JP2643728B2 - Silicone rubber composition and cured product thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition excellent in non-staining property to a substrate to be adhered, and particularly to a non-foamed or foamed silicone rubber cured material useful as a building gasket material, and a cured product thereof. .

[0002]

2. Description of the Related Art
As building gaskets, those molded from rubber materials such as chloroprene rubber and ethylene-propylene-diene rubber are used. In accordance with the demand for increasing the service life of buildings, the weatherability and gas resistance of the gasket materials are increased. Although improvement in properties such as creep properties is required, the gasket material cannot sufficiently meet the demand.

For this reason, in recent years, silicone rubber gaskets have been frequently used as architectural gaskets. However, this silicone rubber gasket is also used as a joint material such as a curtain wall method, a joint seal around an aluminum sash, and a zipper gasket. When used for a long time, such as for example, there is a problem that the adherend base material such as concrete, stone plate, glass, etc. around the gasket becomes dirty.

In recent years, problems such as poor electrical contact due to low molecular weight siloxane generated from the cured silicone rubber, and contamination of the unreacted silicone oil component around the cured silicone rubber due to creep phenomenon have become problems.

[0005] In order to prevent the above-mentioned contamination by the silicone rubber gasket, post-curing is carried out for a long time to remove the contamination portion in the vulcanized molded product of the silicone rubber composition, or to reduce the mobility in the raw material polymer. Soil prevention measures such as removal of molecular weight oligomers are taken.

[0006] However, although these stain prevention measures have a certain effect, they are not satisfactory, and they have disadvantages in that the cost is increased. Therefore, good improvement measures have been desired.

[0007] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a silicone rubber composition which gives a non-foamed or foamed silicone rubber cured product which is excellent in non-staining property to an adherent substrate and which is economically favorable, and a cured product thereof.

[0008]

The present inventors have made intensive studies to achieve the above object, and as a result, (A) an organopolysiloxane represented by the following average composition formula (1):

[0009]

Embedded image (Wherein R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number from 1.98 to 2.02), and extracted with (B) toluene. By adding a silicone powder having a weight change of 0.5% or less at the time, a silicone rubber composition which is excellent in non-staining property to an adherend substrate and which gives an economically favorable cured silicone rubber product can be obtained. Thus, the compositions have been found to be particularly useful as architectural gaskets.

That is, by blending the organopolysiloxane of the formula (1) with a silicone powder whose weight change by extraction with toluene is 0.5% or less, the dirt component contained in the vulcanized molded product is reduced Therefore, a building gasket made of a silicone rubber cured product obtained by curing a silicone rubber composition containing these has excellent weather resistance, good creep resistance, and excellent non-staining properties. The present inventors have found that there is almost no contamination of the adhered base material such as wall material, column material, glass plate, etc., and that the present invention is economically advantageous, and has arrived at the present invention.

In the present invention, the change in the weight of the silicone powder due to the extraction of toluene refers to the silicone powder 1
0 g is immersed in 100 g of toluene at room temperature for 3 days, then filtered and dried.

Hereinafter, the present invention will be described in more detail. The silicone rubber composition of the present invention comprises (A) an organopolysiloxane represented by the above average composition formula (1), and (B) a weight when extracted with toluene. It is composed mainly of silicone powder having a change of 0.5% or less.

In this case, the organopolysiloxane of the component (A) is represented by the following average composition formula (1).

[0014]

Embedded image

Here, R ¹ is the same or different, substituted or unsubstituted monovalent hydrocarbon group, and has 1 to 1 carbon atoms.
10, preferably 1 to 8. Specifically, alkyl groups such as methyl group, ethyl group, propyl group and butyl group, alkenyl groups such as vinyl group, allyl group, butenyl group and hexenyl group, aryl groups such as phenyl group and tolyl group, or these groups A chloromethyl group, a trifluoropropyl group, a cyanoethyl group, or the like, in which a part or all of the hydrogen atoms bonded to the carbon atoms of the above are substituted with a halogen atom, a cyano group, or the like. In addition, n is a positive number of 1.98 to 2.02.

The organopolysiloxane of the above formula (1) is preferably one whose molecular chain end is blocked with a trimethylsilyl group, dimethylphenyl group, dimethylhydroxysilyl group , trivinylsilyl group or the like. The organopolysiloxane may be linear, branched, or cyclic, and may be a mixture of one or more of the same or different molecular structures. In order to obtain a silicone rubber composition having the same, it is preferably linear.

