Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 39~
This invention relates to thermosetting compo-
sitions for molding fiber-reinforced articles, to the process
itself, and to the'novel articles obtained thereby.
Prior fiber-reinforced systems were generally
polyester-basedO While some great advances have been made in
such systems~ such as the low profile, low shrink system shown
in Kroekel, U. S. Patent 3,701~748~ such systems were generally
intended fo~ painted applications~ since exposure of the un-'
paillted cured composites to weather caused severe weathering
problems. '' ~
Other thermosetting resin systems than polyester-
' ' ''bas'ed comp'ositions'were known in prior art fiber-reinforcement
technology, for example Rieke et al., U.S. Patents 3,579,476 and
3,578,630; Pax, U.S. Patent 2,936,487; Squire, U.S. Pa~ent !l
2,899,402; British Patent 799,062;.Munn, U.S. Patents 3,362,942
and 3,154,600. These prior art thermosetting systems not based on
polyesters suffered from substan~ial shrinkage on curing causing
non-conformity with the mold, exposure and prominence of fiber-
reinforcement, and other problems.
.
It is an object of this invention to provide thermo-
setting systems for fiber-reinforced applications which do'not
substantially shrink when molded. A further object is to pro-
vide fiber-reinforced articles which are weatherable and can be
employed in non-painted applications A still further object is
.
~1~3~50
to provide systems and compositions for producing fiber-
reinforced articles having a smooth surface substantially
free of fiber prominence.
These, and other objects as will become apparent
from the following disclosure, are achieved by providing a
composition comprising an unsaturated monomer, a thermoplastic
polymer soluble in the unsaturated monomer, and a polyunsat-
urated crosslinking monomer, with the amount of the cross-
linking monomer being sufficient to cause the cured thermoset
resin molded from the composition to have an optically hetero-
geneous appearance due to foaming during cure, with the
density of the cured resin being significantly less than the
theoretical density if unfoamed.
- In accordance with the process of the invention, a
composition containing fiber reinforcement and particulate
filler is molded at elevated temperature under pressure, with
the composition set forth above~ under such conditions that
foaming takes place and shrinkage is substantially reduced.
The resultant novel articles are fiber-reinforced thermoset
- 20 moldings and are weatherable in some embodiments having sub-
stàntially smooth surfaces.
The present invention, in one aspect, resides in a
thermosettable composition comprising: (A~ from about 20%
to about 70~ by weight, based on said composition,
of an unsaturated monomer; from about 1~ to about 50%
by weight, based on said composition, of (B) a thermoplastic
polymer soluble in said unsaturated monomer; and
from about 10% to about 40% by weight~ based on said
composition, of (C) a polyunsaturated crosslinking
monomerj the amount of ~C) being sufficient to cause the
~ -3
",~
i ..,~
~3~
cured thermoset resin molded under heat and pressure from
said composition to have an optically heterogeneou~ appear-
ance due to foaming during cure, and a density significantly
less than the theoretical density if unfoamed. Articles
made from the aforesaid composition can be used without fin-
ishing or sanding steps and without the necessity of apply-
ing a protective coating.
In another aspect, this invention resides in a
process for preparing fiber-reinforced foamed thermoset
moldings comprising the steps of (1) preparing a composition
comprising fram about 20~ to about 70% by weight, based on
said composition, of (A) an unsaturated monomer; from about
1% to about 50~ by weight, based on said composition, of (B)
a thermoplastic polymer soluble in said unsaturated monomer;
from about 10~ to about 40% by weight, based on said composi~
tion, of (C) a polyunsaturated crosslinking monomer; and ~D)
a fibrous reinforcing agent selected from the class of
materials consisting of fiberglass, sisal fibers, asbestos
fibers, cotton fibers, nylon fibers, polyester fibers, poly-
propylene fibers, quartz fibers, beryllium fibers, boronfibers and carbon fi~ers; and then (2) zuring said composition
at a temperature ranging from about 200F to 350F and under
pressure in a mold; the amount of component (C) in said
composition being sufficient to cause foaming, substantial
reduction:of density below theoretical density, substantial
absence of shrinkage, and reduced fiber prominence.
