JPH0643449B2 - Method for producing new random styrene-butadiene copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel random styrene-butadiene copolymer having styrene units in the copolymer chain modified with a specific amide compound having a specific styrene chain distribution. The present invention relates to a method for manufacturing a united body.

[Prior Art] Random styrene-butadiene copolymers have been widely used as rubber for tires in recent years, but in recent years, due to social demands for resource saving and energy saving, there is a demand for low fuel consumption of automobiles and safety during traveling. With the demand for improvement, tire characteristics are required to have excellent fuel economy, steering stability, and durability.
Rubber for tires is required to have high impact resilience to improve fuel economy, high wet skid resistance to improve steering stability, and excellent wear resistance to improve durability.

However, the relationship between impact resilience and wet skid resistance is contradictory, and the relationship between abrasion resistance and wet skid resistance is also contradictory, and in order to balance these contradictory characteristics, A method has been proposed. For example, by introducing a functional group into a diene polymer, a method of improving impact resilience without impairing wet skid resistance (JP-A-58-162604, JP-A-6-162604).
No. 0-137913). Further, a method of improving impact resilience, wet skid resistance and abrasion resistance by controlling the distribution of styrene in the styrene-butadiene copolymer chain has been proposed. For example, a method of greatly increasing the styrene distribution width at the terminal end in the copolymer chain (Japanese Patent Laid-Open No. 56-1).
43209), a method of blocking two kinds of copolymers having different styrene contents in the same copolymer (JP-A-57-16544).
5, JP-A-57-200413), and a method of highly homogenizing styrene units in a copolymer chain (JP-A-57-100112).

[Problems to be Solved by the Invention] However, although these copolymers have some improvement effects, they have not reached a high level of impact resilience, wet skid resistance and abrasion resistance.

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for producing a random styrene-butadiene copolymer having a highly improved balance of impact resilience, wet skid resistance and abrasion resistance. .

[Means and Actions for Solving Problems] The present invention has conducted a thorough study on the chain distribution of styrene units in a styrene-butadiene copolymer chain in which a functional group is bonded to the copolymer chain. A random styrene-butadiene copolymer modified with a specific amide compound having a specific styrene chain distribution in which the styrene unit in the united chain has a highly excellent balance of impact resilience, wet skid resistance and abrasion resistance. It was made based on the finding of.

That is, the present invention, in the presence of a polar compound in a hydrocarbon solvent, when copolymerizing styrene and 1,3-butadiene with an organic lithium compound as a polymerization initiator, the total amount of styrene and a part of 1,3-butadiene are used. Start the copolymerization of
The styrene polymerization conversion rate is 98 after or after the start of the polymerization.
While the content of styrene monomer in the polymerization system monomer is up to 2% by weight of the finally obtained amount of bound styrene (% by weight of bound styrene in the copolymer), A lithium-terminated copolymer obtained by copolymerization by adding 3-butadiene continuously or intermittently, and a general formula (In the formula, R ₁ is a C ₁ -C ₆ alkyl group, a cycloalkyl group or an alkoxyalkyl group, Y is an oxygen atom, and n is 3
Represents an integer of 4) or an amide compound represented by In one or more hydrogen atoms of the polymethylene chain C ₁ ~ shown
A Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 30 to 30 is characterized by reacting an amide compound substituted with an alkyl group of C _6.
150, 5-45% by weight of bound styrene, 1 styrene unit
The present invention relates to a method for producing a random styrene-butadiene copolymer in which 40% by weight of styrene single chains is 40% by weight or more of bound styrene, and 8% or more of styrene units are 5% by weight or less of bound styrene. Is.

The styrene-butadiene copolymer obtained by the method of the present invention exhibits excellent properties and is used for various rubber applications, and is particularly useful as a rubber for tire red.

The present invention will be described in detail below.

The amide compound used in the present invention has a specific hydrocarbon group bonded to the nitrogen atom, and a nitrogen atom and a carbon atom. A general formula linked by a polymethylene chain represented by (Wherein R ₁ represents a C ₁ -C ₆ alkyl group, a cycloalkyl group or an alkoxyalkyl group, Y represents an oxygen atom or a sulfur atom, and n represents an integer of 3 to 4). It is necessary to have. This has a very important meaning in achieving the present invention. Usually, in a stoichiometric reaction between an amide compound having an acyclic structure and a lithium-terminated polymer, the bond between the carbonyl group and the amino group is cleaved as described in JP-B-42-24174, resulting in a copolymer. It is not possible to effectively introduce amino groups into. Further, when this reaction product is hydrolyzed, it becomes a secondary amine that deactivates the catalyst, so this reaction is not preferable in practice.

