JP2000159813A - Modified diene rubber and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rubber materials reduced in rolling resistance and excellent in wet skid resistance when used as the rubber materials for automobile tires. SOLUTION: A modified diene rubber is obtained by modifying a diene rubber having not less than 80% repeating units of a cis-1,4-structure, a Mooney viscosity (ML1+4, 100 deg.C) of 20-80 and, a weight-average molecular weight, measured by gel permeation chromatography(GPC), of 200,000-1,000,000 with diaminobenzoic acid, and also the Mooney viscosity of the modified product is increased by not less than one compared with that before the modification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified rubber having a high modulus of elasticity and a high wet skid resistance, particularly useful for automobile tires.

[0002]

2. Description of the Related Art Hitherto, as an automobile tire rubber, a rubber composition containing polybutadiene rubber (BR) or styrene-butadiene rubber (SBR) as a main component and a natural rubber mixed therewith has been used.

[0003] In recent years, there has been an increasing demand for low fuel consumption of automobiles and a demand for running safety on snow and ice.
It is desired to develop a rubber material having a large rebound resilience) and a large road surface grip on snow and ice (that is, wet skid resistance). However, rubber having high rebound resilience such as polybutadiene rubber (BR) tends to have low wet skid resistance, while styrene-butadiene rubber (SBR) has high wet skid resistance but high rolling resistance. was there.

Hitherto, as a method for solving the above-mentioned problems, many methods have been proposed in which a low cis-diene rubber is chemically modified with a modifier in the presence of a lithium catalyst. For example, a method of modifying low cis BR with a benzophenone compound has been proposed in JP-A-58-162604 and JP-A-59-117514, in which the rolling resistance of an automobile tire is small and the wet skid resistance is large. It is also reported that the rebound resilience is improved.

JP-B-6-53766, JP-B-6-53766
No. 57769 and Japanese Patent Publication No. 6-78450 disclose that a diene rubber having an active alkali metal terminal is reacted with a nitroamino compound, a nitro compound, a nitroalkyl compound, etc., so that it has excellent rebound resilience and low temperature. It is described that a rubber having a low hardness can be obtained.

However, low cis BR has insufficient abrasion resistance, and modification thereof does not solve this problem. Further, even with SBR, the rebound resilience is low, and even after modification, this defect cannot be sufficiently solved.

[0007]

SUMMARY OF THE INVENTION The present invention provides a high cis-
A diene rubber having a high abrasion resistance, a low rolling resistance and a good wet skid property by modifying a diene rubber having a 1,4-structure content is provided, which is particularly suitable as a rubber for an automobile tire tread. It is intended to do so.

[0008]

According to the present invention, 80% or more of the repeating units have a cis-1,4 structure and a Mooney viscosity (ML _{1 + 4} , 100 ° C.) in the range of 20 to 80,
And the weight average molecular weight measured by gel permeation chromatography is 200,000 to 1,000,
000 is modified by diaminobenzoic acid, and the Mooney viscosity of the modified product is increased by one or more as compared to before the modification (preferably 2 to 1).
0, more preferably 3 to 8).

According to the present invention, more than 80% of the repeating units have a cis-1,4 structure and a Mooney viscosity (ML).
_{1 + 4} , 100 ° C.) in the range of 20 to 80 and a diene rubber having a weight average molecular weight in the range of 200,000 to 1,000,000 as measured by gel permeation chromatography. A modified diene rubber, which is modified with diaminobenzoic acid in the presence of a catalyst containing titanium, neodymium, or the like, and the Mooney viscosity of the modified product is increased by at least one as compared to before the modification. There is also a law.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the diene rubber to be modified in the present invention, 80% or more (preferably 90% or more, more preferably 95% or more) of the repeating unit is cis-based.
1,4 structure and Mooney viscosity (ML _{1 + 4} , 100
C.) in the range of 20 to 80 and a weight-average molecular weight measured by gel permeation chromatography in the range of 200,000 to 1,000,000 (a homopolymer rubber or conjugated diene rubber). (Polymer rubber), and is preferably a diene rubber obtained by homopolymerizing or copolymerizing a conjugated diene using a cobalt, nickel, titanium, or neodymium catalyst system. A diene rubber having a cis-1,4-structure having a repeating structure of less than 80% is not preferred because it has low rebound resilience and cannot achieve the object of the present invention.

