Note: Descriptions are shown in the official language in which they were submitted.
- 2 - 1~ 4 8 ~7 6
The present invention relates to resin compositions and
the cured produc~s obtainable therefrom.
British Patent Speci~ication No. 115020~ describes the
production of resins having repeating units of the formula
; - CH2 - R - CH2 - Ar -
1 (C~2ArOH)n OH
wherein R is an aromatic hydrocarbon or aromatic hydrocarbon-
oxy-aromatic hydrocarbon group, which optionally has inert
; substituents and Ar is the residue o~ a phenolic compound here-
; inafter defined and n is O or 1. British Patent Specification
No. 1305551 describes the curing of these resins with epoxides
havinig 2 or more epoxy groups per molecule to form cured pro-
ducts.
The above resins can be used for the production of sur~ace
coatings and laminates having good chemical and high temperature
ageing resistance and electrical properties.
15The coatlngs are prepared by dissolvlng the resin and a
sultable curlng agent e.g. hexamethylene tetramine as in British
Patent 1150203 or the epoxides as in British Patent 1~05551
in an organic solvent e.g. 2 - ethoxy ethanol or methyl isobutyl
ketone, applying the solution to the sur~ace to be coated,
evaporating the solvent and then curing the resultant coating
; to an infuslble product. I~ the coating ls to be used at a
high temperature or if particular propertles are requlred of it,
post curing e.g. at 160 - 250C may also be needed. We have
found that the above resins tend to produce cured surface coat-
ings showing ~Iclssingfl. Ciising is a well known surface coating
phenomenon (see e.g. 'Palnt ~llm Defects' Manfred Hess, pub- -~
lished by Chapr.lan and Hall 2nd edltion 1955J p.436) and is
associated wlth non-wettlng of the surface beln~ coated.
; Normally the resln laminates are prepared ~ia i~p~gnatiQn o~
glass cloth, or carbon fibre or asbestos cloth with a solutio~
of the resln ln an organic solvent e.g. methyl ethyl ketone.
Such laminates exhibit a wide range o~ utility. However, for
certain appllcations lt may be desirable to incorporate
additlonal materlals in the laminate, for example poly tetra-
~luoroethylene or certain flame retardent materials, the latterespecially for epoxy curing agents. Hltherto, it has not been
~ound possible to produce completely satis~actory laminates
~rom resins incorporatlng such additional materials.
The above resins can also be used as adhesives but the ad-
heslve strength of the cured resin is not very high because on
curing blisters are ~ormed.
,. `3~ '
- ~ . : -
: ` `
~ 8~76
; - The present invention provides a resin composition
which comprises
. (a) a resin having repeating units of the formula
2~ n
.. and preferably consists essentially of such repeating units,
wherein Rl is a divalent or trivalent aromatic hydrocarbyl or
divalent or trivalent aromatic hydrocarbyl-oxy-aromatic hydro-
carbyl group, or inertly substituted derivatives thereof, and
,. 10 Ar is a residue formed by removal of 2 nuclear hydrogen atoms
from a phenolic compound having 1-3 hydroxyl groups and at
least 2 nuclear hydrogen atoms, and n is O or 1, and
; (b) an uncured or partially cured condensate of formaldehyde
,.;,
s.~ and melamine, the weight ratio of resin to condensate being
i 99:1 to 1:99.
~ The resin composition may also contain 0.5 to 100%
. by weight (based on the weight of the resin) of an inorganic
. dispersing agent having at least one dimension less than
. 100 mu and all dimensions less than 15u and stable to 150C.
;...... 20 The resin compositions of the invention may also
contain a particulate material of particle size 0.2,u - 2 mm,
~i- preferably 1~ - 1 mm, and stable to 150C which is preferably
s at least one of a flame retardent, lubricant,
... .
,. . .. .
; .
... .
',~ ,
.; - 3 -
. . .
, .
. ~ .
l E
.,
1~41~ 76
metal powder, and formaldehyde condensate with a nitrogen-
ous compound (as hereinafter described).
We have found that the composition comprising resin
and as dispersing agent finely divided silica of particle
size 1 - 80 m,u, can be used with the curing agent to prepare
a coating solution, which after application, evaporation
` of solvent and heating/curing, produces a coated layer in
which the problem of cissing is greatly reduced if not elimin-
ated. If desired the composition may also contain the
particulate material.
The compositions of the invention comprising resin, the
dispersing agent and curing agent and optionally the parti-
culate material can be cured with decreased production of
.
blisters in the cases when volatile materials are produced
on curing e.g. with haxamethylene tetramine and thus can be
used as adhesives with high adhesive strength.
"t The amount of inorganic dispersing agent is usually
`~ !
0.5 - 20% (by weight based on the weight of the resin) when
the resin composition is to be used for producing coatings
; 20 showing reduced cissing or for adhesives showing the cured
~ form reduced blistering, preferred amounts being 1 - 10%
i in both cases. When the resin composition also contains the
particulate materials, an amount of 0.5 - 100~ (based on
the weight of resin) of dispersing agent is used, the higher
values being appropriate when the dispersion of resin,
dispersing agent and particulate material is to be used as
a "masterbatch" for subsequent dilution with further resin
solution; amounts of dispersing agent in the region 1 - 20%
are preferred when the resin dispersion is to be used as
such.
The amount of particulate material in the resin compo-
: sition i~ usually 1 - 100% (by weight of resin), the higher
' .:
;
;-- ~ - 4 -
. ~
. .
~: - .' .'. :
~`
~;~)4~3~76 :
values again being used when the composition is to be used
, . I
as a masterbatch for subsequent dilution with more resin
solution. Amounts of particulate material in the range
1 - 30% are suitable for dispersions to be used as such, the
r.' preferred upper limit being dependent on the nature of the
particulate material. The usual amounts of antimony oxide,
chlorine and/or phosphorus containing organic flame retard-
; ants and metal powders are respectively 5%, 10% and 25~.
