JP2853060B2 - Heat resistant rubber composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composite rubber composition of a rubber having a carboxylic acid group and / or a carboxylic ester group having excellent heat resistance and a silicone rubber.

(Prior Art) In general, a synthetic rubber alone has a lower strength than a natural rubber and requires a reinforcing filler such as carbon black or a white filler.

When reinforcing property is particularly required among white fillers, silica filler is indispensable. Most of the silica is hydrophilic due to the silanol groups on the surface, has a large amount of adsorbed water, has poor affinity with rubber, is difficult to disperse in rubber, and the silanol groups on the silica surface are vulcanized. There are problems such as delay.

In general, as a method of improving the dispersibility of silica in rubber and further improving the affinity between rubber and silica, a method of adding a silane compound during use or blending of silica treated with a silane compound is used.

Regarding the use of a silane compound, a silane compound having a functional group having good compatibility with rubber or a silane compound having a functional group which reacts with rubber during vulcanization is used. For example, in a sulfur vulcanization system, a mercapto group-containing silane compound and an amino group-containing silane compound are used, and in a peroxide vulcanization system, a vinyl group-containing silane compound and a methacryloxy group-containing silane compound are used. Epoxy-containing silane compounds are mainly used for the rubber.

However, if the silane coupling agent and rubber have too high reactivity, they react before vulcanization,
May cause problems in use.

In the case of a rubber having a carboxylic acid and / or carboxylic acid ester group, a methacryloxy group-containing silane compound or an epoxy group-containing silane compound having a similar chemical structure is used to improve the compatibility of silica, but the heat resistance is improved. That is not enough.

Amino group-containing silane compounds have high reactivity with carboxylic acids or carboxylic acid esters, and are considered to be effective for improving strength. The hydrolysis reaction of the contained silane compound occurs, and the rubber and the hydrolysis reaction product undergo a cross-linking reaction, so that the rubber cannot be used as a rubber.

(Problems to be Solved by the Invention) The present invention has been made in view of the technical problems of the prior art, and a specific silica is used for a composite of a rubber having a carboxylic acid group and / or a carboxylic ester group and a silicone rubber. An object of the present invention is to obtain a rubber composition having extremely excellent heat resistance by compounding the same.

(Means for Solving the Problems) The present invention relates to (B) based on 100 parts by weight of a mixture of (A) a rubber having a carboxylic acid group and / or a carboxylic acid ester group (hereinafter referred to as an acrylic rubber) and a silicone rubber. An object of the present invention is to provide a rubber composition comprising 5-200 parts by weight of silica previously treated with an amino group-containing organosilane compound.

The mixture of acrylic rubber and silicone rubber used in the present invention is composed of 97 to 30% by weight of acrylic rubber and 3 to 70% by weight of silicone rubber (the total of acrylic rubber and silicone rubber is 100% by weight). It is a mixture.

In order to prevent the phase separation between the acrylic rubber and the silicone rubber of the mixture and improve the processability, the silicone rubber has an average particle size of 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less in the acrylic rubber. Those having a network polymer are preferred.

The toluene-insoluble content of the reticulated silicone rubber is at least 30% by weight, preferably at least 50% by weight of the silicone rubber.

A mixture of an acrylic rubber and a silicone rubber containing a reticulated silicone rubber is obtained by graft-polymerizing a radical polymerizable monomer used for the acrylic rubber described below to a silicone rubber emulsion. Is obtained by crosslinking and curing the silicone rubber while applying shear deformation to the silicone rubber.

As a method for crosslinking and curing the silicone rubber, known methods can be used, and examples thereof include peroxide crosslinking, addition reaction crosslinking, and condensation reaction crosslinking.

Acrylic rubber used in the case of reacting and mixing acrylic rubber and silicone rubber while giving shear deformation includes acrylic rubber, ethylene acrylic rubber, ethylene / vinyl acetate / acrylate copolymer, carboxylated nitrile rubber, Butadiene-acrylonitrile-
(Meth) acrylate copolymer, butadiene-
(Meth) acrylic acid ester copolymers, carboxylated styrene-butadiene copolymers, and hydrides thereof are exemplified.

Of these, acrylic rubber, ethylene acrylic rubber, and ethylene / vinyl acetate / acrylate copolymer are particularly preferred, and acrylic rubber is particularly preferred in terms of heat resistance and oil resistance.

Acrylic rubber is a polymer of a (meth) acrylic acid alkyl ester, or the alkyl ester as a main component,
There can be mentioned a copolymer obtained by copolymerizing a component having a crosslinking group described below.

