TW201815940A - Rubber composition and transmission belt using same - Google Patents

Abstract

In the rubber composition according to the present invention, cellulose nanofibers and carbon black are dispersed in a rubber component having chloroprene rubber or an ethylene-[alpha]-olefin elastomer as the main component thereof. The cellulose nanofiber content is 1-20 parts by mass with respect to 100 parts by mass of the rubber component, and the carbon black content is 5-60 parts by mass with respect to 100 parts by mass of the rubber component.

Description

   Rubber composition and transmission belt made of the rubber composition   

The invention relates to a rubber composition and a transmission belt made of the rubber composition.

Cellulose nanofibers have attracted attention as a high-strength and chemically stable material. Patent Document 1 discloses that cellulose nanofibers are dispersed and contained in a rubber component such as neoprene to form a rubber composition, and a tire is produced from the rubber composition.

[Prior technical literature]

[Patent Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 2014-088503.

The present invention is a rubber composition in which cellulose nanofiber and carbon black are dispersed in a rubber component mainly composed of neoprene or ethylene-α-olefin elastomer. The content of the nanofibers is 1 part by mass or more and 20 parts by mass or less, and the content of the carbon black is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component.

The present invention is a transmission belt having at least a part of a belt body formed of the rubber composition of the present invention.

B1‧‧‧Single toothed belt

B2‧‧‧Double toothed belt

10‧‧‧Band

11‧‧‧Compression rubber layer

12‧‧‧ Stretched rubber layer

13‧‧‧ Adhesive rubber layer

14‧‧‧core

15‧‧‧ inside reinforcement cloth

16‧‧‧ Outside reinforcement cloth

17‧‧‧ inside teeth

18‧‧‧ Outer teeth

20, 30‧‧‧ belt running test machine

21, 31‧‧‧ Active pulley

22, 32‧‧‧ Passive pulley

FIG. 1A is a perspective view of a part of a single toothed belt.

FIG. 1B is a perspective view of a part of a double toothed belt.

FIG. 2 is a diagram showing a pulley layout of a belt running tester for evaluating crack resistance.

FIG. 3 is a diagram showing a pulley layout of a belt running tester for evaluating abrasion resistance.

Hereinafter, embodiments will be described in detail with reference to the drawings.

The rubber composition of the embodiment disperses cellulose nanofiber (hereinafter referred to as "CNF") and carbon black (hereinafter referred to as "CB") in neoprene (hereinafter referred to as "CR") or ethylene-α -The uncrosslinked rubber composition in the rubber component whose main component is an olefin elastomer is formed by heating and pressing the rubber component to crosslink it. The content of CNF is 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and the content of CB is 5 to 60 parts by mass with respect to 100 parts by mass of the rubber component.

According to the rubber composition of the above embodiment, CNF and CB are dispersed in a rubber component containing CR or ethylene-α-olefin elastomer as a main component, and the content of CNF is 1 mass part or more and 20 masses relative to 100 mass parts of the rubber component. The CB content is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component. Therefore, in the dynamic use state, the dependence of the storage longitudinal elastic coefficient on temperature is small. Therefore, the difference in the magnitude of the deformation caused by the temperature change is small, and the loss tangent is small. As a result, heat generation can be suppressed, and good abrasion resistance can be obtained.

Here, the rubber component is mainly composed of CR or ethylene-α-olefin elastomer. From the viewpoint of reducing the difference in the size of deformation due to temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the CR or ethylene-α-olefin elastomer in rubber components The content is more than 50% by mass, preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. In addition, when the main component of the rubber component is CR, in addition to this, it may contain an ethylene-α-olefin elastomer, a hydrogenated nitrile rubber (H-NBR: Hydrogenated Nitrile Rubber), or styrene butadiene Styrene Butadiene Rubber (SBR) and the like. When the main component of the rubber component is an ethylene-α-olefin elastomer, it may contain CR, hydrogenated nitrile rubber (H-NBR), styrene butadiene rubber (SBR), and the like.

Examples of the CR include G-type sulfur denaturation CR, W-type thiol denaturation CR, A-type high crystalline CR, low viscosity CR, and carboxylated CR. When the main component of the rubber component is CR, it is preferable to include one or two or more CRs as the rubber component. From the standpoint of reducing the difference in the size of deformation due to temperature changes under dynamic use conditions, suppressing heat generation and obtaining excellent abrasion resistance, a sulfur-modified CR is more preferred, and a sulfur-modified CR is particularly preferred As the main component, it is preferably composed only of sulfur-modified CR. From the same viewpoint, it is even more preferable to be composed only of a sulfur-denatured CR.

