JPH0322413B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition comprising an isoprene polymer having a specified polymer structure and other rubbery polymers, and the present invention relates to a new rubber composition having improved properties suitable for various rubber applications, particularly tire applications. This is what we provide. Natural rubber has extremely excellent processability and physical properties such as green strength, rebound resilience, tensile strength, and tear strength as raw material rubber for various rubber applications, especially tire applications, and its molecular structure is cis-1, It is a well known fact that it is a 4-linked isoprene polymer. On the other hand, various types of synthetic polyisoprene rubber are commercially available, and these have 90 mol% or more of cis-1,4 bonds and exhibit properties similar to natural rubber, but so far they have not reached the properties of natural rubber. I haven't. These synthetic polyisoprene rubbers are synthesized by anionic polymerization using a Ziegler catalyst, which is a combination of a transition metal compound and an organometallic compound, or an organolithium compound, but in general, the higher the 1,4-bonds, the better the natural rubber. They exhibit similar properties and are preferred. Although methods for producing isoprene polymers with lower 1,4-bonds, for example 15 to 80 mol% of 3,4-bonds, are known, they are considered unsuitable for practical use. . As shown in the previous Japanese Patent Application No. 177,696/1987, the present inventors have already discovered that rubber has the above-mentioned low proportion of 1,4-bonds, which was previously considered unsuitable for various rubber applications, especially for tire applications, that is, relatively A rubber composition containing an isoprene polymer having a high proportion of 3,4-bonds was studied, and it was found that the isoprene polymer used under certain restrictions imparts extremely excellent properties to the rubber composition. Rubber, styrene-butadiene copolymer rubber, polyptadiene rubber, 1,
It has been found that this method is effective in improving the wet skid resistance of diene polymers such as isoprene polymers having 80 mol % or more of 4-bonds while maintaining their impact resilience, abrasion resistance, or low heat build-up. The present invention has been made by further intensively proceeding with the studies that led to the above-mentioned invention, whereby the isoprene polymer is
When the molecular structure has a certain specific molecular structure, that is, a multimodal molecular weight distribution that is more than bimodal, a composition having a composition and composition ratio similar to those mentioned above has an effect, such as impact resilience, especially at a high temperature of 50°C or higher. It has been found that the effect of improving the balance between rebound resilience and wet skid resistance is even more remarkable, and that the heat generation property is extremely small and excellent.Based on this knowledge, the present invention has been completed. That is, the present invention has a 3,4-bond of 15 to 80 mol%, a number average molecular weight (n) of 50,000 to 2,000,000, a molecular weight distribution shape that is bimodal or more multimodal, and a weight average molecular weight (w) and number An isoprene polymer having an average molecular weight ratio (w/n) of 1.5 to 5.0 and another rubbery polymer are mixed in a weight ratio.
The present invention provides a rubber composition comprising raw rubber mixed at a ratio of 10:90 to 90:10, and 20 to 120 parts by weight of carbon black and a necessary amount of vulcanizing agent per 100 parts by weight of the raw rubber. , especially when the isoprene polymer is a branched polymer whose high molecular weight portion is coupled with a tin compound, or when the other rubbery polymer is a diene-based rubbery polymer, such as natural rubber or styrene-butadiene copolymer. Rubber, polybutadiene rubber or 1,4
- At least one type selected from synthetic polyisoprene rubbers having a bond content of 80 mol % or more is preferable because the effects described below are great. The rubber composition of the present invention has various superior properties compared to conventionally known rubber compositions, such as improved wet skid resistance and rebound resilience maintained at a high level, especially at high temperatures of 50°C or higher. It exhibits elastic abrasion resistance, etc., and has significantly improved heat generation properties. In the present invention, isoprene polymer refers to, in addition to isoprene polymer, other monomer components copolymerizable with isoprene, such as butadiene, piperylene, styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, This refers to those containing diisopropenylbenzene, etc., and those in which at least 10% by weight, preferably 50% by weight or more of the copolymer consists of isoprene units. The amount of 3,4-bonds in the isoprene polymer used in the present invention is 15 to 80 mol%, preferably 20 to 70 mol%. If it is less than 15% by mole, the