JP2006213743A - Hydrogenated nitrile rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogenated NBR composition wherein heat resistance is further improved while hardly deteriorating mechanical strength and oil resistance inherent in a hydrogenated nitrile rubber. <P>SOLUTION: The hydrogenated nitrile rubber composition comprises, per 100 pts.wt. hydrogenated nitrile rubber, 10-130 pts.wt. bituminous fine powder, 1-10 pts.wt. organic peroxide and 1-10 pts.wt. polyfunctional unsaturated compound. The hydrogenated nitrile rubber composition is excellent in characteristics regarding compression set, while heat resistance is demonstrated by a change in hardness after air-heat aging, a tensile strength change and an elongation change. A sealing material molded from such the hydrogenated nitrile rubber composition is effectively used as a sealing component of which high heat resistance is required, e. g. an O-ring used in an automobile engine, compressor, etc., a mechanical seal, a gasket, a packing, etc., and is also used as a sealing component for carbon dioxide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogenated nitrile rubber composition. More specifically, the present invention relates to a hydrogenated nitrile rubber composition having excellent heat resistance and compression set resistance.

  Hydrogenated nitrile rubber is widely used as various sealing materials because of its inherently excellent heat resistance, ozone resistance, oil resistance, and the like. In recent years, there has been a demand for further improvement in heat resistance due to higher performance of equipment, higher temperature of use environment accompanying reduction in size and weight.

In order to satisfy such a requirement, the applicant has first possessed hydrogenated nitrile rubber by adding white carbon and an organic peroxide having a specific surface area of about 20 to 200 m ² / g to the hydrogenated nitrile rubber. A hydrogenated nitrile rubber composition with improved heat resistance has been proposed with almost no loss of mechanical strength and oil resistance. However, although this composition achieves the desired object, further improvement is required in terms of compression set.
Japanese Patent Laid-Open No. 9-3246

On the other hand, Patent Document 2 proposes a nitrile rubber-based molding material in which hydrogenated nitrile rubber is mixed with Austin Black and natural mica. This hydrogenated nitrile rubber composition is excellent in gas sealability against carbon dioxide gas, but requires improvement in terms of compression set resistance.
JP 2003-119320 A

  An object of the present invention is to provide a hydrogenated NBR composition that further improves its heat resistance without substantially impairing the mechanical strength and oil resistance inherent to the hydrogenated nitrile rubber.

  The object of the present invention is to contain 10 to 130 parts by weight of a bituminous fine powder, 1 to 10 parts by weight of an organic peroxide and 1 to 10 parts by weight of a polyfunctional unsaturated compound per 100 parts by weight of a hydrogenated nitrile rubber. This is achieved by the hydrogenated nitrile rubber composition.

  The hydrogenated nitrile rubber composition of the present invention has excellent properties in compression set in addition to heat resistance indicated by change in hardness, tensile strength change rate, elongation change rate after air heat aging. Seal materials molded from such hydrogenated nitrile rubber compositions are seals that require strict heat resistance, such as O-rings, mechanical seals, gaskets, and packing used in automobile engines and compressors. It is used effectively as a part. It is also used as a carbon dioxide gas sealing part.

  As the hydrogenated nitrile rubber, any commercially available acrylonitrile rubber can be used without any limitation regardless of the amount of bound acrylonitrile, iodine value, or Mooney viscosity. For example, the Nippon Zeon product Zetpol series can be used as it is, and can be selected according to each application such as cold resistance and oil resistance.

  As the bituminous fine powder, coal is pulverized and pulverized to an average particle size of 10 μm or less, usually 1 to 10 μm, preferably 3 to 8 μm, and a specific gravity of 1.25 to 1.45 is used. If the average particle size is larger than this, sufficient reinforcing properties cannot be obtained.

  Such a bituminous fine powder is used in a proportion of 10 to 130 parts by weight, preferably 30 to 120 parts by weight, per 100 parts by weight of hydrogenated nitrile rubber. If the bituminous fine powder is used in a smaller proportion, the desired heat resistance effect cannot be obtained. On the other hand, if it is used in a larger proportion, kneading and molding become difficult due to a decrease in the rubber component. .

  The hydrogenated nitrile rubber composition comprising the above components is peroxide-crosslinked using an organic peroxide. Examples of organic peroxides include di-tertiary butyl peroxide, dicumyl peroxide, tertiary butyl cumyl peroxide, 1,1-di (tertiary butyl peroxy) -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 (benzoylperoxy) ) Hexane, tertiary butyl peroxybenzoate, tertiary butyl peroxy isopropyl carbonate, n-butyl-4,4'-di (tertiary butyl peroxy) valerate, etc., about 1 to 100 parts by weight of hydrogenated nitrile rubber It is used in a proportion of 10 parts by weight, preferably about 2-8 parts by weight. If the organic peroxide is used in a smaller proportion, a vulcanized molded product having a sufficient crosslinking density cannot be obtained. On the other hand, if it is used in a proportion higher than this, a vulcanized molded product cannot be obtained by foaming. Even when a molded product is obtained, the rubber elasticity or elongation is reduced, which is not preferable.

  In organic peroxide crosslinking, a polyfunctional unsaturated compound is used in combination as a co-crosslinking agent. This can be used without particular limitation as long as it is generally usable for hydrogenated nitrile rubber, such as triallyl (iso) cyanurate, trimethylolpropane tri (meth) acrylate, triallyl trimellitate, N , Nm-phenylene bismaleimide, butadiene oligomer and the like are used. These polyfunctional unsaturated compounds are used in a proportion of 1 to 10 parts by weight, preferably 3 to 8 parts by weight, per 100 parts by weight of hydrogenated nitrile rubber. If the polyfunctional unsaturated compound is used in a smaller proportion, sufficient heat resistance is not improved. On the other hand, if it is used in a larger proportion, a vulcanized molded product cannot be obtained due to foaming or molding. Even when a product is obtained, a decrease in rubber elasticity or a decrease in elongation occurs, which is not preferable.

