JPH036247A - Rubber composition for tire - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention provides a rubber composition, particularly a rubber composition containing high trans polybutadiene rubber and olefin rubber as main components, which has excellent weather resistance, heat resistance, and crack growth resistance. This invention relates to an excellent rubber composition.

Furthermore, this invention provides a tire using the rubber composition,
In particular, the present invention relates to a pneumatic tire that not only dramatically improves the appearance but also significantly improves the retread life of large tires by using it in the tread and/or sidewall.

(Prior Art) In the field of pneumatic tires, natural rubber, polybutadiene (BR), and styrene-butadiene rubber (SBR) have traditionally been used as rubber compositions for tire sidewalls.
) was often composed of a blend of In recent years, there has been a trend to frequently use BR, which has excellent bending fatigue resistance, and the blend ratio of BR is often 50% or more.

However, rubber compositions made only of the above diene rubber are inherently easily degraded by oxygen and ozone, and are usually formulated with strong amine anti-aging agents and paraffin wax to prevent aging. There is.

While the tire is new, there are no particular problems in terms of weather resistance, but at the end of its life, or when the tread is renovated and used for a long period of time, the effective amount of anti-aging agent in the rubber composition decreases. As a result, ozone cracks, etc. occur. In addition to the above-mentioned durability issues, there has recently been a strong demand for improving the appearance of tires themselves. That is, as mentioned above, the rubber composition for tire sidewalls contains a large amount of amine anti-aging agent and paraffin wax, which blooms on the rubber surface and forms a protective layer, resulting in excellent anti-aging effects. However, when this protective layer is exposed to sunlight, the amine-based anti-aging agent turns brown, resulting in a very poor appearance.

In order to solve the above problems, methods of using anti-aging agents with a long life, and methods of using reactive anti-aging agents that react with the main chain of the rubber and do not release the anti-aging agent to the outside are considered. However, these have a small anti-aging effect and
The results are not necessarily satisfactory.

On the other hand, research is also being conducted to use non-diene rubbers that do not have double bonds in their main chains so that anti-aging agents are not necessary. These include ethylene propylene diene copolymer (EPDM) and halogenated butyl rubber, but these rubbers have significantly lower crack growth resistance and fracture strength than diene rubbers, so they have excellent weather resistance and ozone resistance. Although it can be obtained, there are very few cases where it has been put into practical use.

(Problems to be Solved by the Invention) An object of the present invention is to provide a rubber composition that has excellent weather resistance and ozone resistance over a long period of time, and has improved crack growth resistance and fracture strength.

A second object of the present invention is to provide a durable pneumatic tire that has excellent weather resistance, ozone resistance, and good appearance over a long period of time, and does not deteriorate in crack growth resistance and breaking strength.

(Means for Solving the Problems) In order to obtain a rubber composition blended with olefin rubber and having excellent weather resistance and ozone resistance, the present inventors solved the problem of crack growth resistance, which is a drawback of olefin rubber. We have discovered that high trans polybutadiene rubber is extremely effective as a means of improving breaking strength, and have completed this invention.

That is, the present invention first uses 20 to 80 parts by weight of high trans polybutadiene rubber containing 75 to 90% by weight of 1.4-1-lance bonding units, and a tertiary compound of ethylene, propylene, and diene. An inorganic filler is added to 100 parts by weight of rubber consisting of 20 to 50 parts by weight of at least one olefin rubber selected from the group consisting of polymers and halogenated butyl rubbers and 0 to 60 parts by weight of other diene rubbers. This is a vulcanizable tire rubber composition containing 20 to 150 parts by weight.

A second aspect of the present invention is a pneumatic tire comprising a tread portion, a sidewall portion, and a bead portion, in which the tread portion, the sidewall portion, or both are made of the rubber composition for a tire.

(Function) The rubber composition of the present invention, on the other hand, contains two olefin rubbers.
The weather resistance and ozone resistance are improved by using 1 part of 0 to 50fi, and on the other hand, 20 to 80% by weight of high trans polybutadiene rubber containing 1.4-trans bond units in the range of 75 to 90% by weight is used. The most important feature is that crack growth resistance, abrasion resistance, and fracture strength are ensured by using the

If the olefin rubber is less than 20 parts by weight, the weather resistance and ozone resistance will be poor, and if it exceeds 50 parts by weight, the weather resistance and ozone resistance will be sufficient, but the crack growth resistance and fracture strength will be significantly reduced. .

