JPS6017456B2 - Foamable silicone composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to foamable silicone compositions, particularly silicone compositions for producing silicone rubber foams having an open cell structure.

There are already many known methods for producing silicone rubber foams, including those that use a blowing agent because the silicone composition itself does not have a foaming function, and those that use a blowing agent that is generated during the condensation reaction of the silicone composition. However, the foams obtained by these methods have a closed cell structure, so in order to obtain open cells, the resulting foams must be mechanically The major drawback was that it required compression to form open cells by breaking the cell walls. In this known method, for example, a pinyl organopolysiloxane having a bare-bonded vinyl group is added to an organohydrodiene polysiloxane having a bare-bonded hydrogen group in the presence of a platinum-based catalyst. The former method is known (see Japanese Patent Publication No. 45-12675), in which the foam is cured by reaction and then foamed with decomposed gas from a thermally decomposable foaming agent added. The latter method has the drawback that the foaming ratio of the body is low, and the latter method uses a hydroxylated organopolysiloxane having a bare-bonded hydroxyl group and an organohydrogenpolysiloxane having a bare-bonded hydrogen group. When this kind of ionic compound is added to the method of condensation in the presence of an organic acid salt or a quaternary ammonium salt (refer to Japanese Patent Publication No. 44-1-7), when the composition comes into contact with high-temperature water or steam, Since depolymerization occurs and various properties as a silicone rubber are lost, there is a disadvantage that its uses are greatly restricted.

Regarding the latter method, there is a method in which the hydroxylated organopolysiloxane and the organohydrodiene polysiloxane are condensed in the presence of a rhodium compound (see Hakama Kosho 53-4822 Gen), and a method in which these are condensed in the presence of a platinum-based catalyst. Method of condensation with
, Special Publication No. Sho 52-4286, Futaru Ko Sho 53-48225) is also known, and in particular, this Hakama Ko Sho Madaraichi No. 48225 discloses that the weight of the silicone composition 10 described above is used for the purpose of obtaining a silicone foam having an open cell structure. Triorga/ having at least two vinyl groups in one molecule
A product is disclosed in which 85 parts by weight or more of a vinyl group-containing organopolysiloxane end-capped with a siloxy group is added, but in this case also, the open cell ratio is 60%.
However, only those with a closed cell ratio of 40% or more have been obtained. The present invention relates to a silicone composition that overcomes these disadvantages and is capable of producing a foam having a substantially open cell structure, which contains at least two silicon-bonded vinyl groups in one molecule. has,
100 parts by weight of an organopolysiloxane having a viscosity of 100,000 centipoise or less at 25q0, 'B' having at least two silicon-bonded hydrogens in one molecule, 25q
0.1 to 5 parts by weight of an organohydrodiene polysiloxane having a viscosity of 100,000 centipoise or less at zero, 0.5 to 5 parts by weight of a monohydroxylated silane having one poppy and bare bonded hydroxyl group in each 'C' molecule. and a catalytic amount of platinum or a platinum-based compound.

To explain this, the present inventors have conducted various studies on the production of silicone rubber foams, particularly silicone rubber foams with an open-cell structure, and have found that they can be produced without using any particular blowing agent due to the condensation reaction. Foaming with generated gas is advantageous for industrial production. An organohydrogenpolysiloxane having at least two hydroxyl groups in one molecule is mixed with a monohydroxysilane having one hydroxyl group in one molecule, and these are reacted in the presence of a platinum catalyst. and an addition reaction between the vinylorganopolysiloxane and the organohydrogenpolysiloxane, as well as an addition reaction between the vinylorganopolysiloxane and the organohydrogenpolysiloxane.

The curing reaction and foaming of the silicone rubber proceed simultaneously through the condensation reaction with the xylated silane, and because the hydroxyl group-containing silicone compound that generates foaming gas through this condensation reaction is specifically designated as mo/hydroxyl silane, The silicone foam obtained here has a closed cell ratio of 30% or less, usually 5% or less, and is essentially an open cell structure, and the expansion ratio of this silicone foam is also 200% or more. The present invention was completed by confirming that it was possible to obtain 400% or more. The reason why the silicone rubber foam obtained by blending this hydroxylated silane becomes an open-cell structure is because when hydroxylated siloxane is used as the hydroxylated silicone, which is a gas generation source due to the condensation reaction, it itself participates in the crosslinking reaction. This makes it difficult for the gas generated to exit the system, but when hydroxylated silane is used, it does not participate in crosslinking, making it easier for the gas generated to exit the system, resulting in open cells. Presumed. The arc component as the main component constituting the silicone composition of the present invention is a vinylorganopolysiloxane having at least two silicon-bonded vinyl groups in one molecule, and has a viscosity of 100,000 centipoise or less at 25°C. be taken as a thing.

