JP2002284940A - Rubber vulcanized molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synthetic rubber composition which has a low out gas content, improved dumping characteristics and improved stickiness almost never deteriorating the performances of conventional synthetic rubbers. SOLUTION: This rubber vulcanized molded article obtained by molding and vulcanizing a composition comprising 100 pts.wt. of a rubber comprising 100 to 40 wt.% of an ethylene-alkyl acrylate copolymer and 0 to 60 wt.% of a fluorine rubber, 0.5 to 10 pts.wt. of an organic peroxide and 0.5 to 10 pts.wt. of a polyfunctional monomer is characterized by containing an out gas in an amount of <=20 μg per g of the vulcanized molded article and having surface friction coefficient of 0.1 to 2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vulcanized rubber molded product. More specifically, the present invention relates to a rubber vulcanized molded product having excellent damping properties and non-staining properties (low outgassing properties).

[0002]

2. Description of the Related Art As a conventional stopper material, fluorine rubber is widely used due to its damping property and low outgassing property. Rubber materials other than fluororubber have problems such as generation of low molecular volatile components from rubber (outgassing) and contamination of disks. As a head impact absorbing material for HDD (hard disk), fluoro rubber has excellent low rebound resilience and is excellent. However, its damping characteristics are highly temperature-dependent, and due to the recent expansion of the operating temperature range due to multifunctionality such as higher performance, miniaturization, and weight reduction, the problem that fluoro rubber has insufficient damping characteristics is being raised. . In addition, malfunctions due to adhesion of rubber may cause a problem. Conventionally, surface treatment is used, but the cost is high.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vulcanized synthetic rubber molded article which has low outgassing and improved damping properties and tackiness without substantially impairing the performance of the conventional synthetic rubber. It is in.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
0.5 to 10 parts by weight of an organic peroxide per 100 parts by weight of a rubber composed of 100 to 40% by weight of an ethylene-alkyl acrylate copolymer rubber and 0 to 60% by weight of a fluororubber and a polyfunctional monomer
A vulcanized molded product obtained by vulcanization molding from a composition containing 0.5 to 10 parts by weight, and the amount of outgas per 1 g of the vulcanized molded product is 20 μg.
This is achieved by a rubber vulcanizate having the following and a surface friction coefficient of 0.1 to 2.5.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the ethylene-alkyl acrylate copolymer rubber, commercially available products, for example, those of Boeing series of Mitsui-Dupont polychemical products can be used as they are. It can be used by blending with fluororubber at a blend ratio of 60% by weight or less, preferably 40% by weight or less. When blended at a higher ratio, the temperature dependence of the damping characteristics of the obtained vulcanized molded product increases.

As the fluorine rubber, vinylidene fluoride /
Propylene hexafluoride, ethylene tetrafluoride / propylene
Binary copolymer, vinylidene fluoride / 6 hexafluoropropylene /
Tertiary copolymers such as tetrafluoroethylene, vinylidene fluoride / 4 ethylene tetrafluoride / perfluoro (alkyl vinyl ether) and the like are used. Of these, peroxide-crosslinked type fluororubber is preferred. Some of them are commercially available, and for example, Viton manufactured by Dupont Dow Elastomer Co. can be used as it is.

The ethylene-alkyl acrylate copolymer rubber or the blend rubber thereof and the fluororubber are used in an amount of 0.5 to 10 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the rubber.
5 parts by weight of an organic peroxide and 0.5 to 10 parts by weight, preferably 1 to 8 parts by weight of a polyfunctional monomer are used in combination. Outside these ranges, the vulcanization molding itself is not performed.

The organic peroxide can be used without any particular limitation as long as it can be generally used. For example, tertiary butyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, 1,1-dioxide (Tert-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-
2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3,1,3-di (tert-butylperoxyisopropyl) benzene , 2,5-
Dimethyl-2,5-di (benzoylperoxy) hexane,
Tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, n-butyl-4,4-di (tertiary butyl peroxy) valerate and the like can be mentioned.