Among them, the alkyl esters of (meth) acrylic acid include ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, methoxyethyl (meth) acrylate, and ethoxyethyl (meth) acrylate. And one or more of these.

Also, acrylonitrile,
One or more monomers such as styrene, 1,3-butadiene, isoprene, isobutylene, chloroprene, ethylene, propylene, vinyl acetate and acrylic acid
It is also possible to use them together in an amount of not more than about% by weight.

Here, as a crosslinking group component of the acrylic rubber, vinyl chloroacetate, allyl chloroacetate, 2-chloroethyl vinyl ether, allyl glycidyl ether,
Glycidyl methacrylate, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, 5-ethylidene-2-norbornene, dicyclopentadiene, vinyl acrylate, allyl methacrylate, sidiclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, P -Vinylphenyl (dimethyl) vinylsilane, 3-methacryloxypropyldimethylvinylsilane, and the like.

The crosslinking group component used in these acrylic rubbers is
15% by weight or less of the alkyl (meth) acrylate,
It is preferably used in an amount of 10% by weight or less, more preferably in the range of about 0.01 to 5% by weight.

Further, the acrylic rubber preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10 to 200, preferably 20 to 150, more preferably 30 to 100, from the viewpoint of kneading workability. A rubber composition having stable quality and characteristics can be obtained by using a rubber composition having a high viscosity. If the Mooney viscosity is out of the above range, kneading workability and dispersibility will be poor, and it will be difficult to maintain quality characteristics such as mechanical strength and heat resistance.

As the silica filler in the component (B) of the present invention, all known silica fillers can be used, and for example, dry silica and wet silica are suitably used. These may be untreated or previously treated with a compound other than the amino group-containing organosilane. As the amino group-containing organosilane compound, specifically, The one represented by the formula (1) is used.

Among those having the structure represented by the general formula (IV), those having two or more active amino groups include, for example, the following.

The amount of the amino group-containing organosilane compound is silica 100
The range is 0.1 to 30 parts by weight, preferably 0.5 to 20 parts by weight, more preferably 1.0 to 15 parts by weight based on parts by weight. 0.1
If the amount is less than 30 parts by weight, the desired heat resistance will not be exhibited, while if it exceeds 30 parts by weight, the mechanical strength will decrease.

The treatment of the silica with the amino group-containing organosilane compound can be performed by a means known per se.

That is, a method in which a silica-based filler and a silane compound are reacted in a processing chamber consisting of an upright tubular furnace by a co-current method in which a silica-based filler and a silane compound are continuously advanced, as disclosed in JP-B-41-17049.
Alternatively, a method of contacting a silica-based filler with a silane compound at a relatively low temperature, followed by a high-temperature treatment and a drying treatment with an inert gas, as disclosed in JP-B-60-6379, may be used.

The rubber composition according to the present invention is a rubber (B) pretreated with an amino group-containing organosilane compound in an amount of 5 to 200 parts by weight, preferably 8 parts by weight, based on 100 parts by weight of the carboxylic acid group and / or carboxylic ester group-containing rubber (A). -150 parts by weight, more preferably 10-100 parts by weight.

If the treated silica (B) is too small or too large, the desired strength cannot be obtained and it is not practical.

The composition of the present invention essentially comprises the components (A) and (B), but in addition, NR, IR, SBR, BR, EP (D) M, and ECO
% By weight or less may be included.

Examples of the reinforcing filler and extender include fumed silica, wet silica and surface-treated or untreated calcium silicate, quartz fine powder, diatomaceous earth, carbon black, zinc white, basic magnesium carbonate, activated calcium carbonate A mixture of magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate, asbestos, glass fibers, organic reinforcing agents, and organic fillers can be added.

Further, as processing aids, fatty acid esters, fatty acid amides, and as plasticizers, for example, phthalic acid derivatives, adipic acid derivatives, sebacic acid derivatives, maleic acid derivatives, trimellitic acid derivatives, phosphoric acid derivatives, glycol derivatives,
Examples of softeners include lubricating oils, process oils, vegetable oils, and sub-aging agents such as diphenylamines, phenylenediamines, phosphates, quinolines, cresols, phenols, dithiocarbamate metal salts, and other colorants. , An ultraviolet absorber, a flame retardant, an oil resistance improver, a foaming agent, an anti-scorch agent, a tackifier, a lubricant, a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerator, and the like.

These compounded rubber compositions are subjected to molding and vulcanization after adding a cross-linking agent by a usual kneader such as a roll or a Banbury mixer.

Crosslinking is performed by applying energy such as heat, an electron beam, ultraviolet light, or electromagnetic waves.

