JPWO2007018148A1 - Rubber composition for transmission belt and transmission belt - Google Patents

Abstract

Provided is a rubber composition for a transmission belt capable of producing a transmission belt having excellent conductivity, conductivity maintaining property after running, bending fatigue resistance and wear resistance. Conductive carbon having a DBP oil absorption of 300 cm 3/100 g or more and furnace carbon black having a nitrogen adsorption specific surface area of 40 to 100 m 2 / g or more and a DBP oil absorption of 100 to 160 cm 3/100 g or less with respect to 100 parts by mass of the rubber: 70 ≦ 8X + Y ≦ 200, 2 ≦ X ≦ 20, and 0 ≦ Y ≦ 90 [wherein X represents the content (parts by mass) of the conductive carbon. Y represents the content (parts by mass) of the furnace carbon black. ] A rubber composition for a transmission belt that is blended within a range satisfying the above.

Description

The present invention relates to a rubber composition for a transmission belt and a transmission belt.

Conventionally, transmission belts such as V-belts and V-ribbed belts have been widely used, and such transmission belts are widely used as, for example, transmission belts for driving auxiliary machinery when driving automotive auxiliary machinery. This auxiliary machine drive transmission belt may cause adverse effects on electronic devices or cause an electric shock accident due to electric leakage due to static electricity generated between pulleys (insulators such as resin and aluminum).

For this reason, in recent years, there has been a demand for lowering the electrical resistance of the accessory driving power transmission belt. Specifically, when a voltage of 500 V is applied and the electrical resistance is measured over a distance of 100 mm, the value is 200 MΩ or less. It is desired to provide a product having properties such as being. Therefore, various techniques for imparting conductivity to the transmission belt have been developed.

Patent Document 1 discloses a V-ribbed belt in which an outer canvas rubber composite composed of a back rubber layer formed of a rubber composition mainly composed of CR polymer, hard carbon, and conductive carbon is coated. Patent Document 2 discloses a transmission belt in which a canvas for a transmission belt mixed and mixed with carbon fiber is bonded to the surface of a belt body.

Further, Patent Document 3 has a canvas layer located on the back surface made of canvas and rubber adhered thereto, and conductive material such as conductive carbon black, ketjen black, metal powder or carbon fiber is contained in the rubber. A V-ribbed belt in which conductivity is imparted to the canvas layer by dispersing is disclosed. These techniques prevent the above-described problems from occurring by imparting conductivity to the back side of the belt.

However, even if the power transmission belt having such a configuration can impart conductivity to a new belt, the conductivity of the belt is lost when the belt is attached to the engine and traveled. Therefore, in recent years, it has become necessary to maintain the conductivity of the belt after traveling, but it is difficult to meet such a requirement at present. In addition, it is also required to impart conductivity to the bottom rubber layer surface, and it is also desired to provide a rubber compounding technique in which the electrical resistance is less increased by running the belt.
JP-A-6-323368 Japanese Patent Laid-Open No. 10-38033 JP-A-10-184812

The present invention provides a rubber composition for a transmission belt capable of producing a transmission belt having excellent conductivity, conductivity maintaining property after running, bending fatigue resistance and wear resistance in view of the above-mentioned present situation. With the goal.

The present invention is, with respect to 100 parts by mass of the rubber, DBP oil absorption of 300 cm ³ / and more conductive carbon 100 g, the nitrogen adsorption specific surface area 40 to 100 m ² / g, a DBP oil absorption of 100~160cm ³ / 100g furnace carbon black And the following formula:
70 ≦ 8X + Y ≦ 200 and 2 ≦ X ≦ 20 and 0 ≦ Y ≦ 90
[In formula, X represents content (mass part) of the said conductive carbon. Y represents content (mass part) of the said furnace carbon black. ] A rubber composition for a power transmission belt, which is blended within a range satisfying the above.

The rubber is preferably an ethylene-α-olefin elastomer.
The ethylene-α monoolefin elastomer preferably has a Mooney viscosity ML _{1 + 4} (125 ° C.) of 40 to 70.

The ethylene-α-olefin elastomer preferably has an ethylene content of 50 to 70%.
The process oil is preferably blended in an amount of 30 parts by mass or less with respect to 100 parts by mass of the rubber.

The present invention is also a transmission belt obtained by using the above-described rubber composition for a transmission belt.
The transmission belt has the following dynamic viscoelastic properties of the vulcanized rubber constituting the transmission belt: tensile mode, frequency 10 Hz, static load 3 kgf / cm ² , dynamic strain 0.6%, temperature 25 ° C. The tan δ in the belt longitudinal direction is preferably 0.25 or less.
The power transmission belt according to claim 6.

According to JIS K6229, the above transmission belt is based on JIS K6229 as the dynamic viscoelastic property of the vulcanized rubber constituting the transmission belt, under the conditions that the extraction solvent is n-hexane, the test method is method A, and the extraction device is type 1. The solvent extraction amount is preferably 14% or less.
The transmission belt is preferably a V-ribbed belt, a double-ribbed belt, or a flat belt.
Hereinafter, the present invention will be described in detail.

