Alkenyl organopolysiloxane and curable composition therefrom

Organopolysiloxanes which have end groups of the general formula ##STR1## where R is alkenyl, Z is alkylene, R.sup.1 is a monovalent organic group, and a is 2 or 3, when mixed with organohydrogensiloxane and a platinum catalyst cure to high strength products without the use of a reinforcing filler.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention provides an alkenyl organopolysiloxane and a curable 
organopolysiloxane composition. More specifically, the present invention 
provides a curable organopolysiloxane whose cured product has a high 
physical strength in the absence of any addition of reinforcing fillers. 
2. Background Information 
Curable organopolysiloxanes are known in the prior art which are composed 
of polysiloxane containing silicon-bonded vinyl groups, polysiloxane 
containing silicon-bonded hydrogen atoms, and a platinum catalyst. 
However, the cured products of such curable organopolysiloxanes generally 
exhibit the drawback of poor physical strength values for the tensile 
strength, tear strength, and hardness. For this reason, a reinforcing 
filler or reinforcing silicone resin is added to such a composition in 
order to improve the physical strength of the cured product with the 
resulting drawback of a too high viscosity and process complications. 
Various methods were examined by the present inventor in order to eliminate 
the above-mentioned drawbacks in the prior art and a curable 
organopolysiloxane composition was discovered as a result whose cured 
product has a high physical strength in the absence of addition of any 
reinforcing filler. 
SUMMARY OF THE INVENTION 
This invention relates to a curable organopolysiloxane composition 
comprising (a) organopolysiloxane in which at least the molecular chain 
ends possess groups with a general formula selected from the group 
consisting of 
##STR2## 
wherein R is an alkenyl group, R.sup.1 is a monovalent organic group 
selected from the group consisting of alkyl, alkenyl, alkoxy, aryl, and 
halogenated alkyl, Z is an alkylene group, and a is 2 or 3, (b) 
organohydrogenpolysiloxane which contains at least two silicon-bonded 
hydrogen atoms per molecule, and (c) a catalytic quantity of platinum or a 
platinum-type compound, in said curable organopolysiloxane composition the 
blending ratio of (a) to (b) is such that the total alkenyl groups in (a) 
to total silicon-bonded hydrogen atoms in (b) is in a molar ratio of from 
1:0.1 to 1:10. 
This invention also relates to an organopolysiloxane comprising a polymer 
in which at least the molecular chain ends possess groups with a general 
formula selected from the group consisting of 
##STR3## 
wherein R is an alkenyl group, R.sup.1 is a monovalent organic group 
selected from the group consisting of alkyl, alkenyl, alkoxy, aryl, and 
halogenated alkyl, Z is an alkylene group, and a is 2 or 3. 
DETAILED DESCRIPTION OF THE INVENTION 
Component (a) is organopolysiloxane in which at least the molecular chain 
ends possess groups with a general formula selected from 
##STR4## 
R in the above general formula is an alkenyl group such as vinyl, allyl, 
and propenyl. R.sup.1 is a monovalent organic group such as alkyl groups 
such as methyl, ethyl, and propyl; alkenyl groups such as vinyl, allyl, 
and propenyl; alkoxy groups such as methoxy, ethoxy, propoxy, and 
methoxyethoxy; aryl groups such as phenyl; and halogenated alkyl groups. 
The subscript a is 2 or 3 and preferably 3. Z is an alkylene such as 
ethylene and propylene. The structure of the organopolysiloxane main chain 
of this component is arbitrary and it may be straight chain, branched 
chain, or network. The organic groups bonded to silicon in this 
organopolysiloxane include alkyl groups such as methyl, ethyl, and propyl; 
alkenyl groups such as vinyl, allyl, and propenyl; alkoxy groups such as 
methoxy, ethoxy, propoxy, and methoxyethoxy; aryl groups such as phenyl; 
and halogenated alkyl groups. In addition, small quantities of hydrogen 
atoms, hydroxyl groups, and organopolysiloxane groups, etc., can be 
present. Alkylene, silalkylene, and oxyalkylene groups can be present in 
the organopolysiloxane main chain of this component as long as they do not 
adversely affect the goal of the present invention. The molecular weight 
of this component is such that the viscosity must be 0.01 to 100 
pa.multidot.s at 25.degree. C. The instant organopolysiloxane can be 
produced by methods known in the prior art, for example, by the 
condensation of a silanol-terminated organopolysiloxane with an 
organosilicon compound with the general formula 
EQU XSiR.sub.3-a.sup.1 (OSiRR.sub.2.sup.1).sub.a 
where X is a hydrolyzable group or by the addition reaction of 
SiH-terminated organopolysiloxane with an organosilicon compound with a 
general formula selected from 
EQU CH.sub.2 .dbd.CH--Si(OSiRR.sub.2.sup.1).sub.a 
and 
EQU R.sub.b.sup.1 Si(OSiRR.sub.2.sup.1).sub.4-b 
in the presence of a platinum catalyst. The subscript b in the above 
formula is 3 or 4. 
