JPS6255537B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, a high modulus of elasticity is achieved by stretching polyisoprene rubber or a mixture of polyisoprene rubber or a rubber containing polyisoprene rubber as a main component in which isotactic poly-α-olefin with a high melting point is stretched in a specific temperature range. The present invention relates to a method of manufacturing a rubber composition having the present invention. Resource saving and energy saving have become important themes in industry in recent years, and the rubber industry is also aiming for lighter weight and higher performance. Therefore, vulcanized rubber having a higher elastic modulus than the commonly used vulcanized rubber has become desired in specific fields. In this case, it is desirable that the physical properties other than the elastic modulus are comparable to those of conventional vulcanized rubber, and that the processability in manufacturing rubber products is excellent. A method of increasing the elastic modulus of vulcanized rubber is to mix a substance having a high elastic modulus (carbon black, resin, etc.) into a powder or fiber form with rubber. However, in this method, the dispersibility of the high-modulus substance and the interfacial adhesion between the rubber and the high-modulus substance are insufficient, so when stress is applied to the vulcanized rubber, the interface between the rubber and the high-modulus substance may be destroyed. This results in a decrease in vulcanized physical properties such as tensile strength, tear resistance, and bending resistance. For example, even in polyisoprene rubber, which is the rubber with the best bending resistance among diene rubbers and is widely used for radial tires, when increasing the amount of carbon black to increase the elastic modulus, the vulcanizate property, especially the resistance There is a problem that flexibility decreases. Furthermore, a composition in which short fibers of highly crystalline 1,2-polybutadiene are microdispersed in rubber is known (Japanese Patent Application Laid-Open No. 55-23150);
Since 2-polybutadiene is highly unsaturated, even if fracture resistance and reinforcing properties are improved, there is a problem with thermal stability, which is undesirable. In order to improve the above-mentioned drawbacks of conventional reinforced rubbers made of high-modulus materials, the present inventors have conducted intensive studies on new reinforcing agents and methods for mixing them. It has been found that a rubber composition with high elastic modulus and excellent fracture properties can be obtained by micro-dispersing the rubber composition using this method. For example, a method in which a rubber solution is mixed with a suspension dispersion of finely powdered high-melting-point isotactic poly-α-olefin with an average particle size of 200μ or less in an organic solvent by stirring, and then the polymer mixture is recovered (unexamined patent application No. 166242 (1982), patent application No. 166242 (1982)
69570), high melting point isotactic poly-α-
There is a method in which a dispersion obtained by applying mechanical shearing force to olefin in a swollen state in an organic solvent is mixed with a rubber solution (Japanese Patent Application Laid-Open No. 56-151741, Japanese Patent Application No. 55450-1983). As a result of further studies on such rubber compositions, the present inventors found that a mixture of polyisoprene rubber produced by the various methods described above and high melting point isotactic poly-α-olefin was processed into a processing machine such as a roll or an extruder. When processed under specific conditions using rubber compositions, the green strength of the unvulcanized product is further improved, the vulcanized product has a high modulus of elasticity, and a rubber composition with significantly improved fracture properties can be industrially advantageously produced. They discovered this and arrived at the present invention. That is, the present invention uses a mixture of polyisoprene rubber or a rubber containing polyisoprene rubber as a main component in which a high melting point isotactic poly-α-olefin having a melting point of 150° C. or higher is dispersed to an average particle size of 50 μm or less. This is a method for producing a rubber composition having a high elastic modulus, which is characterized by stretching at a temperature between 65°C lower than the melting point of poly-α-olefin and 20°C higher than the melting point. The present invention will be explained in detail below. The polyisoprene rubber of the present invention is a high cis-1,4-polyisoprene rubber or natural rubber having a cis-1,4 content of 90% or more. Rubbers mixed with polyisoprene rubber include polybutadiene rubber,
