JPH0721080B2 - Expandable silicone rubber composition and cured product - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a foamable silicone rubber composition, and in particular, a foamable silicone rubber that can be injected into a narrow space such as a through hole and has sufficient rubber strength after curing. It relates to a composition and a cured product.

<< Prior Art >> Various foamable silicone rubber compositions are already known. In particular, those having a foaming mechanism that cures into a sponge at the same time by the gas generated in the condensation reaction in the curing mechanism of the silicone rubber, does not require the use of a special foaming agent and simplifies the blending of the rubber. It has many advantages such as no decomposition residue of the foaming agent remaining on the rubber after foaming. The curing mechanism of the silicone rubber having this foaming mechanism is that a hydroxylated organopolysiloxane having a hydroxyl group bonded to a silicon atom and an organohydrogenpolysiloxane having a hydrogen atom bonded to a silicon atom are combined with platinum chloride such as chloroplatinic acid. The compound is dehydrogenated in the presence of a compound or an organic tin compound to cure and foam to form a sponge.

This type of foamable silicone rubber composition reinforces a copolymer resin composed of R ₃ SiO _0.5 units (R is a monovalent hydrocarbon group) and SiO ₂ units from the viewpoint of maintaining sufficient rubber strength after curing and foaming. It can be used in combination to improve performance (US Pat. No. 4,418,
157), adding reinforcing fillers such as fumed silica. However, in the former case, the heat resistance after curing is poor, and the silicone rubber sponge becomes hard and does not show sufficient strength after aging or heat deterioration, whereas in the latter case, a reinforcing filler is simply added. However, when sufficient hydroxyorganopolysiloxane for foaming is added, the flowability of the foamable silicone rubber before curing and foaming will be lost, and it will not be possible to inject into a narrow space.

<Problems to be Solved by the Invention> As a result of intensive investigations by the present inventors to eliminate these conventional inconveniences, a specific hydrophobic silica and a hydroxylated organopolysiloxane having a specific structure are used in combination in a foamable silicone rubber composition. By doing so, a sponge-like silicone rubber cured product having a composition before curing having good fluidity, foaming and curing at a high magnification at room temperature or under heating, and having sufficient rubber strength after curing is obtained. The inventors have found what can be obtained and have completed the present invention.

Accordingly, an object of the present invention is to provide a foamable silicone rubber composition having good fluidity before curing, foaming and curing at a high magnification at room temperature or under heating, and having sufficient rubber strength after curing, and a foamable silicone rubber composition. Another object of the present invention is to provide a sponge-like cured silicone rubber product obtained by curing.

<< Means for Solving the Problems >> The above object of the present invention is to have a viscosity at 25 ° C of 100 to 20.
Organopolysiloxane having a molecular weight of 0,000 cs and containing at least two alkenyl groups in one molecule: 100 parts by weight, a viscosity at 25 ° C. of 1 to 10,000 cs, and a hydrogen atom directly bonded to a silicon atom in one molecule ( Organohydrogenpolysiloxane having at least three (SiH bonds) is 1 to 1 with respect to the alkenyl group contained in the component.
Hydrophobic silica whose surface is treated with an amount capable of providing 50 times moles of ≡SiH groups, a catalytic amount of a platinum compound, and organic silicon, and carbon adsorbed on the surface is 2% by weight or more: 5 to 50 parts by weight and a silanol group-containing organocyclopolysiloxane represented by the following structural formula: 1 to 80 parts by weight It is achieved by a foamable silicone rubber composition comprising:

In the organopolysiloxane having the alkenyl group bonded to at least two silicon atoms in one molecule, which is the first component constituting the composition of the present invention, the alkenyl group is preferably present at least at the end of the molecular chain. As such an organopolysiloxane, for example ,; Or And the like.

Here, R ³ is a alkenyl group having 2 to 6 carbon atoms such as vinyl group and allyl group, R ² is an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group and butyl group, phenyl group and tolyl group. C6-10 aryl groups such as groups, or groups in which one or all of the hydrogen atoms bonded to the carbon atoms of these groups have been replaced with halogen atoms (eg, chloromethyl groups, 3,3,3-
The same or different unsubstituted or substituted monovalent saturated hydrocarbon group selected from (trifluoropropyl group) and the like. Also, m is an integer from 50 to 2,000, and n is 0 to 200.
Is an integer.

