JPH0657769B2 - Modified rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a modified rubber composition which gives a vulcanized rubber having improved impact resilience and improved JIS hardness at low temperature.

More specifically, a diene polymer rubber having an active alkali metal terminal or a conjugated diene polymer rubber to which an alkali metal is added, a general formula, (In the formula, R ₁ and R ₂ represent an alkyl group, and n represents an integer.)
The present invention relates to a modified rubber composition containing, as a rubber component, a modified diene polymer rubber obtained by reacting a nitroalkyl acrylate compound represented by

<Prior Art> Conventionally, conjugated diene-based polymer rubbers such as polybutadiene and butadiene-styrene copolymer rubber have been used as rubbers for automobile tire treads, but in recent years, demand for low fuel consumption of automobiles and snow and ice Due to the requirement of driving safety, a rubber material having a small rolling resistance and a large road surface grip on snow and ice has been desired as a rubber for an automobile tire tread.

The rolling resistance correlates with the impact resilience of the polymer, and the higher the impact resilience, the smaller the rolling resistance.

On the other hand, the road grip on snow and ice is
It is known that there is a correlation with the IS hardness, and the lower the JIS hardness at low temperature, the greater the road surface grip on snow and ice. However, in the existing rubber material, these characteristics were not practically satisfactory.

<Problems to be Solved by the Invention> An object of the present invention is to provide a modified rubber composition comprising a modified diene polymer rubber that enhances impact resilience and reduces JIS hardness at low temperatures.

<Means for Solving Problems> The present inventors have found that a rubber composition containing a conjugated diene polymer rubber as a rubber component has high impact resilience and high J
As a result of repeated intensive studies to lower the IS hardness, an alkali metal-containing diene polymer is reacted with a specific compound,
It was found that a rubber composition containing a modified diene polymer rubber obtained by introducing a specific atomic group into a polymer as a rubber component can achieve the above-mentioned object and completed the present invention. .

That is, the present invention is a rubber composition comprising a rubber component and a compounding agent, a diene polymer rubber having an active alkali metal terminal or a conjugated diene rubber to which an alkali metal is added, a general formula, (In the formula, R ₁ and R ₂ represent an alkyl group, and n represents an integer.)
The present invention relates to a modified rubber composition comprising a modified diene polymer rubber obtained by reacting with a nitroalkyl acrylate compound represented by, in a rubber component, at least 10% by weight.

The alkali metal-containing diene polymer used in the present invention is obtained by polymerizing a diene monomer or the monomer and another monomer copolymerizable therewith with an alkali metal-based catalyst. Regardless of the type of alkali metal bound to the end of the diene polymer, or the polymerization method (eg, solution polymerization, emulsion polymerization, etc.), a diene polymer having a conjugated diene unit in the polymer chain It means that an alkali metal is added by the reaction.

Examples of the diene polymer rubber include 1,3-butadiene, isoprene, 1,3-pentadiene (piperylene), 2,
Polymer or copolymer rubber of conjugated diene monomer such as 3-dimethyl-1,3-butadiene and 1,3-hexadiene, or styrene, α-methylstyrene, vinyltoluene copolymerizable with the conjugated diene monomer and the monomer , Vinylnaphthalene, divinylbenzene, trivinylbenzene, divinylnaphthalene and other aromatic vinyl compounds, acrylonitrile and other unsaturated nitriles, (meth)
Examples thereof include, but are not limited to, a copolymer rubber with an ester of acrylic acid or vinyl pyridine.

Specifically, polybutadiene rubber, polyisoprene rubber,
Examples thereof include butadiene-isoprene copolymer rubber and butadiene-styrene copolymer rubber.

The diene polymer rubber in which an alkali metal is bonded to the end of the diene polymer rubber is, as described above, obtained by polymerizing the diene polymer rubber with an alkali metal-based catalyst, and at least the polymer chain. It is a living polymer before the termination of polymerization, in which an alkali metal is bonded to one end.

It is possible to use a commonly used one such as an alkali metal-based catalyst, a polymerization solvent, a randomizer, a microstructure modifier for conjugated diene units, and the method for producing the polymer is not particularly limited.

Diene polymer rubbers obtained by adding an alkali metal to diene polymer rubbers include alkali metal base catalysts, alkaline earth metal base catalysts, solution polymerization using Ziegler catalysts, redox type catalysts, etc. Diene copolymer rubber obtained by polymerizing or copolymerizing the conjugated diene monomer or the conjugated diene monomer and a monomer copolymerizable therewith by a usual polymerization method such as emulsion polymerization (specifically, polybutadiene rubber, Polyisoprene rubber, butadiene-styrene copolymer rubber, butadiene-
Examples thereof include isoprene copolymer rubber, polypentadiene rubber, butadiene-piperylene copolymer rubber, and butadiene-propylene alternating copolymer rubber), but with an alkali metal added thereto.

