JPH09157445A - Vulcanizable rubber composition and pinch roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vulcanizable rubber composition excellent in balance between a coefficient of friction and wear resistance, especially suitable as a pinch roller for a magnetic tape apparatus, etc. SOLUTION: This vulcanizable rubber composition is obtained by blending (a) 100 pts.wt. of a nitrile group-containing highly saturated copolymer rubber prepared by hydrogenating a conjugate diene part of an unsaturated nitrile- conjugated diene-based rubber copolymer with (b) 10-60 pts.wt. of a zinc compound, (c) 20-60 pts.wt. of an α,β-ethylenic unsaturated carboxylic acid, (d) 0.1-30 pts.wt. of an organic peroxide-based vulcanizing agent, (e) 3-50 pts.wt. of a low-structure carbon black, (f) 5-40 pts.wt. of a plasticizer, (g) 0.1-30 pts.wt. of an organic peroxide-based vulcanizing agent and (h) an ethylene-α-olefin-based copolymer rubber. The weight ratio of the total of (a) the nitrile group- containing highly saturated copolymer rubber, (b) the zinc compound and (c) the α,β-ethylenic unsaturated carboxylic acid to (g) the ethylene-α-olefin-based copolymer rubber is 80/20 to 30/70.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vulcanizable rubber composition and a pinch roller suitable for a pinch roller used in a magnetic tape device or the like.

[0002]

2. Description of the Related Art A rubber mixture obtained by compounding an organic peroxide and a zinc salt of an ethylenically unsaturated carboxylic acid with a nitrile group-containing highly saturated copolymer rubber is combined with an ethylene-propylene copolymer rubber. It is known that a vulcanizable rubber composition is a rubber material having high strength and excellent weather resistance (for example, JP-A 1-313553). However, these rubber compositions are suitable for applications requiring high strength, oil resistance, etc. in addition to excellent weather resistance and heat resistance, such as various transmission belts for automobiles. However, in applications other than automobile parts, there are many unclear points in order to satisfy the required performance characteristic of the application.For example, magnetic tapes such as pinch rollers of magnetic tape devices are used. It was considered that the performance was insufficient for the application in which the function of smoothly and accurately transferring the material must be maintained for a long period of time.

Conventionally, silicone rubber, chloroprene rubber, urethane rubber or acrylonitrile-butadiene type rubber has been used for rubber coating of pinch rollers used in magnetic tape devices and the like, and various types have been used to stabilize the running of the magnetic tape. Method has been proposed (for example, JP-A-2-273357 and JP-A-61-222416).
No. 3, JP-A-1-187165, etc.). However, in recent years, there has been an increasing demand for higher performance of pinch rollers, and in some cases, conventional rubber materials are not sufficient to satisfy such demand, and an improved method has been desired.

[0004]

However, the present inventors have found that the vulcanizability obtained by blending a nitrile group-containing highly saturated copolymer rubber with an organic peroxide and a zinc salt of an ethylenically unsaturated carboxylic acid. When a low structure carbon black was added to the rubber composition, it was found that the friction coefficient and wear resistance were well balanced, and when this was applied to pinch roller applications, surprisingly, It was found that the magnetic tape has a good constant speed running property, and the present invention has been completed based on this finding.

[0005]

According to the present invention, the following (1) to (4) are provided. (1) (a) 10 to 60 parts by weight of a zinc compound with respect to 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber obtained by hydrogenating a conjugated diene part of an unsaturated nitrile-conjugated diene-based copolymer. Parts, (c) α, β-ethylenically unsaturated carboxylic acid 20 to 60 parts by weight (d) Organic peroxide vulcanizing agent 0.1 to 30 parts by weight, (e) Low structure carbon black 3 to 50 Parts by weight, (f) 5 to 40 parts by weight of a plasticizer, (g) 0.1 to 30 parts by weight of an organic peroxide vulcanizing agent, and (h) an ethylene-α-olefin copolymer rubber. Therefore, the total amount of the above (a) nitrile group-containing highly saturated copolymer rubber, (b) zinc compound and (c) α, β-ethylenically unsaturated carboxylic acid and (g) ethylene-α-
80/20 to 30/70 with olefin copolymer rubber
(Weight ratio) Vulcanizable rubber composition. (2) Compound of Group 2A metal of the periodic table (1)
The vulcanizable rubber composition according to 1. (3) The vulcanizable rubber composition according to (1), which is for a pinch roller. (4) A pinch roller comprising a vulcanized product obtained by vulcanizing the vulcanizable rubber composition according to (1) as a rubber coating.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Nitrile Group-Containing Highly Saturated Copolymer Rubber) The nitrile group-containing highly saturated copolymer rubber used in the present invention is obtained by hydrogenating a conjugated diene unit portion of an unsaturated nitrile-conjugated diene copolymer rubber. The content of bound unsaturated nitrile in the copolymer rubber is 10 to 50% by weight, preferably 15 to 40
% By weight, iodine value 80 or less, preferably 60 or less, and Mooney viscosity (ML _{1 + 4} , 100 ° C.) is 30 to 30.
The rubber is less than 0, preferably in the range of 50 to 200, and more preferably in the range of 60 to 150. The optimum content of bound unsaturated nitrile is selected according to the required performance.