As the polyfunctional monomer, any generally usable one can be used without any particular limitation. Examples thereof include triallyl isocyanurate, triallyl cyanurate, trimethylallyl isocyanurate, ethylene glycol dimethacrylate, and trimethylolpropane. Trimethacrylate, N, N'-m-phenylenedimaleimide and the like. If the amount of the organic peroxide or the polyfunctional monomer is less than 0.5 parts by weight, a sufficient crosslink density cannot be obtained, and if the amount of the organic peroxide or the polyfunctional monomer is 10 parts by weight or more, vulcanization by foaming. A product cannot be obtained, or even if it is obtained, rubber elasticity and elongation decrease.

In the composition containing the above components as essential components, the major axis is 10 to 300 μm, preferably 30 to 200 μm,
And the aspect ratio is 5 or more, preferably 8 or more filler, 5 to 100 parts by weight per 100 parts by weight of rubber, preferably 20 to 8 parts
It is preferable to add 0 parts by weight, in which case irregularities are formed without performing surface treatment of the vulcanized molded product, and a vulcanized molded product excellent in non-adhesiveness can be obtained.

As such a filler, for example, magnesium silicate, calcium silicate, calcium metasilicate, carbon fiber, glass fiber and the like are used. In addition, when the major axis (average particle diameter in the case of a granular body) is larger than 300 μm,
The strength of the vulcanized molded product decreases. On the other hand, when the aspect ratio is 5
If the amount is less than or equal to or less than 5 parts by weight, unevenness cannot be formed on the surface of the vulcanized molded product, and the effect of improving adhesiveness cannot be expected. On the other hand, when the amount of the filler is 100 parts by weight or more, kneading becomes difficult, the hardness of the vulcanized molded product increases, and the strength decreases.

In addition to the above components, rubber compounding agents include reinforcing agents such as carbon black, processing aids such as stearic acid, palmitic acid, and paraffin wax; acid acceptors such as zinc oxide and magnesium oxide; A compounding agent generally used in the rubber industry, such as an agent, is used by being appropriately added as necessary.

The preparation of the rubber composition comprises the steps of intermixing,
Kneading is performed by kneading using a closed kneader such as a kneader or a Banbury mixer or an open roll, and vulcanization is generally performed at 150 to 200 ° C. using an injection molding machine, a compression molding machine, a vulcanizing press, or the like. By heating for about 3 to 60 minutes, and then at about 190 to 250 ° C for 1 to 24
Time heat treatment (secondary vulcanization) is performed.

In order to reduce the outgassing of the rubber vulcanizate of the present invention, heat treatment, decompression treatment, extraction treatment and the like can be performed alone or in combination. It is 1-2 at 190-250 ℃
About 4 hours is preferable.

In order to reduce the coefficient of friction, surface hardening by heat treatment, reduction effect by chemical treatment, coating, etc. can be performed alone or in combination. However, heat treatment is the most efficient economically. The same degree as the outgas reduction is preferable. However, the method is not necessarily limited to these methods as long as the outgassing and the surface friction coefficient fall within predetermined ranges.

The vulcanized molded product obtained by vulcanization molding in this manner has an outgas amount per gram of 20 μg or less,
Preferably 10 μg or less, and the surface friction coefficient is 0.1 to
It has a value of 2.5, preferably 0.1 to 2.0.

【The invention's effect】

The vulcanized molded article according to the present invention exhibits a low out property while maintaining the performance of a conventional synthetic rubber, and has improved damping properties and tackiness. It is suitably used as a shock absorbing stopper component for a storage device head, a printer head, etc., for a disk device for a vehicle, a disk device for a camera-integrated video recorder, etc., using a non-polluting (low outgassing) property of the stopper component. This is effective for preventing adhesion between the head and the head.

[0018]

Next, the present invention will be described with reference to examples.

Example 1 Ethylene-alkyl acrylate copolymer rubber (Bermac D) 100 parts by weight Carbon black (N990) 100 {Dicumyl peroxide 4} N, N'-m-phenylenedimaleimide 1 , Kneading with an open roll. The molding of this rubber composition is performed by a vulcanizing press.
Primary vulcanization at 0 ° C for 30 minutes and heating oven for 200
Heat treatment was performed at 24 ° C. for 24 hours to obtain a vulcanized sheet having a size of 150 × 150 × 2 mm and a cylindrical test piece having a diameter of 29 mm and a height of 12.5 mm.