Component (b) is organohydrogenpolysiloxane which possesses at least 2 
silicon-bonded hydrogen atoms per molecule. The structure of this 
component is arbitrary and it may be straight chain, branched chain, 
cyclic, or network. Organic groups bonded to silicon in the instant 
organopolysiloxane include alkyl groups such as methyl, ethyl, and propyl; 
alkoxy groups such as methoxy, ethoxy, propoxy, and methoxyethoxy; aryl 
groups such as phenyl; and halogenated alkyl groups. The molecular weight 
of component (b) is such that the viscosity must be 0.0001 to 10 
Pa.multidot.s at 25.degree. C. Examples of component (b) are 
trimethylsilylterminated dimethylsiloxane-methylhydrogensiloxane 
copolymer, dimethylhydrogensilyl-terminated 
dimethylsiloxane-methylhydrogensiloxane copolymer, 
trimethylsilyl-terminated methylhydrogenpolysiloxane, 
dimethylhydrogensilyl-terminated methylhydrogenpolysiloxane, 
methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, and 
organopolysiloxane consisting of (CH.sub.3).sub.2 HSiO.sub.1/2 units and 
Si0.sub.2 units. 
The blending ratio of component (a) to component (b) must satisfy the 
condition that the total alkenyl groups in component (a) to the total 
silicon-bonded hydrogen atoms in component (b) has a molar ratio of from 
1:0.1 to 1:10, preferably over 1:0.3 to 1:3 and more preferably over 1:0.6 
to 1:1.5. 
Component (c) is a catalyst which cures components (a) and (b) by an 
addition reaction and is platinum or a platinum-type compound. Examples 
thereof are finely particulate platinum, finely particulate platinum 
adsorbed on a carbon powder support, chloroplatinic acid, alcohol-modified 
chloroplatinic acid, chloroplatinic acid-olefin complexes, chloroplatinic 
acid-vinylsiloxane coordination compounds, platinum black, palladium, and 
rhodium catalysts. The quantity of catalyst to be employed depends on the 
type of catalyst and is arbitrary; however, it is generally 0.01 to 1000 
ppm platinum element, palladium element or rhodium element based on the 
total weight of organopolysiloxane. 
The composition of the present invention is produced by mixing components 
(a), (b), and (c). A known reaction retarder such as an acetylene compound 
or a nitrogen compound can be added to the composition of the present 
invention in order to provide working stability at room temperature. 
Although the cured product of the composition of the present invention has 
a high strength even without adding any reinforcing fillers, an additive 
which imparts a much higher strength to the composition can be added. 
Examples of additives are silicas such as dry-process silica, wet-process 
silica, fine quartz powder, and diatomaceous earth; polysiloxanes 
constituted of (CH.sub.2 .dbd.CH)(CH.sub.3).sub.2 SiO.sub.1/2 units and 
SiO.sub.2 units; metal oxides such as titanium oxide, zinc oxide, iron 
oxide, and cerium oxide; the hydroxides of rare earth elements; carbon 
black; graphite; silicon carbide; mica; talc; and pigments. 
The curing method is arbitrarily selected from among standing at room 
temperature, heating, and exposure to radiation. 
According to the present invention, an organopolysiloxane cured product is 
produced which has a high physical strength without the addition of a 
reinforcing filler and which can be advantageously used in such 
applications as electric-electronic parts, fiber coating, silicone rubber 
for manufacturing molds, various rubber moldings, rubber for coating 
electric wire, release paper, and medical applications. In addition, when 
the blending ratio of component (a) to component (b) satisfies the 
condition that the total alkenyl groups in component (a) to the total 
silicon-bonded hydrogen atoms in component (b), has a molar ratio of 1:0.3 
to 1:3, the resulting composition will generate little hydrogen gas during 
curing and it can thus be advantageously used in optical applications such 
as the coating of optical glass communication fibers.

