JPH05287205A - Silicone rubber gasket - Google Patents

Abstract

PURPOSE:To provide a silicone rubber gasket which does not stain an adherend such as the sorrounding wall material or post. CONSTITUTION:A silicone rubber gasket is produced by molding and vulcanizing a silicone rubber compsn. comprising an organopolysiloxane represented by the mean compsn. formula: R<1>SiO(4-n)/2 (wherein R<1> denotes the same or different, optionallay substd. monovalent hydrocarbon group; and (n) denotes a positive number of 1.98-2.02), a reinforcing silica powder having a specific surface area of 100m<2>/g or higher, a porous filler having an oil absorption capability of 300cc/100g, and a curative.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber gasket which is excellent in non-staining property to a substrate to be adhered and which is useful as a building gasket or the like.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As building gaskets, those molded with rubber materials such as chloroprene rubber and ethylene-propylene-diene rubber are used.These gasket materials have an increased service life of the building and weather resistance of the gasket material. However, it has become impossible to meet the demand for improvement in creep resistance and the like.

Therefore, in recent years, gaskets made of silicone rubber have been widely used as building gaskets. These silicone rubber gaskets are also used as joint materials for curtain wall construction, joint seals around aluminum sashes, zipper gaskets, etc. As a result, when used for a long period of time, the surrounding concrete, stone plate, glass, etc. became contaminated.

Further, in order to prevent the above-mentioned contamination due to the silicone rubber gasket, the contamination components in the vulcanized molded product of the silicone rubber composition are removed by carrying out post-curing for a long time, and the mobility in the raw material polymer is reduced. Measures such as removing molecular oligomers are taken. But,
Although these stain prevention measures have some effects, they cannot be said to be sufficient, and there is a disadvantage that the cost increases, so that a good improvement measure has been desired.

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 gasket which is excellent in non-staining property to a substrate to be adhered and which is economically favorable.

[0006]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, have found that the organopolysiloxane represented by the following average composition formula (1) and a specific surface area of 100 m ² / g are used. It has been found that a silicone rubber gasket formed of the above-mentioned reinforcing silica powder, a porous filler having an oil absorption capacity of 300 cc / 100 g or more, and a curing agent has excellent properties.

R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1
It is a valent hydrocarbon group, and n is a positive number of 1.98 to 2.02. )

That is, the present inventor has added a porous filler having a high oil absorption ability to the above silicone rubber composition, so that the dirt component contained in the vulcanized molded product is adsorbed by the porous filler. Therefore, the silicone rubber gasket obtained by vulcanizing and molding it has weather resistance,
The present invention has been found to have good creep resistance and excellent non-staining properties, to cause little stain on the surrounding base materials such as wall materials, pillar materials, and glass materials, and to be economically advantageous, and thus the present invention It is what led to.

Therefore, according to the present invention, (A) the organopolysiloxane represented by the above average composition formula (1) (B) a reinforcing silica powder having a specific surface area of 100 m ² / g or more (C) an oil absorption capacity of 300 cc / 100 g Provided is a silicone rubber gasket formed of a vulcanized molded product of a silicone rubber composition containing the above-mentioned porous filler (D) curing agent.

The present invention will be described in more detail below. The organopolysiloxane which is the first essential component of the silicone rubber composition according to the present invention is represented by the following average composition formula (1).

R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted 1
It is a valent hydrocarbon group, and n is a positive number of 1.98 to 2.02. )

In the above formula, R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a cycloalkyl group such as a cyclohexyl group, an alkenyl group such as a vinyl group, an allyl group, a butenyl group or a hexenyl group. Group, a phenyl group, an aryl group such as a tolyl group, or a part or all of the hydrogen atoms bonded to the carbon atoms of these groups are halogen atoms,
Selected from a chloromethyl group substituted with a cyano group, a trifluoropropyl group, a cyanoethyl group and the like, the same or different, preferably having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, unsubstituted or substituted It is a valent hydrocarbon group.
Further, n is a positive number of 1.98 to 2.02.

