JP7349853B2 - Rubber member and conveyance roller using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber member and a conveyance roller used in printing devices such as printers, automatic teller machines, etc. using the rubber member.

As shown in FIG. 1, the conveyance roller is a member used in printing devices such as printers, automatic teller machines, etc., and conveys a medium. Since dimensional changes due to wear and deformation are a must for conveyance rollers, hydrogenated nitrile rubber (H-NBR), which has excellent wear resistance and deformation resistance, is often used.

Since nitrile rubber (NBR) contains unsaturated bonds (carbon-carbon double bonds) in its polymer main chain, it has the disadvantage of poor chemical stability such as heat resistance, weather resistance, and ozone resistance. Therefore, hydrogenated nitrile rubber (H-NBR) is produced by hydrogenating the unsaturated bond portion to change the unstable unsaturated bond into a saturated bond. The hydrogenation reaction reduces the amount of residual double bonds in the main chain of the polymer, improving heat resistance, chemical resistance, weather resistance, etc.
However, since H-NBR requires an extra hydrogenation step than NBR, it is disadvantageous in terms of resources and energy. Furthermore, the technology for economically hydrogenating NBR is not simple, and requires labor for technical development, equipment maintenance, maintenance and inspection, etc.

Japanese Patent Application Publication No. 2000-86842 Japanese Unexamined Patent Publication No. 62-54746

By the way, some products do not require as much heat resistance and oil resistance as H-NBR. If H-NBR, which is relatively expensive, is used in such products, there are problems in that the product will be over-specified and the productivity will be low.

In particular, when considering alternatives to H-NBR, which are used in conveyance rollers that convey media used in printing equipment such as printers and automatic teller machines, the following problems are unique to conveyance rollers: .
(1) Naturally, it is necessary to have physical properties equivalent to or better than H-NBR. In particular, wear resistance and deformation resistance (permanent deformation resistance) are important.
(2) Depending on the location where automated teller machines are installed, they may be exposed to the outside air or placed in harsh environments. It is required to maintain good rubber physical properties even under such environments. In particular, low temperature properties are important.
(3) Silicone oil, etc. is often added to improve wear resistance, but this may bleed and be transferred to other parts that come into contact with the rollers or to the conveyed object, causing contamination. This is a fatal defect for the conveyance roller. Therefore, it is necessary to achieve the target physical properties without relying on silicone oil or the like.

Under these circumstances, the inventors of the present invention focused on chlorinated polyethylene, which is cheaper and has better wear resistance than H-NBR. We worked on developing rubber parts that have these properties.
Although chlorinated polyethylene has excellent abrasion resistance, it tends to have poor deformation resistance because of its weak rubber elasticity. Furthermore, since its low-temperature properties are worse than that of H-NBR, another drawback is that its usable temperature range is narrower. In order to compensate for these drawbacks, studies have been conducted to blend chlorinated polyethylene with ethylene-propylene-diene copolymer rubber, which has rubber elasticity and excellent low-temperature properties.

According to Patent Document 1, silicone oil is added to a blend rubber with a chlorine content of 28 to 33%, which is made of 95 to 70% by weight of chlorinated polyethylene and 5 to 30% by weight of ethylene-propylene-diene copolymer rubber. It is said that vulcanized molded products with excellent mechanical properties, low-temperature properties, grease resistance, abrasion resistance, etc. can be obtained from chlorinated polyethylene blend rubber compositions with lower coefficients. However, within the range of the ratio of chlorinated polyethylene and ethylene-propylene-diene copolymer rubber taught in Patent Document 1, although the abrasion resistance is good, the permanent deformation resistance is poor for use as a conveyor roller, and the low-temperature characteristics I can't say it's enough. Additionally, adding silicone oil improves wear resistance by reducing friction, but as the silicone oil bleeds out, it is transferred to other parts and objects that come into contact with the conveyor roller, causing contamination. Unable to overcome shortcomings.

According to Patent Document 2, it is a composition consisting of (A) amorphous chlorinated polyethylene, (B) crystalline chlorinated polyethylene, and (C) ethylene-propylene-diene multicomponent copolymer rubber; The composition ratio of amorphous chlorinated polyethylene and ethylene-propylene-diene multi-component copolymer rubber in the total amount is 30 to 85% by weight, and the proportion of ethylene-propylene to 100 parts by weight of amorphous chlorinated polyethylene is 30 to 85% by weight. -Mechanical properties, hardness, electrical properties, rubber properties from rubber compositions containing 25 to 75 parts by weight of diene multi-component copolymer rubber and sulfur or sulfur donor as a vulcanizing agent. It is said that molded products with a good balance of physical properties such as flame retardancy can be obtained.
However, the ratio of chlorinated polyethylene and ethylene-propylene-diene multicomponent copolymer rubber taught in Patent Document 2 is very wide, and the product is stable over the entire range and has excellent abrasion resistance and permanent deformation resistance. cannot be obtained.
Specifically, in Patent Document 2, sulfur or a sulfur donor is used as a vulcanizing agent, but the product characteristics differ depending on whether sulfur is used or an organic peroxide is used. There is no disclosure or suggestion that significant differences will occur.
Further, in Patent Document 2, it is necessary to blend crystalline chlorinated polyethylene.