The present invention will be explained using demonstrational examples. 
Parts and % in the examples denote weight parts and wt %, respectively. 
The viscosity was measured at 25.degree. C. The tensile strength and 
hardness were measured by the methods of JIS K6301. 
EXAMPLE 1 
100 parts dimethylhydrogensilyl-terminated polydimethylsiloxane with a 0.25 
Pa.multidot.s viscosity, 25 parts of a compound with the formula 
##STR5## 
and 0.5 part of a 3% isopropyl alcohol solution of chloroplatinic acid 
were placed in a flask and then reacted at 150.degree. C. for 2 hours. The 
unreacted components were then distilled under reduced pressure. The 
product polysiloxane, denoted below as polymer I, had a viscosity of 0.6 
Pa.multidot.s. Analysis of the product shows that it was a mixture of 
polymer in which both ends were blocked with the compound of the above 
formula and dimers of the polymer. That is, all polymer terminals were 
blocked with groups with the formula 
##STR6## 
Polymer I contains 1.68% vinyl groups. 
100 parts polymer I were thoroughly mixed with 8 parts 
trimethylsilyl-terminated dimethylsiloxane-methylhydrogensiloxane 
copolymer(dimethylsiloxane unit:methylhydrogensiloxane unit molar 
ratio=1:1, viscosity=0.01 Pa.multidot.s, denoted below as polymer II), 0.5 
part of a 3% isopropyl alcohol solution of chloroplatinic acid and 0.01 
part of 3-phenyl-1-butyne-3-ol to give a (Si--CH.dbd.CH.sub.2 in polymer 
I):(SiH in polymer II) molar ratio of 1:0.96 and this was then cured at a 
temperature of 150.degree. C. for 30 minutes. The cured product had a 
tensile strength of 8 kg/cm.sup.2 and a hardness of 40. The hydrogen gas 
generated during the curing process was gas chromatographically analyzed 
and was determined to be 0.8 .mu.L/g (at 25.degree. C. and 1 atm). 
COMISON EXAMPLE 1 
A cured product was manufactured by the same method as described in Example 
1 using 100 parts dimethylvinylsilyl-terminated polydimethylsiloxane with 
a viscosity of 0.6 Pa.multidot.s, 2.6 parts of polymer II of Example 1, 
0.5 part of a 3% isopropyl alcohol solution of chloroplatinic acid, and 
0.01 part 3-phenyl-1-butyne-3-ol. The resulting cured product had a 
tensile strength of 4 kg/cm.sup.2 and a hardness of 29. Hydrogen gas 
generation was determined by the method described in Example 1 was found 
to be 350 .mu.L/g (at 25.degree. C. and 1 atm). 
EXAMPLE 2 
100 parts of polymer I of Example 1 were thoroughly mixed with 24.9 parts 
of the following organohydrogenpolysiloxane with a 0.02 Pa.multidot.s 
viscosity (denoted below as polymer III), 
##STR7## 
0.3 part of a 3% 2-ethylhexanol solution of chloroplatinic acid, and 0.01 
part 3-methyl-1-butyne-3-ol to give a SiCH.dbd.CH.sub.2 :SiH molar ratio 
of 1.0:1.0 and this was then cured at an elevated temperature of 
130.degree. for 1 hour. The resulting cured product had a tensile strength 
of 5 kg/cm.sup.2 and a hardness of 30. Hydrogen gas generation was 
determined by the same method as described in Example 1 and was found to 
be 0.2 .mu.L/g (at 25.degree. C. and 1 atm). 
COMISON EXAMPLE 2 
100 parts of an organopolysiloxane with a 0.6 Pa.multidot.s viscosity with 
the formula 
##STR8## 
are thoroughly mixed with 19 parts polymer III of Example 2, and 0.3 part 
of a 3% 2-ethylhexanol solution of chloroplatinic acid and then processed 
by the same method as described in Example 1 to obtain a cured product. 
The cured product had a tensile strength of 2 kg/cm.sup.2 and a hardness 
of 22. Hydrogen gas generation was determined by the same method as 
described in Example 1 and was found to be 15 .mu.L/g (at 25.degree. C. 
and 1 atm). 