The organopolysiloxane of the above formula (1) is preferably one whose molecular chain ends are blocked with a trimethylsilyl group, a dimethylphenylsilyl group, a dimethylhydrogensilyl group, a trivinylsilyl group, etc. From the standpoint of preference, it is preferably linear, but it may be one kind or a mixture of two or more kinds having different molecular structures.

Further, the above-mentioned organopolysiloxane has an average degree of polymerization of 100 to 100,000, particularly 5,000 to 2.
The viscosity at 25 ° C. is preferably 100 cs (centistokes) or more, particularly 10
It is preferably from 10,000 to 1,000,000 cs.

This type of organopolysiloxane is usually obtained by cohydrolytically condensing one or more selected organohalogenosilanes, or a cyclic polysiloxane (such as a siloxane trimer or tetramer). It can be obtained by ring-opening polymerization using an alkaline or acidic catalyst.

Next, the reinforcing silica powder, which is the second essential component of the silicone rubber composition, is essential for obtaining a silicone rubber having excellent mechanical strength.
The specific surface area for this purpose 100 m ² / g or more, it is necessary and preferably 150 to 300 m ² / g or more. If the specific surface area is less than 100 m ² / g, the mechanical strength of the cured product will be low.

Examples of such reinforcing silica include fumed silica and precipitated silica.

The reinforcing silica powder is added in the first amount.
It is preferably 10 to 70 parts, especially 30 to 50 parts, relative to 100 parts (parts by weight, hereinafter the same) of the component organopolysiloxane, and if it is less than 10 parts, the addition amount is too small and a sufficient reinforcing effect is obtained. If it exceeds 70 parts, the workability may deteriorate, and the mechanical strength of the obtained gasket may decrease.

Further, the third essential component, the porous filler, is a porous filler having an enhanced oil absorbing ability, and its oil absorbing ability is J
300 cc / when measured according to IS K5101
100 g or more, preferably 500 to 600 cc / 100
Must be g. Oil absorption capacity is 300cc / 10
If the amount is less than 0 g, the non-contaminating property of the silicone rubber gasket, which is the object of the present invention, cannot be sufficiently obtained.

Here, as the porous filler, natural diatomaceous earth, artificial porous silica or the like can be used.
Further, as the artificial porous silica, usual wet silica obtained by decomposing water glass with an acid such as hydrochloric acid or sulfuric acid and then washing with neutralized water is preferably used, for example, Q-805,
Examples thereof include Q-203 (manufactured by Nippon Silica Co., Ltd.), Celite SF (manufactured by John Manville Co.), and zeolite (manufactured by John Manville Co.).

The other characteristics of the porous filler are not particularly limited as long as the oil absorption capacity is in the above range, but the BET specific surface area is 60 to 80 m ² / g and the bulk density is 40 to 60 g / l.
Those within the range are more preferably used.

The amount of the porous filler added is 0.5 to 10 with respect to 100 parts of the first component organopolysiloxane.
Parts, especially 1 to 5 parts are preferable, and if it is less than 0.5 parts, a satisfactory effect may not be obtained, and if it exceeds 10 parts, it may cause a decrease in physical properties. is there.

In the present invention, as the fourth essential component curing agent, a conventionally known one can be used depending on the mechanism of the crosslinking reaction of the silicone rubber composition.

In this case, the end of the molecular chain of the organopolysiloxane of the first component is blocked with a non-hydrolyzable group, and when the crosslinking reaction is carried out by hydrocarbons, the curing agent is an organic compound. Peroxides such as 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-butyl perbenzoate and the like are preferably used. The amount of this organic peroxide added is
0.1 part per 100 parts of the first component organopolysiloxane.
It is preferably 5 to 5 parts, or 0.1 to 1% by weight based on the entire silicone rubber composition.