Therefore, the problem to be solved by the present invention is to use a rubber composition containing chlorinated polyethylene and an ethylene-α-olefin-nonconjugated polyene copolymer instead of H-NBR, to prevent silicone from bleeding. It has an excellent balance of wear resistance, deformation resistance (permanent deformation resistance), and low-temperature properties without relying on the surface friction reduction effect of blending with oil, etc., and is used in printing equipment such as printers, automatic teller machines, etc. It is an object of the present invention to provide a rubber member suitable for a conveyance roller or the like that conveys a medium.

The present invention includes the following.
[1] Contains ethylene-α-olefin-nonconjugated polyene copolymer (a), amorphous chlorinated polyethylene (b), and organic peroxide, a total of 100 parts by weight of (a) and (b) A crosslinked cured product of a rubber composition in which (b) is 50 parts by weight or more and less than 70 parts by weight, and the crosslinked cured product has a crosslink density of 5.50×10 ⁻⁴ mol/ml or more. rubber parts.
[2] The rubber member according to [1], wherein the ethylene-α-olefin-nonconjugated polyene copolymer (a) is ethylene-propylene-diene copolymer rubber (EPDM).
[3] The wear volume after 1000 rotations in the Taber wear test according to JIS K6264 is 0.039 cm ³ or less,
The rubber member according to [1] or [2], which has a compression set of 10% or less according to JIS K6262, and a TR10 of -22°C or less according to a low temperature elastic recovery test according to JIS K6261.
[4] A conveyance roller including the rubber member according to any one of [1] to [3].

As will be specifically described later in this specification, the present inventors have found that the use of an organic peroxide as a vulcanizing agent, compared to the case of using sulfur, increases the permanent deformation resistance required for conveyor roller applications. It was discovered for the first time that sexual performance significantly improved. Furthermore, regarding wear resistance, it has been found that there is an optimal range for the blending ratio of chlorinated polyethylene. As a result, by improving not only wear resistance but also deformation resistance (permanent deformation resistance), the rubber member according to the present invention can minimize dimensional changes due to long-term use even when used as a conveyance roller, for example. Therefore, it is possible to reduce the amount of heat generated and extend the service life.
In addition, as will be specifically described later in this specification, the present inventors have found that when amorphous chlorinated polyethylene is blended, compared to when crystalline chlorinated polyethylene is blended, the requirements for conveyance roller applications are higher. It has been discovered for the first time that significant improvements can be obtained in all of the wear resistance, deformation resistance, and low-temperature properties of the material. By successfully achieving a balance between wear resistance, deformation resistance, and low-temperature properties in this way, the rubber member can be used in a wide temperature range.
Furthermore, since the rubber member according to the present invention does not bleed, there is an advantage that there is no fear of transfer or contamination to a mating member that comes into contact with the rubber member.

FIG. 2 is a schematic diagram of the appearance of a conveyance roller (one rotating support shaft, two rubber members).

<Material>
[Ethylene-α-olefin-nonconjugated polyene copolymer (a)]
The α-olefin in the ethylene-α-olefin-nonconjugated polyene copolymer rubber is, for example, propylene or butene. Therefore, the ethylene-α-olefin-nonconjugated polyene copolymer rubber is at least one type selected from the group consisting of ethylene-propylene-diene copolymer (EPDM) and ethylene-butene-diene copolymer (EBDM). It is preferably ethylene-propylene-diene copolymer (EPDM), and more preferably ethylene-propylene-diene copolymer (EPDM).

