JP3209897B2 - Foamable silicone rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamable silicone rubber composition, and more particularly to a sponge-like foam having a long pot life, foaming and curing by heating, and having uniform cells. The present invention relates to a foamable silicone rubber composition capable of forming a foamed cured product.

[0002]

2. Description of the Related Art A foamable silicone rubber composition capable of forming a sponge-like foamed cured product is roughly classified into a silicone rubber composition having no foaming mechanism and a foaming agent, and a silicone rubber composition. Some curing mechanisms themselves exhibit foaming properties (for example, see Japanese Patent Publication No. 45-12675).

[0003] Of these, those having a foaming property in the curing mechanism itself generally have a short pot life until foaming and curing, that is, a short pot life. Polymethylvinyl cyclic compounds (JP-B-52-42826), acetylene alcohol-based compounds (JP-B-53-5342, JP-B-53-24454, JP-B-53-48226, and JP-B-3-26216) No. etc.) to extend the pot life.

[0004]

However, the pot life of the foamable composition containing the above curing catalyst inhibitor is at most about 20 minutes from the time when the composition is prepared by mixing at room temperature. There is a problem that it is only. Further, when the amount of the curing catalyst inhibitor is increased in order to extend the pot life, a problem arises in that the cells of the obtained sponge-like foamed cured product are non-uniform and too large. Therefore, a foamable silicone rubber composition having a long pot life and capable of forming a sponge-like foamed cured product having uniform cells is demanded.

[0005] The present inventors have conducted intensive studies to meet such demands. As a result, a silicone rubber composition which forms a foamed cured product by a dehydrogenation reaction between a SiH group and a SiOH group is added to a hydroperoxy group as a catalyst inhibitor. It has been found that the addition of an organic compound containing a compound has a long pot life and forms a sponge-like foamed cured product having uniform cells when heated.

Accordingly, an object of the present invention is to provide a foamable silicone rubber composition which has a long pot life, foams and cures when heated, and forms a sponge-like foamed cured product having uniform cells. It is in.

[0007]

According to the present invention, (A) the following general formula (1): R _a (OH) _b SiO _{[4- (a + b)] / 2} (1) Is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, and a and b are an integer of 0 to 2, provided that a + b is 1 to 3. And b is an integer of 1 to 3, wherein the SiH group in the organopolysiloxane ( B) component having at least two units represented by the following formula in one molecule corresponds to one SiOH group in the component (A).
The amount to be 2 to 50 equivalents per amount, (C) a platinum group metal catalyst, foaming containing 1～5,000Ppm, the organic compound (A) component comprising at least one hydroperoxy group (D) A silicone rubber composition is provided.

Component (A) The organopolysiloxane of the component (A) is a base component of the composition of the present invention, and has at least two units represented by the general formula (1) in one molecule. As can be seen, at least two Si atoms per molecule
It has an OH group. That is, the SiOH group undergoes a dehydrogenation reaction with the SiH group of the component (B) described later, whereby a sponge-like cured product is formed.

In the general formula (1), the group R is a substituted or unsubstituted monovalent hydrocarbon having no aliphatic unsaturated bond, and has 1 to 1 carbon atoms such as methyl, ethyl and propyl. C6-10 cycloalkyl groups such as an alkyl group having 6 carbon atoms, cyclohexyl group and the like, aryl groups having 6 to 10 carbon atoms such as phenyl group and tolyl group, benzyl group, 2
-Phenylethyl group, an aralkyl group having 7 to 12 carbon atoms such as a 2-phenylpropyl group, and a group in which at least a part of hydrogen atoms of these groups is substituted with a halogen atom or the like,
For example, groups such as a 3,3,3-trifluoropropyl group can be exemplified. Among these, a methyl group, a phenyl group, a 3,3,3-trifluoropropyl group, and particularly a methyl group are preferred.

In the general formula (1), a and b are a + b
A is an integer of 0 to 2 and b is an integer of 1 to 3, provided that b is an integer of 1 to 3. Therefore, the unit represented by the general formula (1), in other words, the unit having a SiOH group, may be present at the terminal of the molecular chain or may be present in the middle of the molecular chain.

