JPH0645221B2 - Toothed belt - Google Patents

Description

TECHNICAL FIELD The present invention relates to a toothed belt useful as a (timing) belt, a bicycle belt, and the like. More specifically, the present invention relates to a toothed belt having a small compression set, excellent wear resistance, running stability, strength and the like.

[Prior Art] In recent years, most precision toothed belts made of urethane rubber reinforced with long fibers (continuous fibers) are manufactured. They have the advantage of being very highly elastic and durable. However, it cannot respond flexibly to changes in growth,
Alternatively, there is a problem in that the manufacturing process is complicated and thus costly.

On the other hand, the present inventors have proposed a rubber molded product using short fiber reinforced rubber (Japanese Patent Application No. 2-106715). This solves the above problems without impairing the advantages.

[Problems to be Solved by the Invention] The present invention further develops the above-mentioned invention and has high elasticity, small compression set, excellent wear resistance, running stability, and the like.
An object is to provide a toothed belt that can be easily manufactured.

[Means for Solving the Problems] In order to achieve the above object, the belt has a laminated structure of a tooth profile and a back surface, and the belt tooth profile uses a rubber having a small compression set and excellent wear resistance, It has been found that the use of a rubber further containing short fibers in order to give high strength to the back surface of the belt gives excellent results, and thus the present invention has been accomplished.

That is, the present invention, the tooth profile portion (a) is a sulfur and / or peroxide vulcanized rubber containing no short fibers, and the back surface portion (b) is a sulfur and / or peroxide vulcanized rubber containing short fibers, Provided is a toothed belt having a laminated structure of a tooth profile (a) and a back surface (b).

As a preferred embodiment of the toothed belt of the present invention, for example, the tooth profile portion (a) is (I) 100 parts by weight of base rubber, (II) α, β
10 to 50 parts by weight of unsaturated fatty acid, 10 to 50 parts by weight of (III) metal oxide, hydroxide or carbonate, and (I
V) A vulcanized rubber of a rubber composition comprising 0.5 to 5 parts by weight of an organic peroxide, wherein the back surface part (b) comprises the components (I) to (IV) and further (V) short fibers 5 to 5 A vulcanized rubber of a rubber composition obtained by mixing 30 parts by weight, and a toothed belt having a structure in which a toothed portion (a) is laminated on a back surface portion (b).

As the base rubber (I) used in the present invention, all rubber components conventionally used in rubber compositions can be used. For example, isoprene rubber, natural rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber and hydrogenated nitrile rubber, ethynylene propylene rubber, chloroprene rubber, butyl rubber, urethane rubber, acrylic rubber, silicone rubber, and the like, one of which is used. The above may be used. A particularly preferred base rubber (I) is cis-1,4-polybutadiene having a cis structure of 90% or more.

As the α, β-unsaturated fatty acid (II) used in the present invention, α, β-monoethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms is suitable. Examples of such substances include methacrylic acid, acrylic acid, itaconic acid, crotonic acid and the like, and at least one of them is used.
The blending amount of the α, β-unsaturated fatty acid (II) is 10
0 to 50 parts by weight, preferably 20 to
40 parts by weight. If the amount is less than 10 parts by weight, sufficient strength cannot be obtained. If it exceeds 50 parts by weight, the composition becomes hard and the workability becomes poor. Also, the moldability is poor.

The metal oxide, hydroxide or carbonate (III) used in the present invention (hereinafter sometimes simply referred to as “metal compound (III)”) has the above-mentioned α, β
-Forms a metal salt of unsaturated fatty acid (II), which serves as a rubber cross-linking agent. The metal species is generally a divalent metal, preferably zinc, magnesium or the like, but other metals such as sodium, lithium or aluminum may be used. The compounding amount of the metal compound (III) is 10 to 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the base rubber (I).

Incidentally, instead of blending each of the above fatty acid (II) and the metal compound (III) in the rubber composition, or in combination, the fatty acid (II) and the metal compound (III) are preliminarily prepared from the metal of the fatty acid (II). A salt may be formed and incorporated into the rubber composition. α,
The compounding amount of the metal salt of β-unsaturated fatty acid is based on the base rubber (I) 1
20 to 100 parts by weight, especially 40 to 80 parts by weight
Parts by weight are preferred.

Organic peroxide (IV) compounded in the rubber composition of the present invention is perbenzoic acid, benzoyl peroxide, cumene peroxide,
Dicumyl peroxide and the like can be mentioned. Dicumyl peroxide is preferred. The compounding amount of the organic peroxide is 0.5 to 5.0 parts by weight based on 100 parts by weight of the base rubber (I). If it is less than 0.5 part by weight, crosslinking of the metal salt of α, β-unsaturated fatty acid is unlikely to occur, and if it exceeds 5.0 parts by weight, the molded product becomes brittle, which is not practical.

The belt tooth profile (a) is formed by vulcanizing and molding a rubber composition containing the compounding components (I) to (IV).

The back surface part (b) of the belt is formed by vulcanizing and molding a rubber composition containing, in addition to the above-mentioned distribution components (I) to (IV), a short fiber (V) as a reinforcing agent in order to impart high strength. To be done.