Non-conjugated polyenes include 5-ethylidene-2-norbornene, dicyclopentadiene, 5-propylidene-2-norbornene, 5-vinyl-2-norbornene, 2,5-norbornadiene, 1,4-cyclohexadiene, 1,4 -Cyclic polyenes such as cyclooctadiene and 1,5-cyclooctadiene, 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 5-methyl-1,5 -heptadiene, 6-methyl-1,5-heptadiene, 6-methyl-1,6-octadiene, 7-methyl-1,6-octadiene, 5,7-dimethyl-1,6-octadiene, 7-methyl-1 ,7-nonadiene, 8-methyl-1,7-nonadiene, 8-methyl-1,8-decadiene, 9-methyl-1,8-decadiene, 4-ethylidene-1,6-octadiene, 7-methyl-4 -ethylidene-1,6-octadiene, 7-methyl-4-ethylidene-1,6-nonadiene, 7-ethyl-4-ethylidene-1,6-nonadiene, 6,7-dimethyl-4-ethylidene-1,6 - Chain polyenes having internal unsaturated bonds having 6 to 15 carbon atoms, such as octadiene and 6,7-dimethyl-4-ethylidene-1,6-nonadiene, as well as 1,5-hexadiene, 1,6-heptadiene, α,ω-dienes such as 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene and 1,13-tetradecadiene There is.

Preferably, a non-conjugated polyene consisting of 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene (VNB), dicyclopentadiene (DCPD) or 1,4-hexadiene (1,4-HD) At least one compound selected from the group. In particular, 5-ethylidene-2-norbornene is more preferable because it has high polymerization reactivity and therefore easily causes crosslinking reactions.

Therefore, examples of ethylene-α-olefin-nonconjugated polyene copolymer rubber suitable for carrying out the present invention include ethylene-propylene-5-ethylidene-2-norbornene copolymer rubber, ethylene-propylene-5- Vinyl-2-norbornene copolymer rubber, ethylene-propylene-dicyclopentadiene copolymer rubber, ethylene-propylene-1,4-hexadiene copolymer rubber, ethylene-1-butene-5-ethylidene-2-norbornene copolymer rubber Polymer rubber, ethylene-1-butene-5-vinyl-2-norbornene copolymer rubber, ethylene-1-butene-dicyclopentadiene copolymer rubber, ethylene-1-butene-1,4-hexadiene copolymer Rubber can be mentioned.

Further, the ethylene-α-olefin-nonconjugated polyene copolymer rubber preferably has an ethylene content of 55% or more and 65% or less. If the amount of ethylene is less than 55%, wear resistance may deteriorate, and if the amount of ethylene is more than 65%, low temperature properties may deteriorate.

In addition to the above, the properties of the ethylene-α-olefin-nonconjugated polyene copolymer rubber are also affected by the molecular structure, such as the degree of branching, average molecular weight, molecular weight distribution, etc. Many types of ethylene-α-olefin-nonconjugated polyene copolymer rubber are known, and any of them can be used in the present invention as long as the effects of the present invention are not impaired.

Commercially available ethylene-α-olefin-nonconjugated polyene copolymer rubbers include VNB-EPT (EPDM manufactured by Mitsui Chemicals, Inc.), Espren 501A (EPDM manufactured by Sumitomo Chemical Co., Ltd.), and EBT 9330M (manufactured by Mitsui Chemicals, Inc.). EBDM), Esplen 505A (EPDM manufactured by Sumitomo Chemical Co., Ltd.), and the like.

[Amorphous chlorinated polyethylene (b)]
Chlorinated polyethylene is polyethylene that has been chlorinated (some of the hydrogen in the molecule is replaced with chlorine) by a process well known in the industry, such as treating polyethylene with a chlorine-containing compound such as trichloroethane or carbon tetrachloride. Polyethylene.

The chlorinated polyethylene suitable for the practice of this invention is amorphous chlorinated polyethylene. In the present invention, it is preferable that crystalline chlorinated polyethylene is not blended.

The chlorine content of the amorphous chlorinated polyethylene is not particularly limited, but is preferably 28 to 37% by weight, more preferably 28 to 33% by weight. When the chlorine content of the amorphous chlorinated polyethylene is within the above range, a rubber member with high flexibility and good deformation resistance and low-temperature properties can be easily obtained.

Examples of the chlorinated polyethylene include Elasrene 301A manufactured by Showa Denko K.K., H135 manufactured by Daiso, Tyrin 3615 and Tyrin 3611 manufactured by Dupont Dow Elastomer.

Regarding the blend ratio of ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b), the ratio of ethylene-α-olefin-nonconjugated polyene copolymer (a) If the ratio is too small, a sufficient softening effect cannot be expected, and on the other hand, if the ratio is too large, the inherent abrasion resistance of amorphous chlorinated polyethylene (b) will be impaired, so blend at an appropriate ratio. This is very important. Furthermore, within a predetermined range, the greater the ratio of the ethylene-α-olefin-nonconjugated polyene copolymer (a), the better the deformation resistance of the resulting rubber member. In the present invention, (b) is contained in an amount of 50 parts by weight or more and less than 70 parts by weight based on a total of 100 parts by weight of (a) and (b).