The viscosity of the above organopolysiloxane at 25 ° C is 100
~ 200,000cs, but especially 500-100,
It is preferably 000cs. This means that if the viscosity at 25 ° C is less than 100cs, the silicone rubber after curing and foaming cannot have sufficient strength and elongation, while if the viscosity at 25 ° C exceeds 200,000cs, the fluidity of the composition before curing becomes high. This is because it becomes defective.

Further, the organopolysiloxane is preferably an essentially linear diorganopolysiloxane, but it may have a partially branched structure.

Next, since the organohydrogenpolysiloxane as the second component in the present composition acts as a cross-linking agent for the above-mentioned organopolysiloxane as the first component, at least three organohydrogenpolysiloxanes are present in the molecule. It is necessary to include a hydrogen atom (≡SiH bond) directly connected to the silicon atom.

Examples of the organohydrogensiloxane include those represented by the general formula (In the formula, R ⁴ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms, a and b are positive numbers, and a + b is 1.
An organohydrogensiloxane having at least 3 silicon-hydrogen bonds in the molecule represented by (indicating 0 to 3.0) (R ⁴ is a methyl group, an ethyl group, a propyl group, a butyl group or the like having 1 to 6 carbon atoms). It is preferably an aryl group having 6 to 10 carbon atoms such as an alkyl group, a phenyl group and a tolyl group), which has a conventionally known linear structure, cyclic structure or branched chain structure. Either may be used.

Furthermore, since this organohydrogenpolysiloxane is preferably made to have a lower molecular weight than the first component in order to be compatible with the first component, the viscosity at 25 ° C. is 1 to 10,000 cs, preferably 5 to 1,000 cs. Must be in the cs range.

The organohydrogenpolysiloxane is blended in an amount of 1 to 50 times mol, preferably 5 to 40 times mol of the ≡SiH group with respect to the alkenyl group contained in the organopolysiloxane component as the first component. It is the amount that can be done. If the amount is less than 1 time, the foaming silicone rubber composition will be insufficiently cured and foamed, and if it exceeds 50 times, the silicone rubber will become brittle after curing and foaming.

The platinum or platinum compound used as the third component in the present invention is known as an addition reaction catalyst, for example, platinum black, platinum supported on silica, carbon black, etc., chloroplatinic acid, alcohol solution of chloroplatinic acid. , A complex salt of chloroplatinic acid and an olefin or vinyl siloxane, etc. can be appropriately selected and used. The amount of the third component added is a catalytic amount, and specifically, it is in the range of 1 to 2,000 ppm with respect to the first component and the second component.

Next, the hydrophobic silica as the fourth component, which has been surface-treated with organic silicon and has 2% by weight or more of carbon adsorbed on its surface, is a hydrophilic silica obtained by firing silicon tetrachloride or the like. Fumed silica is a silica hydrophobized by heat treatment with dimethylchlorosilane, methyltrichlorosilane, hexamethyldisilazane, etc., where the silanol groups on the surface are trimethylsilyl groups, dimethylsiloxy groups, methylsilyloxy groups and other organosilyl groups. It was blocked,
The manufacturing method is, for example, Japanese Patent Publications No. Sho 49-20739 and No. 41-170.
It is described in No. 49. The amount of carbon adsorbed and immobilized on the surface of silica hydrophobized by these methods is required to be 2% by weight or more based on the total weight of silica in order for the composition of the present invention to have good fluidity. Yes, usually 2-5% by weight
Used. Further, the specific surface area is preferably 50 to 500 m ² / g as measured by the BET method from the viewpoint of the reinforcing property after curing and the fluidity of the composition before curing. Examples of such hydrophobic silica include Aerosil R-812 (manufactured by Degussa, West Germany) and HDK-H2000 (manufactured by Wacker, West Germany).

