JPS6254133B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber composition that provides a vulcanizate that has excellent flow processability and excellent rubber elasticity and mechanical properties as indicated by Ryupke's impact resilience. Currently, natural rubber (NR) is used as tire rubber.
Styrene-butadiene copolymer rubber (SBR) or polybutadiene rubber (BR) is mainly used. These solid rubbers are usually blended with fillers such as carbon black, which provide a high reinforcing effect, and are used as rubber compounds for tires, but these compounds have poor flow processability and require uniform performance. However, there were many difficulties involved in the industrial production of tires and the like. Conventionally, processing aids such as process oil and adhesives have been added to the rubber composition to improve fluidity and processability, resulting in a uniform rubber composition, which is then used to manufacture tires. However, as the use of radial tires progresses, there is a strong trend towards lightweight tires and fuel-efficient tires, and as a result, vulcanized materials are required to have physical properties that require high Ryupke impact resilience, hardness, and mechanical properties. In today's world, it has not been possible to obtain satisfactory results using the processing aids mentioned above. Attempts have been made to use liquid rubbers such as liquid polybutadiene and liquid polyisoprene to improve these problems, but these efforts have not always been satisfactory. In particular, it was not possible to obtain sufficient Ryupke repellency. In order to improve these drawbacks of the conventional technology, the inventors of the present invention have conducted intensive studies and found that the viscosity average molecular weight is
A low molecular weight butadiene polymer having a vinyl bond content of 13,000 to 100,000 and 30% or less, preferably a viscosity average molecular weight of 20,000 to 75,000 and a molecular weight of 3,000 determined by gel permeation chromatography.
Low molecular weight butadiene polymers containing 15% or less of the following polymers (specifically, low molecular weight butadiene polymers or low molecular weight butadiene polymers with a butadiene/isoprene weight composition ratio of 97/3 to 30/70. -Isoprene copolymer) is blended in an amount of 3 to 35 parts by weight per 100 parts by weight of solid rubber mainly composed of natural rubber (NR) or styrene-butadiene copolymer rubber (SBR), resulting in excellent flow processability. The present inventors have discovered that it is possible to obtain an unvulcanized rubber composition that exhibits excellent vulcanized properties and a vulcanized product that exhibits high Ryupke rebound properties, and has completed the present invention. The solid rubber used in the present invention has a Mooney viscosity (ML ₁₊₄ (100°C)) of 35 or more, preferably 40.
Mainly made from the above natural rubber (NR) or styrene-butadiene copolymer rubber (SBR). Natural rubbers include SMR-5L, SMR-20, SMR-50, RSS
#1, RSS #2, RSS #3, ADS, pale crepe, etc. Among them, Mooney viscosity (ML ₁₊₄ (100℃)) is 35 to 130, preferably 40.
~90 is preferably used. As styrene-butadiene copolymer rubber, #1000 and #1100
machines, #1500 machines, #1600 machines, #1700 machines and #1800 machines
hot rubber or cold rubber, among which Mooney viscosity (ML ₁₊₄ (100
C)) is 35 or more, preferably 50 or more. These solid rubbers include polybutadiene rubber (BR), polyisoprene rubber (IR),
An appropriate amount of solid rubber such as 1,3-pentadiene rubber, ethylene-propylene copolymer rubber (EPDM), polychloroprene rubber (CR), and butyl rubber (IIR) may be used. The low molecular weight butadiene polymer used in the present invention is a low molecular weight butadiene polymer or a low molecular weight butadiene-isoprene copolymer having a viscosity average molecular weight of 13,000 to 100,000 and a vinyl bond content of 30% or less. Its viscosity average molecular weight and vinyl bond content are limited to the above ranges.
If the viscosity average molecule is too lower than the above range, the co-vulcanization with solid rubber such as natural rubber or styrene-butadiene copolymer rubber will deteriorate, resulting in poor rubber elasticity, expressed as rebound resilience, for example. Performance such as hardness, modulus, and strength of the vulcanizate deteriorates. On the other hand, if the viscosity average molecular weight is too high, the plasticizing effect will not be exhibited and a uniform rubber compound will not be obtained. From this point of view, the best results are obtained when the viscosity average molecular weight is in the range of 22,000 to 75,000. Here, the viscosity average molecular weight (M _v ) is determined by measuring the intrinsic viscosity in toluene at 30°C, and when the proportion of isoprene units in the low molecular weight butadiene polymer exceeds 50% by weight, the formula [η] = 1.21 × 10 ^{-4 M0} . ⁷⁷ _v , and if the same proportion is less than 50% by weight, the formula [η] = 1.34×10 ^-4 M ⁰ . ⁷⁷ _v . In addition, the vinyl bond content is a value determined by infrared absorption spectroscopy, and it needs to be 30% or less, preferably 17% or less, and if it deviates from this range, the final vulcanized rubber will be affected. The elasticity of the rubber decreases, making it impossible to obtain the intended purpose. In addition to the specified viscosity average molecular weight and vinyl bond, the molecular weight determined by gel permeation chromatography (GPC)
