JPH0563656B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a rubber V-belt, particularly a rubber V-belt suitable for high-load transmission. (Prior Art) V-belts are used in a wide range of fields, and in recent years there has been a strong desire for V-belts that can be used in continuously variable transmissions for automobiles. Such a V-belt is made of metal V
Although metal V-belts have to be used in lubricating oil, rubber V-belts do not require this and are advantageous in terms of cost and maintenance. Continuously variable transmissions for automobiles are required to have an extremely high torque transmission capability. For example, when transmitting the maximum torque of a 1000 c.c. engine, the V-belt must withstand a side pressure of around 20 kg/cm ² . Standard rubber V-belts currently in practical use are usually used under lateral pressure conditions of 4 to 5 kg/ ^cm2 or less.
Even for high-load rubber V-belts, the limit is about 10 kg/cm ² . This is because the rubber V-belt undergoes buckling deformation under high lateral pressure and is destroyed as the V-belt generates heat. By the way, conventional rubber V-belts for transmissions are required to withstand lateral pressure and be easily bent. layer, compressed layer) is composed of rubber containing short fibers. The short fiber orientation direction (grain direction) is the belt width direction. The elastic modulus in the grain direction (vertical elastic modulus) of short fiber-containing rubber used in conventional rubber V-belts is, for example, the dynamic elastic modulus E′ _D (D is a subscript indicating the orientation direction) in a viscoelasticity test. As shown, 1~2× ¹⁰⁹ at 100℃
dynes/cm ² is common, and even high ones are 3 to 4×10 ⁹
It was dynes/ ^cm2 . When considering a rubber V-belt as an automobile transmission belt, it must be heated to 100°C in order to withstand the above side pressure.
The holding elastic layer must be made of short fiber-containing rubber having a warp modulus of elasticity of 6×10 ⁹ dynes/cm ² or more at high temperatures. Examples of the short fibers used in the short fiber-containing rubber include carbon, glass, metal (steel), nylon, polyester, vinylon, aramid, and the like. Carbon and glass fibers are cut during the dispersion and kneading process of short fibers into rubber (for example, initial length of 6 mm→
0.2mm), aspect ratio after composite (short fiber length L
The value (L/D) divided by the outer diameter D) decreases significantly, and the reinforcing function is completely lost. Metal fibers (steel) can damage processing machines such as banburys and rolls during the kneading process, and even if a V-belt can be formed using rubber containing short fibers, the metal fibers will damage the pulleys, which is a problem. There is. In addition, the outer diameter and length of synthetic organic fibers such as nylon, polyester, and vinylon can be freely selected, making it possible to reduce the amount of cutting during processing. It is also considered to have inferior properties and may melt due to friction with the pulley surface. Aramid fibers (e.g. Dupont Kevlar,
Teijinsha's HM-50) has a high elastic modulus of the fiber itself,
It has high strength, is difficult to cut during processing, and has excellent heat resistance. From the above, aramid fibers are selected as short fibers to obtain a warp elastic modulus of 6×10 ⁹ dynes/cm ² or more. For example, there is a modified Halpin-Tsai equation as an equation indicating the warp modulus of a short fiber composite. M=M ₁・(1+ABφ ₂ )/(1−Bφφ ₂ ) A=2・L/D B=(M ₂ /M ₁ −1)/(M ₂ /M ₁ +A) φ=1+φ ₂ (1− φm)/φm ² M: Composite elastic modulus M ₁ : Elastic modulus of matrix rubber without short fibers mixed in M ₂ : Elastic modulus of short fibers L: Short fiber length D: Outer diameter of short fibers φm: Short Maximum volume fraction of fibers φ ₂ : Actual volume fraction of short fibers From the above formula, in order to increase the composite elastic modulus, (1) increase the aspect ratio L/D, that is, increase L, (2) increase the volume fraction φ ₂ , that is, the blended amount of short fibers should be increased, (3) the elastic modulus M ₁ of the matrix rubber should be large, and (4) the elastic modulus of the short fibers should be large. (Problems to be Solved by the Invention) Chloroprene rubber is usually used as a rubber matrix polymer for rubber V-belts. As a result of various studies on the composite of short aramid fibers in a chloroprene rubber matrix and the performance of belts using the same, the following problems were found. Normally, a chloroprene rubber matrix is formulated with 100 parts by weight of sulfur-modified chloroprene rubber, 40 to 60 parts by weight of carbon black as a reinforcing filler, 3 to 10 parts by weight of oil such as process oil or plasticizer, and 3 to 3 parts of magnesium oxide as a crosslinking agent. 5 parts by weight, 3 to 20 parts by weight of zinc oxide, and several parts by weight of other processing aids and anti-aging agents. If a large amount of reinforcing carbon black and a small amount of oil are added to the matrix rubber in order to increase the elastic modulus of the matrix rubber, the viscosity of the unvulcanized rubber will increase, increasing the cutting of fibers during short fiber kneading, and increasing the scorch time. This causes scorching of rubber containing short fibers during kneading or sheeting. On the other hand, when a large amount of short aramid fibers are combined, the longitudinal elastic modulus increases, but the transverse elastic modulus also increases.