Examples of ethylene-α-olefin elastomers include ethylene propylene copolymer (EPR), ethylene propylene diene terpolymer (hereinafter referred to as "EPDM"), ethylene octene copolymer, and ethylene butene copolymer. Wait. In the case where the main component of the rubber component is an ethylene-α-olefin elastomer, it is preferred that the ethylene-α-olefin elastomer contains one or two or more of them, more preferably EPDM, and most preferably EPDM as a main component. ingredient.

When the main component of the rubber component is an ethylene-α-olefin elastomer, the ethylene content thereof is preferably 45% by mass or more and 60% by mass or less, and more preferably 50% by mass or more and 55% by mass or less. When the main component of the rubber component is EPDM, examples of the diene component include ethylidene norbornene (ENB), dicyclopentadiene, and 1,4-hexadiene. The diene component is preferably ethylidene norbornene. When the rubber component is EPDM and the diene component is ethylidene norbornene, the content of the ENB is preferably 5.0% by mass or more and 10% by mass or less, and more preferably 7.0% by mass or more and 9.0% by mass or less.

CNF is formed from skeletal components of plant cell walls obtained by pulverizing plant fibers. Examples of CNF raw material wood pulp include wood pulp such as wood, bamboo, rice (straw), potato, sugar cane (bagasse), water grass, and seaweed. Among them, wood pulp is preferred.

Examples of CNFs include: TEMPO (tetramethylpiperazine-N-oxide; oxidized CNF) and mechanically defibrated CNF. It preferably contains one or two or more of the above-mentioned CNFs, preferably contains TEMPO-oxidized CNF, more preferably contains TEMPO-oxidized CNF as the main component, and more preferably contains only TEMPO-oxidized CNF.

The N-oxygen compound is used as a catalyst to allow the co-oxidant to interact with the cellulose contained in the raw wood pulp, and to selectively oxidize the hydroxyl group at the 6th carbon in the cellulose molecule to a carboxyl group. By mechanically miniaturizing it, TEMPO oxidized CNF can be obtained. Examples of the N-oxy compound include: a radical of 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO), 4-acetamido-TEMPO Wait. Examples of the co-oxidant include hypochlorous acid and its salts, hypochlorous acid and its salts, perchloric acid and its salts, hydrogen peroxide, and perorganic acids. The mechanically defibrated CNF is obtained by pulverizing the raw wood pulp using a defibrating device such as a twin-screw kneader, a high-pressure homogenizer, a grinder, and a bead mill.

The fiber diameter of TEMPO-oxidized CNF is, for example, 1 nm to 10 nm, and its distribution is narrow. On the other hand, the fiber diameter of the mechanically defibrated CNF is tens of nm to hundreds of nm, and its distribution is wide. Therefore, TEMPO oxidized CNF and mechanically defibrated CNF can be clearly distinguished by the above-mentioned fiber diameter and its distribution.

The CNF may contain a water-repellent CNF subjected to a Hydrophobic Treatment. Examples of the water-repellent CNF include CNF in which a part or all of the hydroxyl groups of cellulose are replaced with a water-repellent group, and CNF subjected to water-repellent surface treatment with a surface treatment agent. Hydrophobization of CNF for obtaining a part or all of the hydroxyl groups by replacing them with a water-repellent group includes, for example, amination, esterification, alkylation, toluenesulfonation, epoxidation, Aromatic hydrocarbonation and so on. Among them, amination is preferred. Specifically, the aminated water-repellent CNF is a CNF after the carboxyl group of the TEMPO-oxidized CNF is aminated. In order to obtain a CNF surface treatment agent that has been subjected to a water-repellent surface treatment with a surface treatment agent, for example, a silane coupling agent is available.

In the rubber composition of the embodiment, the content (A) of CNF is 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber component. From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation and obtaining excellent abrasion resistance, it is preferably 3 parts by mass or more and 15 parts by mass or less, and more preferably 5 parts by mass. At least 10 parts by mass.

Examples of CB include slotted carbon black; SAF (Super Abrasion Furnace Black), ISAF (Intermediate Super Abrasion Furnace Black), N-339, HAF (High Abrasion Furnace) Black; High Abrasion Furnace Black), N-351, Medium Abrasion Furnace Black; MAF (Fast Extruding Furnace Black); SRF (Semi-Reinforcing Furnace Black; Semi-reinforcing Furnace Black) Furnace Black), GPF (General Purpose Furnace Black), ECF, N-234 and other furnace blacks; FT (Fine Thermal Black; Fine Thermal Black), MT (Medium Thermal Black; Medium Thermal Black) Isothermally cracked carbon black; and acetylene black. The CB preferably contains one or two or more of them; more preferably, it contains FEF; particularly preferably, it contains FEF as a main component; and most preferably, it contains only FEF.

