JPH07103264B2 - Rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to an isoprene-based rubber composition which is particularly excellent in fracture properties and cyclic fatigue resistance and has a large hysteresis loss.

In recent years, in order to improve the braking performance and grip performance of tires in transportation means such as automobiles and motorcycles, and to prevent noise and vibration of industrial machinery, rubber materials having excellent vibration damping or damping properties have been required. ing. Since these anti-vibration or anti-vibration materials are used under extremely severe conditions, it is required that the materials have a large hysteresis loss and are excellent in fracture characteristics, especially in repeated fatigue resistance.

b. Conventional technology Conventionally, natural rubber or synthetic rubber mixed with a large amount of oil or carbon black has been used as these materials. However, when a large amount of oil is mixed, the impact resilience decreases. , Vibration damping and vibration damping performance are improved, but compression set,
The tensile properties are significantly reduced. Further, when a large amount of carbon black is mixed, there is a problem that the repeated fatigue resistance is deteriorated. As a result of studies conducted by the present inventors in order to solve such a problem, by using a lithium-based isoprene copolymer, good cyclic fatigue resistance, which was not possible with conventional polymers, and a material with high hysteresis loss were obtained. Was found to be obtained (JP-A-57-87406).
No. 58, No. 58-79035, No. 58-122945, No. 59-206423.
No. 59-64645).

However, although such polymers certainly have good vibration damping properties such as repeated fatigue properties and hysteresis loss properties, they have poor fracture properties such as tensile strength and wear resistance, and satisfy recent high requirements for properties. Was still insufficient.

On the other hand, JP-A-57-94028 discloses that wet skid characteristics and fuel consumption characteristics are improved by using a high vinyl type isoprene rubber (IR) having a certain amount of 3,4 bonds or more. . Further, JP-A-58-210943 discloses that an isoprene copolymer having a relatively high vinyl bond content is branched with a coupling agent so that a part of the polymer is branched to broaden the molecular weight distribution so as to have high impact resilience and resistance. It is disclosed that a material having an excellent balance of wear resistance, low heat buildup and wet skid characteristics can be obtained.

c. Problems to be Solved by the Invention However, the fracture strengths of the materials disclosed in the above two publications are still unsatisfactory.

As described above, the high vinyl type IR has various excellent physical properties, but in view of its poor fracture strength, the present invention has been accomplished as a result of investigations on improving physical properties.

d. Means for Solving the Problem That is, the rubber composition of the present invention is (I) an isoprene polymer obtained by polymerizing using a lithium-based catalyst, wherein i) 1,2 bonds and 3, Polyisoprene block (A) with a total of 4 bonds is 20% or less, and the total of 1,2 bonds and 3,4 bonds is 60%
It is composed of the above polyisoprene block (B), and ii) the weight ratio of the block (A) to the block (B) is 10 to 40.
/ 90 to 60, iii) the total of 1,2 bonds and 3,4 bonds in the polymer is 40% or more, iv) contains 20% or more of components having 3 or more branches, and v ) 20 to 70 parts by weight of a block type isoprene polymer having a Mooney viscosity (ML _{1 + 4} , ₁₀₀ ° C) of 30 to 150, and (II) isoprene rubber, styrene-butadiene rubber,
Polybutadiene rubber At least one rubber selected from ethylene-propylene-diene terpolymer rubber (EPDM) and isobutene-isoprene rubber (IIR) 80 parts by weight to 3
It is composed of 0 parts by weight.

The isoprene polymer (I) is obtained by anionic polymerization using a lithium catalyst (organic lithium compound) as an initiator in an inert solvent.

As the polymerization initiator, in addition to a lithium-based catalyst such as alkyllithium, a Lewis base such as ether or tertiary amine can be used as a cocatalyst. As the alkyllithium, monolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium and amyllithium and dilithium compounds such as tetramethylenedilithium are preferably used. Examples of Lewis bases include monoethers and polyethers such as tetrahydrofuran, 2-methoxytetrahydrofuran, o-dimethoxybenzene, ethylene glycol dibutyl ether, and diethylene glycol dimethyl ether, and N, N, N ',
Tertiary amines such as N'-tetramethylethylenediamine, dipiperidinoethane are used. The amount of Lewis base depends on the microstructure of the block copolymer desired.

As the solvent, a solvent inert to the lithium-based catalyst is used, and for example, 2-methyl-butene-1,2-methyl-butene-2, isopentane, n-hexane, cyclohexane, heptane, benzene, toluene and the like are preferably used. To be

The polymerization temperature is usually preferably in the range of 0 ° C to 150 ° C, and the temperature is controlled to be constant, or the polymerization is carried out at an elevated temperature without heat removal. Further, in order to increase productivity, the monomer concentration can be increased and controlled by self-flash.

