Note: Descriptions are shown in the official language in which they were submitted.
RD-18473
1 336$64
POLYEPOXIDE AND POLYPHENYLENE ETHER-POLYEPOXIDE
COMPOSITIONS US~uL IN P~IN$ED CIRCUIT BOARD PRODUCTION
This invention relates to resinous compositions
useful as dielectrics, and more particularly to polypheny-
lene ether-polyepoxide compositions suitable for fabrication
into printed circuit boards.
A number of polyphenylene ether-polyepoxide
compositions having favorable dielectric properties, and
supposedly being useful in circuit board manufacture, are
known. However, for the most part these have not att~ine~
wide commercial use because of deficiencies in one or more
properties. Thus, while the polyphenylene ether~ are
excellent dielectrics and the properties of combinations
thereof with polyepoxide~ are favorable in thiæ respect,
they lack solvent resistance which i8 reguired in order for
the circuit board to survive cleaning with such solvents as
methylene chloride. Other deficiencies are found in areas
~uch as flammability, solderability and resistance to high
temperatures. Moreover, times required for curing such
compositions are typically too long for effective manufac-
ture of circuit boards in large volume.
In addition to excellent dielectric properties,
resinous compositions to be used for printed circuit board
manufacture should be highly flame-retardant. A V-l rating,
as determined by Underwriters Laboratories test procedure
UL-94, is universally required with V-O usually being
necessary. The V-O rating requires a flame-out time (FOT)
of not more than 10 seconds in any trial and a cumulative
EOT of not more than 50 seconds for five sample~. As a
practical matter, a maximum cumulative FOT of 3S ~econds i8
often mandated by purchaserR.
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The fabricated board should not lose substantial
weight and its surface should not be appreciably marred
by contact with methylene chloride. Solderability should
be good, as evidenced by the lowest possible percent
increase in thickness (Z-axis expansion) of the board
when exposed to liquid solder at 288C. In addition to
all these properties of the cured material, a relatively
short curing time is highly desirable.
Commonly owned United States Patent 4,912,172,
issued March 20, 1990, discloses polyphenylene ether-
polyepoxide compositions which are curable by a zinc or
aluminum salt of a diketone such as acetylacetone,
optionally in the presence of a phenolic compound or
basic nitrogen compound as a curing accelerator. While
these compositions have excellent dielectric properties
and solder and solvent resistance, there is room for ~
improvement in flame retardancy and curing time.
In Japanese Patent 58/69052, published October
1981, combinations of polyphenylene ethers with various
types of polyepoxides are disclosed. The latter include
epoxy novolak resins and polyglycidyl ethers of such
compounds as bisphenol A and
3,5,3',5'-tetrabromobisphenol A. Curing of these
compositions is achieved by contact with various known
curing agents, including amines. The cured compositions,
however, have been found to be seriously deficient in
solvent resistance and, in certain cases, in
solderability.
The present invention provides a series of resinous
compositions which comprise polyepoxides and combinations
thereof with polyphenylene ethers. The latter, when used to
impregnate suitable fibrous reinforcing materials such as
glass fiber cloth, furnish workable prepregs. Said
compositions are readily soluble in organic solvents,
facilitating impregnation. They may be combined with other
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1 336464
ingredients to form rapidly curable materials which are
highly solder resistant, solvent resistant and flame re-
tardant, and which have excellent dielectric properties and
dimensional stability at high temperatures. Therefore, the
cured materials are excellent when employed as laminates for
printed circuit boards.
In one of its aspects, the invention includes
resinous compositions containing 15-20% chemically combined
bromine and comprising the reaction product obtained by
heating, in the presence of a catalytic amount of at least
one basic reagent, a mixture comprising:
(A) at least one halogen-free bisphenol polygly-
cidyl ether having an average of at most one aliphatic
hydroxy group per molecule;
lS (B) about 15-25% of at least one halogen-free
epoxidized novolak; and
(C) 25-35% of at least one bisphenol containing
bromine as aryl substituents;
all percentages being by weight of total reagents
A, B and C.
Reagent A in the compositions of this invention is
at least one halogen-free bisphenol polyglycidyl ether. The
most common compounds of this type are prepared by the
reaction of bisphenols with epichlorohydrin. (By "bisphe-
nol" as used herein is meant a compound containing twohydroxyphenyl groups attached to an aliphatic or cyclo-
aliphatic moiety, which may also contain aromatic sub-
stituents.) Said compounds may be represented by the
formula
~J - lc~73
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1 336464
(I) CH2-C~CH2O-A -Y-A ~OCH2CHCH2O-A -Y-A~ OCH2CH-CH2
wherein n has an average value up to 1, each of Al and A2 is
a monocyclic divalent aromatic radical and Y is a bridging
radical in which one or two atoms separate Al from A2. The
o-Al and A2-o bonds in formula I are usually in the meta or
para positions of Al and A in relation to Y.