If a V-belt with cogs is constructed with a short fiber-containing rubber containing a large amount of such short fibers, the tensile elongation at break in the transverse direction decreases, and cracks occur from the bottom of the cogs in the early stages of belt running, resulting in early breakage of the belt. Furthermore, when this short fiber-containing rubber is subjected to a constant strain elongation fatigue test in which it is repeatedly elongated in the anti-grain direction, it breaks early. An object of the present invention is to provide a rubber V-belt for high-load power transmission that maintains lateral pressure properties and has an excellent belt life. (Means for Solving the Problems) In order to achieve the above object, the present invention provides rubber V
In the belt, 40 to 60 parts by weight of reinforcing filler, zinc oxide,
1 to 20 parts by weight (preferably 2 to 15 parts by weight) of a metal oxide vulcanizing agent consisting of at least one of magnesium oxide and lead oxide, 2 to 10 parts by weight of bismaleimide, and an appropriate amount (preferably 13 parts by weight) of aramid short fibers. It is characterized by using short fiber-containing rubber for the retention elastic layer, and having aramid short fibers arranged in the width direction of the belt.Chloroprene rubber can be either sulfur-modified or non-sulfur-modified. The sulfur-modified type is particularly desirable because it has a remarkable effect of increasing the crosslinking density of bismaleimide.If the amount of the metal oxide vulcanizing agent is less than 1 part by weight, the crosslinking of the chloroprene rubber will be reduced. If this is not done sufficiently, the matrix rubber vulcanizate will be inferior not only in heat resistance but also in vulcanized physical properties.On the other hand, if the amount is more than 20 parts by weight, when the metal oxide is zinc oxide, the stiffness of the compounded fabric will deteriorate. When using magnesium oxide, the vulcanization rate is extremely slow, and when using lead oxide, processing safety and storage stability are compromised. In the present invention, it is particularly preferable to use zinc oxide and magnesium oxide in combination, and the amount thereof is 3 to 8 parts by weight per 100 parts by weight of chloroprene rubber. N with nitrogen atoms directly bonded,
N'-linked bismaleimides and bismaleimides in which two nitrogens are bonded via an alkylene group, cycloalkylene group, oxydimethylene group, phenylene group, sulfone group, or other divalent organic group; specific examples thereof Examples include N,N'-ethylene bismaleimide, N,N'-hexamethylene bismaleimide, N,N'-(1,4-phenylene) dimaleimide, N,N'-(O-phenylene) dimaleimide, N,N' -(O-phenylene) dimaleimide, N,N'-(m-phenylene) dimaleimide,
N,N'-(2,4-tolylene)dimaleimide, N,
N'-dulylene dimaleimide, N,N'-
[4.4'(2.2'-dichlorobiphenylene)] dimaleimide, N,N'-[4.4'(2.2'-dichlorobiphenylene)] dimaleimide, N,N'-[4.4'-methylenediphenyl] dimaleimide, N,N'-(1.4-dulylene diethylene) dimaleimide, N,N'-
[4.4′-sulfonyldiphenyl]dimaleimide,
Examples include 2.6.bis(maleimidomethyl)-4-t-butylphenol and N,N'-oxydimethylene dimaleimide. Bismaleimide is used in an amount of 2 to 10 parts by weight per 100 parts by weight of chloroprene rubber. If it is less than 2 parts by weight, even if it is used in combination with a metal oxide vulcanizing agent, it will lack the effect of increasing the degree of crosslinking in the vulcanized product while ensuring the processing safety of the unvulcanized product. This is because the bloom of bismaleimide will be recognized at some point. Oil is added to impart cold resistance or kneading processability to the matrix rubber, but addition of 15 parts by weight or more lowers the elastic modulus of the matrix rubber, and the amount of carbon black must be increased to compensate for this. This deteriorates the heat aging resistance and dynamic properties of the vulcanized rubber. The amount of carbon black as a reinforcing filler is such that the elastic modulus of the matrix vulcanized rubber without adding bismaleimide is appropriate, the viscosity of the matrix unvulcanized rubber is not too high, and the scorch time is such that processing safety can be maintained. It can be decided to become If the short fiber length is too short, the aspect ratio will be low, resulting in poor reinforcing properties, while if it is too long, the fibers will become entangled with each other, resulting in poor dispersion in the rubber or breakage during the kneading process. There's a problem. The short fiber length is 2 to 10 mm, preferably 3 to 10 mm.