Hydrolyzable groups such as a hydroxyl group, an alkoxy group, an acetoxy group, an alkenyloxy group, an acyloxy group, an iminoxy group, an amino group, an amide group and an aminooxy group which are bonded to a silicon atom through a crosslinking reaction. When a condensation reaction such as dehydration reaction, dealcoholization reaction, decarboxylic acid reaction, deketone reaction, deoxime reaction, deamine reaction, deamidation reaction, etc. is performed, that is, the molecular chain of the first component organopolysiloxane When the terminal is blocked with, for example, a dimethylalkoxysilyl group having a lower alkoxy group such as a dimethylhydroxysilyl group or a methoxy group, an ethoxy group, a methyldialkoxysilyl group, a trialkoxysilyl group, etc., a curing agent A metal organic acid salt and an organic amine are suitable as the above. Specific examples of metal organic acid salts and organic amines include organic tin compounds such as dibutyltin dilaurate, organic acid salts such as stearic acid and organic titanium compounds such as titanium tetrapropoxide, and amines such as dibutylamine. It In this case, methyltrialkoxysilane, vinyltrialkoxysilane, phenyltrialkoxysilane, tetraalkoxysilane or methyltributanooxime silane, methyltri (hexanoxime) silane, methyltriacetoxysilane, ethyl having an alkoxy group as necessary. A cross-linking agent such as orthosilicate or propyl orthosilicate may be used. The amount of these curing agents added is 0.01 to 0.01% with respect to the silicone rubber compound.
It is preferably 1.0% by weight.

Further, when the organopolysiloxane of the first component has an alkenyl group directly bonded to a silicon atom, an organohydrogenpolysiloxane containing at least two hydrogen atoms directly bonded to the silicon atom in one molecule. Siloxane may be used as a curing agent to be crosslinked and cured by these addition reactions. The organohydrogenpolysiloxane used here is linear,
It may be branched or cyclic, but the degree of polymerization is 3
A diorganopolysiloxane whose end is blocked with a dimethylhydrogensilyl group is preferable,
Copolymer of dimethylsiloxane unit with methylhydrogensiloxane unit and terminal trimethylsiloxane unit, dimethylhydrogensiloxane unit (H (CH
₃ ) a low-viscosity fluid composed of ₂ SiO _0.5 units) and SiO ₂ units, 1,3,5,7-tetrahydrogen-1,3,3
5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1,3
5,7-Tetramethylcyclotetrasiloxane, 1,5
-Dihydrogen-3,7-dihexyl-1,3
Examples include 5,7-tetramethylcyclotetrasiloxane.

The addition amount of the organohydrogenpolysiloxane as the curing agent is such that the hydrogen atom directly bonded to the silicon atom is 50 to 500 mol% with respect to the alkenyl group of the organopolysiloxane of the first component. It is desirable to be used.

It is preferable to add a known platinum-based catalyst to this addition reaction.
Platinum compound, platinum complex, chloroplatinic acid, alcohol compound of chloroplatinic acid, aldehyde compound, ether compound,
Examples thereof include complexes with various olefins. The addition amount of the platinum-based catalyst is preferably in the range of 1 to 2000 ppm as platinum atom with respect to the organopolysiloxane of the first component.

The silicone rubber composition according to the present invention includes
In addition to the above essential components, as an optional component, a filler such as crushed quartz or calcium carbonate may be added as an extender as long as the effect of the present invention is not impaired. Furthermore, an inorganic or organic foaming agent for forming a sponge may be added. Examples of the foaming agent include azobisbutyronitrile, dinitropentamethylenetetramine, benzenesulfone hydrazide, azodicarbonamide, and the like, and the addition amount thereof is preferably in the range of 3 to 10 parts with respect to the silicone rubber compound. By thus adding the foaming agent to the composition of the present invention, a sponge-like silicone rubber gasket can be obtained.

Further, it is optional to add various additives such as a colorant and a heat resistance improver, a reaction control agent, a release agent or a dispersant for a filler to the composition of the present invention, if necessary. However, diphenylsilanediol, various alkoxysilanes, carbon functional silanes, silanol group-containing low-molecular-weight siloxanes, etc., which are used as dispersants for fillers, are added in a minimum amount so as not to impair the effects of the present invention. It is preferable to stop.