In the rubber composition of the embodiment, the content (B) of the CB is 5 mass parts or more and 60 mass parts or less based on 100 mass parts of the rubber component. From the viewpoint of reducing the difference in the size of the deformation caused by the temperature change under dynamic use conditions, suppressing heat generation and obtaining excellent abrasion resistance, it is preferably 10 parts by mass or more and 40 parts by mass or less, more preferably 10 parts by mass. At least 30 parts by mass. The rubber composition according to the embodiment is preferably 100 parts by mass with respect to the rubber component, and the sum (A + B) of the content of the CNF content (A) and the content of the CB (B) is 15 parts by mass or more and 70 parts by mass. 60 parts by mass or less; more preferably 40 parts by mass or less.

In the rubber composition of the embodiment, the ratio (A / B) of the content (A) of CNF to the content (B) of CB is preferably 0.050 or more and 2.0 or less; more preferably 1.0 or less; particularly preferably 0.5 or less. From the viewpoint of reducing the difference in the size of the deformation caused by the temperature change under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is more preferable than the rubber component 100 In terms of parts by mass, the content (A) of CNF is less than the content (B) of CB.

The short fibers may be dispersed and contained in the rubber composition of the embodiment. Examples of short fibers include para aromatic polyamide short fibers, meta aromatic polyamide short fibers, nylon 6 short fibers, nylon 6,6 short fibers, nylon 4,6 short fibers, Polyethylene terephthalate short fibers, polyethylene naphthalate short fibers, and the like. It is preferable to contain one kind, or two or more kinds of short fibers, and it is more preferable to contain para-type aromatic polyamine short fibers. It is preferable that para-type aromatic polyamido staple fiber is contained as a main component; more preferably, para-type aromatic polyamido staple fiber is only contained.

Examples of para-type aromatic polyamido staple fibers include: polyparaphenylene terephthalamide staple fibers (e.g., Kevlar produced by Du Pont Corporation of the United States, Teijin Corporation of Japan) Twaron) and short fibers of Copolyparaphenylene-3,4'-oxydiphenylene terephthalamide (e.g. technora from Teijin Corporation) ). It is preferable that the para-type aromatic polyamido staple fiber contains one or two of them. More preferred are short fibers containing p-xylylenediamine-3,4'-diphenylether. As the main component, xylylenediamine short fiber is preferably a short fiber containing only p-xylylenediamine-3,4'-diphenyl ether p-xylylenediamine.

The fiber length of the short fibers is preferably 0.50 mm to 5.0 mm, and more preferably 1.0 mm to 3.0 mm. The fiber diameter of the short fibers is preferably 5.0 μm or more and 70 μm or less, and more preferably 10 μm or more and 50 μm or less.

From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is 100 parts by mass relative to the rubber component. The content of the short fibers (C) is preferably 3 parts by mass or more and 25 parts by mass or less; more preferably 5 parts by mass or more and 20 parts by mass or less. From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is 100 parts by mass relative to the rubber component. The sum (A + C) of the content (A) of the CNF and the content (C) of the short fibers is preferably 15 parts by mass or more and 40 parts by mass or less; more preferably 25 parts by mass or less. From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is 100 parts by mass relative to the rubber component. The sum (A + B + C) of the content of CNF (A), the content of CB (B) and the content of short fibers (C) is preferably 30 parts by mass or more and 90 parts by mass or less; more preferably 60 parts by mass or less ; Particularly preferably 40 parts by mass or less.

From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is 100 parts by mass relative to the rubber component. The ratio (A / C) of the content (A) of the CNF to the content (C) of the short fibers is preferably 0.050 or more and 1.3 or less, and more preferably 0.40 or less. From the viewpoint of reducing the difference in the size of deformation caused by temperature changes under dynamic use conditions, suppressing heat generation, and obtaining excellent abrasion resistance, the rubber composition of the embodiment is 100 parts by mass relative to the rubber component. Preferably, the content (A) of CNF is less than the content () of short fibers.

A CR or an ethylene-α-olefin elastomer crosslinking agent is added to the uncrosslinked rubber composition forming the rubber composition of the embodiment. Examples of the CR crosslinking agent include metal oxides such as zinc oxide and magnesium oxide. It is preferred that the crosslinking agent uses both zinc oxide and magnesium oxide. The amount of zinc oxide added is preferably 3 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the rubber component; more preferably 4 parts by mass or more and 6 parts by mass or less. The addition amount of magnesium oxide is preferably 3 parts by mass or more and 7 parts by mass or less with respect to 100 parts by mass of the rubber component; more preferably 4 parts by mass or more and 6 parts by mass or less. Examples of the crosslinking agent of the ethylene-α-olefin elastomer include organic peroxides and sulfur. Both organic peroxides can be used as crosslinking agents, sulfur can also be used as crosslinking agents, and organic peroxides and sulfur can be used as crosslinking agents simultaneously. The addition amount of the organic peroxide or sulfur is, for example, 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the rubber component.

The rubber composition of the embodiment may contain rubber additives such as a plasticizer, a processing aid, and a vulcanization accelerator in addition to the rubber composition.