Rubber composition for a transmission belt of the present invention is a rubber composition used to produce the transmission belt, the rubber 100 parts by weight, and the DBP oil absorption of 300 cm ^3/100 g or more conductive carbon, nitrogen adsorption specific surface area 40 to 100 m ² / g, and a furnace carbon black having a DBP oil absorption of ^{100~160cm 3 / 100g, 70 ≦ 8X} + Y ≦ 200 and,, 2 ≦ X ≦ 20 and 0 ≦ Y ≦ 90 wherein, X represents the content (parts by mass) of the conductive carbon. Y represents content (mass part) of the said furnace carbon black. ] Within a range satisfying the above. For this reason, by using the rubber composition for a transmission belt, it is possible to obtain a transmission belt that is excellent in all of the characteristics of conductivity, conductivity maintaining characteristics after running, bending fatigue resistance, and wear resistance. Here, in this specification, the term “conductive” means that the electrical resistance is measured at a distance of 100 mm when a voltage of 500 V is applied to the transmission belt, and the value is 10 MΩ or less.

That is, the important finding found in the present invention is that when a transmission belt is produced using a rubber composition containing the conductive carbon black and the furnace carbon black within the range satisfying the above formula, Thus, it is possible to obtain a transmission belt having excellent conductivity, conductivity maintaining property after running, and excellent bending fatigue resistance and wear resistance.

Therefore, the transmission belt obtained by using the rubber composition for a transmission belt of the present invention can suppress an increase in electric resistance due to belt running even after running, and can maintain excellent conductivity. is there. Further, it can exhibit a long life during belt running and has excellent bending fatigue resistance. Furthermore, the amount of wear during belt running can be reduced. Although it is extremely difficult to obtain such excellent characteristics at the same time, it can be obtained at the same time by using the rubber composition for a transmission belt of the present invention. In particular, in the present invention, conductivity can be maintained even when subjected to dynamic stimulation such as bending and frictional wear due to belt running, and at the same time, the bending fatigue resistance and wear resistance required for the transmission belt are the same as the conventional non-conductive specifications. It has extremely excellent characteristics in that it does not change.

In general, when a large amount of conductive carbon is added, excellent conductivity is obtained and the maintenance of conductivity is also good, but when this method is applied to the bottom rubber, the problem that the bending resistance and wear resistance are remarkably deteriorated. There is. On the other hand, if the minimum amount of carbon is used, not only will the conductivity be deteriorated, but the amount of rubber will increase due to the small amount of carbon, and noise will be generated when the vehicle is attached to the engine. There is a problem to do. On the other hand, according to the present invention, it is possible to obtain a belt that satisfies all the characteristics required for the belt and maintains good conductivity.

When the content (X) of the conductive carbon is less than 2 parts by mass, the conductivity of the resulting transmission belt may be reduced. If it exceeds 20 parts by mass, the bending fatigue resistance and the wear resistance may be reduced. It is preferable that 9 ≦ X ≦ 20.

If the content (Y) of the furnace carbon black exceeds 90 parts by mass, the bending fatigue resistance and wear resistance of the resulting transmission belt may be reduced. It is preferable that 58 ≦ Y ≦ 90.

The rubber composition for a transmission belt further satisfies the relationship of 70 ≦ 8X + Y ≦ 200 in addition to the content of conductive carbon (X) and the content of furnace carbon black (Y) in the above ranges. If this relational expression is not satisfied, there is a possibility that a transmission belt having excellent conductivity, conductivity maintaining property after running, bending fatigue resistance and wear resistance cannot be obtained.

The conductive carbon is more than a DBP oil absorption of 300 cm ^3/100 g. If it is less than 300 cm ^3/100 g, excellent conductivity, conductive maintenance characteristics after running, it may not be possible to obtain a transmission belt having a flex fatigue resistance and abrasion resistance. Preferably 350cm at ^3/100 g or more, and more preferably 350~500cm ³ / 100g. ^However, even when more than 500 cm 3/100 g, technically some potential use.

In this specification, the DBP oil absorption is an absorption of DBP (dibutyl phthalate) per 100 g of carbon black, and is measured according to JIS K6217. The DBP oil absorption value has a positive correlation with the porosity of carbon black and indirectly quantifies the specific surface area of carbon black.

The conductive carbon is not particularly limited as long as it has conductivity and has the specific DBP oil absorption, and a conventionally known carbon can be used.
Examples of the conductive carbon include conductive carbon black such as thermal black, ketjen black, acetylene black, channel black, and color black; graphite and the like. Among these, conductive carbon black is preferable from the viewpoint that a transmission belt having excellent conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance can be obtained. These may be used alone or in combination of two or more.

The thermal black is a carbon having a large particle diameter obtained by thermal decomposition of natural gas, and examples thereof include FT carbon and MT carbon. The ketjen black and acetylene black are obtained by incomplete combustion of natural gas or the like and thermal decomposition of acetylene, respectively, and were developed as highly conductive fillers.

Among the conductive carbons, ketjen black is particularly preferably used because a transmission belt having excellent conductivity, conductivity maintaining property after running, bending fatigue resistance and wear resistance can be obtained.
The ketjen black preferably has an average primary particle diameter of 1 to 50 nm and a specific surface area (BET) of 700 to 1300 m ² / g. Thereby, the effect of the present invention can be obtained more effectively.