In formula I, the Al and A2 values may be unsub-
stituted phenylene or substituted derivatives thereof,illustrative substituents (one or more) being alkyl, nitro,
alkoxy and the like. Unsubstituted phenylene radicals are
preferred. Each of A and A2 may, for example, be o- or
m-phenylene and the other p-phenylene, but both are pre-
lS ferably p-phenylene.
The bridging radical, Y, is one in which one or
two atoms, preferably one, separate Al from A2. It is most
often a hydrocarbon radical and particularly a saturated
radical such as methylene, cyclohexylmethylene, ethylene,
isopropylidene, neopentylidene, cyclohexylidene or cyclo-
pentadecylidene, especially a gem-alkylene (alkylidene)
radical and most preferably isopropylidene. Also included,
however, are radicals which contain atoms other than carbon
and hydrogen; for example, carbonyl, oxy, thio, sulfoxy and
sulfone.
The materials which are preferred as reagent A are
commercially available reaction products of epichlorohydrin
~-~ and ~2,2)-bis(4-hydroxyphen(yl~propane (bisphenol A), including
EPON 825 (n = 0) and EPO 828 (n = about 0.14), a~ailable
from Shell Chemical Co.
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Reagent B is at least one halogen-free epoxidized
novolak. Suitable novolaks for use as precursors therefor
are known in the art and are typically prepared by the
reaction of formaldehyde with a hydroxyaromatic compound
such as phenol (which is often preferred), cresol or t-bu-
tylphenol. The novolak then undergoes reaction with an
epoxy reagent such as epichlorohydrin to produce the resin
hseful as reagent B.
Various epoxidized novolaks are commercially
available, and any of them may be used according to the
invention. It is usually strongly preferred that the
epoxidized novolak contain substantially no free phenolic
hydrogen atoms.
Reagent C is at least one bisphenol containing
lS bromine in the form of substituents on the aromatic rings,-
usually a brominated derivative of bisphenol A. Its purpose
according to the invention is principally to provide flame
retardancy. 2,2-Bis(3,5-dibromo-4-hydroxyphenyl)propane is
preferred as reagent C because of its availability, rela-
tively low cost and particular suitability for the purposesof the invention.
As previously mentioned, reagent B comprises about
15-25% and reagent C 25-35% of the compositions of this
invention, with the balance being reagent A. Lower concen-
trations of reagent B or reagent C cause an unacceptable
decrease in solvent resistance and/or flame resistance. An
increase in reagent C may yield an incompatible material.
The preferred proportion of reagent C is in the range of
28-32%.
According to the present invention, a mixture
comprising reagents A, B and C is heated, most often at a
temperature in the range of about 125-225C, preferably
about 150-200C and most preferably about 160-190C, in the
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I 3364~4
presence of a catalytic amount of at least one basic rea-
gent. Said mixture preferably consists essentially of said
reagents; that is, they are the only ones contributing to
the novel and essential properties thereof.
The triarylphosphines, especially triphenylphos-
phine, are the preferred basic reagents by reason of their
effectiveness at low levels, low tendency to cause side
reactions and harmlessness when they remain present after
the reaction is complete. The proportion of catalyst is
typically about 0.1-0.5% by weight. The reaction is pre-
ferably conducted in an inert atmosphere such as nitrogen,
especially when a triarylphosphine is employed as catalyst.
An inert organic solvent having a boiling point no higher
than about 125C, usually an aromatic hydrocarbon such as
toluene, may be employed but usually provides no advantage
at this point.
The structure of the resinous composition thus
obtained is not fully known. It is believed to be an
"upstaged" (i.e., partially cured) composition derived from
the compounds of formula I, in which the brominated moieties
form part of the molecular structure. The epoxidized
novolak may also be chemically bound into the molecules of
the upstaged composition in varying proportions.
The preparation of the upstaged compositions of
this invention is illustrated by the following example.
