JPH0345097B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition containing three components as raw rubber components: natural rubber or polyisoprene rubber, polybutadiene rubber with a specific structure, and styrene-butadiene copolymer rubber with a specific structure. The present invention provides a rubber composition with improved vulcanization recovery in the vulcanization process, good processability, and excellent properties such as abrasion resistance and tensile strength of the vulcanizate. BACKGROUND OF THE INVENTION Raw material rubber used in vulcanized rubber products such as automobile tires, anti-vibration rubber, and footwear can be roughly divided into two types: natural rubber and synthetic rubber.
Of these, natural rubber has better processability, green strength, adhesion, tensile strength, heat generation properties, etc. than various synthetic rubbers, and as a result of advances in science and technology, many synthetic rubbers have been developed. Even today, it is still used in many areas of rubber products. However, the disadvantages of natural rubber are physical, such as poor abrasion resistance of the vulcanizate and the tendency to cause unevenness in the vulcanized state during vulcanization. Compared to synthetic rubber, the production volume and price of natural rubber are more easily affected by weather factors, making it more susceptible to supply instability. Polyisoprene rubber, which was developed to replace natural rubber, is similar to natural rubber in terms of its molecular structure, but it is not as good as natural rubber in terms of green properties, adhesiveness, etc. In addition, although various other synthetic rubbers have various physical properties, most of them are not as good as natural rubber in terms of the balance of various physical properties. In addition, many attempts have been made to blend synthetic rubber with natural rubber in order to improve the above-mentioned drawbacks of natural rubber. For example, blending polybutadiene rubber with natural rubber has improved wear resistance. . However, little effort has been made to improve vulcanization recovery while retaining the above-mentioned characteristics of natural rubber. Under such circumstances, the inventors of the present invention have conducted intensive studies to improve a rubber composition in which natural rubber or polyisoprene rubber is blended with polybutadiene rubber and styrene-butadiene copolymer rubber, and as a result, they have arrived at the present invention. (A-1) Component: 20-75% by weight of natural rubber and/or polyisoprene (B-1) Component: 10-50% by weight of polybutadiene with a vinyl bond content of 1-25% (C-1 ) component: styrene content is 5 to 60% by weight, and vinyl bond content in the butadiene part is 60 to 80%
Styrene-butadiene copolymer 15-60
The present invention is a conjugated diene rubber composition using, as a raw material rubber, the following three components: The present invention will be described in detail below. Component (A-1) of the present invention comprises natural rubber and/or
or polyisoprene rubber, preferably at least 30% by weight of the component (A-1) is natural rubber. The natural rubber used in the present invention has a polyisoprene skeleton, and is a raw material rubber obtained by concentrating and refining the sap of the Hevea tree and other plants. Furthermore, the polyisoprene rubber used in the present invention is
It is a rubber-like synthetic rubber obtained by polymerizing isoprene in an inert hydrocarbon solvent using a Ziegler catalyst or a lithium catalyst, and generally contains 85% or more of cis-1,4 bonds. , those with a number average molecular weight of about 100,000 to 1,000,000 are used. In the present invention, component (A-1) is used in a composition of 20 to 75% by weight, preferably 30 to 70% by weight of the raw rubber. If the amount is less than 20% by weight, the tensile strength, heat generation property, etc. of the resulting composition will be problematic, while if it exceeds 75% by weight, vulcanization is likely to occur. Next, the polybutadiene used as component (B-1) of the present invention is rubbery and has a vinyl bond content of 1 to 25%, preferably 1 to 15%.
When the amount exceeds 25%, problems arise in the abrasion resistance, anti-friction elasticity, etc. of the vulcanizate obtained. The polybutadiene component (B-1) preferably has a number average molecular weight in the range of 50,000 to 400,000, more preferably 75,000 to 300,000, and has a molecular weight distribution (weight average molecular weight (Mw) and number average molecular weight (Mn)). (Mw/Mn)) is preferably 1.1
~4.0. Component (B-1) is used in an amount of 10 to 50% by weight, preferably 15 to 50% by weight, based on the raw rubber. If the amount is less than 10% by weight, the effect of improving the abrasion resistance of the resulting composition will be slight, while if it exceeds 50% by weight, processability will be insufficient and re-vulcanization will likely occur. Next, the styrene content of the styrene-butadiene copolymer used as component (C-1) of the present invention is 5 to 60% by weight, preferably 15 to 50% by weight. If the styrene content is less than 5% by weight, the processability is insufficient and the resulting composition has poor tensile strength.