The system of this invention is applicable to bulk
moldings compound (BMC) applications, sheet molding compound
-3a-
C
~3g~
(SMC) applications wherein a chemical thickener is employed to
~ause the composition to reach an appropriate viscosity before
molding, and to pre-mix and mat molding methods which do not
employ the chemical thickener procedure, and to other molding
procedures common to polyester technology. In the case of
SMC and BMC, the thermoplastic polymer employed should have
acid or anhydride functionality, as described in f~rther detail
later in this specification, but for pre-mix and wet mat molding
procedures, it is not required to have acid functional thermo-
plastic polymer.
With the latter methods, in addition to the resinsystem comprising the unsaturated monome~, thermoplastic polymer,
and crosslinking monomer, the moldable composition also includes
filler, fibrous reinfDrcement, free radical catalyst, mold
release agent, pigment, and any other desired additive. For SMC
and BMC applications, aspreviously mentioned, a chemical thick-
ener is further included.
Suitable unsaturated monomers for use in accordance
with this invention are alkyl esters of acrylic and methacrylic
acids having from 1 to 8 carbon atoms in the alcohol-derived
moiety, styrene and substituted styrenes, vinyl esters, and the
like, with optional minor amounts of unsaturated acids, anhydrides,-
esters, and half esters, amides, vinyl silanes, and the like.
Exemplary monomers include methyl methacrylate, methyl acrylate,
ethyl acrylate, vinyl acetate, ~-methyl styrene, and the like,
with optional minor amounts of acrylic acid, maleic anhydride,
monoethyl
103~3450
fumarate, acrylamide, and the like. While the amount most
suitable is dependent upon the particular monomer selected~
from about 20 to about 70~ by weight monomer based on the weight
of polymer, monomer, and crosslinking agent has been found to be
most useful. Mixtures of two or more monomers have been found
to be very suitable.
Suitable thermoplastic polymers~ which must be
:;
soluble in the monomer or monomer mixturej include polymers
derived from one or more of the folIowing monomers: Cl to C18
- 10 alkyl acrylates~ Cl to C18 alkyl methacrylates and ethacrylates~
~ styrene, substituted styrenes, vinyl esters, and acrylonitrile.
Polystyrene, polymethyl methacrylate, vinyl acetatejvinyl chloride
copolymers, cellulose esters such as cellulose acetate butyrate,
cellulose acetate propionate, styrene/acrylonitrile, methyl
methacrylate/ethyl acrylate~ saturated thermoplastic polyesters~
- polycaprolactone, and the like, are all suitable polymers~ with
. ~ ~ . .
ths preferred species being methyl methacrylate/ethylacrylate
for weatherable systems ? and-polystyrene for non-weatherable
systems.
The molecular weight of the thermoplastic polymers
can be from about 1,000 to 10,000,000. The structure of the
polymer can be essentially linear or can be extensively branched.
The preferred molecular weight range is 25,000 to 500,000; and
the most preferred range is about 70,000 to 2009000. Mixtures
--5--
.~ ,
~ 945C~
o~ thermoplastic polymers are suitable.
Suitable proportions of thermoplastic polymer are
from about l to about 50 percent by weight of the polymer,
monomer, and crosslinker composition, with the preferred pro-
5 portion being about 10 to about 30 percent, and the mostpreferred proportions being about 15 to 25 percentO
The components can be added in any order. It is
preferred to dissolve the thermoplastic polymer in the un-
saturated monomer prior to addition of the polyunsaturated
crosslinking monomer, but the three components can be mixed
simultaneously. The thermoplastic polymer can be in solid~
particulate form or in liquid form prior to addition It is
also possible to prepare the thermoplastic polymer in the
presence of the monomer.
For applications wherein chemical thickening is
employed it is necessary to provide acid or anhydride func-
tionality in the thermoplastic polymer. This is suitably
accomplished by incorporating in the monomer system used to
make the thermoplastic polymer an acid or anhydride functional
ethylenically unsaturated monomer ~hich is copolymerizable with
the other monomer or monomers.