The average degree of polymerization of the organopolysiloxane is 100 to 100,000, especially 5,000 to 20,000.
00 is preferred. Further, the viscosity at 25 ° C. is 100 centistokes (cs) or more, particularly 100,
It is preferably from 000 to 10,000,000 cs.

The organopolysiloxane of the component (A) is
Ring opening of cyclic polysiloxane (siloxane trimer, tetramer, etc.) by co-hydrolytic condensation of one or more selected organohalosilanes, or using an alkaline or acidic catalyst. It can be obtained by polymerization.

The weight change of the silicone powder (B) due to the extraction with toluene is 0.5% or less.
It is preferably at most 1%. This weight change is 0.5
%, The non-staining property of the cured silicone rubber, which is the gist of the present invention, cannot be sufficiently obtained.

Examples of the silicone powder include a silicone powder obtained by co-hydrolyzing a silane having a hydrolyzable group, a gel-like powder obtained by curing a vinyl-containing siloxane in the presence of dimethylhydrogensiloxane and a platinum-based catalyst. Examples include silicone rubber powder obtained by pulverizing a cured silicone rubber, and an emulsion polymer. Each of the silicone powders is washed with a silicone oil-soluble organic solvent such as toluene as necessary, so that the amount of toluene extracted is 0.
It can be 5% or less of silicone rubber powder.

The performance of the silicone powder is not particularly limited as long as the change in weight due to the extraction with toluene is 0.5% or less. Those having a diameter of 30 μm or less are preferably used.

The amount of the silicone powder (B) is 0.5 to 50 parts, preferably 3 to 30 parts, per 100 parts (parts by weight, hereinafter the same) of the organopolysiloxane (A).
It is preferable to use a part. If the amount is less than 0.5 part, sufficient non-staining properties of the cured product may not be obtained, and if it exceeds 50 parts, the processability is deteriorated and the mechanical strength of the cured product is not satisfied. There are cases.

The composition of the present invention preferably contains finely divided silica as the component (C). This fine silica powder is used to impart appropriate hardness and mechanical strength such as tensile strength to the silicone rubber, and has a specific surface area of 5%.
0 m ² / g or more, preferably finely divided silica of 100 to 300 m ² / g is preferably used. Specific examples of such finely powdered silica include fumed silica, calcined silica, precipitated silica, and the like.
More than one species can be used in combination. These silicas may be surface-treated with a chain organopolysiloxane, a cyclic organopolysiloxane, hexamethyldisilazane , dichlorodimethylsilane, or the like.

The compounding amount of such fine powder silica is as follows:
The amount is preferably 5 to 70 parts, more preferably 30 to 50 parts, per 100 parts of the organopolysiloxane of the component (A).
If the amount is less than 5 parts, the reinforcing effect may not be obtained, and if it exceeds 70 parts, the processability may be deteriorated, and the mechanical strength of the obtained cured product may be reduced.

The composition of the present invention may further contain, if necessary, crushed quartz, an extender, as long as the effects of the present invention are not impaired.
A filler such as calcium carbonate can be blended.

Further, the composition of the present invention contains azobisisobutyronitrile, dinitropentamethylenetetramine,
Inorganic or organic blowing agents such as azodicarbonamide and benzenesulfone hydrazide can be added. The amount of the foaming agent is preferably 3 to 10 parts based on 100 parts of the silicone rubber compound. A sponge-like cured product can be obtained by adding a foaming agent to the composition of the present invention to form a cured product. When this is used as a gasket, a sponge-like silicone rubber gasket can be obtained.

If necessary, various additives such as a colorant and a heat resistance improver, a reaction control agent, a release agent, a filler dispersant and the like can be added. It is preferable that the amount of diphenylsilanediol, various alkoxysilanes, carbon functional silane, low molecular weight siloxane containing silanol group, and the like used as the above is limited to a minimum amount so as not to impair the effects of the present invention.

Further, in order to make the silicone rubber composition of the present invention flame-retardant and fire-resistant, a platinum material, a mixture of a platinum compound and titanium dioxide, a mixture of platinum and manganese carbonate, platinum and γ-Fe ₂ Known additives such as a mixture of O ₃ , ferrite, mica, glass fiber, and glass flake can also be added.