Examples include diene rubber such as styrene-butadiene rubber, ethylene-propylene rubber, butyl rubber, and mixtures thereof, but diene rubber is preferred because of ease of co-vulcanization. The content of polyisoprene rubber in the rubber mixture is at least 50%. 50%
If it is smaller, the fracture characteristics will be worse. The high melting point isotactic poly-α-olefin used in the present invention has a melting point (20
Peak temperature when scanning at °C/min)
It is an isotactic poly-α-olefin having a temperature of 150°C or higher, preferably 160°C or higher. Melting point is 150℃
If it is less than that, the rubber will melt under the vulcanization conditions and good physical properties will not be obtained. Specific examples include isotactic polypropylene (hereinafter, isotactic may be omitted and simply referred to as 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(3-methyl- 1-hexene), poly(4-methyl-1-hexene), polyvinylcyclopentane, a copolymer of propylene and allylbenzene, and a copolymer of 3-methyl-1-butene and 1-butene. Copolymers of other α-olefins may be mentioned. Among these, polypropylene and poly(4-methyl-1-pentene) are preferred. Poly(4-methyl-1-pentene) can be synthesized, for example, using a Ziegler-Natsuta catalyst consisting of triethylaluminum-titanium tetrachloride. Melting point is above 200℃. Isotactic polypropylene is also commonly polymerized using, for example, Ziegler-Natsuta catalysts. The melting point is 150℃ or higher and the isotactic polymer content is 90% or higher. Preferably, the isotactic polymer is separated and removed. A method for producing a mixture in which high melting point isotactic poly-α-olefin is microdispersed in polyisoprene rubber with an average particle size of 50 μm or less by directly crushing isotactic poly-α-olefin to a particle size of 50 μm or less. A method of mixing high melting point isotactic polyisoprene rubber with polyisoprene rubber.
A method of mixing a dispersion obtained by applying mechanical shearing force to α-olefin in a swollen state in an organic solvent and a rubber solution. Both wet and dry methods, including mechanical mixing methods, can be used. Particle size is 40
μ or less is more preferable. If the particle size exceeds 50μ, the particles will not be sufficiently dispersed in the rubber, so even if stretched, the properties will not be improved and the processability of the rubber composition will be poor. The high melting point isotactic poly-α-olefin produced by the various methods described above has an average particle size of 50.
The mixture microdispersed in polyisoprene rubber at a temperature of 65°C lower than the melting point of high melting point poly-α-olefin, preferably lower than the melting point.
between 55°C below and 20°C above the melting point.
More preferably, after stretching at a temperature between 55°C below the melting point and the melting point, the stretched product is returned to normal rubber processing temperature, and then inorganic fillers, softeners, plasticizers, colorants, anti-aging agents, etc. Rubber chemicals such as a vulcanizing agent, a vulcanizing agent, and an accelerator are kneaded and vulcanized. In addition, high melting point isotactic poly-α-
After kneading an inorganic filler, a softener, a plasticizer, a coloring agent, an anti-aging agent, etc. into a mixture of olefin and polyisoprene rubber, it is stretched in the above temperature range,
The same result can be obtained even if a vulcanizing agent and accelerator are then added and vulcanization molded. In the present invention, stretching processing refers to applying mechanical shearing force to the isotactic poly-α in the rubber composition using an extruder with rolls or dies.
-Refers to the process of imparting orientation to olefin. The greater the orientation, the higher the elastic modulus. Therefore, it is desirable to process the material under molding conditions with a large shearing force, that is, a large processing strain, and it is industrially advantageous to use, for example, a roll, a calender, an extruder, or the like. If the temperature is 65°C or more below the melting point of the isotactic poly-α-olefin, the isotactic poly-α-olefin will not soften even if stretched under forming conditions with large processing distortion.
