JP4731453B2 - Rubber vulcanizate - Google Patents

Description

The present invention relates to a rubber vulcanizate obtained by vulcanization of a modified rubber which is particularly useful for automobile tires and has both a high elastic modulus and high wet skid resistance.

  Conventionally, as an automobile tire rubber, a rubber composition containing polybutadiene rubber (BR) or styrene-butadiene rubber (SBR) as a main component, and other natural rubber is used.

  In recent years, demands for lower fuel consumption of automobiles and driving safety requirements on snow and ice have increased, and automobile tire tread rubber has low rolling resistance (ie, high rebound resilience) and road surface grip on snow and ice (ie, Development of a rubber material having a large wet skid resistance) is desired. However, a rubber having high impact resilience such as polybutadiene rubber (BR) tends to have low wet skid resistance, whereas styrene-butadiene rubber (SBR) has high wet skid resistance but also high rolling resistance. was there.

  Conventionally, many methods for chemically modifying a low cisdiene rubber with a modifier in the presence of a lithium catalyst have been proposed as a method for solving the above problems. For example, a method of modifying low cis BR with a benzophenone compound has been proposed in Patent Document 1 and Patent Document 2, and it has been reported that rolling resistance of automobile tires is small, wet skid resistance is large, and impact resilience is also improved. Has been.

  In Patent Document 3, Patent Document 4, and Patent Document 5, by reacting a diene rubber having an active alkali metal terminal with a nitroamino compound, a nitro compound, a nitroalkyl compound, etc., it has excellent rebound resilience, low temperature It is stated that a rubber with low hardness can be obtained.

However, low cis BR has insufficient wear resistance, and this problem cannot be solved even by modification. In addition, even the SBR has a low impact resilience, and even after modification, this defect cannot be sufficiently solved.
JP 58-162604 A JP 59-117514 A Japanese Examined Patent Publication No. 6-53766 Japanese Patent Publication No. 6-57769 Japanese Patent Publication No. 6-78450

  The present invention has a high abrasion resistance, a low rolling resistance and a good wet skid property by modifying a diene rubber having a high cis-1,4-structure content, and particularly as a rubber for automobile tire treads. An object of the present invention is to provide a rubber composition containing a diene rubber that has become suitable.

In the present invention, 80% or more of the repeating diene units have a cis-1,4 structure, a Mooney viscosity (ML _{1 + 4} , 100 ° C.) is in the range of 20 to 80, and measured by gel permeation chromatography. The diene rubber having a weight average molecular weight in the range of 200,000 to 1,000,000 is modified with a silicon compound having an amino group and an alkoxy group in advance so that the Mooney viscosity is increased by 1 or more as compared with that before the modification. A rubber vulcanizate obtained by heating a composition containing the modified diene rubber and a vulcanizing agent .

Preferred embodiments of the invention will now be described.
(1) The diene rubber is modified in the presence of a catalyst selected from the group consisting of aluminum halides and alkyl halides.
(2) Increase in Mooney viscosity is in the range of 2-10.
(3) The diene rubber is polybutadiene rubber.

  The modified diene rubber used in the present invention is modified by a silicon compound having an amino group and an alkoxy group, and the Mooney viscosity of the modified product is increased by 1 or more compared with that before modification, thereby increasing the gel fraction. The rubber composition of the present invention is particularly useful as an automobile tire material because it has achieved an increase in tensile strength, an improvement in impact resilience, and an improvement in wet skid resistance.

In the diene rubber to be modified in the present invention, 80% or more (preferably 90% or more, more preferably 95% or more) of repeating diene units has a cis-1,4 structure, and Mooney viscosity (ML _{1 +} 4,100 ° C.) in the range of 20-80, and diene rubber having a weight average molecular weight measured by gel permeation chromatography in the range of 200,000-1,000,000 (single weight of conjugated diene) It 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 with a repetitive diene structure of less than 80% is not preferred because it has low impact resilience and the object of the present invention cannot be achieved.

  Specific examples of the diene rubber include polybutadiene (BR), polyisoprene (IR), styrene-butadiene rubber (SBR), isoprene-butadiene rubber, and nitrile-butadiene rubber (NBR). BR is preferred. In general, a commercially produced product may be used, or a polymerized or copolymerized product as appropriate.