The organopolysiloxane of the component (A) is
As long as it has at least two units of the general formula (1) in one molecule, it can have any other organosiloxane unit. Examples of such other organosiloxane units include: The following general formula (3): _Re SiO _{(4-e) / 2} (3) In the formula, R is the same as described above, and e is an integer of 1 to 3, and a unit represented by the following formula is exemplified. This general formula (3)
As R in the above, the same as those exemplified in the general formula (1) can be exemplified.

The molecular structure of the organopolysiloxane of the component (A) may be any of linear, branched, cyclic, network and the like, but usually a linear one is used.
Not only one kind but also a mixture of two or more kinds may be used. Further, the viscosity of the organopolysiloxane is not particularly limited. At 25 ° C., the viscosity ranges from a low viscosity of about 100 centipoise to a high viscosity called silicone raw rubber (viscosity: about 100,000,000 centipoise), preferably 100 to 100,000. Centipoise can be used.

Representative examples of the organopolysiloxane of the component (A) include, for example, formula (4): HO (R ¹ R ² SiO) _L H (4) or formula (5): (R ³ ) ₃ SiO (R ¹ R ² SiO) _M [R ¹ Si (OH) O] _N Si (R ³ ) ₃ (5) wherein R ¹ and R ² may be the same or different;
An unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, R ³ is an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, and L is 20 to 3,000, preferably 200 M is an integer of 2 to 20, N is 3 to 20
And an organopolysiloxane represented by the following formula: Among them, typical examples of the organopolysiloxane suitably used include, but are not limited to,
For example, dimethylorganopolysiloxane terminated at both ends with silanol groups. The organopolysiloxane of the above formula (4) and the organopolysiloxane of the above formula (5) may be used as a mixture.

Component (B) The organopolysiloxane of the component (B) functions as a so-called crosslinking agent, and has at least two units represented by the general formula (2) in one molecule. . That is, this organopolysiloxane has two or more SiH groups in one molecule, and this SiH group undergoes a dehydrogenation reaction with the SiOH group in the organopolysiloxane of the above-mentioned component (A) to obtain a cured product. Is formed. In addition, since hydrogen serving as a foaming source is generated by the dehydrogenation reaction, foaming occurs at the same time as curing, and the resulting cured product becomes a sponge-like foam.

The group R in the general formula (2) is the same as the R in the general formula (1), and examples thereof are the same as those exemplified for the general formula (1). Further, in the general formula (2), c and d are each an integer of 0 to 2 and d is an integer of 1 to 3, provided that c + d is 1 to 3. Therefore, the unit represented by the general formula (2), in other words, the unit having a SiH group, may be present at the terminal of the molecular chain, or may be present in the middle of the molecular chain. Also, they may be present in both of them. further,
Examples of the unit other than the general formula (2) include a unit represented by the general formula (3).

The molecular structure may be any of linear, branched, cyclic, network and the like, but usually a linear or cyclic one is used. Also, not only one kind,
More than one kind may be mixed and used. Further, the viscosity is not particularly limited, but generally, at 25 ° C, 1 to
It is preferably 10,000 centipoise, especially 1-1,500 centipoise.

The organopolysiloxane of the component (B) is, for example, a compound represented by the following formula (6): R ⁴ (R ⁴ R ⁴ SiO) _x (R ⁴ HSiO) _Y Si (R ⁴ ) ₃ (6) ⁴ is a substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond, x is an integer of 0 to 100, and y is 2 to 2
100 integer].

The component (B) is usually used in such an amount that the SiH group in the component (B) is 2 to 50 equivalents, particularly 5 to 20 equivalents, per equivalent of the SiOH group in the component (A). Is done. If the amount of Si—H groups is too small, sufficient foaming cannot be achieved, and if the amount is too large, unreacted Si
Since a large number of H groups remain, the physical properties of the cured product (foam) are reduced. Generally, the component (B) is used in an amount of 0.1 to 50 parts by weight, especially 2 to 3 parts by weight, per 100 parts by weight of the component (A) within a range that satisfies the above-mentioned quantitative conditions for the Si—H group.
It is preferred that it be blended in an amount of 0 parts by weight.