The rubber hardness of the rubber composition according to the embodiment measured in accordance with the Japanese Industrial Standard JIS K6253: 2012 with an A-type rubber hardness meter is preferably A80 or more and A95 or less.

The tensile strength of the rubber composition according to the embodiment measured in accordance with Japanese Industrial Standard JIS K6251: 2010 in the grain direction is preferably 20.0 MPa to 35.0 MPa; more preferably 25.0 MPa to 30.0 MPa. The elongation at break of the rubber composition according to the embodiment measured in accordance with Japanese Industrial Standard JISK6251: 2010 in the grain direction is preferably 10% or more and 40% or less; more preferably 15% or more and 30% or less.

The storage longitudinal elastic coefficient (E ') of the rubber composition of the embodiment measured in accordance with the Japanese Industrial Standard JISK6394: 2007 at a dynamic distortion of 1.0% and a frequency of 10 Hz at 25 ° C and in the reverse grain direction is preferred. 10.0 MPa to 70.0 MPa; more preferably 15.0 MPa to 40.0 MPa. The storage longitudinal elastic coefficient at 100 ° C. in the reverse grain direction is preferably 10.0 MPa to 55.0 MPa; more preferably 13.0 MPa to 25.0 MPa. The ratio of the storage longitudinal elastic coefficient at 100 ° C and inverse grain direction to the storage longitudinal elastic coefficient at 25 ° C and in grain direction is preferably 0.70 or more; more preferably 0.80 or more; particularly preferably 0.90 or more.

The loss tangent (tan δ) of the rubber composition of the embodiment measured at 25 ° C. in the reverse grain direction according to the Japanese Industrial Standard JISK6394: 2007 and with dynamic distortion of 1.0% and a frequency of 10 Hz, preferably 0.17 or less ; More preferably 0.10 or less. The loss tangent at 100 ° C. in the reverse grain direction is preferably 0.13 or less; more preferably 0.080 or less.

In the case of using CR as the main component of the rubber component, CNF is mixed into CR latex and the solvent is removed to prepare a master batch in which CNF is dispersed in CR, and then added to the master batch The CB-containing rubber additive is kneaded to obtain an uncrosslinked rubber composition, and the uncrosslinked rubber composition is heated and pressurized to crosslink the rubber components, thereby obtaining the rubber composition of the embodiment having the above structure. Alternatively, when CR is used as the main component of the rubber component, CNF is mixed into the CR latex and the solvent is removed to prepare a masterbatch in which CNF is dispersed in the CR. Then, rubber components such as CR are mixed with the masterbatch. After being diluted, a rubber additive containing CB is added and kneaded to obtain an uncrosslinked rubber composition. The uncrosslinked rubber composition is heated and pressurized to crosslink the rubber components, and the embodiment having the above structure can be obtained. Rubber composition. When ethylene-α-olefin elastomer is used as the main component of the rubber component, the water-repellent CNF is dispersed in a solvent such as toluene to form a dispersion, and the ethylene-α-olefin elastomer is dissolved in a solvent such as toluene. A solution is formed by mixing the dispersion and the solution, and the solvent is removed to prepare a masterbatch in which CNF is dispersed in the ethylene-α-olefin elastomer, and the masterbatch may be used.

Because the rubber composition of the embodiment can reduce the difference in the size of deformation caused by temperature changes under dynamic use conditions and suppress heat generation, the rubber composition of the embodiment is very suitable as a material for forming a transmission belt, and is particularly suitable. It is used as a material forming at least a part of the transmission belt body.

FIG. 1A shows a single cogged V belt B1 as an example of a transmission belt. The single-toothed belt B1 is used, for example, as a speed change belt for small-sized speed queda and agricultural machinery.

The single-toothed belt B1 has a rubber belt body 10, a compression rubber layer 11 on the inner peripheral side of the belt, a tensile rubber layer 12 on the outer peripheral side of the belt, and an adhesive rubber layer 13 therebetween. The band body 10 and the cross section of the rubber band body 10 are trapezoidal. A core wire 14 is embedded in an intermediate portion in the thickness direction of the adhesive rubber layer 13, and the core wire 14 is provided so that the core wire 14 forms a spiral having a pitch in a bandwidth direction. The inner reinforcing cloth 15 is provided in contact with the surface of the inner peripheral surface of the tape constituting the compression rubber layer 11; the outer reinforcing cloth 16 is provided in contact with the surface of the outer peripheral surface of the band constituting the stretch rubber layer 12. The inner teeth 17 are formed on the inner circumferential side of the belt along the belt length direction at a constant pitch. On the other hand, the belt outer peripheral side is configured as a very flat belt back surface.

FIG. 1B shows another example of a transmission belt, namely a double cogged V belt (B2). The double-toothed belt B2 is used, for example, as a speed change belt for a large buggy or a large Scooter.

