U.S. patent application number 09/964119 was filed with the patent office on 2002-06-20 for viscosity modifier for thermosetting resin composition.
Invention is credited to Gan, Joseph.
Application Number | 20020076482 09/964119 |
Document ID | / |
Family ID | 10837313 |
Filed Date | 2002-06-20 |
United States Patent
Application |
20020076482 |
Kind Code |
A1 |
Gan, Joseph |
June 20, 2002 |
Viscosity modifier for thermosetting resin composition
Abstract
A heat curable thermosetting epoxy resin formulation useful for
making prepregs and electrical laminates containing a viscosity
modifier, wherein the viscosity modifier is: (a) an optionally
substituted polymer of a monovinylidene aromatic monomer,
optionally having one or more further unsaturated monomers
copolymerized therewith; (b) an optionally substituted
polyphenylene oxide; or (c) an oxazolidone ring-containing
compound.
Inventors: |
Gan, Joseph; (Strasbourg,
FR) |
Correspondence
Address: |
THE DOW CHEMICAL COMPANY
INTELLECTUAL PROPERTY SECTION
P. O. BOX 1967
MIDLAND
MI
48641-1967
US
|
Family ID: |
10837313 |
Appl. No.: |
09/964119 |
Filed: |
September 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09964119 |
Sep 25, 2001 |
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09370656 |
Aug 6, 1999 |
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Current U.S.
Class: |
427/58 |
Current CPC
Class: |
C08G 18/003 20130101;
C08L 63/00 20130101; Y10T 428/31511 20150401; C08L 63/00 20130101;
C08L 2666/20 20130101 |
Class at
Publication: |
427/58 |
International
Class: |
B05D 005/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 14, 1998 |
GB |
9817799.1 |
Claims
What is claimed is:
1. A thermosetting resin composition comprising a heat-curable
thermosetting resin having a molecular weight of from about 200 to
about 3000, and from about 0.5 to about 40 percent by weight, based
on the resin composition, of a viscosity modifier which is a
thermoplastic resin having a molecular weight of at least about
5000 and a hydroxyl content not exceeding about 0.2 hydroxyl
equivalents per 100 g of the resin composition, wherein the
viscosity modifier is: a) an optionally substituted polymer of a
monovinylidene aromatic monomer and optionally one or more further
unsaturated monomers copolymerized therewith; b) an optionally
substituted polyphenylene oxide; or c) an oxazolidone
ring-containing compound.
2. A method of preparing a thermosetting resin composition, which
method comprises combining a heat-curable thermosetting resin
having a molecular weight of from about 200 to about 3000, with
from about 0.5 to about 40 percent by weight, based on the resin
composition, of a viscosity modifier wherein the viscosity modifier
is a thermoplastic resin having a molecular weight of at least
about 5000 and a hydroxyl content not exceeding about 0.2 hydroxyl
equivalents per 100 g of the resin composition, wherein the
viscosity modifier is: a) an optionally substituted polymer of a
monovinylidene aromatic monomer and optionally one or more further
unsaturated monomers copolymerized therewith; b) an optionally
substituted polyphenylene oxide; or c) an oxazolidone
ring-containing compound.
3. A viscosity modifier for a heat-curable thermosetting resin
composition of a thermoplastic resin wherein the thermoplastic
resin has a molecular weight of at least about 5000, and a hydroxyl
content not exceeding about 0.2 hydroxyl equivalents per 100 g of
the resin composition, and wherein the viscosity modifier
comprises: a) an optionally substituted polymer of a monovinylidene
aromatic monomer, optionally having one or more further unsaturated
monomers copolymerized therewith; b) an optionally substituted
polyphenylene oxide; or c) an oxazolidone ring-containing
compound.
4. A resin composition as claimed in claim 1, wherein the viscosity
modifier is polystyrene, brominated polystyrene, a polyphenylene
oxide, or a brominated polyphenylene oxide.
5. A resin composition as claimed in claim 1, wherein the viscosity
modifier is an oxazolidone ring-containing compound which is the
reaction product of: a) a polyisocyanate having an isocyanate
functionality of from about 1.9 to about 2.1; b) a polyepoxide
having an epoxide functionality of from about 1.9 to about 2.1; and
optionally, c) a chain extender.
6. A resin composition as claimed in claim 5, wherein the
polyisocyanate is
2,4'-methylene-bis(phenylisocyanate)4,4'-methylene-bis(phenylisocyanat-
e), polymeric MDI or toluene diisocyanate, or a mixture of two or
more thereof.
7. A resin composition as claimed in claim 5, wherein the
polyisocyanate compound is employed in an amount of from about 15
to about 43 weight percent, based on the polyepoxide and
polyisocyanate reactants.
8. A resin composition as claimed in claim 7, wherein the
polyisocyanate compound is employed in an amount of from about 20
to about 40 weight percent, based on the polyepoxide and
polyisocyanate reactants.
9. A resin composition as claimed in claim 8, wherein the
polyisocyanate compound is employed in an amount of from about 25
to about 35 weight percent, based on the polyepoxide and
polyisocyanate reactants.
10. A resin composition as claimed in claim 5, wherein the
polyepoxide is a diglycidyl ether of a dihydric phenol or a
diglycidyl ester of a dicarboxylic acid.
11. A resin composition as claimed in claim 5, wherein the
polyepoxide is a diglycidyl ether of bisphenol-A, a diglycidyl
ether of bisphenol-F, a brominated diglycidyl ether of bisphenol-A,
a brominated diglycidyl ether of bisphenol-F or a mixture of two or
more thereof.
12. A resin composition as claimed in claim 5, wherein the chain
extender is a dihydric phenol, a halogenated dihydric phenol, a
dicarboxylicacid, a diamine, or an alkanolamine.
13. A resin composition as claimed in claim 5, wherein the amount
of the oxazolidone ring-containing compound viscosity modifier is
from about 0.5 to about 20 percent in weight, based on the weight
of the resin composition.
14. A resin composition as claimed in claim 5, wherein the
oxazolidone ring-containing compound viscosity modifier is an
epoxy-terminated polyoxazolidone and the amount of the
epoxy-terminated polyoxazolidone is from about 0.5 to about 20
percent by weight, based on the weight of the resin
composition.
15. A resin composition as claimed in claim 1, wherein the
heat-curable thermosetting resin is an epoxy-terminated resin
having a molecular weight of from about 200 to about 3000.
16. A resin composition as claimed in claim 15, wherein the
epoxy-terminated resin has a molecular weight of from about 200 to
about 1500.
17. A resin composition as claimed in claim 1, wherein the
heat-curable thermosetting resin is a resin derived from the
reaction of a polyepoxide with a polyisocyanate, and having an EEW
of from about 200 to about 600.
18. A resin composition, as claimed in claim 1, wherein the resin
composition also comprises a chain extender, in an amount of from
about 0.2 to about 0.5 equivalents of chain extender per epoxy
equivalent in the epoxy-terminated resin.
19. A resin composition as claimed in claim 1, wherein the
heat-curable resin composition contains boric acid or a boron oxide
as an inhibitor.
20. A resin composition as claimed in claim 1, wherein the
composition also comprises an accelerator.
21. A resin composition as claimed in claim 1, wherein the
composition also comprises a curing agent.
22. A resin composition as claimed in claim 21, wherein the curing
agent is a polyamine, polyamide, polyanhydride, polyphenol, or a
polyacid compound.
23. A thermoplastic oxazolidone ring-containing compound having a
molecular weight of at least about 5000, which is the reaction
product of: a) from about 20 to about 43 weight percent, based on
the polyepoxide and polyisocyanate reactants, of a polyisocyanate
having an isocyanate functionality of from about 1.9 to about 2.1;
b) from about 80 to about 57 weight percent, based on the
polyepoxide and polyisocyanate reactants, of a polyepoxide having
an epoxide functionality of from about 1.9 to about 2.1; and
optionally, c) a chain extender.
24. An oxazolidone ring-containing compound as claimed in claim 23
wherein the chain extender is a dihydric phenol, a halogenated
dihydric phenol, a dicarboxylicacid, a diamine, or an
alkanolamine.
25. An oxazolidone ring-containing compound as claimed in claim 23,
wherein the polyepoxide is a diglycidyl ether of a dihydric phenol
or a diglycidyl ester of a dicarboxylic acid.
26. An oxazolidone ring-containing compound as claimed in claim 25,
wherein the polyepoxide is a diglycidyl ether of bisphenol-A, a
diglycidyl ether of bisphenol-F, a brominated diglycidyl ether of
bisphenol-A, a brominated diglycidyl ether of bisphenol-F or a
mixture of two or more thereof.