Examples of the commercially available ketjen black include “Ketjen EC” and “Ketjen EC-600JD” (trade name, manufactured by Ketjen Black International).

The furnace carbon black has a nitrogen adsorption specific surface area of 40 to 100 m ² / g. When a transmission belt is manufactured using a rubber composition blended within a range satisfying the above formula, it is possible to obtain conductivity with a small amount of addition when the nitrogen adsorption specific surface area is within the above range. Excellent electrical conductivity, electrical conductivity maintaining property after running, bending fatigue resistance, and abrasion resistance can be obtained. If it is less than 40 m ² / g, the conductivity of the resulting transmission belt, the conductivity maintenance property after running, the bending fatigue resistance, and the wear resistance may be reduced.

The nitrogen adsorption specific surface area (N ₂ SA) is a value measured by ASTM D3037-88 “Standard Test Method for Carbon Black-Surface Area by Nitrogen Absorption” Method B. The measured value of IRB # 6 by this method is 76 m ² / g.

The furnace carbon black is of the DBP oil absorption amount 100~160cm ³ / 100g. Exceeds 160cm 3 ^/ 100g, it may not be possible to obtain a transmission belt having excellent flex fatigue resistance and abrasion resistance.

The furnace carbon black is not particularly limited as long as it is a filler obtained by incomplete combustion of hydrocarbon oil or natural gas and has the specific nitrogen adsorption specific surface area and DBP oil absorption amount. Depending on the diameter, SAF, ISAF, IISAF, HAF, FF, FEF, MAF, GPF, SRF, CF and the like can be mentioned. Among the above-mentioned furnace carbon blacks, HAF and FEF are preferable from the viewpoint of obtaining a transmission belt having excellent conductivity, conductivity maintenance property after running, bending fatigue resistance and wear resistance. These may be used alone or in combination of two or more.
Examples of commercially available furnace carbon black include N550 (manufactured by Tokai Carbon Co., Ltd.), N330 (manufactured by Tokai Carbon Co., Ltd.), and the like.

Examples of the rubber contained in the rubber composition for a transmission belt include chloroprene rubber, natural rubber, nitrile rubber, styrene / butadiene rubber, butadiene rubber, ethylene-α-olefin elastomer, ethylene / propylene rubber, and chlorosulfonated polyethylene rubber. And acrylic rubber, urethane rubber, hydrogenated acrylonitrile rubber and the like.

Of these, ethylene-α-olefin elastomers are preferred. By using ethylene-α-olefin elastomer as rubber and blending conductive carbon and furnace carbon black within the range satisfying the above formula, better conductivity, conductivity maintenance property after running, bending resistance A transmission belt having fatigue and wear resistance can be obtained. Moreover, it is preferable also from an environmental viewpoint.

Examples of the ethylene-α-olefin elastomer include a rubber made of a copolymer of an α-olefin excluding ethylene and ethylene and a diene (non-conjugated diene), and a copolymer of an α-olefin excluding ethylene and ethylene. Or a partially halogen-substituted product thereof, or a mixture of two or more of these. As the α-olefin excluding ethylene, at least one selected from the group consisting of propylene, butene, hexene and octene is preferably used. Among these, ethylene-α-olefin elastomers include ethylene-propylene-diene rubber (hereinafter also referred to as EPDM), ethylene-propylene copolymer (EPM), ethylene-butene copolymer (EBM), and ethylene-octene copolymer (EOM). These halogen substitution products (particularly chlorine substitution products) and mixtures of two or more of these are preferably used.

In the ethylene-α-olefin elastomer, the ethylene content may be 50 to 70% by mass in a total amount of 100% by mass of ethylene, α-olefin and diene constituting the ethylene-α-olefin elastomer. preferable. As a result, it is possible to obtain a transmission belt having good conductivity, conductivity maintaining characteristics after running, bending fatigue resistance, and wear resistance.

As the diene component, a non-conjugated diene such as 1,4-hexadiene, dicyclopentadiene or ethylidene norbornene is usually used as appropriate. These may be used alone or in combination of two or more.

In the ethylene-α-olefin elastomer, the non-conjugated diene is preferably 50 or less, more preferably 4 to 40 as the iodine value of the elastomer. The ethylene-α-olefin elastomer preferably has a Mooney viscosity ML _{1 + 4} (125 ° C.) of 40 to 70. As a result, it is possible to obtain a transmission belt having good conductivity, conductivity maintaining characteristics after running, bending fatigue resistance, and wear resistance.

Examples of commercially available ethylene-α-olefin elastomers include Esprene 301 (trade name, manufactured by Sumitomo Chemical Co., Ltd.), X-3012P, 3085 (trade name, manufactured by Mitsui Chemicals), EP21, EP65 (trade name, JSR). Co., Ltd.), 5754, 582F (trade name, manufactured by Sumitomo Chemical Co., Ltd.) and the like.