, In the dispersions of the invention comprising resin,
dispersing agents and particulate material (optionally with -
curing agent) the amount of dispersing agent depends on the
~; nature and amount of the solvent and particulate material
and on the degree of dispersion required.
The inorganic dispersing agent, which is stable to at
least 150C, preferably to at least 200C, usually has a
minimum dimension of at least lm~u. It is preferably finely
i~ divided silica of average particle size 3 - 80m,u especially
X. .. - ..
7 - 40m,u, e.g., the fumed colloidal silica sold under the
.
i trade marks "AEROSIL" and "CAB-O-SIL", finely divided
;' 20 chrysotile asbestos e.g. of diameter about 25mp and length
5 to 10 ,u such as that sold under the trade mark "SYLODEX"
which may optionally be mixed with silica, and finely
; divided hydrous magnesium aluminium silicates e.g. organic
derivatives of mont-morillonite with a platelike structure
of thickness 2 to 4m,u and maximum dimension 0.5 to l~, such
as that sold under the trade name "BENTONE".
Examples of the flame retardants are organic compounds
containing halogen and/or phosphorus atoms such as poly- -
halogenated organic compounds, preferably those in which
the halogen is
.,:,
i~:
, ;
.... . .
~ 5 -
,',"., ~.
..... .. . .
chlorine or bromine, and especially those in which the organic
nucleus is an aromatic nucleus, e.g. decachlorobiphenyl, hexa-
bromobenzene, hexachlorobenzene and tetrabromobisphenol A, and
tris (bromopropyl) phosphate, tris (pentabromophenyl) phosphate
and tris (dichloropropyl) phosphate. These compounds, which
may be soluble in the resin solution, are used in con~unction
; with antimony o~ide, which is insoluble. Other flame retardants
are metal borates e.g. borates of metals of Gp. 2 (of the
Periodic Table published in Bull. Soc. Chim France January 1966 ?
such as zinc, calcium or barium. Antimony oxide may also be
present in admixture with the borates.
The lubrlcant particulate materials may be homo polymers of
tetrafluoroethylene (PTFE) and copolymers thereof with other
fluorinated olefins of 3-6 carbon atoms e.g. perfluoropropylene,
or may be inorganic in nature, such as graphite~ molybdenum di
sulphide or metal salts of fatty acids of 8-20 carbon atoms, e.g.
; stearic acid, zinc and calcium stearates being preferred. In-
corporation of the lubricant in the resin composition enables
cured products e.g. bearings having a low coefficient of fric-
; 20 tion to be obtained.
- The metal powder, that may also be the particulate material, ~-- may be aluminium powder or zinc dust. Metal powders are
generally used when the resin, dispersing agen~ and metal
; powder is for use in surface coating applications, but could be
used for producing laminates.
The particulate material can also be a formaldehyde condensate
formed frrom f~r~alqehyde (or a compound yielding it in situ such
. . , p a~^aJDr~n~/a~ ~C
D as poraformaldch~ or hexamine) and a nitrogenous compound
Z Y
containing a N = C - NX2 group (or a group enolisable to said
:. Z O
group such as a - N - C - NH2 group), wherein Y represents an
oxygen, sulphur or nitrogen atom, and Z represents a hydrogen,
carbon or oxygen atom or Y and Z together form a direct bond.
Preferably the nitrogenous compound contains at least 2 - NH2
: groups and preferably has 1-6J especially 1-~ carbon atoms.
~5 Examples of the nitrogenous compound are urea, melamine, thio
;~ urea, cyanamide, dlcyandiamide and guanidine. Such condensates
;~ which may be in the cured, partially cured or uncured form are
well known and are described in, for example "Aminoplastics"
by C.P. Vale, published Cleaverhulme Press, London 1950. The
preparation of the uncured condensates is described further
below. The addition of these formaldehyde condensates to the
resin compositions improves the electrical properties of the
cured product.
. . .
48~76
The resin is preferably prepared, following the general
proce~ure described in British patent specification No. 1150203,
by reacting (1) an aralkyl ether of the general formula R'
` (-CH2OR)a and/or an aralkyl halide of the general formula R'
(CH2X)a, wherein R' is a divalent or trivalent aromatic
hydrocarbyl or aromatic hydro-carbyloxy aromatic hydrocarbyl
radical,R' optionally containing inert substituents in the
aromatic nucleus, R is an alkyl radical containing 1-5 carbon
;~ atoms, X is chlorine, bromine or iodine and _ has a value of ~ -
2 or 3 with (2) a molar excess, normally of at least 1.3:1,
preferably in the range of 1.4:1 to 2.5:1 of a phenolic compound
or a phenolic compound and a non phenolic compound containing
an aromatic nucleus. If a is 3 then n is 1 and a further ArOH
. ~ group may be bonded to R' through another methylene bridge.
. In these general formulae R' represents any divalent or
i........... trivalent aromatic hydrocarbyl or aromatic hydrocarbyloxy
.il aromatic hydrocarbyl radical, for example the m - or p-phenylene
. radical, the diphenylene radical, the diphenylene oxide radical
";
,,~ ~0~,
:~ ~ ' - -
the radical
' or the radical
.....
:.,
~ 7 -
,
:.: -
.. . .