The double-toothed belt B2, like the single-toothed belt B1, has a belt body 10 composed of a compression rubber layer 11, a tensile rubber layer 12, and an adhesive rubber layer 13, a core wire 14 embedded in the adhesive rubber layer 13, and an adhesive layer. An inner reinforcing cloth 15 provided on the inner peripheral surface of the belt and an outer reinforcing cloth 16 provided on the outer peripheral surface of the belt. In addition, inner teeth 17 and outer teeth 18 are formed on the belt inner peripheral side and the belt outer peripheral side with a certain pitch in the belt length direction, respectively.

In the single-toothed belt B1 and the double-toothed belt B2, it is preferable that at least a part of the belt body 10 is formed of the rubber composition of the embodiment, and in particular, the compression rubber layer 11 is formed of the rubber composition of the embodiment.

The single-toothed belt B1 and the double-toothed belt B2 used for variable-speed applications are severely bent while changing the winding diameter around the pulley. At this time, bending will cause heat generation. If the deformation of the belt increases with increasing temperature, it will be difficult to maintain a stable shifting operation. Moreover, if there is a lot of heat generation, the heat generation will become an energy loss, resulting in power transmission. Reduced efficiency. However, the single-toothed belt B1 and the double-toothed belt B2 made of the rubber composition of the embodiment can have a small difference in the size of the deformation caused by the temperature change under dynamic use conditions such as bending, so they can be used. It maintains a stable shift operation and suppresses heat generation, so that the reduction in power transmission efficiency can be suppressed to a low level. Friction transmission belts such as the single-toothed belt B1 and the double-toothed belt B2 are required to have high abrasion resistance, and excellent wear resistance can be obtained by using the rubber composition of the embodiment.

It should be noted that, in the above-mentioned embodiment, the transmission belt formed of the rubber composition of the embodiment as at least a part of the belt body shows a single-toothed belt B1 and a double-toothed belt B2. However, it is not limited to this, and a flat belt, a V belt, a V ribbed belt, a toothed belt, or the like may be used. In addition, the rubber composition of the embodiment is not limited to being used for manufacturing a transmission belt. For example, the rubber composition can also be used for manufacturing rubber products such as tires and hoses.

[Example]

(Rubber composition)

The rubber compositions in Examples 1 to 15 and Comparative Examples 1 to 3 were prepared. Various ingredients and their content ratios are shown in Tables 1A and 1B.

<Example 1>

The sulfur-modified CR latex is 100 parts by mass of sulfur-modified CR latex (manufactured by TOSOH Corporation), which is a rubber component in the sulfur-modified CR latex. By mixing with TEMPO-oxidized CNF and removing the solvent, a masterbatch in which TEMPO-oxidized CNF is dispersed in sulfur-modified CR is prepared. Then, to the master batch, 100 parts by mass of sulfur-modified CR, which is a rubber component, 22 parts by mass of FEF (Seast SO Tokai Carbon Co., Ltd.) and 16 parts by mass of para-type aromatic polyamido staple fibers were added (Manufactured by Technora Teijin Co., Ltd., fiber length is 3.0 mm, fiber diameter is about 12 μm), plastic puppet with a mass part of 5, stearic acid with a mass part of 1, zinc oxide with a mass part of 5, and 5 parts by mass The magnesium oxide was mixed and kneaded to obtain an uncrosslinked rubber composition. This uncrosslinked rubber composition was heated and pressed to crosslink the rubber components to obtain a crosslinked rubber composition. This rubber composition was designated as Example 1.

<Example 2>

A rubber composition similar to Example 1 was defined as Example 2 except that the amount of TEMPO-oxidized CNF added was 1 part by mass based on 100 parts by mass of the rubber component.

<Example 3>

A rubber composition similar to Example 1 was set as Example 3 except that the amount of TEMPO-oxidized CNF added was 5 parts by mass based on 100 parts by mass of the rubber component.

<Example 4>

A rubber composition similar to Example 1 was set as Example 4 except that the amount of TEMPO-oxidized CNF added was 20 parts by mass based on 100 parts by mass of the rubber component.

<Example 5>

A rubber composition similar to that of Example 1 except that the sulfur-modified CR latex (B-30 Japan TOSOH Co., Ltd.) was used in place of the sulfur-modified CR latex was designated as Example 5.

<Example 6>

A rubber composition similar to Example 1 was defined as Example 6 except that the amount of FEF added was 5 parts by mass relative to 100 parts by mass of the rubber component.

<Example 7>

A rubber composition similar to Example 1 was set as Example 7 except that the amount of FEF added was 10 parts by mass relative to 100 parts by mass of the rubber component.

<Example 8>

A rubber composition similar to Example 1 was set as Example 8 except that the amount of FEF added was 40 parts by mass relative to 100 parts by mass of the rubber component.

