alcohols, marketed by Proctor and Gamble)
and 5 parts of a dispersant as described below. 245 parts of
~-Crystobalite sand are dispersed in this mixture using a
Torrance Cavitation Disperser. The product is a fluid dispersion
~viscosity 24 poise)~containing 50% by volume of silica.
100 Parts of the dispersion are polymerised by the addition
of 3 parts of diethylene tetramine, giving a rigid, tough composite
material~
The dispersant used in this Example is prepared by
reacting 100 parts of "Epikote" 828 with 10 parts of
_ 91 --
- - ` 106~5~
p-nitrob~næoic acid in the presence of 1 part of dimethyl-
aminoethanol at 140-150~C for 30 minutes.
A similar dispersion, prepared by the above procedure
but omitting the dispersant, is much more viscous and consequently
S i~ more difficult to fabricate into a satisfactory composite
material.
- 92 _