Wet skid resistance is poor; conversely, if the stainless steel content exceeds 60% by weight, there is no problem with wet skid resistance, but it has a negative effect on abrasion resistance and anti-friction elasticity. The amount of vinyl bonds in the butadiene moiety of the styrene-butadiene copolymer (C-1) is 35 to 80%, preferably 40 to 70%.
If the vinyl bond content is less than 35%, the effect of improving vulcanization recovery will be small and the wet skid resistance of the resulting composition will be insufficient; on the other hand, if it exceeds 80%,
Poor abrasion resistance and anti-shock elasticity. The styrene-butadiene copolymer of component (C-1) is a copolymer in which the styrene units in the polymer are uniformly present along the molecular chain, and the styrene content increases or decreases along the molecular chain. one or more polymer blocks consisting of a copolymer with a high styrene content, a copolymer with a high styrene content or polystyrene, and one or more polymer blocks consisting of a copolymer with a low styrene content or polybutadiene. Any polymer may be used. Also,
Amount of blocked styrene in copolymer (J.Polym.Sci,
1, 409 (1946)) is preferably 5% by weight or less of the copolymer from the viewpoint of exothermic properties. In addition, copolymers in which the vinyl bonds of the component (C-1) are uniform along the molecular chain like the above-mentioned styrene, copolymers in which the amount of vinyl bonds increases or decreases, copolymers with different amounts of vinyl bonds, etc. A variety of copolymers can be used, including copolymers in which there are two or more polymer blocks. The number average molecular weight of the component (C-1) and the styrene-butadiene copolymer is preferably 50,000 to 400,000,
More preferably, the range is 75,000 to 300,000, and the molecular weight distribution is preferably 1.1 to 4.0. (C-1) component is 15 to 60% by weight in the raw rubber,
It is preferably used in a range of 20 to 50% by weight. When the amount is less than 15% by weight, the effect of improving vulcanization recovery is slight and the wet skid resistance of the composition is poor, and when it exceeds 60% by weight, the abrasion resistance is deteriorated. Furthermore, in the present invention, the styrene content of the mixed component (B-1) and (C-1) is 10 to 35% by weight, and the amount of vinyl bonds in the butadiene portion is 30 to 60%. It is preferable to use each component according to its structure and composition in order to balance the effect of improving vulcanization reversion, retention of abrasion resistance, and other properties of the resulting composition. The polybutadiene of the component (B-1), (C-
1) Any of the styrene-butadiene copolymers obtained by any manufacturing method may be used as the raw rubber component of the present invention as long as they meet the limiting conditions for each polymer. can. Typical methods for producing polybutadiene, component (B-1), include a method using an organolithium-based catalyst as a catalyst, or a method using a Ziegler-based catalyst such as a nickel compound, titanium compound, or cobalt compound. Examples include a solution polymerization method and an emulsion polymerization method. The styrene-butadiene copolymer of component (C-1) is a copolymer with a higher vinyl bond content than the styrene-butadiene copolymer generally used for rubber applications. The copolymer used is typically manufactured by using an organic lithium such as n-butyllithium or sec-butyllithium or other alkali metal compound as a polymerization catalyst in an inert solvent such as hexane, cyclohexane, or benzene. , alkoxides such as potassium butoxide, dodecylbenzenesulfonate, as co-catalyst components as necessary.
Polar organic compounds such as ethers, polyethers, tertiary amines, polyamines, thioethers, hexamethylphosphorotriamide, etc. are used as compounds to adjust the amount of vinyl bond using organic compounds typified by organic acid salts such as sodium stearate. It can be obtained by copolymerizing the monomers styrene and butadiene in a predetermined ratio. The amount of vinyl bonds can be controlled by the amount of the polar organic compound added and the polymerization temperature. It is also possible to couple the polymer chain having an active end obtained by the above method with a polyfunctional compound such as silicon tetrachloride, tin tetrachloride, or a polyepoxy compound, or to add a branching agent such as divinylbenzene. Depending on the method of addition to the polymerization system, branched or radial copolymers can be obtained. Furthermore, in the polymerization method, various polymerization conditions such as adjusting the addition method of the monomer, changing the amount of the compound for adjusting the vinyl bond amount, the addition method, and the polymerization temperature in the middle of the polymerization reaction, It is possible to make a copolymer in which the styrene content and the amount of vinyl bonds increase or decrease in the molecular chain, or the copolymer has a block shape.