Furthermore, the effect of improving crack growth resistance and fracture strength is small when the high trans polybutadiene rubber is used for less than 20 overlapping parts.

Other diene-based rubbers include natural rubber, isoprene-based rubbers such as synthetic polyisoprene rubber, and butadiene-based rubbers such as cis-polybutadiene and styrene-butadiene rubber, but isoprene-based rubbers, especially natural rubber, are destructive. Preferred from the viewpoint of physical properties, workability, etc. The amount of other diene rubber used is 0 to 60 parts by weight, if necessary.

In this invention, the terpolymers of ethylene, propylene, and diene include terpolymers with various ethylene and propylene contents and various diene monomers.
A terpolymer having an ethylene content of 8 to 85 mol %, a weight average molecular weight of 250,000 or more, and an iodine value of 10 or more is preferred because it has particularly excellent crack growth resistance and fracture properties. When the amount of ethylene is less than 68 mol%, the effect of improving physical properties due to ethylene chains is small, and when it exceeds 85 mol%, the rubbery property is lost. Furthermore, if the weight average molecular weight is less than 250,000, the strength of the polymer will be greatly reduced. Furthermore, if the iodine value is less than 10, co-vulcanization with other diene rubbers will be poor.

If the trans linkage unit of the high trans polybutadiene rubber used in this invention is less than 75 weight, it does not have sufficient trans chain length to develop elongated crystallinity, and if it exceeds 90 weight, the polymer becomes rubbery. does not indicate. Preferably, the trans-linked units account for 80-85% by weight. Further, from the viewpoint of realizing elongated crystallinity, the vinyl bond is also preferably 15 weight or less.

A high trans polybutadiene rubber having such a microstructure has sufficient elongation crystallinity and can improve fracture strength and flexural fatigue resistance.

Here, as the catalyst system for producing the high trans polybutadiene rubber used in the present invention, the following catalyst systems can be mentioned.

(2) A catalyst comprising an alcoholade of barium, strontium or carlasim, an organoaluminium compound, and an organomagnesium compound described in Japanese Patent Publication No. 62-35401.

■Special Publication No. 62-21002 or Special Publication No. 5
A catalyst comprising barium alcoholade and organolithium as described in Publication No. 6-4501.

■ Japanese Patent Publication No. 60-2323 or Japanese Unexamined Patent Publication No. 56
A catalyst comprising a composite complex of barium, strontium or calcium and organoaluminum described in JP-A-157409, and a Lewis base, lithium alcoholade or lithium phenolate.

(2) A catalyst comprising lithium of organolithium/barium alcoholade or phenolate/organoaluminium/diethylene glycol monoalkyl ether or lithium salt of 2-N-dialkylaminoethanol as described in Japanese Patent Publication No. 57-34893.

■ Japanese Patent Publication No. 52-30543, Japanese Patent Publication No. 56-15
7411, or JP-A-56-157410, a catalyst comprising organolithium/barium alcoholade or phenolate, or a salt of carboxylic acid, aluminum or zinc.

■ Unexamined Japanese Patent Publication No. 11296/1983 or Japanese Patent Publication No. 11296/1983
A catalyst comprising a barium alcoholade or phenolate, an organolithium, an organomagnesium, and an organoaluminium, as described in JP-A No. 26406.

■ Japanese Patent Publication No. 52-48910 or Japanese Patent Application Publication No. 1983-
A catalyst comprising barium alcoholade and organomagnesium described in JP 123628.

■ A catalyst consisting of an organic barium compound, an organic aluminum compound, and an alkali metal salt of ethylene glycol dialkyl ether or ethylene glycol monoallyl ether.

■ Catalysts consisting of organolithium compounds, barium alkyl phenolates, alkoxy or phenoxy silicon compounds, and alkali metal salts of ethylene glycol monoallyl ether.