The bare organic groups other than vinyl groups in this vinylorganopolysiloxane include methyl group, ethyl group, propyl group,
A single prime number such as isopropyl group, butyl group, tertiary butyl group, bentyl group, hexyl group, cyclohexyl group
It is a monovalent organic group selected from six alkyl groups or aryl groups such as phenyl groups, but the vinyl group may be present at the end of the molecular chain, in the chain, or both. The molecular shape of is linear,
It may be either cyclic or branched. Also, this {B
}The organohydrogenpolysiloxane as a component is said to have at least two silicon-bonded hydrogen groups in its molecule, but other than these hydrogen groups, the bare and elementary-bonded organic groups are the same as in the above-mentioned wind component. A monovalent organic group selected from the following types.

In addition, the elementary bonded hydrogen groups in this organohydrodiene polysiloxane may be present at either the end of the molecular chain, the main chain, or both, and the molecular structure of this siloxane also varies. It may be straight mirror-shaped, circular, or branched. However, the viscosity of this product is 1000
00 centipoise or less, preferably 30,000 centipoise or more. The amount of siloxane added is 0.1 to 5 parts by weight based on 10 parts by weight of vinylorganopolysiloxane as a wind component.
Preferably it is 5 to 2 parts by weight. The monohydroxylated silane as component C' constituting the silicone composition of the present invention is an organosilane having one bare-bonded hydroxyl group in its molecule, and silicon-bonded organic groups other than this hydroxyl group are The wind component is selected from the same components as those of the wind component.

The amount of this monohydroxylated silane added is 0 to 10 parts by weight of the vinylorganopolysiloxane as the component.
．． The amount is 5 to 5 parts by weight, preferably 1.0 to 2 parts by weight, and may be determined by taking into consideration the amount of the component {B} described above. In addition, the platinum catalyst as a supporting component used in the present invention is responsible for the addition reaction between the wind component and the bending component.'B)
This is to carry out a condensation reaction between the component and the 'C} component, and this can be carried out using metallic platinum alone, supported on a carrier such as silica gel or powdered charcoal, or platinum chloride, or a mixture of platinum and chloroplatinic acid. Salts, platinum-olefin collars, etc. are exemplified, but any known catalyst of this type may be used, and the amount added is based on 1 million parts by weight of the silicone composition consisting of the above components 1 as platinum amount
-20 parts by weight may be used.

The silicone composition of the present invention has the above-mentioned ■, 'B', [q
and obtained by uniformly mixing the dish ingredients,
Since the reaction proceeds even at room temperature, these must be mixed before use.

This composition also contains 3-methyl-1-pentyne-3, a compound known as a compound that suppresses the catalytic ability of platinum catalysts, for the purpose of controlling foaming accompanying the curing reaction and condensation reaction.
-ol-, acetylenic alcohol such as 3-methyl-1-butyn-3-ol, or a polymethylvinylsiloxane cyclic compound obtained by hydrolysis of methylvinyldichlorosilane, etc. may also be added, and silicone rubber may also be added. Appropriate amounts of inorganic fillers that are commonly added to compositions for use, such as finely powdered silica, diatomaceous earth, calcium silicate, calcium carbonate, and titanium dioxide, may be added as necessary. The reaction of these ■, 'B}, Ni and dish compositions starts immediately when they are mixed, but
In this reaction, the curing reaction due to the addition reaction between the harmful component and the [B-component] and the foaming phenomenon due to the condensation reaction between the 'B} component and the 'C} component proceed simultaneously. A silicone rubber foam having a structure can be easily and reliably obtained.

Note that this foaming is usually done inside a foaming case,
At this time, this may be carried out under heating in order to accelerate the curing of the target product and improve the physical properties of the silicone rubber. The silicone rubber foam obtained in this way has a substantially open cell structure with a closed cell ratio of 30% or less, particularly 5% or less, which means that its expansion ratio is also 200% or more.
In particular, since it is 400% or more, there is no need to collapse the closed cells by mechanical compression after the foaming process.
It can be used as is for various purposes, and silicone rubber also has properties such as electrical insulation, heat resistance,
In addition to flame resistance and self-extinguishing properties, this molded product also has excellent cushioning properties, making it useful as a cushioning material for various electrical devices, as well as flame-resistant wall materials, architectural sealants, and food containers. It can be rationally used as a noncombustible material for various rolls, passes, trains, aircraft, etc., and also as various padding materials and cushioning materials. Next, examples of the present invention will be given, and all parts in the examples indicate parts by weight.

