Heat-resistant epoxy resin composition based on 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane

Heat-resistant epoxy resin composition obtained by incorporation of 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane in a resin composition consisting esssentially of epoxy resin and an epoxy hardener is disclosed.

BACKGROUND OF THE INVENTION 
1.Field of the Invention 
The present invention relates to an epoxy resin composition which is 
excellent in heat-resistance and which can be used for insulation 
materials and laminate materials for electric and electronic parts, and 
particularly for sealing semiconductors. 
2.Description of the Prior Art 
The fields of electric equipment and electronic parts have the tendency to 
use high density mounting and multifunctionality. Accordingly, for 
insulation materials and laminate materials to be used in these fields, 
and particularly for sealing semiconductors, it is strongly desired to 
develop heat-resistant resin compositions capable of withstanding heat 
generation in the mounting step or in use. Technical innovation is 
particularly remarkable in the field of resin-sealing type semi-conductor 
equipment and the development of durable products for use in a more severe 
environment has been strongly required. 
The above resin-sealing is generally conducted by transfer molding of epoxy 
resin compositions in view of economy. In particular a system of o-cresol 
novolak type epoxy resin which a novolak type phenol resin as a hardener 
is excellent in moisture resistance and hence is mainly employed today. 
However, the resin-sealing type semiconductor equipment is being replaced 
by surface-mounted type semiconductor equipment according to the trend 
toward the above high density mounting. The surface-mounted type equipment 
is different from conventional inserted type semi-conductor equipment and 
the whole package is exposed to a soldering temperature of 200.degree. C. 
or more. Additionally, in an environment of extended use at high 
temperatures such as in the periphery of automotive engines, the resin 
composition used for the sealing material is required to have a high 
heat-resistance for the severe environment. Conventional epoxy resin 
cannot fulfil such requirement. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide an epoxy resin 
composition having excellent heat-resistance, particularly an epoxy resin 
composition which can be applied to the resin-sealing type semiconductor 
equipment requiring high heat-resistance. 
As a result of an intensive investigation in order to improve the 
heat-resistance of epoxy resins, the present inventors have found that 
excellent heat-resistance can be obtained by using a compound 
simultaneously comprising in the molecule a functional group capable of 
reacting with epoxy resin and a maleimide group having heat-resistance. 
Thus, the present invention has been completed. 
One aspect of the present invention is a heat-resistant epoxy resin 
composition comprising an epoxy resin, an epoxy hardener, and 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane illustrated by formula 
(I) : 
##STR1## 
Another aspect of the present invention is a novel process for preparing 
the compound of formula (I) for use in the composition of the present 
invention. 
The heat-resistant epoxy resin composition of the invention comprising 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane which has a maleimide 
group can provide high heat-resistance which could not be obtained with a 
conventional epoxy resin composition. When the resin composition is used 
for sealing the semiconductor equipment requiring high heat-resistance, 
excellent reliability can be obtained. Thus, the present invention is 
valuable in industry. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Conventional epoxy resins can be employed for the composition of the 
present invention as long as the epoxy resin is multivalent. 
Exemplary epoxy resins which can be used include: 
(1) novolak type epoxy resins such as glycidyl derivatives of phenol 
novolak and cresol novolak: 
(2) glycidyl derivatives of other compounds having two or more active 
hydrogens in a molecule, for example, glycidy) type epoxy resins obtained 
by reacting polyhydric phenols such as bisphenol A, 
bis(hydroxyphenyl)methane, resorcinol, bis(hydroxyphenyl)ether, and 
tetrabromobisphenol A; polyhydric alcohols such as ethylene glycol, 
neopentyl glycol glycerol, trimethylolpropane, pentaerythritol, diethylene 
glycol, polypropylene glycol, bisphenol A-ethylene oxide adduct and 
trihydroxyethylisocyanurate; amino compounds such as ethylenediamine, 
aniline and bis(4-aminophenyl)-methane; and polycarboxylic acids such as 
adipic acid, phthalic acid and isophthalic acid; with epichlorohydrin or 
2-methylepichlorohydrin, and: 
(3) dicyclopentadiene diepoxide and butadiene dimer diepoxide. 