27. A thermosetting resin composition as claimed in claim 5,
wherein the said viscosity modifier composition comprises an
oxazolidone ring-containing compound as defined in claim 23, in an
amount such as to provide from about 0.01 to less than about 0.5
equivalents of oxazolidone, per kilogram of the thermosetting resin
composition.
28. A thermosetting resin composition as claimed in claim 27,
wherein the said viscosity modifier composition comprises an
oxazolidone ring-containing compound as defined in claim 23, in an
amount such as to provide from about 0.05 to about 0.25 equivalents
of oxazolidone, per kilogram of the thermosetting resin
composition.
29. A process for preparing a prepreg, which process comprises
impregnating a reinforcing web with an epoxy resin composition, a
hardener for the epoxy resin and an organic solvent, and heating
the web to a temperature sufficient to partially react the epoxy
resin with the hardener, characterized in that the epoxy resin
composition is a resin composition as claimed in claim 1.
30. A process for preparing an electrical laminate which process
comprises laminating at least one layer of a prepreg prepared by a
method as defined in claim 29 with electrically conductive material
and heating the so prepared laminate to cure the epoxy resin.
31. A process for preparing a cured thermoset resin, which process
comprises heating and thereby curing a thermosetting resin
composition comprising a heat-curable thermosetting resin having a
molecular weight of from about 200 to about 3000, and from about
0.5 to about 40 percent by weight, based on the resin composition,
of a viscosity modifier which is a thermoplastic resin having a
molecular weight of at least about 5000 and a hydroxyl content not
exceeding about 0.2 hydroxyl equivalents per 100 g of the resin
composition, wherein the viscosity modifier is: a) an optionally
substituted polymer of a monovinylidene aromatic monomer and
optionally one or more further unsaturated monomers copolymerized
therewith; b) an optionally substituted polyphenylene oxide; or c)
an oxazolidone ring-containing compound and thermosetting resin
composition.
32. An article comprising a cured or B-staged resin composition as
claimed in claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to resin formulations, and in
particular to curable thermosetting resin formulations such as
epoxy resins. In particular embodiments, the invention relates to
resin formulations useful for making prepregs and electrical
laminates.
[0002] It is known to make prepregs, electrical laminates and other
composites from a fibrous substrate and an epoxy-containing matrix
resin. Such processes usually contain the following steps:
[0003] (1) an epoxy-containing formulation is applied to a
substrate by rolling, dipping, spraying, other known techniques
and/or combinations thereof. The substrate is typically a woven or
nonwoven fiber mat containing, for instance, glass fibers or
paper.
[0004] (2) The impregnated substrate is "B-staged" by heating at a
temperature sufficient to draw off solvent in the epoxy formulation
and optionally to partially cure the epoxy formulation, so that the
impregnated substrate can be handled easily. The "B-staging" step
is usually carried out at a temperature between 90.degree. C. and
210.degree. C. and for a time between 1 minute and 15 minutes. The
impregnated substrate that results from B-staging is called a
prepreg. The temperature is most commonly 100.degree. C. for
composites and 130.degree. C. to 180.degree. C. for electrical
laminates.
[0005] (3) One or more sheets of prepreg are stacked in alternating
layers with one or more sheets of a conductive material, such as
copper foil, if an electrical laminate is desired.
[0006] (4) The laid-up sheets are pressed at high temperature and
pressure for a time sufficient to cure the resin and form a
laminate. The temperature of lamination is usually between
100.degree. C. and 230.degree. C., and is most often between
165.degree. C. and 190.degree. C. The lamination step may also be
carried out in two or more stages, such as a first stage between
100.degree. C. and 150.degree. C. and a second stage at between
165.degree. C. and 190.degree. C. The pressure is usually between
50 N/cm.sup.2 and 500 N/cm.sup.2. The lamination step is usually
carried on for 10 to 500 minutes, and most often for 45 to 300
minutes. The lamination step may optionally be carried out at
higher temperatures for shorter times (such as in continuous
lamination processes) or for longer times at lower temperatures
(such as in low energy press processes).
[0007] (5) Optionally, the resulting copper-clad laminate may be
post-treated by heating for a time at high temperature and ambient
pressure. The temperatures of post-treatment are usually between
120.degree. C. and 250.degree. C. The post-treatment time usually
is between 30 minutes and 12 hours.
[0008] Electrical laminates and processes by which they are made,
are described in greater detail in numerous references, such as
U.S. Pat. No. 5,314,720 (May 24, 1994) and Delmonte, Hoggatt &
May; "Fiber-reinforced Epoxy Composites," Epoxy Resins, Chemistry
and Technology (2d Ed.) at 889-921 (Marcel Dekker, Inc. 1988).
[0009] The formulations that are used in such processes typically
contain:
[0010] (1) an epoxy resin;
[0011] (2) a curing agent, for example a polyamine such as
dicyandiamide, a polyanhydrides such as a styrene/maleic anhydride
copolymer, or a polyphenol or a mixture of two or more curing
agents;
[0012] (3) a catalyst to promote the reaction of the resin and the
curing agent, such as 2-methylimidazole, 2-ethyl,4-methylimidazole,
2-phenylimidazole, or a mixture of two or more catalysts; and
[0013] (4) optionally, from 0 to 50 weight percent of a volatile
organic solvent such as a ketone, a glycol ether,
dimethylformamide, xylene or a mixture of two or more organic
solvents.
[0014] Viscosity is critical in laminate making processes. See, for
example, Delmonte, Hoggatt & May at 903. High viscosity resins
distort the position of fibers in the substrate, and are difficult
to impregnate into the substrate. However, if the viscosity of the
resin is too low, the resin tends to flow out of the prepreg stack
during the lamination process, resulting in a laminate which is
deficient in resin, such that it is very difficult to obtain a
homogeneous thickness over the whole laminate. The ability to
control the thickness of laminates is important in some
applications. For example, recently, a new chip memory module
technology has been developed to achieve faster bus/substrate speed
(>300 MHz) to better utilize the capabilities of faster CPUs.
The critical need in this application is for extremely tight
control of the dielectric constant which translates into much
better thickness control of the laminate layers.
[0015] Formulations which contain liquid epoxy resins and a chain
extender have not commonly been used in laminating processes,
because their viscosity in the treater and prepreg is often too
low. The formulations run and drip in the treater before the
B-stage is complete. Furthermore, the formulations flow too much
after the prepreg is put into the laminating press. The resin is
forced out of the laminate and into the press, and the resulting
laminate is too thin.
[0016] Extra catalysts may be added to the formulation to encourage
quick reaction of epoxy resin and chain extender in the treater, so
that higher molecular weight advanced resins are produced before
dripping occurs. However, those catalysts also accelerate curing of
the resin with the curing agent. It is difficult to prevent the
viscosity from building too high for effective lamination.
Moreover, formulations which contain too much catalyst have a short
shelf- or pot-life, and the resulting prepregs have a short
shelf-life.
[0017] It is known to incorporate thermoplastic resins in
electrical laminate formulations to reduce the resin flow out
(waste) by increasing the melt viscosity of the B-staged materials
of the prepregs during the lamination process. A high molecular
weight polymer obtained by an advancement reaction using
bisphenol-A and the diglycidylether of bisphenol-A and is sold
commercially by Phenoxy Associates (USA), under the trademark PKHH.
This material is frequently used to reduce resin flow-out by
increasing the melt viscosity of the B-staged materials without
shortening the gel time. However, when PKHH is used, the Tg of the
resulting laminate is adversely affected. In the case of acid
anhydride cured systems (for example as disclosed in
PCT/US98/01041), the secondary hydroxyl groups present in PKHH
react easily at room temperature with the acid anhydride to
generate acid groups in the presence of amine catalysts. These acid
groups react with the epoxy groups and the pot-life/gel time of the
formulations are considerably reduced and is not desirable.
[0018] There are three end products (conventionally referred to as
polyoxazolidones) which can be obtained in the condensation
reaction of polyisocyanates with polyfunctional epoxides, namely
isocyanate-terminated polyoxazolidones, linear polyoxazolidones,
and epoxy-terminated polyoxazolidones. These three possible end
products and various methods for their production, are described in
U.S. Pat. No. A 5,112,932 and in the references referred to
therein, all of which are incorporated herein by reference. Epoxy
terminated polyoxazolidones are prepared by reacting an epoxy resin
with a polyisocyanate compound using stoichiometric excess of epoxy
resin (isocyanate/epoxide ratio lower than 1).