Alkali metal addition to the diene polymer rubber may be carried out by a commonly used method. For example, a diene polymer rubber may be added to a hydrocarbon solvent in a conventional alkali metal base catalyst and an ether compound, an amine compound or a phosphine compound. The addition reaction is carried out in the presence of such a polar compound at a temperature of 30 to 100 ° C. for several tens of minutes to several ten hours. The amount of the alkali metal-based catalyst used is usually in the range of 0.1 to 10 mmol per 100 g of the diene polymer rubber. If it is less than 0.1 mmol, the impact resilience cannot be improved. Side reactions such as cutting occur and do not contribute to the improvement of impact resilience.

The polar compound is usually used for 1 mol of the alkali metal-based catalyst.
It is 0.1 to 10 mol, preferably 0.5 to 2 mol. An example of the alkali metal-based catalyst used in the polymerization and the addition reaction is as follows.

It is a complex with lithium, sodium, potassium, rubidium, cesium metal or their hydrocarbon compounds or polar compounds.

Preferred are lithium or sodium compounds having 2 to 20 carbon atoms.

For example, ethyl lithium, n-propyl lithium, iso
-Propyl lithium, n-butyl lithium, sec-butyl lithium, t-octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, 4-cyclopentyl lithium, 1,4-dilithio-butene-2, sodium naphthalene, sodium biphenyl, potassium-tetrahydrofuran complex, potassium diethoxyethane complex, sodium salt of α-methylstyrene tetramer and the like.

The polymerization reaction and the alkali metal addition reaction are carried out in a hydrocarbon solvent or a solvent that does not destroy the alkali metal-based catalyst such as tetrohydrofuran, tetrahydropyran and dioxane.

The suitable hydrocarbon solvent is selected from aliphatic hydrocarbons, aromatic hydrocarbons and alicyclic hydrocarbons, and particularly has 2 to 2 carbon atoms.
Propane having twelve, n-butane, iso-butane,
n-pentane, iso-pentane, n-hexane, cyclohexane, propene, 1-butene, iso-butene, trans-2-butene, cis-2-butene, 1-pentene,
2-Pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like are preferable. Further, these solvents can be used as a mixture of two or more kinds.

Next, the compound to be reacted with the above-mentioned alkali metal-containing diene polymer rubber used in the present invention has a general formula: (In the formula, R ₁ and R ₂ represent an alkyl group, and n represents an integer.)
Is a nitroalkyl acrylate compound represented by.

Specific examples of such nitroalkyl acrylate are shown below.

2-Methyl-2-nitropropyl acrylate, 3-Methyl-3-nitrobutyl acrylate, 4-Methyl-4-nitropentyl acrylate, 2-Ethyl-2-acrylate
Nitropropyl, 2-propyl-2-nitropropyl acrylate, 2-butyl-2-nitropropyl acrylate, 2-methyl-2-nitrobutyl acrylate, 2-ethyl-2-nitrobutyl acrylate, 2-propyl acrylate 2-Nitrobutyl and the like can be mentioned, but 2-methyl-2-nitropropyl acrylate is particularly preferred.

The amount of the nitroalkyl acrylate compound used is such that an alkali metal-based catalyst or a diene polymer rubber used in the production of a diene polymer rubber having an alkali metal bonded to the end thereof is treated with an alkali metal in a subsequent reaction. The amount is usually 0.05 to 10 mol, preferably 0.2 to 2 mol, per 1 mol of the alkali metal-based catalyst used in the addition.

Since the reaction between the nitroalkyl acrylate compound and the active conjugated diene-based polymer rubber having an alkali metal terminal or the conjugated diene-based polymer rubber to which an alkali metal is added occurs rapidly, the reaction temperature and reaction time can be selected in a wide range. However, it is generally room temperature to 100 ° C. and several seconds to several hours.

The reaction may be carried out by bringing an alkali metal-containing diene polymer rubber and the nitroalkyl acrylate compound into contact with each other. For example, the diene polymer rubber is polymerized using an alkali metal base catalyst, and the diene polymer rubber is dissolved in the polymer rubber solution. As a preferred embodiment, a method of adding a predetermined amount of the nitroalkyl acrylate compound to the above, a method of adding the nitroalkyl acrylate compound after the completion of the alkali metal addition reaction in the diene polymer rubber solution, and reacting Although it can be illustrated, it is not limited to this method.