Acetylene, 1,2-butadiene, fluorene,
Various compounds such as primary amines and secondary amines can also be used. The polymerization process for obtaining the above polymers can be a batch process, a continuous process, or a combination thereof. Next, the characteristics of the composition of the present invention will be described. (1) Compared to compositions using natural rubber and/or polyisoprene as raw material rubber, vulcanization recovery is improved, and the resulting vulcanizate has a good relationship between abrasion resistance and wet skid resistance. be. (2) Compared to a composition using the two components of the present invention, component (A-1) and polybutadiene as component (B-1), as raw rubber, vulcanization recovery is improved, and the resulting vulcanization The tensile strength and wet skid resistance of the material are improved. (3) It has better abrasion resistance than a composition whose raw rubbers are the component (A-1) of the present invention and the styrene-butadiene copolymer as the component (C-1). . (4) In the (A-1) component of the present invention, (B-
The composition has better wet skid resistance than when the raw rubber is a mixture of two components: 1) component + styrene-butadiene copolymer having a styrene content and vinyl bond amount corresponding to component (C-1). Abrasion resistance is improved while maintaining the The composition of the present invention includes the component (A-1), (B-
Component 1) and component (C-1) are used as raw rubber,
Various compounding agents are added to this, and it is put into practical use by being molded and vulcanized. The compounding agents added to the above rubber composition include:
Reinforcing agents, softeners, fillers, vulcanizing agents, vulcanization accelerators, vulcanization aids, colorants, flame retardants, lubricants, foaming agents,
There are other compounding agents, and these are selected and used as appropriate depending on the intended use of the composition. Carbon black is a typical reinforcing agent, and it can be obtained by various manufacturing methods. Various carbon blacks with different particle sizes or structures are used, but ISAF, HAF, and FEF carbon blacks are preferably used for applications centered on tires. The amount of process oil added is taken into account depending on the amount of raw rubber used, but the raw rubber 100
10 to 150 parts by weight, preferably 40 to 150 parts by weight
100 parts by weight are used. The type and amount of carbon black added are appropriately adjusted depending on the intended use of the rubber composition, and two or more types may be used in combination. Other reinforcing agents used include inorganic reinforcing agents such as silica and activated calcium carbonate, high styrene resins, and phenol-formaldehyde resins. 1 to 100 parts by weight are used, preferably 5 to 50 parts by weight. Typical softeners added as needed include process oils, and various rubbers such as paraffin, naphthenic, and aromatic rubbers are suitably used in the composition, and when added to 100 parts by weight of the raw material rubber, Against 2
~100 parts by weight are used, preferably 5 to 70 parts by weight. It is also possible to use an oil-extended polymer in which process oil is added to the raw rubber in advance. Other softening agents include liquid paraffin, coal tar, fatty oil, and sub. A typical example of the vulcanizing agent is sulfur, which is used in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of raw rubber. Other vulcanizing agents include sulfur compounds such as sulfur chloride, morpholine disulfide, and alkylphenol disulfide, and peroxides, which may be used alone or in combination with sulfur. There are a wide variety of vulcanization accelerators,
These vulcanization accelerators are used in an amount of 0.01 to 5 parts by weight per 100 parts by weight of raw rubber, and two or more types may be used in combination. Typical vulcanization accelerators include guanidine, aldehyde-amine, and aldehyde-ammonia. , thiazole series, imidazoline series, thiourea series, thiuram series, diothycarbamate series,
Examples include xanthate type and mixing accelerators. As a vulcanization aid, metal oxides such as zinc oxide,
There are fatty acid compounds such as stearic acid, amines, etc., and these are 0.1% per 100 parts by weight of raw rubber.