The above reaction is shown below, where p represents the polymer chain.

On the other hand, in a hydrocarbon solvent, a secondary amine is liberated by a stoichiometric reaction between the amide compound having a 5-membered ring or 6-membered ring structure used in the present invention and the lithium-terminated copolymer. It is possible to reliably introduce a functional group such as an amino group into the copolymer. When the copolymer thus obtained is blended with a compounding agent such as carbon black or process oil, mixed and kneaded, and vulcanized, the vulcanized product exhibits excellent impact resilience and abrasion resistance.

The bound styrene of the copolymer obtained by the method of the present invention is 5 to 45% by weight, preferably 10 to 40% by weight. If the bound styrene content is less than 5% by weight, wet skid resistance is lowered, which is not preferable. On the other hand, bound styrene is 45% by weight
If it exceeds the range, impact resilience and wear resistance decrease, which is not preferable.

The styrene single chain having one styrene unit (hereinafter referred to as S ₁ ) of the copolymer obtained by the method of the present invention is 40% by weight or more, preferably 55% by weight or more, and 8 or more styrene units of bound styrene. Continuous styrene chain (hereinafter S ₈ ~
Is called) 5.0% by weight or less of the bound styrene, preferably
Must be less than 2.5% by weight. Even if S ₁ is less than 40% by weight of the bound styrene or S ₈ is more than 5% by weight, impact resilience, abrasion resistance and wet skid resistance are lowered, which is not preferable.

Mooney viscosity of the copolymer obtained by the method of the present invention
(ML _{1 + 4} , 100 ° C.) is 30 to 150, preferably 50 to 120.
If the Mooney viscosity is less than 30, the effects of improving impact resilience and wear resistance are not sufficient. When the Mooney viscosity exceeds 150, problems remain in the calendering processability and extrusion processability of the compound.

The physical properties of the copolymer obtained by the method of the present invention are significantly changed by changing the microstructure of the butadiene portion, and the physical properties are also greatly changed by the distribution of styrene composition in the copolymer chain.

Regarding the relationship between the microstructure and physical properties of the butadiene part,
2 The relationship between vinyl content and physical properties is known. For example, 1,2
Increasing vinyl content improves the wet skid resistance of the polymer and reduces its wear resistance (Rubber Age
ber Age), Vol 104, 55 (1972)].

In addition, as the 1,2 vinyl content increases, the heat resistance and reversion of vulcanization are improved. KH Nordsiek "Paper Presented to the Int.
f., 1979).

The relationship between the 1,2 vinyl content and the physical properties is already known, and the 1,2 vinyl content is not particularly limited in the present invention, but the 1,2 vinyl content is 10 in terms of impact resilience and abrasion resistance. -30% by weight, while the content of 1,2 vinyl is 30-90% by weight in terms of wet skid resistance.
Is desirable. In any case, it is good to determine the 1,2 vinyl content according to the purpose of use.

Regarding the 1,2 vinyl distribution in the polymer chain,
It may be uniform in the polymer chain, may gradually change along the polymer chain as shown in JP-B-48-875, or may be distributed in blocks. Well (USP-3301840), basically it should be decided according to the purpose of use.

Regarding the styrene composition distribution in the styrene-butadiene copolymer chain, it may be evenly distributed in the copolymer chain, or it may be unevenly distributed in the copolymer chain (Japanese Patent Application No. 60-410).
No. 8) may be required, and in short, it may be decided depending on the purpose of use.

The processability of the copolymer obtained by the method of the present invention is significantly changed by changing the molecular weight distribution. The relationship between the molecular weight distribution and the processability is well known, and in the present invention, the molecular weight distribution ( _W / _W ) displayed with the ratio of the weight average molecular weight ( _W ) and the number average molecular weight ( _N ) is shown.
_N ) is not particularly limited, but is preferably 1.2 to 3.5 in consideration of the balance between physical properties and processability. The shape of the molecular weight distribution may be monomodal or polymodal of bimodal or more.