Example 2 In Example 1, the following formulation was used: Ethylene-alkyl acrylate copolymer rubber (Bomac D) 70 parts by weight Fluoro rubber (Viton GBL-200 made by DuPont Dow elastomer) 30 カ ー ボ ン Carbon black (N990) 70 〃 2,5-dimethyl-2,5-di (No. 3 Butylperoxy) hexane 3 ト リ Triallyl isocyanurate 2 〃

Comparative Example 1 In Example 1, the heat treatment was changed to 170 ° C. for 24 hours.

Comparative Example 2 In Example 1, the heat treatment was changed to 270 ° C. for 24 hours.

Comparative Example 3 In Example 2, the ethylene-alkyl acrylate copolymer rubber was not used, and the fluororubber was changed to 100 parts by weight. In addition, the amount of carbon black was changed to 15 parts by weight for hardness adjustment.

Comparative Example 4 In Example 2, 30 parts by weight of ethylene-alkyl acryl copolymer rubber and 70 parts by weight of fluoro rubber were used, respectively. In order to adjust the hardness, the amount of carbon black was changed to 50 parts by weight.

Comparative Example 5 In Example 1, dicumyl peroxide was used in an amount changed to 0.3 part by weight, but the crosslink density did not increase and vulcanization molding was not possible.

Comparative Example 6 In Example 1, N, N'-m-phenylenedimaleimide was used in an amount changed to 0.3 part by weight, but the crosslink density did not increase, and vulcanization molding was not possible.

Comparative Example 7 In Example 1, dicumyl peroxide was used in an amount changed to 15 parts by weight, but foaming occurred during vulcanization molding, and vulcanization molding was not possible.

Comparative Example 8 In Example 1, N, N′-m-phenylenedimaleimide was used in the amount changed to 15 parts by weight, but foaming occurred during vulcanization molding, and vulcanization molding could not be performed.

With respect to each vulcanized sheet obtained in each of the above Examples and Comparative Examples, physical properties in a normal state were measured in accordance with JIS K-6253 and JIS K-6251.
The rebound resilience at 20, 25 and 70 ° C was measured. Further, the surface roughness was measured as a substitute property of the adhesive property (a reduction in the contact area with the counterpart material was aimed at). In addition, the amount of outgas due to heat extraction at 120 ° C for 5 hours (GC by headspace method)
-MS measurement). Further, the friction coefficient was measured with a HEIDON surface property tester (load: 25 gf). The results obtained are shown in Table 1. Table 1 Example Comparative Example Measurement Items 1 2 1 2 3 4 Normal Properties Hardness (Durometer A) 75 78 73 78 75 82 Tensile Strength (MPa) 9.4 10.1 9.2 4.2 22.2 13.3 Elongation (%) 250 260 280 140 250 250 Rebound resilience (%) -20 ° C 18 27 20 29 42 34 25 ° C 21 15 23 24 7 10 70 ° C 26 32 29 32 65 50 Surface roughness Ra value 0.3 0.3 0.3 0.3 0.2 0.3 Outgas amount (μg / g) 2 1 60 1 2 3 Coefficient of friction 2.5 2.4 4.0 1.2 2.9 2.8

Example 3 Ethylene-alkyl acrylate copolymer rubber (Bomac D) 100 parts by weight Carbon black (N990) 50 50 Carbon fiber (major axis 100 μm, aspect ratio 10) 50〃 Dicumyl peroxide 4〃 N, N'- m-Phenylene dimaleimide 1 These compositions were kneaded with a kneader and an open roll. The molding of this rubber composition is performed by a vulcanizing press.
Primary vulcanization at 0 ° C for 30 minutes, and heating oven 220
Heat treatment was performed at 150 ° C. for 15 hours to obtain a vulcanized sheet having a size of 150 × 150 × 2 mm and a cylindrical test piece having a diameter of 29 mm and a height of 12.5 mm.

Comparative Example 9 In Example 3, the heat treatment was changed to 150 ° C. for 15 hours.

Comparative Example 10 In Example 3, the heat treatment was changed to 275 ° C. for 15 hours.