Orientation is not possible and high elastic modulus cannot be obtained. In addition, when stretched at a temperature exceeding the melting point of isotactic poly-α-olefin plus 20°C,
The isotactic poly-α-olefin that has been stretched once is annealed and no longer exhibits a sufficient orientation effect, making it impossible to obtain a molded product with a higher modulus of elasticity. For example, in the case of polypropylene, it is preferable to stretch at a temperature of 110 to 180°C. There is no particular restriction on the mixing ratio of high melting point isotactic poly-α-olefin in the rubber composition, but vulcanization with high elastic modulus (expressed as 100% tensile stress) and excellent tear resistance and bending resistance To obtain rubber, isotactic polyα-
The content of olefins is between 2 and 40% by weight, particularly preferably between 3 and 25% by weight. If it is less than 2% by weight, a high elastic modulus cannot be obtained, and if it exceeds 40% by weight, workability will be poor. The rubber composition obtained according to the present invention can be used alone or in combination with other rubbers for rubber applications. Other rubbers used here are polyisoprene rubber,
Examples include polyptadiene rubber, styrene-butadiene rubber, ethylene-propylene rubber, butyl rubber, natural rubber, and diene rubber is particularly preferred. The rubber composition produced by the method of the present invention has high green strength as an unvulcanized product, and the vulcanized product has a high modulus of elasticity and excellent fracture properties such as resistance to flex crack growth, so it is suitable for rubber applications. It can be used frequently. Next, the present invention will be explained in detail with reference to Examples. Example 1 Isotactic polypropylene (Mitsubishi Yuka Co., Ltd.)
20 per part by weight of Noblen, melting point 165℃)
Part by weight of toluene was added and heated to dissolve. After cooling, the swollen polymer was stirred for 15 minutes using a high-speed mixer (13,000 rpm) and crushed by applying shear force. While mixing a predetermined amount of this mixture with a propeller stirrer, use IR-2200 (polyisoprene rubber manufactured by Japan Synthetic Rubber Co., Ltd., cis-1,4 content 98%) so that the polypropylene content is 10% by weight.
ML ¹⁰⁰ °C ₁₊₄ 82) n-hexane solution (solid concentration
Ten
% by weight) was added and stirring was continued for 30 minutes.
The mixture was poured into a large amount of methanol containing a small amount of 2,6-di-t-butyl-p-cresol and coagulated. The average particle size of polypropylene in this rubber composition was 0.28μ. After stretching the coagulated product at a roll temperature of 160℃
After cooling to .degree. C., kneading and vulcanization molding were performed based on the formulation shown in Table 1. Physical property measurements are shown in Table 3. Table 1 Polymer 100 parts by weight Carbon black ISAF 50 Aromatic oil JSR AROMA 10 Zinc Flower 5 Stearic acid 1 Antioxidant 810-NA 1 Vulcanization accelerator CZ 1.5 Sulfur 2.5 Vulcanization conditions 145℃ x 25 minutes Example 2 An experiment was conducted by changing the roll temperature during the stretching process in Example 1 to 130°C. Example 3 An experiment was conducted by changing the roll temperature during the stretching process of Example 1 to 170°C. Examples 4 and 5 The polypropylene content of Example 1 was increased to 5.15% by weight.