[0019] U.S. Pat. No. A 4,070,416 (Hitachi) describes a process for
producing thermosetting resins by mixing one equivalent or more of
polyfunctional isocyanate per one equivalent of a polyfunctional
epoxide in the presence of a tertiary amine, morpholine derivatives
or imidazole as catalysts. The catalyst is used within a range of
0.1 to 2 weight percent, based on the combined weight of the
reactants. The reaction temperature of 130.degree. C. or lower is
said to result in the formation of mainly isocyanurate rings,
whereas it is assumed that oxazolidone rings should be mainly
formed at temperature above 130.degree. C. The resins produced are
said to exhibit excellent electrical and mechanical properties and
high thermal stability. They are said to have various applications
as heat resistance insulation varnishes, casting resins,
impregnation resins, molding resins for electrical parts,
adhesives, resins for laminating boards, resins for printed
circuits etc.
[0020] EP A 0,113,575 discloses powder coating compositions
comprising epoxy terminated polyoxazolidone resins prepared by
reacting a diepoxide and a diisocyanate in amounts which provide a
ratio of epoxide equivalents to isocyanate equivalents of from
1.1:1 to 10:1 and curing agents. The polyoxazolidone resins are
said to have comparatively high glass transition temperatures and
provide coatings of improved resistance to cathodic disbandment.
The coating compositions are applied by fluidized bed sintering or
electrostatic spray methods.
[0021] Self thermosetting compositions of polyisocyanates and
polyepoxides are described in U.S. Pat. No. A 4,564,651 (Markert)
and U.S. Pat. No. A 4,631,306 (Markert) which disclose a method for
the preparation of reaction resin molded materials and molded
materials for insulating components, respectively containing
oxazolidone and isocyanurate rings by mixing a polyepoxide and a
polyisocyanate to from a resin mixture having a viscosity up to
7000 mpa.multidot.s at 25.degree. C. and the mole ratio of epoxy to
isocyanate groups of 1:1 to 5:1; reacting the resin mixture in the
presence of an imidazole or tertiary amine catalyst at elevated
gelling temperature of from 80.degree. C. to 130.degree. C. to form
a cross linked polymer; and heating the cross linked polymer to
130.degree. C. to 200.degree. C. to cause post hardening and
produce a molded material. The molded materials are reported to
exhibit improved mechanical properties.
[0022] U.S. Pat. No. A 3,334,110 (Schramm) discloses a method for
preparing epoxy terminated polyoxazolidones by reacting a
polyisocyanate with a polyepoxide in the presence of a catalyst
mixture comprising an alcohol and tertiary amine or a quaternary
ammonium salt. The epoxy terminated polyoxazolidones can be cured
with epoxy curing catalysts or reacted with epoxy hardeners to give
a variety of products useful in the fields of coatings, laminating,
bonding, molding, foams, etc.
[0023] U.S. Pat. No. A 4,066,628 (Ashida et. al.) discloses a
process for preparing polyoxazolidones by reacting an organic
isocyanate with an epoxide in the presence of dialkyl zinc, zinc
carboxylate, organozinc chelate compound or trialkyl aluminum as
the catalyst. Polyoxazolidones prepared by this process are useful
starting materials for the manufacture of a wide variety of
products including foams, coatings, adhesives, elastomers and the
like.
[0024] Although numerous processes for the preparation of
polyoxazolidones are described in the literature, there is no
disclosure nor suggestion in the known art that epoxy terminated
polyoxazolidones would be useful as viscosity-modifying additives,
to be added in relatively small amounts to other resin
compositions, in particular to heat curable thermosetting resins
such as epoxy resins, in order to improve their viscosity
properties, whilst maintaining an adequate Tg in the final cured
resin.
[0025] EP B 0,695,316 and U.S. Pat. No. A 5,449,737 (CIBA) also
disclose the preparation of oxazolidone-containing base resins.
[0026] Although both of these CIBA references refer in general
terms to materials having an epoxy equivalent weight (EEW) of from
200 to 10,000, they are concerned with "base resins", intended to
be cured with a crosslinking agent, and for such purposes, a
material having a low EEW (for example no more than 500) would
invariably be used. If a material with a high equivalent weight (in
particular, higher than 500) is used as a base resin in the
production of laminates, the resin fails to wet out the glass
fibers, and is therefore unsatisfactory. All of the Examples in
both of the CIBA patents use an amount of isocyanate of no more
than 18.7% (TDI) for the preparation of the base resin, and result
in materials having an EEW of no more than 500. In practice
therefore, the skilled addressee following the teaching of these
references would not prepare a material having a molecular weight
of 5000 or more.
SUMMARY OF THE INVENTION
[0027] We have now discovered that certain low hydroxyl content
high molecular weight resins are able to act as viscosity
modifiers, and provide higher melt viscosity to the B-staged
material at without adverse effect on varnish and prepreg gel
times, pot-life and shelf-life.
[0028] We have also discovered certain new,
oxazolidone-ring-containing materials having a molecular weight
which is significantly higher than those envisaged in EP A
0,695,316 and U.S. Pat. No. A 5,449,737, which are useful as such
viscosity modifiers.
[0029] We have also found that prepregs incorporating the viscosity
modifiers exhibit better storage stability and higher laminate Tg
than systems employing PKHH. In particular, we have found that the
Tg of laminates obtained using PKHH exhibit lower Tg when the
prepregs were stored over a period of time whereas prepregs
prepared using the viscosity modifiers of the present invention
exhibited a lower drop in laminate Tg after same period of
storage.
[0030] Accordingly, in a first aspect of the present invention,
there is provided the use as a viscosity modifier for a
heat-curable thermosetting resin composition of a thermoplastic
resin wherein the thermoplastic resin has a molecular weight of at
least about 5000, and a hydroxyl content not exceeding about 0.2
hydroxyl equivalents per 100 g of the resin composition, and
wherein the viscosity modifier is:
[0031] a) an optionally substituted polymer of a monovinylidene
aromatic monomer, optionally having one or more further unsaturated
monomers copolymerized therewith;
[0032] b) an optionally substituted polyphenylene oxide; or
[0033] c) an oxazolidone ring-containing compound.
[0034] The viscosity modifier may be, for example, polystyrene,
brominated polystyrene, a polyphenylene oxide, or a brominated
polyphenylene oxide. Preferably however, the viscosity modifier is
an oxazolidone ring-containing compound which is obtained by the
reaction of:
[0035] a) a polyisocyanate having an isocyanate functionality of
from about 1.9 to about 2.1;
[0036] b) a polyepoxide having an epoxide functionality of from
about 1.9 to about 2.1, and optionally; and
[0037] c) a chain extender,
[0038] wherein the oxazolidone ring-containing compound has a
molecular weight of at least about 5000.
[0039] In a second aspect of the present invention there is
provided a thermosetting resin composition comprising a
heat-curable thermosetting resin having a molecular weight of from
about 200 to about 3000, and from about 0.5 to about 40 percent by
weight, based on the resin composition, of a viscosity modifier
which is a thermoplastic resin having a molecular weight of at
least about 5000 and a hydroxyl content not exceeding about 0.2
hydroxyl equivalents per 100 g of the resin composition, wherein
the viscosity modifier is:
[0040] a) an optionally substituted polymer of a monovinylidene
aromatic monomer and optionally one or more further unsaturated
monomers copolymerized therewith;
[0041] b) an optionally substitute polyphenylene oxide; or
[0042] c) an oxazolidone ring-containing compound.
[0043] In a further aspect of the present invention there is
provided a method of preparing a thermosetting resin composition,
which method comprises combining a heat-curable thermosetting resin
having a molecular weight of from about 200 to about 3000, with
from about 0.5 to about 40 percent by weight, based on the resin
composition, of a viscosity modifier wherein the viscosity modifier
is a thermoplastic resin having a molecular weight of at least
about 5000 and a hydroxyl content not exceeding about 0.2 hydroxyl
equivalents per 100 g of the resin composition, wherein the
viscosity modifier is:
[0044] a) an optionally substituted polymer of a monovinylidene
aromatic monomer and optionally one or more further unsaturated
monomers copolymerized therewith;
[0045] b) an optionally substituted polyphenylene oxide; or
[0046] c) an oxazolidone ring-containing compound.
[0047] The thermosetting resin composition is preferably an epoxy
resin composition, and may preferably also comprise a hardener for
the epoxy resin and/or an organic solvent. Optionally, the
composition may also comprise one or more pigments, fillers,
stabilizers or other conventional epoxy resin additives.