When the iodine value exceeds 80, the heat resistance and strength are deteriorated. The lower limit of the iodine value is not particularly limited, but if the iodine value is excessively low, vulcanization may be difficult, so that an iodine value of at least 1 is generally used. If the Mooney viscosity is less than 30, the durability under high pressure for a long period of time is insufficient, and compression set and crushing (compression relaxation) are not improved. On the other hand, when it exceeds 300, the workability during kneading becomes poor.

The monomers used for producing the above-mentioned nitrile group-containing highly saturated copolymer rubber are exemplified. Specific examples of unsaturated nitriles include acrylonitrile, methacrylonitrile, and α-chloroacrylonitrile.

Specific examples of the conjugated diene include 1,3-butadiene, 2,3-dimethylbutadiene, isoprene,
1,3-pentadiene and the like can be mentioned.

In the case of an isoprene-butadiene-acrylonitrile copolymer rubber in which 1,3-butadiene and isoprene are used together as a conjugated diene, the amount of bonded 1,3-butadiene in the total amount of bonded conjugated dienes is usually 30 to 7.
0% by weight, and the amount of bound isoprene is 70 to 30% by weight.

Further, for the unsaturated nitrile-conjugated diene copolymer rubber, an ethylenically unsaturated monomer or other monomer capable of copolymerizing with the unsaturated nitrile and the conjugated diene is used. Examples thereof include vinyl aromatic compounds, ethylenically unsaturated carboxylic acid alkyl esters, ethylenically unsaturated carboxylic acid alkoxyalkyl esters, ethylenically unsaturated carboxylic acid fluoroalkyl esters, and (meth) acrylic acid cyano-substituted alkyl esters. it can.

Specific examples of the nitrile group-containing highly saturated copolymer rubber include acrylonitrile-butadiene copolymer rubber (NBR), acrylonitrile-butadiene-isoprene copolymer rubber (NBIR), acrylonitrile-isoprene copolymer rubber (NIR), Acrylonitrile-butadiene-acrylate copolymer rubber, acrylonitrile-butadiene-acrylic acid copolymer rubber, acrylonitrile-
Examples thereof include butadiene-acrylate-methacrylic acid copolymer rubbers and hydrogenated copolymer rubbers such as acrylonitrile-butadiene copolymer rubber hydrides (HNBR). These copolymer rubbers can be used alone or in combination of two or more.

Among them, a highly saturated type rubber obtained by hydrogenating an acrylonitrile-butadiene copolymer rubber is preferable, in which case the bound acrylonitrile amount is 10 to 40% by weight, the iodine value is 60 or less, preferably 40 or less, and the Mooney viscosity is 5
0 to 150.

Such an unsaturated nitrile-conjugated diene copolymer rubber is usually used in the presence of a radical polymerization initiator, if necessary with a molecular weight modifier, to obtain an unsaturated nitrile and a conjugated diene, and if necessary, other It is prepared by copolymerizing with an ethylenically unsaturated monomer.

The radical polymerization initiator to be used is not particularly limited, but organic peroxides, redox polymerization initiators, azo compounds, persulfates and the like are usually used. The amount of these polymerization initiators used is usually 0.005 to 3 parts by weight per 100 parts by weight of the total amount of the monomers. Also,
The polymerization temperature is preferably in the range of 0 to 100 ° C.