effect of improving wet skid resistance, which is the object of the invention, will not be achieved, while if it is more than 80% by mole, certain physical properties, such as abrasion resistance, will be extremely poor, which is not preferred. Other important molecular structures of the isoprene polymer used in the present invention are molecular weight and molecular weight distribution. The molecular weight is measured by a conventional method using GPC (gel persion chromatography) and determined from a calibration curve using a polystyrene standard sample of known molecular weight. The molecular weight of the polymer of the present invention is limited to 50,000 to 2,000,000 in terms of polystyrene equivalent number average molecular weight. Polymers outside this range do not have sufficient mixability with other rubbery polymers or processability in compounding, and low molecular weight polymers are not preferred in the present invention from the viewpoint of physical properties that need to be improved. The preferred molecular weight range is 100,000 to 1,000,000, particularly preferably 200,000 to 800,000. The isoprene polymer of the present invention, like other isoprene polymers, is subject to the effect of "decomposition", and the above-mentioned molecular weight indicates the molecular weight before this operation. In addition, the shape of the molecular weight distribution of the isoprene polymer used in the present invention is a bimodal or more multimodal molecular weight distribution, and the molecular weight distribution has a weight average molecular weight to number average molecular weight ratio (n/n) of 1.5 to 5.0. It needs to be something. A bimodal or more multimodal molecular weight distribution can also be obtained by mixing two or more types of polymers with different molecular weights, but a particularly preferable shape of the polymer used in the present invention is that the shape of the polymer after polymerization is A polymer whose high molecular weight side is a branched polymer obtained by coupling a part of the active end with a polyfunctional coupling agent such as silicon tetrachloride, tin tetrachloride, carbon tetrachloride or 700 form. The modal is molecular weight distribution. The most preferred coupling agent is a tin compound, examples of which include tin tetrachloride, tin tetramethoxy, and trichlorobutyltin. In addition, the weight average molecular weight (w) and number average molecular weight (
The ratio (w/n) of n) is limited to 1.5-5.0. If it is less than 1.5, the processability of the rubber composition will be insufficient, while if it exceeds 5.0, the effect on physical properties will be insufficient, which is not preferable. The shape and w/n of the above molecular weight distribution are the same as the molecular weight.
This is determined by measurement using GPC. The isoprene polymer used in the present invention can be obtained by anionic polymerization in an inert diluent, and IA metal is generally used as the anionic catalyst. A particularly preferred catalyst for obtaining the polymer used in the present invention is a catalyst comprising an organolithium compound or an organosodium compound and a Lewis base. Examples of the above organic lithium compounds include the following. Methylithium, ethyllithium, n-(sec- or tert-)butyllithium, amyllithium, phenyllithium or cyclohexyllithium. Examples of Lewis bases include ether compounds, thioether compounds, tertiary amine compounds, phosphine compounds, alcoholate compounds of alkali metals other than lithium, sulfonates, and sulfuric acid ester salts. Use more than one species. Particularly preferred compounds include dimethyl ether, diethyl ether, diphenyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, 1,2-dipoxyethane, triethylamine, N,N,N',N'-tetramethylethylenediamine, dialkylallylsulfur Examples include hydrofluoride, hexamethylphosphoamide, potassium alkylbenzenesulfonate, sodium alkylbenzenesulfonate, potassium butoxide, sodium butoxide, and the like. The second component constituting the raw material rubber of the rubber composition of the present invention
Another preferable rubbery polymer as a component is a diene rubbery polymer. Particularly preferred diene-based rubbery polymers include natural rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, and synthetic polyisoprene rubber having 80% or more of 1,4-bonds. Can be used. The above-mentioned diene-based rubbery polymer has its molecular structure, such as molecular weight, molecular weight distribution, degree of branching, and in the case of copolymers, the composition ratio of monomer components, its distribution, or the bonding mode of each monomer component (microstructure). Although there are various types depending on the distribution and the like, in general, any molecular structure may be used as long as it is a rubbery polymer. The composition ratio of the isoprene polymer and other rubbery polymers in the raw material rubber is limited to a weight ratio of 10:90 to 90:10, preferably 20:80 to 80:20. Within this range, the present invention exhibits the effects described above.