~10 parts by weight are used. Typical anti-aging agents or antioxidants added as needed are amine-based, phenol-based, phosphorus-based, sulfur-based, etc., and these are 0.001 to 10 parts by weight per 100 parts by weight of raw rubber. They may be added, and two or more types may be used in combination. In addition, scorch inhibitors added as needed include phthalic anhydride, salicylic acid, N-nitroso-diphenylamine, etc. Tackifiers include coumaron-indene resin, terpene-phenol resin, rosin ester, etc. Examples include calcium carbonate, clay, talc, and aluminum hydroxide. Furthermore, various other compounding agents may be used as necessary. The rubber composition of the present invention is produced by mixing raw rubber and various compounding agents using various mixing devices generally used for mixing rubber compositions, such as open rolls, Banbury mixers, kneaders, and extruders. Then, after being molded into the desired shape, it is vulcanized. The rubber composition of the present invention can be used for various automobile tires,
Due to its characteristics, it is suitable for use in industrial products such as belts, hoses, anti-vibration rubber, footwear, daily necessities, construction materials, and various other uses. Examples are shown below, but these are intended to explain the present invention more specifically, and are not intended to limit the scope of the present invention. Reference Example Among the polybutadiene and styrene-butadiene copolymer used as component (B-1) and component (C-1) in the present invention, examples of typical polymerization methods for polymers other than commercially available products are shown below. . Polymerization of Γ Sample B-b Using a polymerization reactor with an internal volume of 40 mm equipped with a stirrer and a jacket, n-hexane was added to the reactor.
18.2 kg, butadiene 4.6 kg, diethylene glycol dimethyl ether 5.0 g, and n-butyl lithium 2.0 g were added, and the reactor internal temperature was maintained at 50 to 75°C, polymerization was continued for 1.5 hours. After adding 0.5 parts by weight of di-tert-butyl-p-cresol, the solvent was removed to obtain sample B-b. The analytical values of this sample are shown in Table 2.
Shown below. Note that the microstructure was calculated by measuring the spectrum using an infrared spectrophotometer and using Morero's method. In addition, when sample B-b was analyzed by GPC, the weight average molecular weight (Mw) was 254,000, the number average molecular weight (Mn) was 178,000, and Mw/Mn = 1.43.
It was hot. In addition, GPC is Shimadzu LC-1
The detector is a differential refractometer, the solvent is tetrahydrofuran, and the column is HSG-50.
One tube each of 60 and 70 was measured at a temperature of 40°C. The analytical values of other (B-1) components are shown in Table 2. Polymerization of Γ Sample Ca [used as component (C-1)] Using the same polymerization reactor as that used to obtain Sample B-b, 18.2 kg of cyclohexane, 3.45 kg of butadiene, 1.15 kg of styrene, and diethylene glycol were added to the reactor. Add 6.0 g of dimethyl ether and 3.0 g of n-butyl lithium, and adjust the internal temperature of the reactor to 50-70℃.
After polymerization was completed, 3.0 g of silicon tetrachloride was added to the polymer solution to cause a coupling reaction. After adding 0.5 parts by weight of di-tert-butyl-P-cresol per 100 parts by weight of the polymer, the solvent was removed and Sample C-
I got a. The analytical values of sample Ca are shown in Table 3. Also, Mw=276000, Mn=158000, Mw/
Mn=1.75. Polymerization of Γ sample C-f Using one polymerization reactor with an internal volume of 10 equipped with a stirrer and a jacket, the internal temperature of the polymerization reactor was set at 94 to 98°C.
26g/min of butadiene and 6.5g/min of styrene as monomers were supplied from the bottom of the reactor.
min, n-hexane as solvent 130g/min,
2.4 Tetrahydrofuran as a polar compound
The polymerization reaction was started by feeding 0.038 g of n-butyllithium as a catalyst per 100 g of monomer using a metering pump, and the polymer solution was continuously extracted from the top of the reactor. After reaching a steady state, 0.5 parts by weight of di-tert-butyl-P-cresol per 100 parts by weight of the polymer was added to the obtained polymer solution, and the hexane solvent was removed. The analytical values of the obtained polymer (sample Cf) are shown in Table 3. In addition, in the analysis by GPC, sample C-f has Mw=338000, Mn=
148000, Mw/Mn=2.28. Table 3 also shows the analytical values of the styrene-butadiene copolymer used in the other component (C-1). The styrene content and the microstructure of the butadiene moiety in the styrene-butadiene copolymer were determined by measuring the spectrum using an infrared spectrophotometer.