[Phase] Organolithium compound, barium alkylphenolate, alkoxy or phenoxy aluminum compound,
A catalyst consisting of an alkali metal salt of ethylene glycol monoallyl ether.

■ Catalyst systems whose main components are organomagnesium compounds and/or organoalkali metal compounds, organic alkaline earth metal compounds (excluding organomagnesium compounds), and organoaluminum compounds (Patent Application No. 62-25387
Specification No. 5).

■ Organic barium aluminum compound (art complex)
, organic barium aluminum compound (art complex),
and a catalyst system whose main component is a lithium compound (patent application 1986)
-43570 specification).

(2) Catalyst systems containing barium compounds, organoaluminium compounds, organomagnesium compounds, organolithium alkoxide compounds and/or organolithium amide compounds as main components (Japanese Patent Application No. 63-60210).

The catalyst system may include tetrahydrofuran, ethylene glycol, ethylene glycol dialkyl ester, ethylene glycol diallyl ether, alkali metal salt of ethylene glycol monoalkyl ether, alkali metal salt of ethylene glycol monoallyl ether, alkali metal salt of dialkylaminoethanol, etc. An ether compound may be used in combination.

Furthermore, when preparing the catalyst system, a conjugated diene may be used in combination as necessary.

The conjugated dienes used for catalyst preparation are isoprene, 1.3-
7'tadiene, 1,3-pentadiene, etc. are used. Although a conjugated diene or an ether compound is not essential as a catalyst component, the catalytic activity of the catalyst component is further improved by using them together.

The catalyst can be prepared, for example, by reacting the catalyst system dissolved in an inert organic solvent and, if necessary, a conjugated diene or ether compound. At that time, the order of addition of each component may be arbitrary.

It is preferable to mix, react, and age these components in advance in order to improve polymerization activity and shorten the polymerization initiation induction period. It's okay.

In the case of the catalyst system as described above, since the resulting trans polybutadiene has a long trans bond chain, elongated crystallinity is suitably expressed.

Since the above-mentioned high trans polybutadiene production catalyst system is a living catalyst, by adding an appropriate amount of tin halide etc. in the late stage of polymerization, it is possible to
As described in Japanese Patent Application No. 1, the terminals of the polymer can be modified, thereby improving the dispersibility of microcarbon in the polymer, which is more advantageous in achieving both wear resistance and processability.

Examples of polymerization solvents include inert organic solvents, such as aromatic hydrocarbon solvents such as benzene, toluene, and xylene, aliphatic hydrocarbon solvents such as n-pentane, n-hexane, n-butane, and cyclohexane, and methyl cyclohexane. Alicyclic hydrocarbon solvents such as benzene, cyclohexane, and mixtures thereof can be used.

The polymerization temperature is usually -20'C to 150C, preferably 30 to 120C. The polymerization reaction may be carried out batchwise or continuously.

Note that the monomer concentration in the solvent is usually 5 to 50% by weight,
Preferably it is 10 to 35% by weight.

In addition, in order to prevent deactivation of the catalyst system and polymer used in this invention in order to produce a polymer, it is necessary to avoid mixing compounds with a deactivation effect such as oxygen, water, or carbon dioxide gas into the polymerization system as much as possible. Consideration must be taken to eliminate this problem.

After the polymerization is completed, steam is blown into the polymer solution to remove the solvent, or a poor solvent such as methanol is added to solidify the polymer, and then dried with a hot roll or under reduced pressure to obtain a butadiene polymer. be able to.

Alternatively, a butadiene-based polymer can also be obtained by directly removing the solvent from the polymer solution under reduced pressure.

The most suitable inorganic filler for use in the rubber composition of this invention is carbon black, but other fillers include silicon dioxide (silica), calcium carbonate, titanium dioxide,
Shiraika etc. can be used. When these are used, light-colored formulations with excellent weather resistance, ozone resistance, crack growth resistance, and fracture strength are also possible.

The rubber composition of the present invention has excellent weather resistance, ozone resistance, crack growth resistance, and fracture properties, and can be used as a tire outer skin member,
That is, it can be suitably used for either or both of the sidewall part and the tread part of a tire. Such a tire has significantly improved durability and appearance due to the characteristics of the rubber composition.

(Examples) Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Various measurements in the examples were performed by the following methods.