`':
,.,
1~41~76
` Thus both mono nuclear, and fused and unfused di-and poly
nuclear radicals may be represented by R', though mononuclear
`` radicals are preferred because the cured products therefrom
~ have higher strength at high temperatures than those from di
.` and polynuclear radicals. Preferably R' does not represent a -
diphenylene or diphenylene oxide radical when the aralkyl halide
is used to prepare the resin. The resin is preferably pre-
pared from the aralkyl ether, especially ones in which R is an
alkyl radical of less than 4 carbon atoms e.g. a methyl radical.
The preferred compounds for a reaction with the phenolic com-
` pounds are those in which a has a value 2, particularly the
p-xylylene dihalides for example p-xylylene dichloride and the
,~ p-xylylene dialkyl ethers for example p-xylylene - glycoldi -
`~'` methylether.
,..;~
... .
,.. '; ~ .
' . ~
,,',, :-'
~. ~
.: ~
;~.,. , ~.
.. . .
", ~,
'',i,~ ''' :
:~
~... I
,., ~ . ~
.,.,.
~:.,,. . : .
. .
. - 7a -
: ~.
.,?, . :
:,''';
: .,;
~ E
, . .
.: ,.
4iY~76
.~
If desired the Rl radical may contain substituents, for
; example methyl radicals, attached to the aromatic nucleus,
,`; provided the said substituents are inert under the conditions
of the reaction. In fact the presence of chlorine or fluorine
atoms in some or all of the available positions in the aroma-
tic nucleus has been found advantageous in that it leads to
improved flame resistance in the resulting polymeric products~
Examples of such substituted aralkyl ethers and aralkyl halides,
which may be employed according to this invention, are 2,3,5,6 -
tetrachloro - 1,4 - di(chloromethyl) benzene and 2,~,5~6 -
tetrachloro - l,4 - di(methoxy-methyl) - benzene.
~` The phenolic compound includes any compound or mixture of
;~` compounds derived from benzene and containing l to 3, preferably
l or 2, hydroxyl radicals ~oined to the aromatic nucleus, there
being a total of not more than ~ substituents attached to ring
carbon atoms of the benzene nucleus apart from the one essen-
tial hydroxyl group. Thus the phenolic compounds may be of
formula OH
,........................ .
~ (R3)1 _ 3 .
where each R~ is hydrogen, hydroxyl, amino, alkyl of 1 to 8
carbon atoms, e.g. methyl, ethyl, isopropyl, tert, butyl or
tert. octyl, phenyl and hydroxyphenyl alkyl e.g. hydroxy
phenyl - methylene, - ethylene and - isopropylidene. Examples
of these phenolic compounds are phenol, p - cresol, m - cresol,
; resorcinol, catechol, 4-methyloatechol, isopropyl catechol,
diphenylol propane (bis 2,2- (4-hydroxy phenyl) propane),
; diphenylolethane, monoalkyl phenols such as p-ethylphenol,
p-tert. butyl phenol and p-tert. octyl phenol, m - and p -
phenyl phenol p - amino phenol, pyrogallol and phloroglucinol.
, Mixtures of the phenols can be used such as a monophenol with
, .
a dihydric phenol e.g. resorcinol with phenol itself, or mix-
tures of diphenols e.g. 4-methyl catechol and catechol and/or
resorcinol such as that sold as a phenolic coal tar fraction.
Examples of the compound containing aromatic nuclei which
may be mixed with the phenolic compound in the formation of the
resin are dlphenyl - or dibenzyl - etherJ terphenyl, diphenyl-
~`i amine, diphenyl sulphide diphenyl, anthracene, diphenylsulphone,
;~ triphenyl phosphate, octaphenylcyclotetrasiloxane, aryl sub~
stituted borazoles and metal complexes such as ferrocene.
The proportion of aromatic compound can vary within wide limits
but i~ not sufficient to prevent satisfactory curlng of the
''.,
:
. ' .
` ` 1~48~7~
reaction product with the hardening agent. Further details of
the aromatic compound and its modes of use in the reaction of
- phenol and dihalide or diether are given in British Patent
Specification No. 1150203.
The curing agent is a condensate of formaldehyde with
melamine in the uncured or partly cured form. The condensates
- are preferably made by reaction of one molar proportion of ~-~
; melamine with 1-10 molar proportions of formaldehyde (or
formaldehyde yielding compound), especially 1:2 to 1:8 molar
proportions, in neutral or alkaline conditions. The amount of
curing agent needed for reaction with the resin in general
depends on the nature of the curing agent, in particular on the
number of free methylol groups on it and also the degree of
curing desired. Thus less hexamethylol-melamine will generally
be needed than trimethylolmelamine for equivalent curing. The
resin is mixed with the formaldehyde condensate in a weight ratio
of 1 - 99 : 99 - 1, preferably 50 - 95 : 50 - 5 and especially ;
, 65 - 85 : 35 - 15.
,.. ; .
The formaldehyde condensate in its uncured or partially
` 20 cured forms is used as a curing agent whether or not an
i inorganic dispersing agent is also present. When the comp-
`~ osition comprising resin (a) and condensate as curing agent
is to be used as a moulding powder, the components can be dry
mixed, formed into a moulding powder and subsequently moulded
:,. -
"
;' :
. .
, / .
`',
., I
l E
-- lo - lV48~76
under heat and pressure to rorm cured moulded articles. When
the composition comprising resin (a) and condensate as curing
agent is to be used ~or coating purposes or for impregnation
in the production of laminates, it is preferred, but not
essential, to incorporate the inorganic dispersing agent as
well so that the liquid dispersion used for coating or dis-
` persion may be as uni~orm as possible. The conditions for
curing are the same as for hexamine curing. The use of the
condensates or the nitrogenous compounds as curing agents en~
ables cured products with good electrical properties especially
high arc and tracking resistance, and high heat resistance to
be obtained.