The amount of the hydrophobic silica added is 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of the first component organopolysiloxane.

If it is less than 5 parts by weight, the strength of the silicone rubber after curing and foaming will be insufficient, and if it exceeds 50 parts by weight, the fluidity of the composition before curing will be poor.

The silanol group-containing organocyclopolycyclosiloxane as the fifth component in the composition of the present invention is It is represented by the structural formula.

Here, R ¹ has 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms.
Of the same or different unsubstituted or substituted monovalent hydrocarbon group of, for example, methyl group, ethyl group, propyl group,
An alkyl group having 1 to 6 carbon atoms such as a butyl group, an phenyl group, an aryl group such as a tolyl group, or a chloromethyl group in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with a halogen atom or the like; Examples include a 3,3,3-trifluoropropyl group, or an alkenyl group such as a vinyl group and an allyl group. Further, m and n are 1 ≦ n ≦ 8 and 0 ≦ m, respectively.
≦ 8 and n + m = an integer represented by 3 to 8, but n + m = 4 because of the ease of synthesis and purification of cyclosiloxane.
~ 6 are preferred.

The silanol group-containing organocyclopolysiloxane is used in an amount of 1 to 80 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the first component organopolysiloxane. If it is less than 1 part by weight, sufficient foaming cannot be obtained, and if it exceeds 80 parts by weight, the addition reaction between the first component and the second component cannot be completed.

The composition of the present invention contains the above-mentioned components as essential components, but further acetylene alcohol or 1,3,5,7-tetramethyl-1,3,5,7 for the purpose of adjusting the foaming and curing reaction. −
Carbon, iron oxide, aluminum hydroxide, benzotriazole and the like can be appropriately added in order to add tetravinylcyclosiloxane or the like as a reaction control agent for the platinum catalyst and to impart flame retardancy.

Further, while preliminarily adjusting the hardness of the silicone rubber foam, while maintaining the object of the present invention, ground quartz, fused quartz,
It is also possible to add magnesium carbonate, magnesium sulfate, calcium carbonate or the like for use.

The composition of the present invention can be widely used for heat insulating materials having excellent cushioning properties and heat insulating properties, cushioning materials, etc., for construction, automobile parts, electric parts, aircraft parts and the like.

<Effects of the Invention> As described in detail above, the composition of the present invention uses the silanol group-containing organocyclopolysiloxane as the fifth component, and therefore has good fluidity before curing, and not only the through holes, It is convenient because it can be easily injected into various small gaps of electric parts and automobile parts, and since the fourth component, hydrophobic silica, acts as a reinforcing agent, the strength of the foam after curing is sufficient, and conventional foaming is possible. It can be easily applied to applications that could not be achieved depending on the hydrophilic silicone rubber composition.

<< Examples >> The present invention will be described in more detail with reference to Examples below, but the present invention is not limited thereto.

Example 1. Dimethylpolysiloxane oil in which both ends of a molecular chain having a viscosity of 10,000 cs are blocked with dimethylvinylsiloxy groups: 100 parts by weight Octyl alcohol modified solution of chloroplatinic acid (platinum amount: 1% by weight): 0.3 parts by weight 1,3,5,7-Tetramethyl-1,3,5,7, -tetravinylcyclotrisiloxane: 0.04 parts by weight Hydrophobic fumed silica R-812 (Degussa, carbon content 3%): 30 parts by weight Parts A base composition was prepared by uniformly mixing the above components using a mixing stirrer.

Next, to 130 parts by weight of the above base composition 25 parts by weight of cyclosiloxane represented by the formula (1) was added and uniformly mixed to obtain a compound I.

The obtained compound flows well and has good fluidity at 25 ° C.
The viscosity at was 1,500 poise.

Example 2. To 130 parts by weight of the base composition obtained in Example 1. Was added to 30 parts by weight of cyclosiloxane represented by and uniformly mixed to obtain a compound II.

The obtained compound had good fluidity and its viscosity at 25 ° C was 1,300 poise.