One or more epoxy resins selected from the aliphatic and alicyclic epoxy 
resins such as above may be used. 
A preferred epoxy resin is the novolak type epoxy resins such as glycidyl 
compounds of phenol novolak and cresol novolak in view of heat-resistance 
and electrical properties in particular. 
Resins obtained by modifying the above epoxy resin with silicone oil or 
silicone rubber can also be used. Such resins include, for example, a 
silicone modified epoxy resin prepared by the process disclosed in 
Japanese Patent Laid-Open Publication SHO 62-270617(1987) and 
62-273222(1987). 
The epoxy hardener used in the composition of the present invention can be 
any type of epoxy hardener including phenol compounds, amine compounds, 
acid anhydrides and the like. Phenol compounds are preferred in view of 
moisture resistance and include, for example, novolak type phenol resins 
and aralkyl type phenol resins obtained by reacting phenols such as 
phenol, cresol and resorcinol with aldehydes or aralkyl ethers; and 
polyhydric phenols such as tri-hydroxyphenylalkanes and 
tetrahydroxyphenylalkanes. These phenol compounds are used singly or as a 
mixture. 
The amount of the epoxy hardener used is in the range of 0.1 to 10 
equivalents, preferably 0.5 to 2 equivalent per equivalents of the epoxy 
resin. 
The composition of the present invention uses 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane, i.e., the compound of 
formula (I), as a required component. 
The compound used can be prepared by known processes. However, a high 
purity compound can be prepared by a novel process found by the present 
inventors. The high purity compound can provide a composition which is 
excellent in heat-resistance and has good and stable quality. 
The compound of formula (I) used for the composition of the invention, 
i.e., 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane is useful as a 
modifying agent for various polymers. The compound has conventionally been 
prepared, for example, by reacting 
2-(4-hydroxyphenyl)-2-(4-aminophenyl)propane with maleic anhydride in the 
presence of a large amount of a dehydrating agent such as acetic 
anhydride, phosphorus oxide or condensed phosphoric acid as disclosed in 
Japanese Laid-Open Patent Publication SHO 55-149293(1980). However, the 
process produces acetylated compounds or esterified compounds as 
by-products because the amine compound used as the raw material has a 
hydroxyl group. Further, an addition reaction to the double bond of 
maleimide group takes place and leads to a decrease in the yield and 
purity and additionally to coloration. Consequently, 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane having good quality could 
not be obtained. 
The novel process described below which has been found by the present 
inventors has eliminated the disadvantage of the above conventional 
process and can give a high purity 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane in high yield and without 
by-products. 
That is, the embodiments of the preparation process in the present 
invention is to prepare the compound in high purity and high yield by 
conducting a dehydrating and ring-closing reaction of 
2-(4-hydroxyphenyl)-2-(4-aminophenyl)propane with maleic anhydride in an 
organic solvent capable of forming a water azeotrope in the presence of an 
acid catalyst and an aprotic polar solvent. 
The raw materials used in the process are 
2-(4-hydroxyphenyl)-2-(4-aminophenyl)propane (hereinafter referred to as 
amine compound) and maleic anhydride. The amount of maleic anhydride is in 
the range of 1.0 to 1.5 moles, preferably 1.05 to 1.3 moles per mole of 
amine compound. When the amount of maleic anhydride is less than 1.0 mole, 
it sometimes causes formation of unfavorable by-products which are adducts 
of 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane and excess amine 
compound remains. 
The reaction is carried out in the presence of a catalyst. 
Exemplary catalysts which can be used include mineral acids such as 
sulfuric acid and phosphoric acid, heteropoly acids such as wolframic acid 
and phosphomolybdic acid, organic sulfonic acids such as p-toluenesulfonic 
acid and methanesulfonic acid, and halogenated carboxylic acids such as 
trichloroacetic acid and trifluoroacetic acid. Sulfuric acid and 
p-toluenesulfonic acid are preferred in particular. 
The amount of the catalyst used is usually in the range of 0.5 to 5% by 
weight per total weight of amine compound and maleic anhydride. A catalyst 
amount less than 0.5% by weight leads to an insufficient effect of the 
catalyst. On the other hand, a catalyst amount exceeding 5% by weight is 
disadvantageous in economy and causes difficulty in removing the residual 
catalyst. 