Specific examples of the diene rubber include polybutadiene (BR), polyisoprene (IR), styrene-butadiene rubber (SBR), isoprene-butadiene rubber, and nitrile-butadiene rubber (NBR). Preferably it is BR. Generally, commercially produced products may be used, or those obtained by appropriate polymerization or copolymerization may be used.

The diene rubber modifier used in the present invention is:
Diaminobenzoic acid, and specific examples of the compound include 2,3-diaminobenzoic acid, 2,4-diaminobenzoic acid, 2,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 3,5 -Diaminobenzoic acid. Particularly, 3,4-diaminobenzoic acid and 3,5-diaminobenzoic acid are preferred. These modifiers may be used alone or in combination of two or more.

The method for modifying a diene rubber with a modifier in the present invention may be such that a modifier and a diene rubber are brought into contact in an organic solvent to cause a modification reaction. It can be carried out by adding a modifier directly to the polymerization solution. As another method, it is also possible to directly knead and modify using an extrusion kneader or the like.

When the modification reaction rate is low, an aluminum halide or an alkyl halide can be used as a catalyst to increase the reaction rate. Examples of aluminum halides include aluminum chloride, aluminum bromide, aluminum iodide and the like. Examples of the alkyl halide include alkyl halides having 1 to 6 carbon atoms such as ethyl bromide, ethyl iodide, butyl chloride, butyl bromide, and butyl iodide.

As the organic solvent used for the modification reaction, any organic solvent which does not react with the diene rubber can be used freely. Usually, the same solvent as used in the production of the diene rubber is used. Specific examples thereof include aromatic hydrocarbon solvents such as benzene, chlorobenzene, toluene and xylene, n-heptane, n-hexane, and n-hexane.
Examples thereof include aliphatic hydrocarbon solvents having 5 to 10 carbon atoms such as pentane and n-octane, and alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, tetralin, and decalin. In addition, methylene chloride, tetrahydrofuran and the like can also be used.

The temperature of the reaction solution for the denaturation reaction is from 0 to 100
C. It is preferably in the range of room temperature, particularly preferably in the range of room temperature to 70C. If the temperature is too low, the progress of the modification reaction is slow, and if the temperature is too high, the polymer tends to gel. The time of the denaturation reaction is not particularly limited, but is preferably in the range of usually 0.5 to 6 hours. If the denaturation reaction time is too short, the reaction does not proceed sufficiently, and if the time is too long, the polymer tends to gel.

The amount of the diene rubber in the modification reaction solution is usually in the range of 5 to 500 g, preferably 20 to 200 g, more preferably 30 to 100 g per liter of the solvent.

The amount of the modifier used in the modification reaction is usually in the range of 0.01 to 150 mmol, preferably 1 to 100 mmol, more preferably 3 to 50 mmol, per 100 g of the diene rubber. If the amount is too small, the amount of nitrogen element introduced into the modified diene rubber becomes small, and the modifying effect is small. If the amount is too large, the unreacted modifier will remain in the modified diene rubber, and it will be troublesome to remove it, which is not preferable.

In carrying out the modification reaction, it is preferable to use a catalyst depending on the type of the modifying agent. The amount of the catalyst used in this reaction is usually 0.01 to 100 mmol, preferably 0.1 to 100 g per 100 g of the diene rubber.
It is from 0.5 to 50 mmol, more preferably from 0.08 to 20 mmol.

The modified diene rubber of the present invention is compounded alone or blended with another synthetic rubber or natural rubber, and if necessary, oil-extended with a process oil, and then a filler such as carbon black, a vulcanizing agent. It is vulcanized by adding a vulcanization accelerator and other usual compounding agents, and is used for rubber applications requiring mechanical properties and abrasion resistance of tires, hoses, belts, and other various industrial products. It can also be used as a modifier for plastic materials.

[0021]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but these do not limit the purpose of the present invention. The rubbery polymers obtained in the following Examples and Comparative Examples have Mooney viscosities (ML _{1 + 4} , 100
C), cis-1,4-structure weight, molecular weight and molecular weight distribution,
The nitrogen content and the gel fraction were measured by the following methods.

(1) Mooney viscosity (ML _{1 + 4} , 100
° C): 100 according to JIS-K6300 using a Mooney viscometer (SMV-200) manufactured by Shimadzu Corporation.
After preheating at 1 ° C. for 1 minute, the viscosity was measured for 4 minutes and indicated as the Mooney viscosity of the rubber (ML _{1 + 4} , 100 ° C.). (2) Cis-1,4-structure amount: The microstructure of the polymer was measured by a 0.4% by weight carbon disulfide solution by infrared absorption spectrum analysis to calculate the cis-1,4-structure amount. did.