The silicone rubber composition of the present invention is prepared by uniformly mixing the above components with a rubber kneading machine such as a two-roll mill, a Banbury mixer or a dough mixer (kneader), and subjecting the mixture to a heat treatment if necessary. Can be obtained by For example, a method in which the organopolysiloxane of the component (A) and the finely divided silica of the component (C) are mixed in advance to prepare a base compound, and the silicone powder of the component (B) is mixed with the base compound may be employed. it can.

As a method for curing the silicone rubber composition of the present invention, it can be cured by any of a method of vulcanization using an organic peroxide as a catalyst and a method of utilizing an addition reaction.

When the molecular chain terminals of the organopolysiloxane (A) are blocked with non-hydrolyzable groups and the crosslinking reaction is carried out between hydrocarbons, a method of vulcanizing with an organic peroxide is used. Can be adopted. The organic peroxide can be used without particular limitation as long as it is generally used for curing a peroxide-curable silicone rubber. Specifically, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-
Methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis (2,5-t-
(Butylperoxy) hexane, di-t-butyl peroxide, t-butylbenzoate, etc., and these can be used alone or in combination of two or more.

The amount of the organic peroxide to be added is 0.5 to 5 parts per 100 parts of the organopolysiloxane of the component (A).
Or 0.1 to 1% by weight of the silicone rubber composition. Curing can be performed by heating at a temperature of 100 to 300 ° C. for about 0.01 to 0.5 hours.

When the organopolysiloxane of the component (A) has an alkenyl group directly bonded to a silicon atom, an organohydrogenpolysiloxane having two or more SiH groups in one molecule is used as a curing agent. The silicone rubber composition can be cured by using and crosslinking by these addition reactions.

The organohydrogenpolysiloxane may be linear, branched or cyclic, but preferably has a degree of polymerization of 300 or less. Specifically, diorganopolysiloxane whose terminal is blocked by a dimethylhydrogensilyl group, a copolymer of a dimethylsiloxane unit with a methylhydrogensiloxane unit and a terminal trimethylsiloxy unit, a dimethylhydrogensiloxane unit (H (CH ₃ ) ₂ SiO _0.5 unit) and SiO ₂
Low-viscosity fluid consisting of units, 1,3,5,7-tetrahydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1, Examples include 3,5,7-tetramethylcyclotetrasiloxane, 1,5-dihydrogen-3,7-dihexyl-1,3,5,7-tetramethylcyclotetrasiloxane, and the like.

The organohydrogenpolysiloxane as the curing agent is such that the hydrogen atom of the SiH group is 50 to the alkenyl group of the organopolysiloxane (A).
It is preferably used in an amount ratio of up to 500 mol%. Curing by the addition reaction can be performed by heating at a temperature of 100 to 300 ° C. for 0.01 to 0.5 hours.

It is preferable to add a known platinum-based catalyst to this addition reaction. Specifically, metal platinum, a platinum compound, a platinum complex, chloroplatinic acid, an alcohol compound of chloroplatinic acid, an aldehyde compound, Examples include ether compounds and complexes with various olefins. The amount of the platinum-based catalyst to be added is preferably 1 to 2,000 ppm as platinum metal based on the organopolysiloxane of the component (A).

The silicone rubber composition of the present invention is formed into a desired shape by architectural gaskets such as corner gaskets, joint seal gaskets, and zipper gaskets by various molding methods such as cast molding, mold pressure molding, and extrusion molding. However, these moldings can be 100-
Post-curing is preferably performed at a temperature of 200 ° C. for 30 minutes to 24 hours.

[0038]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. In each example, the viscosity is a value at 25 ° C.

Example 1, Comparative Example 1 99.825 mol% of dimethyl siloxane unit, 0.15 mol% of methyl vinyl siloxane unit, 0.1 mol% of dimethyl vinyl siloxane unit.
100 parts of a rubbery organopolysiloxane having an average degree of polymerization of 8,000 consisting of 025 mol%, 3 parts of diphenylsilanediol as a dispersant, 4 parts of dimethylpolysiloxane having a terminal silanol group (degree of polymerization n = 10), and a specific surface area of 20 parts
40 parts of silica fine powder Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) of 0 m ² / g was mixed and heat-treated for 2 hours to prepare a base compound.