The reaction is carried out by using solvents. Exemplary solvents used are 
organic solvents which can remove water by azeotropic distillation. 
Preferred solvents include, for example, benzene, toluene, xylene, 
mesitylene and chlorobenzene. The solvent is used in an amount of 3 to 10 
times by weight in order to smoothly progress the reaction. 
In the process of the invention, an aprotic polar solvent is used in 
combination with the above organic solvent capable of forming water 
azeotrope. Exemplary aprotic polar solvents include N,N-dimethylacetamide, 
N,N-dimethylformamide, N-methyl-2 pyrrolidone, 
1,3-dimethyl-2-imidazolidinone and N,N-diethylacetamide. The amount of the 
aprotic polar solvent is in the range of 10 to 40% by weight, preferably 
20 to 30% by weight per weight of the above organic solvent. 
The reaction is usually carried out by adding amine compound to the organic 
solvent solution of maleic anhydride and stirring at 150.degree. C. or 
less, preferably 20.degree. to 100.degree. C. for 10 minutes or more, 
preferably 0.5 to 1 hour to form maleamic acid. Successively the aprotic 
polar solvent and the acid catalyst are added to the reaction mixture 
obtained, heated to 80.degree. C. or more, preferably to a temperature 
range of 100.degree. to 180.degree. C., and stirred for 0.5 to 20 hours, 
preferably 4 to 8 hours to progress the reaction while azeotropically 
distilling off generated water. Alternatively, a mixture of maleic 
anhydride, the organic solvent and the catalyst is heated to a temperature 
range of 80.degree. to 180.degree. C. and a solution of amine compound in 
the aprotic polar solvent is added dropwise to the mixture. The reaction 
is progressed while azeotropically removing the generated water. 
After completing the reaction by the above steps, the reaction mixture is 
cooled to 60.degree. to 80.degree. C., and is immediately concentrated 
under reduced pressure to distill off the solvent. Thereafter water or a 
mixture of water and a suitable solvent such as methanol, ethanol and 
isopropyl alcohol is added to obtain 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane. 
2-(4-Hydroxyphenyl)-2-(4-maleimidophenyl)propane can be obtained by the 
process in high purity and high yield as compared with conventionally 
known processes. 
The content of 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane in the 
composition of the invention is in the range of 10 to 400 parts by weight 
per 100 parts by weight of the epoxy resin. When the content is less than 
10 parts by weight, good resistance to heat cannot be obtained. On the 
other hand, a content exceeding 400 parts by weight renders the cured 
product brittle. 
Use of curing accelerators in the composition of the invention is desired 
in order to cure the resin. Curing accelerators which can be used include, 
for example, imidazoles such as 2-methylimidazole and 
2-methyl-4-ethylimidazole; amines such as triethanolamine, 
triethylenediamine and N-methylmorpholine; organic phosphines such as 
tributylphosphine, triphenylphosphine and tritolylphosphine; 
tetraphenylborone salts such as tetraphenylphosphonium tetraphenylborate 
and triethylammonium tetraphenylborate; and 1,8-diazobicyclo 
(5,4,0)undecene-7 and derivatives thereof. These curing accelerators may 
be used singly or as a mixture and, when necessary, may also be used in 
combination with free-radical initiators such as organic peroxides or azo 
compounds. 
The amount of these curing accelerators used are in the range of 0.01 to 10 
parts by weight per 100 parts by weight of the sum of the epoxy hardener 
and the compound of formula (I). 
Other amorphous or crystalline additives may be added to the resin 
composition in addition to the above components depending upon the use and 
objects. Representative additives include spherically fused silica powder, 
alumina powder, silicon nitride powder, silicon carbide powder, glass 
fibers and other inorganic fillers; release agents such as fatty acids, 
fatty acid salts and waxes; flame retardants such as bromine compounds, 
antimony compounds and phosphorus compounds; coloring agents such as 
carbon black and coupling agents such as silane base, titanate base, and 
zirco aluminate base.

The present invention will hereinafter be illustrated in detail by way of 
examples. 