Component (C) The platinum group metal-based catalyst of component (C) is a catalyst for accelerating the above-mentioned dehydrogenation-hardening reaction between the SiOH group and the SiH group. Rhodium-based ones are known, but platinum-based ones from the economical point of view, for example, silica, alumina or fine particulate platinum metal adsorbed on a carrier such as silica gel, platinic chloride, chloroplatinic acid, Complexes of chloroplatinic acid hexahydrate with olefins or divinyldimethylpolysiloxane, alcohol solutions of chloroplatinic acid hexahydrate, and the like are preferably used.

The platinum group metal-based catalyst is preferably used in an amount of usually 1 to 500 ppm, particularly 10 to 100 ppm, as platinum group metal, based on the component (A).
If it is less than 1 ppm, the curing reaction is not effectively promoted, and curing and foaming may be insufficient.
Even if it is blended in a larger amount, the curing reaction is not accelerated further and it is uneconomical.

Component (D) The component (D) is an organic compound containing at least one hydroperoxy group (—OOH), and functions as a catalyst inhibitor that suppresses the catalytic effect of the component (C). . That is, by blending such components, the pot life of the composition can be extended, and further, by heating the composition, it is possible to obtain a sponge-like cured product having foam-cured and uniform cells. It becomes.

Specific examples of the organic compound (D) include, but are not limited to, methyl ethyl ketone hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide,
1-hydroxycyclohexyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, decalin hydroperoxide, 1,
Examples thereof include 1,2,2-tetramethylpropyl hydroperoxide, p-menthane hydroperoxide, pinane hydroperoxide and the like, and these can be used alone or in combination of two or more. . Among them, preferred components (D) are methyl ethyl ketone hydroperoxide, cumene hydroperoxide, and t-butyl hydroperoxide.

In general, the component (D) is preferably added in an amount of 1 to 5,000 ppm, particularly 10 to 1,000 ppm, based on the component (A). If it is less than 1 ppm, the effect of suppressing the catalyst becomes insufficient and the pot life cannot be effectively extended. On the other hand, if the amount is more than 5,000 ppm, curing and foaming require long-time heating, which is inefficient.

Other Ingredients In the present invention, the above-mentioned (A) to (D) are used as long as the object of the present invention of extending the pot life and forming a foam having uniform cells is not impaired.
In addition to the components, various additives blended in conventionally known foamable silicone rubber compositions can be blended as needed. For example, a vinyl group-containing organopolysiloxane can be blended to increase the reinforcing property of the sponge-like cured product, and fumed silica, precipitated silica,
Inorganic fillers such as diatomaceous earth, quartz fine powder, iron oxide, titanium oxide, aluminum oxide, aluminum silicate, zinc white, carbon black, etc .; antistatic agent; heat-resistant agent; flame retardant; pigment; glass fiber; Can be blended. In particular, the inorganic filler may be untreated, or may be surface-treated with an organosilicon compound such as organochlorosilane, organopolysiloxane, or hexaorganosilazane.

Foamable Silicone Rubber Composition The composition of the present invention can be easily prepared by uniformly mixing the above-mentioned essential components (A) to (D) and various additives optionally blended at room temperature. Prepared. This composition has a significantly long pot life. For example, the pot life of a conventionally known foamable silicone composition is about 20 minutes at 25 ° C., whereas the pot life of this composition is 25 minutes.
C. for 24 hours or more.

The composition is molded using a known molding apparatus such as injection molding or injection molding.
By heating at 0 ° C., for example, 120 ° C. for 1 to 120 minutes, foaming and curing occur, forming a sponge-like cured product. The resulting spongy cured product has uniform cells,
Generally speaking, it has a diameter of 1 mm or less.

