JP2011088991A - Rubber composition and belt using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition excellent in abrasion resistance and durability while maintaining physical properties inherent to rubber; and to provide a belt using the same. <P>SOLUTION: The rubber composition contains a whole aromatic polyamide fiber in a rubber polymer, wherein the whole aromatic polyamide fiber has a diameter of 25 to 70 μm and a length of 1.0 to 6.0 mm; 5 to 50 pts.wt. of the whole aromatic polyamide fiber is contained in 100 pts.wt. of the rubber polymer; in the cross section of the rubber composition, 30 to 80 wt.% of the total amount of the whole aromatic polyamide fiber contained in the rubber composition is present in the surface layer portion of 5% from the surface with respect to the total thickness of the rubber composition; and the whole aromatic polyamide fiber of 0.1 to 0.8 mm in an average fiber length protrudes from the rubber composition surface. The belt is made using the rubber composition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition with improved durability, which is preferably used mainly for a transmission belt, and a belt using the rubber composition.

  In power transmission members such as transmission belts, high demands such as low noise, improvement of dynamic load capacity, and wear resistance are imposed. Conventionally, as a belt satisfying such characteristics, it has been studied to have a layer containing fibers on the contact surface of the power transmission unit of the belt.

  For example, Patent Document 1 discloses that a kevlar pile having a specific aspect ratio is provided with a raised layer on at least one power transmission surface on the power transmission side and the driven side by electrostatic flocking, thereby reducing weight, low noise, and power transmission efficiency. An excellent power transmission member is described. Certainly, this method improves light weight, low noise, and power transmission efficiency, but the flocked fibers are not entangled with each other, and high compressive shear stress is applied from the napped layer surface over a long period of time as in actual operation. In this case, the bond strength between the fiber and the adhesive is not so strong, and even if the fiber itself, such as Kevlar, implants a highly abrasion-resistant fiber, the problem is that the pile tends to fall off after a long period of use. There is.

For the same purpose, Patent Document 2 proposes a non-woven fabric in which fibers are raised on the power transmission surface of a belt. Although this method is also effective in improving the low noise property and dynamic load capacity, the nonwoven fabric on the surface is described as having a basis weight of 30 to 100 g / m ² , but polishing such a nonwoven fabric with a low basis weight is not possible. It is difficult industrially, and it is difficult to obtain a fixed brushed density with large polishing spots. Furthermore, although it is needle punched, the binder is not used, and the raised fiber has poor entanglement and adhesiveness, and when high compression shear stress is applied over a long period of time, there is a problem that the fiber easily falls off from the surface. .

  Further, Patent Document 3 discloses a belt in which the surface portion of the power transmission unit is made of an elastomer including an aramid short fiber and the short fibers protrude to the outside. Patent Document 4 discloses only a surface portion outermost layer of the power transmission unit. In addition, a belt having a vulcanized elastomer layer in which fibers are mixed is proposed. However, these belts are effective in improving noise reduction and dynamic load capacity, but still have the problem that the fibers fall off from the surface as described above. Under these circumstances, it is desired to develop a transmission belt having a wear-resistant fibrous layer on the surface of the power transmission portion that is hard to drop off fibers.

  As a countermeasure, in Patent Document 5, the weight ratio of 50/50 to 90% is a short fiber made of copolyparaphenylene, 3,4'-oxydiphenylene terephthalamide and a pulp made of polyparaphenylene terephthalamide on the surface of the power transmission unit. Although a method of providing a layer containing para-type aromatic polyamide fiber paper composed of / 10 has been proposed, there is a concern that the fiber paper and the rubber layer have low adhesiveness and the fiber paper peels off.

Japanese Patent Laid-Open No. 9-14361 JP 2004-251402 A Japanese Patent Laid-Open No. 1-164839 JP 2005-337495 A JP 2008-32073 A

  An object of the present invention is to provide a rubber composition excellent in wear resistance and durability while maintaining the original properties of rubber and a belt using the same.

  As a result of intensive studies in view of the above-mentioned background art, when an aromatic polyamide fiber having a specific shape is kneaded with rubber, the fiber is distributed on the surface of the rubber composition and is firmly held, and has excellent wear resistance. The present inventors have found that a rubber composition can be obtained, and have reached the present invention.