In the silicone rubber composition according to the present invention, the above-mentioned components are uniformly mixed using a rubber kneader such as a two-roll, Banbury mixer, dough mixer (kneader), and if necessary heat treatment. It can be obtained by applying. In this case, for example, an organopolysiloxane as the first component, a reinforcing silica powder as the second component, and the like are mixed in advance to prepare a base compound, and a porous filler as the third component and further as a fourth component are prepared with the base compound. Add a curing agent,
You can mix them.

The silicone rubber composition thus obtained is a gasket required by various molding methods such as cast molding, mold pressure molding, extrusion molding, for example, corner gasket, joint seal gasket, zipper gasket. Etc., but these molded products may be post-cured at 100 to 200 ° C. for 30 minutes to 24 hours, if necessary.

[0033]

The silicone rubber gasket of the present invention is
It has excellent weather resistance and creep resistance, excellent non-contamination property, hardly stains the surrounding base materials such as wall materials, column materials, glass plates, etc., and it is also economically favorable. It is useful as

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples] Dimethylsiloxane unit 99.825 mol%, methylvinylsiloxane unit 0.15 mol%, dimethylvinylsiloxane 0.025
100 parts by weight of a rubbery organopolysiloxane having an average degree of polymerization of about 8,000, 3 parts by weight of diphenylsilanediol as a dispersant, 4 parts by weight of a terminal silanol group dimethylpolysiloxane (degree of polymerization n = 10), and 40 parts of fumed silica (manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g was added and heat treated for 2 hours to prepare a base compound.

B for 100 parts of the above base compound
ET specific surface area of 72 m ² / g, oil absorption capacity of 500 cc / 1
00g, porous silica Q-8 having a bulk specific gravity of 52 g / l
05 (manufactured by Nippon Silica Co., Ltd.) was added, and the mixture was sufficiently kneaded with a two-roll mill. Further, 1.5 parts of a 2,4-dichlorobenzoyl peroxide / dimethylpolysiloxane (1,000 cs) = 50/50 paste (hereinafter, curing agent 1) as a curing agent was added thereto, and this composition was 40 mmφ.
With an extruder of U / D = 12, the outer diameter is 20 mm
A tubular gasket having φ and an inner diameter of 16 mmφ was made.

Next, this was continuously vulcanized under atmospheric pressure under vulcanization conditions of 300 ° C./5 minutes and then cut into 1 m lengths, and 200 ° C. /
Post-curing was carried out for 1 hour to obtain a silicone rubber gasket (Example 1).

Also, instead of porous silica, Celite S
F (oil absorption capacity 125 cc / 100 g, BET specific surface area 3.
0 m ² / g, bulk specific gravity 3 g / l, manufactured by John Manville),
A silicone rubber gasket was obtained in the same manner as in Example 1 except that zeolite (oil absorption capacity 170 cc / 100 g, BET specific surface area 3.6 m ² / g, bulk specific gravity 0.5 g / l, manufactured by John Manville) was used. (Example 2,
3).

For comparison, a silicone rubber gasket was obtained in the same manner as in Example 1 without adding porous silica (Comparative Example).

Each of the obtained silicone rubber gaskets was cut into a length of 20 cm, adhered on a white glasal board plate with a screw and fixed to an outdoor exposure device having an inclination of 45 °, and changed with time for half a year. When the degree of stain was visually observed, the results shown in Table 1 were obtained.

[0041]

[Table 1]

From the results shown in Table 1, it was confirmed that the silicone rubber gasket of the present invention (Example) is superior in non-contamination property of the base material and the like as compared with the one without the porous filler (Comparative Example). It was

Claims (1)

[Claims] 1. (A) An organopolysiloxane represented by the following average composition formula (1), R ¹ _n SiO _{(4-n) / 2} (1) (wherein, R ¹ is the same or different from each other). Substitution or substitution 1
It is a valent hydrocarbon group, and n is a positive number of 1.98 to 2.02. ) (B) Vulcanization of a silicone rubber composition containing a reinforcing silica powder having a specific surface area of 100 m ² / g or more, (C) a porous filler having an oil absorption capacity of 300 cc / 100 g or more, and (D) a curing agent. Silicone rubber gasket made of molded products.