Examples of the short fibers (V) include carbon fibers, alumina fibers, aromatic polyamide fibers, silicon carbide fibers, silica fibers, boron fibers, potassium titanate fibers, polyamide fibers, polyester fibers, polyvinyl alcohol fibers, polyacrylic fibers, Typical synthetic fibers such as polyvinyl chloride fiber, polyvinylidene chloride fiber, polyethylene fiber, polypropylene fiber, polyurea fiber and natural fibers can be used. It is more preferable to perform heat-threading treatment and adhesion treatment for imparting strength to these fibers. Polyamide (particularly nylon) fiber, polyacrylic fiber and the like are preferable. The fiber length (L) of the short fibers is from 10 μm to
It is 30 mm, preferably 1 to 10 mm. Further, the ratio (L / D) of the fiber length L and the fiber diameter D is 10 or more, particularly 50 to
1000 is preferred. If the ratio is less than 10, the reinforcing property of the short fiber rubber in the roll circumferential direction is poor.

The amount of the short fiber (V) blended in the rubber composition is the base rubber (I) 1
5 to 30 parts by weight, preferably 10 to 100 parts by weight
20 parts by weight. If it is less than 1 part by weight, the strength will be insufficient, and if it exceeds 100 parts by weight, problems such as moldability will occur.

The weight ratio of the rubber composition used for the toothed portion (a) and the rubber composition used for the back surface portion (b) is not limited, but may be, for example, 50:50 to 20:80.

In the preparation of the rubber composition used for the tooth portion (a) or the back surface portion (b), the kneading method may be an ordinary method (for example, roll kneading, kneader kneading, Banbury kneading, etc.). It is preferable to perform () by applying a shearing force in a fixed direction. By doing so, the rubber is oriented in a certain direction, and a large strength is obtained in that direction. For example, in the case of a roll, rubber is arranged in the circumferential direction of the roll, and when an extruder is used, the extrusion direction is the same as the orientation direction. Further, according to the research of the present invention, it was found that not only the strength but also the elongation has a high orientation, and similarly to the orientation of the strength, it extends too much in the orientation direction and greatly extends in other directions. Therefore, at the time of vulcanization molding, a belt excellent in strength and stretchability can be obtained by putting it in a mold so that its orientation matches the rotational direction of the belt.

The method for producing the toothed belt of the present invention is not limited, but, for example, one of the above-mentioned unvulcanized rubber compositions used for the tooth profile portion (a) or the back surface portion (b) is first (semi) vulcanized and molded. , Tooth profile (a)
Alternatively, either the back surface part (b) is first (semi) molded. Then, the remaining one unvulcanized rubber composition is combined with the above (semi) vulcanized rubber and integrally vulcanized and molded to obtain a two-layer structure of the present invention having a toothed portion (a) and a back surface portion (b). The toothed belt of is obtained. Molding (vulcanization) is performed under conventionally known conditions. Generally, it is carried out in a mold at a temperature of 140 to 170 ° C. for 10 to 40 minutes.

Alternatively, the tooth profile portion (a) and the back surface portion (b) are separately vulcanized and molded, and then bonded together by a common method such as bonding to obtain the tooth belt of the present invention.

The shape of one embodiment of the toothed belt of the present invention obtained as described above is schematically shown in FIG.

As shown in FIG. 1, the toothed belt of the present invention has a tooth profile portion.
(a) and the back surface part (b) containing the short fibers (V) form a two-layer structure. The shape and size of the tooth profile (a), the layer thickness, etc. may be appropriately selected according to the purpose of use of the belt. For example, it may have an acute tooth profile as shown in FIG. 1 or a curved tooth profile. The layer thickness of the back surface portion (b) is not particularly limited and may be appropriately selected according to the purpose of use.

EFFECTS OF THE INVENTION According to the present invention, it is possible to easily manufacture a toothed belt having high elasticity, small compression set, and excellent wear resistance, running stability, and the like.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples.

(Example 1) With the composition shown in Table-1, each of the rubber compositions of the tooth profile portion (a) and the back surface portion (b) was kneaded by applying a shearing force in the circumferential direction with a roll. The obtained rubber composition of the tooth profile (a) is
It was molded in the form of a tooth profile at 30 ° C. for 30 minutes. Next, this molded rubber and the rubber molded product of the back part (b) were combined and
The toothed belt of the present invention was obtained by integrally molding at 0 ° C. for 30 minutes.

[Brief description of drawings]

 FIG. 1 shows a sectional view of the toothed belt of the present invention. a: Tooth profile, b: Rear surface, V: Short fiber.

Claims (3)

[Claims] 1. The sulfur and / or tooth-shaped portion (a) does not contain short fibers.
Or a peroxide vulcanized rubber, the back surface (b) is sulfur and / or peroxide vulcanized rubber containing short fibers, and a toothed belt having a laminated structure of a tooth profile (a) and a back surface (b) . 2. The tooth profile (a) comprises 100 parts by weight of (I) base rubber, (II) 10 to 500 parts by weight of α, β-unsaturated fatty acid, and (I)
II) Metal oxides, hydroxides or carbonates 10 to 50
A vulcanized rubber of a rubber composition comprising 1 part by weight and (IV) 0.5 to 5 parts by weight of an organic peroxide, wherein the back surface part (b) comprises the components (I) to (IV) and further (V). The toothed belt according to claim 1, which is a vulcanized rubber of a rubber composition containing 5 to 30 parts by weight of short fibers. 3. The fiber length (L) of the short fibers (V) is 10 μm to 30.
mm and ratio (L / D) of fiber length (L) to fiber diameter (D)
Is 10 or more, The toothed belt according to claim 1.