As the molecular weight regulator, 2,2 ', 4,
6,6'-pentamethylheptane-4-thiol, 2,
Alkylthiols such as 4,4-trimethylpentane-2-thiol, dodecane-12-thiol, 2,2,6,6-tetramethylheptane-4-methanethiol and 2,4,6-trimethylnonane-4-thiol Compounds;
Xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, and diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide Hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate,
Terpinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer (preferably 50% by weight or more of 2-4-diphenyl-4-methyl-1-pentene), 2,5-dihydrofuran, 3 , 6-
Examples thereof include dihydro-2H-pin, phthalane, 1,2-butadiene, 1,4-hexadiene and the like.
The amount of the molecular weight modifier used is usually 0.005 to 3 parts by weight based on 100 parts by weight of the total amount of the monomers.

The radical polymerization method is not particularly limited, and bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like can be appropriately selected as necessary. Of these, emulsion polymerization is preferred. In the case of production by emulsion polymerization, polymerization is carried out by a usual emulsion polymerization method, and when a predetermined conversion rate is reached, hydroxylamine, sodium carbamate, etc. are added to terminate the polymerization. Then, the residual monomer is removed by heating, steam distillation or the like. Furthermore, a coagulant such as an inorganic coagulant, a polymer coagulant, or a heat-sensitive coagulant used in ordinary emulsion polymerization is added to the obtained polymer latex to coagulate and recover the copolymer.

In producing the nitrile group-containing highly saturated copolymer rubber used in the present invention, the method of hydrogenating the conjugated diene unit portion of the unsaturated nitrile-conjugated diene copolymer rubber is not particularly limited, and is usually By using the hydrogenation method of.

Examples of the catalyst used in the hydrogenation include palladium / silica and palladium complex (JP-A-3-252405). Furthermore, JP-A-62-125858 and JP-A-62-42937.
JP-A-1-45402, JP-A-1-45403
It is also possible to use a rhodium or ruthenium compound as described in JP-A-1-45404 and JP-A-1-45405.

(Zinc Compound) Examples of the zinc compound used in the present invention include zinc oxide, zinc carbonate and zinc hydroxide. The compounding ratio of the zinc compound is
The amount is 10 to 60 parts by weight, preferably 15 to 55 parts by weight, based on 100 parts by weight of the nitrile group-containing highly saturated copolymer rubber. Of these, zinc oxide is preferred.

(Α, β-ethylenically unsaturated carboxylic acid)
As the α, β-ethylenically unsaturated carboxylic acid used in the present invention, acrylic acid, methacrylic acid, crotonic acid, 3
-Unsaturated monocarboxylic acids such as butenoic acid; maleic acid,
Unsaturated dicarboxylic acids such as fumaric acid and itaconic acid; Monoesters of unsaturated dicarboxylic acids such as monomethyl maleate, monomethyl fumarate and monomethyl itaconic acid; Unsaturated polycarboxylic acids other than the above; At least monovalent free carboxyl Examples thereof include esters of unsaturated polycarboxylic acids having a group remaining. Among these, methacrylic acid is particularly preferable from the viewpoints of physical properties and availability. The blending ratio of the α, β-ethylenically unsaturated carboxylic acid is 20 to 60 parts by weight, preferably 25 to 55 parts by weight, based on 100 parts by weight of the nitrile group-containing highly saturated copolymer rubber.

The zinc compound and the α, β-ethylenically unsaturated carboxylic acid are added to the nitrile group-containing highly saturated copolymer rubber and reacted in situ in the copolymer rubber to obtain α , Zinc salt of β-ethylenically unsaturated carboxylic acid is formed. In this case, as the zinc compound, it is preferable to remove coarse particles having a particle size of 20 μm or more in advance by classification, and to use a coarse particle content of 5% by weight or less, such as tensile strength of vulcanized rubber. It is preferable in improving the strength characteristics of.

The molar ratio of the α, β-ethylenically unsaturated carboxylic acid to the zinc compound calculated based on the molecular weight of the α, β-ethylenically unsaturated carboxylic acid and the formula weight of the zinc compound is usually It is in the range of 1: 0.5 to 1: 3.2, preferably 1: 0.5 to 1: 2.5.