Example 1
A mixture of 50 parts by weight of bisphenol A
diglycidyl ether, 30 parts of 2,2-bis(3,5-dibromo-4-hy-
droxyphenyl)propane, 20 parts of an epoxy novolak resin
commercially available~from Ciba-Geigy under the gr-~Q
designation "EPN 1138'~ and 0.2 part of triphenylphosphine
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was heated at 165C for one hour in a nitrogen atmosphere,
with stlrring. The product was the desired upstaged com-
position and contained 17.6% bromine.
For the preparation of compositions useful in the
manufacture of printed circuit boards having the desired
properties, the upstaged composition of this invention is
combined with a polyphenylene ether. In particular, another
aspect of the invention is resinous blends containing 5-10%
chemically combined bromine and comprising (I) about 35-60%
of the above-described upstaged composition and (II) about
40-65% of at least one polyphenylene ether, said percentages
being by weight of total resinous components.
The polyphenylene ethers useful as component II in
the blends of this invention comprise a plurality of struc-
tural units having the formula
Q ~ 3
(II)
Q2 Ql
In each of said units independently, each Ql is independ-
ently halogen, primary or secondary lower alkyl (i.e., alkyl
containing up to 7 carbon atoms), phenyl, haloalkyl, amino-
alkyl, hydrocarbonoxy, or halohydrocarbonoxy wherein at
least two carbon atoms separate the halogen and oxygen
atoms; and each Q2 is independently hydrogen, halogen, pri-
2S mary or secondary lowér alkyl, phenyl, haloalkyl, hydro-
carbonoxy or halohydrocarbonoxy as defined for Ql. Examples
of suitable primary lower alkyl groups are methyl, ethyl,
n-propyl, n-butyl, isobutyl, n-amyl, isoamyl, 2-methylbutyl,
n-hexyl, 2,3-dimethylbutyl, 2-, 3- or 4-methylpentyl and the
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corresponding heptyl groups. Examples of secondary lower
alkyl groups are isopropyl, sec-butyl and 3-pentyl. Prefer-
ably, any alkyl radicals are straight chain rather than
branched. Most often, each Ql is alkyl or phenyl, especial-
ly C1 4 alkyl, and each Q2 is hydrogen. Suitable poly-
phenylene ethers are disclosed in a large number of patents.
Both homopolymer and copolymer polyphenylene
-éthers are included. Suitable homopolymers are those con-
taining, for example, 2,6-dimethyl-1,4-phenylene ether
units. Suitable copolymers include random copolymers con-
taining such units in combination with (for example) 2,3,6-
trimethyl-1,4-phenylene ether units. Many suitable random
copolymers, as well as homopolymers, are disclosed in the
patent literature.
Also included are polyphenylene ethers cont~ining
moieties which modify properties such as molecular weight,
melt viscosity and/or impact strength. Such polymers are
described in the patent literature and may be prepared by
grafting onto the polyphenylene ether in known manner such
non-hydroxy-containing vinyl monomers as acrylonitrile and
vinylaromatic compounds (e.g., styrene), or such non-hy-
droxy-containing polymers as polystyrenes and elastomers.
The product typically contains both grafted and ungrafted
moieties. Other suitable polymers are the coupled polyphen-
ylene ethers in which the coupling agent is reacted in knownmanner with the hydroxy groups of two polyphenylene ether
chains to produce a higher molecular weight polymer contain-
ing the reaction product of the hydroxy groups and the
coupling agent. Illustrative coupling agents are low
molecular weight polycarbonates, quinones, heterocycles and
formals.
For the purposes of this invention, the polypheny-
lene ether has a number average molecular weight within the
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range of about 3,000-40,000, preferably at least about
12,000 and most preferably at least about 15,000, and a
weight average molecular weight within the range of about
20,000-80,000, as determined by gel permeation chromato-
graphy. Its intrinsic viscosity is most often in the rangeof about 0.35-0.6 dl./g., as measured in chloroform at 25C.
The polyphenylene ethers are typically prepared by
the oxidative coupling of at least one corresponding mono-
hydroxyaromatic compound. Particularly useful and readily
available monohydroxyaromatic compounds are 2,6-xylenol
(wherein each Q is methyl and each Q2 is hydrogen), where-
upon the polymer may be characterized as a poly(2,6-di-
methyl-1,4-phenylene ether), and 2,3,6-trimethylphenol
(wherein each Ql and one Q is methyl and the other Q2 is
hydrogen).
A variety of catalyst systems are known for the
preparation of polyphenylene ethers by oxidative coupling.
There is no particular limitation as to catalyst choice and
any of the known catalysts can be used. For the most part,
they contain at least one heavy metal compound such as a
copper, manganese or cobalt compound, usually in combination
with various other materials.