(1) Microstructure of polybutadiene: Determined by infrared absorption spectroscopy (Moleguchi) method.

(2) Tensile properties: Performed according to JIS K 6301.

(3) Crack growth resistance: test piece 60mm x 100mm
An initial flaw of 0.31 TIITl was placed in the center of X 1.0 mm, and an extensional strain was applied under conditions of a vibration frequency of 300 cycles/min and a strain of 50%, and evaluation was performed based on the time it took for this to grow to 20 mm.

(4) Weather resistance: test piece 20mm x 100mm x
1. Stretch a 0mm rubber plate by 100% and heat it at 40°C.
The sample was left in an ozone bath with an ozone concentration of 50 ppm, and evaluated based on the time until cracks were visible to the naked eye.

Table 1 shows the name and properties of the polybutadiene (Bll) used.

Table 1 The larger the value, the better the crack growth resistance.

*1 Measured using an infrared spectrophotometer *2 JSRBR01 Table 2 shows the properties of the ethylene propylene genter polymer used.

Table 2 All of the EPDMs shown in Table 2 are commercially available products, and the ethylene content and iodine value in the table are the published data values. Weight average molecular weight, Mw is measured by GPC method,
Calculated in terms of polystyrene.

The above rubber was compounded according to the compounding recipe shown in Table 3, and 14
A test piece was prepared by vulcanization at 5°C for 40 minutes.

The details of the formulation are further shown in Tables 4 and 5 together with the test results.

Book I ENB: Ethylidene norbornene Table 3 *1 *2 Made by Japan Synthetic Rubber Co., Ltd. Chlorobutyl 1068 Made by Japan Synthetic Rubber Co., Ltd. SBR1500 (emulsion polymerization) Book 4 Tetramethylthiuram monosulfide test results in the 4th table
- Shown in Table 6.

Table 4 shows the influence of the microstructure and loading of high trans BR. Rubber made by blending conventional cis-BR with EPDM has poor crack growth resistance and fracture strength. On the other hand, when 20 to 80 parts by weight of the transformer BRB and C containing 75 to 90% of the transformer alloy of the present invention are added, the fracture strength and crack growth resistance are significantly improved while maintaining good weather resistance. be done.

In Table 5, olefin rubber (EPDM A)
By adding 0 parts or more, weather resistance is significantly improved, but if it exceeds 50 parts by weight, crack growth resistance and fracture strength are poor.

Table 6 shows the influence of the structural factors of EPDH.

It can be seen that when EPDM having an ethylene content of 68 to 85 mol%, a weight average molecular weight of 250,000 or more, and an iodine value of 10 or more is blended, the fracture strength and crack growth resistance are excellent.

) 1J = polybutadiene with 71% trans binding gold (trans B
Production of R-A') Under a nitrogen atmosphere, 2400 g of cyclohexane and 600 g of 1,3-butadiene were charged into a stainless steel polymerization reactor with an internal volume of 7 and equipped with a stirrer, and the mixture was heated at 65°C.
After adjusting to barium dinonyl phenoxide 1.7
An ate complex obtained by reacting mmol and 6.8 mmol of triethylaluminum at 70°C for 30 minutes, 8.5 mmol of 1,3-butadiene, 6.8 mmol of n-butyllithium, and tetrahydrofurfuryloxyridium. After further reacting 4.0 mmol at 70°C for 30 minutes, the resulting dark yellow-red transparent solution was charged into the polymerization reactor to initiate polymerization.

Polymerization was carried out for 40 minutes at an elevated temperature, and after reaching 100°C, polymerization was carried out for an additional 30 minutes.

The conversion rate of the charged monomer into polymer was 94%.

Add 2 to the polymer solution thus obtained as a stabilizer.
．． Add 5 g of 6-dibutyl-p-cresol, remove the solvent by steam stripping and heat to 110°C.
A polymer was obtained by roll drying.

The amount of trans-1,4 bonded gold in the butadiene portion of the polymer is 71%, the amount of vinyl bonded gold is 6%, and the Mooney viscosity is 40.
Met.

The properties of this polymer are shown in Table 1.