EXAMPLE 3 
100 parts dimethylhydrogensilyl-terminated polydimethylsiloxane with a 0.6 
Pa.multidot.s viscosity, 20 parts of a compound with the formula 
##STR9## 
and 0.5 part of a 3% isopropyl alcohol solution of chloroplatinic acid 
were placed in a flask and then reacted at 160.degree. C. for 2 hours. The 
unreacted components were distilled under reduced pressure. The 
polysiloxane product, denoted hereafter as polymer IV, had a viscosity of 
1.1 Pa.multidot.s and its polymer terminals were all confirmed by analysis 
to be blocked by groups with the formula 
##STR10## 
The vinyl group content was 0.70%. 
100 parts of polymer IV were thoroughly mixed with 2.0 parts of a compound 
with the formula 
##STR11## 
0.2 part of a 3% isopropyl alcohol solution of chloroplatinic acid, and 
0.005 parts 3-methyl-1-butyne-3-ol wherein the resulting SiCH.dbd.CH.sub.2 
:SiH molar ratio was 1.0:1.0 and this was then cured into a sheet at 
150.degree. C. for 20 minutes. The cured product had a tensile strength of 
9 kg/cm.sup.2 and a hardness of 35. Hydrogen gas generation was determined 
by the method described in Example 1 and was found to be 5.5 .mu.L/g (at 
25.degree. C. and 1 atm). 
COMISON EXAMPLE 3 
100 parts dimethylvinylsilyl-terminated polydimethylsiloxane with a 1.0 
Pa.multidot.s viscosity were thoroughly mixed with 1.1 parts of a compound 
with the formula 
##STR12## 
0.2 part of a 3% isopropyl alcohol solution of chloroplatinic acid, and 
0.005 part 3-methyl-1-butyne-3-ol and this was then cured into a sheet by 
the method described in Example 3. The cured product had a tensile 
strength of 6 kg/cm.sup.2 and a hardness of 24. Hydrogen gas generation 
was determined by the method described in Example 1 and was found to be 35 
.mu.L/g (at 25.degree. C. and 1 atm). 
EXAMPLE 4 
100 parts dimethylhydroxysilyl-terminated dimethylsiloxane-diphenylsiloxane 
copolymer (dimethylsiloxane unit:diphenylsiloxane unit molar ratio=90:10, 
viscosity=5.0 Pa.multidot.s) were mixed with 5 parts of a compound with 
the formula 
##STR13## 
and 0.1 part dibutyltin diacetate catalyst at room temperature in the 
ambient for 6 hours, heated at 70.degree. C. under reduced pressure to 
remove the acetic acid produced and then heated to 180.degree. C. under 
reduced pressure to remove the unreacted material. The product polymer V 
was confirmed by analysis to be blocked at both ends by groups with the 
formula 
##STR14## 
Its vinyl group content was 6.5% and its viscosity was 5.4 Pa.multidot.s. 
100 parts polymer V were thoroughly mixed with 36 parts of a cyclic 
organohydrogenpolysiloxane with the formula 
##STR15## 
1 part of a 2% 2-ethylhexanol solution of chloroplatinic acid, and 0.01 
part 3,5-dimethylhexyne-3-ol to give a SiCH.dbd.CH.sub.2 :SiH molar ratio 
of 1.0:1.0 and this was then cured into a sheet at an elevated temperature 
of 100.degree. C. for 1 hour. The cured product had a tensile strength of 
12 kg/cm.sup.2 and a hardness of 12. Hydrogen gas generation was 
determined by the method described in Example 1 and was found to be 0.5 
.mu.L/g (at 25.degree. C. and 1 atm). 
COMISON EXAMPLE 4 
100 parts dimethylvinylsilyl-terminated dimethylsiloxane-diphenylsiloxane 
copolymer (dimethylsiloxane unit:diphenylsiloxane unit molar ratio=90:10, 
viscosity=5.2 Pa.multidot.s) were thoroughly mixed with 12 parts of the 
cyclic organohydrogenpolysiloxane cited in Example 4, 1 part of a 2% 
2-ethylhexanol solution of chloroplatinic acid, and 0.01 part 
3,5-dimethylhexyne-3-ol and this was then heated at 100.degree. C. for 1 
hour. However, the mixture did not become rubber, but rather gelled and 
its tensile strength and hardness could not be measured.