[0048] The amount of the oxazolidone ring-containing compound in
the epoxy resin composition is preferably such as to provide from
about 0.01 to about 1 equivalents of oxazolidone, preferably from
about 0.02 to about 0.75 equivalents of oxazolidone, more
preferably about 0.02 to about 0.5 equivalents of oxazolidone, per
kilogram of resin. A third aspect of the present invention is a
process for making a composite, particularly an electrical
laminate, using an epoxy resin composition as described above.
[0049] In a fourth aspect of the present invention, there is
provided a thermoplastic oxazolidone ring-containing compound
having a molecular weight of at least about 5000, which is the
reaction product of:
[0050] a) from about 20 to about 43 weight percent, based on the
polyepoxide and polyisocyanate reactants, of a polyisocyanate
having an isocyanate functionality of from about 1.9 to about
2.1;
[0051] b) from about 80 to about 57 weight percent, based on the
polyepoxide and polyisocyanate reactants, of a polyepoxide having
an epoxide functionality of from about 1.9 to about 2.1; and
optionally,
[0052] c) a chain extender.
DETAILED DESCRIPTION OF THE INVENTION
[0053] The polyepoxide compound useful in the preparation of the
viscosity modifier is suitably a compound which possesses an
average of from about 1.9 to about 2.1 1,2-epoxy groups per
molecule. In general, the polyepoxide compound is saturated or
unsaturated aliphatic, cycloaliphatic, aromatic or heterocyclic
compound which possesses more than one 1,2-epoxy group. The
polyepoxide compound can be substituted with one or more
substituents which are non reactive with the isocyanate groups such
as lower alkyls and halogens. Such polyepoxide compounds are well
known in the art. Illustrative polyepoxide compounds useful in the
practice of the present invention are described in the Handbook of
Epoxy Resins by H. E. Lee and K. Neville published in 1967 by
McGraw Hill, New York and U.S. Pat. No. 4,066,628 both incorporated
herein by reference.
[0054] Examples of suitable aromatic polyepoxides are bisphenol-A,
bisphenol-F, bisphenol-AD, bisphenol-S, tetramethyl bisphenol-A,
tetramethyl bisphenol-F, tetramethyl bisphenol-AD, tetramethyl
bisphenol-S, tetrabromobisphenol-A, tetrachlorobisphenol-A,
biphenols such as 4,4'-biphenol or
3,3',5,5'-tetramethyl-4,4'-biphenol, and dihydroxynaphthalene.
[0055] Examples of suitable aliphatic polyepoxides are diglycidyl
esters of hexahydrophthalic acid and diglycidyl esters of
dicarboxylic acids, epoxidized polybutadiene, epoxidized soyabean
oil, and epoxidized diols.
[0056] Cycloaliphatic epoxides include, for example,
3,4-epoxy-6-methylcyclohexyl carboxylate and 3,4-epoxycyclohexyl
carboxylate.
[0057] Preferred polyepoxides are glycidyl compounds of
bisphenol-A, of bisphenol-F, of tetrabromobisphenol-A and of
3,3',5,5'-tetramethyl-4,4-bi- phenol. Mixtures of any two or more
polyepoxides can also be used in the practice of the present
invention.
[0058] The polyisocyanate compound useful in the practice of the
present invention may be represented by the following general
formula:
(O.dbd.C.dbd.N).sub.m--R
[0059] wherein R is substituted or unsubstituted aliphatic,
aromatic or heterocyclic polyvalent group and m has an average
value of from about 1.9 to about 2.1. Examples of suitable
polyisocyanates are the difunctional isocyanate disclosed in WO A
9,521,879 incorporated herein by reference. Preferred examples are
2,4'-methylene bis(phenylisocyanate) and 4,4'-methylene
bis(phenylisocyanate) (MDI) and isomers thereof, higher functional
homologs of MDI (commonly designated as "polymeric MDI"), toluene
diisocyanate (TDI) such as 2,4-toluene diisocyanate and 2,6-toluene
diisocyanate, m-xylylene diisocyanate, hexamethylene diisocyanate
(HMDI) and isophoronediisocyanate. Particularly preferred
polyisocyanates are 2,4'-methylene bis(phenylisocyanate) and
4,4'-methylene bis(phenylisocyanate). Mixtures of any two or more
polyisocyanates can also be used.
[0060] A suitable catalyst may be employed to facilitate reaction
of the polyepoxide compound with the polyisocyanate compound.
Examples of suitable catalysts include zinc carboxylate, organozinc
chelate compound, trialkyl aluminum, quaternary phosphonium and
ammonium salts, tertiary amines and imidazole compounds. The
preferred catalysts are imidazole compounds and azo compounds.
Particularly, preferred catalysts are 2-phenylimidazole
2-methylimidazole, 1 methylimidazole, 2-methylimidazole,
4,4'-methylene methylimidazole), 1,5-diazabicyclo[4.3.0] non-5-en,
1,4-diazabicyclo[2.2.2] octane and 1,8-diazabicyclo[5.4.0]
undec-7-en.
[0061] The catalyst is generally employed in an amount of from
about 0.01 to about 2; preferably about 0.02 to about 1, most
preferably about 0.02 to about 0.1, weight percent based on the
combined weight of the polyepoxide compound and polyisocyanate
compound used.
[0062] The polyisocyanate compound is generally employed in an
amount of from about 15 to about 43, preferably about 20 to about
43, more preferably about 20 to about 40, most preferably about 25
to about 35, weight percent, based on the polyepoxide and
polyisocyanate reactants.
[0063] The polyepoxide compound is generally employed in an amount
of from about 85 to about 57, preferably about 80 to about 57, more
preferably about 80 to about 60, most preferably about 75 to about
65, weight percent, based on the polyepoxide and polyisocyanate
reactants.
[0064] The reaction of the polyepoxide with the polyisocyanate is
usually conducted at a temperature of from about 100.degree. C. to
about 240.degree. C., preferably from about 120.degree. C. to about
230.degree. C., more preferably from about 130.degree. C. to about
220.degree. C., most preferably from about 140.degree. C. to about
210.degree. C.
[0065] The polyoxazolidone-containing viscosity modifier can be
produced via either a batch reactor or an extruder. The extrusion
products exhibit lower polydispersity and lower gel particle
content verses the batch reactor-produced materials. The resident
time in an extruder depends on the temperature of the extrusion
temperature, the size of the extruder and the catalyst levels.
[0066] In the production of oxazolidone ring-containing resins via
batch reactor, the catalyst is usually added to the reaction vessel
containing the polyepoxide prior to the start of the addition of
polyisocyanate compound. The catalyst can be dissolved in a
suitable solvent prior to the addition to the polyepoxide to
improve homogenization if desired. The temperature at which the
catalyst is added is not critical. In general the catalyst is added
at a temperature lower than the reaction temperature. The
temperature is then raised and the reaction temperature maintained
while the controlled addition of the polyisocyanate to the mixture
of the catalyst and the polyepoxide is started. The polyisocyanate
addition time will depend on the physical characteristics of the
reactor, e.g., stirrer size, and heat transfer characteristics, but
usually, the polyisocyanate is added to the reaction vessel within
a period of time of from about 3 to about 300, preferably about 5
to about 240, more preferably about 10 to about 180, most
preferably about 20 to about 150 minutes, while maintaining the
reaction temperature. The reaction temperature is maintained after
the complete addition of the polyisocyanate for a period of time of
from about 5 to about 180, preferably about 15 to about 120, most
preferably about 30 to about 90 minutes.
[0067] In general, the reaction of the polyepoxide compound and the
polyisocyanate compound is preferably conducted neat, that is, in
the absence of a solvent or other liquid reaction diluent, although
the reaction may be carried out in the presence of a polar solvent
such as DMF, NMP and DMSO.
[0068] The optional chain extender employed in the production of
the polyoxazolidone compound is one which is able to increase the
molecular weight of the polyoxazolidone compound. Preferred chain
extenders are dihydric phenols, halogenated dihydric phenols,
dicarboxylic acids, diamines, aminoamides and alkanolamines.
[0069] Suitable dicarboxylic acid chain extenders are compounds of
the formula
R--(COOH).sub.u
[0070] wherein R is a C.sub.1-40 hydrocarbyl moiety optionally
containing oxygen along the backbone, and u is from about 1.9 to
about 2.1. Examples are succinic acid, glutaric acid, adipic acid,
oxalic acid, phthalic acid, hexahydrophthalic acid, maleic acid,
citraconic acid, itaconic acid, dodecenylsuccinic acid and
alkylated endoalkylenetetrahydrophthalic acid, and half esters
obtained from the reaction of a polyol with an acid anhydride.