The intended purpose is particularly achieved if the proportion of polymers or copolymers of 3000 or less is at most 15% (by weight). This is especially noticeable when the amount is 10% (by weight) or less. Such low molecular weight butadiene polymers having a specific microstructure and molecular weight can be produced by various methods including anionic polymerization and coordination anionic polymerization (for example, polymerization using Ziegler catalysts). It is preferably produced by an anionic polymerization method using a lithium-based catalyst, which produces a small amount of vinyl bonds, a sharp molecular weight distribution, and a small proportion of low molecular weight parts, and which is extremely easy to polymerize. The anionic polymerization method using such a lithium-based catalyst uses metallic lithium or organolithium (for example, methyllithium, propyllithium, butyllithium, or distyrenyllithium) and a polymerization solvent (n-butane,
isopentane, n-hexane, n-heptane, benzene, toluene, or xylene) in the presence or absence of butadiene monomer or butadiene monomer and isoprene monomer (and other substances within the scope of the present invention). (copolymerizable monomers) are combined and polymerized or copolymerized. Molecular weight can be controlled by adjusting the amount of catalyst and monomer used. The copolymer is produced by adding butadiene monomer and isoprene monomer to the polymerization system separately or simultaneously, or by adding each separately. The butadiene/isoprene weight composition ratio is preferably 30/70 or less. If the composition ratio of butadiene becomes small, the impact resilience becomes small and the intended purpose may not be achieved, so the weight composition ratio is preferably in the range of 97/3 to 40/60. Such specific low molecular weight butadiene polymers and low molecular weight butadiene-isoprene copolymers are blended into solid rubbers mainly composed of natural rubber and styrene-butadiene copolymer rubber, but low molecular weight butadiene polymers are particularly preferred. used. In addition,
The above-mentioned low molecular weight butadiene polymers and low molecular weight butadiene-isoprene copolymers are those whose molecular terminals are carboxyl groups or hydroxyl groups, compounds containing carboxyl groups in the molecular chain (e.g. maleic anhydride, acrylic acid), It may also contain a small amount of a compound containing a hydroxyl group. A solid rubber mainly composed of natural rubber, styrene-butadiene copolymer rubber, and a low molecular weight butadiene polymer are mixed by a conventional method such as a Bamberley mixer or a roll mill, but the mixing ratio is higher than that of the diene solid rubber. The amount of the low molecular weight butadiene polymer is preferably 3 to 35 parts by weight, preferably 5 to 25 parts by weight, per 100 parts by weight. In this way, a rubber composition is obtained, in addition to which vulcanizing agents such as sulfur, peroxides or quinoids, vulcanization accelerators, activators such as stearic acid or zinc oxide, carbon black, silica, clay or carbonic acid are added. Fillers with strong reinforcing properties such as calcium,
Furthermore, rubber compounding chemicals such as wax are added as necessary. Also, if it is a very small amount, oil,
Lanolin, adhesive resin (petroleum-based, rosin-based, terpene-based or phenol-based), etc. may be blended. The rubber composition of the present invention thus obtained can be used in various parts of bias tires and radial tires, especially steel radial tires, such as the tread, carcass, breaker, sidewall, bead filler, steel cord chief, or rim strip. Useful. In addition to tires, it is of course useful for industrial products such as rubber belts, anti-vibration rubber, and rubber hoses. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 and Comparative Example 1 A low molecular weight butadiene polymer (hereinafter abbreviated as LBR(A)) having a viscosity average molecular weight of 57000 and a vinyl bond content of 16% was produced by polymerizing butadiene using butyllithium as a catalyst. A low molecular weight butadiene (hereinafter abbreviated as LBR(B)) having a viscosity average molecular weight of 7000 and a vinyl bond content of 8% was obtained. When the molecular weight distribution of these low molecular weight butadiene polymers was measured by gel permeation chromatography (GPC), it was found that the molecular weight of low molecular weight butadiene polymers LBR (A) and LBR (B) was 3000 or less. The proportions of these cases were 1% and 27%, respectively. These low molecular weight butadiene polymers LBR (A) and LBR (B) were mixed in a Banbury mixer according to the formulation shown in Table 1 to obtain a rubber compound. Their Mooney viscosity was significantly lower than that in the case where the low molecular weight butadiene polymer was not used, and they had excellent flow processability. The rubber compound thus obtained was press vulcanized at 145°C. When the mechanical properties etc. of the obtained vulcanizate were measured, the results shown in Table 1 were obtained.