It is preferable that the rubber composition for a power transmission belt is blended with a content of process oil of 30 parts by mass or less with respect to 100 parts by mass of the rubber. By blending the process oil with the rubber composition for a transmission belt, it becomes possible to improve the workability in manufacturing the transmission belt. However, for example, when the back rubber layer of the belt is manufactured using a rubber composition containing a process oil, the back rubber layer is worn on the back of the belt when the pulley and the back of the belt come into contact with each other. There may be a case where the noise of the belt at the time of separation or the noise of the belt hitting the pulley at the time of contact with the flat pulley is generated.

The rubber composition for a transmission belt of the present invention can improve processability even when the amount of process oil added is small, and can suppress the occurrence of the above problems. When the said compounding quantity exceeds 30 mass parts, there exists a possibility that workability may fall or bending fatigue resistance and abrasion resistance may fall. It is more preferably 5 to 25 parts by mass.

The process oil is not particularly limited as long as it is generally used for rubber, and examples thereof include paraffinic, naphthenic, and aromatic process oils. Among these, paraffinic process oil is preferably used because a transmission belt having good sound characteristics, bending fatigue resistance, and abrasion resistance can be obtained.

The rubber composition for a transmission belt can be crosslinked with sulfur or an organic peroxide.
The organic peroxide is not particularly limited. For example, di-t-butyl peroxide, di-t-amyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 1,4-di-t- Butylperoxyisopropylbenzene, 1,3-di-t-butylperoxyisopropylbenzene, 2,2-di-t-butylperoxybutane, 2,5-dimethyl-2,5-di- (t-butylper Oxy) hexane, 2,5-dimethyl-2,5-di-t-butylperoxy) hexyne-3, n-butyl-4,4-di-t-butylvalerate, 1,1-di-t- Butylperoxycyclohexane, di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) pro Dialkyl peroxides such as t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, t-butyl peroxymalate, t-butyl peroxyneodecanoate, t-butylperoxybenzoate, di-t-butylperoxyphthalate, t-butylperoxydilaurate, 2,5-dimethyl-2,5-di- (benzoylperoxy) hexane, t-butylperoxyisopropyl carbonate Peroxyesters such as; ketone peroxides such as dicyclohexanone peroxide; and mixtures thereof. Of these, organic peroxides having a half-life of 1 minute at a temperature in the range of 130 to 200 ° C. are preferred, and in particular, di-t-butyl peroxide, di-t-amyl peroxide, and t-butylcumyl peroxide. Dicumyl peroxide and 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane can be preferably used. These may be used alone or in combination of two or more.

In the rubber composition for a transmission belt, the amount of the organic peroxide is preferably 0.001 to 0.1 mol with respect to 100 parts by mass (solid content) of the rubber. If the amount is less than 0.001 mol, the crosslinking does not proceed sufficiently and there is a risk that the mechanical strength will not be exhibited. When it exceeds 0.1 mol, the scorch safety of the vulcanizate or the elongation of the vulcanizate may deviate from the practical range. More preferably, it is 0.005-0.05 mol.

In the case of the above peroxide crosslinking, a crosslinking aid may also be blended. By blending a crosslinking aid, the degree of crosslinking can be increased to further stabilize the adhesive force, and problems such as adhesive wear can be prevented. Examples of the crosslinking aid include triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), 1,2 polybutadiene, metal salt of unsaturated carboxylic acid, oximes, guanidine, trimethylolpropane trimethacrylate, ethylene glycol diester. Mention may be made of those usually used for peroxide crosslinking, such as methacrylate, N, N'-m-phenylenebismaleimide and sulfur.

In the case of the sulfur vulcanization, the amount of sulfur added is preferably 1 to 3 parts by mass with respect to 100 parts by mass of the rubber.
In the case of sulfur vulcanization, a vulcanization accelerator may be blended. By blending a vulcanization accelerator, the degree of vulcanization can be increased and problems such as adhesive wear can be prevented. The vulcanization accelerator is not particularly limited as long as it is generally used as a vulcanization accelerator. Examples thereof include N-oxydiethylenebenzothiazole-2-sulfenamide (OBS) and tetramethylthiuram disulfide (TMTD). , Tetraethylthiuram disulfide (TETD), zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), N-cyclohexylbenzothiazole-2-sulfenamide, 2-mercaptobenzothiazole, dibenzothiazolyl disulfide, etc. be able to.

The rubber composition for a transmission belt may contain short fibers. The short fibers are not particularly limited, and examples thereof include short fibers made of nylon 6, nylon 66, polyester, cotton, aramid, and the like. By appropriately selecting the short fibers, it is possible to improve performances such as wear resistance, noise prevention, and bending fatigue resistance. By appropriately adjusting the length or shape of the short fiber, it is possible to improve the performance such as wear resistance and noise prevention property, but the length of the short fiber is usually 0.1-3. 0.0 mm is preferred.

The above-mentioned rubber composition for power transmission belts, together with the above-described components, may be used as usual, such as reinforcing agents such as silica, fillers such as calcium carbonate and talc, plasticizers, stabilizers, processing aids, colorants and the like. It may contain various chemicals used in the rubber industry.

The rubber composition for a transmission belt is mixed by using a normal mixing means such as a roll or a banbury together with the rubber, conductive carbon, furnace carbon black and, if necessary, the above-described components. Can be manufactured.