1 Thought, 1 Polybutadiene with 77% trans-bound gold (trans B
Production of R-B) In the method of Reference Example 1, the catalyst n-butyllithium 6.
0 mmol, tetrahydrofurfuryloxylithium4.
Polymerization was carried out in the same manner except that 0 mmol was used.

The properties of this polymer are shown in Table 1.

Polybutadiene (trans B) with 85% of trans binding gold content
Production of R-C) Under a nitrogen atmosphere, 24.5. OOg, 1.3-
Add 600g of butadiene and heat the mixture at 65°.
After adjusting to C, barium dinonyl phenoxide 1.
An ate complex obtained by reacting 7 mmol of triethylaluminum with 6.8 mmol of triethylaluminum at 70°C for 30 minutes, 17 mmol of 1,3-butadiene, 5.1 mmol of n-butyllithium, and 5.1 mmol of tetrahydrofurfuryloxylithium. After further reacting 1 mmol at 60°C for 30 minutes, the resulting dark yellow-red transparent solution was charged into the polymerization reactor to initiate polymerization.

Polymerization was carried out for 40 minutes at an elevated temperature, and after reaching 80°C, polymerization was carried out for an additional 40 minutes.

The conversion rate of the charged monomer to polymer was 92%.

Add 2 to the polymer solution thus obtained as a stabilizer.
, 6-G was added with 5 g of monobutyl-p-cresol, and the solution was removed by steam stripping and heated to 110°C.
A polymer was obtained by roll drying.

The amount of trans-1,4 bond gold in the butadiene portion of the polymer is 85%, the amount of vinyl bond gold is 3%, and the Mooney viscosity is 40.
Met.

The properties of this polymer are shown in Table 1.

Station 11 Tsusaki Polybutadiene with 92% trans binding (trans BR-
Production of D) Polymerization was carried out in the same manner as in Reference Example 3 except that dibutylmagnesium was used instead of n-butyllithium as a catalyst.

The properties of this polymer are shown in Table 1.

Next, the rubber compositions of Comparative Example 1, Example 1, and Example 2 were applied to the tread and sidewall of a passenger car radial tire 16551713 to make a tire prototype. 0.3m in the part
Initial scratches were made at 10 locations each with a length of 500 m, and each was run for 50,000 km using an outdoor drum tester to evaluate the growth of the scratches.

Compared to the trial tire equipped with the rubber composition of Comparative Example 1, the trial tire equipped with the rubber composition of Example 1 and the rubber composition of Example 2 had no scratches in both the tread and sidewall areas. It was confirmed that the growth was extremely small.

(Effect of the invention) 1. High trans polybutadiene rubber containing 4-trans bond units within the range of 75 to 90% by weight, and EPDM
The tire rubber composition of the present invention, which is formed by blending specific amounts of halogenated butyl rubber, other diene rubber, and an inorganic photonic agent, has better weather resistance than conventional rubber compositions containing cis-polybutadiene. This is a rubber composition with improved crack growth resistance and fracture strength while maintaining the same or higher properties.

Furthermore, tires using this rubber composition in the tread and/or sidewall have improved weather resistance and flex crack resistance, and improved durability and appearance.

Continuation of the procedure Correction

Claims (4)

[Claims] 1. High trans polybutadiene rubber containing 1,4-trans bond units in the range of 75 to 90% by weight 20 to 8
0 parts by weight, 20 to 50 parts by weight of at least one olefin rubber selected from the group consisting of terpolymers of ethylene, propylene and diene, and halogenated butyl rubber, and 0 to 60 parts by weight of other diene rubbers. 20 to 150 parts by weight of inorganic filler per 100 parts by weight of rubber.
A vulcanizable tire rubber composition comprising parts by weight. 2. The rubber composition for a tire according to claim 1, wherein the terpolymer is a rubber having an ethylene content of 68 to 85 mol%, a weight average molecular weight of 250,000 or more, and an iodine number of 10 or more. 3. The rubber composition for tires according to claim 1, wherein the other diene rubber is an isoprene rubber. 4. Inorganic fillers include carbon black, silicon dioxide,
The rubber composition for tires according to claim 1, wherein the filler is selected from the group consisting of calcium carbonate and titanium dioxide.