The obtained modified diene polymer rubber has a nitroalkyl acrylate compound introduced at the molecular end or in the molecular chain.

After completion of the reaction, the modified diene polymer rubber is used as it is in the coagulation method used in the production of rubber by ordinary solution polymerization such as addition of a coagulant from the reaction solution or steam coagulation, and the coagulation temperature is not limited at all. It has not been.

The crumb separated from the reaction system can also be dried by using a band dryer, an extrusion type dryer or the like used in the usual production of synthetic rubber, and the drying temperature is not limited at all.

It is necessary that the modified modified diene polymer rubber is contained in the rubber composition in an amount of at least 10% by weight, preferably 20% by weight or more. If it is less than 10% by weight, improvement in impact resilience cannot be expected.

When the rubber is used in combination with other rubbers, the other rubbers include emulsion-polymerized styrene-butadiene copolymer rubber, polybutadiene rubber by solution polymerization (anionic polymerization catalyst, Ziegler type catalyst, etc.), styrene- Butadiene copolymer rubber. Polyisoprene rubber, butadiene-isoprene copolymer rubber, etc. and natural rubber are included. One or more of these rubbers are selected and used according to the purpose.

Mooney viscosity of the modified modified diene polymer rubber (M
L _{1 + 4} 100 ° C.) is usually in the range of 10 to 200, preferably 20 to 150.

If it is less than 10, mechanical properties such as tensile strength are inferior, and if it exceeds 200, miscibility is poor when it is used in combination with other rubber and processing operability becomes difficult, and a vulcanized product of the obtained rubber composition is obtained. It is not preferable because the mechanical properties of are deteriorated.

All or part of the rubber component used in the present invention can be used as an oil-extended rubber.

The modified rubber composition of the present invention is produced by mixing the rubber component and various compounding agents using a mixer such as a roll / Banbury machine. The various compounding agents to be used may be selected from those commonly used in the rubber industry, and those suitable for the purpose of use of the rubber composition may be selected, and are not particularly limited.

Usually, the vulcanization system is sulfur, stearic acid, zinc white, various vulcanization accelerators (thiazole series, thiuram series, sulfenamide series, etc.) or organic peroxides, and the reinforcing agent is HAF, ISAF, etc. Various grades of carbon black, silica, etc. are used, as fillers calcium carbonate, talc, etc., and as other compounding agents, process oils, processing aids, antioxidants, etc. are used. The type and amount of these compounding agents are selected according to the purpose of use of the rubber composition, and are not particularly limited in the present invention.

The modified rubber composition of the present invention has impact resilience and JIS at low temperature.
Since it has improved hardness, it is preferably used especially for automobile tires, but it can also be used as various industrial raw material rubbers for shoe soles, floor materials, anti-vibration rubbers, etc.

<Examples> The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A polymerization reactor made of stainless steel having an internal volume of 10 was washed, dried and replaced with dry nitrogen, and then 1000 g of 1,3-butadiene,
4300 g of n-hexane, 40 mmol of ethylene glycol diethyl ether and 6.6 mmol of n-butyllithium (n-hexane solution) were added, and polymerization was carried out at 50 ° C. for 1 hour while stirring.

After completion of the polymerization, 3.3 mmol of 2-methyl-2-nitropropyl acrylate was added, and the mixture was reacted for 30 minutes with stirring. Then, 10 milliliter of methanol was added and the mixture was further stirred for 5 minutes.

Then, the contents of the polymerization reactor were taken out, and 5 g of 2,6-
Di-t-butyl-p-cresol (Sumitomo Chemical Co., Ltd.
Riser BHT) and add most of the n-hexane to steam.
After emission, it was dried under reduced pressure at 60 ° C. for 24 hours.

The Mooney viscosity and 1,2 bond unit content (by infrared spectroscopy) of the resulting polymer rubber were measured.

The resulting polymer rubber had a Mooney viscosity of 67 and a vinyl content of 70%.

The resulting polymer rubber was kneaded on a roll with each compound according to the compounding recipe in Table 1 to obtain a rubber composition.
Press vulcanization was carried out under the condition of 30 ° C for 30 minutes.

The impact resilience of the vulcanized rubber was measured at 60 ° C. using a Lupkeresilien tester. JIS hardness is JIS K63
01 at -20 ° C.

The measurement results are shown in Table 2.

Comparative Example 1 A polymer and a rubber composition were obtained in the same manner as in Example 1 except that 2-methyl-2-nitropropyl acrylate was not added, and their physical properties were measured.