The acid functionality may be carboxylic, phosphonic7
phosphoric~ sulfonic and the like. Typical acid and anhydride
--6--
I
; ~
~139450
functional monomers that are easily copolymerizable with the
comonomers of this invention include acrylic acid, methacrylic
acid, methacryloxyacetic acid, acryloxyacetic acid, meth-
acryloxypropionic acid, methylenemalonic acid, a-chloroacrylic
acida itaconic acid and anhydride, monomethyl itaconate, a-
methylene-a-methylglutaric acid, p-vinylbenzoic acid, ~-meth-
acryloxyethylphosphonic acid, a~methacryloxyethylphosphoric
acid~ ~-methacryloxyethylsulfonic acid9 ~-sulfa-toethyl meth~
acrylate~ and the like. Some~hat less reactive monomers during
copolymerization include ethacrylic acid, a-alkylacrylic acids~
crotonic acid, cinnamic acid, maleic acid and anhydride, fumaric
acid, a-cyanoacrylic acid, monovinyl succinic acid or anhydride~
a-carbomethoxyvinylphosphonic acid, p-vinylbenzenephosphonic
acid, a-carbomethoxyvinylphosphoric acid, p-vinylbenzenephosphor-
ous acid~ vinylsulfonic acid, a-carbomethoxyvinylsulfonic acid,
p vinylbenzenesulfonic ac~d, and the like. To one skilled in
the art thereare many additional acid and anhydride functional
monomers which may be used to prepare the acid or anhydride
functional polymer.
The level of acid or anhydride functionality in the
polymersuitable varies considerably depending upon the strength
of ths acid, the chemical thic~ener involved, the degree of
the thickening desired, the amount of the acid functional
polymer used~ and the general quality of the molded compound
--7--
~Q3945(~ j
desiredO The acid or anhydride containing monomer in the
thermoplastic polymer is preferably about 0.1 to 10% and more
preferably 0.5 to 5%~ An example of a preferred polymer is
the terpolymer of 85% methyl methacrylate, 12.5% ethyl acrylate~
and 2.5% acrylic acid.
Exemplary acid or anhydride functional thermoplastic
polymers useful in chemically thickening embodiments of the
present invention include the polymers of methyl methacrylate
and acrylic acid (MMA/AA)~ polymers Of methyl methacrylate and
the methacrylic acid (MMA/MAA), polymers of methyl methacrylate~ ¦
ethyl acrylate and acrylic acid (MMA/EA/AA)~ polymers of methyl
methacrylate, ethyl acrylate and methacrylic acid ~MMA/EA/MhA)~
polymers of methyl methacrylate~ butyl acrylate and acrylic acid
(MM~/BA/AA)~ polymers of styrene, acrylonitrile and acrylic acid
(S/AN/AA), polymers of styrene~ methyl methacrylate and acrylic
acid (S/MMA/AA)~ polymer of styrene, methyl methacrylate, and
maleic anhydride~ and tha likeO
Suitable polyunsaturated crosslinking monomers include
allyl acrylate~ allyl methacrylate, bisphenol-A.dimethacrylate,
1,3-butanediol dimethacrylate, 1,3-butanediol diacrylate, 1, 4
cyclohexanedimethyl dimethacrylate, diallyloxy compounds, al-
ethylene glycol diacrylate, diethylene glycol dime.thacrylate,
diisopropylene glycol dimethacrylate, divinyl benzene, divinyl-
oxymethane~ ethylene diacrylate~ ethylene dimethacrylate, ethyl-
~dene diacrylate~ ethylidene dimethacrylate~ 1~ 6~hexamethylene
.',,,; ' , .
lQ3~99L50
diacrylate~ hexamethylene dimethacrylate, neopentyl glycol
dimethacrylate~ tetraethylene glycol dimethacrylate 3 tetra--
methylene diacrylate9 tetramethylene dimethacrylate, tri-
ethylene glycol diacrylate~ triethylene glycol dimethacrylate,
l~ trimethylol ethane trimethacrylate, l,l,l-trimethylol
propane triacrylate, 1,1,1 trimethylol propane trimethacrylate,
vinyl allyloxyacetate, vinyl crotonate, vinyl methacrylate, and
the tetramethacrylate of pentaerythritol. The optimum amount of
crosslinking agent must be experimentally determined for each
system. The amount used must be sufficient to cause foaming
under the molding conditions to be employed, i.e., temperature,
pressure~ molding cycle timesO The expansion due to foaming
contributes to counteract the normal shrinkage due to poly-
merization and with certain of the preferred systems, a ne~-
ligible net shrink can be obtained. It has been found that the
foaming mechanism also contributes to the highly advantageous
reduction of fiber prominence achieved by the system of this
invention. The desired foaming effect can be determined by an
optically heterogeneous appearance in the neat cured resin. That
iS 7 if the resin system is molded nèat, without filler, fibers,
or pigment, the cured molding appears white and non-transparent.