6mm is good. The short fibers are usually subjected to an adhesive treatment in order to impart adhesion between the short fibers and the chloroprene rubber. As an adhesive treatment for short fibers, first, aramid long fibers are deep-treated with an isocyanate compound or an epoxy compound (immersion → heat-dried), and then deep-treated with resorcinol-formalin-latex (RFL liquid).
This is then done by cutting. Alternatively, dip treatment (once only) may be performed with an isocyanate adhesive (for example, Chemlock 402 manufactured by Lord Co.). Alternatively, the untreated fibers may be first cut into a predetermined length, immersed in an adhesive treatment solution, centrifuged to remove excess solution, and then heated and dried. If the amount of aramid short fibers is too large, the bending fatigue resistance (stretching fatigue resistance) in the anti-grain direction (the direction in which the belt travels when formed into a belt) is significantly deteriorated.
Therefore, the blended amount of aramid short fibers is preferably 13% by volume or less. (Example) Examples of the present invention will be described below. Table 1 shows the rubber composition of the holding elastic layer of Examples (1) and (2) of the present invention and Comparative Examples (1) to (4), and Table 2 shows the characteristics of the matrix rubber. are shown in Table 3, and belt performance is shown in Table 4. In Tables 2 and 3, tan δ refers to the ratio E''/E' of the loss modulus E'' to the storage modulus E' in a viscoelastic solid such as vulcanized rubber. This tanδ is
It is a measure that expresses the amount of vibrational energy of a vibrating body lost as heat due to internal friction compared to the energy that can be recovered, and the larger tanδ is, the greater the loss as heat in response to dynamic stimulation. This indicates that the rubber belt generates more heat, leading to belt failure.

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[Table] As shown in Table 1, in Comparative Examples (1) and (2), the elastic modulus of the matrix rubber was increased by incorporating a large amount of carbon black as a reinforcing filler, thereby increasing the elasticity of the short fibers. The elastic modulus of the filled rubber is increased. Furthermore, in Comparative Examples (3) and (4), the elastic modulus of the rubber containing short fibers was increased by blending a large amount of short fibers with respect to ordinary matrix rubber. Comparing the matrix rubber properties, as shown in Table 2, the matrix rubbers of Comparative Examples (1) and (2) have almost the same elasticity as the matrix rubbers of Examples (1) and (2). rate (100% modulus, hardness, E′(100
℃)), but the Mooney viscosity is high, the scorch time is short, and there are problems with processing safety. or,
The tan δ is also significantly large, and it is thought that the dynamic heat generation is also large. Comparative Examples (3) and (4) are satisfactory in processing safety, but have low elastic modulus and large tan δ. Next, rubber containing short fibers will be described. After dissolving the unvulcanized rubber mixed with short fibers in toluene, the lengths of the eluted fibers were measured using a microscope, and the average value of n=60 fibers is shown in Table 3. In Comparative Examples (1) and (2), the matrix rubber had a high Mooney viscosity, so the fiber length after kneading was considerably shorter than in the other examples. As a result, the elastic modulus in the grain direction is smaller than in the example. Comparative Examples (3) and (4) have a large amount of fiber, so the elongation in the antigrain direction is small. In addition, in Examples (1) and (2), the amount of short fibers is small and the tan δ of the matrix rubber is small, so E′ (100°C) in the anti-grain direction of the rubber containing short fibers is small, tan δ is small,
E" (100℃) is small, making it a fiber-filled rubber with low bending heat generation. Furthermore, it also has a remarkable elongation fatigue life in the anti-grain direction. Next, each short fiber-filled rubber is attached to a rubber V-belt with cogs. As shown in Figure 1, the test belt was a rubber V-belt 1 with cogs, and a holding elastic layer was placed above and below an adhesive elastic layer 3 in which a cord 2 was embedded. A canvas 6 is attached to the lower surface of the lower holding elastic layer 5, and the belt width is 35 mm, the belt angle is 26 degrees, and the belt length is 780 mm.

