JPS6121253B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to high hardness, high modulus rubber compositions. More specifically, tire parts or industrial rubber products exhibit excellent processability when unvulcanized, have low temperature dependence of hardness and modulus after vulcanization, and have excellent low heat generation properties, especially blowout resistance. The present invention relates to a high hardness, high modulus rubber composition suitable for. With the remarkable development of the automobile industry in recent years and the expansion of the expressway network, the performance required of automobile tires has become even more stringent. for example,
In terms of maneuverability, high-speed stability, handling stability, and running resistance characteristics are required, and in terms of durability, characteristics such as fracture resistance, fatigue resistance, and heat generation characteristics are required. Such required performance has been satisfied to some extent with existing general-purpose rubbers. However, it is not necessarily sufficient as a rubber material for various types of flat tires such as radial tires, which are new tires that accompany the recent increase in the speed of automobiles. These tires have a more complex structure than normal bias tires, and because they are flat and have a larger ground contact area, the components that use the tire's high-hardness rubber are required to perform more rigorously than conventional tires. Ru. Specific performance requirements for high hardness rubber parts include high hardness and high modulus with low temperature dependence of hardness and modulus, low heat build-up, good fatigue resistance, and good adhesion. . It goes without saying that good workability is also an important performance requirement. Conventionally, attempts have been made to obtain high hardness rubber by incorporating a large amount of reinforcing filler such as carbon black, or by blending high styrene rubber or resins. However, when a large amount of filler is blended, processing performance in various processes such as kneading in a Banbury mixer, roll processing, extrusion processing, and vulcanization molding is significantly inferior. Furthermore, the performance of vulcanized rubber is also disadvantageous due to the inclusion of a large amount of reinforcing fillers such as carbon black. That is, the heat generation temperature during the dynamic test is high, and the fatigue resistance, for example, the time required for fracture under repeated compressive deformation (blowout time) is short. Furthermore, when a blend of high styrene rubber and resins is used, the hardness and modulus are highly temperature dependent and the rubbery properties are inferior. For this reason, it can be used as a high-hardness rubber material such as the sole material of shoes, but it is difficult to use as a high-hardness rubber for tires, which have severe usage conditions. As mentioned above, the reality is that there is no material among existing high-hardness rubbers that meets the strict performance requirements associated with recent developments in tire design technology. Therefore, the present inventors conducted intensive studies to develop a high hardness, high modulus rubber that has good processability, low temperature dependence of hardness and modulus after vulcanization, low heat generation, and excellent blowout resistance. As a result of progress,
A rubber composition containing 3 to 10 parts by weight of sulfur in 100 parts by weight of a mixture of 1,2-polybutadiene (hereinafter abbreviated as 1,2PB) and a general-purpose rubber such as natural rubber has the above properties. It has been discovered that a rubber with excellent high hardness and high modulus can be obtained, and the present invention has been achieved. That is, the present invention has a vinyl content of 70%.
10 to 50 parts by weight of 1,2 polybutadiene with a crystallinity of 5 to 40%, an intrinsic viscosity [η] (measured in toluene at 30°C) of 0.7 or more, and natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber. The product contains 3 to 10 parts by weight of sulfur in 90 to 50 parts by weight of at least one rubber selected from polybutadiene rubber and polybutadiene rubber.It has good processability, temperature dependence of hardness and modulus, heat generation property, and especially blowout resistance. This is a high hardness, high modulus rubber composition characterized by: In the 1,2PB used in the present invention, 70% or more, preferably 80% or more of the butadiene bonds are 1,2 bonds. Further, the crystallinity of 1,2PB is 5 to 40%, preferably 10% to 30%. The intrinsic viscosity in toluene at 30°C is preferably 0.7 or more, more preferably 1.0 to 3.0.
If the degree of crystallinity is less than 5%, the thermoplastic properties will be weak, the processability of the unvulcanized rubber will be poor, and the desired high hardness rubber will not be obtained. If the degree of crystallinity exceeds 40%, it will be difficult to knead and mold it using ordinary rubber processing machines. Rubbers to be blended with 1,2PB include natural rubber (NR), cis-polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), and cis-polybutadiene rubber (BR), and other rubbers, such as ethylene- High hardness rubber exhibiting good fatigue properties (for example, blowout resistance) cannot be obtained using α-olefin rubber or the like. These rubbers contain 90 to 50 parts by weight of 1,2PB10 to 50 parts by weight.
