JPS6255536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides high melting point isotactic poly-α-
This invention relates to a novel method for producing a rubber composition with high elastic modulus, excellent tear resistance and bending resistance, which is obtained by melt blending olefin with polyisoprene rubber at a temperature above its melting point. In recent years, vulcanized rubber having a higher elastic modulus than the commonly used vulcanized rubber has become desired in certain fields. In this case, the physical properties of the rubber other than the elastic modulus are the same as those of conventional vulcanized rubber,
It is desirable to have excellent processability when manufacturing vulcanized rubber products. A method of increasing the elastic modulus of vulcanized rubber is to mix a high elastic modulus substance (inorganic substance, resin, etc.) with rubber in the form of powder or fiber. However, with this method, the dispersibility of the high modulus material and the interfacial adhesion between the rubber and the high modulus material are insufficient, so when stress is applied to the rubber product, the interface between the rubber and the high modulus material may be destroyed. Therefore, it has fatal defects in vulcanized physical properties such as tensile strength, tear resistance, and bending resistance. For example, among diene rubbers, polyisoprene rubber, which has the best bending resistance, and natural rubber are widely used for radial tires. However, when the modulus of elasticity is high, there is a problem that the vulcanized physical properties, particularly the bending resistance, deteriorate. The object of the present invention is to improve the above-mentioned drawbacks of rubber reinforced with high modulus materials. In view of these circumstances, the inventors of the present invention have conducted intensive studies on the method of mixing high-melting point isotactic poly-α-olefin with rubber, and have found that by micro-dispersing it using a specific method, high elastic modulus and tear resistance can be achieved. It has been discovered that a rubber composition with excellent bending resistance can be advantageously produced industrially, and the present invention has been achieved. That is, the present invention is a method for producing a rubber composition having a high elastic modulus, which comprises mechanically mixing isotactic poly-α-olefin with a high melting point and a particle size of 1000μ or less with polyisoprene rubber in a molten state. be. The present invention will be explained in detail below. The high melting point isotactic poly-α-olefin used in the present invention is an isotactic poly-α-olefin having a melting point of 150°C or higher, preferably 160°C or higher. If the melting point is lower than 150°C, it will melt under the rubber vulcanization conditions and good physical properties will not be obtained.
Specific examples include isotactic polypropylene, polyallylcyclopentane, polyallylcyclohexane, polyallylbenzene, poly-
(3-methyl-1-butene), poly(3-cyclohexyl-1-butene), poly(4-phenyl-1)
-butene), poly(3-methyl-1-pentene),
Poly(4-methyl-1-pentene), poly(4-
Examples include copolymers of α-olefins and other α-olefins, such as copolymers of (methyl-1-hexene) and propylene and allylbenzene, and copolymers of (3-methyl-1-butene) and 1-butene. It will be done. Among these, isotactic polypropylene and poly(4-methyl-1-pentene) are preferred.
In particular, it is preferable to use isotactic polypropylene for applications that require tensile strength, and poly(4-methyl-1-pentene) for applications that require tear resistance and bending resistance. Poly(4-methyl-1-pentene) can be synthesized, for example, using a Ziegler-Natsuta catalyst consisting of triethylaluminum-tita tetrachloride (for example, Brit.
P.944055 (1963)). Melting point is above 200℃. Isotactic polypropylene is also commonly polymerized with, for example, Ziegler-Natsuta catalysts (e.g.
G. Natsuta, “Stereoregular Polymerization,” Pergamon Press. (1967)). Melting point is 150℃
In this case, the isotactic polymer is 90% or more. Moreover, it is preferable to use one in which the atactic polymer is separated and removed. In the present invention, the rubber to be mixed with the isotactic poly-α-olefin having a high melting point is polyisoprene rubber, and specific examples include cis-1,4-polyisoprene rubber and natural rubber. The mixing method of the present invention is based on the isotactic polyurethane.
This method involves mechanically kneading α-olefin and rubber at a temperature higher than the melting point of the isotactic poly-α-olefin. Here, the mechanical mixing method refers to kneading processing using various processing machines such as extruders and kneaders, and by this means it is possible to micro-disperse the isotactic poly-α-olefin into the rubber. is important. However, even if the above-mentioned polymer is mixed with rubber in its commonly used form and then mechanically kneaded at a temperature higher than the melting point of the polymer, the rubber composition intended by the present invention cannot be obtained. As in the present invention, isotactic poly-α-olefin and rubber are mechanically kneaded in a molten state to form an isotactic poly-α-olefin.