The compositions of this invention may also contain in-
organic fillers, e.g. asbestos flour, mica or chopped glass
strands. The inorganic filler and resin will normally be
present in a weight ratio of o.o5 r 1 to 4.0 : 1. Other in-
gredients such as pigments, accelerators, and antistaining
agents e.g. magnesium oxide, or titanium dloxide may also be
present if desired.
- 20 The compositions of the ~nvention can be made by mixing
the various components in any order, but it is convenien~ to
add the curing agent last. me mixing can be carried out in
any convenient method such as dry blending to form a powder
for moulding (optionally with subsequent addition of organic
solvent to make the desired liquid ~or coating and impreg-
natlng purposes) or blending in solutions in an organic solvent
to prepare the liquid directly. The solvent may be a dialkyl
ketone o~ 3-8 carbon atoms e.g. methyl isobutyl ketone, methyl
~, ethyl ketone, or methylisoamyl ketone, isophorone, diacetone
i': 30 alcohol,a cycloalkyl ketone of 5-7 carbon atoms e.g. cyclo-
hexanone, an alkoxy alkanol with 1-6 carbon atoms in the
alkoxy group and 2-7 carbon atoms ln the alkanol group such
as 2 - ethoxyethanol, alkyl ethers thereof with 1-6 carbon
atoms in the alkyl group e.g. the methyl ether,esters o~ the
~5 alkoxy alkanols with alkanoic acids of 2-6 carbon atoms e.g.
the acetate, any Or whlch solvents can be (in an amount suf-
ricient to maintain the resin in solution) mixed with an
` aromatic hydrocarbon preferably a monocyclic one of 6-12
carbon atoms such as benzene, toluene or xylene or an aliphatic
~; 40 hydrocarbon such as white spirit or solvent naphtha or an
al~anol e.g. o~ 1 to 6 carbon atomsJ such as methanol, ethanol
- or n - butanol. me resin is usually present in the organi~
solvent solutions in an amount o~ 5 - 90~ preferably 20 - 65
e.g. 20 - 50~ by weight. The mixing can be carried out at a
4~76
low temperature e.g. 20 - ~0C and ~he mixture stored until
required, but the mixing of the curing agent with the remainder
of the components is usually carried out at a higher tempera-
ture e.g. about 60 C for several hours e.g. 1 - 4 hrs. and
then the mixture cooled to room temperature and stored until
required.
The liquid dispersed mixture of resin, dlspersing agent (if
present), particulate material (if present), solvent and curing
agent (and other additives if present) can be used as a coating
solution or as an lmpregnant for the production of laminates.
me solvent from the liquid dispersed mixture can also be
evaporated and the residual product used as a moulding
powder; this technique ls pre~erred for the production of
moulding powders containing long fibres, which may be broken
in the dry mixing method.
The compositions of the invention are cured by heating
usually at above 70C and preferably over 100C e.g. 150 -
;~ 175C. Post curing if needed is usually carried out at 160 C -
250C. The time needed for post-curing varies according to the
properties of the desired product, and the temperature of use
; of that product.
For the use of the compositions of the invention for
coating, the mixture of resin9 dispersing agent (if present),
curing agent and solvent (together with any other additives)
can be applied by any means to the surface to be coated e.g.
by painting, spraying or lmmersion. Normally the surface will
be of metal e.g. ~errous metal such as mlld steel but other
substrates suoh as wood, plastic material or inorganic mater-
, ials such as porcelain or cement can be coated, if desired.
~0 After coating the solvent is evaporated and the layer cured.
~hen the dispersing agent is finely divided silica, the curqd
layer shows little or no "cissing'.
i In the use of the compoæitions of the invention as adhesives
the mixture of resin, dispersing agent, curing agent and sol-
vent, (together with any other additives) can be applied to
one or both of the surfaces to be adhered together by any
means e.g. painting, spraying or immersion. Examples of
suitable surfaces are those of metals e.g. ferrous metal such
as mild ~teel but other substrates such as plastics materials
e.g. those described in British Patent 115020~, optionally
with reinforcement e.g. glass or asbestos fibres, or inorganic
materials such as porcelain or cement can be used. After the
applications, the solvent is evaporated, the surfaces brought
together and the combination of surfaces and intervening layer
.,,
''
.
,, : ' ~ '
.
1~ 8~
cured. Because of the reduction in the number and/or size
of blisters produced, the bond formed by the combination has
high strength.
In the use of the compositions of the invention for
making laminates, the liquid mixture is applied to the
laminate base. Suitable laminate bases are glass cloth or
carbon ~ibre agglomerates although other fibrous materials
such as asbestos cloth may also be employed if desired.
Such materials are impregnated with the dispersed mixture as
described above and then dried. Typically the fibrous base
is passed through a bath of the resin dispersion.
The fibrous material into which the resin has been
, . .
impregnated is then subjected to a precure heat treatment
at about 140C~ often for about 10 minutes. The laminates
are then pressed at a tempPrature above 160C often in the
range 170 to 190C at a pressure of from 7 to 105 kg/cm2,
although pressures above 35 kgjcm2, often of about 70 kg/cm2
are normally employed. Normally pressing will be carried
out for a period of at least 1/2 hour, often for about an
^ 20 hour, depending upon the conditions of temperature and
pressure employed.
; For optimum results the laminates are subsequently
,.
post cured. The temperature and time employed for the pos-t
cure operations are dependent upon each other. For example
a post cure in the temperature range 140 - 190 C may take
;~ up to 7 hours whereas one in the range 220 - 250 C may be
accomplished in five hours. However, it is normally
desirable that the material is heated to a temperature at
least in the range 190C - 220C.
- 12 -
. .
.