Parts by weight are used. If the weight fraction of 1,2PB is less than 10 parts by weight, the thermoplastic properties of the unvulcanized product will be weak, making it impossible to obtain a product with good processability, and it will also be difficult to obtain the desired high hardness rubber. . When the weight fraction of 1,2PB exceeds 50 parts by weight, a large amount of sulfur is required to reduce temperature dependence, making it difficult to obtain a rubber composition with excellent rubber-like elasticity. Furthermore, the tackiness of the surface of the unvulcanized rubber becomes poor, which is unfavorable in terms of the manufacturing process. The amount of sulfur required to obtain the effects of the present invention varies depending on the degree of crystallinity and weight fraction of the 1,2PB used, but is at least 3 parts by weight per 100 parts by weight of rubber containing 1,2PB. 10 parts by weight or less, preferably 4 to 4 parts by weight
7 parts by weight. If the weight ratio of sulfur is less than 3 parts by weight, the crosslinking density cannot be sufficiently increased, so the temperature dependence of the vulcanized rubber is large, and it is impossible to obtain a high hardness rubber exhibiting excellent blowout resistance. In general rubber materials, blowout resistance deteriorates when the crosslink density is increased, but the rubber composition of the present invention, contrary to general rubber materials, has extremely good blowout resistance by increasing the crosslink density. It has a major feature in that it shows . The weight percentage of sulfur is
If the amount exceeds 10 parts by weight, it is difficult to obtain a high hardness rubber with excellent rubber-like elasticity. The rubber composition of the present invention usually contains carbon black in an amount of 20 to 70 parts by weight, preferably 40 to 60 parts by weight, per 100 parts by weight of rubber containing 1,2PB. In the present invention, since 1,2PB, which has high hardness after vulcanization, is used, it is possible to sufficiently obtain the desired high hardness rubber with a smaller amount of carbon black than usual. Adding more than 70 parts by weight of carbon black will adversely affect properties such as processability and heat generation properties, similar to existing high-hardness rubbers. Furthermore, if the amount of carbon black added is less than 20 parts by weight, a sufficient reinforcing effect cannot be obtained, and various mechanical strengths are deteriorated, which is not preferable in terms of practical performance. There are no particular restrictions on the type of carbon black, and ordinary carbon black can be used. The process oil used in the present invention includes:
Naphthenic process oils and aromatic process oils are preferred. Also, the blending amount is 1,
It is used in an amount of 5 to 100 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of rubber containing 2PB. If the amount of process oil is less than 5 parts by weight, the filler and vulcanization accelerator will be poorly dispersed, and if it is more than 100 parts by weight, the strength and elasticity of the resulting vulcanized rubber will be poor. In the present invention, in addition to sulfur, carbon black, and process oil, compounded rubber chemicals such as various reinforcing agents, fillers, softeners, and anti-aging agents can be appropriately added depending on the purpose to impart their effects. . The method of vulcanization in the present invention is not particularly limited, and after kneading the above-mentioned components well using a mixer such as a roll or Banbury, vulcanization is performed using a conventional method such as a vulcanizing press, a vulcanizing pot, or an injection molding machine. be able to. The rubber compound composition of the present invention obtained as described above exhibits excellent processability when unvulcanized, and after vulcanization, it has high hardness and high modulus, has low temperature dependence of these physical properties, and has low heat build-up. It is characterized by being a rubber composition with extremely excellent blowout resistance. Another major feature is that because of its good fluidity, it has excellent vulcanization adhesion to other rubbers or dissimilar materials, such as fibers and bead wires. As mentioned above, the rubber composition obtained by the present invention has many characteristics not found in existing high-hardness rubbers, so it can be applied to various parts of the tire shown in FIG. , TP wedge 2, TP
Filler 3, TP insert 4, SW filler 5,
Rim cushion 6, bead filler #1, #2
7. It can be applied to bead insulation 8, etc. Among these, it is particularly suitable for application to parts of the rim cushion 6, bead filler 7, and bead insulation 8 that require high hardness.
Note that 9 in the figure is a side wall. In addition to tire applications, the characteristics of this rubber composition can also be used in rubber product fields such as vibration-proof rubber for various automobiles, vibration-proof rubber for building floors, and railway track pads. It goes without saying that there is. Hereinafter, the present invention will be specifically explained using Examples, but the present invention is not limited by these Examples unless the gist of the invention is exceeded. In addition,
Parts and % in the following examples mean parts by weight and % by weight unless otherwise specified. Example 1 1,2PB with 92% 1,2 bonds, crystallinity 25%, and intrinsic viscosity 1.3 (30°C, toluene)
(1,2PB-A. This is the product name JSR
RB820), natural rubber (RSS#3), polyisoprene rubber (JSR IR2200), and styrene-butadiene copolymer rubber (JSR1500) with sulfur,
Carbon black and rubber compounding agents were used in the proportions shown in Table 1, and after kneading with a Banbury mixer, press vulcanization was performed at 150°C for 30 minutes. Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber composition. The physical property measurement conditions are summarized in Table 2.