[Table] The belt running life is based on the drive pulley with a diameter of 172 mm (rotation speed 3200 rpm, torque 3.2 Kgm) and the diameter
Wrap the test belt between the 86mm driven pulley and
The belt was run in an atmosphere of 80°C, the time until cracking was measured, and this was taken as the belt running life. However, Comparative Example (1) was set as 100 and expressed as an index. Transmissible torque was measured by winding a test belt between a driving pulley (rotation speed: 2600 rpm) with a diameter of 86 mm and a driven pulley with a diameter of 172 mm. Furthermore, the transmittable torque at low speeds (the maximum transmittable torque of the belt that can be transmitted with a slip of 3% or less) and the life index at high speeds are shown in FIGS. 2 and 3, respectively. The transmittable torque at low speed shows a correlation with the grain direction E′100°C of the rubber containing short fibers, and Examples (1) and (2) and Comparative Examples (3) and (4) have almost the same transmission ability. show. Comparative example
(1) and (2) have poor communication ability. On the other hand, when comparing the life index at high speed at the same transmittable torque, it is clear that the embodiment of the present invention is significantly superior to the comparative example. The adhesive elastic layer is made of rubber having a dynamic elastic modulus of 5×10 ⁸ dynes/cm ² and a JISA hardness of 89°. Therefore, by adding bismaleimide to the matrix rubber formulation of chloroprene rubber, the crosslinking density of the matrix rubber can be increased and the elastic modulus can be increased. is not worse than when no bismaleimide is added, and therefore a matrix rubber with excellent processing safety, high modulus of elasticity, and excellent dynamic properties can be obtained. Furthermore, when short fibers are mixed into the matrix rubber, the Mooney viscosity of the matrix rubber can be set low, and the short fibers are less likely to be cut. In order to obtain short fiber-containing rubber with the same elastic modulus in the grain direction, the amount of short fibers combined is small, and the short fiber-containing rubber has excellent elongation and elongation fatigue life in the anti-grain direction. In addition, a short fiber-containing rubber with a small tan δ can be obtained, allowing E″≒E′×tan δ to be small, and bending heat generation is small.By combining aramid short fibers, a rubber with short fibers of 6×10 ⁹ dynes/cm ² or more can be obtained. Vertical elastic modulus (100
℃) short fiber-containing rubber is obtained. (Effects of the Invention) In the present invention, the holding elastic layer is formed using short fiber-containing rubber that has a large elastic modulus in the grain direction and excellent properties in the anti-grain direction, so high torque transmission is possible and high With a long service life, it can be applied to automobile transmissions.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a rubber V-belt according to an embodiment of the present invention, and FIGS. 2 and 3 are illustrations of test results. 1... Rubber V-belt, 2... Cord, 3... Adhesive elastic layer, 4, 5... Holding elastic layer.

Claims (1)

[Claims] 1 A belt in which a holding elastic layer is located above and below an adhesive elastic layer in which a cord is embedded, and the holding elastic layer is made of 100 parts by weight of chloroprene rubber, 40 to 60 parts by weight of reinforcing filler, and zinc oxide. , 1 to 20 parts by weight of a metal oxide vulcanizing agent consisting of at least one of magnesium oxide and lead oxide, and 2 to 20 parts by weight of bismaleimide.
A rubber V comprising short fiber-containing rubber containing 10 parts by weight and an appropriate amount of aramid short fibers, and characterized in that the aramid short fibers are arranged in the width direction of the belt.
belt.