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
1999-11-30
2001-08-14
Moore, Margaret G. (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...
C524S290000, C524S306000, C524S311000, C524S287000, C524S299000, C524S300000, C524S308000, C524S321000, C524S588000
Reexamination Certificate
active
06274658
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a one-part or two-part, addition-curable silicone rubber composition having both a sufficient storage stability and a rapid-curing performance.
2. Description of the Prior Art
Addition-curable silicone rubber compositions making use of platinum or platinum compounds as curing catalysts have a good curing performance and also, as materials, they are r adaptable to both the millabe type and the liquid type. Hence, they are used for various purposes. In particular, the liquid-type ones are useful as adhesives, impression materials, LIMS materials and so forth. In either type, the composition may be mixed and/or heated to accelerate cross-linking reaction, thus a rubbery cured product can be obtained.
In the case of the one-part type, usually a cure retarding agent i.e. addition reaction (hydrosilylation reaction) inhibitor is compounded in order to ensure the storage stability of compositions (for a storage time before use), and hence they must be heated to make it cure. In such an instance, high-temperature heating is desirable for accelerating the curing. When the high-temperature heating is not applicable for some reasons, the compositions can not help being heated for a long time at a low temperature. When such long-time heating is improper, the two-part type can not help being used. Thus, it is desired for the one-part type to have a sufficient storage stability and also to be curable in a short time even at a low temperature.
In the case of the two-part type also, it is desired for them to have a sufficient storage stability and also to be curable in a short time at a low temperature.
Accordingly, studies have been made in variety on the both types so as to obtain curable compositions having both the sufficient storage stability and the rapid-curing performance in a well balanced state. Especially on the one-part type compositions, studies have been made in variety using vinyl-containing siloxanes, phosphorus compounds, nitrogen compounds or acetylene alcohols as cure retarding agents.
However, any addition-curable silicone rubber composition having both the sufficient storage stability and the rapid-curing performance in a well balanced state have not been obtained in the both cases of one-part type and two-part type.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an addition-curable silicone rubber composition having both the sufficient storage stability and the rapid-curing performance in a well balanced state.
As a means for achieving such an object, the present invention provides an addition-curable silicone rubber composition comprising;
(A) an organopolysiloxane containing in one molecule at least two alkenyl groups bonded to silicon atoms, represented by the average compositional formula (1):
R
1
a
R
2
b
SiO
(4−a−b)/2
wherein R
1
represents a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond; R
2
represents an alkenyl group; and a is a number ranging from 0.96 to 2.00, b is a number ranging from 0.0001 to 0.5, and a and b satisfy a +b =1.90 to 2.04;
(B) an organohydrogenpolysiloxane containing in one molecule at least two hydrogen atoms bonded to silicon atoms, represented by the average compositional formula (2):
R
3
c
H
d
SiO
(4−c−d)/2
wherein R
3
represents a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond; and c is a number ranging from 0.70 to 2.0, d is a number ranging from 0.005 to 1.0, and c and d satisfy c+d=0.8 to 3.0;
(C) a platinum catalyst; and
(D) a (meth)acrylate compound having a melting point of 40° C. or above.
The composition of the present invention may optionally further contain (E) an acetylene alcohol compound or an acetylene alcohol compound the alcoholic hydroxyl group (C—OH) of which has been modified with a silane or siloxane.
DESCRIPTION OF THE REFERRED EMBODIMENTS
The present invention will be described below in greater detail.
(A) Organopolysiloxane:
The component-(A) organopolysiloxane is a compound having in one molecule at least two alkenyl groups bonded to silicon atoms, represented by the average compositional formula (1): R
1
a
R
2
b
SiO
(4−a−b)/2
This is used as a base polymer. There are no particular limitations on the molecular structure of this organopolysiloxane. It may have any of straight-chain, branched-chain, cyclic and three-dimensional network structures. It may also be a polymer formed of single siloxane units or a copolymer formed of two or more types of siloxane units. In usual instances, it is commonly a straight-chain diorganopolysiloxane whose molecular chain is terminated with triorganosiloxyl groups at both terminals and backbone chain is substantially formed of the repetition of diorganosiloxane units. Also, the alkenyl groups in the molecule may be groups bonded to either silicon atoms at molecular chain terminals or silicon atoms at some positions of the molecular backborn chain, or may be groups bonded to the both of these. In view of physical properties of cured products, it may preferably be one containing alkenyl groups bonded to at least the silicon atoms at the both molecular chain terminals.
In the average compositional formula (1), R
1
's may be the same or different, and each represent a substituted or unsubstituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, having 1 to 12 carbon atoms, and preferably 1 to 8 carbon atoms. As specific examples of the group represented by R
1
, it may include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl 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 and a naphthyl group; aralkyl groups such as a benzyl group, a phenylethyl group and a phenylpropyl group; and any of these hydrocarbon groups at least part of hydrogen atoms of which has been substituted with a halogen atom such as a fluorine atom, a bromine atom or a chlorine atom or with a nitrile group to form substituted hydrocarbon groups, as exemplified by a trifluoropropyl group, a chloromethyl group and a cyanoethyl group. In particular, in view of readiness for synthesis and chemical stability, it is preferred that R
1
's are all methyl groups. If necessary in view of properties, part of the methyl groups may be substituted with a phenyl group or trifluoropropyl group.
R
2
represents an alkenyl group. As specific examples of the alkenyl group represented by R
2
, it may usually include those having about 2 to 6 carbon atoms, such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a pentenyl group, an hexenyl group and a cyclohexenyl group. The vinyl group and allyl group are preferred. In view of readiness for synthesis and chemical stability, the vinyl group is more preferred.
Letter symbol a is a number ranging from 0.96 to 2.00, and preferably from 1.8 to 2.00; b is a number ranging from 0.0001 to 0.5, and preferably from 0.001 to 0.1; and a and b satisfy a+b=1.90 to 2.04, and preferably 1.95 to 2.02.
This organopolysiloxane may usually have a viscosity at 25° C. of 10 cSt (centistokes) or above, preferably within the range of from 50 to 5,000,000 cSt, and more preferably from 100 to 1,000,000 cSt, in view of the flexibility of resulting cured products and the workability of compositions.
As typical examples of the component-(A) organopolysiloxane, it may include methylvinylsiloxane cyclic copolymers, methylvinylsiloxane-dimethylsiloxane cyclic copolymers, dimethylsiloxane-methylvinylsiloxane copolymers terminated with trimethylsiloxyl groups at both terminals of the molecular chain, methylvinylpolysiloxanes terminated with trimethylsiloxyl groups at both terminals of the molecular chain, dimethylsiloxane-methylvinylsiloxane-
Moore Margaret G.
Pillsbury & Winthrop LLP
Shin-Etsu Chemical Co. , Ltd.
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