The surface smoothness and weatherability of molded
parts allows articles to be used without any finishing or sanding
steps and without addition of protective coating~ Preferred
amounts of
.~ .
~394~5~
crosslinking monomers depend on the particular crosslinker-
thermoplastic polymer-monomer system to be employed. In all
acrylic systems such as trimethylolpropane trimethacrylate -
PMMA/EA-MMA~ suitable amounts of crosslinker are about 10 to
50 percent based on weight of the three components~ preferably
about 18 to 30% In styrene systems such as divinyl benzene-
polystyrene-styrene, useful amounts of crosslinker include about
!
10 to 40 perc~nt, preferably about 15 to 30 percent, based on l.
the weight of the three ~omponents.
The preferred molding temperatures are from about 200
to 3500F., with the most preferred range being about 230 to 3200F.
Th.e optimum temperature for a particular system depends on other
parameters such as the particular catalyst and components em-
ployed. The mold pressure should preferably be about 5 to ~,000
psi with the best results being obtained in a range of 200 to
2aO00 psi~The molding times are preferably about 30 seconds to
3 min~tes but, again, this is quite dependent on the other para-
meters o~ the system. The all acrylic systems appear to be best
in terms of weatherability and would be useful for making facia
panels, appliance housings, car bodies, laminating to plywood~
and other uses wherein weatherability is an advantage. Systems
of predominately styrenes and polystyrenes have been found not
to be very weatherable and these systems would mainly be useful
for molding articles for indoor uses.
--10-- .,
~3~5~
One suitable method for use in accordance with this
invention is to mix -the resin component, filler, pigment and
additives in a mixing device capable of dispersing the filler
and addltives. The resin paste is then mixed with the glass
fibers either by pouring onto a fiber glass mat or by adding
chopped glass to the mixing device. In the case of BMC or
premix systems, the compound may be stored for a period of time
before use. With SMC the resin paste is poured into the machine
~ and doctored onto a polyethylene film which is then compacted
- 10 with chopped glass fibers or glass mat. The SMC can be stored
~~ ' until ready for use~
~he suitable chemical thickeners are those commonly
. . .
usë~ ~n the artn Metal hydroxides and oxides are preferred
~~~ thickening agents, including, generally, oxides and hydroxides
- - 15 of metals in Groups I and II. Preferred are the oxides and
~~~ hydroxides of metals in Grou~ II. Most preferred are magnesium
oxide, mag-nesium hydroxide, and calcium ~ydroxide. The speed
and effectiveness of the thickening process vary considerably
~-- depending on the metal oxide or hydroxide. The amounts used
~eo depend on the desired viscosity at a given point in time, but in
general, 0~01 to 10%- by weight based on total resin components
is suitable, and 0.1 to 5~ preferred.
_ . .
The molding compositions generally contain a rein-
forcing agent in the form of fibrous materials, in particular
fiber glass. Other reinforcements may be used alone or in
--11--
B
,",_
~039~5~
combination with fiber glass to obtain special effects of
e~ther appearance or physical characteristics. Alternative re-
inforcements include sisal, asbestos, cotton~ organic synthetic
fibers such as nylon, polyester, polypropylene, and the like;
inorganic fibers such as quartz, beryllium, boron~ carbon fibers,
and the like. The form and the quantity of the reinforcing com-
ponents will vary greatly depending upon the physical character-
istics desired in the final molded part and the particular
production technique involved. For example, when fiber glass
is used in premix or bulk molding compounds~ chopped strand
fiber glass of approximately 1/8 to 3/4 inch in length is pre-
ferred. When fiber glass is used in sheet molding compounds,
-- chopped strands are preferred of approximately 3/4 to 3 inches in
length. In the case of sheet molding compounds the fiber glass
may be added in the form of a chopped strand mat bound together
~y a binder or, as is preferred, in the form of chopped contin-
uous filaments not bound into a mat. Other forms of reinforcement
may be used with the resin system of this invention such as
woven cloth or veil for special effects or increased strength
and reinforcement in certain areas of the part. In the premix,
BMC and SMC embodiments of the invention, the reinforcement
should be free to flow with the compound to the extremities of
the rnold. Thus the optimum length of the fiber and the exact
nature of the fiber is controlled by the process, and properties
-12-
~3~
required. In SMC and BMC systems, the glass fiber rainforcement
comprises about lO to 5O percen~ b~ weight of the resin~ filler~
and reinforcement, with 15 to 35 percent by weight being preferred~
Various types, grades and concentrations of fillers
and extenders are generally added to the molding composi~ion in
order to improve or change the physical characteristics and
other properties of the molding compound and/or the final cured
part. Fillers are used in quantities of from 1 to 80%, based
on the weight of the molding system or compound. The filler
content usually included in the molding compositions ranges from
about 50 to 300 weight percent, based on the weight of the resin
systemO Fillers useful with the resin system of the present
invention include clays, talcs, calcium carbonates, silicas,
calcium silicates, wood flour, phenolic microballoons, glass
beads and spheres, titanium dioxide, carbon blacks, and the like.