Moreover, regardless of the size of the blend ratio, the higher the crosslinking density of the cured product, the better the deformation resistance of the resulting rubber member. In the present invention, the crosslinking density is set to 5.50×10 ⁻⁴ mol/ml or more.

[Organic peroxide]
Sulfur, which is commonly used as a crosslinking agent for rubber, is not preferred because the formation of a crosslinked structure is difficult to proceed, resulting in a low crosslinking density and poor deformation resistance of the resulting rubber member. Therefore, in the present invention, rubber is crosslinked using an organic peroxide without using sulfur or a sulfur donor.
Organic peroxides used as crosslinking agents in the present invention include peroxycarbonates, diacyl peroxides, dialkyl peroxides, peroxyketals, and alkyl peresters.

Peroxycarbonates include 1,6-bis(t-butylperoxycarbonyloxy)hexane, 1,6-bis(1,1-dimethylpropylperoxycarbonyloxy)hexane, 1,6-bis(1 , 1-dimethylbutylperoxycarbonyloxy)hexane, 1,6-bis(1,1,3,3-tetramethylbutylperoxycarbonyloxy)hexane, 1,6-bis(t-butylperoxycarbonyloxy)hexane, bis[t-(C4-C10)alkylperoxycarbonyloxy]((C3-C10) alkanes, diethylene glycol-bis (t-butyl peroxycarbonate), diethylene glycol-bis(1,1-dimethylpropyl peroxycarbonate), diethylene glycol-bis(1,1-dimethylbutyl peroxycarbonate), diethylene glycol-bis(1,1,3,3 di- or tri(C2-C3) alkylene glycol-bis[t-(C4-C10) alkyl peroxycarbonate] such as -tetramethylbutylperoxycarbonate), triethylene glycol-bis(t-butylperoxycarbonate), t-Butylperoxy 2-ethylhexyl carbonate, 1,1-dimethylpropylperoxy 2-ethylhexyl carbonate, 1,1-dimethylbutylperoxy 2-ethylhexyl carbonate, 1,1,3,3-tetramethylbutylperoxy 2 -Ethylhexyl carbonate, t-butylperoxyisopropyl carbonate, 1,1-dimethylpropylperoxyisopropyl carbonate, 1,1-dimethylbutylperoxyisopropyl carbonate, 1,1,3,3-tetramethylbutylperoxyisopropyl carbonate, etc. Examples include t-(C4-C10)alkylperoxy(C3-C8))alkyl carbonates.

Examples of diacyl peroxides include dibenzoyl peroxide, bis(2-methylbenzoyl) peroxide, bis(3-methylbenzoyl) peroxide, bis(4-methylbenzoyl) peroxide, and bis(2,4-dimethylbenzoyl). Peroxide, bis(3,5-dimethylbenzoyl) peroxide, bis(2-chlorobenzoyl) peroxide, bis(3-chlorobenzoyl) peroxide, bis(4-chlorobenzoyl) peroxide, bis(2,4 -dichlorobenzoyl) peroxide, bis(3,5-dichlorobenzoyl) peroxide, and other bis[unsubstituted or chlor-substituted or (C1 to C3) alkyl-substituted benzoyl] peroxides.

The dialkyl peroxides include di[(C3 to C12) alkyl] peroxide which may have phenyl substitution or two (C3 to C12) alkyl peroxide groups which may have phenyl substitution and 8 carbon atoms. Examples include dialkyl peroxides bonded via ~12 hydrocarbon bridging groups, specifically dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2, 5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3,1,3-bis(t-butylperoxyisopropyl)benzene, t-butylcumyl peroxide, di-t-butyl peroxide, etc. can be mentioned.

Peroxyketals include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, and 2,2-bis(t-butylperoxycyclohexane). oxy)butane, 2,2-bis(1,1-dimethylpropylperoxy)butane, 2,2-bis(1,1-dimethylbutylperoxy)butane, 2,2-bis(1,1,3, Examples include 3-tetramethylbutylperoxy)butane, 4,4-di-t-butylperoxy-n-butylvalerate, and the like.

Examples of alkyl peresters include t-butylperoxybenzoate, 1,1-dimethylpropylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, and 1,1-dimethylpropylperoxy-2-ethylhexanoate. Noate, 1,1-dimethylbutylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di-t-butylperoxyhexahydroterephthalate , t-butylperoxy-3,5,5-trimethylhexanoate, 1,1-dimethylpropylperoxy-3,5,5-trimethylhexanoate, 1,1-dimethylbutylperoxy-3,5 , 5-trimethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-3,5,5-trimethylhexanoate, and the like.
These can also be used as diluted products or masterbatch products using silica or calcium carbonate as a carrier.