【table】

[Table] From Table 1, the rubber elasticity seen from the rebound elasticity of the vulcanizate of the rubber compound is when the viscosity average molecular weight is 57,000, the vinyl bond content is 16%, and the proportion of the molecular weight of 3,000 or less is 1%. Certain low molecular weight butadiene polymers
This is sufficient when using LBR(A), which has a viscosity average molecular weight of 7000 and a vinyl bond content of 16%.
It can be seen that this is superior to the case of using a low molecular weight butadiene polymer LBR (B) in which the proportion of molecules having a molecular weight of 3000 or less is 27%. Example 2 and Comparative Examples 2 to 3 By copolymerizing butadiene monomer and isoprene monomer in an inert hydrocarbon solvent using butyllithium as a catalyst, the viscosity average molecular weight was
39000, the amount of vinyl bonds is 13%, the weight composition ratio of butadiene/isoprene is 60/40, and the proportion of molecular weight determined by gel permeation gelatography (GPC) is 5% of 3000 or less. The following low molecular weight butadiene-isoprene copolymer (hereinafter abbreviated as LBIR(C)) was obtained. During the polymerization, butadiene monomer and isoprene monomer were each divided into four portions and added alternately. On the other hand, by copolymerizing butadiene monomer and isoprene monomer in the same manner as the polymerization method described above except for coexisting an ether compound in an inert hydrocarbon solvent, the amount of vinyl bonds was 51%.
A low molecular weight butadiene-isoprene copolymer (hereinafter referred to as LBIR
(abbreviated as (D)) was obtained. Rubber compounds shown in Table 2 were prepared using these two types of low molecular weight butadiene-isoprene copolymers and commercially available alkylphenol resins using a roll mill. These rubber compounds had excellent flow processability.

[Table] As can be seen from Table 2, the viscosity average molecular weight is
Even if it is a low molecular weight butadiene-isoprene copolymer with a vinyl bond content of 13% and a butadiene/isoprene weight composition ratio of 60/40, the molecular weight
When using a low molecular weight butadiene-isoprene copolymer LBIR (C) in which the proportion of molecular weight of 3000 or less is 5% or less, the proportion of molecular weight of 3000 or less is 21
% of low molecular weight butadiene-isoprene copolymer LBIR (D) and phenolic resin, it is superior in terms of flow processability, strength performance and rubber elasticity performance in vulcanizates. . Example 3 and Comparative Examples 4 to 5 By polymerizing butadiene in an inert hydrocarbon solvent using butyllithium as a catalyst,
A low molecular weight butadiene polymer (hereinafter abbreviated as LBR-(E)) with a viscosity average molecular weight of 22,000, a vinyl bond content of 20% or less, and a proportion of molecules with a molecular weight of 3,000 or less (measured by GPC) of 6%. I got it. In this case, the entire amount of butyllithium was added at the start of the polymerization, but when butyllithium was added several times during the polymerization, the viscosity average molecular weight was 24,000 and the amount of vinyl bonds was 21%, proportion of molecules with a molecular weight of 3000 or less (measured by GPC)
is a low molecular weight butadiene polymer (hereinafter referred to as
LBR-(F)) was obtained. Using the two types of low molecular weight butadiene polymers LBR-(E) and LBR-(F) prepared in this way and aromatic process oil as plasticizers, a rubber compound was prepared according to the formulation shown in Table 3. did. These rubber compounds were vulcanized in the same manner as in Example 1, and the physical properties of the obtained vulcanizates were examined, and the results shown in Table 3 were obtained.

【table】

[Table] As can be seen from Table 3, lower molecular weight butadiene polymers with viscosity average molecular weights of 22,000 and 24,000 compared to rubber compounds using process oil as a plasticizer.
Rubber compounds using LBR (E) and LBR (F) are excellent in impact resilience and mechanical properties of the vulcanized products. Low molecular weight butadiene polymer LBR with a particularly low proportion of molecules with a molecular weight of 3000 or less
This is noticeable when (E) is used.

Claims (1)

[Scope of Claims] 1. A low molecular weight butadiene polymer having a viscosity average molecular weight of 13,000 to 100,000 and a vinyl bond content of 30% or less in 100 parts by weight of a solid rubber mainly composed of natural rubber or styrene-butadiene copolymer rubber. A rubber composition containing ~35% by weight. 2. A low molecular weight butadiene polymer in which the viscosity average molecular weight is 20,000 to 75,000, and the proportion of the polymer having a molecular weight of 3,000 or less as determined by gel permeation chromatography is 15% or less. The rubber composition according to claim 1, which is a polymer. 3. The rubber composition according to claim 1 or 2, wherein the low molecular weight butadiene polymer is a butadiene polymer obtained by an anionic polymerization method. 4. Claim 1, wherein the low molecular weight butadiene-based polymer is a butadiene-isoprene copolymer obtained by an anionic polymerization method and having a butadiene/isoprene weight composition ratio of 97/3 to 30/70. Or the rubber composition according to item 2. 5. The rubber composition according to any one of claims 1 to 4, wherein the rubber composition is a compounded rubber for radial tires.