EXAMPLE 1 
To a reaction vessel equipped with a stirrer, thermometer and an azeotropic 
distillation trap, 60 g (0.1 mole) of maleic anhydride, 480 g of toluene 
and 2.6 g of 95% sulfuric acid were charged and heated to a reflux 
temperature. A solution containing 114 g (0.5 mole) of 
2-(4-hydroxyphenyl)-2-(4-aminophenyl)propane in 160 g of 
N,N'-dimethylacetamide was dropwise added from a dropping funnel over 4 to 
5 hours and reacted for 5 hours at the same temperature. Generated water 
by the reaction was removed by azeotropic distillation. After completing 
the reaction, the reaction mixture was cooled to 80.degree. to 90.degree. 
C. and the solvent was successively removed under reduced pressure. The 
organic layer thus obtained was mixed with 100 ml of isopropyl alcohol and 
then 300 ml of water was added and stirred for 0.5 to 1 hour to 
precipitate crystals. The crystals were filtered and dried to obtain 147 g 
of 2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane as yellow crystals. 
The yield was 96%. 
The product had a melting point of 168.degree.-171.degree. C. and a purity 
of 99% by gel permeation chromatography (GPC). 
______________________________________ 
Elemental analysis (%) 
C H N 
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Calculated 74.8 5.5 4.6 
Found 74.1 5.66 4.5 
MS (EI): 307.sup.(M+1) 
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EXAMPLE 2 
The same procedures as conducted in Example 1 were carried out except that 
480 g of chlorobenzene was used in place of toluene to obtain 149 g 
2-(4-hydroxyphenyl)-2-(4-maleimidophenyl)propane as yellow crystals. The 
yield was 97%. The product had a melting point of 167.degree. to 
171.degree. C. and a purity of 98.5% by GPC. 
EXAMPLE 3 
The same procedures as conducted in Example 1 were carried out except that 
2.6 g of methanesulfonic acid was used as the catalyst, 160 g of 
N-methyl-2-pyrrolidone was used as the aprotic polar solvent, and 60 g 
(0.61 mole) of maleic anhydride was used. 
2-(4-Hydroxyphenyl)-2-(4-maleimidophenyl)propane thus obtained was 147 g. 
The yield was 96%. The product was yellow crystals and had a melting point 
of 167.degree.-171.degree. C. and a purity of 98.5% by GPC. 
EXAMPLE 4 
To a reaction vessel equipped with a stirrer, thermometer and an azeotropic 
distillation trap, 300 g (0.3 mole) of maleic anhydride and 240 g of 
toluene were charged and 57 g (0.25 mole) of 
2-(4-hydroxyphenyl)-2-(4-aminophenyl)propane was added with stirring. The 
reaction was carried out for an hour and then 1.3 g of p-toluenesulfonic 
acid and 80 g of N,N-dimethylacetamide were added. The resulting mixture 
was heated to reflux temperature and reacted for 10 hours while 
azeotropically distilling off water generated by the reaction. After 
completing the reaction, the reaction mixture was cooled to 
80.degree.-90.degree. C. and the solvent was successively distilled off 
under reduced pressure. The residual organic layer was mixed with 100 ml 
of methanol and then 300 ml of water. The mixture was stirred for 0.5-1 
hour to precipitate crystals. The crystals were filtered and dried to 
obtain 74 g of 2-(4-hydroxyphenyl)-2- 4-maleimidophenyl) propane as yellow 
crystals. The yield was 96.3%. The product had a melting point of 
168.degree.-171.degree. C. and a purity of 99% GPC. 
EXAMPLE 5 
The same procedures as conducted in Example 4 was carried out except that 
240 g of xylene was used as the organic solvent and 40 g of 
N,N-dimethylformamide was used as the aprotic polar solvent. 
2-(4-Hydroxyphenyl)-2-(4-maleimidophenyl)propane thus obtained was 73.3 g. 
The yield was 95.5%. 
The product was yellow crystals and had a melting point of 
168.degree.-171.degree. C. and a purity of 99% by GPC. 