The method for producing the copolymer of the present invention, in the presence of a polar compound in a hydrocarbon solvent, when copolymerizing styrene and 1,3-butadiene with an organolithium compound as a polymerization initiator,
The copolymerization of the total amount of styrene and a part of 1,3-butadiene is started, and the concentration of styrene monomer in the polymerization-type monomer until the polymerization conversion rate of styrene reaches 98% by weight after or during the start of the polymerization. Is copolymerized by continuously or intermittently adding the remaining 1,3-butadiene so that the amount of bound styrene becomes equal to or less than twice the amount of bound styrene finally obtained (wt% of bound styrene in the copolymer). The lithium-terminated copolymer obtained and the general formula (In the formula, R ₁ is a C ₁ -C ₆ alkyl group, a cycloalkyl group or an alkoxyalkyl group, Y is an oxygen atom, and n is 3
Represents an integer of 4) or an amide compound represented by In one or more hydrogen atoms of the polymethylene chain C ₁ ~ shown
Reacted with an amide compound substituted with an alkyl group of C ₆ ,
It is a method for obtaining the styrene-butadiene copolymer of the present invention by adding alcohol, water and the like to the reaction system after completion of the reaction.

In the present invention, ethers, tertiary amines, alkaline metal alkoxides, etc. are used in order to adjust the microstructure of the butadiene part in the copolymer chain or the randomness in the copolymer chain of styrene and butadiene. The polar compound of is used. For example, diethyl ether, ethylene glycol
Dimethyl ether, ethylene glycol di-n-butyl ether, ethylene glycol n-butyl-tert-butyl ether, ethylene glycol di-tert-butyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran, α-methoxymethyltetrahydrofuran, dioxane , 1,2-dimethoxybenzene, triethylamine, N,
N, N ', N'-tetramethylethylenediamine, potassium-
Examples thereof include tert-aluminum oxide and potassium-tert-butyl oxide. These compounds are used alone or as a mixture of two or more kinds.

The addition amount of the polar compound used in the present invention is 0 to 200 mol per 1 mol of the organolithium metal compound.

Examples of the organolithium compound used in the present invention include n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, monoorganolithium compounds such as tert-butyllithium, dilithiomethane, 1,4-dilithiobutane, 1 , 4-Dilithio-2-ethylcyclohexane, 1,2
And polyfunctional organolithium compounds such as -dilithio-1,2-diphenylmethane and 1,3,5-trilithiobenzene. These are used alone or in a mixture of two or more. Further, as the polyfunctional organolithium compound used in the present invention, a compound which can be substantially a polyfunctional organolithium compound by reacting the above monoorganolithium compound with another compound is also used. For example, a reaction product of a monoorganolithium compound and a polyvinylaromatic compound (Japanese Patent Publication No. 55-6652), a monoorganolithium compound and a conjugated diene, and / or a monovinylaromatic compound are reacted with each other, and then the polyvinylaromatic compound is reacted. Or a reaction product obtained by simultaneously reacting a monoorganolithium compound, a conjugated diene, and / or a monovinylaromatic compound, and a polyvinyl compound (West German Patent 2003384, etc.).

The amount of these organolithium compounds used is usually 0.1 to 10 mmol per 100 g of the conjugated diene monomer.

As the hydrocarbon solvent used in the present invention, aliphatic, alicyclic and aromatic hydrocarbons can be used. For example, hydrocarbon solvents are propane, isobutane, n-
Hexane, isooctane, cyclopentane, cyclohexane, benzene, toluene and the like, and particularly preferable solvents are n-hexane, cyclohexane and benzene. These may be used alone or as a mixture of two or more.

The amide compound used in the present invention has the general formula (In the formula, R ₁ is a C ₁ -C ₆ alkyl group, a cycloalkyl group or an alkoxyalkyl group, Y is an oxygen atom, and n is 3
Represents an integer of 4) or a compound represented by the general formula In one or more hydrogen atoms of the polymethylene chain C ₁ ~ shown
An amide compound substituted with an alkyl group of C ₆ , as specific examples, 1-cyclohexyl-2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, 1-propyl
-2-pyrrolidone, 1-butyl-2-pyrrolidone, 1-isopropyl-2-pyrrolidone, 1,5-dimethyl-2-pyrrolidone, 1-methoxymethyl-2-pyrrolidone, 1-methyl-2-piperidone, 1,
4-dimethyl-2-piperidone, 1-ethyl-2-piperidone, 1-
Examples include isopropyl-2-piperidone, 1-isopropyl-5,5-dimethyl-2-piperidone, 1-methyl-2-pyrrolidone and 1-methyl-2-piperidone are preferable, and 1-methyl-
2-Pyrrolidone is particularly preferred.