A first class of preferred catalyst systems con-
sists of those containing a copper compound. Such catalysts
are disclosed, for example, in U.S. Patents 3,306,874,
3,306,875, 3,914,266 and 4,028,341. They are usually com-
binations of cuprous or cupric ions, halide (i.e., chloride,
- bromide or iodide) ions and at least one amine.
Catalyst systems containing manganese compounds
constitute a second preferred class. They are generally
alkaline systems in which divalent manganese is combined
with such anions as halide, alkoxide or phenoxide. Most
often, the manganese is present as a complex with one or
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more complexing and/or chelating agents such as dialkyl-
amines, alkanolamines, alkylenediamines, o-hydroxyaromatic
aldehydes, o-hydroxyazo compounds, ~-hydroxyoximes (mono-
meric and polymeric), o-hydroxyaryl oximes and ~-diketones.
Also useful are known cobalt-containing catalyst systems.
Suitable manganese and cobalt-containing catalyst systems
for polyphenylene ether preparation are known in the art by
reason of disclosure in numerous patents and publications.
Particularly useful polyphenylene ethers for the
purposes of this invention are those which comprise mole-
cules having at least one of the end groups of the formulas
N(R2)
Q ~ C(R )2
(III) -O ~ OH and
Q2 Ql
Ql Q2 Q2 Ql
~ Q Q ~
wherein Ql and Q2 are as previously defined; each Rl is
independently hydrogen or alkyl, with the proviso that the
total number of carbon atoms in both Rl radicals is 6 or
less; and each R is independently hydrogen or a C1 6 pri-
mary alkyl radical. Preferably, each Rl is hydrogen andeach R2 is alkyl, especially methyl or n-butyl.
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1 336464
RD 18473
Polymers containing the aminoalkyl-substituted end
groups of formula III may be obtained by incorporating
an appropriate primary or secondary monoamine as one of
the constituents of the oxidative coupling reaction
mixture, especially when a copper- or manganese-
containing catalyst is used. Such amines, especially
the dialkylamines and preferably di-n-butylamine and
dimethylamine, frequently become chemically bound to
the polyphenylene ether, most often by replacing one of
the ~-hydrogen atoms on one or more Ql radicals. The
principal site of reaction is the Q1 radical adjacent to
the hydroxy group on the terminal unit of the polymer
chain. During further processing and/or blending, the
aminoalkyl-substituted end groups may undergo various
reactions, probably involving a quinone methide-type
intermediate of the formula
Q2 C~R )2
(V~ ~0 ~0
Q Q
wherein Ql and Q2 and R1 are as previously defined, with
numerous beneficial effects often including an increase
impact strength and compatibilization with other blend
components. Reference is made to United States Patents
4,054,553, 4,092,294, 4,477,649, 4,477,651 and
4,517,341.
Polymers with 4-hydroxybiphenyl end groups of
formula IV are typically obtained from reaction
mixtures in which a by-product diphenoquinone of the
formula
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1 336464
Ql Q2 Q2 Ql
(VI) 0 ~ ~ 0
Ql Q2 Q2 Ql
is present, expecially in a copper-halide-secondary or
tertiary amine system. In this regard, the disclosure
of United States Patent 4,447,649 is again pertinent as
are those of U.S. Patents 4,234,706 and 4,482,697. In
mixtures of this type, the diphenoquinone is ultimately
incorporated into the polymer in substantial
proportions, largely as an end group.
In many polyphenylene ethers obtained under the
above-described conditions, a substantial proportion of the
polymer molecules, typically constituting as much as about
90% by weight of the polymer, contain end groups having one
or frequently both of formulas III and IV. It should be
understood, however, that other end groups may be present
and that the invention in its broadest sense may not be
dependent on the molecular structures of the polyphenylene
ether end groups.
It will be apparent to those skilled in the art
from the foregoing that the polyphenylene ethers contem-
plated for use in the present invention include all those
presently known, irrespective of variations in structural
units or ancillary chemical features.
In addition to the polyphenylene ether and the
upstaged composition, the resinous blends of this invention
preferably contain (III) an amount up to about 10% of at
least one polyepoxy compound selected from those described
hereinabove with reference to reagents A and B. Said
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polyepoxy compound acts to improve the solvent resistance of
the cured compositions described hereinafter. The epoxi-
dized novolaks (reagent B) are usually preferred by reason
of their high solubility in the solvents ordinarily employed
as described hereinafter. Resinous blends which do not
contain component III are within the scope of the invention
but are generally not preferred.