Among the above organic peroxides, at least one selected from the group consisting of dialkyl peroxides and peroxyketals is preferred. By using these, the crosslinking efficiency can be increased, and the thermal stability during kneading and processing of the rubber can also be easily increased.

The amount of organic peroxide to be used is not particularly limited as long as the crosslinking density of the cured product of the rubber composition according to the present invention can be set to 5.50×10 ⁻⁴ mol/ml or more. For example, the amount of organic peroxide blended is 100% of the total weight of the ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b) in the rubber composition according to the present invention. It is more than 1.2 parts by weight and not more than 2.4 parts by weight.

Commercially available organic peroxides include Percyl D (dialkyl peroxide manufactured by NOF Corporation), Perhexa 25B (dialkyl peroxide manufactured by NOF Corporation), Perhexa C (peroxyketal manufactured by NOF Corporation), etc. It will be done.

[Other additives]
The rubber composition according to the present invention may further contain a co-crosslinking agent that improves the crosslinking efficiency of the rubber, carbon black that improves the mechanical properties, a softener, an anti-aging agent, a processing aid, etc. .

[Co-crosslinking agent]
As a co-crosslinking agent, triallyl isocyanurate, triallyl cyanurate, triallyl isocyanate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, glycidyl methacrylate, diallyl phthalate, quinone Dioximes, bismaleimides, dimethacrylic acid metal salts, diacrylic acid metal salts, sulfur compounds, 1,2-polybutadiene, and the like can be used.
The amount of the co-crosslinking agent is based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b) in the rubber composition of the present invention. , preferably 0.1 to 10 parts by weight, more preferably 0.5 to 3 parts by weight.

[Carbon black]
By incorporating carbon black as a filler into the rubber composition according to the present invention, the mechanical properties of the resulting rubber member can be improved. There are various types of carbon black, and an appropriate one is selected and used depending on the purpose. As the carbon black, any known carbon black can be used, and examples thereof include SAF, ISAF, HAF, MAF, FEF, GPF, SRF, etc., which are furnace blacks commonly used for rubber. Carbon black may be used alone or two or more types may be blended.

Preferably, carbon black with an iodine adsorption amount of 80 mg/g or less is used. More preferably, one with an iodine adsorption amount of 20 to 40 mg/g is used, which provides a good balance between wear resistance and deformation resistance.

Specifically, commercially available products include Asahi F-200GS (manufactured by Asahi Carbon Co., Ltd., iodine adsorption amount: 55 mg/g), Asahi #60U (Asahi Carbon Co., Ltd., iodine adsorption amount: 40 mg/g), Asahi #55 (manufactured by Asahi Carbon Co., Ltd., iodine adsorption amount: 40 mg/g), Asahi Carbon Co., Ltd., iodine adsorption amount: 25 mg/g), Asahi N760G (Asahi Carbon Co., Ltd., iodine adsorption amount: 27 mg/g), and Seast S (Tokai Carbon Co., Ltd., iodine adsorption amount: 26 mg/g). It will be done.

The amount of carbon black added to the rubber composition according to the present invention is not particularly limited. The amount of carbon black to be blended is 100 parts by weight in total of the ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b) in the rubber composition according to the present invention. Preferably it is 40 parts by weight or more and 100 parts by weight or less.

[Softener]
Softeners include process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, petroleum softeners such as petrolatum; coal tar softeners such as coal tar and coal tar pitch; castor oil, linseed oil, rapeseed oil, Vegetable oil-based softeners such as coconut oil; waxes such as tall oil, sabu, beeswax, carnauba wax, and lanolin; aliphatic dibasic acid esters such as bis(2-ethylhexyl) sebacate; tris(2-ethylhexyl) phosphate, etc. Orthophosphoric acid ester; fatty acids and fatty acid salts such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, calcium stearate, zinc laurate; synthetic polymer substances such as petroleum resin, atactic polypropylene, coumaron indene resin, etc. can give.

[Anti-aging agent]
As the anti-aging agent, known anti-aging agents can be used, including amine-ketone anti-aging agents, phenolic anti-aging agents, imidazole anti-aging agents, amine anti-aging agents and the like. The amount of the anti-aging agent is based on 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b) in the rubber composition of the present invention. , usually 0.1 to 10 parts by weight, preferably 0.5 to 3 parts by weight. Specific examples of commercially available products include Nocrack CD (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., 4,4'-bis(α,α-dimethylbenzyl)diphenylamine) and the like.

[Processing aid]
Processing aids should be selected according to the purpose, and generally well-known higher fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, hydrocarbons, etc. may be used alone or in combination. may be used in combination. The amount of the processing aid is based on the total of 100 parts by weight of the ethylene-α-olefin-nonconjugated polyene copolymer (a) and amorphous chlorinated polyethylene (b) in the rubber composition according to the present invention. , preferably 0.1 to 10 parts by weight. Furthermore, silica, calcium carbonate, finely divided talc, finely divided aluminum silicate, and the like may be used as reinforcing agents.