(3) Molecular weight and molecular weight distribution: A calibration curve obtained from a molecular weight distribution curve of gel permeation (permeation) chromatography (manufactured by Tosoh Corporation, GPC) at a temperature of 40 ° C. using polystyrene as a standard substance and tetrahydrofuran as a solvent. The weight average molecular weight (M
w) and the number average molecular weight (Mn) are determined, and the weight average molecular weight (Mw) and Mw / M
n. (4) Nitrogen content: Quantified by the Kjeldahl method according to JIS-K0102.

(5) Method of measuring gel fraction: About 0.5 g of an unvulcanized rubber sample is taken, cut into small pieces, and accurately weighed (Rg). The weight of a 100-mesh stainless steel basket is precisely weighed (Kg), the entire weighed sample is transferred to a basket, and the weight is measured (Rg + Kg). This is toluene 100m
Immerse in a bottle with a stopper containing L and leave it at 23 ° C. for 24 hours. Then, the basket is pulled up, dried at 23 ° C. for 24 hours, further dried under reduced pressure at 70 ° C. for 24 hours to a constant weight, and the toluene-insoluble matter is accurately weighed together with the basket (Gg + Kg). The gel fraction was determined.

Gel fraction (%) = 100 × [G− (R ×
(Filler parts ÷ rubber composition total parts)] ÷ [(R ×
(Parts by weight of rubber: total parts by weight of rubber composition)] However, parts by weight of filler: parts by weight of carbon black in Table 1 Total parts by weight of rubber composition: total parts by weight of all components in Table 1 Parts by weight of rubber: The rubber components (NR + BR or modified B
R) total weight parts

Also, a 300% elastic modulus, a rolling resistance index,
The tensile strength and wet skid resistance index were measured by the following methods. (1) 300% modulus (M _300): JIS-K6301
And a modulus at 300%. (2) Rolling resistance index: Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho, tan δ was measured at a temperature of 70 ° C., an initial distortion of 10%, and a dynamic strain of 2%, and the rolling resistance was calculated by the following equation. An index was determined. A larger index value indicates a lower rolling resistance, and the rolling resistance may be 100 or more.

Rolling resistance index = 100 × [(value of comparative example (unmodified product)) / (value of example (modified product)]]

(3) Tensile strength: Measured according to JIS-K-6301. (4) Wet skid resistance index: ASTM-E303- using a portable skid resistance meter manufactured by Stanley.
83. Indices of grip characteristics (driving performance, braking performance and steering performance) on a wet road surface indicate that the larger the value, the better.

Example 1 A polybutadiene rubber (Ube Industries, Ltd.) produced using a cobalt catalyst was placed in a 2-liter glass separable flask equipped with a stirrer and a temperature controller.
UBEPOL-340L, ML _{1 + 4} , 100 ° C = 3
3, cis-1,4 structure = 98%, number average molecular weight Mn = 240,300 by GPC, weight average molecular weight Mw = 58
130 g of 5,600 (Mw / Mn = 2.44) and 1.2 liters of toluene were introduced, and the contents were heated to 60 ° C. while stirring to completely dissolve the polybutadiene rubber. Next, 10 mmol of 3,4-diaminobenzoic acid previously dispersed in tetrahydrofuran and 7.5 mmol of a catalyst (aluminum chloride) were added, and 60
The denaturation reaction was performed at 2 ° C. for 2 hours.

After completion of the reaction, the reaction mixture was cooled to room temperature, and the reaction mixture was transferred to a 3-liter flask, and 1.2 liters of methanol was added to precipitate a modified polybutadiene rubber. This modified polybutadiene rubber was separated by a 300-mesh wire net, and the modified polybutadiene rubber was dissolved in 1 liter of toluene. Then, 1.2 liter of methanol was added to precipitate the modified polybutadiene rubber again. After repeating this operation three times, the antioxidant [tetrakis- [methylene-3- (3,5-di-t-
Butyl-4-hydroxyphenyl) propionate] methane (Irganox 101, manufactured by Ciba-Geigy Japan)
[0] with respect to the modified polybutadiene was kneaded at 1000 ppm and dried under vacuum at 100 ° C. for 1 hour to obtain the desired modified polybutadiene rubber.

Example 2 Example 1 was repeated except that the amount of 3,4-diaminobenzoic acid added was changed to 20 mmol and the amount of catalyst (aluminum chloride) used was changed to 20 mmol.
A modified polybutadiene rubber was produced in the same manner as described above.