: The resinous blends of this invention contain
about 35-60% of component I and about 40-65% of component
II. When component III is present, it comprises up to about
10%. All ~f said percentages are based on the total resin-
ous components in said blend. The preferred proportions are
about 35-45% of component I, about 50-60% of component II
and about 4-8% of component III. The blends also contain
5-10%, preferably 6-9%, of chemically combined bromine ---
supplied, at least in part, by component I. The foregoing
percentages are exclusive of any solvent which may be
present.
The principal utility of the upstaged compositions
and resinous blends of this invention is in the preparation
of cured resinous laminates useful in printed circuit
boards. For this purpose, the resinous blends are combined
with various other materials either during or after their
preparation. Such other materials may include, for example,
conventional catalysts and/or hardeners.
The resinous blends are particularly useful when
dissolved in an inert organic solvent, generally an aromatic
hydrocarbon such as toluene, and used to impregnate glass
cloth which can be formed into prepregs. Upon curing, said
prepregs can be used to form copper-clad laminates useful
for the manufacture of printed circuit boards which, as
previously mentioned, are characterized by excellent
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RD-18473
dielectric properties, solderability, flame retardancy and
resistance to high temperature conditions and solvents.
A particularly useful genus of curable compositions
for this purpose, which is disclosed and claimed in commonly
owned U.S. Patent No. 4,853,423, issued August 1, 1989,
contains chemically combined bromine in an amount effective
to impart flame retardancy and comprises about 25-50% of
component I, about 35-55% of component II, preferably an
amount up to about 10% of component III, and;
(IV) about 4-15% of at least one halogen-free
novolak, substantially all oxygen therein being in the form
of phenolic hydroxy groups;
(V) an amount of at least one of imidazoles and
arylene polyamines to provide a total of at least 2 milli-
equivalents of basic nitrogen per 100 parts of said curable
composition;
(VI) about 0.1-1.0% of zinc in the form of a zinc
salt which is soluble or stably dispersible in said curable
composition; and
(VII) about 1-4% of antimony pentoxide stably
dispersed in said curable composition;
said curable composition being dissolved in an
effective amount, typically to a solute concentration of
about 30-60%, of an inert organic solvent;
all percentages being by weight and percentages of
components I-VIII being based on the total of said
components and any other resinous materials and brominated
materials present.
Component IV is at least one novolak in which
substantially all oxygen is in the form of phenolic hydroxy
groups. Thus, it is similar in molecular structure to the
previously described epoxidized novolak except that it has
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not been epoxidized. t-Butylphenol-formaldehyde novolaks
are often preferred.
Component V is at least one compound selected from
the group consisting of imidazoles and arylene polyamines.
Any of such imidazoles and polyamines known in the art to be
useful as curing agents for epoxy resins may be employed.
Particularly useful imidazoles are imidazole, 1,2-dimethyl-
imidazole, 2-methylimidazole, 2-heptadecylimidazole and
1-(2-cyanoethyl)-2-phenylimidazole. Commercially available
imidazole-arylene polyamine mixtures are often preferred;
the especially preferred mixtures contain arylene polyamines
with a high degree of alkyl substitution on the aromatic
ring, typically at least 3 such substituents. The diethyl-
methyl-substituted m- and p-phenylenediamines are generally
the most preferred polyamines.
The amount of component V is selected to achieve
rapid cure after solvent removal. This requires at least 2
and preferably at least 4.5 milliquivalents of basic nitro-
gen per 100 parts of the curable composition, including any
basic nitrogen present in the polyphenylene ether (mostly as
end groups of formula III). Thus, when a polyphenylene -
ether essentially free from basic nitrogen is employed the
proportion of component V must be increased. (For the
purpose of this invention, the equivalent weight of an
imidazole is equal to its molecular weight and that of a
diamine is half its molecular weight.)
Component VI is chemically combined zinc, fur-
nished in the form of a zinc salt which is soluble or stably
dispersible in the curable composition. Zinc salts of
diketones in which one carbon atom separates the carbonyl
groups, especially zinc acetylacetonate, and zinc salts of
fatty acids, especially zinc stearate, are examples of
suitable forms of zinc for this purpose. In general, the
R3-18 73
1 336464
fatty acid salts are preferred when component V contains
alkylene polyamines, and diketone salts are preferred when
component V is entirely imidazole.