[0071] The term hydrocarbyl as employed herein means any aliphatic,
cycloaliphatic, aromatic, aryl substituted aliphatic or
cycloaliphatic, or aliphatic or cycloaliphatic substituted aromatic
groups.
[0072] Other suitable chain extenders useful in the practice of the
present invention are diamines and aminoamides, i.e., amine- or
amino amide-containing compounds having two N--H bonds capable of
reacting with an epoxy group. Such compounds useful in the present
invention include, for example, di-secondary amines of the general
formula R--NH--R'--NH--R" wherein R, R' and R" are alkyl,
cycloalkyl or aryl moieties; and heterocyclic di-secondary amines
wherein one or both of the N atom is part of a nitrogen-containing
heterocyclic compound such as: 1
[0073] For reactivity reasons, and in order to control the epoxy
advancement reaction with the di-functional amines more
effectively, di-secondary amines or primary amines having
sterically hindered amine groups are preferred as, for example,
2,6-dimethyl cyclohexylamine or 2,6-xylidene
(1-amino-2,6-dimethylbenzene).
[0074] Amino amide-containing compounds useful as advancement
monomers in the present invention include for example derivatives
of carboxylic and amides as well as derivatives of sulfonic acid
amides having additionally one primary or two secondary amino
groups. Preferred examples of such compounds are amino-aryl
carboxylic acid amides and amino-arylsulfonamides. A preferred
compound of this group is, for example, sulphanilamide (4-amino
benzylsulfonic acid amide).
[0075] Other suitable examples are piperazine and substituted
piperazine such as 2-methyl piperazine, monoethanolamine, and
piperidin-4-carbonic acid.
[0076] The chain extender is particularly preferably a phenolic
compound, containing on average more than about 1 and less than
about 3, preferably from about 1.8 to about 2.2 and more preferably
about 2 active hydrogen (e.g., phenolic hydroxyl) groups per
molecule.
[0077] The most preferred chain extenders are dihydroxy phenols.
Non-limitative examples of the phenol compounds are
2,2-bis(3,5-dibromo-4-hydroxyphenyl) propane;
2,2-bis(4-hydroxyphenyl) propane;
2,2-bis(3,5-dichloro-4-hydroxyphenyl) propane; bis(4-hydroxyphenyl)
methane; 1,1-bis(4-hydroxyphenyl)-1-phenyl ethane;
1,1'bis(2,6-dibromo-3,5-dimethyl-4-hydroxyphenyl) propane;
bis(4-hydroxyphenyl) sulfone; bis(4-hydroxyphenyl) sulfide;
resorcinol, hydroquinone, tetramethylbisphenol-A,
tetramethylbisphenol-AD and tetramethylbisphenol-S. Preferred
dihydroxy phenolic compounds are 2,2-bis(4-hydroxyphenol) propane
(bisphenol-A), and 2,2-bis(4-hydroxy-3,5-dibromophenyl)
propane.
[0078] When the phenolic chain extender is non-halogenated, its
molecular weight is preferably at least about 110 and more
preferably at least about 185. The molecular weight is preferably
no more than about 800, more preferably no more than about 500, and
most preferably no more than about 250. For halogenated phenolic
chain extenders, the formula weight of non-halogen atoms in the
chain extender preferably meets the foregoing preferred
limitations, and the total molecular weight is preferably within
the preferred embodiments plus the formula weight of the
halogen.
[0079] The quantity of chain extender employed in the production of
the viscosity modifier is preferably such that the equivalent ratio
of epoxy compound to chain extender is from about 1.5 to about
0.85, preferably from about 1.3 to about 0.9, more preferably from
about 1.2 to about 0.95.
[0080] The polyoxazolidone compounds are used in accordance with
the invention as viscosity modifying additives to improve the
viscosity characteristics of curable thermosetting resin
formulations such as epoxy-resins, in particular in the manufacture
of prepregs and laminates, in particular electrical laminates. The
compositions may also be used in encapsulation, coating and
structural composite applications.
[0081] The thermosetting resin into which the viscosity modifier is
incorporated is preferably an epoxy resin, more preferably a
diglycidyl ether of bisphenol-A or a diglycidyl ether of a
halogenated bisphenol-A. Other useful low-viscosity epoxy resins
are glycidyl ether derivatives of
1,1,1-tris-(hydroxyphenyl)-alkanes and halogenated variations
thereof. Examples of suitable epoxy resins and processes to make
them are also described in H. Lee & K. Neville, Handbook of
Epoxy Resins at 2-1 to 3-20 (McGraw-Hill Book Co. 1967)
incorporated herein by reference.
[0082] The epoxy resin is generally an epoxy-terminated resin
having a molecular weight of from about 200 to about 3000, and may
incorporate flame-retardant groups, for example, halogen (e.g.,
bromine or chlorine) or phosphorous, in the resin.
[0083] In particular, the epoxy resin may be, for example, a resin
derived from the reaction of a polyepoxide with a polyisocyanate,
and having an molecular weight of from about 200 to about 3000 (for
example, as described in U.S. Pat. No. A 5,112,932 incorporated
herein by reference).
[0084] The formulation may comprise a low viscosity resin and low
solvent content, as described in WO A 9,612,751 incorporated herein
by reference.
[0085] The formulation may furthermore comprise styrene maleic acid
anhydride copolymer as the hardener, in order to provide low
dielectric constant properties, as disclosed in PCT/US98/01041
incorporated herein by reference.
[0086] The formulation may also comprise a boron-containing
compound, for example boric acid or a boron oxide, as a cure
inhibitor, as disclosed in GB A 0,458,502 incorporated herein by
reference.
[0087] The heat-curable thermosetting resin preferably further
contains a hardener (otherwise known as a "curing agent"). Suitable
hardeners are multifunctional cross-linkers. Such multifunctional
cross-linkers are described in numerous references, such as Vol. 6,
Encyclopedia of Poly. Sci. & Eng., "Epoxy Resins," at 348-56
(J. Wiley & Sons 1986) incorporated herein by reference.
Multifunctional cross-linkers (as opposed to catalysts and chain
extenders) preferably contain on average more than two active
hydrogen moieties per molecule. For instance, the cross-linker
preferably contains a plurality of secondary amine groups, one or
more primary amine groups, more than 2 phenolic hydroxyl groups, a
plurality of primary amide groups or more than two carboxylic acid
groups.
[0088] Examples of suitable multifunctional cross-linkers known to
be useful as hardeners for epoxy resins, include polyamines,
polyamides, polyanhydrides, polyphenols and polyacids that contain
more than two reactive sites per molecule on average. Preferred
examples of multifunctional cross-linkers include dicyandiamide and
polyphenols such as novolacs. Examples of other multifunctional
cross-linkers which can be used include polyanhydrides as
disclosed, for example, in WO A 9,411,415 (published May 26, 1994)
incorporated herein by reference.
[0089] The quantity of multifunctional cross-linker is preferably
from about 0.1 to about 200 parts by weight, per hundred parts by
weight of the resin composition. When the multifunctional
cross-linker is dicyandiamide, the formulation preferably contains
from about 0.5 to about 8 parts by weight of dicyandiamide per
hundred parts of the resin composition. The polyanhydrides are
preferably used in an amount of from about 20 to about 100 parts,
per hundred parts of the resin composition.
[0090] Epoxy resin composition according to the invention may
optionally contain other additives of a generally conventional
type, such as stabilizers, flame retardants, organic or inorganic
fillers, pigments and wetting agents. Examples of suitable
additives are described in U.S. Pat. No. A 5,066,735 and in C. A.
Epoxy Resins-Second Ed. at 506-512 (Mercel Dekker, Inc., 1988) both
incorporated herein by reference. Particular examples of additives
are methyl-toluene-4-sulfonate, aluminum oxides, phosphonic acid
ester (such as Amgard P45 supplied by Albright and Wilson Ltd.
United Kingdom), and Talc.
[0091] A typical epoxy resin in accordance with the invention is as
follows:
1 % BY WEIGHT Solvent 0-60 Pigment 0-10 Filler 0-20 Stabilizer
0.01-2 Hardener 0.1-60 Catalyst 0.01-5 Chain extender 0-50
Viscosity modifier 0.5-40 Epoxy resin 20-99
[0092] The formulations previously described may be used to make
prepregs and electrical laminates. The formulations advance quickly
and controllably during B-staging to avoid drip, and cure to
provide good laminates in the laminating step.