,'
''~ '
lV4~76
, The invention is illustrated in the following Examples:
Example I
Resin A
An aralkylene phenol resin was made by reacting 705g
(7.5 moles) of phenol and 830g (5 moles) of p-xylylene
dimethyl ether (technical grade) in the presence of lml. of
diethyl sulphate as catalyst. On heating to 130 - 200C
methanol was lib~rated and distilled out. The product on
'; cooling, was a red brown solid having a softening point of
,~ 10 97& . -
Resin B
126g (1 mole) of melamine and 225mls (3 moles) of a
40% formalin solution were mixed together and a few drops
:~ of dilute sodium hydroxide were added to make the mixture
.
slightly alkaline. The resultant solution was heated to
~ 75& with stirring and on cooling a white pre~ipitate was
`;~ formed. This was filtered off and dried-to obtain a white
powder, trimethylol melamine nominally.
Resin C
7.5gms of resin A were mixed th~roughly in a powdered
state with 2.5gms of resin B. The mixture was put into an
aluminium dish and placed in an oven at 200C. A hard
infusible, insoluble mass was formed.
240gms of resin A were dissolved in a mixture of 240gms
.. . . . . .
of ethyl methyl ketone and 80g of industrial methylated
.:: . .
spirits. To this solution was added 80gms of resin B and
... .
6gms of fumed silica and these were dispersed using a high
speed mixer. The resultant mixture was used to impregnate
glasscloth "MARGLASS" (trade mark) 116T/P705 and the pre-
preg produced was precured for 10 minutes at 135 C. This
was cut into 25cm x 25cm squares and pressed into a laminate
,
;
; - 13 -
.~:
. .
'.,~
.. .. . .
- `` 1~48~76
at 175C,t70 kg/cm for 1 hour. The laminate produced was ~.. post-cured from 140 to 250C over 23 hours and had the .
. following flexural strengths
.. Flexural measured strength at 20C 5700 kg/cm2
150C 2680 " "
~ 200C 1300
:s 250C 1016 " "
~'`' ' .
,. .
,;~,
~ .
.'1 '
. ' .
, .
. .
., ~ .
,.~.
.
.
, . . .
.,~, .
.
....
.
;,,
.
,
. . ,
.~:
- 14 - .
`;;:
,: .
.. :, . . ..
.. .
::; .
: .:
1q~4~3~76
` SUPPLEMENTARY DISCLOSURE
,,'' ' :
In the main disclosure are described resin compositions
which comprise a resin having repeating units of the formula
.,i .
~H R' CH Ar
(CH2ArOH)n OH
and an uncured or partly cured condensate of formaldehyde and
melamine. The formaldehyde condensate acts as a curing agent
for the resin to give cured products with good electrical
properties and high heat resistance.
; We have found that if the weight of the condensate
is 55 - 90% of the combined weight of resin and condensate,
. , .
then the cured products have good arc and track resistance and
: strength at high temperatures which may be accompanied by high
heat resistance as well.
The compositions with the higher amounts of condensate
comprise (a) a resin having repeating units of the formula
-CH2 - R' - CH - Ar
I
- (CH2ArOH)n OH
terminated with ArOH groups wherein R' is a divalent or trivalent
~ 20 aromatic hydro-carbyl or divalent or trivalent di(aromatic
; hydrocarbyl) oxy group, which optionally has at least one inert
substituent and Ar is a residue formed by removal of two
nuclear hydrogen atoms from a phenolic compound having 1 - 3
hydroxyl groups and at least two nuclear hydrogen atoms in ortho
. ,,
and/or para positions to a hydroxyl group, and n is 0 or 1 and
;` (b) a condensate formed from formaldehyde ( or a compound
~ yielding it in situ such as paraformaldehyde or hexamethylene,.............. .
tetramine) and melamine, said condensate being in an uncured
- or partially cured form and provided 55 - 90% by weight of
the total weight of resin and condensate.
- 15 -
:, . .~ . .;
: .
,,;
` i~48~76
` The condensates are preferably made by reaction of"'
one molar proportion of melamire with 1.2 - 10 molar proportions
of formaldehyde (or less preferred, the equivalent amount of
formaldehyde yielding compound) especially 1:2 to 1:8 molar
~ proportions, in neutral or alkaline conditions. The condensate
: is uncured or partially cured, usually with not more than five
repeat units derived from the nitrogenous compound. Preferably
it is uncured with one structural unit derived from melamine and
at least two hydroxymethyl groups attached to nitrogen atoms.
The two hydroxymethyl groups may be attached to the same or
different nitrogen atoms. Preferably the condensate contains
hydroxy methyl groups attached to nitrogen atoms in an average
number from two, (and preferably from 2.5) to the maximum
number of hydrogen atoms attached to nitrogen ato~s in the
melamine. The condensate preferably contains 2 to 6, usually
; an average of 2.5 to 6, and especially 3 or 6 (as in trimethyl-
~ olmelamine and hexamethylolmelamine) hydroxymethyl groups. An
- average of 2.5 hydroxy methyl groups per molecule of melamine
means that, for example, the condensate is a 1:1 molar mixture
of a condensate with 2-, and a condensate with 3-hydroxymethyl
` groups per molecule of melamine.
~ The amount of formaldehyde condensate is 55 - 90%
; by weight of the total weight of resin and condensate. Amounts
; .:
i ` of 58 - 74%, eg. 60 - 70% are preferred as these amounts give
cured products with high strength at high temperatures and
, ~ . ,
moderate retention of strength after aging at high temperatures
but coupled with a moderate comparative tracking index. Amounts
j of 74 - 90%, eg. 80 - 90%, are used if a much higher comparative
'!, tracking index of the cured products is wanted.
The resin has repeating units of formula
'~''"',
- - 16 -
..,.