Calculated by Hampton's method. [Table] [Table] [Table] [Table] Example 1 Natural rubber and polyisoprene rubber shown in Table 1 were used as component (A-1), polybutadiene rubber shown in Table 2 was used as component (B-1), The raw material rubber of the present invention was used as the styrene-butadiene copolymer rubber (C-1) component shown in Table 3, and the compounding agents shown in Table 4 were used at the composition ratio of each component as shown in Table 5. Mixed using a Banbury mixer. After molding, the obtained compound was press-vulcanized at 140℃,
Physical properties were measured. The results are shown in Table 5. The results shown in Table 5 will be described below. Examples 1-1 to 1-3 are sample A-a and sample B.
-a, a composition whose raw material rubber is a rubber obtained by mixing the three components of sample C-a within the composition range of the present invention. Restoration of vulcanization is improved compared to the composition of Comparative Example 1-2 in which only the composition, sample B-a, is a rubber component. Further, in all of these Examples, the relationship between abrasion resistance and wet skid resistance is improved compared to Comparative Examples 1-1 to 1-3. Furthermore, sample C-a of Comparative Example 1-3
Compared to compositions using In Comparative Example 1-4, the amount of component (A-1) was higher than the range of the present invention, and this composition showed little improvement in reversion, and in Comparative Example 1-5, the amount of component (A-1) was higher than the range of the present invention. It is lower than the range, and the tensile strength and heat generation properties are inferior. Comparative Example 1-6, which consists of two components, component (A-1) and component (B-1), had greater reversion than the composition of the example, and the tensile strength and wet skid resistance of the vulcanizate were lower. On the other hand, Comparative Example 1-7 consisting of two components, component (A-1) and component (C-1),
Poor rebound elasticity and abrasion resistance. Furthermore, Comparative Example 1-8 is the same as that of Example 1-2 (B
-1) component + A styrene-butadiene copolymer having a styrene content and a vinyl bond amount corresponding to component (C-1) and sample A-a were used as raw rubber, but Example 1- Compared to No. 2, wear resistance is inferior. Comparative Example 1 using a styrene-butadiene copolymer outside the scope of the present invention as component (C-1)
Comparative Example 1-9, which used polybutadiene outside the scope of the present invention as component (B-1), had poor abrasion resistance. Example 1-4 is a composition using polyisoprene rubber as the component (A-1), and results equivalent to natural rubber were obtained. Table 4 Raw material rubber 100 parts by weight Aromatic process oil 5 ISAF grade carbon black 45 Stearic acid 2 Zinc oxide 4 Anti-aging agent B ^*1 1 Vulcanization accelerator CZ ^*2 1 Sulfur 1.7 *1 Diphenylamine and acetone reaction product*2 N-cyclohexylbenzothiazole sulfenamide Example 2 Various samples were used as the (B-1) component and (C-1) component, and the three components with the composition shown in Table 7 were used as raw rubber, A composition containing the ingredients shown in Table 4 was obtained in the same manner as in Example 1 and vulcanized to give the results shown in Table 7. As shown in Table 7, it can be seen that the composition of the present invention has improved cure recovery and has well-balanced physical properties of the vulcanizate. [Table] [Table] [Table] [Table]

Claims (1)

[Scope of Claims] 1 (A-1) Component: 20 to 75% by weight of natural rubber and/or polyisoprene (B-1) Component: 10 to 50% by weight of polybutadiene with a vinyl bond content of 1 to 25% ( C-1) Component: Styrene content is 5 to 60% by weight, and vinyl bond content in the butadiene part is 60 to 80%.
Styrene-butadiene copolymer 15-60
A conjugated diene rubber composition whose raw material rubber is three components of % by weight. 2. Claims that the styrene content of the polymer composition obtained by mixing component (B-1) and component (C-1) is 10 to 35% by weight, and the amount of vinyl bonds in the butadiene portion is 30 to 60%. The conjugated diene rubber composition according to item 1. 3 (A-1) Component: Natural rubber and/or polyisoprene 20-75% by weight (B-1) Component: Polybutadiene with a vinyl bond content of 1-25% 10-50% by weight (C-1) Component: The styrene content is 5-60% by weight, and the vinyl bond amount in the butadiene part is 60-80%.
Styrene-butadiene copolymer 15-60
A rubber composition for vulcanization comprising three components by weight as a raw rubber, and the raw material rubber further contains a component (D): a reinforcing agent and a component (E): a vulcanizing agent.