[Points to remember]
The addition of silicone oil improves the wear resistance of the product due to its friction-reducing effect, and the addition of a plasticizer improves the low-temperature properties of the product. Since the main use is as a conveyance roller that conveys media used in machines, etc., if these bleed and transfer to other parts that come into contact with the roller or the conveyed object, causing contamination, it will be a fatal defect. Whether or not it bleeds depends on the amount of oil added and the composition of the mixture, so it is difficult to specify it uniformly, but as a guide, the SP value of EPDM is about 8, and the SP value of chlorinated polyethylene is about 9. Therefore, it can be said that there is no problem in adding oil etc. with an SP value of 7.5 to 9.5.
Further, although the addition of a plasticizer contributes to improving the low-temperature properties of the product, it is undesirable because there is a concern that the wear resistance and deformation resistance may deteriorate.

<Method for preparing rubber composition>
The rubber composition according to the present invention can be prepared by blending the above components using a known method for preparing a rubber composition. For example, copolymer rubber, chlorinated polyethylene, and various additives are mixed at a predetermined temperature using a known mixer such as a Banbury mixer, a single-screw or twin-screw extruder, a kneader, or an internal mixer such as an intermix. , for example, at a temperature of 80 to 170°C for 3 to 10 minutes, and then, using rolls such as open rolls or a kneader, add a crosslinking agent or the like as necessary at a predetermined temperature, for example, a temperature of 40 to 80°C. It can be prepared by adding and kneading for 5 to 30 minutes.

<Method for manufacturing conveyance rollers>
The rubber composition obtained by kneading can be vulcanized into a desired conveyance roller member using an extrusion molding machine, a compression molding machine, an injection molding machine, a transfer molding machine, or the like. The molding conditions are, for example, 150 to 220°C and 1 to 30 minutes.

In this way, an excellent rubber member that satisfies the following conditions can be obtained.
The wear volume after 1000 rotations in the Taber wear test according to JIS K6264 is 0.039 cm ³ or less.
Compression set according to JIS K6262 is 10% or less.
TR10 in a low temperature elastic recovery test according to JIS K6261 is -22°C or less.
The crosslinking density of the cured product is 5.50×10 ⁻⁴ mol/ml or more.
These rubber members are particularly suitable for manufacturing conveyance rollers.

<Functions of rubber composition components on wear resistance/deformation resistance/low temperature properties>
Although not bound by theory, the effects of the constituent elements of the rubber composition on the above-mentioned properties are thought to be as follows.

[About wear resistance]
There are various types of wear on rubber, such as "abrasive wear,""adhesivewear," and "fatigue wear." In actual usage environments, wear occurs as a combination of these wear types. . The characteristics of each type of wear are as follows.
Abrasive wear: Abrasion that occurs when hard, sharp protrusions scratch the rubber surface with high frictional force.
Adhesive wear: Wear that occurs when the smooth surfaces of abrasive materials and the rubber surface rub against each other, resulting in minute fractures occurring inside the rubber material and transferring to the other surface.
Fatigue wear: Wear caused by fatigue and deterioration caused by repeated deformation when a rubber material slides on a smooth, uneven surface.
In general, chlorinated polyethylene is relatively hard, has high strength, and has a small coefficient of friction, so it is resistant to abrasive wear, and even chlorinated polyethylene alone has excellent wear resistance. In the present invention, it is possible to further improve wear resistance by blending an appropriate amount of ethylene-α-olefin-nonconjugated polyene copolymer rubber therein.
The mechanism is presumed to be that chlorinated polyethylene is less flexible than other types of rubber, and therefore tends to be prone to fatigue wear. By blending an appropriate amount of the relatively flexible copolymer rubber mentioned above, it is possible to impart flexibility while retaining the advantages of chlorinated polyethylene, which is hardness, high strength, and a low coefficient of friction. It is thought that this will not only improve resistance to fatigue wear but also improve wear resistance overall.

[About deformation resistance]
Although chlorinated polyethylene is not particularly bad in deformation resistance, it tends to be slightly inferior compared to other types of organic peroxide crosslinked rubbers. This is because the elasticity of chlorinated polyethylene is weak, so it is difficult to recover even if the load is released after deformation. In the present invention, deformation resistance is improved by blending an appropriate amount of the above-mentioned relatively elastic copolymer rubber.