The transmission belt of the present invention is obtained using the above-described rubber composition for a transmission belt. Therefore, the transmission belt has excellent conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance, and can be suitably used.

Examples of the transmission belt include those in which at least a part of rubber elements constituting the belt is obtained using the above-described rubber composition for a transmission belt. Examples of the transmission belt include a V-ribbed belt, a double-ribbed belt, and a flat belt.

FIG. 1 shows an example of a V-ribbed belt. FIG. 1 is a schematic view showing a cross-sectional view (surface perpendicular to the belt longitudinal direction) of an example of a V-ribbed belt.
1 has a back rubber layer 2 and a bottom rubber layer 3, and an adhesive rubber layer 4 between the back rubber layer 2 and the bottom rubber layer 3, and is arranged in the belt longitudinal direction. The core wire 5 is fixed by the adhesive rubber layer 4. Further, the bottom rubber layer 3 has a plurality of cross-sectional V-shaped grooves (ribs) formed continuously in the belt longitudinal direction. In many cases, short fibers (not shown) are dispersed in the bottom rubber layer 3 so as to be oriented in the width direction of the belt in order to enhance the side pressure resistance.

The V-ribbed belt 1 is obtained by using the above-described rubber composition for a transmission belt in which at least a part of the rubber elements constituting the belt is obtained. Here, the rubber elements include a back rubber layer 2, a bottom rubber. Layer 3 and adhesive rubber layer 4. Among the rubber elements, the back rubber layer 2 or the bottom rubber layer 3 is preferably obtained using the above-described rubber composition for a transmission belt, and both the back rubber layer 2 and the bottom rubber layer 3 are described above. More preferably, it is obtained using a rubber composition for a power transmission belt. In this case, the V-ribbed belt 1 has excellent conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance. In addition, when the back rubber layer 2 or the bottom rubber layer 3 is not obtained by using the above-described rubber composition for a transmission belt, the rubber layer may be, for example, the above-described rubber, or other conventionally known other as required. It can be obtained by using a composition containing the components.

The said adhesive rubber layer 4 can be obtained with a conventionally well-known composition, for example, can be obtained using the rubber composition containing the rubber | gum mentioned above. It is preferable that the rubber composition for obtaining the adhesive rubber layer 4 uses an ethylene-α-olefin elastomer as the rubber. Thereby, the effect of the present invention can be obtained. The rubber composition may contain other conventionally known components.

As the core 5, a polyester core, a nylon core, a vinylon core, an aramid core, or the like is preferably used. Polyethylene terephthalate and polyethylene naphthalate are preferably used as the polyester core, and 6,6-nylon (polyhexamethylene adipamide) and 6 nylon are preferably used as the nylon core. As the aramid core, copolyparaphenylene, 3,4′oxydiphenylene, terephthalamide, polyparaphenylene terephthalamide, polymetaphenylene isophthalamide, or the like is preferably used. These core wires are generally bonded with a resorcin-formalin-latex adhesive composition (RFL adhesive) or the like and embedded in the adhesive rubber layer 4.

FIG. 2 shows an example of a flat belt. FIG. 2 is a schematic view showing a cross-sectional view (plane perpendicular to the longitudinal direction of the belt) of an example of a flat belt.
The flat belt 6 shown in FIG. 2 includes a back rubber layer 2 and a bottom rubber layer 3, and an adhesive rubber layer 4 between the back rubber layer 2 and the bottom rubber layer 3, and is arranged in the belt longitudinal direction. The core wire 5 is fixed by the adhesive rubber layer 4. In many cases, short fibers (not shown) are dispersed in the bottom rubber layer 3 so as to be oriented in the width direction of the belt in order to enhance the side pressure resistance.

The flat belt 6 is obtained by using the above-described rubber composition for a transmission belt, at least a part of the rubber elements constituting the belt. The back rubber layer 2, the bottom rubber layer 3, the adhesive rubber layer 4, and the core wire 5 in the flat belt 6 can be the same as those in the V-ribbed belt 1. Further, the back rubber layer 2 and the bottom rubber layer 3 are also preferably formed in the form obtained by using the above-described rubber composition for a transmission belt. In this case, the flat belt 6 has excellent conductivity, after running. It has the following electrical conductivity maintaining characteristics, bending fatigue resistance and wear resistance.

FIG. 3 shows an example of a double ribbed belt. FIG. 3 is a schematic view showing a cross-sectional view (surface perpendicular to the longitudinal direction of the belt) of an example of a double ribbed belt.
3 has a bottom rubber layer 3 and an adhesive rubber layer 4 between the bottom rubber layer 3, and a core wire 5 disposed in the belt longitudinal direction is the adhesive rubber layer. 4 is fixed. Further, the bottom rubber layer 3 has a plurality of cross-sectional V-shaped grooves (ribs) formed continuously in the belt longitudinal direction. In many cases, short fibers (not shown) are dispersed in the bottom rubber layer 3 so as to be oriented in the width direction of the belt in order to enhance the side pressure resistance.