(Carbon Black) The carbon black used in the present invention has a low structure among those generally used as a reinforcing agent for rubber. Here, the structure generally refers to the bonding shape of particles when the individual particles of carbon black are three-dimensionally bonded in a chain form or a tuft shape to form an aggregate, the number of particles forming the aggregate, and voids. It means the size of the volume.

The low structure means a carbon black test method for rubber (JIS K6221-1982 or AS.
According to TM D2414-90), n-dibutyl phthalate (DBP) oil absorption is 90 ml / 100 g or less.

Specific examples of the low-structure carbon black are illustrated by using abbreviations. For example, channel blacks include EPC and MPC; furnace blacks include ISAF-LS, HAF-LS and MAF-.
LS, FEF-LS, FF, HMF, GPF, SRF
Etc. Examples of the thermal black include MT, FT and the like. These can be used alone or in combination of two or more. Among them, FEF-LS, SRF, MA
The F-LS is used as a prize.

Further, it is also possible to use carbon black having a high structure, which has a DBP oil absorption of 118 ml / 100 g or more, within a range that does not impair the effects obtained by the present invention. As high structure carbon black, HPC, CC, ISAF-HS, HAF-H
S, MAF, FEF, APF, CRF, CF, SCF,
Examples thereof include ECF and HML.

Low structure carbon black is
It is compounded in an amount of 3 to 50 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the nitrile group-containing highly saturated copolymer rubber. If the amount of carbon black is excessively small, the abrasion resistance of the pinch roller deteriorates. If the amount of carbon black is excessively large, a large amount of plasticizer blended for adjusting the hardness of the pinch roller will bleed to the surface, which is not preferable.

(Plasticizer) As the plasticizer used in the present invention, one having a freezing point of 0 ° C. or lower, preferably −30 ° C. or lower, which is usually used as a plasticizer for rubber, is used. Specific examples thereof include phosphate-based compounds such as tributyl phosphate and tri-2-ethylhexyl phosphate; dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate,
Phthalates such as di-n-octyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate, octyldecyl phthalate, diisodecyl phthalate and butylbenzyl phthalate; aliphatic monobasic acids such as butyl oleate Ester type; dibutyl adipate, adipic acid n
An aliphatic dibasic acid ester system such as hexyl; a dihydric alcohol ester system such as diethylene glycol dibenzoate; an oxyacid ester system such as methyl acetylricinoleate. These can be used alone or in combination of two or more. Among them, phthalate ester-based plasticizers are preferred because of their low bleeding.

The plasticizer is used in an amount of 5 to 40 parts by weight, preferably 10 to 30 parts by weight, based on 100 parts by weight of the nitrile group-containing highly saturated copolymer rubber. If the amount of the plasticizer is excessively small, the friction coefficient of the pinch roller surface becomes large and the tape is worn, and if it is excessively large, the plasticizer bleeds on the surface of the pinch roller, which is not preferable.

(Organic Peroxide-Based Vulcanizing Agent) The organic peroxide-based vulcanizing agent used in the present invention may be any one used in ordinary rubber vulcanization and is not particularly limited. Not done. Examples include dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, benzoyl peroxide, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,
2,5-dimethyl-2,5-di (benzoylperoxy) hexyne, α, α′-bis (t-butylperoxy-m-isopropyl) benzene and the like can be mentioned. Of these, di-t-butyl peroxide is preferable. These organic peroxides are used in an amount of 0.1 to 30 parts by weight, preferably 0.5 to 100 parts by weight of a rubber mixture of a nitrile group-containing highly saturated copolymer rubber and an ethylene-α-olefin copolymer rubber. Used in the range of up to 20 parts by weight.

Further, an unsaturated compound usually used as a crosslinking aid in organic peroxide vulcanization may be mentioned.
Examples include ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N,
Examples thereof include N'-m-phenylene dimaleimide and triallyl isocyanurate. Of these, triallyl isocyanurate is preferable from the viewpoint of vulcanization properties. The addition amount of these is in the range of 0.1 to 15 parts by weight with respect to 100 parts by weight of the copolymer rubber.