Comparative Example 11 In Example 3, a filler (calcium silicate) having a major axis of 50 μm and an aspect ratio of 3 was used in place of the carbon fiber in the same amount.

Comparative Example 12 In Example 3, the long diameter was 400 μm instead of carbon fiber.
The same amount of filler (glass fiber) having an aspect ratio of 10 was used.

Comparative Example 13 In Example 3, 2 parts by weight of carbon fiber and 98 parts by weight of carbon black were used.

Comparative Example 14 In Example 3, the carbon fiber was changed to 120 parts by weight and the carbon black was changed to 5 parts by weight.

With respect to the vulcanized sheets obtained in Example 3 and Comparative Examples 9 to 14, the physical properties in a normal state were measured in accordance with JIS K-6253 and JIS K-6251, and in accordance with JIS K-6255. Then, the rebound resilience at -20 ° C, 25 ° C and 70 ° C was measured.
Further, the surface roughness was measured as a substitute property of the adhesive property (a reduction in the contact area with the counterpart material was aimed at). In addition, the outgas amount due to heat extraction at 120 ° C for 5 hours (based on the headspace method)
GC-MS measurement). Further, the coefficient of friction was measured with a HEIDON surface property tester (load: 25 gf). The results obtained are shown in Table 2. Table 2 Example Comparative Example Measurement Items 3 9 10 11 12 13 14 Normal Properties Hardness (Durometer A) 75 72 79 72 66 75 84 Tensile Strength (MPa) 8.5 9.0 3.8 6.9 3.5 9.2 2.9 Elongation (%) 160 210 100 300 220 260 150 Rebound resilience (%) -20 ° C 23 26 28 20 21 21 25 25 ° C 19 24 21 26 25 23 28 70 ° C 24 27 25 27 27 26 30 Surface roughness Ra value 2.6 2.5 2.7 0.8 3.7 0.4 2.9 Outgas amount (μg / g) 4 70 4 3 3 4 2 Coefficient of friction 1.0 3.9 0.5 1.9 2.9 3.4 1.6

The above results show that the damping characteristics of Examples 1, 2, and 3 have low temperature dependence, and that Example 3 has a large surface roughness and reduced tackiness.
The outgas amount is as small as fluorine gas. In Comparative Examples 3 and 4, the temperature dependence of the damping characteristics was large.
In Nos. 11 and 13, the temperature dependence of the damping characteristics was small, but the surface roughness was small and no tackiness was imparted. Comparative Examples 12 and 14 have poor physical properties (low material strength). Comparative example
Samples 1 and 9 had a large amount of outgas, and Comparative Examples 2 and 10 had cracks on the rubber surface after heat treatment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F16F 7/00 F16F 7/00 BF term (reference) 3J066 AA22 AA29 BA01 BB01 BD05 4J002 BB07W BD14X BD15X BD16X DA018 DJ008 DJ048 DL008 EH077 EK016 EK036 EK046 EK056 EK066 EK086 EU027 EU187 EU197 FA048 FD018 FD020 FD070 FD147 FD156 GM00 GQ00

Claims (4)

[Claims] 1. 0.5 to 10 parts by weight of an organic peroxide and 0.5 to 10 parts by weight of a polyfunctional monomer per 100 parts by weight of a rubber comprising 100 to 40% by weight of an ethylene-alkyl acrylate copolymer rubber and 0 to 60% by weight of a fluoro rubber. Vulcanized molded product from the composition containing a part, the outgas amount per 1 g thereof is 20μg or less and the surface friction coefficient is 0.1 to 2.5
A rubber vulcanized molded product, characterized in that: 2. A composition containing 5 to 100 parts by weight of a filler having a major axis of 10 to 300 μm and an aspect ratio (ratio of major axis / minor axis) of 5 or more per 100 parts by weight of rubber. 2. The rubber vulcanized molded product according to claim 1. 3. The vulcanized rubber molded product according to claim 1, wherein a composition containing 5 to 100 parts by weight of a particulate filler having an average particle diameter of 10 to 300 μm per 100 parts by weight of rubber is used. 4. The rubber vulcanizate according to claim 1, which is used as a shock absorbing stopper part.