Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-13
2001-09-18
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S457000, C525S510000, C525S931000, C528S028000
Reexamination Certificate
active
06291599
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to an epoxy resin having an improved flexibility and a lower internal stress after being cured.
BACKGROUND OF THE INVENTION
Due to the rapid development of the electronic and information industries in recent years, the new generation of semiconductor production processes demand the epoxy resin to have a high I/O (Input and Output Count) modulus, high heat resistance, high flowability, high physical properties, etc. Therefore, the studies on how to improve the flexibility and heat resistance of the epoxy resin become another essential field of research. The structure of a siloxane compound has properties such as good thermal stability and anti-oxidation property, good air permeability and electrical insulation property, maintaining softness, elasticity and flowability at a low temperature, good weather resistance, and low stress formation, etc. Therefore, such a structure is helpful to the improvement of flexibility and the reduction of stress formation.
In 1996, Chun-Shan Wang et al. [T. H. Ho, C. S. Wang, polymer, 37, 2722(1996)] produced thermoplastic polyurethane (TPU) by reacting various siloxane compound monomers of OH-terminated polydimethyl siloxane with isocyanate-containing monomers such as MDI or TDI in room temperature using dibutyltindilaurate-T12 as the catalyst. The reaction forms a thermoplastic polyurethane (TPU) with the main chain of which containing siloxane. The TPU of various structure is blended with an o-cresol formaldehyde novolac epoxy resin and then cured at 150° C. and 50 kgr/cm
2
for one hour, and at 180° C. and 210° C. for two and three hours, respectively. The results indicate that the cured article has a higher thermal resistance and a higher Thermal Shock Cycling Test value thereby improving the defects in the thermal resistance and the existence of internal stress existed the epoxy resin molding formulation for IC packaging.
The curing of an epoxy resin at a high temperature will cause the formation of a residual internal stress and brittleness. Relatively, polysiloxane has a lower degree of stress formation and a better flexibility. Therefore, the use of polysiloxane in improving the flexibility of epoxy resin has received a wide attention in the industry. However, there is a large difference in the solubility parameter between the polysiloxane and the epoxy resin thereby causing a severe phase separation and a non-uniform distribution of the polysiloxane in the epoxy resin. There are a wide variety of epoxy resins and their hardeners; and the reaction mechanisms thereof vary, as well. Therefore, the addition of a polysiloxane into any epoxy resin curing system will not unanimously achieve the property-modifying effects. The predominant factor affecting the improvement of flexibility is the improvement of the compatibility between the polysiloxane and the epoxy resin. Therefore, the increase of the molecular attractions between the polysiloxane and the epoxy resin can achieve this effect; and the formation of the hydrogen bonding is the most effective method in increasing the attractive force between two molecules.
The objectives of the present invention are to provide a polysiloxane urethane modifier and the use of the modifier in improving the flexibility of the epoxy resin and toughening the epoxy resin by grafting the modifier to an epoxy resin.
BRIEF DESCRIPTION OF THE INVENTION
The present invention discloses a modifier for improving the flexibility of the epoxy resin wherein the modifier has the following chemical structure (I):
where
m is an integer of 0<m<10;
R
1
is an alkyl having 1~7 carbons;
R
2
is an alkyl having 1~7 carbons; preferably, m=5, R
1
and R
2
are —(CH
2
)
6
—.
The present invention also discloses an epoxy resin having a modifying side chain of a polysiloxane urethane group wherein the epoxy resin has the following chemical structure:
where:
m is an integer of 0<m<10,
p
is between {fraction (1/100)} and {fraction (25/100)}, and 0<n, p<1;
R
1
is an alkyl having 1~7 carbons;
R
2
is an alkyl having 1~7 carbons;
Ep is
where
or Ep is a novolac-type epoxy resin group having the following formula
where R
3
is hydrogen or methyl, g is an integer of 1 to 6, R
4
and R
5
independently are hydrogen or
where R
3
has a same definition as the above. Preferably, m=5, R
1
and R
2
are &Parenopenst;(CH
2
)
6
&Parenclosest;; and Q is —C(CH
3
)
2
—.
The present invention further discloses a method of preparing a modified epoxy resin, which comprises reacting a modifier as claimed in claim
1
with an epoxy resin of the following formula in a molten state:
where:
0<r<1;
Ep is
where
or Ep is a novolac-type epoxy resin group having the following formula
where R
3
is hydrogen or methyl, g is an integer of 1 to 6, R
4
and R
5
independently are hydrogen or
where R
3
has a same definition as the above wherein the reaction is carried out in an inert gas at a temperature of 80° C.-120° C.; and the amount of addition of the modifier as claimed in claim
1
is 1 phr to 30 phr (parts by weight per 100 parts by weight of the epoxy resin).
REFERENCES:
patent: 4707529 (1987-11-01), Hoffman et al.
patent: 5844053 (1998-12-01), Nishida
patent: 5962139 (1999-10-01), Hagiwara et al.
Chen Hon-Bin
Ma Chen-Chi Martin
Yang Jeng-Cheng
Chung-Shan Institute of Science & Technology
Dawson Robert
Jackson Walker L.L.P.
Zimmer Marc S.
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