In the double-ribbed belt 7, at least a part of the rubber elements constituting the belt is obtained by using the above-described rubber composition for a transmission belt. As the bottom rubber layer 3, the adhesive rubber layer 4, and the core wire 5 in the double ribbed belt 7, the same ones as in the V ribbed belt 1 can be used. Moreover, the point that the bottom rubber layer 3 is preferably obtained by using the above-described rubber composition for a transmission belt is also the same. In this case, the double ribbed belt 7 has excellent conductivity, conductivity maintaining property after running, It has bending fatigue resistance and wear resistance.

The transmission belt has the following dynamic viscoelastic properties of the vulcanized rubber constituting the transmission belt: tensile mode, frequency 10 Hz, static load 3 kgf / cm ² , dynamic strain 0.6%, temperature 25 ° C. The tan δ in the belt longitudinal direction (reverse direction) is preferably 0.25 or less. In this case, the transmission belt is excellent in all of conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance. The tan δ is more preferably 0.10 to 0.20.

Further, the transmission belt preferably has a storage elastic modulus E ′ of 20 to 50 MPa under the above conditions as a dynamic viscoelastic property of the vulcanized rubber constituting the transmission belt. In this case, the transmission belt is excellent in all of conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance. In the present specification, the above tan δ and E ′ are the conditions under the above-mentioned conditions using the Rheometrics RSAII, the specimen shape is 1 mm in thickness, 5 mm in width and 60 mm in length, and the distance between chucks is 22.7 mm. The value obtained by measuring dynamic viscoelasticity.

According to JIS K6229, the above transmission belt is based on JIS K6229 as the dynamic viscoelastic property of the vulcanized rubber constituting the transmission belt, under the conditions that the extraction solvent is n-hexane, the test method is method A, and the extraction device is type 1. The solvent extraction amount is preferably 14% or less. In this case, the transmission belt is excellent in all of conductivity, conductivity maintaining property after running, bending fatigue resistance, and wear resistance. The solvent extraction amount is more preferably 5 to 14%.

The transmission belt preferably has a hardness of 80 to 95 as measured by a type A durometer according to JIS K6253 as the dynamic viscoelastic properties of the vulcanized rubber constituting the transmission belt. The transmission belt has a tensile strength of 5 to 20 MPa, an elongation of 150 to 250%, an M100 (elongation of 100) as a dynamic viscoelastic property of the vulcanized rubber constituting the transmission belt in a tensile test according to JIS K6251. % Tensile stress) is preferably 4.0 to 10.0 MPa. When the vulcanized rubber constituting the transmission belt has such dynamic viscoelastic properties, the properties required for the transmission belt are excellent. Further, the conductivity, the conductivity maintaining property after running, the bending fatigue resistance and the wear resistance are also excellent.

The transmission belt having the tan δ, E ′, solvent extraction amount, hardness, tensile strength, elongation, and vulcanized rubber characteristics of M100 can be obtained by appropriately selecting and using the above-described rubber composition for the transmission belt. It becomes possible.

The power transmission belt of the present invention can be manufactured by a conventional method conventionally known. For example, the V-ribbed belt can be manufactured by the following manufacturing method. A composition containing components such as rubber is kneaded using a closed kneader, and the resulting rubber composition is rolled with an open roll to produce an unvulcanized sheet. The obtained unvulcanized sheet is used for the bottom rubber layer and the back rubber layer, and after laminating the adhesive rubber layer in which the core wire such as polyester core wire is embedded and the bottom rubber layer, the back rubber layer is bonded. Thus, a V-ribbed belt can be obtained.

Rubber composition for a transmission belt of the present invention, with respect to 100 parts by mass of the rubber, DBP oil absorption of 300 cm ³ / and more conductive carbon 100 g, the nitrogen adsorption specific surface area 40 to 100 m ² / g, DBP oil absorption amount 100~160cm ^3/100 g and furnace carbon black is one that is formulated within the range which satisfies the above equation. Because it is a rubber composition formulated to satisfy such a specific relationship, by using this rubber composition, all the properties of conductivity, conductivity maintenance property after running, bending fatigue resistance and wear resistance can be achieved. An excellent transmission belt can be obtained.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.

Examples 1-11, 16-22, Comparative Examples 1-13
Table 1 shows the composition of the rubber composition used for forming the bottom rubber layer and the back rubber layer of the transmission belt. Table 2 shows the composition of the rubber composition used for forming the adhesive rubber layer.

The commercially available ethylene-propylene-diene rubber (EPDM) used is as follows.
Ethylene content 63% by mass, propylene content 34% by mass, ethylidene norbornene (ENB) content 3% by mass
Mooney viscosity ML _{1 + 4} (125 ° C.) 40

(Manufacture of transmission belt)
The rubber composition used for forming the bottom rubber layer and the back rubber layer was kneaded using a closed kneader, and the obtained rubber composition was rolled with an open roll to obtain an unvulcanized sheet. This unvulcanized sheet was used for the bottom rubber layer and the back rubber layer. Further, an unvulcanized sheet was similarly prepared using the rubber composition used for forming the adhesive rubber layer, and used for the adhesive rubber layer. After laminating the adhesive rubber layer in which the polyester core wire was embedded and the bottom rubber layer, the back rubber layer was adhered to obtain a V-ribbed belt.