The use of alumina trihydrate as filler i~ preferred for
certain applications, especially where non-burning character-
istics or enhanced electrical properties are desired. The use
o calcium carbonate, aluminum silicate, or silica is preferred
for other applications due to its lower cost. The inclusion of
rel`a~ively large quantities of filler is generally useful to
obt~in the surface smoothness improvement, to reduce cost, and/or
to improve the flow and handling characteristics of both the
molding compounds before cure and the flow characteristics during
the molding and curing process, or to modify electrical and
mechanical properties.
.. . .. . .
-13-
~ 03~45(~
Other additives are necessar~ such as a free
radical catalyst to provide a rapid cure. The catalyst is
chosen to allow fillingof the mold before gelation and to
provide a fast cure after gelation. Choice of catalyst de-
pends in part on desired mold temperature. For example, tert-
butyl perbenzoate is preferred when the molding temperature is
in the range of 275 to 3250F, whereas t-but~l peroctoate is
preferred at 240o to 2750F~ However~ many other catalysts
can be used such as benzoyl peroxide, tert-butyl peroxide~
tert-butyl peroctoate~ di-tert-butyl peroctoate~ cyclohexanone
~peroxide, lauroyl peroxide, and the likeO Catalyst ratios are
from about 0.1 to about 3 percent~ preferably 0.5 to 2 percent~
based on weight of resin.
Also useful are free radical inhibitors to provide
suf~icient stability to the resin and the molding compound at
ambient temperatures. The inhibitors also help to provide a ¦
sufficient length of time for flow within the mold before gela-
tion. Such inhibitors include hydroquinone and its monomethyl ¦
ether~ p-benzoquinone, and the like. Also useful are release ¦
agents to provide fast and efficient release of the molded part
from the surface of the mold after cure. The release agents
may be applied as a spray on the mold or incorporated internally
in the bulk or sheet molding composition. Release agents which
may be used include lecithin and mixtures of phosphates such as
those marketed under the 'Zelec" trademark by E.I. duPont de
Nemours and Company. Also, calcium and zinc stearate are useful.
Suitable amounts are 0.1 to 2 percent based on weight of resin.
The use of the resin systems of this invention in
bulk and sheet molding compounds provides molding systems for
the operator and end user with graat advantages over conven-
tional polyester or other thermosetting systems. An advantage
-14-
,~
: ~ ~3
is the reduction of shrinkage which allows molding compo-
sitions to be used in applications w~ere- size and dimensions
are extremely critical. The molding compowlds are easily han~
dled and extrudedO Automatic handling equipment may be used to
prepare the compound and to place it in the mold. The compounds
show excellent flow characterists such t~hat they fill the detail
and extremities of the mold and move into the mold with great
~reedom. The resin system of this invention prov1des rapid
and full cure. During the molding process the shrinkage during
polymerization and cure is reducedO Metal reinforcements~ bush-
ings, and insertions may be molded in place during the moldingprocess. The molded parts prepared from the resin system of
this invention offer surface characteristics which substantially
duplicate the surface of the moldg whether the mold has a mirror
finish or a special pattern~ Upon removal of the cured part
from the mold there is essentially no warping thereby allowing
large parts to be prepared with great thickness variation
across the part. Large webs and reinforcing ribs may be in-
cluded in the molded part. The design freedom for the use of
reinforced plastics is greatly increased0 The physical proper-
ties of the molding compounds using the resin systems of thisinvention are excellent.
- Without departing-~rom ~he spirit or scope of this invention,
various alternatives and modifications w~11 be apparent to those
skilled in the art~ from the above disclosures and the follow-
ing examples which are indicated to illustrate a few embodiments
of the invention.
!