EXAMPLES 6 AND 7, AND COMATIVE EXAMPLES 1 
The formulations of Table 1, the raw material amounts of which are 
illustrated in parts by weight, were melt-kneaded on hot rolls at 
100.degree.-130.degree. C. for 3 minutes, cooled, crushed and tabletted to 
obtain molding compositions. 
The following raw materials were used in the formulations of Table 1. 
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Epoxy resin Trademark, EOCN-1027 
A product of Nippon Kayaku Co. Ltd. 
Novolak phenol resin 
Trademark, PN-80 
A product of Nippon Kayaku Co., Ltd. 
Phenol aralkyl resin 
Trademark, MILEX XL-225L 
A product of Mitsui Toatsu Chemicals 
Inc. 
Fused silica Trademark, HARIMICK S-CO 
A product of Micron Co., Ltd. 
Silane coupling agent 
Trademark, NCU Silicone A-187 
A product of Nippon Unicar Co., Ltd. 
______________________________________ 
These compositions were transfer molded at 180.degree. C. for 3 minutes 
under a pressure of 30 kg/cm.sup.2 to obtain test pieces for measuring 
physical properties. 
Separately, a test element of 10.times.10 mm in dimension fitted on the 
four edges with aluminium bonding pad members of 100.times.100.times.1.mu. 
in dimension and aluminum wiring of 10.mu. in width which connected these 
pad members was mounted on the element fitting portion of a lead frame for 
a flat package. The lead frame and the bonding pad members were connected 
with gold wires and the above compositions were transfer molded under the 
same conditions as above. Thus, semiconductor equipment for tests were 
prepared. These molded specimens for the tests were post cured at 
180.degree. C. for 6 hours prior to the test. Results are illustrated in 
Table 2. 
The following test methods were used. 
Glass transition temperature: In accordance with TMA method 
Flexural strength: In accordance with JIS K-6911 
Heat deterioration test at 200.degree. C.: Flexural strength was measured 
before and after storing the test piece in a constant temperature oven at 
200.degree. C. for 1000 hours. Results are illustrated by the retention of 
flexural strength. 
VSP test: The semiconductor equipment for test was allowed to stand at 
121.degree. C. for 24 hours under pressure of 2 atmospheres in a pressure 
cooker tester and immediately immersed in a FLORENATE liquid (Trademark; 
FC-70, a product of Sumitomo 3M Co., Ltd.) which was previously maintained 
at 215.degree. C. The numbers of pieces of semiconductor equipment which 
generated cracks in the packaging resin were counted. The numerator 
indicates the number of semiconductors which generated cracks. The 
denominator indicates the total number of semiconductors tested. 
High temperature storage test: The semiconductor equipment was allowed to 
stand at 200.degree. C. for 1000 hours in a constant temperature oven. 
Thereafter, operating tests was carried out. Results are illustrated by 
cumulative failure rate of the semiconductor equipment which did not 
operate in the test. 
TABLE 1 
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Example Example Comparative 
Raw material 6 7 Example 1 
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Epoxy resin (EP = 195)*.sup.1 
100 100 100 
Novolak phenol resin 
46 23 54 
(OH = 106)*.sup.2 
Phenol aralkyl resin 
-- 38 -- 
(OH = 174) 
Compound of Example 1 
25 25 -- 
Fused silica 606 659 546 
(average particle size 24.mu.) 
Triphenylphosphine 
1.4 1.5 1.2 
Silane coupling agent 
4.7 5.1 4.2 
Carnauba wax 3.5 3.8 3.2 
Carbon black 2.3 2.5 2.1 
Antimony oxide 7.8 8.5 7.0 
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*.sup.1 Epoxy value 
*.sup.2 OH value 
TABLE 2 
______________________________________ 
Example Example Comparative 
Property 6 7 Example 1 
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Glass transition temperature 
180 180 160 
(.degree.C.) 
Flexural strength (kg/cm.sup.2) 
room temperature 
16.0 16.0 15.0 
215.degree. C. 3.5 3.5 1.0 
Heat deterioration at 200.degree. C. 
80 80 50 
(Strength retention after 
1000 hrs: %) 
VSP test (Crack generation 
0/20 0/20 20/20 
rate) 
High temperature storage 
0 0 63 
test (Cumulative failure 
rate: %) 
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