<Example 9>

A rubber composition similar to that of Example 1 was defined as Example 9 except that the amount of FEF to be added was 60 parts by weight based on 100 parts by mass of the rubber component.

<Example 10>

Except that ISAF (SEAST 600 Tokai Carbon Co., Ltd.) was added instead of FEF, the rubber composition was the same as that of Example 1 as Example 10.

<Example 11>

Except that SAF (SEAST 9 Tokai Carbon Co., Ltd.) was added instead of FEF, the rubber composition was the same as that of Example 1 as Example 10.

<Example 12>

Except that a mechanically defibrated CNF (fiber diameter of several tens to hundreds of nm) was added instead of TEMPO to oxidize the CNF, the rubber composition was the same as that of Example 1 as Example 12.

<Example 13>

-TEMPO catalyst oxidation-

After fully washing the soft bleaching craft pulp with hydrochloric acid and ion-exchanged water, mix the soft bleaching craft pulp with ion-exchanged water, and then add 2, 2, 6, 6-tetramethyl to it Hexahydropyridine-1-oxy radical (TEMPO) and NaBr were stirred. Next, an aqueous sodium hypochlorite solution was added to the wood pulp mixed liquid, the pH was adjusted, and stirring was continued. The obtained wood pulp mixture was filtered, and the filtrate was sufficiently washed with ion-exchanged water. By this TEMPO catalyst oxidation treatment, the hydroxyl group at the C6 position in cellulose molecules contained in the wood pulp is selectively oxidized to a carboxyl group.

-Protonation-

The obtained TEMPO catalyst-oxidized wood pulp was mixed with ion-exchanged water and stirred. Next, hydrochloric acid was dropped into the wood pulp mixture. After that, the obtained wood pulp mixed liquid was filtered, and the filtrate was sufficiently washed with ion-exchanged water. By this protonation treatment, the carboxyl group introduced by the oxidation of the TEMPO catalyst is protonated.

-Amination-

The obtained protonated wood pulp was mixed with ion-exchanged water and stirred. Next, an aqueous solution of Hexadecyltrimethylammonium hydroxide was dropped into the wood pulp mixture. Then, the obtained wood pulp mixture was filtered, and the filtrate was sufficiently washed with ion-exchanged water, and then the filtrate was dried. By this amination treatment, a hexadecyltrimethylamine hydroxide is used to neutralize the protonated carboxyl group introduced by the TEMPO catalyst oxidation and obtained by the protonation treatment to form a salt. That is, the above-mentioned wood pulp mixed liquid is aminated with a tetraamine compound, cetyltrimethylamine hydroxide.

-Defibration-

The dried wood pulp was added to toluene and dispersed with a bead mill, and then the wood pulp contained in the obtained dispersion was defibrated with a jet mill (manufactured by Toko Corporation). By the defibrating treatment, a dispersion liquid was prepared in which tetrahydrated compound CNF (fiber diameter: 3 nm to 4 nm) hydrolyzed with tetraamine compound was dispersed in toluene with cetyltrimethylamine hydroxide.

The dispersion obtained by dispersing the obtained water-repellent CNF in toluene was mixed with a toluene solution of EPDM (produced by EP33 JSR, ethylene content: 52% by mass, ENB content: 8.1% by mass) so as to be relative to the rubber component. That is, 100 parts by mass of EPDM, the content of water-repellent CNF is 5 parts by mass, and then toluene is removed to prepare a masterbatch in which water-repellent CNF is dispersed in EPDM. Then, to this master batch, 100 parts by mass of EPDM, which is a rubber component, 50 parts by mass of FEF, 16 parts by mass of para-type aromatic polyamido staple fibers, 5 parts by mass of a plasticizer, and 1 part by mass of stearin were added. Acid, 5 parts by mass of zinc oxide, 10 parts by mass of a co-crosslinking agent (Hi-Cross M produced by Seiko Chemical Co., Ltd.), 6 parts by mass of an organic peroxide cross-linking agent (PERCUMYL D Japan Oil Co., Ltd.) and Kneading is performed to obtain an uncrosslinked rubber composition, and the uncrosslinked rubber composition is heated and pressurized to form a rubber composition in which the rubber components are crosslinked. The rubber composition is defined as an example. 13.

<Example 14>

A rubber composition similar to that of Example 13 was set as Example 14 except that the addition amount of the water-repellent CNF and the addition amount of FEF were 100 parts by mass and 35 parts by mass with respect to 100 parts by mass of the rubber component, respectively. .

<Example 15>

The rubber composition was the same as that of Example 13 except that the amount of water-repellent CNF and the amount of FEF added were 20 parts by mass and 15 parts by mass with respect to 100 parts by mass of the rubber component. .