(Creation of vulcanized rubber sheet for measuring vulcanized rubber properties)
Using the rubber composition used to form the bottom rubber layer and the back rubber layer, an unvulcanized sheet is obtained by the same method as in the production of the transmission belt, and vulcanized for vulcanized rubber property measurement by further vulcanization. A rubber sheet was obtained (vulcanization conditions: 170 ° C. × 20 minutes).
Table 3 shows tan δ, E ′, solvent extraction amount, rubber hardness, tensile strength, elongation, and M100 in the belt longitudinal direction (reverse direction) of the vulcanized rubber sheet obtained above. These values are values measured by the method described above.

The obtained V-ribbed belt was subjected to the belt stand test described below, and the electrical resistance characteristics, the heat-resistant bending travel life, and the wear amount due to 24-hour belt travel were examined. The results are shown in Table 4. For the method of measuring electrical resistance, place a belt on the brass base with the measuring surface facing down, place a 1 kg weight on it, put the terminal of the electrical resistance meter on the brass base, and apply a voltage of 500V. Then, the electrical resistance value was measured (a schematic diagram of electrical resistance measurement is shown in FIG. 4).

(Electric resistance characteristics by belt running)
A belt was installed in a 5-axis layout as shown in FIG. 5, and the electrical resistance before running and the electrical resistance after running for 200 hours were measured.

(Heat-resistant bending test)
Belts were installed in a 5-axis layout as shown in FIG. 5 and evaluated from the time from the start of travel to the time when cracks occurred in the V-ribbed belt. The results shown in Table 4 were obtained by index-converting the time until crack generation until Comparative Example 1 was 100.

(Abrasion test)
A belt was installed in a two-axis layout as shown in FIG. The results shown in Table 4 are obtained by index-converting the weight wear rate with Comparative Example 1 as 100.
Moreover, the presence or absence of adhesion was also evaluated. The presence or absence of the occurrence of an adhesive on the belt subjected to the abrasion test was judged visually.

In Comparative Example 1 (in the case of an existing general composition), the electric resistance after running for 200 hours was 1000 MΩ or more, and did not reach the target of 10 MΩ. Comparative Example 2 (mixed in a large amount only with furnace carbon black) had an electric resistance of 0.8 MΩ after running for 200 hours, which was much better than Comparative Example 1, but the heat-resistant bending running life was 80 of Comparative Example 1. %, The amount of wear after 24 hours was 2.5 times larger. Comparative Example 3 (containing only a large amount of conductive carbon) had good electrical resistance characteristics and wear resistance, but had a heat-resistant bending travel life of only 40% of Comparative Example 1.

Comparative Example 4 (conductive carbon 5 parts + furnace carbon black 20 parts) was excellent in heat resistance flexibility and wear resistance, but inferior in electric resistance characteristics. Comparative Examples 5 and 6 (Comparative Example 2 + conductive carbon) had better wear resistance than Comparative Example 2, but were inferior in heat-resistant flexibility. Comparative Example 7 (conductive carbon 16 parts + furnace carbon black 90 parts) was inferior in these properties with 1.5 times the abrasion and 70% heat-resistant flexibility. Comparative Example 8 (20 parts of conductive carbon + 60 parts of furnace carbon black) had a heat-resistant flexibility of 80% of Comparative Example 1. Comparative Example 9 (conductive carbon 22 parts + furnace carbon 40 parts) had a heat-resistant flexibility of 70%. In addition, in other examples (Comparative Examples 10 to 11) that are out of the range of the above formula, those excellent in all performances were not obtained.

In the examples, the heat-resistant bending running life and the wear resistance were almost the same as those of Comparative Example 1, and the electric resistance characteristics were remarkably good. Further, as can be seen from the results of the comparative example and the example, the wear resistance is improved when tan δ (25 ° C.) is lowered. In addition, when the amount of hexane extracted is large (14% or more) and the amount of process oil is large, the wear characteristics are remarkably deteriorated. Furthermore, an adhesive is also generated.

FIG. 7 shows the blending relationship of conductive carbon and furnace carbon black in Examples 1 to 11, 16 to 18 and Comparative Examples 1 to 11. From the graph shown in FIG. 7, in order to obtain a transmission belt that is excellent in all of the heat-resistant bending running life, wear resistance, and electric resistance characteristics, the composition of conductive carbon and furnace carbon black is adjusted within the range of the above formula. It turns out that is very important.

FIG. 8 is a diagram showing the relationship between the characteristics of furnace carbon black and various belt characteristics. FIG. 9 is a diagram showing the relationship between the characteristics of conductive carbon and various belt characteristics. According to the results of these figures, if the blending amount range in the present invention is satisfied and the DBP oil absorption amount and the nitrogen adsorption specific surface area are satisfied, even if the carbon species is changed, there is no difference in electric resistance and other physical properties after running. And it has been proven that similar results can be obtained. On the contrary, it is shown that when carbon deviating from the specified ranges of the DBP oil absorption amount and the nitrogen adsorption specific surface area in the present invention is used, the conductivity or other physical properties cannot be satisfied.