(Ethylene-α-olefin Copolymer Rubber) The ethylene-α-olefin copolymer rubber used in the present invention is a copolymer of ethylene and α-olefin or a non-conjugated diene thereof. It is a substantially saturated copolymer rubber. Typical examples thereof include ethylene-propylene binary copolymer rubber, ethylene-propylene-butene ternary copolymer rubber, ethylene-1-bute binary copolymer rubber, and ethylene-propylene-non-conjugated diene. Terpolymer rubber, ethylene-propylene-1-butene-
Ethylene and carbon number 3 such as non-conjugated diene copolymer rubber and ethylene-1-butene-non-conjugated diene multipolymer rubber
Crystallinity of .alpha.-olefin of .about.14 as main component 20%
Below, preferably 10% or less of a low crystalline or amorphous elastomer or a mixture thereof. Among them, ethylene-propylene-non-conjugated diene terpolymer rubber is preferable.

Here, as the non-conjugated diene, dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, 5-ethylidene-2-norbornene and the like are used. Of these, dicyclopentadiene or 5 -A copolymer containing ethylidene-2-norbornene as a third component is preferable.

Mooney viscosity [ML _{1 + 4} (100 ° C.)] of ethylene-α-olefin-non-conjugated diene copolymer rubber
Is usually 10 to 180, preferably 40 to 140, and its iodine value is preferably 20 or less.

In these ethylene-α-olefin-non-conjugated diene copolymer rubbers, the ethylene unit / α-olefin unit is 50/50 to 90/10, preferably 60 /.
The ratio is 40 to 84/16 (molar ratio), and the (ethylene + α-olefin) unit / non-conjugated diene unit (in the case of a ternary or multi-component copolymer) is usually 98/2 to 90/1.
0, preferably 97/3 to 94/6 (molar ratio).

Ethylene of component (g) used in the present invention
The α-olefin copolymer rubber is usually a total amount of the above (a) nitrile group-containing highly saturated copolymer rubber, (b) zinc compound and (c) α, β-ethylenically unsaturated carboxylic acid and (g) ) 80/20 to 30/70 (weight ratio) with the ethylene-α-olefin copolymer rubber, preferably 70 /
It is used in the range of 30-40 / 60 (weight ratio). When the relative proportion of the nitrile group-containing highly saturated copolymer rubber is excessively large, the noise when applied to the pinch roller is lowered,
On the contrary, if the relative proportion of the ethylene-α-olefin-based copolymer rubber is excessively large, the abrasion resistance decreases.

(Blending Compound of Group 2A Metal of Periodic Table) Furthermore, by blending the compound of Group 2A metal of the periodic table to the vulcanizable composition of the present invention, the strength characteristics of the vulcanized rubber can be improved. When applied to a pinch roller, the wear resistance can be further improved.

Compounds of Group 2A metals of the periodic table include beryllium, magnesium, calcium, strontium,
Oxides, hydroxides, peroxides, carbonates, carbonates, carbonates, sulfates of Group 2A metals of the periodic table such as barium,
Examples thereof include nitrates, acetates, oxalates, phosphinates, phosphonates, phosphates, phosphohydrides and ammonium salts.

Specific examples of the above compounds include beryllium oxide, beryllium oxide, beryllium carbonate, beryllium nitrate and the like; and magnesium compounds include
Magnesium oxide, magnesium hydroxide, magnesium peroxide, magnesium carbonate, magnesium carbonate hydroxide,
Magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium oxalate, magnesium phosphinate, magnesium phosphonate, magnesium phosphate, magnesium hydride phosphate, magnesium ammonium phosphate, etc .; as the calcium compound, calcium oxide,
Calcium hydroxide, calcium peroxide, calcium carbonate, calcium sulfate, calcium nitrate, calcium acetate, calcium oxalate, calcium phosphonate, calcium phosphate, etc .; as strontium compounds, strontium oxide, strontium hydroxide, strontium peroxide, strontium carbonate, Strontium sulfate,
Strontium nitrate, strontium acetate, strontium oxalate salt, strontium phosphate, etc .; Barium compounds include barium oxide, barium hydroxide, barium peroxide, barium carbonate, barium sulfate, barium nitrate, barium acetate, barium oxalate, phosphinic acid Examples thereof include barium, barium phosphonate, and barium phosphate. A mixture of two or more of these may be mentioned.