The block-type isoprene polymer (I) of the present invention is
It contains 20% or more of a branched polymer having 3 or more branches.

The branched polymer can be obtained by polymerizing a monomer using a lithium-based catalyst as an initiator to form blocks (A) and (B), and then performing a coupling reaction using a coupling agent. Coupling agents include alkenyl aromatic compounds such as divinylbenzene and diisopropenylbenzene, tin halides such as tin tetrachloride and triphenyltin chloride, halogenated compounds such as silicon tetrachloride, butyltrichlorosilicon and methyltrichlorosilicon. Silicon compounds, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, polymeric type diphenylmethane diisocyanate, isophorone diisocyanate, isocyanate compounds such as hexamethylene diisocyanate, There are polyester compounds such as diethyl adipate, polyepoxy compounds such as epoxidized soybean oil, 4-vinylpyridine, 2-vinylpyridine, etc. It can be added to the system. Further, a monofunctional modifier such as tributyltin chloride, N, N'diethylaminobenzophenone or 1,3 diethyl-2-imidazolidinone may be used in combination with the above coupling agent.

The isoprene polymer (I) is obtained by batch polymerization or continuous polymerization using a tank reactor, a tower reactor, or a tubular reactor.

The weight ratio of the block (A) to the block (B) in the block-type isoprene polymer (I) is 10-40 / 90-60. If the amount of the block (A) is less than 10% by weight, the tensile strength and wear resistance will be poor, and if it exceeds 40% by weight, the antivibration performance such as flex crack growth resistance and hysteresis loss property will be poor.

Regarding the microstructure, polyisoprene block (A)
Has a total of 1,2 and 3,4 bonds of less than 20%. If it exceeds 20%, the tensile strength and wear resistance are poor. The polyisoprene block (B) has a total of 1,2 bonds and 3,4 bonds of 60% or more. If it is less than 60%, the hysteresis loss is small and the anti-vibration performance is poor.

The average microstructure of the block-type isoprene polymer (I) of the present invention is such that the total of 1,2 bonds and 3,4 bonds is 40%.
Or more, preferably 50% or more. If it is less than 40%, excellent vibration damping performance cannot be obtained.

The molecular weight of the block-type isoprene polymer of the present invention has a Mooney viscosity (ML _{1 + 4} , ₁₀₀ ° C.) of 30 to 150.
If the Mooney viscosity is less than 30, the fracture characteristics and wear resistance are poor,
Further, if it exceeds 150, it is very difficult to industrially obtain it, and even if it is obtained, the workability is poor and the desired physical properties cannot be obtained.

The block-type isoprene polymer (I) of the present invention is
By introducing a branched structure, it is possible to improve fracture characteristics and cyclic fatigue resistance. That is, the content of the branched polymer of the isoprene polymer (I) is 20% or more, preferably 30 to 70%. The content of the block polymer having this branched bond can be measured by gel permeation chromatography (GPC).

Excellent flex crack growth resistance, abrasion resistance, fracture properties, and hysteresis loss properties are shown in isoprene polymer (I) and other specific diene rubbers, namely isoprene rubber, styrene butadiene rubber, polybutadiene rubber, EPDM, IIR.
It is obtained by blending with at least one rubber (II) selected from the above.

The isoprene rubber also includes natural rubber.

The isoprene polymer (I) is used in a proportion of 20 to 70 parts by weight based on 100 parts by weight of the total rubber after blending. If it is less than 20 parts by weight, excellent flex crack growth resistance and hysteresis loss properties cannot be obtained, and if it exceeds 80 parts by weight, wear resistance and tensile strength are poor.

Known additives can be added to the rubber composition of the present invention depending on its use. For example, carbon black or silica-based white filler is added in an amount of 10 to 120 per 100 parts of rubber.
Parts, extender oils such as aromatic oil and naphthenic oil are blended with 0 to 80 parts per 100 parts of rubber, and vulcanizates are used for high loss materials, specifically various vibration damping materials, soundproofing materials and tire materials (tread , Sidewalls).

e. Examples Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to this example as long as the gist thereof is not exceeded. The fracture property depends on the tensile strength (T _B ), the hysteresis loss is the impact resilience, and the cyclic fatigue resistance property is the crack growth property under constant elongation (the time for the crack to grow to a certain length is indicated by an index). It was evaluated by.

Examples 1 to 7 and Comparative Examples 1 to 9 Polymer A 2000 g of cyclohexane and 500 g of isoprene were charged into a 5 autoclave that had been sufficiently dried and purged with nitrogen, and then the temperature was raised to 50 ° C. 0.23 g of n-butyllithium was added as a polymerization initiator, and the block (A) was polymerized at an isothermal temperature. After the polymerization conversion rate reached 20%, 100 g of tetrahydrofuran was added, and the block (B) was further polymerized at a polymerization temperature of 45 ° C to 60 ° C. After the polymerization conversion rate reached 100%, 0.08 g of silicon tetrachloride was added to carry out a coupling reaction. The obtained polymer was added with 3 g of 2,6-di-tert-butyl p-cresol as an antioxidant.
Was added, and the mixture was desolvated by the steam stripping method, and then dried on a hot roll. The analysis results of the obtained polymer are shown in Table 1.