[0093] Such formulations can be stored for long periods without
loss of stability.
[0094] Preferred embodiments of the invention are illustrated in
the following specific Examples.
[0095] Preparation 1--Preparation of Viscosity Modifier
[0096] General Production Procedure for Oxazolidone Ring-containing
Polyepoxy/Polyisocyanate Copolymer Viscosity Modifier:
[0097] An epoxy resin (D.E.R. 330) was heated to 100.degree. C.
under nitrogen purge in a 1-liter flange-top glass reactor equipped
with an electrically driven mechanical stirrer, air and nitrogen
inlets, sample port, condenser and thermocouple 1500 ppm based on
the total solids (epoxy plus isocyanate) of a reaction catalyst
(1,8-diazabicyclo[5.4.0] undec-7-en, a commercial product
obtainable from Anchor under the trademark AMICURE DBU-E) was added
and the mixture was heated to 150.degree. C. (for MDI) or
180.degree. C. (for TDI).
[0098] An isocyanate (as described in Table 1) was charged into the
epoxy resin via an additional funnel portionwise within a period of
5-240 minutes.
[0099] The heat of reaction caused the reaction temperature to rise
to at least 190.degree. C.-210.degree. C. The reaction temperature
was maintained between 200.degree. C. and 205.degree. C. until all
the isocyanate was added. After addition was complete, the reaction
mixture was kept at 200.degree. C. for 5-60 min. until the
theoretical epoxy equivalent weight (EEW) was reached. The solid
resin was diluted with DMF to 50-55 wt % solid solution and cooled
to room temperature.
[0100] Preparation 2
[0101] General Production Procedure for Viscosity Modifier
Incorporating Chain Extender
[0102] Epoxy/isocyanate copolymers produced in accordance with
Preparation 1 were introduced as a charge into a 1-liter flange-top
glass reactor equipped with an electrically driven mechanical
stirrer, air and nitrogen inlets, sample port, condenser and
thermocouple.
[0103] The chain extender (tetrabromobisphenol-A, Bisphenol-A, or
monoethanolamine) was added to the epoxy/MDI copolymer solution and
additional solvent was added to make a 35 wt % solid solution.
[0104] When a bisphenol chain extender was used, an additional
advancement catalyst (triphenylethyl phosphonium acetate) was added
to the solution. The reaction mixture was heated to 120.degree.
C.-135.degree. C. The temperature of the reaction mixture was
maintained in this range over a period of 2-24 hours until the
epoxy content of the extended on solid was lower than 1%.
[0105] When an amine chain extender was used, the reaction
temperature was between 60.degree. C.-100.degree. C. and no
additional catalyst was needed.
[0106] The reaction mixture was cooled to room temperature, and
additional solvent was added to adjust the solid content to 30 wt
%.
EXAMPLES 1 to 6
[0107] Polyoxazolidone compositions were prepared, using the
general preparation method 1 outlined above, and the ingredients
and amounts set out in Table 1.
[0108] The following analytical methods are used for various
measurements in the examples.
[0109] The standard wet titration method was used to determine
Epoxy Equivalent Weight (EEW).
[0110] Reactivity of the resins was measured according to the
following method: The resin solution was blended with catalyst and
hardened in amounts as shown in Table 3 and Table 9. The mixture
was then reacted on the surface of a hot plate, and reactivity was
reported as elapsed time required for gelation.
[0111] The glass transition temperature of the resin was measured
by DSC at 10.degree. C./min, from 0 to 150.degree. C.
[0112] The melt viscosity was measured according to the ASTM D445
method using an ICI cone and plate viscometer.
[0113] Weight average molecular weight (M.sub.w) was measured by
GPC using DMF as solvent.
[0114] Physical properties of the compositions are also shown in
Table 1.
2 TABLE 1 Example No Comparative Comparative 1 2 3 4 5 6 Example 1
Example 2 COMPOSITION EPOXY RESIN A 70 67 69 69.5 69.5 78 81 PKHH
from Phenoxy Associate co. ISOCYANATE A 30 33 30.5 30.5 ISOCYANATE
B 31 ISOCYANATE C 22 19 DBU, ppm 1500 1000 1500 1500 1500 2000 2000
RESIN CHARACTERISTICS EEW 858 716 721 700 600 435 >10000 MELT
VISCOSITY 43.7 7.68 8.0 7.04 4.8 0.53 Not @200 .degree. C., Pa
.multidot. s measureable Tg, .degree. C. 93 112 91 96 90 86 60 95
Mw 5994 9714 7121 7821 6101 7596 4564 59487 Epoxy Resin A is a
diglycidyl ether of bisphenol-A having an epoxy equivalent weight
between 177 and 189 sold by The Dow Chemical Company under the
trademark D.E.R. 330. ISOCYANATE A is a mixture of 50/50 wt % of
2,4' and 4,4'- methylenebis(phenyisocyanate), sold by The Dow
Chemical Company under the trademark XZ95263.00 ISOCYANATE B is
4,4'- methylenebis(phenyisocyanate), sold by The Dow Chemical
Company under the trademark ISONATE M125 ISOCYANATE C is technical
grade TDI (95% 2,4-and 5% 2,6-isomer) sold by Fluka, under the
desaignation 89871 DBU is a catalyst for the epoxy/MDI reaction
{1,8-diazabicyclo[5.4.0]und- ec-7-en}
[0115] Examples 1 to 6 each have a Tg of at least 86, which is
generally comparable with that of PKHH.
[0116] Each of Examples 1 to 6 have a hydroxyl content which was,
for practical purposes, 0. Comparative Example 1 is intended to
illustrate the type of product obtained following the method
disclosed in Example 6 of EP B 0,695,316, which uses TDI, in an
amount of 18.7%, based on the total amount of TDI/epoxy resin (this
being the highest amount of TDI suggested in the reference). It can
be seen that the molecular weight of the resulting product is less
than 5,000, and the melt viscosity and Tg values of the product are
low. By comparison, Example 6 employs a larger amount of isocyanate
(TDI) which results in a material having a higher molecular weight,
and consequently a higher Tg.
EXAMPLES 7 to 10
[0117] Advanced polyoxazolidone compositions were prepared, by
reacting the polyoxazolidone compositions prepared in Examples 1,
3, 4 and 5 with various chain extenders, namely bisphenol-A, TBBA
(tetrabromobisphenol-A) and monoethanolamine, using the general
preparation method 2 outlined above, and the ingredients and
amounts set out in Table 2. Physical properties of the compositions
are also shown in Table 2.
[0118] The Tg of the resulting materials are all higher than that
of PKHH.
3 TABLE 2 Example No. COMPOSITION 7 8 9 10 Example 1 29.2 Example 3
29.2 Example 4 26.09 Example 5 38.34 TBBA 10.8 10.8 Bisphenol-A
3.91 Monoethanolamine 1.66 DMF 60 60 70 60 Triphenylethylacetate
0.04 0.03 0.09 RESIN CHARACTERISTICS % epoxy (on solid) 0.67 0.70
0.65 0.82 Tg, .degree.C. 130 137 131 111 Hydroxyl content 0.10 0.10
0.11 0.14 (Equiv/100 g solids)
Formulation Examples I to IV
[0119] Epoxy resin varnish compositions were prepared using the
viscosity modifiers prepared according to Examples 2 and 7 and the
ingredients and amounts set out in Table 3. The various components
were mixed at room temperature, using a mechanical stirrer.
Physical properties of the compositions are also shown in Table
3.
[0120] Epoxy resin B is a reaction product of a commercially
available liquid epoxy resin having an EEW of 180 (D.E.R. 383),
tetabromobisphenol-A (TBBA), a commercially available brominated
epoxy resin having an EEW of 441 (D.E.R. 560), and a catalyst
(Triphenylethyl phosphoniumacetate). The designation D.E.R. 383,
D.E.R. 560, etc. are used at various points in the following
description to refer to the commercial designations of various
epoxy resins produced by The Dow Chemical Company.
4 D.E.R. .TM. 383 51.60 TBBA 22.00 D.E.R. .TM. 560 6.40 catalyst
500 ppm based on solid EEW = 363 Glycol ether (Dowanol PM) 10.00
Acetone 8.80 Boric acid solution 1.20 (20 wt % in methanol) TOTAL
100.00
[0121] Stroke cure reactivity at 170.degree. C. was measured by
stroking the formulation onto a hotplate at 170.degree. C., and
measuring the time taken for the composition to gel.