  The diene rubber modifier used in the present invention includes an amino group (preferably an aminoalkyl group bonded to an alkyl group having 1 to 6 carbon atoms) and an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms). ), And an aminoalkylalkoxysilane compound is preferable. Examples of specific compounds include 3-aminopropyldimethylmethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 3 -Aminopropylmethyldiethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldimethylbutoxysilane, 3-aminopropylmethyldibutoxysilane, 3- (2-aminoethylaminopropyl) dimethoxymethylsilane, 3- ( 2-aminoethylaminopropyl) dimethoxyethylsilane, 3- (2-aminoethylaminopropyl) dimethoxypropylsilane, 3- (2-aminoethylaminopropyl) dimethoxybutylsilane, 3- (2-amino Tilaminopropyl) diethoxymethylsilane, 3- (2-aminoethylaminopropyl) trimethoxysilane, 3- (2-aminoethylaminopropyl) triethoxysilane, 3- (2-aminoethylaminopropyl) tributoxysilane Etc. Among these compounds, 3-aminopropyltrimethoxysilane, 3- (2-aminoethylaminopropyl) dimethoxymethylsilane, and 3- (2-aminoethylaminopropyl) trimethoxysilane are particularly preferable. These modifiers may be used alone or in combination of two or more.

  As a method for modifying a diene rubber with a modifier in the present invention, the modifier and the diene rubber may be brought into contact with each other in an organic solvent to generate a modification reaction, or a diene rubber polymerization solution may be used. It can be carried out by directly adding a modifier. As other methods, direct kneading modification using an extrusion kneader or the like is also possible.

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

  The organic solvent used for the modification reaction can be freely used as long as it does not react with the diene rubber. Usually, the same solvent as used for the production of the diene rubber is used. Specific examples thereof include aromatic hydrocarbon solvents such as benzene, chlorobenzene, toluene and xylene, and aliphatic carbonization of 5 to 10 carbon atoms such as n-heptane, n-hexane, n-pentane and n-octane. Examples thereof include hydrogen solvents, cycloaliphatic hydrocarbon solvents such as cyclohexane, methylcyclohexane, tetralin, and decalin. Further, methylene chloride, tetrahydrofuran and the like can also be used.

  The temperature of the reaction solution for the modification reaction is preferably in the range of 0 to 100 ° C, and particularly preferably in the range of room temperature to 70 ° C. If the temperature is too low, the modification reaction proceeds slowly, and if the temperature is too high, the polymer is easily gelled. There is no particular limitation on the time for the modification reaction, but it is usually preferably in the range of 0.5 to 6 hours. If the modification 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 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, and more preferably 3 to 50 mmol with respect to 100 g of the diene rubber. If the amount used is too small, the amount of nitrogen element introduced into the modified diene rubber will be small, and the modification effect will be small. If the amount used is too large, unreacted modifier remains in the modified diene rubber, which is not preferable because it takes time to remove it.

  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 0.05 to 50 mmol, more preferably 0.08 to 20 mmol, with respect to 100 g of the diene rubber.

  The modified diene rubber used in the present invention is blended alone or blended with other synthetic rubber or natural rubber, and if necessary, is oil-extended with a process oil, and then a filler such as carbon black, a vulcanizing agent, a vulcanizing agent. It is vulcanized by adding a sulfur accelerator and other ordinary compounding agents, and is used as a rubber composition required for mechanical properties and wear resistance of various industrial articles such as tires, hoses, belts, and the like. The modified diene rubber can also be used as a modifier for plastic materials.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, these do not limit the objective of this invention.
The Mooney viscosity (ML _{1 + 4} , 100 ° C.), cis-1,4-structure amount, molecular weight and molecular weight distribution, nitrogen content, and gel content of the rubber-like polymers obtained in the following Examples and Comparative Examples The rate was measured by the following method.

(1) Mooney viscosity (ML _{1 + 4} , 100 ° C.): Measured for 4 minutes after preheating at 100 ° C. for 1 minute using a Mooney viscometer (SMV-200) manufactured by Shimadzu Corporation according to JIS-K6300. And expressed as the Mooney viscosity of rubber (ML _{1 + 4} , 100 ° C.).
(2) cis-1,4-structure: cis-1,4-structure is calculated by measuring the microstructure of the polymer using a 0.4% by weight carbon disulfide solution by infrared absorption spectrum analysis. did.