Under certain conditions, zinc bis(acetylaceton-
ate) can form a hydrate which readily loses acetylacetoneand becomes insoluble in the organic systems used for
laminate preparation. Therefore, it may be necessary to
take steps to maintain the zinc in stable dispersion.
One means for doing this is to subject the compo-
sition to continuous agitation; however, this is generallynot practical. A better method is to form an alcoholate of
the zinc acetylacetonate, as by reaction with methanol.
Said alcoholate loses alcohol rather than acetylacetone
under similar conditions, remaining in solution or homoge-
neous suspension.
Another method for maximizing homogeneity is to
employ a zinc fatty acid salt. Still another method is to
employ a titanium compound as a compatibilizer, as disclosed
hereinafter.
Component VII is antimony pentoxide, which must
also be maintained in stable dispersion. This may be done
by agitation and/or combination with a suitable dispersing
agent, of which many are known in the art.
One preferred dispersing agent is a polymer which
is compatible with the resinous constituents of the curablecomposition but is substantially non-reactive under the
conditions employed, typically a polyester. More powerful
dispersing agents, such as amines, may be required when
component VI is a fatty acid zinc salt, since such salts may
otherwise form insoluble complexes with antimony pentoxide.
Also present, preferably, in the curable composi-
tion is the above-described component III, in the amount of
about 4-1S%.
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In the curable composition, component IV serves as
a hardener and component V as a curing catalyst. Component
VI has cocatalytic properties and accelerates curing; it
also serves to improve solvent resistance and flame retar-
dancy. Component VII functions as a synergist for thebromine to improve flame retardancy. If it is absent, the
proportion of bromine compound required to provide V-O flame
retardancy is much higher, typically about 12%, and the only
way to avoid incompatibility of the bromine compound is to
use more expensive bromine sources.
The broad ranges of proportions of bromine and
components I-VII in the curable compositions are described
hereinabove. The most preferred proportions are:
Bromine - 6-9%;
Component I - about 30-40%;
Component II - about 40-50%;
Component III - about 4.2-4.8%;
Component IV - about 4-8%;
Component V - about 5-10 milliequivalents
of basic nitrogen;
Component VI - about 0.1-0.6% of zinc;
Component VII - about 1-3% of antimony
pentoxide.
Other materials may also be present. These
include inert, particulate fillers such as talc, clay, mica,
silica, alumina and calcium carbonate. In addition, the
bromine content of the curable composition may be supplied
in part by materials such as alkyl tetrabromophthalates
and/or epichlorohydrin reaction products with mixtures of
bisphenol A and tetrabromobisphenol A. The alkyl tetra-
bromophthalates also serve as plasticizers and flow improv-
ers. Such materials as antioxidants, thermal and ultra-
violet stabilizers, lubricants, anti-static agents, dyes and
pigments may also be present.
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1 336464
A material whose presence in minor amount may
improve the solvent resistance and compatibility of the
curable composition is at least one aliphatic tris(dialkyl-
phosphato)titanate. Suitable phosphato~itanates are known
in the art and commercially available. They may be repre-
sented by the formula
R5 ~ ~ ~ O
(VII) (R30-R )2C-CH20Ti~o-~ O-P(OR )2
\ OH x
wherein R3 is C2 6 primary or secondary alkyl or alkenyl and
preferably alkenyl, R4 is Cl 3 alkylene and preferably
methylene, R5 is Cl 5 primary or secondary alkyl, R6 is
C5 12 primary or secondary alkyl and x is from O to about 3
and preferably O or 1. Most preferably, R3 is allyl, R5 is
ethyl, R6 is octyl and x is 0. The phosphatotitanate is
most often present in the amount of about 0.1-1.0 part by
weight per 100 parts of the resinous composition.
The above-described curable compositions may be
employed as varnishes for impregnation of fibrous substrates
(woven or non-woven) such as glass, quartz, polyester,
polyamide, polypropylene, cellulose, nylon or acrylic
fibers, preferably glass. Upon removal of the solvent by
evaporation, fibrous composite prepregs are obtained which
may be cured by application of heat and pressure. As used
herein, "prepreg" means a curable article comprising a
substrate impregnated with an uncured or partially cured
resinous material.
Typically, 2- to 20-ply prepreg laminates are
compression molded at temperatures in the range of about
200-250C and under pressures on the order of 20-60
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1 336464
kg./cm. . Laminates clad with a conductive metal such as
copper, useful for printed circuit board production, may be
so prepared and cured by art-recognized methods. The metal
cladding may then be conventionally patterned.