(Comparative example 1)

In addition to replacing the sulfur-modified CR latex with hydrogenated nitrile rubber latex (ZLX-B Japan Zeon Co., Ltd.), and adding 3 parts by mass of an organic peroxide crosslinking agent to 100 parts by mass of the rubber component, The rubber composition which was the same as that of Example 1 was designated as Comparative Example 1.

(Comparative example 2)

A styrene butadiene rubber latex (produced by J-9049 JSR Co., Ltd.) will be used in place of the sulfur-modified CR latex, and 0.3 parts by mass of an organic peroxide crosslinking agent will be added to 100 parts by mass of the rubber component. The rubber composition which is the same as that in Example 1 is referred to as Comparative Example 2.

(Comparative example 3)

A rubber composition similar to that of Example 1 except that FEF was not added was defined as Comparative Example 3.

(experiment method)

<Rubber hardness>

The rubber hardness in Examples 1 to 15 and Comparative Examples 1 to 3 was measured in accordance with Japanese Industrial Standard JIS K6253: 2012 using an A-type rubber hardness tester.

<Tensile properties>

In accordance with Japanese Industrial Standard JIS K6251: 2010, the tensile strength and elongation at break in the grain direction were measured for Examples 1 to 15 and Comparative Examples 1 to 3, respectively.

<Viscoelastic properties>

In accordance with Japanese Industrial Standard JIS K6394: 2007, the storage longitudinal elastic coefficient (E ') and loss tangent (tanδ) in the inverse grain direction at 25 ° C and 100 ° C were measured for Examples 1 to 15 and Comparative Examples 1 to 3, respectively. ). The measurement conditions are 1.0% dynamic distortion and 10Hz frequency. The ratio of the storage longitudinal elastic coefficient at 100 ° C to the storage longitudinal elastic coefficient at 25 ° C was calculated.

<Characteristics of belt>

Using the rubber composition in Examples 1 to 15 and Comparative Examples 1 to 3, a single-toothed belt B1 having the same structure as the belt shown in FIG. 1A was produced. At this time, a compression rubber layer of the belt body was formed, and Ensure that the direction of the inverse texture is the length of the belt.

-Crack resistance-

FIG. 2 shows a belt running tester 20 for evaluating crack resistance.

The belt running tester 20 includes a driving pulley 21 having a wheel diameter of φ40 mm and a passive pulley 22 provided on the right side of the driving pulley 21 and having a wheel diameter of 40 mm. The passive pulley 22 is provided so as to be movable left and right so as to be able to withstand an axial load (fixed load DW).

The single-toothed belt B1 formed in each of Examples 1 to 15 and Comparative Examples 1 to 3 was wound between the active pulley 21 and the passive pulley 22 of the belt running tester 20, and faced to the right. The passive pulley 22 applies an axial load of 600 N to apply a belt tension, and the active pulley 21 is rotated at a speed of 3000 rpm at an ambient temperature of 100 ° C. to allow the belt to run. The belt was stopped periodically, and it was confirmed by visual inspection whether cracks occurred. The running time of the belt in which cracking was confirmed was defined as the cracking resistance life. It should be noted that the longest belt running time is 240 hours.

-Abrasion resistance, temperature of the belt-

FIG. 3 shows a belt running tester 30 for evaluating abrasion resistance.

The belt running tester 30 includes a driving pulley 31 having a wheel diameter of φ60 mm and a passive pulley 32 provided on the left side of the driving pulley 31 and having a belt diameter of 100 mm. The passive pulley 32 is provided so as to be movable left and right so as to be able to withstand an axial load (fixed load DW).

After measuring the mass of the single-toothed belt B1 formed in each of Examples 1 to 15, and Comparative Examples 1 to 3, the single-toothed belt B1 was wound around a driving pulley of a belt running tester 30. Between 31 and the passive pulley 32, an axial load of 700 N is applied to the passive pulley 32 toward the left side to apply belt tension, and 10 N is applied to the passive pulley 32. With a rotating load of m, the active pulley 31 was rotated at a rotation speed of 4200 rpm at an ambient temperature of 50 ° C, and the belt was allowed to run for 200 hours. A non-contact thermometer was used to record the maximum temperature on the back of the belt when the belt was running, and this was used as the temperature of the belt. After the belt was run, the quality of the belt was measured again. Subtract the mass of the belt after the belt runs from the mass of the belt before the belt runs, find the quality difference, and divide the mass of the belt before the belt runs to calculate the percentage as the belt wear rate. Let the belt wear rate of Example 1 be It was set to 100 and the abrasion resistance index was calculated.

(test results)

Tables 2A and 2B show the test results.