I experimented by changing it to . Example 6 2,2'-methylenebis(4-methyl-6-t-butylphenol) (anti-aging agent) was added to 100 parts by weight of a mixture of 10% by weight polypropylene powder with an average particle size of 35μ and 90% by weight of IR-2200. 1 part by weight was added and kneaded at 200°C using an extruder (25 mmφ). This kneaded product was stretched at a roll temperature of 160°C, and then blended and vulcanized according to the formulation shown in Table 2. Table 3 shows the physical property measurement results. Table 2 Polymer/2,2'-methylenebis(4-methyl-
6-t-butylphenol) = 100/1
101 parts by weight Carbon black ISAF 50 Aromatic oil JSR AROMA 10 Zinc Flower 5 Stearic acid 1 Antioxidant 810-NA 1 Vulcanization accelerator 1.5 Sulfur 2.5 Vulcanization conditions 45℃ x 25 minutes Example 7 Average particle size 30μ 10% by weight of polypropylene powder
Table 1 shows 100 parts by weight of a mixture of 90% by weight of IR-2200 and
After kneading the recipe shown in at a roll temperature of 160℃,
It was stretched and vulcanized at the same temperature. Table 3 shows the physical property measurement results. Example 8 IR-2200 of Example 6 was mixed with NR#1 (natural rubber,
Table 3 shows the results of experiments performed by changing to RSSNo1). Example 9 IR-2200 of Example 6 was changed to IR-2200/BRO1=70/
30 (wt%) (BRO1 Polybutadiene rubber cis-1,4 content 97% ML manufactured by Japan Synthetic Rubber Co., Ltd. ¹⁰⁰ °C ₁₊₄ 44)
I experimented by changing it to . The results are shown in Table 3. Comparative Examples 1 and 2 Experiments were conducted by changing the roll temperature during stretching in Example 1 to 80°C or 200°C. The measurement results are shown in Table 3. Comparative Examples 3 and 4 IR-2200 alone or IR-2200/carbon (ISAF) = 90/10 (wt%) was stretched at a roll temperature of 60°C, cooled to 80°C, and then summarized in Table 1. Compounding processing and vulcanization molding were performed based on the compounding recipe shown in Table 1. Table 3 shows the physical property measurement results. Comparative Example 5 The average particle diameter of the polypropylene of Example 7 was 210
Table 3 shows the results of an experiment in which μ was changed. Comparative Examples 6 and 7 NR# ¹ alone or NR# ¹ / carbon (ISAF) = 90/10 (wt%) was stretched at a roll temperature of 160°C, cooled at 80°C, and then processed in Table 1. The compound was used as a polymer, and compounding processing and vulcanization molding were performed according to the compounding recipe shown in Table 1. Table 3 shows the physical property measurement results. Comparative Example 8 A mixture of 90 parts by weight of IR-2200/BRO1=70/30 (wt%) and 10 parts by weight of carbon (ISAF) was stretched at a roll temperature of 160°C, then cooled to 80°C. Using this as the polymer shown in Table 1, compounding processing and vulcanization molding were carried out according to the formulation shown in Table 1.
Table 3 shows the physical property measurement results. Example 10 20 parts by weight of toluene was added to 1 part by weight of poly(4-methyl-1-pentene) (manufactured by ICI, melting point 235°C) and dissolved by heating. After cooling, the swollen polymer was stirred for 15 minutes using a high-speed mixer (13,000 rpm) and crushed by applying shear force. While mixing a predetermined amount of this mixture with a propeller stirrer, add a solution of IR-2200 in n-hexane (solid concentration 10% by weight) so that the content of poly(4-methyl-1-pentene) is 10% by weight. Add the specified amount of
Stirring was continued for 30 minutes. The mixture was poured into a large excess of methanol containing a small amount of 2,6-di-t-butyl-p-cresol and coagulated. The average particle size of poly(4-methyl-1-pentene) in this rubber composition was 0.32μ. After stretching the coagulated material at a roll temperature of 200℃,
After cooling to 80°C, kneading and vulcanization molding were performed using the formulation shown in Table 1. Table 4 shows the physical property measurement results. Examples 11, 12 Poly(4-methyl-1-pentene) of Example 10