To microdisperse olefin, the average particle size is
It is essential to use isotactic poly-α-olefin with a particle size of 1000 μm or less.
In other words, when kneading rubber at the temperature at which isotactic poly-α-olefin melts, the viscosity of the rubber is much lower than the viscosity at normal processing temperatures (50 to 100°C), and the kneading effect is also reduced. So,
In order to compensate for this kneading effect, it is necessary to use isotactic poly-α-olefin that has been made into fine particles in advance. Polymers with an average particle size of 10 to 500 microns are usually used. The kneading temperature is preferably between the melting point of the isotactic poly-α-olefin and +50°C, and more preferably kept at 250°C or less in view of the deterioration of the rubber. There are various methods for atomizing isotactic poly-α-olefin, including mechanically pulverizing it, adding a surfactant to the swollen state in a solvent, and then pulverizing it under mechanical shearing force. After that, the method of evaporating the solvent to form fine particles, the method of sorting from the slurry polymer after polymerization, etc. are industrially advantageous. The kneading time required to micro-disperse the isotactic poly-α-olefin in the rubber is a commonly used kneading time, and there is no need for a particularly long kneading time. Further, when kneading is carried out at a temperature higher than the melting point of the isotactic poly-α-olefin as in the present invention, it is desirable to add an anti-aging agent to prevent thermal deterioration of the rubber. In this case, the anti-aging agent used may be a heat-resistant anti-aging agent commonly used, and the amount added is preferably 0.1 to 5% by weight. There is no limit to the mixing ratio of high melting point isotactic poly-α-olefin and rubber, but high modulus (represented by 100% tensile stress and 300% tensile stress)
In order to obtain a vulcanized rubber with excellent tear resistance and bending resistance, the content of isotactic poly-α-olefin in the rubber composition is preferably 2 to 40% by weight. Particularly preferred is a range of 3 to 25% by weight. If the content is less than 2% by weight, the elastic modulus (100%
Tensile stress (represented by 300% tensile stress), tear resistance, and bending resistance improvement effect is small, and 40% by weight
If it exceeds this value, workability will deteriorate. The rubber composition obtained by the present invention can be used alone or in combination with other rubbers for rubber applications. Other rubbers used here include polyisoprene rubber, polybutadiene rubber, styrene-butadiene rubber, ethylene-propylene rubber, butyl rubber, and diene rubber is particularly preferred. When the rubber composition of the present invention is used for rubber applications, reinforcing agents and compounding agents that are commonly incorporated into rubber can be used. Furthermore, the processing and vulcanization methods used are those commonly used for rubber. Next, the present invention will be specifically explained with reference to Examples. Example 1 Poly(4-methyl-1-pentene) (manufactured by ICI,
(melting point 235℃) powdered to an average particle size of 28μ, 10 parts by weight, IR-2200 (polyisoprene rubber manufactured by Japan Synthetic Rubber Co., Ltd., cis 1,4-content 98%,
ML ¹⁰⁰ °C ₁₊₄ 82) 90 parts by weight and 1 part by weight of 2,2'-methylenebis(4-methyl-6-t-butylphenol) as an antiaging agent were added to an extruder (inner diameter 25 mm).
The mixture was kneaded at 240°C. After cooling the kneaded product to room temperature, it was compounded according to the recipe shown in Table 1. Next, press vulcanization was performed at 145° C. for 20 minutes, and then a tensile test, a tear test, and a bending (crack growth) test were performed according to JISK6301. The results are shown in Table 3.