Example 3 To 130 parts by weight of the base composition obtained in Example 1 Was added to 10 parts by weight of cyclosiloxane represented by and uniformly mixed to obtain a compound III.

The obtained compound had good fluidity, and the viscosity at 25 ° C was 3,000 poise.

Example 4. To 130 parts by weight of the base composition obtained in Example 1. Was added to 15 parts by weight of cyclosiloxane represented by and uniformly mixed to obtain a compound IV.

The obtained compound had good fluidity, and the viscosity at 25 ° C was 2,000 poise.

Comparative Example 1. 130 parts by weight of the base composition obtained in Example 1 Compound V was prepared by adding 15 parts by weight of tetrasiloxane represented by

The composition obtained did not flow at all and had a viscosity at 25 ° C of 30,000
It was a poise.

Comparative Example 2. 100 parts by weight of dimethylpolysiloxane oil in which both ends of a molecular chain having a viscosity of 10,000 cs blocked with dimethylvinylsiloxy groups: 100 parts by weight, octyl alcohol-modified chloroplatinic acid solution (platinum amount: 1% by weight): 0.3 parts by weight Parts, 1,3,5,7, -tetramethyl-1,3,5,7, -tetravinylcyclotrisiloxane: 0.04 parts by weight, quartz powder having an average particle size of 2μ: 30 parts by weight, and 15 parts by weight were mixed uniformly to obtain compound VI.

The obtained compound had good fluidity and the viscosity at 25 ° C was 200 poise.

Comparative Example 3. 100 parts by weight of dimethylpolysiloxane oil in which both ends of a molecular chain having a viscosity of 10,000 cs blocked with dimethylvinylsiloxy groups: 100 parts by weight, octyl alcohol-modified chloroplatinic acid solution (platinum amount: 1% by weight): 0.3 parts by weight Parts, 1,3,5,7 tetramethyl 1,3,5,7 tetravinylcyclotrisiloxane: 0.04 parts by weight, hydrophobic fumed silica R-974 (manufactured by Degussa, carbon content 1%): 30 parts by weight , as well as 15 parts by weight of a cyclosiloxane represented by

The obtained compound did not flow at all, and the viscosity at 25 ° C was 45,000 poise.

Example 5. Compounds (I) to (VII) obtained in Examples 1 to 4 and Comparative Examples 1 to 3 are methyl hydrogen siloxane polymers having both ends of the molecular chain blocked with trimethylsiloxy groups (average degree of polymerization). 40) to compounds I, II and IV ~
12 parts by weight was added to VII, 48 parts by weight was added to compound III, and they were mixed and foam-cured.

In this case, the SiH group / vinyl group ratio of Compounds I, II and IV-VII is 35, and the SiH group / vinyl group ratio of Compound III is
It was 20.

For each cured product, the expansion ratio and tensile strength after curing were measured, and the results shown in Table 1 were obtained.

The results of the above Examples and Comparative Examples demonstrate that the composition of the present invention has good fluidity before curing, but also has sufficient tensile strength after curing.

Claims (2)

[Claims] 1. An organopolysiloxane having a viscosity at 25 ° C. of 100 to 200,000 cs and containing at least two alkenyl groups in one molecule: 100 parts by weight, and a viscosity at 25 ° C. of 1 to 10,000 cs. An organohydrogenpolysiloxane having at least three hydrogen atoms (≡SiH bonds) directly bonded to a silicon atom in the molecule is added to the alkenyl group contained in the above component in an amount of 1 to 1.
Hydrophobic silica whose surface is treated with a catalytic amount of a platinum compound and organic silicon capable of providing 50 times moles of ≡SiH groups, and whose carbon adsorbed on the surface is 2% by weight or more: 5 to 50 parts by weight and a silanol group-containing organocyclopolysiloxane represented by the following structural formula: 1 to 80 parts by weight (Here, R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and m and n are each 1 ≦
n ≦ 8, 0 ≦ m ≦ 8, and 3 ≦ n + m ≦ 8) are contained in the foamable silicone rubber composition. 2. A cured product obtained by curing the foamable silicone rubber composition according to claim 1.