[0027]

EXAMPLES In the following Examples and Comparative Examples, "parts" means "parts by weight", and the viscosity is a value at 25 ° C. Example 1 100 parts of dimethylpolysiloxane terminated with silanol groups at both ends having a viscosity of 20,000 cP, 5 parts dimethylpolysiloxane terminated with silanol groups at both ends having a viscosity of 30 cP, and 10 parts of fine powder silica (Aerosil R972, trade name of Degussa) The mixture was uniformly mixed at room temperature to obtain a silicone base (1). To this silicone base (1), 0.4 part of divinylmethylpolysiloxane complex of chloroplatinic acid hexahydrate and 0.03 part of methyl ethyl ketone hydroperoxide were uniformly mixed, and further, (CH ₃ ) ₃ SiO- [Si CH ₃ ( H) O] ₃₈ -Si (CH ₃ ) ₃ , an organohydrogenpolysiloxane having a viscosity of about 10 cP and a silanol group-containing polysiloxane
4 parts were added and mixed so as to have about 10 equivalents of Si-H groups with respect to the amount of H groups, and the foamable silicone rubber composition (having a viscosity of 1,
200 poise).

When the above composition was foamed and cured at 120 ° C. for 30 minutes, a sponge-like cured product having uniform cells having a diameter of 1 mm or less and a density of 0.35 g / cm ³ was obtained. Was. After this composition was prepared and stored at 25 ° C. for 24 hours, the viscosity was 1,200 poise, and no foaming was confirmed. Further, the composition after storage was heated and foamed and cured in the same manner as described above.
A sponge-like cured product having uniform cells of not more than mm and a density of 0.38 g / cm ³ was obtained.

Comparative Example 1 An expandable silicone rubber composition was prepared in the same manner as in Example 1, except that 0.05 parts of 1-ethynyl-1-cyclohexanol was used instead of methyl ethyl ketone hydroperoxide. When this composition was foamed and cured under the same conditions as in Example 1, the cells of the obtained sponge-like cured product were non-uniform, and bumpy foam was also confirmed on a part of the surface.

Comparative Example 2 A foamable silicone rubber composition was prepared in the same manner as in Example 1, except that 0.05 parts of 3,5-dimethyl-1-hexyn-3-ol was used instead of methyl ethyl ketone hydroperoxide. Was prepared. When this composition was foamed and cured under the same conditions as in Example 1,
The cells of the obtained sponge-like cured product were non-uniform, and bumpy foaming was also confirmed on a part of the surface.

Example 2 Diphenyl thiol terminated with a silanol group at both ends having a viscosity of 20,000 cP
100 parts of dimethylpolysiloxane copolymer [OSi (C ₆
H ₅ ) ₂ units content 7 mol%], 5 parts of dimethylpolysiloxane terminated with silanol groups at both ends having a viscosity of 30 cP, and 10 parts of finely divided silica (same as in Example 1) were uniformly mixed at room temperature. Was used as a silicone base (2). To this silicone base (2), 0.4 part of divinylmethylpolysiloxane complex of chloroplatinic acid hexahydrate and 0.05 part of methyl ethyl ketone hydroperoxide were uniformly mixed, and the organohydrogenpolysiloxane used in Example 1 was further mixed. 4 parts were added and mixed so that about 10 equivalents of Si—H groups with respect to the amount of OH groups of the silanol group-containing polysiloxane were added to form a foamable silicone rubber composition (viscosity of 1,200 poise).
Was prepared.

When the above composition was foamed and cured at 120 ° C. for 30 minutes, a sponge-like cured product having uniform cells having a diameter of 1 mm or less and a density of 0.31 g / cm ³ was obtained. Was. After the composition was prepared and stored at 25 ° C. for 24 hours, the viscosity was 1200 poise, and no foaming was confirmed. Further, when the composition after storage was heated and foamed and cured in the same manner as described above, the diameter was 1 mm in the same manner.
A sponge-like cured product having the following uniform cells and a density of 0.32 g / cm ³ was obtained.

Example 3 Divinylmethylpolysiloxane complex of chloroplatinic acid hexahydrate 0.4 was added to the silicone base (2) prepared in Example 2.
Parts, t-butyl hydroperoxide 0.06 parts, and then uniformly mixed with 4 parts of the organohydrogenpolysiloxane used in Example 1, as in Example 2, to form a foamable silicone rubber composition. (Viscosity of 1,200 poise).