[Table] It can be seen that this rubber composition has excellent bending resistance and high elastic modulus. Example 2 Poly(4-methyl-1-pentene) of Example 1
The treatment was carried out in the same manner as in Example 1, except that the average particle diameter of the sample was changed to 230μ. A high modulus rubber composition having excellent bending resistance is obtained. Examples 3 and 4 Poly(4-methyl-1-pentene) of Example 1
The amount was changed to 5% by weight and 15% by weight. A high modulus rubber composition having excellent bending resistance is obtained. Example 5 10 parts by weight of polypropylene (Mitsubishi Yuka Co., Ltd. Noblen, melting point 165°C) powdered to an average particle size of 32μ, 90 parts by weight of IR-2200, and the anti-aging agent 2,2'-methylenebis(4- Methyl-6-t-
Butylphenol) 1 part by weight was added to an extruder (inner diameter 25
mm) at 200°C. This kneaded product was blended and vulcanized in the same manner as in Example 1, and the physical properties were measured. Table 3 shows the results. It can be seen that this rubber composition has high tensile strength and high elasticity without decreasing tear resistance. Example 6 The average particle diameter of the polypropylene in Example 5 was 210
Changed to μ. A rubber composition with high tensile strength and high modulus of elasticity is obtained. Example 7 The polypropylene content of Example 5 was changed to 15% by weight. A rubber composition with high tensile strength and high modulus of elasticity is obtained. Example 8 Natural rubber was used in place of IR-2200 in Example 1. The formulation and vulcanization conditions were the same as in Example 1,
Physical properties were measured. Table 3 shows the results. A rubber composition having a high elastic modulus with excellent bending resistance is obtained. Example 9 Instead of the IR-2200 used in Example 5, natural rubber was used for measurement. The results are shown in Table 3.
A high modulus rubber composition having high tensile strength without any decrease in tear resistance can be obtained. Comparative Example 1 and Comparative Example 5 Synthetic polyisoprene rubber (IR-2200) and natural rubber were compounded and vulcanized according to the formulation shown in Table 2. The vulcanization conditions were 145°C for 20 minutes for both synthetic polyisoprene and natural rubber. Table 2 Polymer 100 parts by weight Carbon black ISAF 50 Aromatic oil (JIS AROMA) 10 Zinc Flower 5 Stearic acid 1 Anti-aging agent (810-NA) 1 Vulcanization accelerator (Z) 1.5 Sulfur 2.5 Comparative example 2 Implementation Poly(4-methyl-1-pentene) of Example 1
The average particle diameter was changed to 2800μ. Comparative Example 3 The average particle diameter of the polypropylene of Example 5 was 3300
I replaced it with μ. Comparative example 4 Carbon black (ISAF) 10 parts by weight, IR-
2200 90 parts by weight and 2,2'-methylenebis(4
-Methyl-6-t-butylphenol) was kneaded under the same conditions as in Example 1, and then the first
Compounding was performed based on the formulation shown in the table, and physical properties were measured. Comparative Example 6 10 parts by weight of carbon black (ISAF) and 90 parts by weight of natural rubber were mixed with 1 part by weight of 2,2'-methylenebis(4-methyl-6-t-butylphenol) under the same conditions as in Example 1. Based on the formulation shown in Table 1, the mixture was processed and the physical properties were measured. Comparative Example 7 10 parts by weight of poly(4-methyl-1-pentene) with an average particle size of 230μ, 90 parts by weight of IR-2200, and
2246 (antiaging agent) 200 parts by weight using an extruder
Kneaded at ℃. This kneaded product was blended and vulcanized in the same manner as in Example 1, and its physical properties were measured. Comparative Example 8 10 parts of polypropylene with an average particle size of 210μ and IR
-2200 90 parts by weight were kneaded at a roll temperature of 130°C. This kneaded product was blended according to the recipe shown in Table 2 and vulcanized.

【table】

Claims (1)

[Claims] 1. A method for producing a rubber composition having a high elastic modulus, which comprises mechanically mixing an isotactic poly-α-olefin with a high melting point with polyisoprene rubber at a temperature above its melting point. . 2. The method for producing a rubber composition according to claim 1, wherein the isotactic poly-α-olefin with a high melting point has a particle size of 1000 μm or less. 3. The method for producing a rubber composition according to claim 1, wherein the isotactic poly-α-olefin with a high melting point is poly(4-methyl-1-pentene). 4. The method for producing a rubber composition according to claim 1, wherein the isotactic poly-α-olefin having a high melting point is isotactic polypropylene. 5. The method for producing a rubber composition according to claim 1, wherein the content of the isotactic poly-α-olefin with a high melting point in the rubber composition is 2 to 40% by weight.