-15- I
~039~S(;lI
~XAMPLE I
This example illustrates a thermosettable system based
exclusively on acrylic components.
- 24 parts by weight of methyl methacrylate/ethyl
acrylate copolymer molding powder of the following monomer ratio
(MMA/EA:87/13) of molecular weight of 1.8 x 105 were dissolved
in 56 parts by weight methyl methacrylate, and to this solution
was added 20 parts by weight trimethylol propane trimethacrylateO
To the above composition was added 150 parts by weight
"Camel Wite'~ CaC03 filler, 0.5 part t-butyl peroctoate catalyst,
and 0.4 parts by weight "Zelec UN'~ release agent. ~ mat laminate
using two plies of Owens Corning M-8601 continuous strand glass
" fiber mat (2 ounces per square foot) and one ply 15 mil surfacing
mat Owens CorniI~g "Modiglas CFSM'~ wa~; molded at a gldss fiber
content of 30% by weight and thickness of 110 mils, at a pressure
f ~ psi and temperature of 2600F. for 3 minutes. The molding
had a smooth glossy surface~
EXAMPLE II
The following three examples show the reduction in
density of the polymers made from syrups having different cross-,
linker contents. 18 parts of a thermoplastic having the compo-
sition MMA/EA/MAA in a ratio 87/13/2.0 and 10 parts of trimethyl-
olpropane trimethacrylate crosslinking agent were dissolved in 72
parts of methyl methacrylate monomer. Into this resin system was
incorporated 0.5 part t-butyl peroctoate. The syrup was cured at
~16- ,
!
~a394so
a temperature 2600Fo and 400 psi, The resultant molding had
isolated areas of optically heterogeneity due to foaming and
had a density of 1.20 g/cc~
-16a-
1 0 ~ ~ ~ III '
A composition similar to Example II except that the
- amount of crosslinker was increased to 35 parts and 25 parts of-
the MMA were eliminated? was molded under the same conditions.
The resultant molding was completely op-tically heterogeneous and
had a density in grams per cubic centimeter of 1.07 as compared
with 1.20 of Example II.
- EXAMPLE IV
A composition similar to Example II except that ~50
parts of crosslinking agent based on weight of resin wa's ùsed~ '
was molded under the same conditions and resulted in a'density
of 1.03 with a completely heterogeneous appearance.
EXAMPLE V
' Twenty-three parts of the composition of Example II~
III and IV were mixed with 47 parts calcium carbonate filler,
30 parts glass fiber mat reinforcement and molded under the same
conditions to determine comparative surface smoothness or rough-
ness ~ue to absence of fiber prominence. The surface
- smoothnes's of the molded panel is determined with a Bendix Micro-
corder (Bendix Corp., Industrial Meterology Division). The
surface smoothness is the a~erage of four half-inch segments
along a two-inch traceO The average of the four traces con-
stitutes the required microinch reading for the entire panel.
The molding from the resin of Example II had a surface profile
f 338 microinches per 0 5 inches, Example III had a profile of
168 and Example IV had a profile of 138. This establishes that
increasing crosslinker content results in increased foaming and
smoother surfaces.
~17-
~(139~ a~ ,t
XAMPLEI VI
This example illustratjes the relationship between
the amount of crosslinking agent versus optical heterogeneity
and surface profile.
A composition havingthermoplastic polymer (MMA/EA/AA
at a ratio of 87/13/2.5), polyunsaturated crosslinking agent
(trimethylolpropane trimethacrylate) and monomer (MMA) in the
welght proportions shown in the following table were prepared.
The compositions also included 0.5% t-butylperoctoate catalyst.
Neat (without filler or fiber reinforcement) compositions were
molded under heat (2600F~) and pressure (400 psi) for three
\ minutes in a laboratory press betweell caul plates, to make
~"x4"xllO mil moldings, which were examined as to "degree of
~ whitening", i.e., the percent of the 4"x4l' sheet which was
~5 optically heterogeneous. The same compositions were mixed with
glass fiber and CaC03 filler in a weight ratio of 28 resin:
30 glass: ~2 filler and 0.2% mold release agent, based on
weight of resin and filler, and molded at 2600F. and 400 psi
for three minutes in a press using polished matched metal die
molds to make 12"x12"x80 mil moldings~ which were scanned as
to surface profile using a Bendix Microcorder, and the micro-
inches of waviness per 0.5 inch determined.
LnO
~_ .. . ... .. ".. . ... ...