Among these metal compounds, oxides and hydroxides of magnesium and alkaline earth metals are preferable. Especially, when magnesium oxide and magnesium hydroxide are used, a vulcanized rubber having a significantly improved tensile stress can be obtained. When calcium oxide and calcium hydroxide are used, strength characteristics such as tensile strength,
It is possible to stably obtain a high-strength vulcanized rubber without varying depending on manufacturing conditions such as kneading. Therefore, it is preferable to select these metal compounds or to use two or more kinds in combination according to the purpose of use of the vulcanized rubber, desired physical properties and the like.

The compound of Group 2A metal of the periodic table is usually added to 100 parts by weight of the nitrile group-containing highly saturated copolymer rubber.
0.5 to 30 parts by weight, preferably 0.5 to 20 parts by weight,
It is more preferably 1 to 10 parts by weight. If the blending ratio is too small, the tensile stress improving effect is small, and conversely, if the blending ratio is too large, the strength characteristics tend to be deteriorated. Further, when using an alkaline earth metal compound such as calcium oxide and calcium hydroxide, it is preferable to blend 2 parts by weight or more in order to stably obtain a high-strength vulcanized rubber.

If desired, the vulcanizable rubber composition of the present invention is used in ordinary rubber industry such as reinforcing agents such as silica, fillers such as calcium carbonate and talc, stabilizers, vulcanization aids and colorants. Various known additives can be added.

Further, if necessary, acrylic rubber, fluororubber, styrene-butadiene copolymer rubber, natural rubber,
Other rubbers such as polyisoprene rubber and ethylene-vinyl acetate copolymer resins and the like can be used in combination with the vulcanizable rubber composition of the present invention.

The method for producing the vulcanizable rubber composition of the present invention is not particularly limited, but usually, a nitrile group-containing highly saturated copolymer rubber and an ethylene-α-olefin-based rubber are mixed with a mixer such as a roll or a Banbury mixer. The rubber composition is produced by kneading and mixing the copolymer rubber and the vulcanization system and other compounding agents.

Specifically, usually, a nitrile group-containing highly saturated copolymer rubber, a zinc compound, an α, β-ethylenically unsaturated carboxylic acid, a metal compound of Group 2A of the periodic table, etc. are used in a roll, a Banbury, a kneader, or a nitrite. The mixture is kneaded by a shaft extruder or the like, and further ethylene-α-olefin copolymer rubber is added and kneaded. Then, at a temperature at which the organic peroxide does not decompose,
Add organic peroxide and knead. The vulcanized rubber composition obtained is molded into a desired shape and then heated to be vulcanized. Zinc compound and α, β-ethylenically unsaturated carboxylic acid,
By reacting at the stage of preparing a vulcanizable rubber composition, α, β-
It is believed to form zinc salts of ethylenically unsaturated carboxylic acids.

(Pinch roller) The vulcanizable rubber composition of the present invention has excellent performance as a rubber coating for a pinch roller used in a magnetic tape device or the like. The method for coating the pinch roller with rubber using such a rubber composition is not particularly limited, but the following method is adopted, for example.

The vulcanizable rubber composition was kneaded with a roll at 50 to 60 ° C., and 1.3 g of these compounds were filled in a mold,
A rubber ring having an inner diameter of 5.0 mmφ × an outer diameter of 10 mmφ × a width of 6 mm is prepared by compression molding using a compression molding machine under vulcanization (molding) conditions of 150 to 180 ° C. for 15 to 30 minutes. The molding pressure is 130 ± 20 Kg / cm ² . Next, a polyacetal core rod (outer diameter: 5.2 mmφ × width: 6.2 mm) was fastened with these rubber rings by rubber elastic force and covered, and surface roughness (Ra) = 0.8 ± 0.3 μm. Then, a pinch roller is manufactured by polishing and finishing.