Polymer B The block (A) was polymerized isothermally in the same manner as the polymer A using 2000 g of cyclohexane and 500 g of isoprene and 0.24 g of n-butyllithium. Polymerization conversion
After reaching 30%, 100 g of tetrahydrofuran was added and the block (B) was further polymerized at a temperature in the range of 45 to 60 ° C. Polymer A after the polymerization conversion rate reaches 100%
The same coupling reaction was performed. The analysis results of the obtained polymer are shown in Table 1.

Polymer C A polymer was obtained in the same manner as in Polymer A except that 0.5 g of polymeric diphenylmethane diisocyanate was used as the coupling agent. The analysis results are shown in Table-1.
It was shown to.

A polymer was obtained in the same manner as the polymer A except that the polymer D block (B) was polymerized at a temperature of 40 ° C to 50 ° C.

Polymer E A polymer was obtained in the same manner as the polymer A except that 3 g of tetrahydrofuran was added to polymerize the block (A).

Polymer F A polymer was obtained in the same manner as the polymer A except that 40 g of tetrahydrofuran was added to polymerize the block (B).

Polymer G A polymer was obtained in the same manner as the polymer A except that 100 g of tetrahydrofuran was added and the polymerization was carried out when the polymerization conversion rate was 8%.

Polymer H A polymer was obtained in the same manner as the polymer A except that 100 g of tetrahydrofuran was added when the polymerization conversion rate was 50%.

Polymer I A polymer was obtained in the same manner as the polymer A except that 0.02 g of silicon tetrachloride was added.

Polymer J n-butyllithium and silicon tetrachloride 0.03 each
A polymer was obtained in the same manner as the polymer A except that 5 g and 0.012 g were added.

Polymer K A polymer was obtained in the same manner as the polymer A except that 0.12 g of SnCl ₄ was used as the coupling agent.

The analysis results of Polymers A to K are shown in Table 1.

Each of the above polymers A to K was kneaded in a 250 cc plastomill in accordance with the compounding recipe shown in Table-2.
Vulcanization was performed at ° C.

Table-2 Parts by weight Polymer 100 HAF Carbon 50 Stearic acid 2 ZnO 3 Anti-aging agent 810NA ^{* 1} 1 Anti-aging agent TP ^{* 2} 0.8 Accelerator DPG ^{* 3} 0.6 Accelerator DM ^{* 4} 1.2 Sulfur 1.5 * 1 N-phenyl-N ′ -Isopropyl-p-phenylenediamine * 2 N, N'-diallyl-p-phenylenediamine * 3 Diphenylguanidine * 4 Dibenzothiazyl disulfide The obtained polymer was used as natural rubber (NR) or styrene-butadiene rubber (SBR). Table 3 shows the evaluation results of the physical properties of the rubber obtained by blending at the compounding ratio shown in Table 3.

As is clear from the results shown in Table 3, Example-1,
2,4,5,6 and 7 of rubber T _B as compared to the rubber of Comparative Example 1,2,3 and 5 to 9, E _B, hysteresis loss properties (resilience), flex crack growth resistance and It has a good overall balance of wear properties and is suitable as a vibration damping material.

Similarly, the rubber of Example-3 has a better balance of physical properties than the rubber of Comparative Example-4, and is suitable as a vibration damping material.

f. Effects of the Invention The rubber composition of the present invention is excellent in fracture properties, flex crack growth resistance and hysteresis loss properties, and by utilizing these properties, it can be used as a material for various vibration damping applications.

Claims (2)

[Claims] 1. An isoprene polymer obtained by polymerization using a lithium-based catalyst, comprising: i) a polyisoprene block (A) having a total of 1,2 bonds and 3,4 bonds of 20% or less. It is composed of polyisoprene block (B) having a total of 1,2 bonds and 3,4 bonds of 60% or more, and ii) the weight ratio of block (A) to block (B) is 10 to 40.
/ 90 to 60, iii) the total of 1,2 bonds and 3,4 bonds in the polymer is 40% or more, iv) contains 20% or more of components having 3 or more branches, and v ) 20 to 70 parts by weight of a block-type isoprene polymer having a Mooney viscosity (ML _{1 + 4} , ₁₀₀ ° C.) of 30 to 150, 2. A rubber comprising 80 to 30 parts by weight of at least one rubber selected from isoprene rubber, styrene-butadiene rubber, polybutadiene rubber, ethylene-propylene-diene terpolymer rubber and isobutene-isoprene rubber. Composition.