" ', ~ A ~
E~
E~
H Z ~ 3Y~450
c~ ~ c~ ,1 ~ r~
~ C-
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H I .
O ~)
P~
~ql ~1 . .
CQ ~ .
~ ~ ~ ~ O
H ~) ,1 O~ ~
~ V~
F~
.. ' E~
C~
C' ~O
~,
~.
H
H ~ ~ O ~ O
U~ ¢ . ~ ~ ,
V.
H
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¢~
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--19 -
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lQ39450
EXAMPLE VII
_ .
This example establishes the necessity of both poly-
unsakurated crossli~king agent and thermoplastic polymer.
A resin composition having 18 parts of the thermo-
plastic polymer and 82 parts of the monomer used in Example
VI was molded in the same manner to determine degree of whitening.
The molding was entirely clear, indicating that no foaming took
place. The composition had no crosslinking agent, and it did
not thermoset. The surface profile of the composite was 1455
microinches/0.5 inch.
A composition having 20 parts trimethylolpropane
trimethacrylate crosslinking agent and 80 parts MMA monomer
used in Example VI was also molded neat to determine degree
of foam whitening. It was clear, indicating lack of foaming.
The mat laminate prepared from this composition using the pro-
cedure of Example VI had a surface profile of 768 ~-in./0.5
~~~ inch. Mold scumming was observed.
The following ten Examples illustrate several alter-
native compositions suitable in accordance with the invention.
In all cases~ the compositions contained 0 2 percent
based on weight of resin of mold release agent,`and 005%, based
on weight of resin, of t-butylperoctoate as catalyst~ two mats
of continuous strand glass fibers, CaC03 filler, were molded on
a laboratory press at 2600F~ and ~00 psi for three minutes to
form 12"x12"x125 mils sheets which were examined for linear
shrinkage~ ~aviness of surface, 600 gloss (ASTM Procedure No.
D-563-62T) and colorability. Weight ratio of resin to glass
to filler was 28:30:420
-2~-
l ~
~L~9~50
I
. ..
EXAMPLE ~TIII
MMA monomer, 87MMA/13EA/2.5~ thermoplastic polymer
having an average molecular welght of 1.3 x 105, and divinyl-
5 benzene ( 52% active) crosslinking agent in the weight ratioof 53:27:10 were molded~ and had a shrinkage of 0.95 mils
- per inch, profile of 448 microinches of waviness per 0. 5
inch, and a 600 gloss of 61. 5%.
EXAMPLE IX
MMA monomer, 87MMA/13EA/2.5L4 thermoplastic polymer~
and 20 trimethylol propane trimethacrylate in the weight ratio
of 56:2L~:20 had 1.00 mils/inch shrinkage, profile of 242
microinches/0.5 inch, and a 600 gloss of 77.7%.
\ EXAMPLE X
MMA monomer, the same thermoplastic polymer as in
Example VIII, and neopentyl glycol dimethacrylate crosslinking
agent in a weight ratio o~ 56:24:20 had mold shrinkage of 1.66
profile of 43 5 microinches/0.5 in.~ and a gloss of 69.6%~
EXAMPLE XI
MMA monomer, the thermoplastic polyrner used in
Example XIII, and 1,3-butanediol dimet~crylate crosslinking,
;- monomer in the ratio of 56:24:20 gave a composite with a
shrinkage of 1.19 mils/in., surface profile of 5205 and gloss
of 64.6%.
EXAMPLE XII
MMA monomer~ 87MMA/13EA thermoplastic polymer having
a molecular weight of 1.9 x 105, and trimethylolpropane tri-
methacrylate crosslinking monomer at 56:24:20 weight ratio
ga~re shrinkage, surface profile, and gloss of 0.97, 234, and
30 72.2% respectively.
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~03~4S0
EXAMPLE XIII
MMA monomer, 87MMA/13EA/2.OMAA having an average
molecular weight of l.G x 105 thermoplastic polymer, and
trimethylolpropane trimethacrylate in a weight ratio of
56:24:20 had shrinkage, surface profile, and gloss values of
1~15~ 2~, and 72.1~, respectively.
EXAMPLE XIV
MMA monomer, polystyrene having a molecular weight
of about 100~000 thermoplastic polymer~ and the crosslinking
monomer of Example IX, in the weight ratio of 56:24:20, had
a shrinkage of 0.~8~ profile of 228~ and gloss of 80.1%.