(3) Molecular weight and molecular weight distribution: Calculated using a calibration curve obtained from a molecular weight distribution curve of gel permeation (permeation) chromatography (GPC, manufactured by Tosoh Corporation) at a temperature of 40 ° C. using polystyrene as a standard substance and polystyrene as a solvent. Thus, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined, and the weight average molecular weight (Mw) and the molecular weight distribution spread were indicated as Mw / Mn.
(4) Nitrogen content: quantified by Kjeldahl method according to JIS-K0102.

(5) Method for measuring gel fraction: About 0.5 g of an unvulcanized rubber sample is taken, finely cut, and the weight is accurately measured (Rg). The weight of a 100-mesh stainless steel basket is precisely weighed (Kg), and the weighed sample is transferred to the cage and the weight is measured (Rg + Kg). This is immersed in a bottle with a stopper containing 100 mL of toluene and left at 23 ° C. for 24 hours. Next, the basket is pulled up, dried at 23 ° C. for 24 hours, and then dried under reduced pressure for 24 hours so as to become a constant weight at 70 ° C., and the toluene-insoluble matter is accurately weighed together with the cage (Gg + Kg). The gel fraction was determined.

Gel fraction (%) = 100 × [G− (R × (filler part by weight / total rubber composition part by weight))] / [(R × (rubber part by weight / total rubber composition part by weight))]
However,
Part by weight of filler: part by weight of carbon black in Table 1 Total part by weight of rubber composition: Total part by weight of the total composition in Table 1 Part by weight of rubber: Total weight of rubber component (NR + BR or modified BR) in Table 1 Part

In addition, 300% elastic modulus, rolling resistance index, tensile strength, and wet skid resistance index were measured by the following methods.
(1) 300% elastic modulus (M ₃₀₀ ): measured by JIS-K6301 and indicated by a modulus at 300%.
(2) Rolling resistance index: Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd., tan δ was measured under the conditions of a temperature of 70 ° C., an initial distortion of 10%, and a dynamic strain of 2%. The index was determined. A larger index value means 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 in accordance with JIS-K6301.
(4) Wet skid resistance index: Measured according to the method of ASTM-E303-83 using a portable skid resistance meter manufactured by Stanley. It shows that it is so favorable that a numerical value is large with the parameter | index of the grip characteristic (driving performance, braking performance, and steering performance) on the wet road surface.

[Example 1]
Polybutadiene rubber (Ube Industries, UBEPOL-340L, ML _{1 + 4} , ML _{1 + 4} , 100 ° C. = 33, cis-1) produced by a cobalt catalyst system in a 2 liter glass separable flask equipped with a stirrer and a temperature controller. , 4 structure = 98%, number average molecular weight Mn by GPC = 240,000, weight average molecular weight Mw = 585,000, Mw / Mn = 2.44) 130 g and 1.2 liters of toluene were introduced, and the contents were While stirring, the temperature was raised to 60 ° C. to completely dissolve the polybutadiene rubber. Next, 10 mmol of a modifier (3- (2-aminoethylaminopropyl) dimethoxysilane) previously dispersed in tetrahydrofuran and 7.5 mmol of a catalyst (aluminum chloride) were added, and the mixture was denatured at 60 ° C. for 2 hours. Reaction was performed.

  After completion of the reaction, the reaction mixture was cooled to room temperature, the reaction mixture was transferred to a 3 liter flask, and 1.2 liters of methanol was added to precipitate the modified polybutadiene rubber. This precipitation-modified polybutadiene rubber was separated with a 300-mesh wire mesh, the modified polybutadiene rubber was dissolved in 1 liter of toluene, and then 1.2 liters 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 1010, manufactured by Ciba Geigy Japan)] was modified. The polybutadiene was kneaded and mixed with 1000 ppm and vacuum-dried at 100 ° C. for 1 hour to obtain the desired modified polybutadiene rubber.