When the above composition was foamed and cured at 120 ° C. for 30 minutes, a sponge-like cured product having uniform cells having a diameter of 1 mm or less and a density of 0.38 g / cm ³ was obtained. Was. After the composition was prepared and stored at 25 ° C. for 24 hours, the viscosity was 1200 poise, and no foaming was confirmed. Further, when the composition after storage was heated and foamed and cured in the same manner as described above, the diameter was 1 mm in the same manner.
A sponge-like cured product having the following uniform cells and a density of 0.42 g / cm ³ was obtained.

Example 4 A divinylmethylpolysiloxane complex of chloroplatinic acid hexahydrate was added to the silicone base (1) prepared in Example 1.
Parts, methyl ethyl ketone hydroperoxide 0.05
Parts of the organohydrogenpolysiloxane 4 used in Example 1 as in Example 1.
Parts of the foamable silicone rubber composition (viscosity
1,200 poise).

When the above composition was foamed and cured at 120 ° C. for 30 minutes, a sponge-like cured product having uniform cells having a diameter of 1 mm or less and a density of 0.35 g / cm ³ was obtained. Was. After the composition was prepared and stored at 25 ° C. for 24 hours, the viscosity was 1,200 poise and no foaming was confirmed. Further, when the composition after storage was heated and foamed and cured in the same manner as described above, the diameter was 1 mm in the same manner.
A sponge-like cured product having the following uniform cells and a density of 0.41 g / cm ³ was obtained.

Comparative Example 3 100 parts of dimethylpolysiloxane having both ends having a viscosity of 20,000 cP and blocked with silanol groups and having an average of 2 mol of vinyl groups per molecule, and a dimethyl terminated with a silanol group having both ends having a viscosity of 30 cP. 5 parts of polysiloxane and 10 parts of finely divided silica (same as in Example 1) were uniformly mixed at room temperature to obtain a silicone base (3). 0.4 parts of divinylmethylpolysiloxane complex of chloroplatinic acid hexahydrate and 0.03 parts of methyl ethyl ketone hydroperoxide were uniformly mixed with the silicone base (3).
4 parts of an organohydrogenpolysiloxane having 0 cP and having about 1.5% by weight of hydrogen were added and mixed. Immediately after the mixture thus obtained, the reaction started and gelled.

[0039]

The foamable silicone rubber composition of the present invention has an advantage that the pot life is remarkably long, and a cured sponge having uniform cells can be obtained by curing by heating. .

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kaio Inoue 1-10 Hitomi, Matsuida-cho, Usui-gun, Gunma Prefecture Inside the Silicone Electronic Materials Research Laboratory, Shin-Etsu Chemical Co., Ltd. (56) References JP-A-8-59868 ( JP, A) Japanese Patent Publication No. 3-26216 (JP, B2) Japanese Patent Publication No. 53-24454 (JP, B2) Japanese Patent Publication No. 53-48226 (JP, B2) "Silicone Handbook" edited by Kunio Ito Published by Nikkan Kogyo Shimbun 1990 8.31 Page 347, Page 387 (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 83/06 C08K 5/14 C08L 83/05 C08J 9/02

Claims (2)

(57) [Claims] (A) The following general formula (1): R _a (OH) _b SiO _{[4- (a + b)] / 2} (1) wherein R has an aliphatic unsaturated bond. A and b are unsubstituted or substituted monovalent hydrocarbon groups, provided that a + b is 1-3.
a is an integer of 0 to 2, b is an integer of 1 to 3, an organopolysiloxane having at least two units in one molecule represented by the following formula: (B) the following general formula (2): R _c (H) _d SiO _{[4- (c + d)] / 2} (2) wherein R is the same as above, and c and d are provided that c + d is 1-3.
c is an integer of 0 to 2, d is an integer of 1 to 3, and the SiH group in the organopolysiloxane (B) component having at least two units represented by the following formula in the molecule is (A)
The amount of the SiOH groups per equivalent 2 to 50 equivalents in component, 1～5,000Ppm against (C) a platinum group metal catalyst, (D) an organic compound containing at least one hydroperoxy group (A) component A foamable silicone rubber composition comprising: 2. A composition obtained by curing the composition according to claim 1 .
Foamed cured product.