The crosslinking agent may be sulfur or a derivative thereof used as a rubber crosslinking agent, or any of organic peroxides, alkylphenol resins, and ammonium benzoate. Further, the crosslinking group contained in the rubber (A) may be used. A polyfunctional cross-linking agent having two or more functional groups having a reactivity with is used.

Examples of the organic peroxide used as a crosslinking agent include 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (t- Butylperoxy) hexane, 2,2'-bis (t-butylperoxy) -P-diisopropylbenzene, dicumyl peroxide, di-t-butyl peroxide, t-butyl perbenzoate, 1,1-bis ( t-butyl peroxy)
-3,3,5-trimethylcyclohexane, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide,
P-chlorobenzoyl peroxide, azobisisobutyronitrile and the like, preferably 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,2,5-
Dimethyl-2,5-di (t-butylperoxy) hexane and 2,2'-bis (t-butylperoxy) -P-diisopropylbenzene.

The polyfunctional crosslinking agent having two or more functional groups reactive with the crosslinking group present in the rubber (A) is preferably an amino group, an isocyanate group, a maleimide group, an epoxy group, a hydroxyl group, At least one selected from the group consisting of a mercapto group and a carboxyl group
A polyfunctional crosslinking agent having two or more kinds of functional groups, such as diamines, polyamines, diisocyanates, dithiols, polyisocyanates, maleimides, diepoxides, diols, polyols, bisphenols, Compounds such as dicarboxylic acids can be mentioned.

Specific examples of these compounds include, for example, N, N'-phenylenedimaleimide, hexamethylenediamine, 2,2
-Bis (4'-hydroxyphenyl) propane, 2,2-
Bis (4'-hydroxyphenyl) hexafluoropropane, triazinetrithiol and the like can be mentioned.

Furthermore, when an elastomer into which an epoxy group is introduced is used as the rubber (A), polyamine carbamates, ammonium organic carboxylate, dithiocarbamate, or alkali metal organic carboxylate can be used.

Further, when an elastomer having a halogen group introduced into the rubber (A) is used, polyamine carbamates,
An ammonium salt of an organic carboxylic acid, an alkali metal salt of an organic carboxylic acid, or a triazine compound can also be used.

In the case of sulfur, the amount of the crosslinking agent added is the rubber composition of the present invention.
0.1 to 5 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight
3 parts by weight, and in the case of the organic peroxide, the addition amount thereof is 0.01 to 10 parts by weight with respect to 100 parts by weight of the rubber composition.
It is preferably 0.1 to 5 parts by weight, and in the case of a polyfunctional crosslinking agent, 0.0 to 5 parts by weight based on 100 parts by weight of the rubber composition of the present invention.
It is 1 to 10 parts by weight, preferably 0.1 to 5 parts by weight.

If the amount of the crosslinking agent is too small, the crosslinking density of the rubber component is low, and the mechanical strength, oil resistance, and creep resistance are insufficient. The elongation of the vulcanizate of the rubber composition decreases.

At the time of peroxide crosslinking, a bifunctional vinyl monomer or the like may be used as a crosslinking aid.

Examples of such a crosslinking aid include the following compounds. That is, ethylene glycol dimethacrylate, 1,3
-Butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 2,2 '-Bis (4-methacryloyldiethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, divinylbenzene, N, N'-methylenebisacrylamide, P-quinonedioxime, P , P'-dibenzoylquinone dioxime, triazinedithiol, triallyl cyanurate, triallyl isocyanurate, bismaleimide and the like.

In order to cross-link (vulcanize) the rubber composition, usually 80 to
Perform primary vulcanization at 200 ° C for several minutes to 3 hours under a pressure of 20 to 200 kg / cm ² , and if necessary at 80 to 200 ° C for 1 to 48
Time, secondary vulcanization to make rubber products. The rubber elastic body crosslinked (vulcanized) in this way has excellent mechanical strength and excellent heat resistance, and can be used in general industries and chemical fields.

(Example) Next, the present invention will be described in detail with reference to examples.

The initial physical properties and the aging test were evaluated under the conditions shown in each table in accordance with JIS K6301.

Reference Example 1 Nippon Silica Co., Ltd. Wet Silica Nip Seal VN3 10
0 parts by weight of silane compound: T by Toshiba Silicone Co., Ltd.
Using 5 parts by weight of SL8331 (3-aminopropyltriethoxysilane), a treated silica was obtained by the method disclosed in JP-B-41-17049.