Example 3 Example 1 was repeated except that the amount of 3,4-diaminobenzoic acid added was changed to 24 mmol and the amount of catalyst (aluminum chloride) used was changed to 20 mmol.
A modified polybutadiene rubber was produced in the same manner as described above.

Example 4 Example 1 was repeated except that the amount of 3,4-diaminobenzoic acid added was changed to 27 mmol and the amount of catalyst (aluminum chloride) used was changed to 27 mmol.
A modified polybutadiene rubber was produced in the same manner as described above.

Example 5 A modified polybutadiene rubber was produced in the same manner as in Example 1, except that 10 mmol of 3,5-diaminobenzoic acid was used as a modifier and 10 mmol of ethyl bromide was used as a catalyst. .

Comparative Example Unmodified polybutadiene rubber (UBEPOL-340L, manufactured by Ube Industries, Ltd.) was used as a comparative polybutadiene rubber.

[Vulcanization properties] Polybutadiene rubber (modified BR or unmodified BR) obtained in each of Examples and Comparative Example 1
Was blended as shown in Table 1 to prepare a rubber composition. Next, the obtained compound was press-vulcanized at 150 ° C. for 30 minutes to determine the physical properties of the vulcanized product by the above-mentioned methods, including rebound resilience (300% modulus), rolling resistance index, tensile strength,
And the wet skid resistance was measured and is shown in Table 2.

[0037]

[Table 1] Table 1 配 Mixing amount (parts by weight) ──────────────── {Modified BR or BR 70 NR 30 carbon black (ISAF) 45 zinc white (ZnO) 3 stearic acid 1 vulcanization accelerator * 1 sulfur 1.5} ──── * N-tert.-butyl-2-benzothiazolylsulfenamide

[0038]

Table 2 Table 2 Example Comparative Example 1 2 3 4 5 ( Undenatured) ───────────────────────────────── Nitrogen content (ppm) 420 520 600 630 370 Undetected Mooney Viscosity 36 39 39 39 38 33 (increase due to denaturation) 36 665- gel fraction (%) 36.20 36.27 38.10 38.24 36.21 33.6 ───────────── 300% elastic modulus (MPa) 12.29 12.54 12.60 13.00 12.27 9.68 Rolling resistance index 110 111 111 112 112 108 100 Tensile strength (MPa) 20.88 20.94 21.27 21.41 20.07 15.87 Wet skid index 108 108 110 110 108 100 ──────────────────────────── ─────

[0039]

The modified diene rubber of the present invention is modified with diaminobenzoic acid, and the Mooney viscosity of the modified product is increased by at least one as compared with that before modification, thereby increasing the gel fraction and the tensile strength. And an improvement in the rebound resilience and the wet skid resistance, and are particularly useful as a material for automobile tires.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuji Nakajima 8-1, Goi Minami Coast, Ichihara-shi, Chiba Ube Industries, Ltd. Chiba Petrochemical Plant (72) Inventor Kiyoshige Muraoka Tsutsui, Chuo-ku, Kobe-shi, Hyogo 2-1-1 Sumitomo Rubber Industries, Ltd. (72) Inventor Noriko Yagi 2-1-1 Tsutsui-machi, Chuo-ku, Kobe-shi, Hyogo F-term in Sumitomo Rubber Industries, Ltd. 4J100 AB02Q AM02Q AS02P AS03P AS03Q CA01 CA04 DA03 DA09 HA61 HB29 HC05 HC47 JA29

Claims (2)

[Claims] (1) 80% or more of the repeating unit is cis-1,
4 structures, Mooney viscosity (ML _{1 + 4} , 100 ° C)
Is in the range of 20 to 80, and the weight average molecular weight measured by gel permeation chromatography is 2
That the diene rubber in the range of 00000 to 1,000,000 has been modified with diaminobenzoic acid, and that the Mooney viscosity of the modified product has increased by one or more compared to before the modification. Characterized modified diene rubber. 2. 80% or more of the repeating units are cis-1,
4 structures, Mooney viscosity (ML _{1 + 4} , 100 ° C)
Is in the range of 20 to 80, and the weight average molecular weight measured by gel permeation chromatography is 2
A diene rubber in the range of 00000 to 1,000,000 is modified with diaminobenzoic acid in the presence of a catalyst containing cobalt, nickel, titanium or neodymium, and the Mooney viscosity of the modified product is reduced. A method for producing a modified diene rubber, wherein the number is increased by one or more as compared to before the modification.