.. 31~
g~i76
- CH2 - R' CH - Ar -
:~ - (CH2ArOH)n OH
and is terminated by ArOH groups. Preferably the resin contains
substantially only units derived from ArOH and units of skeletal
structure -- -
- - C - R' - C -
(- C ~)n
The resin is preferably made,following the general
procedure described in British Patent No. 1150203,by reacting
(1) an aralkyl ether of the general formula R'(CH2OR)a and/or
aralkyl halide of the general formula R'(CH2X)a, wherein R', R,
a and X are as defined above, with a molar excess of a phenolic
compound, or a mixture thereof with a nonphenolic compound
containing an aromatic nucleus. While R' is preferably an
unsubstituted aromatic hydrocarbyl group, especially a m-
; or p- phenylene group, if desired the R' radical may contain at
least one substituent attached to the aromatic nucleus, which
substituent is an alkyl group of 1 to 6 carbon atoms, e.g.
a methyl group a phenyl group or a halogen atom, e.g. a chlorine
or bromine atom. These substituents are inert under the con~
ditions of the reaction. In fact the presence of chlorine or
) fluorine atoms in some or all of the available positions in the
aromatic nucleus is advantageous in that it leads to improved
flame resistance in the resulting polymeric products. Examples
of such substituted aralkyl ethers and aralkyl halides, which
may be employed according to this invention, are 2, 3, 5, 6 -
; tetrachloro - 1, 4 - di (chloromethyl) benzene and 2, 3, 5, 6 -
~" tetrachloro - 1, 4 - di(methoxy-methyl) - benzene.
:,,
~ The phenolic compound is any compound or mixture of
..
compounds derived from benzene and containing 1 to 3, preferably
~- 1 or 2, hydroxyl radicals joined to an aro~atic nucleus, at
least two of the ortho and para positions to a hydroxyl
:- .
r
~ ~ ~ 17 ~
~, .
" 1q~48~i76
:.
group b~ing unsubstituted and any non-hydroxlic substituents
being inert under the conditions of the reaction. Thus the
phenolic compounds may be of formula
OH
~ (R3)1-3
where each R3 is hydroxyl, alkyl of 1 to 8 carbon atoms, e.g.,
methyl, ethyl, isopropyl, tertiary butyl or tertiary octyl,
halogen e.g. chlorine, nitro, phenyl and bis(hydroxyphenyl)-alkyl,
e.g. bis(hydroxy phenyl)- methylene, -ethylene and -isopropyl-
idene. Preferably the phenolic compounds contain only onearomatic ring. Examples of these phenolic compounds are phenol,
p - cresol, m - cresol, resorcinol, catechol, 4 - methyl-
catechol, isopropyl catechol, d1phenylol propane (bis 2,2- (4-
hydroxy phenyl) propane), diphenylolethane, monoalkyl phenols
such as p-ethylphenol, p-tertiary butyl phenol and p-tertiary
.:
octyl phenol, m - and p - phenyl phenol, pyrogallol and
phloroglucinol. A mixture of phenol and beta naphthol as des-
cribed in our British Patent Specification No. 1363531 may be
used. Mixtures of the phenols can be used such as a mono-
phenol with a dihydric phenol, e.g. resorcinol with phenol
itself, or mixtures of diphenols, e.g. 4-methyl catechol and
; catechol and/or resorcinol, such as that sold as a phenolic
coal tar fraction. Preferably these particular mixtures or
phenol itself resorcinol, or catechol are used.
The aralkylene compound of formula R'(CH2OR)a or
; R(CH2X)a is preferably substantially pure usually with at
least 90% by weight of the expected compound, but technical
grade materlals may be used. Thus technical grade p-xylylene
glycol dimethyl ether can contain 65 - 90% of the expected
30 compound, 0.1 - 5% of p-methoxymethyl toluene, 0.1 - 10% of
, - 18 -
"',
,. . . . .
-..... . : - . : :
1~48~76 ~
p-tolualdehyde dimethyl acetal and 10 - 35% of p-methoxymethyl-
benzaldehyde dimethyl acetal and small amounts of other im-
purities. The amount of the acetal includes any of the corres-
ponding aldehyde present.
The reaction to form the resin is carried out with
one mole of aralkylene compound and a molar excess of the
phenolic compound or mixture thereof with the aromatic com-
pound. Preferably at least 1.3 moles of phenolic compound ~-
(or mixture) per mole of aralkylene compound are used. From
1.3 to 3 moles of the phenolic compound are suitably employed
for every mole of the aralkylene compound. When the molecular
proportion falls below the specified 1.3:1 ratio and approaches
; 1:1 the reaction mixture exhibits an increased tendency to gel
prematurely. When in the aralkylene compound a is 2 and the
. , ~ratio of phenol to compound is greater than 2.5, the resulting ~-
.7 products become more difficult to cure. Polymeric products
having the highest softening points are obtained when the ratio
of the phenolic compound to aralkylene compound is at the low
end of the specified range. Preferably when a in the compound
is 2 the phenolic compound is employed in a ratio of 1.3:1 to
2:1 e.g. 1.3 to 1 to 1.7 to 1, especially 1.4 to 1.6:1. When
a in the compound is 3, the phenolic compound is preferably
employed in a ratio of 2:1 to 3:1 e.g. 2.5:1 to 3:1.
The compositions of the invention are cured by heat-
ing, usually at above 70C and preferably 100 - 180C, e.g.
~;~ 150 - 180C. Post curing may also be carried out, usually
:~ .
, initially at 60 - 100C for 4 - 24 hours, and then at 160 -
250C. The time needed for post curing varies according to
.~i . .
~ the properties of the desired product, and the temperature of
,~ 30 use of that product; examples of times of curing at 100 - 180C
,: .,
are 0.5 - 48 hours, e.g. 0.5 - 10 hours at 150 - 180C. The
,, , 19
' !