Reference Example 2 TSL8340 manufactured by Toshiba Silicone Co., Ltd. as a silane compound
A treated silica was obtained in the same manner as in Reference Example 1, except that 5 parts by weight of (N- (2-aminoethyl) -3-aminopropyltrimethoxysilane) was used.

Reference Example 3 A treated silica was obtained in the same manner as in Reference Example 1 except that surface-treated dry silica Aerosil R972 manufactured by Nippon Aerosil Co., Ltd. was used.

Reference Example 4 TSL8380 manufactured by Toshiba Silicone Co., Ltd. as a silane compound
(3-mercaptopropyltrimethoxysilane) 5 parts by weight, Nipsil VN3 manufactured by Nippon Silica Co., Ltd. as silica
A treated silica was obtained in the same manner as in Reference Example 1 using 100 parts by weight.

Reference Example 5 TSL8350 of Toshiba Silicone Co., Ltd. as a silane compound
A treated silica was obtained in the same manner as in Reference Example 1 except that 10 parts by weight of (3-glycidoxypropyltrimethoxysilane) was used.

Reference Example 6 TSL8370 manufactured by Toshiba Silicone Co., Ltd. as a silane compound
(3-methacryloxypropyltrimethoxysilane) 15
Except for using parts by weight, treated silica was obtained in the same manner as in Reference Example 3.

Example 1 A mixture of the acrylic rubber and the silicone rubber as the component (A) was prepared by the following procedure.

First, 0.1 mol% of organic groups bonded to silicon atoms are vinyl groups, the remainder is methyl groups, and the average degree of polymerization is 6.00.
0 parts by weight of 100 parts by weight of linear polymethylvinylsiloxane and 35 parts by weight of fine powdered silica whose surface has been treated with polydimethylsiloxane and hydrophobized until uniform with a kneader to obtain a silicone rubber composition (a-1). ) Got.

AR10 made by Nippon Synthetic Rubber Co., Ltd. as an acrylic rubber
1) using the composition (a-1) as a silicone rubber,
In addition, as a polyorganohydrogensiloxane as a crosslinker for shear deformation cross-linking and curing of silicone rubber, a linear polymethylhydrogensiloxane whose terminal is blocked with a trimethylsilyl group and composed of 20 methylhydrogensiloxane units is used. Was. Acrylic rubber, silicone rubber composition (a-1) and polymethyl hydrogen siloxane are sequentially charged into a rubber mixer (heated to 60 to 80 ° C. and set to 60 rpm), kneaded, and uniformly mixed according to the following formulation. At this point, chloroplatinic acid 1
An isopropanol solution containing a% by weight was added, and the mixture was further kneaded. After being homogenized again, the mixture was discharged. The temperature of the rubber mixture A at the time of discharge was 150 to 200 ° C.

Next, the rubber mixture A is again put into a rubber mixer (60 to 80 ° C).
And set to 60 rpm), and as shown in Table 1, as the component (B) silica, the silica of Reference Example 1 and
Components other than the cross-linking agent, such as processing aids, were added and kneaded. After the mixture became uniform, it was discharged. Rubber temperature at discharge is 120 ~ 200
° C.

Next, the discharged rubber was wound around two rolls and kneaded by adding the vulcanizing agent shown in Table 1 and then press vulcanized (press vulcanization at 100 to 160 kg / cm ^{2 at} 170 ° C. for 20 minutes). One more
Secondary vulcanization was carried out in a gear oven at 75 ° C. for 4 hours and evaluated for physical properties. The results are shown in Table 2.

Example 2 0.2 mol% of organic groups bonded to silicon atoms are vinyl groups, the remainder is methyl groups, and the average degree of polymerization is 100 parts by weight of linear polymethylvinylsiloxane having an average degree of polymerization of 6.000. Treated and hydrophobized fine powder silica 30
The silicone rubber composition (a-2) was obtained by blending the parts by weight with a kneader until uniform.

Nippon Mektron Co., Ltd. PA 40 as an acrylic rubber
4. The composition (a-2) prepared above was used as the silicone rubber, and the same polyorganohydrogensiloxane as used in Example 1 was used.

Acrylic rubber, silicone rubber composition (a-2) and polymethyl hydrogen siloxane are sequentially charged into a rubber mixer (heated to 60 to 80 ° C. and set to 60 rpm), kneaded, and uniformly mixed in the above formulation. At that point,
An isopropanol solution containing 1% by weight of chloroplatinic acid was added, and the mixture was further kneaded. After being homogenized again, it was discharged.
The temperature of the silicone rubber mixture B at the time of discharge was 150 to 200 ° C.

