Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-11-17
2002-04-23
Tucker, Philip (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C528S015000, C528S031000, C528S032000, C523S200000, C427S219000, C524S497000
Reexamination Certificate
active
06376603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a titanium oxide-filled addition reaction-curable silicone rubber composition having a low viscosity and low thixotropic properties.
2. Description of the Prior Art
Titanium oxide is conventionally added in silicone compositions as a colorant. As its new uses, e.g., there is a demand for uses as a light-screening agent in thin films or conversely as a reflecting agent. Stated specifically, there is a demand for its use in parallel type reflecting agents of photocoupler devices and reflective undercoatings of LEDs.
To meet such a demand, it is necessary to add the titanium oxide in a large quantity. However, adding titanium oxide in a silicone rubber composition in a large quantity as conventionally done makes the composition have a high viscosity and high thixotropic properties to make it difficult to handle and also provide no satisfactory operability.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a titanium oxide-filled addition reaction-curable silicone rubber composition having a low viscosity and low thixotropic properties and easy to handle, even though it contains titanium oxide in a large quantity, and especially having a superior operability when used as a light-screening agent or a reflecting agent.
To achieve the above object, the present invention provides a titanium oxide-filled addition reaction-curable silicone rubber composition comprising;
(A) a diorganopolysiloxane containing at least two alkenyl groups in one molecule;
(B) an organohydrogenpolysiloxane containing in one molecule at least two hydrogen atoms bonded to silicon atoms;
(C) a platinum group metal catalyst; and
(D) a titanium oxide powder having been surface-treated with a compound selected from the group consisting of a tetraalkoxysilane and a partial hydrolysis-condensation product of a tetraalkoxysilane; the titanium oxide powder being contained in an amount not less than 15 parts by weight based on 100 parts by weight of the component (A).
The present invention also provides a cured product obtained by curing the above composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described below in detail.
(A) Alkenyl Group-containing Diorganopolysiloxane:
The component-(A) diorganopolysiloxane is a compound containing at least two alkenyl groups in one molecule, and is used as a base polymer of the composition of the present invention. This alkenyl group-containing diorganopolysiloxane is normally a substantially linear (or straight-chain) compound whose backbone chain moiety consists basically of repetition of diorganopolysiloxane units and both molecular-chain terminals are terminated with triorganopolysiloxyl groups. It may also contain a branched structure at some parts of its molecular structure, or may have a cyclic structure on the whole. In particular, in view of physical properties such as mechanical strength of cured products, straight-chain diorganopolysiloxanes are preferred. The alkenyl group may be present only on the both terminals of the molecular chain, may be present only in the course of the molecular chain as side-chain substituents, or may be present both on the both terminals of the molecular chain and in the course of the molecular chain.
As typical examples of such an alkenyl group-containing diorganopolysiloxane, it may include diorganopolysiloxanes represented by the following general formula (1):
wherein R
1
's each independently represent a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, X represents an alkenyl group, Y's each represent an alkenyl group or a group represented by R
1
, n is an integer of 0 or 1 or more, and m is an integer of 0 or 1 or more; having in the molecule at least two alkenyl groups bonded to silicon atoms.
In the general formula (1), the substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, represented by R
1
may include, e.g., alkyl groups such as a methyl group, a ethyl group, a propyl group, a isopropyl group, a butyl group, a isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, a octyl group, a nonyl group, a decyl group and a dodecyl group; cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group and a cycloheptyl group; aryl groups such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group and a biphenyl group; aralkyl groups such as a benzyl group, a phenylethyl group, a phenylpropyl group and a methylbenzyl group; and any of these groups at least part of hydrogen atoms bonded to carbon atoms of which has been substituted with a halogen atom such as fluorine, chlorine or bromine or a cyano group, as exemplified by halogen-substituted alkyl groups, cyano-substituted alkyl groups and halogen-substituted aryl groups such as a chloromethyl group, a 2-bromomethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a chlorophenyl group, a fluorophenyl group, a cyanoethyl group, a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group. Typical groups represented by R
1
are those having 1 to 10 carbon atoms, in particular, those having 1 to 6 carbon atoms, and preferably substituted or unsubstituted alkyl groups having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluorpropyl group and a cyanoethyl group; and substituted or unsubstituted phenyl groups such as a phenyl group, a chlorophenyl group and a fluorophenyl group.
In the general formula (1), the alkenyl group represented by X may usually include those having 2 to 8 carbon atoms as exemplified by a vinyl group, an allyl group, a propenyl group, a isopropenyl group, a butenyl group, a hexenyl group and a cyclohexenyl group. In particular, lower alkenyl groups such as a vinyl group and an allyl group are preferred.
In the general formula (1), n is an integer of 0 or more, and m is an integer of 0 or more. Also, n and m may preferably be integers that satisfy 10≦n+m≦10,000 and 0≦m/ (m+n)≦0.2, and particularly preferably integers that satisfy 50≦n+m≦2,000 and 0≦m/(m+n) ≦0.05. Y's each represent an alkenyl group or the group represented by R
1
. This alkenyl group may include the same as those exemplified for those of X, and R
1
is as defined above, provided that Y's as substituents bonded to silicon atoms at the molecular-chain both terminals may both preferably be alkenyl groups.
This alkenyl group-containing diorganopolysiloxane may also preferably be those having a viscosity at 25° C. of from 1 to 100,000 poises, and particularly from about 10 to 50,000 poises.
(B) Organohydrogenpolysiloxane:
The component-(B) is a compound having in one molecule at least two, and preferably at least three, hydrogen atoms bonded to silicon atoms (i.e., SiH groups), and is used as a cross-linking agent (D). This organohydrogenpolysiloxane may be any of resinous products having a straight-chain, branched, cyclic or three-dimensional network structure. As typical examples of such an organohydrogenpolysiloxane, it may include, e.g., organohydrogenpolysiloxanes represented by the following average compositional formula (2):
H
a
R
2
b
SiO
(4-a-b)/2
(2)
wherein R
2
independently represents a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond; and a and b are numbers that satisfy 0<a<2, 0.7≦b≦2 and 0.8≦a+b≦3, and preferably 0.001≦a≦1.2, 0.8≦b≦2 and 1≦a+b≦2.7, and more preferably 0.01≦a≦1, 1.2≦b≦2 and 1.8≦a+b≦2.4.
In the average compositional formula (2), the substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, represented by R
2
may include the same as those exemplified for R
1
in the general formula (1). Typical groups represented by R
2
are those having 1 to 10 carbon atoms, in pa
Peng Kuo-Liang
Shin-Etsu Chemical Co. , Ltd.
Tucker Philip
LandOfFree
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