Increasing the isoprene polymer ratio beyond this range is undesirable as it brings about a significant decrease in impact resilience, abrasion resistance, etc. On the other hand, if the ratio of other rubbery polymers increases significantly, the effect of improving the rubber composition by the isoprene polymer, which is the object of the present invention, will not be sufficiently exhibited, which is undesirable. The above-mentioned components constituting the raw rubber of the present invention may be mixed together with other components constituting the rubber composition using an open roll, an internal mixer, etc., or only the raw rubber components may be mixed in advance with these rubber mixers. or mixed in solution,
A method of removing the solvent may also be used. An example of a preferred method is to mix the raw material rubber in situ during polymerization, in which polymerization is carried out to obtain different polymers in two or more reaction zones connected in series or parallel, thereby producing the raw material rubber of the present invention at once. This is the way to obtain. The rubber composition of the present invention comprises the above-mentioned raw material rubber, carbon black, and a vulcanizing agent. The type and amount of carbon black used can be freely selected depending on the use of the rubber composition of the present invention, and generally FEF
The carbon black is selected from carbon black commonly known as class, HAF class, ISAF class, GPF class or SAF class. Further, the amount thereof needs to be 20 to 120 parts by weight per 100 parts by weight of raw rubber. If it is less than 20 parts by weight, the tensile strength, abrasion resistance, etc. will not be sufficient, and if it exceeds 120 parts by weight, it will result in a significant decrease in rebound properties, which is undesirable. Examples of the vulcanizing agent include sulfur and various sulfur compounds such as quinone dioxime, dithiomorpholine, and alkylphenol disulfide, with sulfur being particularly preferred. The amount used can be freely changed depending on the use of the composition. For example, when using sulfur as a vulcanizing agent, 0.3 parts by weight per 100 parts by weight of raw rubber.
An amount selected within the range of 6.0 to 6.0 parts by weight is used. In use, the rubber composition of the present invention further includes:
If necessary, process oil, fillers other than carbon black, zinc oxide, stearic acid, antioxidants, antiozonants, wax, etc. can be added. Processing oils consist of high-boiling parts of petroleum fractions that are usually used for rubber compounding, and are known as paraffinic, naphthenic, or aromatic oils depending on the chemical structure of their hydrocarbon molecules. can be used depending on the purpose and use, and the amount can be freely selected. Further, as fillers other than carbon black, silicic acid, silicates, calcium carbonate, titanium oxide, various clays, etc. are used. The rubber composition of the present invention is prepared by mixing the above-mentioned components using a mixer known for the rubber industry, such as an open roll.