The preparation of compositions of this invention
and curable compositions containing them is illustrated by
the following examples. All parts and percentages are by
weight unless otherwise indicated.
In Examples 2-9, the following ingredients were
employed:
Component I - the product of Example 1.
Component II - a poly(2,6-dimethyl-1,4-phenylene
ether) having a number average molecular weight of
about 20,000, an intrinsic viscosity in chloroform
lS at 25C of 0.40 dl./g. and a nitrogen content of
about 960 ppm.
Component III - the bisphenol A diglycidyl ether
and the "EPN 1138" of Example 1.
Component IV - a commercially available t-butyl-
phenol novolak having an average molecular weight
in the range of about 700-900.
Component V:
Imidazole-amine mixture - a mixture of
1,2-dimethylimidazole and isomers of diethyl-
methylphenylenediamine, having an average
equivalent weight of about 91.
Component VI - zinc acetylacetonate or zinc
stearate.
Component VII:
~ T~
-~ APE 1540~- a commercially available colloidal
dispersion comprising about 40% antimony
pentoxide in a polyester resin derived
predominantly from isophthalic acid.
ADP-480~- a commercially available colloidal
dispersion comprising about 75% antimony
- 1 9 -
RD-18473
-- 1 336$~4
pentoxide coated with an amine powder and
dispersed in toluene.
Additional components:
DOTBP - dioctyl tetrabromophthalate.
Brominated epoxy - a product prepared by the
reaction of a mixture of bisphenol A and
2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane
with epichlorohydrin, containing about 21%
bromine.
Phosphatotitanate - a commercially available
compound of formula VII wherein R3 is allyl,
R4 is methylene, R5 is ethyl, R6 is octyl and
x is 0.
Examples 2-8
A series of curable varnish compositions was
prepared by dissolution of the ingredients in toluene to a
total solids concentration of 35-40%. The compositional
data for said varnish compositions are given in Table I.
Except for phosphatotitanate and basic nitrogen, all units
are percent by weight.
-20-
TABLE I ~ .
Example
2 3 4 5 6 7 8
Component 1 29.38 37.09 32.3127.3326.81 35.65 36.46
Cam,onent 11 45.70 37.53 40.3445.5544.69 44.57 45.58
Component 111:
EPN 1138 ----- ----- 4.034.56 4.47 ll.45 4.56
Bisphenol A diglycldyl ether 5.44 7.21 ----- ----- ~----- ----- -----
Component IV 5.01 4.26 8.074.56 4.47 8.92 9.12
Component V:
2-heptadecylImldazole0.87 0.70 ----- 0.73 0.72 ----- -----
lmidazole-amlne mixture ----- ----- 0.56 ----- ----- 0.62 0.64
Component Vl:
Zinc bls~acetylacetonate~ 2.07 1.711.62 1.56 1.53 ----- -----
I Zinc stearate ----- ----- 1.61 ----- ----- 1.78 1.82
Component Vll
APE 1540 7.18 7.16 6.94 ----- ----- _____ _____
I ADP 480 ----- ----- ----- 3.97 3.90 4.01 1.82
DOTBP 4.35 4.34 4.522.63 ----- ----- -----
Brominated epoxy __-__ _____ _____9.11 _____ _____ _____
Phospllatotitanate, parts/100 parts
resinous ccm,onont 0.5n 0.4 0 400.47 0.46 0.45 0.46
Bromine 6.9 8.3: 7 577.80 7.50 6.26 6.20
Zlnc 0.5 0.4 0.570.39 0.38 0.18 0.19
Antimony pentoxlde 2.u 2.'l 2. 3.0 2.9 3.0 1.37 CS~
Baslc nltrogen, meq./100 parts 5.~ 4.~ 9.~ 5.5 5.4 9.9 10.1 r~
o~
~,
~D-18473
1 336464
Swatches of electrical grade woven fiberglass
cloth were dipped into the varnishes of Examples 2-7 and air
dried at elevated temperature to remove solvent and yield
composite prepregs. Copper-clad laminates were then pre-
pared from l-oz. copper foil and 8 plies of the prepregs by
compression molding for 5-10 minutes at 230C and 49.2
kg./cm. . Said laminates were evaluated for flame retard-
:ancy in accordance with Underwriters Laboratories procedure
UL-94. Those prepared from the compositions of Examples 6
and 7 were also evaluated according to various test proce-
dures which form part of military specification MIL-P-13949.
The results are given in Table II.