: ' . ." . : ~ .
. .
,.'. '. ` ~' ' : .
'; -
1~)41~i76
cured articles are usually in the form of moulded products or
laminates.
In the production of laminates, a solution or dis-
persion of the resin and condensate is used to impregnate a
fibrous laminate base. The fibrous material into which the
resin has been impregnated is usually then subjected to a
precure heat treatment at 100 - 160C, often at 130 - 140C for
5 - 20 minutes, e.g. for about 10 mins. In the prepregs formed
` the resin and condensate have partly reacted. A stack of the
prepregs is then pressed at a temperature above 160C, often
in the range 170 - 190C at a pressure of from 100 to 1,500 psi,
although pressures above 500 psi, often of about 1,000 psi are
normally employed. Normally pressing will be carried out for
a period of at least 1/2 hour, and generally up to 2 hours,
often for about an hour, depending upon the conditions of
temperature and pressure employed.
For optimum results the laminates are subsequently
post cured, e.g. by heating outside the press (as in air
circulating oven). The temperature and time employed for the
post cure operations are dependent upon each other, and on the
; use of the product and the degree of post cure. Usually the
post cure is at 60 - 100C for 4 - 24 hours, e.g. 12 - 24
hours at 80 - 100C, and then for at least 3 hours, and often
4 - 48 hours, at a temperature of 140 - 250'C, often raising
the temperature from a value in the range 140 - 180C to a
value in the range 190 - 250C during that time. A post cure ~-
in the temperature range 140 - 190C may take 5 - 7 hours,
whereas one in the range 220 - 250C may be accomplished in
., .
3 - 5 hours. However it is normally desirable that the
i 30 material is heated to a temperature in the range 190 - 220C.
., :
The cured products with good comparative tracking
... .
. .
. .
.
- - ~
1~48676
index may be used in electrical insulation, e.g. in insulators
for external uses or in electric motors.
The invention is illustrated in the following ;
Examples.
The technical grade p-xylylene glycol dimethyl ethers
used in the Examples are products containing 65 - 75% p-
;xylylene glycol dimethyl ether, 0.5 - 3~ p-methoxymethyltoluene,
i ~ . :. -
; 0.5 - 5% p-tolualdehyde dimethyl acetal, 10 - 25% of p-methoxy-
methylbenzaldehyde dimethyl acetal and small amounts of other
- 10 p-xylenes substituted in the side chains with methoxy groups.
The amount of acetal includes any of the corresponding
aldehyde present. ~`
Example 2 and Comparative Example 1
Condensate A
; ,. ,
'252 g (2 moles) of melamine were added to 429 g
,...................................................................... .
(5 moles) of a 38% formaldehyde solution and the resultant
;' -mixture was heated until a clear solution was obtained at 70C.
.;. .
Then, 127 g of 2-ethoxyethanol was added to give a 50% solution
.,~
of melamine condensate (nominally a mixture of di and tri-
methylolmelamines).
The following solution formulations were prepared:-
~^~ Comp. Ex. 1. 2
Solutions A B
-
Aralkyl-phenol resin from p-xylylene
glycol dimethyl ether tech (40 mol.%)
and phenol (60 mol.%) prepared as
~'. described in BP1150203.
Softening point 88C. 250 g 165 g
.';'
!, " Solution of condensate A. 500 g 660 g
;$' 30 2 - ethoxyethanol 365 g 275 g
,
;;~ Concentration of condensate (based on
total weight of condensate and resin). 50% 66.7%
.,~.,. . ~.
~ . .
~. 1
,.: ,:
.,:: .
- - 21 -
''
` 1~48f~76
The solutions A and B were impregna~ed into Marglass
116T/P705 glasscloth and then the impregnated glasscloth pre-
cured at a temperature at 120C and 115C respectively each
for 10 minutes. Laminates were made from the prepregs pro-
duced by pressing for 1 hour at 175C and 1,000 psi, and then
post curing in an air circulating o~en for 16 hours at 90C
and 6 hours from 140 - 200C. The resin contents of the
laminates A and B prepared in this way were 31.7%, and 31.7
respectively.
After post curing, flexural strength measurements
were made on the laminates at about 20C, 150C and 200C
before and after heat aging at 200C. The results obtained
~ .
were as follows.
Flexural strengths at 20C (psi)
A B
initial 38,600 -40,100
after 24 hrs. at 200C 40,000 32,900
' "48 hrs. " 43,000 31,900
"100 hrs. " 36,800 27,600
"250 hrs. " 20,000 17,800
, "500 hrs. " 10,000 11,000
. . .
"750 hrs. " D.L. 8,900
" 1000 hrs. " D.L. D.L.
D.L. means delaminated, i.e. the sample split, an indication ;~
of poor strength.
Flexural strengths at 150C (psi)
A B
initial 41,500 33,700
after 24 hrs. at 200C 31,600 23,200
" 48 hrs. " 44,600 25,300
" 100 hrs. " 32,200 23,000
: ' .
- 22 -
.~
". 1048~76
Flexural strengths at 150C (psi)
(cont'd)
A B -
after 250 hrs. at 200C 15,500 14,400
; " 500 hrs. " D.L. 10,500
,
. " 750 hrs. " D.L. 8,100
" 1000 hrs. " D.L. D.L.
Flexural strengths at 200C (psi)
A B
,~ 10 initial 39,300 26,100
,;
, after 24 hrs. at 200C 35,200 29,600
' "48 hrs. " 35,000 34,100
"100 hrs. " 32,300 23,400
~` "250 hrs. " 13,800 13,800
"500 hrs. " 8,800 8,800
"750 hrs. " D.L. 9,900
n 1000 hrs. 1! D.L. D.~.