- EXAMPLE XV
MMA monomer~ cellulose acetate butyrate thermo-
plastic polymer (Eastman "O. 5 sec")~ and the crosslinker used
~` 15 in Example IX, in a weight ratio of 56:24:20, yielded a molding
. having shrinkage of 1.12, surface profile of 294, and gloss
of 71.4%.
EXAMPLE XVI
Mixture of 48 weight parts MMA and 8 weight parts
a-methyl styrene as monomer, 24 weight parts of ~he thermo-
plastic polymer used in Example VIII, and 20 weight parts o~
the crosslinker used in Example IX yielded a molding with
shrinkage of o.35, surface profile of 244, and gloss of 58.2%.
EXAMPLE XVII
Monomer mixture of 12 weight parts vinyl acetate
and 44 weight parts MMA~ 24 weight parts of the thermoplastic
polymer used in Example VIII, and 20 weight parts of the cr
linker used in Example IX, yielded a composite molding with
a shrinkage of o.46~ surface profile of 204, and a gloss o~
70 ~.
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I
~L~394S~) ~
EXAMPLE XVIII
This example demonstrates the excellent weather-
I ability achievable from a composition made in accordance with
the lnvention. "600 gloss" after the number of ~ rs exposure
to a Sunshine Carbon Arc weathering machine was measured,
as was the color and degree of fiber prominence after 1006
hours. The weight ratio of resin:CaC03 filler:glass fibers
~ was 28:42:30. The resin composition was MMA monomer, MMA/EA
; 10 thermoplastic polymer (monomer ratio of 87/13)having an aver-
age molecular weight of 1.9 x 105~ and trimethylol propane
trimethacrylate crosslinker in the weight ratio 57.1:26.1:
16.5. After O hours~ the gloss was 80.3; after 243 hours
75.7; after 496 hours, 72.8; after 1006 hours, 66.3. Color
after 1006 hours was lF (i.e., on a scale of OF for no fading
to 5F for maximum fading wherein the color disappears~.
EXAMPLE XIX
This example is an embodiment showing composites
with low shrinkage made by using an all styrene resin.
.. . .
A resin of 60 parts styrene~ 25 parts polystyrene
of molecular weight of about 100~000~-and 15 parts divinyl-
benzene is mixed with l-part t-butylperbenzoate~ 0.50 parts
"Zelec UN",¦ 0.75 parts chrome oxide pigment, and 60 parts
calcium carbonate filler. The above paste is poured onto
30 parts Or doubIe ply glass strand mat (2 ounces per square
foot) with 2 plies of surfacing mat and molded at 3000F. and
~00 psi for 3 minutes.
~he resultant composite has a low surface proflle
and shrinlcage.
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.
EXAMPLE XX
This exampl0 illustrates one sheet molding compound
(SMC) embodiment.
A resin composition of 64 parts MMA monomer, 18
parts of MMA/EA/AA copolymer (87/13/2.5~ having a molecular
weight of about 1.3 x 105 and 18 parts of trimethylol propane
trimethacrylate was mixed with 8i parts of calc;ium carbonate
filler, 0.5 parts t-butylpero~toate, 0.5 parts "Zelec NE"* release
agent, 0.2 parts of "Maglite~S" magnesium oxide thickening
agent~ and 2.0 parts of titanium dioxide pigments. The initial
Brookfield viscositylof the paste was 50~000 cps; the viscosity2
of a portion of the paste not used for SMC was ll x 106 cps.
after five days. The paste was immediately placed in the
SMC machine and mixed with 1 inch chopped glass fibers so
that the final composition of the SMC was resin:filler:glass =
23:47:30. m e SMC was molded after ~8 hours at a viscosity
of 9.6 x 106 cps. at ~00 psi, 2700F., for three minutes. The
molded part had a surface waviness of 222 microinches per 0.5
inch, a shrinkage of 1.53 mils per inch and a 600 gloss of
83.5%.
EXAMPLE XXI
This example shows the optical heterogeneity being
obtained in another system. A mixture of 56 parts by weight
vinyl acetate, 24 parts by weight of polystyrene, and 20 parts
by weight diallylmaleate was molded under the same conditions
as ln Example II and resulted in a molding which was completely
optically heterogeneous.
1 - No. 6 spindle at 10 RPM
2 - T-F spindle at 1 RPM~ helipath
* Trademark -24-
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