TA~LE 11
Example
2 3 4 5 6 7
Lam nate thlckness ~less copperl, mm. 1.42 1.40 1.501.56 1.52 1.57
Res n content, X
UL-~4:
FOT, total sec./5 samples 25 27~ 19 27 30 29
Ratlng V-O Y-O V-O V-O V-O V-O
Water ebsnrptlon ~24 hrs. soak
at 23C , S ---- ---- ---- ---- 0.06 0.07
Flexural ~trength, MPa.:
Longltu~lnal ---- ---- ---- ---- 606.7 ----
Cross-sectlonal ---- ---- ---- ~ ---- 379.2 ----
Plexural modulus, GPa.:
Longltudlnal ---- ---- ---- ---- 22.1 ----
Cross-sectlonal ---- ---- ---- ---- 19.3 ----
lzod Impact strength, Joules/m.:
Longltudlnal ---- ---- ---- ---- N0* ----
I Cross-sectlonal ---- ---- ---- ---- 671 ----
Dlelectrlc constant at I MHz.:
Untreated ---- ---- ---- ---- 4.19 3.70
I After 24 hrs. In water at 23C ---- ---- ---- ---- 4.24 3.75
Dlsslpatlon factor at IMHZ.:
Untreated ---- ~--- ~~~~ ~~~~0-01l 0-13 -
After 24 hrs. In water at Z3C ---- ---- ---- ---~0.012 0.16
Parallel dlelectrlc breakdown
strength, kv.:
Short tIme
Untreated ---- -~-- ---- ---- 76 ----
After 48 hrs. In water at 50C ---- ---- ---- ---- 78 79 C~
Step by step
Untreated ---- ---- ---- ---- 73 ---- ~'
After 48 hrs. In water at 50C ---- ---- ---- ---- 64 72
Perpendlcular dlelectrlc breakdown
strength, volts/mll:
Untreated ---- ---- ---- ---- 767 803
After 48 hrs. In water at 50C ---- ---- ---- ---- 783 ---
Peel strength, hg./cm. ---- ____ ____ ____>1.4 ~1.4 ~
Methylene chlorlde reslstance, X absorbed ---- ---- ---- ---- o 1.44 w
*No break.
-- ~ 336464 RD-18473
Example 9
A 75% solution in toluene of the upstaged
composition of Example 1 was prepared and 640 parts thereof
(component I) was combined with 2252 parts of hot toluene,
600 parts of component II, 60 parts of "EPN 1138" (component
III), 120 parts of component IV, 10.2 parts of 2-hepta-
decylimidazole (component V), 24 parts of zinc acetyl-
acetonate (component VI), 42 parts of ADP-480 (component
VII) and 6 parts of phosphatotitanate, to prepare a curable
varnish containing 7.5% bromine, 0.45% zinc, 2.4% antimony
pentoxide and 5.5 milliequivalents of basic nitrogen per 100
parts. Swatches of electrical grade woven fiberglass cloth
were dipped into said varnish and air dried at elevated
temperature to remove solvent and yield composite prepregs.
Copper-clad laminates were then prepared from 10 plies of
the prepregs by compression molding for 10 minutes at -240C
and 18.1 kg./cm.2.
The laminates were subjected to physical testing in
comparison with the following controls, based on the
disclosure of the aforementioned Japanese Patent 58/69052.
Control A - identical to Example 9 except that an
upstaged composition prepared from 66.7 parts of
bisphenol A diglycidyl ether and 33.3 parts of
2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane was
employed and the phosphatotitanate was omitted.
Control B - a curable composition was prepared
from 600 parts of polyphenylene ether, 400 parts
of bisphenol a diglycidyl ether, 73 parts of
m-phenylenediamine, 1 part of triethylamine
hydrochloride and 2252 parts of toluene; a 10- 2
ply laminate was molded at 200C and 28.1 kg./cm.
for one hour. The procedure was essentially that
of Example 2 of the aforementioned Japanese Patent
58/69052.
The test result are given in Table III.
1 336464
RD-18473
TABLE III
Invention Control A Control B
Glass transition 221 220 190
temperature, C
Methylene chloride 0 10 0
resistance, % absorbed
appearance after methylene Good SevereSevere
chloride immersion erosion Whitening
Z-axis expansion, ~ 1.3 4.1 3.4
It is apparent that the upstaged compositions of
this invention, when employed with phosphatotitanates,
afford laminates with properties superior to those of
laminates prepared according to the aforementioned
Japanese Patent 58/69052.
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