5TABLE 3 weight ratio of components (based on solids) Formulation I
Formulation II Formulation (comparative- (comparative- Formulation
III IV EPOXY RESIN no viscosity PKHH as viscosity Example of
(Example of FORMULATION modifier) modifier) invention) invention)
Epoxy resin B 100.00 100.00 100.00 100.00 DICYANDIAMIDE [10% 3.00
3.00 3.00 3.00 solid in DOWANOL PM .TM./ DMF] Tetraphenolethane
(TPE) 0.80 0.80 0.80 0.80 (SD-357B) Soln. [50% in MEK] (Borden
Chemicals) Glycidyl ether of TPE 2.00 2.00 2.00 2.00 (EPON 1031
.TM.). [69.7% Solid in Acetone] PKHH* Resin Soln. (40% 3.00 in
Dowanol PMA .TM.) Material of Example 7 3.00 (40% solid in DMF)
Material of Example 2 3.00 (50% solid in DMF) 2-PHENYLIMIDAZOL 0.47
0.47 0.47 0.47 (20% solid in methanol) TOTAL (on a solids basis)
106.27 109.27 109.27 109.27 MEK Solvent to make up 60.0% sol.
Stroke Cure Reactivity 265-269 267-271 269-273 277-281 170.degree.
C. (sec) NB, Components of formulations I to IV are given on a
solids basis
[0122] Preparation of Prepregs
[0123] Prepregs were prepared from formulation Examples I to IV by
dipping, using a substrate of glass cloth (Type 7628 from Porcher
Textile, Badinieres, Fr-38300 Bourgoin-Jallieu France, or Interglas
Textil GmbH, Ulm/Donau, Germany). The impregnated substrates were
passed through a CARATSCH.TM. pilot treater (built by Caratsch AG,
Bremgarten, Switzerland) having a 3-meter horizontal oven, at an
air temperature of from 180.degree. C. to 185.degree. C., and a
winding speed of from 1 to 2.1 m/min.
[0124] For each of formulation in Table 3, three different treater
settings were employed, selected so as to produce prepregs having
different residual gel times (approximately 120, 140, and 170
seconds, measured at 171.degree. C.)
[0125] The resin content of each prepreg was measured using 10
cm.times.10 cm square sheets of glass cloth before and after
prepreg production, according to Method IPC-L-109B,
IPC-TM-650:2.3.16 (available from the Institute for Interconnecting
and Packaging Electronic Circuits, Lincolnwood, Ill., USA). Results
appear in Tables 4 to 7.
6TABLE 4 Formulation Example I (Comparative) Settings A2 A5 A6 Oil
(.degree.C.) 240 Set Temp (.degree.C.) 185 Air Temp (.degree.C.)
180 Gap 48 44 46 Winding Speed 1.3 1.55 1.1 (m/min) Resin content
42 41 43.9 (wt %) Gel-time (sec) 142 175 126 MIL Flow (%) 20.0 21.0
20.3 Minimum Viscosity 20.48 5.12 27.52 @140.degree. C.
(Pa.sec)
[0126]
7TABLE 5 Formulation Example II (Comparative) Settings B3 B5 B6 Oil
(.degree.C.) 240 Set Temp (.degree.C.) 185 Air Temp (.degree.C.)
183.5 181.9 182.0 Gap 45 44 45 Winding Speed 1.59 1.9 1.7 (m/min)
Resin content 41.6 41.5 43.3 (wt %) Gel-time (sec) 117 167 147 MIL
Flow (%) 17.8 20.1 22.9 Minimum Viscosity 41.6 12.64 21.28
@140.degree. C. (Pa.sec)
[0127]
8TABLE 6 Formulation Example III (Invention) Settings D2 D3 D4 Oil
(.degree.C.) 240 Set Temp (.degree.C.) 185 Air Temp (.degree.C.)
183 Gap 45 44 42 Winding Speed (m/min) 1.5 1.75 2.1 Resin content
(wt %) 42.8 42.5 41.1 Gel-time (sec) 124 143 169 MIL Flow (%) 22.1
25.0 22.5 Minimum Viscosity 34.08 18.24 9.44 @140.degree. C.
(Pa.sec)
[0128]
9TABLE 7 Formulation Example IV (Invention) Settings E2 E3 E6 Oil
(.degree.C.) 240 Set Temp (.degree.C.) 183 Air Temp (.degree.C.)
179.4 Gap 58 57 54 Winding Speed (m/min) 1.5 1.75 1.3 Resin content
(wt %) 44.2 47.8 46.1 Gel-time (sec) 157 174 114 MIL Flow (%) 26.1
31.0 25.0 Minimum Viscosity 19.52 10.56 51.84 @140.degree. C.
(Pa.sec)
[0129] The viscosity of the B-staged materials was plotted against
time on a constant rising temperature scale of 1.5.degree. C./min,
over a temperature of from 80.degree. C. to 180.degree. C. The
resulting curves are shown as FIGS. 1 to 3 (with gel times of
approximately 120, 150, and 170 seconds, respectively).
[0130] FIGS. 1 to 3 demonstrate that the Examples according to the
invention have a viscosity which is significantly better (for an
equivalent gel time) than that of compositions containing no flow
modifier, (Formulation I), and at least as good as that of a
formulation containing PKHH (Formulation II).
[0131] Preparation of Laminates
[0132] Eight sheets of each prepreg were laid-up in alternating
layers with sheets of copper foil, according to the following press
cycle. The laid-up prepregs were cured according to the following
temperature profile, using the pressures shown in Tables 8 to
11:
10 Start Temp: 40.degree. C. Plateau Temp: 180.degree. C. Heat up
ramp duration 70 min Plateau Time: 40 min Cooling to RT time 50 min
Vacuum duration 30 min Low Pressure 40.degree.-110.degree. C. (25
KN/900 cm.sup.2) High Pressure 110.degree.-end (40 KN/900
cm.sup.2)
[0133] The following tests were performed on each cured
laminate:
[0134] (a) N-methylpyrrolidone (NMP) pick-up was measured by
weighing a 5 cm.times.5 cm sheet of laminate, immersing it in NMP
at 23.degree. C. for 30 minutes, and then reweighing. The results
are expressed as a percent gain.
[0135] (b) Laminate glass-transition temperature was measured using
a differential scanning calorimeter (DSC), scanning from 50.degree.
C. to 220.degree. C. at 10.degree. C. per minute. The results are
expressed in .degree. C. The same laminate sample was run twice, to
obtain Tg I and Tg II.
[0136] (c) Water resistance was measured by putting the laminates
in a pressure cooker for 120 minutes according to Method IPC-A-600,
IPC-MI-660 and IPC-TM-650:2.6.16. All laminates passed the test
with 100 percent. Water pick-up was measured.
[0137] (d) T--260 was measured as the time in minutes when the
laminate started to decompose, when heated to 260.degree. C.
11 TABLE 8 Laminate Laminate Laminate Laminate 1 2 3 4 Prepreg
setting A6 B3 D2 E6 (see tables 4-7) Laminate Properties Tg I/II
.degree.C. 147/145 144/143 148/146 149/147 (fresh prepreg) Tg I/II
.degree.C. 145/143 141/140 146/144 147/144 (prepreg aged 45 days at
room temp) Water pick-up, 0.47 0.48 0.47 0.49 (wt %) NMP pick-up
0.15 0.12 0.15 0.11 (wt %) T - 260 (min) 25.7 32.5 27.6 33.8
[0138] Table 8 demonstrates that the compositions according to the
invention show a higher Tg of the final laminate both immediately
after the laminate is prepared, and after 45 day aging of the
prepreg at room temperature, than corresponding laminates prepared
using PKHH.
[0139] Use of Different Viscosity Modifiers in Epoxy Formulations
Using Styrene/maleic Anhydide Copolymer as Curing Agent
(Hardener).
[0140] Compositions were prepared using styrene/maleic anhydride
copolymer as an epoxy hardener, and various hydroxyl-free viscosity
modifiers, as shown in Table 9. The epoxy resin C has the following
composition (parts by weight):
12 D.E.R .TM. 330 19.452 D.E.R .TM. 560 25.352 TBBA 11.196 TOTAL
56.000
[0141] To prepare resin C, the 3 components listed above were
blended at 130.degree. C. for 1 hour, and the solids were dissolved
in DOWANOL.TM. PMA to give a solution containing 85% solids.
[0142] The styrene/maleic anhydride copolymer was SMA 3000,
available from ELF ATOCHEM.