It is obtained by kneading by various known methods using an internal mixer, etc., and the rubber products obtained through the vulcanization process are compared to rubber products obtained from conventionally known rubber compositions. It exhibits excellent physical properties, such as improved rebound properties, especially the relationship between rebound resilience and wet skid resistance at high temperatures, and has greatly improved heat generation properties, making it suitable for use in, for example, fuel-efficient tires. . Next, the effects of the present invention will be explained with reference to Examples, but these are not intended to limit the present invention. Example 1 n in hexane using a reactor with a capacity of 10
Isoprene was batch polymerized at a temperature of 50°C in the presence of -butyllithium and 1,2-dimethoxyethane. As the polymerization progresses, the temperature rises to 80℃,
99.5 mol% of the isoprene was converted to polymer. Further, tin tetrachloride was added to the obtained polymer having active terminals in a molar ratio of 1/8 to the n-butyllithium used to cause a coupling reaction, thereby obtaining isoprene polymer A. The analysis value of this item is 3,
The 4-bond content was 41 mol%, the number average molecular weight was 410,000, the molecular weight distribution was bimodal, and the w/n ratio was 1.7. Part by weight of this polymer A67 and natural rubber (RSS No. 3)
33 parts by weight is used as raw material rubber, and to this is added 5 parts by weight of aromatic process oil (specific gravity 0.951, VGC 0.961), 50 parts by weight of carbon black (HAF grade), 2 parts by weight of stearic acid, 5 parts by weight of zinc oxide, and antioxidant. Agent B
(Reaction product of diphenylamine and acetone)
1 part by weight, 1.7 parts by weight of sulfur and vulcanization accelerator (n-
tert-butyl-2-benzothiazylsulfenamide) was blended and kneaded using a small laboratory Banbury mixer and an 8-inch roll. The obtained unvulcanized rubber composition was vulcanized at 150°C and subjected to physical property measurements. The results are shown in Table 1. Example 2 A polymer was produced in the same manner as in Example 1 to obtain polymer A, except that tetramethylene diamine was used instead of 1,2-dimethoxyethane and tin tetrachloride was used at a molar ratio of 1/6. I got a B. The analysis value of this product is 3,4-bond 50 mol%, number average molecular weight 470000
The molecular weight distribution was bimodal and w/n 1.8. A rubber composition was obtained in the same manner as in Example 1 except that 67 parts by weight of this polymer B and 33 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Example 3 A rubber composition was obtained in the same manner as in Example 1 except that 33 parts by weight of polymer B and 67 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Example 4 Polymer C was obtained in the same manner as in Example 1, except that a mixture of isoprene and butadiene was used as the monomer instead of isoprene alone. The analytical value for this is 72 bound isoprene
The weight percent was 28% by weight of bound butadiene, 38% by weight of 3,4-bonds in the isoprene moiety, the number average molecular weight was 360,000, and the molecular weight distribution was bimodal with a w/n of 1.8. A rubber composition was obtained in the same manner as in Example 1 except that 67 parts by weight of this polymer C67 and 33 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Example 5 Polymer D was obtained in the same manner as in Example 2, except that a mixture of isoprene, butadiene and styrene was used instead of isoprene alone as the monomer. The analytical values for this product are 57% by weight of bound isoprene, 29% by weight of bound butadiene,
The content was 14% by weight of bound styrene, 46% by mole of 3,4-bonds in the isoprene moiety, a number average molecular weight of 325,000, and a bimodal molecular weight distribution of w/n 1.8. A rubber composition was obtained in the same manner as in Example 1 except that 67 parts by weight of this weight body D and 33 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Example 6 A rubber composition was obtained in the same manner as in Example 1 except that 33 parts by weight of Polymer D and 67 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Comparative Examples 1 to 3 Comparative Examples 1 to 3 each used a polymer as the raw material rubber.
100 parts by weight of A, 100 parts by weight of polymer B and natural rubber
A rubber composition was obtained in the same manner as in Example 1 except that 100 parts by weight was used alone. Table 1 shows the physical properties after vulcanization. Comparative Example 4 Polymer E was obtained in the same manner as in Example 1 except that 1,2-dimethoxyethane was not used. The analytical value of this product is 9 mol% of 3,4-bonds, number average molecular weight of 410,000, and molecular weight distribution is bimodal w/
n was 1.8. A rubber composition was obtained in the same manner as in Example 1 except that 67 parts by weight of this polymer E and 33 parts by weight of natural rubber were used as raw rubber. Table 1 shows the physical properties after vulcanization. Comparative Example 5 Isoprene polymer F was obtained using the same reactor and polymerization conditions as in Example 1, except that batch polymerization was changed to continuous polymerization and the coupling reaction was not performed. The analysis value of this product is 3,4-bond 44 mol%, number average molecular weight 390000, molecular weight distribution is monomodal w/
It was n2.0. Part by weight of this polymer F67 and natural rubber
A rubber composition was obtained in the same manner as in Example 1 except that 33 parts by weight was used as the raw rubber. Table 1 shows the physical properties after vulcanization. By comparing the physical properties of Examples 1 to 6 and Comparative Examples 1 to 5 in Table 1, it was possible to limit the polymers A to D, which exhibit extremely poor physical properties when used alone as raw rubber. The compositions of the examples used by mixing with natural rubber at the same ratio do not lose the advantages of compositions made of natural rubber alone, such as high rebound elasticity and small and good heat generation properties, but without losing the disadvantages of compositions made of natural rubber alone. It was found that the wet skid resistance was significantly improved. Furthermore, by comparing the physical properties of Examples 1, 2, 4, and 5 and Comparative Examples 4 and 5, it was found that this improvement was achieved only by isoprene polymers having a specific polymer structure. I understand. The recovery of vulcanization of these compositions was also measured using a disk rheometer at 160°C. As a result, the compositions of Examples 1 to 6 showed almost no recovery, whereas the composition of Comparative Example 3 exhibited significantly large recovery, as is generally known. It turned out to be extremely good.