Next, the rubber mixture B was again charged into a rubber mixer (heated to 60 to 80 ° C. and set to 60 rpm), and as shown in Table 1, as the component (B) silica, the silica of Reference Example 2 and the processing aid Components other than the cross-linking agent, such as an agent, were added and kneaded. After the mixture became homogeneous, the mixture was discharged. Rubber temperature at discharge is 120 ~ 200 ℃
Met.

Next, the discharged rubber was wound around two rolls, and the mixture was kneaded with the vulcanization aid shown in Table 1 and subjected to press vulcanization (press vulcanization at 100 to 160 kg / cm ^{2 at} 170 ° C. for 20 minutes). Further, secondary vulcanization was performed at 175 ° C. for 4 hours with a gear open for evaluation of physical properties. The results are shown in Table 2.

Example 3 Using the silicone rubber composition (a-2) of Example 2,
Rubber mixture C was obtained in the same manner as in Example 2 using VAMAC-G manufactured by DuPont as an acrylic rubber.

Next, the rubber mixture C was again charged into a rubber mixer (heated to 60 to 80 ° C. and set to 60 rpm), and as shown in Table 1, as the component (B) silica, the silica of Reference Example 3 and the processing aid Components other than the cross-linking agent were added and kneaded, and the mixture was discharged after being made uniform.

Next, the discharged rubber was wound around two rolls and kneaded by adding the vulcanizing agent shown in Table 1 and then press vulcanized (press vulcanization at 100 to 160 kg / cm ^{2 at} 170 ° C. for 20 minutes). Further, secondary vulcanization was performed at 175 ° C. for 4 hours with a gear open for evaluation of physical properties.

 The results are shown in Table 2.

Example 4 Silica of Reference Example 3 was added to 100 parts by weight of rubber mixture B
A rubber composition was obtained in the same manner as in Example 2 except that 0 part by weight was blended. Further, the rubber was evaluated in the same manner as in Example 2, and the results are shown in Table 2.

Comparative Example 1 A rubber was evaluated in the same manner as in Example 1 except that the silica of Reference Example 4 was used, and the results are shown in Table 2.

Comparative Example 2 Rubber was evaluated in the same manner as in Example 2 except that the silica of Reference Example 5 was used, and the results are shown in Table 2.

Comparative Example 3 Rubber was evaluated in the same manner as in Example 3 except that the silica of Reference Example 4 was used, and the results are shown in Table 2.

Comparative Example 4 A rubber was evaluated in the same manner as in Example 4 except that the silica of Reference Example 6 was used, and the results are shown in Table 2.

Comparative Example 5 As shown in Table 1, a wet silica nip seal VN3 manufactured by Nippon Silica Co., Ltd., and TSL 8331 manufactured by Toshiba Silicone Co., Ltd. as an amino group-containing silane compound were added to the rubber mixture A obtained in Example 1 as shown in Table 1. (3-Aminopropyltriethoxysilane) and a component other than a crosslinking agent such as a processing aid were added, and an attempt was made to prepare a rubber composition by the same process as in Example 1. However, the rubber composition was powdered and could not be aggregated for evaluation. could not.

(Effect of the Invention) The heat-resistant rubber composition of the present invention can be used for transportation equipment such as automobiles, ships, aircrafts, etc., rubber parts used for general industrial articles such as foods, electric appliances, electronics, OA, and building materials, for example, various packings, O- Acrylic rubber and silicone rubber such as rings, oil seals, bearing seals, gaskets, belts, hoses, boots, anti-vibration rubbers, tubes, diaphragms, and rolls can be widely applied to fields where they are conventionally used.

Thus, the heat-resistant rubber composition of the present invention has an extremely large industrial value.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI (C08L 83/04 13:00) (72) Inventor Hironori Matsumoto 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. ( 72) Inventor Hirofumi Yoshida 6-31, Roppongi, Minato-ku, Tokyo Toshiba Silicone Co., Ltd. (72) Inventor Makoto Matsumoto 6-31, Roppongi, Minato-ku, Tokyo Toshiba Silicone Co., Ltd. (72) Inventor Junichiro Watanabe 6-2-31 Roppongi, Minato-ku, Tokyo Toshiba Silicone Co., Ltd. (56) References JP-A-57-195757 (JP, A) JP-A-61-103951 (JP, A) JP-A-49-49 34948 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 7/00-21 / 02,83 / 04-83/08 C09K 3 / 36,9 / 06

Claims (1)

(57) [Claims] 1. Silica pretreated with (B) an amino group-containing organosilane compound per 100 parts by weight of a mixture of (A) a rubber having a carboxylic acid group and / or a carboxylic ester group and a silicone rubber. A rubber composition comprising parts by weight.