[About low temperature characteristics]
The low-temperature properties of chlorinated polyethylene tend to be poor compared to other types of rubber. This is due to the crystallinity and intermolecular cohesive force of chlorinated polyethylene. In the present invention, the low-temperature properties are improved by blending an appropriate amount of the above-mentioned copolymer rubber, which has relatively good low-temperature properties.

Next, the content of the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

<Evaluation method>
[Abrasion resistance]
The abrasion resistance in the present invention is evaluated using the JIS K 6264:2018 Taber abrasion test. The test was conducted using a polishing wheel: H-18, an additional force of 4.9 N, and 60 rpm, and the wear volume after 1000 rotations was used as an index of wear resistance.

[Deformation resistance]
The compression set test of JIS K 6262:2018 is used to evaluate the deformation resistance in the present invention. A test is conducted for 24 hours under an environment of 25% compression and 100°C, and the compression set at that time is used as an index of deformation resistance.

[Low temperature characteristics]
The low temperature elastic recovery test (TR test) of JIS K 6261:2018 is used to evaluate the low temperature properties in the present invention. The temperature at which the shrinkage rate is 10% (TR10) is taken as an index of low temperature characteristics.

[Crosslink density]
The rubber composition obtained by kneading was crosslinked using a press molding machine at 170° C. for 10 minutes to obtain a 2 mm thick sheet-like test piece. This sheet-like test piece was punched out into a size of 20 mm x 20 mm, immersed in a toluene solution at 40°C for 72 hours, and then dried at 60°C for 72 hours. The weight of the test piece in air and water before immersion in toluene solution, after immersion (after swelling), and after drying was measured, and the volume of the test piece before immersion V _o (mL) and the volume after swelling V ₁ (mL) were measured. , the volume after drying V ₂ (mL), and the volume of the filler in the rubber member V _F (mL) were determined. Furthermore, the effective network chain concentration v (mol/mL) was determined using the Flory-Rehner equation.

ｖ ： 有効網目鎖濃度 （ｍｏｌ／ｍＬ）
ｖ_Ｒ ： 膨潤したゴム部材中における膨潤した純ゴムの容積（純ゴムの容積＋吸収した溶剤の容積（Ｖ_ｓｏｌ））に対する純ゴムの容積分率であり、下式にて求める。

v: Effective network chain concentration (mol/mL)
v _R : is the volume fraction of pure rubber to the volume of swollen pure rubber in the swollen rubber member (volume of pure rubber + volume of absorbed solvent (V _sol )), and is determined by the following formula.

μ ： ゴム―溶剤間の相互作用定数
Ｖ_ｍ ： 溶剤の分子容（２３℃トルエンのとき、１０６．２９（ｍＬ／ｍｏｌ））

μ: Rubber-solvent interaction constant
V _m : Molecular volume of the solvent (106.29 (mL/mol) when using toluene at 23°C)

Here, the interaction constant μ between rubber and solvent was determined as follows. That is, the SP value of both chlorinated polyethylene and ethylene-propylene-diene copolymer rubber differs slightly depending on the grade, but in the present invention, the SP value of chlorinated polyethylene is 9.2, and the SP value of ethylene-propylene-diene copolymer rubber is 9.2. An SP value of 8.0 was used to calculate the crosslink density. Further, the SP value of toluene was set to 8.9. The solvent interaction constant with toluene for each blend ratio of chlorinated polyethylene and ethylene-propylene-diene copolymer rubber at 25°C is shown below.

<Examples, comparative examples, and reference examples>
[Example 1]
In a 3.5 liter Banbury mixer, 50 parts by weight of EPDM (manufactured by Sumitomo Chemical Co., Ltd., trade name: Esprene 501A), 50 parts by weight of amorphous chlorinated polyethylene (manufactured by Showa Denko K.K., trade name: Elastren 301A), a total of 100 parts by weight. After masticating for 1 minute at a rotational speed of 40 rpm, 1 part by weight of triallyl isocyanate (manufactured by Mitsubishi Chemical Corporation, trade name: Taiku) and carbon black (manufactured by Asahi Carbon Co., Ltd., trade name: Asahi N760G) were added. ) and kneaded for 3 minutes, the mixture was discharged from the Banbury mixer. The discharged mixture was wound around 12-inch rolls with a gap of 5 mm to form a sheet. Next, the above-formed rubber dough was wound around 6-inch rolls with a gap of 4 mm, and 2.4 parts by weight of dialkyl peroxide (manufactured by NOF Corporation, trade name: Percmill D) was kneaded in. After cutting back three times on each side, rounding was performed three times. Finally, it was formed into a sheet. The obtained rubber composition was crosslinked and cured using a press molding machine at 170° C. for 10 minutes to obtain a rubber member.