[0049]

The present invention will be described more specifically with reference to the following examples. Parts and% in Examples, Comparative Examples and Reference Examples are based on weight unless otherwise specified. The characteristics of the rubber composition and the raw material components were measured as follows. (1) Vulcanized physical property evaluation test According to Japanese Industrial Standard JIS K6301, an unvulcanized rubber composition prepared according to the compounding recipe of Table 1 was 170 ° C x 30
3mm sheet obtained by vulcanization under the conditions of
A test piece was punched out using a No. Bendal to measure tensile strength (unit: kgf / cm ² ), 100% tensile stress (unit: kgf / cm ² ) and elongation (unit:%). The hardness was measured using a JIS spring type A hardness tester. Furthermore, compression set is JIS
According to K6301, the measurement was performed for the case of holding at 150 ° C. for 77 hours. (unit:%). (2) Friction coefficient (μ) A ball indenter load was applied to a vulcanized sheet prepared in the same manner as for the measurement of normal physical properties using a surface property tester (HEIDON-14S / D, manufactured by Shinto Scientific Co., Ltd.). It was measured at 100 g, a ball indenter sliding speed of 500 mm / min, and room temperature. (3) Abrasion amount The abrasion amount (mg) is the same vulcanizate as above according to JIS K6264, using a Taber abrasion tester and a load of 1 k.
g, rotation speed (grinding stone) H under the condition of rotation speed 1000 rpm
It measured using -18. Further, a wear test was performed using an Akron wear tester under the conditions of a load of 10 Lb, an angle of 25 degrees, and a rotation speed of 1000.

(4) Tape running test The vulcanizable rubber composition was kneaded by a roll at 50 to 60 ° C., 1.3 g of these compounds was filled in a mold, and 150 to 180 using a compression molding machine. Vulcanization (molding) for 15-30 minutes at ℃
Compressed and molded under the conditions of inner diameter 5.0 mmφ × outer diameter 10 mmφ
A rubber ring having a width of 6 mm is prepared. Molding pressure is 130
± 20 Kg / cm ² . Next, a polyacetal core rod (outer diameter: 5.2 mmφ × width: 6.2 mm) was fastened with these rubber rings by rubber elastic force and covered, and surface roughness (Ra) = 0.8 ± 0.3 μm. Then, a pinch roller is manufactured by polishing and finishing. In the magnetic tape running test, the surface state of the pinch roller after running for 2000 hours was observed for the pinch roller using a cassette tape for 30 minutes. (Adhesiveness) The extent to which the pinch roller surface is contaminated mainly due to the contact between the pinch roller and the metal capstan,
The evaluation was made in 3 stages. 3: No stain on pinch roller surface 2: Small amount of stain on pinch roller surface 1: Large amount of stain on pinch roller surface (wearability) Mainly, the extent to which the pinch roller surface is worn due to contact between the pinch roller and tape is 3 The grade was evaluated. 3: No wear of pinch roller surface 2: Small amount of wear of pinch roller surface 1: Large amount of wear of pinch roller surface (noise) Occurrence of squeak noise during the tape running test was evaluated in three stages. 3: No pinch roller squeaking noise 2: Small amount of pinch roller squeaking noise 1: Large amount of pinch roller squeaking noise

Examples 1 to 5 and Comparative Examples 1 to 4 According to the formulations shown in the upper part of Table 1, a nitrile group-containing highly saturated copolymer rubber (Zetpol 2020) and an ethylene-α-olefin copolymer rubber (EPDM) were used. ) Is mixed with it to prepare a vulcanizable rubber composition in which a low-structure carbon black, a plasticizer and an organic peroxide vulcanizing agent are mixed,
An evaluation test was conducted on these, and the results are shown in the lower part of Table 1. For comparison, vulcanizable rubber compositions containing chloroprene rubber (CR) and high-structure carbon black (FEF-HS) were prepared, and the same evaluation tests were performed on these compositions, and the results are shown in Table 1. Are also shown.

The nitrile group-containing highly saturated copolymer rubber is as follows. Binding acrylate Mooney Ronitoriru nitrile group-containing highly saturated copolymer rubber iodine value Viscosity amount (%) manufactured by Nippon Zeon (Ltd.) Zetpol 2020 28 78 36

The following was used as the ethylene-α-olefin copolymer rubber. Ethylene-propylene-dicyclopentadiene copolymer ethylene / propylene / dicyclopentadiene = 55 /
40/5 (molar ratio) Mooney viscosity 80

Further, the compounding recipe of the CR composition (Comparative Example 4)
Is as follows. CR (neoprene W) 100 parts FEF carbon black 40 parts Stearic acid 0.5 part MgO # 150 4 parts Nocrac PA 2 parts Zinc white # 1 5 parts Axel 22-S 0.5 parts Process oil 15 parts

[0055]

[Table 1]

The compounding ingredients in Table 1 are as follows. * 1) Dioctyl phthalate * 2) Organic peroxide-based vulcanizing agent / 1,3-bis (t-butylperoxyisopropyl) benzene * 3) Anti-aging agent / substituted diphenylamine

From the results shown in Table 1, it is understood that the vulcanized product obtained by vulcanizing the rubber composition of the present invention has an excellent balance between the friction coefficient and the wear resistance. Then, when this is applied to the pinch roller, it is found that the abrasion resistance, the adhesiveness, and the noise property are extremely small as compared with the case of CR or the like which has been conventionally used for the pinch roller application.