  Thus, according to the present invention, a rubber composition containing a wholly aromatic polyamide fiber in a rubber polymer, wherein the wholly aromatic polyamide fiber has a diameter of 25 to 70 μm and a length of 1.0 to 6.0 mm. And 5 to 50 parts by weight of wholly aromatic polyamide fiber is contained with respect to 100 parts by weight of the rubber polymer, and in the cross section of the rubber composition, 5% from the surface with respect to the total thickness of the rubber composition 30-80% by weight of the total weight of the total aromatic polyamide fiber contained in the rubber composition is present in the surface layer portion of the rubber composition, and the total aromatic has an average fiber length of 0.1-0.8 mm from the surface of the rubber composition Provided is a rubber composition characterized by protruding polyamide fibers. Moreover, according to this invention, the belt using the said rubber composition is provided.

  According to the present invention, it is possible to provide a rubber composition in which a specific wholly aromatic polyamide fiber is kneaded with rubber so that the fiber is concentrated on the rubber surface portion and the fiber is appropriately protruded. . In addition, this makes it possible to significantly improve the wear resistance and durability of the rubber composition, and in particular, it can be used for a belt and exhibit excellent performance.

It is a schematic diagram of the apparatus used for the durability test of the belt of this invention.

  The rubber composition of the present invention is a rubber composition containing a wholly aromatic polyamide fiber in a rubber polymer. The main material of the rubber composition used in the present invention is not particularly defined as long as it is a polymer material that can exhibit rubber elasticity. For example, acrylic rubber, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, isoprene rubber, urethane rubber, ethylene-propylene rubber, epichlorohydrin rubber, chlorosulfonated polyethylene rubber, chloroprene rubber, silicone rubber, styrene-butadiene rubber, Examples thereof include polysulfide rubber, natural rubber, butadiene rubber, butyl rubber, and fluorine rubber. These may be used alone or in a blend.

  These rubbers include inorganic fillers such as carbon black and silica, organic fillers such as coumarone resins and phenol resins, softeners such as naphthenic oils, anti-aging agents, and vulcanization. Auxiliaries, processing aids and the like may be included as necessary. Further, organic / inorganic fiber fillers other than wholly aromatic polyamide fibers may be used in combination. In particular, the effect of the present invention can be obtained more by using a rubber matrix to which an inorganic filler is added.

  As the wholly aromatic polyamide fiber used in the present invention, polyparaphenylene terephthalamide short fiber and copolyparaphenylene 3,4'-oxydiphenylene terephthalamide short fiber are preferable. Among wholly aromatic polyamide fibers, In particular, when a copolyparaphenylene · 3,4′-oxydiphenylene · terephthalamide fiber having excellent wear resistance is used, a particularly good rubber composition is obtained. It can be obtained by dissolving a wholly aromatic polyamide fiber resin in a solvent, wet spinning and stretching by a known method.

  In the present invention, the diameter of the wholly aromatic polyamide fiber is 25 to 70 μm, the length is 1.0 to 6.0 mm, and 5 to 50 parts by weight of the wholly aromatic polyamide fiber is included with respect to 100 parts by weight of the rubber polymer. 30 to 30% of the total weight of the total aromatic polyamide fiber contained in the rubber composition in a surface layer portion of 5% from the surface with respect to the total thickness of the rubber composition in the cross section of the rubber composition. It is important that 80% by weight is present and wholly aromatic polyamide fibers having an average fiber length of 0.1 to 0.8 mm protrude from the surface of the rubber composition.

  As a result of investigations by the present inventors, when the wholly aromatic polyamide fiber having the above-mentioned diameter and length is contained and kneaded by adding 5 to 50 parts by weight of the wholly aromatic polyamide fiber to 100 parts by weight of the rubber polymer, A rubber composition is obtained in which rubber is concentrated on the surface layer of rubber, and an aromatic polyamide fiber having a specific average fiber length protrudes, and the rubber composition has improved wear resistance and durability. I found out.