FIG. 10 shows the relationship between the blending amounts of conductive carbon and furnace carbon black, and the numerical values in the figure show the characteristic values of the belt. This result proves the important significance of the above formula, DBP oil absorption, and nitrogen adsorption specific surface area in the present invention.

Examples 12-15
A transmission belt and a vulcanized rubber sheet for measuring vulcanized rubber properties were produced in the same manner except that the composition of the rubber composition used for forming the bottom rubber layer and the back rubber layer was changed to that shown in Table 5. . Further, the obtained transmission belt and vulcanized rubber sheet for measuring vulcanized rubber properties were similarly evaluated, and the results are shown in Tables 6 and 7.

The commercially available ethylene-propylene-diene rubber (EPDM) used is as follows.
[Nordel IP 4640]
Ethylene content 55% by mass, propylene content 40.1% by mass, ethylidene norbornene (ENB) content 4.9% by mass
Mooney viscosity ML _{1 + 4} (125 ° C.) 40
[Nordel IP 4570]
Ethylene content 50% by mass, propylene content 45.1% by mass, ethylidene norbornene (ENB) content 4.9% by mass
Mooney viscosity ML _{1 + 4} (125 ° C.) 70
[Nordel IP 4770]
Ethylene content 70% by mass, propylene content 25.1% by mass, ethylidene norbornene (ENB) content 4.9% by mass
Mooney viscosity ML _{1 + 4} (125 ° C.) 70

In Examples 12 to 15, different Mooney viscosities and ethylene contents were examined. It was revealed that the higher the Mooney viscosity and ethylene content, the better the wear resistance and heat flexibility.

The power transmission belt of the present invention can be suitably used as a V-ribbed belt, a double-ribbed belt, a flat belt or the like. In addition, it can be expected to be applied to other belts that require electrical conductivity.

It is an example of a cross-sectional view (surface perpendicular to the belt longitudinal direction) of the V-ribbed belt. It is an example of the cross-sectional view of a flat belt. It is an example of the cross-sectional view of a double ribbed belt. It is the schematic of an electrical resistance measurement. It is the schematic of the driving | running | working test apparatus used for the electrical resistance characteristic by belt driving | running | working and a heat-resistant bending driving | running | working test. It is the schematic of the apparatus which performs an abrasion test. It is the graph which showed the relationship of the combination of the conductive carbon of Examples 1-11 and Comparative Examples 1-9, and furnace carbon black. It is the figure which showed the relationship between the characteristic of furnace carbon black, and various belt characteristics. It is the figure which showed the relationship between the characteristic of conductive carbon, and various belt characteristics. It is the figure which showed the relationship of the compounding quantity of electroconductive carbon and furnace carbon black.

Explanation of symbols

1, 11, 31 V-ribbed belt 2 Back rubber layer 3 Bottom rubber layer 4 Adhesive rubber layer 5 Core wire 6 Flat belt 7 Double-ribbed belt 12 Electrical resistance meter 13 Terminal (measurement unit)
14 Brass base 15 Weight (1kg)
21, 32 Drive pulley 22, 33 Driven pulley

Claims (9)

Per 100 parts by mass of the rubber, DBP oil absorption of 300 cm ³ / and more conductive carbon 100 g, the nitrogen adsorption specific surface area 40~100m ² / g, DBP oil absorption amount 100~160cm ³ / 100g furnace carbon black and the following formula ;
70 ≦ 8X + Y ≦ 200 and 2 ≦ X ≦ 20 and 0 ≦ Y ≦ 90
[In formula, X represents content (mass part) of the said conductive carbon. Y represents content (mass part) of the said furnace carbon black. ]
A rubber composition for a transmission belt, wherein the rubber composition is blended within a range satisfying the above. The rubber composition for a transmission belt according to claim 1, wherein the rubber is an ethylene-α-olefin elastomer. The rubber composition for a transmission belt according to claim 2, wherein the ethylene-α monoolefin elastomer has a Mooney viscosity ML _{1 + 4} (125 ° C.) of 40 to 70. The rubber composition for a transmission belt according to claim 2 or 3, wherein the ethylene-α-olefin elastomer has an ethylene content of 50 to 70%. The rubber composition for a transmission belt according to claim 1, 2, 3, or 4, wherein the process oil is blended in an amount of 30 parts by mass or less with respect to 100 parts by mass of the rubber. A transmission belt obtained by using the rubber composition for a transmission belt according to claim 1, 2, 3, 4 or 5. As the dynamic viscoelastic characteristics of the vulcanized rubber constituting the transmission belt, tan δ in the longitudinal direction of the belt is obtained under the conditions of tensile mode, frequency 10 Hz, static load 3 kgf / cm ² , dynamic strain 0.6%, and temperature 25 ° C. The transmission belt according to claim 6, wherein the transmission belt is 0.25 or less. As the dynamic viscoelastic properties of the vulcanized rubber constituting the transmission belt, the extraction amount of the solvent is 14% under the condition that the extraction solvent is n-hexane, the test method is method A, and the extraction device is type 1 according to JIS K6229. The transmission belt according to claim 6 or 7, wherein: The power transmission belt according to claim 6, 7 or 8, which is a V-ribbed belt, a double-ribbed belt or a flat belt.

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