Particularly, in the experimental example (Example 1) in which the low-structure carbon black was used in combination with the plasticizer, the tackiness and abrasion resistance were higher than those in the high-structure carbon black (Comparative Example 1). Is greatly improved. Further, there is no squeaking noise when the tape is running, and the noise property is good.

[0059]

As described above, according to the present invention, a vulcanizable rubber composition suitable for applications such as magnetic tape devices and a pinch roller using the vulcanized product obtained by vulcanizing the rubber composition can be obtained. . The vulcanizate obtained by vulcanizing the rubber composition of the present invention has extremely less wear and tackiness than in the case of NBR or the like which has been conventionally used for pinch roller applications,
In addition, there is no squeaking noise when the tape is run for a long time, and the noise property is good.

Specific embodiments of the present invention are as follows. (1) The unsaturated nitrile in the unsaturated nitrile-conjugated diene-based copolymer rubber is selected from acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and the like. (2) The conjugated diene in the unsaturated nitrile-conjugated diene copolymer rubber is selected from 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene and the like. (3) The unsaturated nitrile-conjugated diene copolymer rubber is an acrylonitrile-butadiene copolymer rubber. (4) The ethylene-α-olefin copolymer rubber is an ethylene-propylene-non-conjugated diene terpolymer rubber. (5) The non-conjugated diene of the ethylene-α-olefin-non-conjugated diene copolymer rubber is dicyclopentadiene. (6) The compound of metal 2A in the periodic table is an oxide or hydroxide of magnesium and an alkaline earth metal. (7) Low structure carbon black is FEF
-LS, MAF-LS, SRF. (8) The plasticizer is a phthalate ester type. (9) The zinc compound is zinc oxide in which coarse particles having a particle size of 20 μm or more are removed in advance by classification to make the content rate of the coarse particles 5% or less. (10) The α, β-ethylenically unsaturated carboxylic acid is methacrylic acid. (11) The molar ratio of the α, β-ethylenically unsaturated carboxylic acid to the zinc compound calculated based on the molecular weight of the α, β-ethylenically unsaturated carboxylic acid and the formula weight of the zinc compound is
Usually 1: 0.5 to 1: 3.2, preferably 1: 0.5 to
The range is 1: 2.5.

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Claims (4)

[Claims] 1. To (a) 100 parts by weight of a nitrile group-containing highly saturated copolymer rubber obtained by hydrogenating a conjugated diene portion of an unsaturated nitrile-conjugated diene copolymer, (b) a zinc compound 10 to 10 parts by weight. 60 parts by weight, (c) 20 to 60 parts by weight of α, β-ethylenically unsaturated carboxylic acid, (d) 0.1 to 30 parts by weight of organic peroxide-based vulcanizing agent, (e) carbon black of low structure 3 to 50 parts by weight, (f) plasticizer 5
-40 parts by weight, (g) an organic peroxide-based vulcanizing agent 0.1-3
0 parts by weight and (h) an ethylene-α-olefin copolymer rubber are blended, and the (a) nitrile group-containing highly saturated copolymer rubber, (b) zinc compound and (c) α,
The total amount of β-ethylenically unsaturated carboxylic acid and (g) the ethylene-α-olefin-based copolymer rubber are 80 / 20-.
A vulcanizable rubber composition having a weight ratio of 30/70. 2. The vulcanizable rubber composition according to claim 1, wherein a compound of Group 2A metal of the periodic table is blended. 3. The vulcanizable rubber composition according to claim 1, which is for a pinch roller. 4. A pinch roller comprising a vulcanized product obtained by vulcanizing the vulcanizable rubber composition according to claim 1 as a rubber coating.