[0143] The brominated polystyrene was a material sold as PDBS-10
(by Great Lakes).
[0144] The Brominated polyphenylene oxide was a material sold as
PO-64P(by Great Lakes).
[0145] The Catalyst/inhibitor was a mixture of 2-ethyl,4-methyl
imidazole and boric acid, in a weight ratio of 5:4 (20% solids in
methanol).
13TABLE 9 Weight ratio of components (based on solids) IX VIII
(comparative- (comparative - PKHH no viscosity viscosity
Formulation V VI VII modifier) modifier) SMA 3000 (F) .TM. 44.000
44.000 44.000 44.000 44.000 (50% solid in DMF) Epoxy resin C 56.000
56.000 56.000 56.000 56.000 (85% solid in DOWANOL PMA .TM.) PKHH
solution 6.000 (30% solid in DMF) Example 2 6.000 (50% solid in
DMF) Brominated Polystyrene 6.000 (30% solid in DMF) Brominated
polyphenylene oxide 6.000 [30% solid in DMF] Catalyst/inhibitor
0.090 0.090 0.090 0.090 0.090 MEK Solvent to make up solution
Containing 60.0% solids TOTAL 106.090 106.090 106.090 100.090
106.090 Stroke Cure Reactivity 170.C (in sec.) 185-189 194-198
200-204** 184-188 179-185 - Day 1 Stroke Cure Reactivity 170.C (in
sec.) 171-175 182-186 182 -186 170-174 161-165 - Day 2 Stroke Cure
Reactivity 170.C (in sec.) 167-171 167-171 180-184 162-166 147-151*
- Day 3 *phase separation caused by onset of gelling. **The
formulation VII was turbid and the brominated polyphenylene oxide
settled out due to low solubility of the viscosity modifier.
[0146] As can be seen from Table 9, Formulations V, VI, and VII
containing viscosity modifiers with a near-zero hydroxy content all
show similar gel time reduction, with no phase separation caused by
onset of gelling, compared to the compositions containing no
viscosity modifier.
14TABLE 10 Formulation Example V Settings F4 F5 F6 Oil (.degree.
C.) 226 Set Temp (.degree. C.) 175 Air Temp (.degree. C.) 166 Gap
62 61 51 Winding Speed 0.9 1.0 1.1 (m/min) Resin content (wt %)
42.1 39.6 38.3 Gel-time (sec) 6 34 51 MIL Flow (%) 3.5 11.5
14.7
[0147]
15TABLE 11 Formulation Example VI Settings G1 G2 G3 Oil (.degree.
C.) 231 Set Temp (.degree. C.) 175 Air Temp (.degree. C.) 167 Gap
65 68 66 Winding Speed 0.9 1.0 1.1 (m/min) Resin content (wt %)
39.7 46.8 39.4 Gel-time (sec) 9 28 52 MIL Flow (%) 1.9 20.6
15.7
[0148]
16TABLE 12 Formulation Example VII Settings H3 H1 H2 Oil (.degree.
C.) 226 Set Temp (.degree. C.) 175 Air Temp (.degree. C.) 166 Gap
60 60 61 Winding Speed 0.9 1.0 1.1 (m/min) Resin content (wt %)
43.95 40.7 41.9 Gel-time (sec) 5 39 60 MIL Flow (%) 3.4 10.6
17.2
[0149]
17TABLE 13 Formulation Example IX (Comparative) Settings I2 I4 I5
I6 Oil (.degree. C.) 236 Set Temp (.degree. C.) 175 Air Temp
(.degree. C.) 166 167 Gap 55 55 53.5 53.5 Winding Speed (m/min) 1.1
1.3 1.4 1.5 Resin content (wt %) 39.5 43.2 42.5 43.2 Gel-time (sec)
4 32 43 46 MIL Flow (%) 1.4 18.2 18.2 21.5
[0150] The viscosity of the B-staged materials was plotted against
time on a constant rising temperature scale of 3.0.degree. C./min,
over a temperature of from 80.degree. C. to 200.degree. C. The
resulting curves are shown as FIGS. 4 to 6 (with gel times of
approximately 7, 33, and 49 seconds, respectively).
[0151] FIGS. 4 to 6 demonstrate that the Examples according to the
invention have a viscosity at least as good as that of a
formulation containing PKHH (Formulation IX).
[0152] Preparation of Laminates
[0153] Eight sheets of each prepreg were laid-up in alternating
layers with sheets of copper foil, according to the following press
cycle. The laid-up prepregs were cured according to the following
temperature profile, using the pressures shown in Tables 8 to
11:
18 Start Temp: 40.degree. C. Plateau Temp: 200.degree. C. Heat up
ramp rate0 3 .degree. C./min Plateau Time: 90 min Cooling to RT
time 50 min Vacuum duration 30 min Pressure 120 KN/900 cm
square
[0154] The standard copper foils NT-TW and the commercially
available treated copper foil NTTWS were obtained from Circuit
foils, 35 .mu.m thickness grade and the peel strength was measured
by IPC method TM-650 Number 2.4.8C.
19 TABLE 14 Laminate Laminate Laminate Laminate 5 6 7 8 Prepreg
setting F5 G2 H1 I5 (see Tables 10-13) Laminate Properties Tg I/II
.degree. C. 183/185 182/187 181/184 180/182 (fresh prepreg) Water
pick-up, wt % 0.19 0.21 0.21 0.21 Standard Copper 12.3 12.4 12.3
11.6 (NT-TW) peel Strength N/cm Treated Copper 15.4 13.4 15.1 16.2
(NTTWS) peel strength, N/cm
EXAMPLE 11
[0155] A polyoxazolidone viscosity modifier composition was
prepared using the general preparation method 1 outlined above with
the following ingredients: 68 weight percent epoxy resin A, 32
weight percent isocyanate A, and 1500 ppm DBU. The resulting
modifier resin had an EEW of 780 and a melt viscosity of 34 Pa.s at
200.degree. C.
[0156] An epoxy resin varnish composition according to the present
invention using the above viscosity modifier and a comparative
epoxy resin varnish without the viscosity modifier, were prepared
using the procedure as outlined for Formulation Examples I to IV
except that the base thermosetting resin used was D.E.R. 592A80.
D.E.R. 592A80 is a resin based on epoxy-terminated polyoxazolidone
resin and is commercially available from The Dow Chemical Company.
The ingredients and amounts of the varnishes are set out in Table
15 below. The varnishes were prepared by blending the various
components at room temperature using a mechanical stirrer. The
stroke cure reactivity of each of the varnishes are also shown in
Table 15.
[0157] Prepregs from the above described varnishes were prepared
and the gel time of each were measured according to the procedure
described above for Formulation Examples I to IV except that the
prepregs were pressed at 190.degree. C. in 90 minutes under a
pressure of 150 KN/900 square cm. The gel time of the prepregs are
shown in Table 15.
[0158] Laminates were prepared from the above prepregs according
the procedure described above for Formulation Examples I to IV
except that the following temperature profile was used:
20 Start temperature: 40.degree. C. Plateau temperature:
190.degree. C. Heat up ramp duration 45 minutes Plateau time 90
minutes Cooling to RT time 50 minutes Vacuum duration 30 minutes
Pressure 150 KN/900 cm.sup.2
[0159] The Tg of the laminates was measured and is shown in Table
15.
21 TABLE 15 Example 11 Comparative (Example of the Example A
Invention) Bare Thermosetting 100 part solid 100 part solid Resin
D.E.R. 592A80 Viscosity modifier, 0 3 (phr), (based on solid) Boric
acid, (phr) 0.4 (solid) 0.4 (solid) (20 wt % in methenol solution)
Catalyst, 2-ethyl, 0.6 0.6 4-methyl imidizole (phr) (2E4MI) (2E4MI)
Dicy, (phr) (10% soliid 2.8 (solid) 2.8 (solid) in Dowanol PM/DMF)
Varnish Gel time @170 218 241 .degree. C., (seconds) Treater
Setting Oven air temperature, 183 184 .degree. C. Treater speed,
m/min 1.5 1.6 Resin content, wt % 44 45.4 Prepreg Gel time 94 118
measured @171.degree. C., (seconds) Minimum melt viscosity, 79 85
measured @ 140.degree. C. (class) Laminate Tg, (.degree. C.) 176
174
[0160] The evaluation results described above in Table 15 shows
that it is possible to achieve a longer gel time for both varnish
and prepreg prepared using the viscosity modifier of the present
invention, and achieve a higher B-staged material melt viscosity
while maintaining high laminate Tg.
* * * * *