【table】

【table】

【table】

[Table] Comparative Example 1 Example 1 (Experiment No. 1) except that 1.5 parts by weight of sulfur was used.
A vulcanized rubber was obtained in the same manner as in 2). Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber composition. Comparative Example 2 Example 1 (Experiment No. 1) except that 12 parts by weight of sulfur was used.
A vulcanized rubber was obtained in the same manner as in 2). Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber composition. Comparative Example 3 A vulcanized rubber was obtained in the same manner as in Example 1, except that 100 parts by weight of 1.2PB-A was used. Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber composition. Comparative Example 4 A vulcanized rubber was obtained in the same manner as in Example 1, except that 100 parts by weight of RSS #3, 2.5 parts by weight of sulfur, 80 parts by weight of carbon black, and 15 parts by weight of aroma oil were used. Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber composition. Comparative Example 5 A vulcanized rubber was obtained in the same manner as in Example 1, except that 70 parts by weight of JSR1500, 30 parts by weight of high styrene rubber (JSR0061), and 1.5 parts by weight of sulfur were used. Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber compound composition. Example 2 1.2PB with 90% 1.2 bonds, crystallinity 17.8%, and intrinsic viscosity 1.25 (30°C, in toluene)
Table 4 shows the compounding agents for rubber using the following compounds: A vulcanized rubber was obtained using the compounding ratio shown in (same as Example-1). Table 3 shows the physical properties of the unvulcanized and vulcanized products of this rubber compound composition.

【table】

【table】

[Table] Example 3 Assuming the application of high hardness rubber to the rim cushion part of a tire, the following experiment was conducted taking into account actual usage conditions and usage conditions. That is, the two types of unvulcanized rubber of Example 1 (Experiment Nos. (2) and (4)) and the unvulcanized rubber with the tire sidewall composition shown in Table 5 were molded into a round bar shape using an extruder. Vulcanization and adhesion were carried out as shown in FIG. 2 under the same vulcanization conditions as in Example-1. In the figure, 10 is sidewall rubber, 11 is Example-1
rubber. Thereafter, the blowout time was measured using a Gutdoritsu flexometer to evaluate the fatigue resistance. The results are shown in Table-6.

【table】

[Table] Comparative Example 6 The unvulcanized rubber of Comparative Example 4 was vulcanized and bonded in the same manner as in Example 3, and the blowout time was measured using a Gutdoritsu flexometer to determine the resistance. The fatigue properties were evaluated. The results are shown in Table-6.

[Table] Example 4 Assuming the application to the bead insulation part of a high hardness part of a tire, the following experiment was conducted in consideration of actual usage conditions and usage conditions. That is, using the same unvulcanized rubber and beat wire as in Example 1 (Experiment No. 2) except that 50 parts by weight of carbon black was used, the width α was set to 50 parts as shown in Fig. 3.
A test piece with a thickness β of 10 mm was vulcanized and formed, and a beat wire pull-out test and a pull-out fatigue test were conducted. In the figure, 12 is vulcanized rubber and 13 is a beat wire. The results are shown in Table-7. In addition,
The vulcanization conditions were the same as in Example-1. Comparative Example 7 Using the existing bead insulation rubber shown in Table 8, it was vulcanized and molded in the same manner as in Example 4, and a beat wire pull-out test and a pull-out fatigue test were conducted. The results are shown in Table-7.

【table】

[Table] Note 1) Diphenyl guanidine

[Table] From the above results, the rubber compound composition of the present invention shows good processability when unvulcanized, and after vulcanization, it has high hardness and high modulus, has low temperature dependence of these physical properties, and has low heat generation. It can be seen that it has excellent fatigue resistance (blowout resistance) and good adhesion.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing each component of the tire, FIG. 2 is a schematic diagram of a specimen in Example-3, and FIG.
The figure shows the shape of the specimen in Example-4. 1...Trend, 2...TP wedge, 3...
TP filler, 4...TP insert, 5...SW
Filler, 6... Rim compression, 7... Bead filler #1, #2, 8... Bead injection, 9... Side wall.

Claims (1)

[Claims] 1. Vinyl content is 70% or more and crystallinity is 5 to 40.
%, intrinsic viscosity [η] (measured in toluene at 30℃)
10 to 50 parts by weight of 1,2 polybutadiene of 0.7 or more, 90 to 50 parts by weight of at least one rubber selected from natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, and polybutadiene rubber, and 3 to 10 parts by weight of sulfur. A high hardness, high modulus rubber composition comprising: 2 The vinyl content of the 1,2 polybutadiene is
80% or more, crystallinity 10-30%, intrinsic viscosity [η]
2. The rubber composition according to claim 1, wherein the rubber composition (measured in toluene at 30°C) is from 1.0 to 3.0. 3. The rubber composition according to claim 1, wherein the amount of sulfur is 4 to 7 parts by weight. 4. The rubber composition according to claim 1, wherein 20 to 70 parts by weight of carbon black is blended with 100 parts by weight of the rubber containing the 1,2 polybutadiene.