The polymer rubber produced has a Mooney viscosity of 13, and contains vinyl. The amount was 70%.

Comparative Example 2 A polymer and a rubber composition were obtained in the same manner as in Example 1 except that 2-methyl-2-nitropropyl acrylate was not added and that n-butyllithium was 4.2 mmol, and the physical properties were measured. It was

The produced rubber had a Mooney viscosity of 67 and a vinyl content of 70%.

Example 2 A polymerization reactor made of stainless steel with an internal volume of 10 was washed, dried, and purged with dry nitrogen.
g, 250 g of styrene, 4300 g of n-hexane, 23 g of tetrahydrofuran, 7.1 mmol of n-butyllithium (n-hexane solution) were added, and polymerization was carried out at 50 ° C. for 1 hour while stirring. After completion of the polymerization, 3.5 mmol of 2-methyl-2-nitropropyl acrylate was added, and the mixture was reacted for 30 minutes with stirring. Then, 10 milliliter of methanol was added and the mixture was further stirred for 5 minutes.

Then, the contents of the polymerization reactor were taken out, and 5 g of 2,6-
Di-t-butyl-p-cresol (Sumilyzer- BH
T) was added to evaporate most of the n-hexane,
It was dried under reduced pressure at 60 ° C. for 24 hours.

The produced polymer rubber had a Mooney viscosity of 67, a styrene content of 25% and a vinyl content of 40%.

With respect to the obtained polymer rubber, a rubber composition was obtained in the same manner as in Example 1 and its physical properties were measured.

Comparative Example 3 The procedure of Example 2 was repeated except that 2-methyl-2-nitropropyl acrylate was not added.

The produced polymer rubber had a Mooney viscosity of 18, a styrene content of 25% and a vinyl content of 40%.

Comparative Example 4 The procedure of Example 2 was repeated except that 2-methyl-2-nitropropyl acrylate was not added and that n-butyllithium was 4.4 mmol.

The produced polymer rubber had a Mooney viscosity of 67, a styrene content of 25% and a vinyl content of 40%.

Table 2 shows the results of measuring the physical properties of these examples and comparative examples.

From these results, the rubber composition for a tire tread of the present invention, the rubber composition for a tire tread containing the polymer obtained by the same method as the polymer of the present invention except that the nitroalkyl acrylate compound is not added, and the present invention It can be seen that the impact resilience is remarkably high and the JIS hardness at low temperature is remarkably low, as compared with the rubber composition for a tire tread, which contains a polymer containing no nitroalkyl acrylate compound having the same Mooney viscosity as that of the above polymer.

Example 3 and Comparative Example 5 A stainless steel polymerization reactor having an internal volume of 10 was washed and dried to give a styrene-butyldiene copolymer (Moonie viscosity 5).
1, styrene content 25%, vinyl content 40%) 500g,
4300 g of n-hexane was charged and dissolved with stirring. Then n
-Butyllithium (n-hexane solution) 6.4 mmol and tetramethylethylenediamine 6.4 mmol were added and reacted at 70 ° C for 1 hour.

Next, add 2-methyl-2-nitropropyl acrylate to 3.2
After adding millimole and reacting for 30 minutes under stirring, 1
0 milliliter of methanol was added and the mixture was further stirred for 5 minutes.

Then, the contents of the polymerization reactor were taken out, and 5 g of 2,6-
Di-t-butyl-p-cresol (Sumilyzer BH
T) was added to evaporate most of the n-hexane,
It was dried under reduced pressure at 60 ° C. for 24 hours.

Using the resulting polymer rubber, a rubber compounding composition was prepared according to the compounding recipe shown in Table 1, press-vulcanized to prepare a test piece, and physical properties were measured in the same manner as in Example 1.

The measurement results are shown in Table 2.

Further, using a styrene-butadiene copolymer before modification,
It carried out similarly and it was set as the comparative example 5.

The results are shown in Table 2.

<Effects of the Invention> As described above, according to the present invention, there is provided a modified rubber composition containing a modified diene-based copolymer rubber as a rubber component, which enhances impact resilience and reduces JIS hardness at low temperatures. You can

Claims (1)

[Claims] 1. A diene polymer rubber having an active alkali metal terminal or a conjugated diene rubber to which an alkali metal is added in a rubber composition comprising a rubber component and a compounding agent; (In the formula, R ₁ and R ₂ represent an alkyl group, and n represents an integer.)
A modified rubber composition characterized in that the rubber component contains at least 10% by weight of a modified diene polymer rubber obtained by reacting with a nitroalkyl acrylate compound.