[Table 2A]     

According to Table 2A and Table 2B, in Examples 1 to 15 in which a predetermined amount of CNF and FEF are added to CR or EPDM, the storage longitudinal elastic coefficient at 100 ° C. in the reverse texture direction is 25 compared to the reverse texture direction. The ratio of storage longitudinal elastic coefficient at ℃ is above 0.75, which is high, so the dependence of storage longitudinal elastic coefficient on temperature is small. Therefore, it can be predicted in advance that the difference in the magnitude of the deformation caused by the temperature change is small. Because the loss tangent at 25 ° C is below 0.16 and the loss tangent at 100 ° C is below 0.13, which is low, it can be predicted in advance that there will be less heat generation under dynamic use conditions. From the characteristics of the belt, it can be known that the anti-cracking life is 86.4 hours or more, is long, and the wear resistance index is 100 or less except for Examples 6, 7, and 11 to 15, which is low. Moreover, when the belt is running, the temperature of the belt is lower than 100 ° C, which is low. Therefore, it can be seen that there is less fever.

On the other hand, in Comparative Example 1 using a hydrogenated nitrile rubber as a rubber component and Comparative Example 2 using a styrene butadiene rubber as a rubber component, the storage longitudinal elastic coefficient at 100 ° C. in the reverse texture direction is relative to the reverse texture The ratios of the storage longitudinal elastic coefficients at 25 ° C in the direction were all 0.60, which was low. Therefore, the dependence of storage longitudinal elastic coefficient on temperature is large. It can be predicted in advance that there is a large difference in the magnitude of the deformation caused by the temperature change. Moreover, since the loss tangents at 25 ° C are all 0.18, and the loss tangents at 100 ° C are 0.14 and 0.15 respectively, which are relatively high, it can be predicted in advance that there will be more heat generation under dynamic use conditions. With regard to the characteristics of the belt, the anti-cracking life is 42 hours and 31 hours, respectively, which is short, and the abrasion wear index is 103 and 195, which are high. Moreover, when the belt is running, the belt temperatures are 102 ° C and 104 ° C, respectively, which are relatively high. Therefore, it was found that there was a lot of fever.

For Comparative Example 3 without the addition of FEF, the ratio of the storage longitudinal elastic coefficient at 100 ° C in the inverse grain direction to the storage longitudinal elastic coefficient at 25 ° C in the inverse grain direction is 0.71, which is higher than that of Examples 1 to 15 Slightly lower. The loss tangents at 25 ° C and 100 ° C are 0.069 and 0.049, respectively, which are lower. Therefore, it can be predicted in advance that there is less heat generation under dynamic use conditions. Moreover, from the characteristics of the belt, the anti-cracking life is 82.4 hours, which is slightly shorter than that of Examples 1 to 15. When the belt is running, the belt temperature is 84 ° C, which is at the same level as that of Examples 1 to 15. . However, it can be seen that the abrasion resistance index is 205, which is very high.

(Industrial availability)

The present invention is useful in the technical field of a rubber composition and a transmission belt made of the rubber composition.

Claims (15)

    A rubber composition in which cellulose nanofibers and carbon black are dispersed in a rubber component mainly composed of neoprene or ethylene-α-olefin elastomer to form the rubber composition; 100 parts by mass of the rubber component, The content of the cellulose nanofiber is 1 part by mass or more and 20 parts by mass or less, and the content of the carbon black is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the rubber component.         The rubber composition according to claim 1, wherein the main component of the rubber component is sulfur-modified neoprene.         The rubber composition according to claim 1, wherein the main component of the rubber component is an ethylene propylene diene copolymer.         The rubber composition according to claim 1, wherein the cellulose nanofibers contain tetramethylpiperazine-N-oxide-oxidized cellulose nanofibers.         The rubber composition according to claim 1, wherein the carbon black contains rapid-extrusion black.         The rubber composition according to claim 1, wherein a sum of a content of the cellulose nanofiber and a content of the carbon black is 15 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the rubber component.         The rubber composition according to claim 1, wherein the ratio of the content of the cellulose nanofibers to the content of the carbon black is 0.050 or more and 2.0 or less.         The rubber composition according to claim 1, wherein the content of the cellulose nanofiber is smaller than the content of the carbon black.         The rubber composition according to claim 1, further comprising short fibers dispersed therein.         The rubber composition according to claim 9, wherein the short fibers include para-type aromatic polyamidamine short fibers.         The rubber composition according to claim 9, wherein the sum of the content of the cellulose nanofibers and the content of the short fibers with respect to 100 parts by mass of the rubber component is 15 parts by mass or more and 40 parts by mass or less.         The rubber composition according to claim 9, wherein the sum of the content of the cellulose nanofiber, the content of the carbon black, and the content of the short fiber is 30 parts by mass or more and 90 parts by mass relative to 100 parts by mass of the rubber component. The following.         The rubber composition according to claim 9, wherein the ratio of the content of the cellulose nanofibers to the content of the short fibers is 0.050 to 1.3.         The rubber composition according to claim 9, wherein the content of the cellulose nanofibers is smaller than the content of the short fibers.         A transmission belt having at least a part of a belt body made of the rubber composition according to any one of claims 1 to 14.