【table】

[Table] Examples 7 to 9 In Examples 7 to 9, styrene-butadiene copolymer rubber (manufactured by Japan Synthetic Rubber Co., Ltd., emulsion polymerization
SBR#1502), polybutadiene rubber (manufactured by Asahi Kasei Kogyo Co., Ltd., Diene 35) in Example 8, and cis-1,4-polyisoprene rubber in Example 9, except that aromatic Process oil (specific gravity 0.951, VGC 0.961) 15 parts by weight, carbon black (HAF-HS grade) 60 parts by weight, stearic acid 3 parts by weight, zinc oxide 5 parts by weight, antioxidant B
(Reaction product of diphenylamine and acetone)
1 part by weight, 1.8 parts by weight of sulfur and vulcanization accelerator (n-
1.2 parts by weight of tert-butyl-2-benzothiazylsulfenamide) was blended and kneaded using a small laboratory Banbury mixer and an 8-inch roll. The obtained unvulcanized rubber composition was vulcanized at 160°C and subjected to physical property measurements. The results are shown in Table 2. Comparative Examples 6 to 8 In Comparative Examples 6 to 8, each of the styrene-butadiene copolymer rubber, polybutadiene rubber, and cis-1,4-polyisoprene rubber used in Examples 7 to 9,
Rubber compositions were prepared in exactly the same manner as in Examples 7 to 9, except that the rubber composition alone was used as the raw material rubber. Table 2 shows the physical properties after vulcanization. By comparing Example 7 and Comparative Example 6, Example 8 and Comparative Example 7, and Example 9 and Comparative Example 8 in Table 2, it was found that styrene-butadiene copolymerization was carried out similarly to the case of natural rubber shown in Table 1. rubber, polybutadiene rubber,
In the case of cis-1,4-polyisoprene rubber, by mixing Polymer A in a certain limited ratio, the disadvantages can be improved without losing the advantages of each, and the balance can be improved. It can be seen that a composition exhibiting excellent physical properties was obtained.

【table】

【table】

Claims (1)

[Claims] 1. 15 to 80 mol% of 3,4-bonds, a number average molecular weight (n) of 50,000 to 2,000,000, a shape of molecular weight distribution that is bimodal or more multimodal, and a weight average molecular weight (w) of Number average molecular weight ratio (w/
An isoprene polymer having Mn) of 1.5 to 5.0 and another rubbery polymer in a weight ratio of 10:90 to 90:10.
A rubber composition prepared by blending 20 to 120 parts by weight of carbon black and a necessary amount of a vulcanizing agent per 100 parts by weight of raw rubber mixed in the ratio of . 2. The rubber composition according to claim 1, which is a branched polymer obtained by coupling a tin compound on the high molecular weight side of an isoprene polymer. 3. The rubber composition according to claim 1, wherein the other rubbery polymer is a diene rubbery polymer. 4. The diene-based rubbery polymer is at least one selected from natural rubber, styrene-butadiene copolymer rubber, polyptadiene rubber, and synthetic polyisoprene rubber containing 80 mol% or more of 1,4-bonds. A rubber composition according to claim 3.