Table 4 shows the results of an experiment in which the content was changed to 7.5 and 15% by weight. Example 13 2,2′-methylenebis(4-methyl-6-t) was added to 100 parts by weight of a mixture of 10% by weight of poly(4-methyl-1-pentene) powder with an average particle size of 30μ and 90% by weight of IR-2200. -butylphenol) was added and kneaded at 230°C using an extruder (25 mmφ). This kneaded product was stretched at a roll temperature of 200°C, and then blended and vulcanized according to the formulation shown in Table 2. Table 4 shows the physical property measurement results. Example 14 IR-2200 of Example 13 was converted into NR# ¹ (natural rubber,
Table 4 shows the results of experiments performed by changing to RSSNo1). Comparative Example 9 Table 4 shows the results of an experiment in which the roll temperature of Example 10 was changed to 80°C. Comparative Example 10 2,2'-methylenebis(4-
1 part by weight of methyl-6-t-butylphenol) was added and kneaded at a roll temperature of 200°C. This kneaded product was stretched at a roll temperature of 200°C, and then blended and vulcanized according to the formulation shown in Table 2. Table 4 shows the physical property measurement results. Example 15 100 parts by weight of a mixture of 10 parts by weight of polypropylene powder with an average particle size of 210μ and 90 parts by weight of IR-2200, and 2,2'-methylenebis(4-methyl-6-t-butylphenol) (anti-aging agent) 1 part by weight was added and kneaded at 200°C using an extruder (25 mmφ). This kneaded product was stretched at a roll temperature of 160°C, and then blended and vulcanized according to the formulation shown in Table 2. Table 3 shows the physical property measurement results. Example 16 After heating and dissolving 90 g of IR-2200 and 10 g of polypropylene pellets (average particle size 3 mm) in 2 kg of toluene, the hot polymer solution was dissolved in a small amount of 2,6-di-t-butyl-p. -The polymer was recovered by pouring it into a large amount of methanol containing cresol. The resulting polymer was dried in vacuum for 24 hours. The particle size of polypropylene in the obtained rubber composition was 0.48μ. This rubber composition was stretched using rolls at 150°C, and then compounded and vulcanized according to the formulation shown in Table 2. Table 3 shows the physical property measurement results. Example 17 A swollen polymer swollen with 20 parts by weight of toluene per 1 part by weight of poly(4-methyl-1-pentene) was stirred at high speed (10,000 rpm) in an aqueous potassium rosinate solution, and then steam was introduced to remove the solvent. was removed. In this case, 3 g of potassium rosinate was used per 1 g of poly(4-methyl-1-pentene). The powder thus obtained was collected and dried. The average particle size was 20μ. This fine powder was added to an n-hexane solvent (the dispersion concentration at this time was 1.5% by weight), and while stirring and dispersing with a high-speed mixer (10000 rpm), a hexane solution of polyisoprene rubber (IR-2200) (solid content concentration
10%) was added to the above suspension and mixed with stirring. The mixture was added to a large amount of methanol containing a small amount of 2,6-di-t-butyl-p-cresol and coagulated.
Poly(4-methyl-1-pentene) content is 10%
It was hot. The coagulated rubber composition was vacuum dried for one day and then stretched using a roll at 200°C. Table 2
It was mixed and vulcanized according to the recipe. Table 4 shows the physical property measurement results. Example 18 1 part by weight of 2,2'-methylene-bis(4-methyl-6-t-butylphenol) was added to 100 parts by weight of the rubber composition of Example 6, and the mixture was heated in an extruder equipped with a T-die (25 parts by weight).
Kneading and stretching were performed at 170°C using a lip gap of 0.1 mm. They were blended and vulcanized according to the recipe in Table 2. Table 3 shows the physical property measurement results.

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Claims (1)

[Scope of Claims] 1. A mixture of polyisoprene rubber or a rubber containing polyisoprene rubber as a main component in which high melting point isotactic poly-α-olefin with a melting point of 150°C or higher is dispersed to have an average particle size of 50 μm or less. 65℃ above the melting point of isotactic poly-α-olefin
A method for producing a rubber composition having a high elastic modulus, which comprises stretching at a temperature ranging from a low temperature to a temperature 20°C higher than the melting point. 2. The method for producing a rubber composition according to claim 1, wherein the content of the high melting point isotactic poly-α-olefin in the rubber composition is 2 to 40% by weight.