[Example 2]
A rubber member was obtained in the same manner as in Example 1, except that the amounts of EPDM and amorphous chlorinated polyethylene were changed to 40 parts by weight and 60 parts by weight, respectively.

[Comparative example 1]
A rubber member was obtained in the same manner as in Example 1, except that the amounts of EPDM and amorphous chlorinated polyethylene were changed to 60 parts by weight and 40 parts by weight, respectively.

[Comparative example 2]
A rubber member was obtained in the same manner as in Example 1, except that the amounts of EPDM and amorphous chlorinated polyethylene were changed to 30 parts by weight and 70 parts by weight, respectively.

[Comparative example 3]
A rubber member was obtained in the same manner as in Example 1, except that the amounts of EPDM and amorphous chlorinated polyethylene were changed to 20 parts by weight and 80 parts by weight, respectively.

From the results of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, as the amount of amorphous chlorinated polyethylene added increases, the wear resistance improves, but on the other hand, the low-temperature properties deteriorate. It can be seen that there is a trend. Conversely, the higher the ratio of EPDM, the better the low temperature characteristics. In Comparative Example 1, the amount of chlorinated polyethylene added is too small, resulting in poor wear resistance, while in Comparative Example 2, the amount of chlorinated polyethylene added is too large, resulting in poor deformation resistance and low-temperature properties.
Therefore, in order to achieve a wear volume of 0.039 cm ³ or less at 1000 revolutions measured by the Taber abrasion test, it is appropriate to add 50 parts by weight or more of amorphous chlorinated polyethylene, and -22 In order to achieve TR10 of .degree. C. or lower, it is appropriate that the amount of amorphous chlorinated polyethylene added be less than 70 parts by weight.

[Example 3]
A rubber member was obtained in the same manner as in Example 2 except that the amount of dialkyl peroxide was changed to 2.0 parts by weight.

[Example 4]
A rubber member was obtained in the same manner as in Example 2 except that the amount of dialkyl peroxide was changed to 1.6 parts by weight.

[Comparative example 4]
A rubber member was obtained in the same manner as in Example 2 except that the amount of dialkyl peroxide was changed to 1.2 parts by weight.

From the results of Example 2, Example 3, Example 4, and Comparative Example 4, it can be seen that as the amount of dialkyl peroxide added decreases, the wear resistance improves, but on the other hand, the deformation resistance tends to deteriorate. . In Comparative Example 4, the amount of dialkyl peroxide added was too small, resulting in poor deformation resistance and low-temperature properties. This is because the crosslinking density of the cured product decreases rapidly as the amount of dialkyl peroxide added decreases.
Therefore, in order to achieve a compression set of 10% or less and a TR10 of -22°C or less, it is appropriate to cure the cured product so that the crosslink density is 5.50 x 10 ^-4 mol/ml or more. be.

[Comparative example 5]
A rubber member was obtained in the same manner as in Example 2, except that the amorphous chlorinated polyethylene was changed to crystalline chlorinated polyethylene (manufactured by Showa Denko K.K., trade name: Elastren 352GB-X5). Although this member had a high crosslinking density as a cured product, it was unsatisfactory in terms of wear resistance, deformation resistance, and low-temperature properties.

[Reference example]
The characteristics of a rubber member using hydrogenated nitrile rubber (H-NBR) instead of EPDM are listed as a reference example. It can be seen that the properties of the rubber member of the present invention are equal to or better than those of HNBR.

According to the present invention, there is provided a transport roller that has excellent wear resistance, deformation resistance, and low-temperature properties and is suitable for transporting media used in printing equipment such as printers, automatic teller machines, etc. A rubber member suitable for production as an alternative to hydrogenated nitrile rubber (H-NBR) can be provided.

1 Rotation support shaft 2 Rubber member

Claims (3)

Contains ethylene-α-olefin-nonconjugated polyene copolymer (a), amorphous chlorinated polyethylene (b), and organic peroxide, based on a total of 100 parts by weight of (a) and (b) A conveying roller having a rubber member containing a cured product of a rubber composition in which (b) is 50 parts by weight or more and less than 70 parts by weight and has a crosslink density of 5.50×10 ⁻⁴ mol/ml or more. The conveyance roller according to claim 1, wherein the ethylene-α-olefin-nonconjugated polyene copolymer (a) is ethylene-propylene-diene copolymer rubber (EPDM). The rubber member is
The wear volume at 1000 revolutions measured by the Taber wear test specified in JIS K6264 is 0.039 cm ³ or less,
The conveyance roller according to claim 1 or 2, wherein the compression set measured in accordance with the provisions of JIS K6262 is 10% or less, and the TR10 measured by the low temperature elastic recovery test specified in JIS K6261 is -22°C or less. .