  In addition to the above essential components, the composition contains reinforcing agents such as carbon black and white carbon, fillers such as talc, clay, graphite and calcium silicate, processing aids such as stearic acid, palmitic acid and paraffin wax. Various compounding agents generally used in the rubber industry, such as acid acceptors such as zinc oxide, magnesium oxide and hydrotalcite, anti-aging agents, and plasticizers, are appropriately added and used.

  The rubber composition is prepared by kneading using a kneader such as an intermix, kneader, Banbury mixer or an open roll. The vulcanization is performed using an injection molding machine, a compression molding machine, a vulcanizing press, or the like. In general, it is carried out by heating at about 150 to 200 ° C. for about 3 to 60 minutes, and if necessary, secondary vulcanization is carried out at about 100 to 200 ° C. for about 0.5 to 24 hours.

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

Example Hydrogenated nitrile rubber (Nippon Zeon product Zetpol 1020) 100 parts by weight Bituminous fine powder (Keystone Filler & Mfg product Mineral Black 325BA 60 〃
(Average particle size 6μm)
N990 carbon black 10 〃
Triallyl isocyanurate 5 〃
Zinc oxide 5 〃
Stearic acid 1 〃
Diphenylamine anti-aging agent (Ouchi Emerging Chemical Product NOCRACK CD) 1
Imidazole-based anti-aging agent (Company product NOCRACK MBZ) 1 〃
Dicumyl peroxide 3 〃
The above components were kneaded with a kneader and an open roll, and this was press-crosslinked at 170 ° C. for 20 minutes to form a 150 × 150 × 2 mm vulcanized sheet and a P-24 size O-ring.

Comparative Example 1
In the examples, triallyl isocyanurate was not used.

Comparative Example 2
In Example 1, instead of triallyl isocyanurate, bituminous fine powder and N990 carbon black, 55 parts by weight of wet method white carbon (specific surface area: 80 m ² / g) and vinyl silane coupling agent (Nihon Unicar Product A) -172) 1 part by weight was used.

Comparative Example 3
In Example 1, the amount of bituminous fine powder was changed to 5 parts by weight, and the amount of N990 carbon black was changed to 80 parts by weight.

Comparative Example 4
In Example 1, when the amount of bituminous fine powder was changed to 150 parts by weight and N990 carbon black was not used, kneading was impossible because the viscosity of the blend was too high.

Comparative Example 5
In Example 1, when the dicumyl peroxide amount was changed to 0.5 parts by weight, a sufficient crosslink density could not be obtained, and a normal test piece could not be obtained.

Comparative Example 6
In Example 1, when the dicumyl peroxide amount was changed to 12 parts by weight, it was vulcanized and foamed, and a normal test piece was not obtained.

Comparative Example 7
In Example 1, the amount of triallyl isocyanurate was changed to 0.5 parts by weight.

Comparative Example 8
In Example 1, when the triallyl isocyanurate amount was changed to 12 parts by weight, it was vulcanized and foamed, and a normal test piece was not obtained.

Using the vulcanized sheets obtained in the above Examples and Comparative Examples 1, 2, 3, and 7, normal physical properties and an air heat aging test were performed, and a compression set test was performed on the O-ring.
Normal physical properties: JIS K6253, K6251 compliant Air heating aging test: JIS K6257 compliant Compression set test: JIS K6262 compliant

The results obtained are shown in the following table.
table
Comparative example
Measurement Item Example 1 2 3 7
Normal physical properties Hardness (Durometer A) 80 81 80 80 80
Tensile strength (MPa) 16.2 13.5 22.0 17.5 13.6
Elongation (%) 530 500 450 380 520
Air heating aging test (150 ° C, 70 hours)
Change in hardness (points) +1 +1 +3 +4 +2
Tensile strength change rate (%) +2 +0 +6 +9 +1
Rate of change in elongation (%) -28 -31 -19 -12 -28
Air heating aging test (150 ° C, 168 hours)
Change in hardness (points) +3 +3 +4 +5 +3
Tensile strength change rate (%) +3 -2 +17 +7 +2
Elongation change rate (%) -45 -42 -27 -20 -38
Air heating aging test (150 ° C, 336 hours)
Change in hardness (points) +5 +5 +7 +8 +5
Tensile strength change rate (%) +2 +3 +34 +17 +0
Elongation change rate (%) -58 -61 -42 -39 -60
Air heating aging test (150 ° C, 500 hours)
Change in hardness (points) +6 +6 +7 +9 +6
Tensile strength change rate (%) +0 -1 +36 +26 +3
Elongation change rate (%) -66 -72 -60 -56 -70
Compression set test (150 ° C)
After 70 hours (%) 28 31 38 39 31
168 hours later (%) 34 38 50 59 37
336 hours later (%) 42 47 63 73 47
After 500 hours (%) 49 55 74 80 56

Claims (4)

  Hydrogenated nitrile rubber composition comprising 10 to 130 parts by weight of bituminous fine powder, 1 to 10 parts by weight of organic peroxide and 1 to 10 parts by weight of polyfunctional unsaturated compound per 100 parts by weight of hydrogenated nitrile rubber object.   The hydrogenated nitrile rubber composition according to claim 1, wherein the bituminous fine powder is a fine coal powder having an average particle size of 10 µm or less.   The hydrogenated nitrile rubber composition according to claim 1 or 2, which is used as a molding material for a sealing material. A sealing material obtained by crosslinking and molding the hydrogenated nitrile rubber composition according to claim 3.