  Therefore, when the diameter of the wholly aromatic polyamide fiber is 25 μm or less, that is, the diameter of the general wholly aromatic polyamide fiber is 5.5 to 24.7 μm (0.33 to 6.67 dtex), the rubber of the present invention having the above-described configuration is used. A composition cannot be obtained. On the other hand, when the diameter exceeds 70 μm, for example, in the case of copolyparaphenylene 3,4′-oxydiphenylene terephthalamide fiber, the amide solvent in the dope tends to remain, and the yarn-forming property is deteriorated. It is appropriate that the thickness is 70 μm or less.

  The fiber length of the wholly aromatic polyamide fiber is 1.0 to 6.0 mm, preferably 1.5 mm to 3.5 mm. When the fiber length is less than 1.0 mm, the rubber composition of the present invention in which fibers are concentrated and distributed on the surface layer portion of the rubber composition by kneading and the fibers protrude from the rubber surface with the average fiber length is obtained. Becomes difficult. When the fiber length exceeds 6.0 mm, the dispersibility of the fiber in the rubber is deteriorated, and at the same time, as in the case of less than 1.0 mm, the rubber composition having the constitution of the present invention tends not to be obtained.

  As described above, the content of the wholly aromatic polyamide fiber is 5 to 50 parts by weight with respect to 100 parts by weight of the rubber polymer. By adding the fiber in such an amount, the rubber composition having the constitution of the present invention can be obtained. it can. Further, if the content is less than 5 parts by weight, the effect of wear resistance cannot be obtained, and if it exceeds 50 parts by weight, wear resistance is obtained with a small amount of fiber which is one of the objects of the present invention. It will deviate from the purpose and the dispersibility in rubber will also deteriorate.

  The rubber composition of the present invention is characterized in that a total aromatic polyamide fiber having an average fiber length of 0.1 to 0.8 mm, preferably 0.1 to 0.5 mm, protrudes from the surface of the composition. To do. If the average fiber length is less than 0.1 mm, sufficient wear resistance cannot be obtained, and if it exceeds 0.8 mm, the fibers fall off.

  The surface of the fiber may be untreated or covered with a resin or rubber having good adhesion to the rubber main component described above. Examples of the resin include resorcin / holimarine / latex resin, and examples of the rubber include rubber paste in which each matrix rubber is dissolved. The amount of the resin or rubber covering the fiber surface is preferably 20 parts by weight or less with respect to 100 parts by weight of the fiber.

  The fibers protruding from the surface of the rubber composition are preferably 2 to 15% of the total aromatic polyamide fibers contained in the rubber composition. If it is less than 2%, sufficient wear resistance cannot be obtained, and if it exceeds 15%, there is a problem that the amount of fibers in the rubber (surface layer part) decreases when it falls off due to a very high load. Cheap.

  The rubber composition of the present invention described above can be produced, for example, by the following method. The method of cutting the wholly aromatic polyamide fiber used in the present invention into the fiber length is not particularly defined, and may be a guillotine type cut, a rotary type cut or a pulverized cut. The guillotine type cut and the rotary type cut are preferable because the fiber length distribution is narrow and the productivity is good.

  The method for blending and mixing the wholly aromatic polyamide fiber with the rubber so as to have the above content is not particularly limited, and can be kneaded by a known means and method as appropriate using, for example, a Banbury mixer, a kneader or the like. .

  After kneading, usually rubber products such as tires and belts are rolled into a sheet by using a calender roll or the like, and the thickness of the rubber sheet in this case needs to be in the range of 0.1 to 20 mm. is there. When the thickness is less than 0.1 mm, the surface layer portion, which is a feature of the rubber composition of the present invention, does not have 30 to 80% by weight of fibers. Moreover, even if the rubber sheet thickness exceeds 20 mm, the rubber composition of the present invention cannot be obtained.

  Moreover, when creating a sheet by rolling, it is necessary to relax after stretching under tension. The values of tension and relaxation vary depending on the type and thickness of the rubber type and calendar roll, and are difficult to limit, but the relaxation rate needs to be between 5 and 50%. When the relaxation rate is less than 5%, the rubber composition of the present invention is not obtained. When the relaxation rate exceeds 50%, it becomes difficult to control the shrinkage of the rubber sheet, and the sheet production is adversely affected.