[Example 2]
A modified polybutadiene rubber was produced in the same manner as in Example 1, except that the same amount of 3- (2-aminoethylaminopropyl) trimethoxysilane was used as the modifier and 10 mmol of ethyl bromide was used as the catalyst.

[Example 3]
A modified polybutadiene rubber was produced in the same manner as in Example 1, except that the same amount of 3-aminopropyltrimethoxysilane was used as the modifier and 2 mmol of aluminum chloride was used as the catalyst.

[Example 4]
A modified polybutadiene rubber was produced in the same manner as in Example 1 except that the same amount of 3-aminopropyltrimethoxysilane was used as the modifier and 5 mmol of aluminum chloride was used as the catalyst.

[Example 5]
A modified polybutadiene rubber was produced in the same manner as in Example 1 except that the same amount of 3-aminopropyltrimethoxysilane was used as the modifier and 7.5 mmol of aluminum chloride was used as the catalyst.

[Comparative Example 1]
Unmodified polybutadiene rubber (UBEPOL-340L manufactured by Ube Industries, Ltd.) was used as a comparative polybutadiene rubber.

[Comparative Example 2]
A modified polybutadiene rubber was produced in the same manner as in Example 1 except that the same amount of bis (dimethylamino) dimethylsilane was used as the modifier.

[Vulcanized properties]
A rubber composition was prepared by blending the polybutadiene rubber (modified BR or unmodified BR) obtained in each Example and Comparative Example 1 as shown in Table 1. Next, the obtained blend was press vulcanized at 150 ° C. for 30 minutes, and the physical properties of the vulcanized product were obtained by the above-described methods by the resilience (300% elastic modulus), rolling resistance index, tensile strength, and wet skid. The resistance was measured and shown in Table 2.

Table 1 ────────────────────
Compounding amount (parts by weight)
────────────────────
Modified BR or BR 70
NR 30
Carbon black (ISAF) 45
Zinc flower (ZnO) 3
Stearic acid 1
Vulcanization accelerator * 1
Sulfur 1.5
────────────────────
* N-tert.-Butyl-2-benzothiazolylsulfenamide

Table 2 ──────────────────────────────────
Example Comparative Example 1
1 2 3 4 5 (unmodified)
──────────────────────────────────
Nitrogen content (ppm) 197 437 42 87 207 Undetected Mooney viscosity 38 42 35 37 38 33
(Increase due to denaturation) 5 9 2 4 5-
Gel fraction (%) 45.0 45.6 35.2 39.1 42.7 33.5
──────────────────────────────────
300% elastic modulus (MPa) 14.1 13.9 12.0 12.6 13.2 11.6
Rolling resistance index 108 109 102 104 106 100
Tensile strength (MPa) 22.8 23.3 20.8 21.07 21.7 20.0
Wet skid index 108 109 101 103 107 100
──────────────────────────────────

  The modified polybutadiene rubber of Comparative Example 2 was similarly compounded as shown in Table 1 to prepare a rubber composition, press vulcanized, and the physical properties of the vulcanized product were rebounded in the same manner. Elasticity (300% elastic modulus), rolling resistance index, tensile strength, and wet skid resistance were measured. The results are shown below.

  Nitrogen content (ppm): 12, Mooney viscosity (increase by modification): 33.5 (0.5), gel fraction (%): 34.0, 300% elastic modulus (MPa): 11.7, rolling Resistance index: 101, Tensile strength (MPa): 20.3, Wet skid index: 100

  That is, in place of the silicon compound having an amino group and an alkoxy group of the modifier used in the present invention, bis (dimethylamino) dimethylsilane, which is a silane compound having an amino group and an alkyl group, may be used to modify the diene. It can be seen that it does not cause a significant improvement in the properties of the rubber.

Claims (2)

More than 80% of the repeating diene units have a cis-1,4 structure, a 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 Modified diene system in which a diene rubber having a molecular weight of 200,000 to 1,000,000 is previously modified with a silicon compound having an amino group and an alkoxy group so that the Mooney viscosity is increased by 1 or more compared with that before the modification. A rubber vulcanizate obtained by heating a composition containing rubber and a vulcanizing agent . The rubber vulcanizate according to claim 1, wherein the diene rubber is polybutadiene rubber.