Thus the initial strength at low and high temp-
eratures of laminates is adequate and a significant per-
~, 20 centage of that strength is retained on aging at 200C.
.. . . .
Condensate Resin B
378 gms (3 moles) of melamine were added to 772
.,,~: .
,~ gms (9 moles) of a 38% w/v formaldehyde solution and the
~' resultant mixture was heated until a clear solution of tri-
methylol melamine was obtained at a~out 70C. At this point -
1150 gms of 2 - ethoxyethanol were added with stirring and
~` the solution was cooled.
Example 3 and Comparative Example 3
.~., . :
,~ Resin A
:.~ . .
282 g (3 moles) of phenol were mixed with 249 (1.5
'; moles) of technical p-xylylene glycol dimethylether in the
presence of 0.2 mls of diethyl sulphate as catalyst. The
- 23 -
mixture was heated to 135 - 180C and the methanol formed by
- reaction was distilled out. The product was a red-brown semi-
solid.
The following solutions were prepared:-
Comparative Ex. 2 Ex. 3 r
Solution _ _
aralkyl phenol resin A362 g 181 g
solutio~ of condensate A 362 g 724 g
2-ethoxyethanol 436 g 255 g
These solutions have concentrations of 33.3% and 66.7% of
the condensate based on the total solids content. Glasscloth
laminates were made from the solutions as in Example 2 with
precure conditions of 10 mins. at 134C for C and at 140C
for D.
The resin contents of the laminates were 35.0% and
30.0% respectively. The laminates were post cured as des- -
cribed in Example 2. Their flexural strengths after heat aging
at 200C were measured.
Laminate CFlexural strengths (psi)
:. .
RT 150C 200C
initial 85,600 30,70015,400
after 24 hrs. at 200C75,500 50,40026,000
" 48 hrs. " 85,900 60,00038,800
" 100 hrs. " 88,300 60,00035,600
" 250 hrs. " 78,000 61,70054,100
Laminate D Flexural strengths (psi)
RT 150C 200C
initial 45,000 44,20043,200
after 24 hrs. at 200C43,600 44,50047,600
" 48 hrs. " 43,500 31,40045,200
" 100 hrs. " 48,800 39,00041,300
- 24 -
1~48f~76
Flexural strengths (psi) (cont'd)
RT 150C 200C
after 250 hrs. at 200C 21,300 18,600 18,600
These results show that the laminate D (from 66.7~
condensate) has adequate strength and some retention of that
strength at high temperatures, though not as much as that of
laminate C (from 33.3% condensate).
Examples 4 to 6 and Comparative Examples 3 and 4
Preparation of Trimethylolmelamine
.
378 g (3 moles) of melamine were added to 772 g
(9 moles) of a 38~ w/v formaldehyde solution and the resultant
mixture was heated until a clear solution was obtained at
about 70C. On cooling to room temperature solid trimethyl-
olmelamine precipitated. This was filtered and dried in an
air-circulating oven at 60C.
The following mixes were prepared:-
Examples: Comp. Ex. ~ Comp. Ex. 4 4 5 6
Mixes: E F G H J
Aralkyl-phenol resin
(as used in Example 2). 80g 40g 32g 24g 16g
Trimethylolmelamine (TMM) - 40g 48g 56g 64g
Silica 120g 120g120g120g 120g
Magnesium oxide 2.6g 2.6g2.6g2.6g 2.6g
Zinc stearate 3.2g 3.2g3.2g3.2g 3.2g
Hexamine 10g
The amount of trimethylolmelamine in E to J is 0,
50, 60, 70 and 80% respectively, based on the total weight
of aralkyl-phenol resin and trimethylolmelamine. -
E was milled for 12 minutes at 120C. The rest
were milled for 2 minutes at 120C.
Discs were moulded from each of the mixes ~sing a
pressure o~ 1,000 psi for 30 minutes, at 175C. The discs
1~;)4~i67~i
were post cured by heating at 90C for 16 hours and from 140C
to 200C over 9 hours.
The comparative kracking index (CTI) was obtained
for each disc according to BS.3781.
The results were as follows:
Disc from Mix. CTI
E 150
F 140
G 250
H 240
J 400
Thus mixes G and H, having 60 and 70% respectivel~
condensate give higher CTI values than F with 50~ TMM, but
the CTI from mixture J with 80~ TMM is highest. -
.
Examples 7 - 10 and Comparative Examples 5 and 6
50% solutions of aralkylene-phenol resin as used
in Example 2 and 50% solutions of trimethylolmelamine (TMM)
Condensate B, each in 2-ethox~ ethanol, were mixed in different
proportions to give a series of solutions K - Q. Each of the
20 solutions was heated in an aluminium dish at 130C for 30
minutes to evaporate the solvent and cause curing and then
heated at 250C for two hours in complete the cure. Each
specimen produced was weighed and then re-weighed after being
heated for 24 hours at 250C. The weight loss on the aging
as a percentage of the original weight was as follows.
Example Solution % Resin % TMM ~ Weight Loss
Comp. Ex. 7 K 50 50 4.0
Ex. 7 L 40- 60 4.7
Ex. 8 M 30 70 6.2
Ex. 9 N 20 80 8.5
Ex. 10 P 10 90 9.3
Comp. Ex. 8 Q 0 100 9.8
.
~ - 26 -
. - : . . .
1~48676
These results and those of Examples 4 - 6 show that
with 60 - 7~ TMM, the cured products have a moderate com-
parative tracking index and a moderate resistance to high
temperature aging, while with 80 - 90~ T~$ the CTI is large
but the resistance to aging is poorer. .
. - 26a -