  The rubber composition produced by the above method can be applied to applications that require wear resistance and high durability such as tires, belts, hoses, and shoe soles. The performance can be fully exhibited.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

(1) Measurement of fiber distribution in rubber Cut the cross section of a rubber compound described later, and examine the fiber distribution state with a laser microscope (manufactured by Keyence Corporation). The number of fibers contained in a square area with one side from the top to the bottom On the other hand, the ratio of the number of fibers included in the range of 5% from the upper end and the lower end is displayed in%.

(2) Length and number ratio of fibers protruding on rubber surface layer Calculate the length and number of fibers protruding on the surface per unit area with the same sample and device as in (1), and calculate the ratio to the total number of fibers. %indicate.

(3) Abrasion resistance A block having a width of 5 mm and a length of 15 mm was cut out from a rubber sheet having a thickness of 7 mm obtained by vulcanizing each rubber composition at 160 ° C. for 20 minutes to prepare a sample. Using a pin-on-disk friction and wear tester manufactured by Orientec Co., Ltd., the wear amount was measured on a No. 320 sandpaper with a load of 5 kg and a circumferential speed of 100 rpm so that the fiber cross-section direction of the sample was worn. . The abrasion resistance is indicated by an index display in which the amount of wear is 100 for the sample without the aramid fiber (Comparative Example 1). The lower the index, the better the wear resistance.

(4) Belt durability A rubber sheet having a thickness of 7 mm was wound around a drum, vulcanized using a steam vulcanizer at 160 ° C. for 20 minutes, and cut into a belt having a thickness of 2 mm to obtain a sample. 1 was adjusted so that a constant load of 10 kg was applied to the belt-like sample, and an endurance test was performed at a peripheral speed of 120 rpm. The time at which the belt broke was indicated by an index display with the sample without the aramid fiber (Comparative Example 1) being 100. Note that the higher the index, the better the durability.

[Examples 1-7, Comparative Examples 2-7]
Teijin Techno Products Technora, whose diameter (fineness) and fiber length are shown in Table 2, was added to the rubber having the composition shown in Table 1 in an amount of fiber relative to 100 parts by weight of the rubber polymer, and kneaded with a Banbury mixer. The kneaded rubber was rolled with a calender roll and relaxed by 10% to prepare a rubber sheet having a thickness of 7 mm.
Further, the amount of fibers protruding from the rubber composition surface, the maximum length, the minimum length, and the average (average fiber length) of the fiber length were measured to evaluate the wear resistance and durability. The results are shown in Table 2.

[Comparative Example 1]
A rubber sheet was prepared in the same manner as described above, except that no fiber was added, and the wear resistance and durability were evaluated. The results are shown in Table 2.

  The rubber composition of the present invention is extremely excellent in wear resistance while maintaining the original physical properties of rubber, and is used for various applications that require wear resistance and high durability such as tires, belts, hoses, and shoe soles. be able to. For this reason, a power transmission belt having excellent durability can be provided by using this rubber composition.

1. Rotating roll 2. Auto tensioner 3. Rubber belt

Claims (3)

  A rubber composition containing a wholly aromatic polyamide fiber in a rubber polymer, wherein the wholly aromatic polyamide fiber has a diameter of 25 to 70 μm, a length of 1.0 to 6.0 mm, and 100 parts by weight of the rubber polymer 5 to 50 parts by weight of wholly aromatic polyamide fiber with respect to the rubber composition, and in the cross section of the rubber composition, the rubber layer has a surface layer portion of 5% from the surface with respect to the total thickness of the rubber composition. 30 to 80% by weight of the total weight of the total aromatic polyamide fiber contained in the composition is present, and the total aromatic polyamide fiber having an average fiber length of 0.1 to 0.8 mm protrudes from the surface of the rubber composition. A rubber composition characterized by the above.   The rubber composition according to claim 1, wherein the wholly aromatic polyamide fiber is a copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber.   A belt using the rubber composition according to claim 1.

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