Example 1 100 parts of methylvinylpolysiloxane with a degree of polymerization of about 580, consisting of 99.7 mol% of dimethylsiloxane units and 0.3 mol of dimethylvinylsiloxy units, 95.0 parts of methylhydrogensiloxy units and 5.0 parts of trimethylsiloxy units. Methylhide with a degree of polymerization of about 40 and consisting of 0 mol%.

Diene polysiloxane 12. part, trimethylsilanol 5. 0.01 part of chloroplatinate of symmetrical divinyltetramethyldisiloxane containing about 30% by weight of platinum, and 0.1 part of a polymethylvinylsiloxane cyclic compound.
When the two parts were mixed at room temperature, the mixture immediately started to react to form a silicone rubber foam. When this foam was examined for its foaming state, it was an open cell with an expansion ratio of 290% and a closed cell ratio of 5%, and was found to be a good silicone rubber foam.

Example 2 Diorganopolysiloxane with a degree of polymerization of about 100, consisting of 68.0 mol% of dimethylsiloxy units, 30.0 mol% of diphenylsiloxy units, and 2.0 mol% of dimethylvinylsiloxy units, 10 parts of methylhydrogensiloxy unit 80.0 mol% and trimethylsiloxy unit 20
．． Methylhide with a degree of polymerization of about 10 and consisting of 0 mol%.

Diene polysiloxane 13. $ parts, 3.5 parts of trimethylsilanol, 0.01 part of chloroplatinate of symmetrical dipinyltetramethyldisiloxane containing about 3% by weight of platinum, and 0.01 part of polymethylvinylsiloxane cyclic compound at room temperature. When mixed to make a foam, the foaming ratio was 3.
00%, a sponge-like silicone rubber foam having a closed cell ratio of 10% and a substantially open cell structure was obtained. Example 3 Trimethylsilyl group-terminated vinylmethylpolysiloxane with a degree of polymerization of about 540, consisting of 99.0 mol% dimethylsiloxy units and 1.0 mol% methylvinylsiloxy units, 10 anchor parts, 95.0 mol% methylhydrogensiloxy units and 12.1 parts of methylhydrodiene polysiloxane with a degree of polymerization of about 40, consisting of 5.0 mol% of trimethylsiloxy units, 17.8 parts of diphenylmethylsil/ol, and symmetrical divinyl containing about 3% by weight of platinum. 0.01 part of chloroplatinate of tetramethyldisiloxane and 0.006 part of polymethylpinylsiloxane cyclic compound
When a foam was prepared by mixing the two parts at room temperature, a sponge-like silicone rubber foam having a continuous cell structure with an expansion ratio of 290% and a closed cell ratio of 5% was obtained.

Comparative Example 1 In place of 5.0 parts of trimethylsilanol in Example 1, hydroxyl group-terminated dimethyl with a degree of polymerization of about 10 and consisting of 80.0 mol% of dimethylsiloxy units and 20.0 mol% of dimethylhydroxylsiloxy units was used. Siloxane 1
A foam was made in the same manner as in Example 1 except that 9.5 parts and 1.5 parts of trimethylsilanol were added. The resulting silicone rubber foam had a foaming rate of about 300%. had a high closed cell ratio of 76%, and did not substantially have an open cell structure.

Comparative Example 2 In place of 3.5 parts of trimethylsilanol in Example 2, hydroxyl-terminated dimethylsiloxane 1 having a degree of polymerization of about 10 and consisting of 80.0 mol% of dimethylsiloxy units and 20.0 mol% of dimethylhydroxylsiloxy units was used.
A foam was produced in the same manner as in Example 2 except that 9.4 parts of silicone rubber was added, and the foaming rate of the obtained silicone rubber foam was about 230%; %, and did not substantially have an open cell structure.

Claims (1)

[Claims] 1 (A) 100 parts by weight of an organopolysiloxane having at least two silicon-bonded vinyl groups in one molecule and having a viscosity of 100,000 centiboise or less at 25°C (B) At least two silicon-bonded hydrogens in one molecule organohydrodiene polysiloxane having a viscosity of 100,000 centipoise or less at 25° C.
1 to 50 parts by weight (C) 0.5 to 50 parts by weight of a monohydroxylated silane having one silicon-bonded hydroxyl group in one molecule (A) A catalytic amount of platinum or a platinum-based compound. A foamable silicone composition.