Next, with respect to 100 parts of the base compound, the change in the weight of toluene extracted was 0.08%, and the silicone powder passed through 60 mesh (K-Shin-Etsu Chemical Co., Ltd.)
E951U rubber sheet was pulverized and washed with toluene (10 parts) and sufficiently kneaded using two rolls.

After kneading, 2,4-dichlorobenzoyl peroxide / dimethylpolysiloxane = 5 as a curing agent
1.5 parts of a 0/50 (viscosity 1,000 cs) paste was added, and this composition was extruded with an extruder of 40 mmφ, U / D = 12 to form a tube having an outer diameter of 20 mm and an inner diameter of 16 mm. After continuous normal-pressure heat vulcanization under the vulcanization conditions of 300 ° C. for 5 minutes, cut into 1 m length,
Post-curing was performed at 0 ° C. for 4 hours to produce a silicone rubber gasket (Example 1).

A silicone rubber gasket was produced in the same manner as in Example 1 except that no silicone powder was added (Comparative Example 1).

Example 2 Using 1.5 parts of dimethylhydrogenpolysiloxane and 0.15 part of a 0.5% chloroplatinate solution in toluene as a crosslinking agent, the viscosity was 800 cs.
After gelling 100 parts of a siloxane oil having vinyl groups at both ends, the mixture was extracted with toluene and pulverized to obtain a gel-like silicone powder (average particle size: 2 μm, change in toluene extraction weight: 0.07).
%).

Example 1 Example 1 was repeated except that this gel silicone powder was used instead of KE951U powder.
A silicone rubber gasket was obtained in the same manner as described above.

Example 3 A siloxane having a viscosity of 600 cs and having a vinyl group at both ends was used, using 1.2 parts of polyethylene glycol octyl phenyl ether as an emulsifier.
An emulsion was prepared by emulsifying a composition containing 1.5 parts of dimethylhydrogenpolysiloxane as a crosslinking agent and 30% of dimethylpolysiloxane having a viscosity of 50 cs and capped at both ends with a trimethylsilyl group to prepare an emulsion. The addition reaction was carried out at room temperature for 16 hours using a curing agent of the formula (1), followed by salting out to obtain a silicone powder (average particle size: 2.4 μm).
The silicone powder was extracted with toluene and dried, and the desired silicone powder (toluene extraction weight change 0.0
5%). A silicone rubber gasket was obtained in the same manner as in Example 1 except that this gel silicone powder was used instead of the KE951U powder.

Comparative Example 2 A silicone rubber emulsion polymer was obtained in the same manner as in Example 3 (average particle size: 2.3 μm).
This silicone powder was washed with toluene and then dried to obtain a silicone rubber emulsion polymerization powder (toluene extraction weight change 0.6%).

Each of the silicone rubber gaskets obtained in Examples and Comparative Examples was cut to a length of 20 cm, and was tightly attached to a white glass plate with screws, and fixed to an outdoor exposure device having a 45 ° inclination. When the degree of contamination due to a change over time for six months was visually observed, the results shown in Table 1 were obtained.

[0048]

[Table 1]

From the results shown in Table 1, it was confirmed that the silicone rubber gaskets of Examples 1 to 3 were more excellent in non-staining properties of the base material and the like than the silicone rubber gaskets of Comparative Examples to which no silicone powder was added.

[0050]

According to the silicone rubber composition of the present invention, the cured product is excellent in weather resistance and creep resistance and is excellent in non-staining properties. It is useful as a building gasket material because it hardly pollutes adherends such as materials, pillars, and glass plates, and has good economic efficiency.

Claims (4)

(57) [Claims] (A) an organopolysiloxane represented by the following average composition formula (1): (In the formula, R ¹ represents the same or different unsubstituted or substituted monovalent hydrocarbon group, and n is a positive number from 1.98 to 2.02.) (B) Weight change upon extraction with toluene Is a silicone rubber composition containing 0.5% or less of silicone powder. 2. The silicone rubber composition according to claim 1, wherein (B) a fine silica powder having a specific surface area of 50 m ² / g or more is blended. 3. The silicone rubber cured product according to claim 1, which is prepared for a foamed silicone rubber by blending a foaming agent. 4. A cured silicone rubber obtained by curing the composition of claim 1, 2, or 3.