The amount of the amide compound used in the present invention is usually 0.2 to 2.0 mol, based on 1 mol of the organolithium compound,
It is preferably 0.5 to 1.5 mol, and particularly preferably 1.0 mol. Since the reaction between the lithium-terminated copolymer and the amide compound occurs immediately after they come into contact with each other, the reaction temperature and reaction time can be adjusted over a wide range, but usually the reaction temperature is 25 to 115 ° C. and the reaction time is 1 second to 3 hours. It is within the range. The addition method of these amide compounds is not particularly limited, a method of adding an amide compound after completion of the copolymerization, or a method of adding 1,3-butadiene after completion of the copolymer, and then adding an amide compound, Alternatively, there is a method of adding an amide compound in an amount such that the copolymerization is not stopped during the copolymerization. In short, the method of adding the amide compound may be determined according to the purpose of use.

The polymerization temperature is preferably 20 to 130 ° C.

After completion of the predetermined reaction, after adding an antioxidant such as 2,6-di-tert-butyl-p-cresol, the resulting copolymer is separated,
The desired copolymer can be obtained by performing usual post-treatments such as washing and drying.

The copolymer obtained by the method of the present invention may be used as an oil-extended rubber by mixing it with a process oil in a solution state, removing the solvent after mixing.

The copolymer obtained by the method of the present invention can be used alone or blended with natural rubber or other synthetic rubber such as polybutadiene, polyisoprene, emulsion-polymerized styrene-butadiene copolymer and the like. When blending with natural rubber or other synthetic rubber,
In order to exhibit the excellent properties of the present invention, it is necessary that at least 30% by weight or more of the raw rubber is a copolymer obtained by the method of the present invention.

Further, the copolymer obtained by the method of the present invention is blended with a known compounding agent such as carbon black or process oil, mixed and vulcanized, and then the product, for example, a tire such as a tire tread, a carcass or a sidewall. It can be used for applications, extruded products, automobile window frames, industrial products, anti-vibration rubber, etc., but because it has excellent impact resilience and wet skid resistance balance, it is especially suitable as a fuel-efficient tire red. Can be used.

[Examples] The present invention is described below with reference to examples, but these examples do not limit the present invention. The various properties were measured by the following methods.

The styrene chain distribution of the random styrene-butadiene copolymer is analyzed by the method recently developed by Tanaka et al. Specifically, the styrene chain distribution is analyzed by gel permeation chromatograph (GPC) of a decomposition product obtained by ozone cleavage of all the double bonds of the butadiene unit. page). The Mooney viscosity was measured at 100 ° C. using an L rotor by a usual method. The bound styrene was calculated from the absorption based on the phenyl group at 262 nm by the ultraviolet absorption spectrum method. The microstructure of the butadiene part was calculated by the Hampton method using an infrared spectrophotometer. The impact resilience was measured using a Dunlop trypsometer at a test temperature of 70 ° C. Abrasion resistance was measured using a pico abrasion tester. Wet skid resistance was measured with a device manufactured by the British Road Research Institute.

Examples 1 to 6 and Comparative Examples 1, 2, 5 and 6 In a nitrogen atmosphere, a polymerization vessel with a stirrer made of stainless steel and having an internal volume of about 10 was provided with predetermined amounts of cyclohexane, styrene and 1,3 as shown in Table 1. -Butadiene (hereinafter referred to as "first butadiene") and a Lewis base are charged in a polymerization vessel while vigorously stirring the mixture, and the mixture is adjusted to a predetermined temperature, and then a predetermined amount of n-butyllithium is added to the mixture. Polymerization started. Then, as shown in Table 1, 1,3-butadiene (hereinafter referred to as second butadiene) was continuously supplied to the polymerization system at a constant rate by a metering pump. After the supply of the second butadiene was completed, the polymerization temperature reached the maximum temperature and the copolymerization was completed, a predetermined amount of the amide compound was added as shown in Table 1 and the reaction was carried out for about 10 minutes. As a stabilizer in the copolymer solution thus obtained, 2,6-di-tert-butyl
5 g of -p-cresol was added and the solvent was removed by heating to obtain a copolymer. However, in Comparative Example 6, the amide compound was changed to 1 g of methanol to carry out the copolymerization. Table 3 shows the basic properties of the copolymer thus obtained. The unvulcanized rubber composition obtained by kneading and mixing these copolymers in a small pressure kneader according to the formulation of Table 2 was 145 ° C.
Was vulcanized and the physical properties were evaluated. The measurement results are shown in Table-3.

Comparative Examples 3 and 4 In a nitrogen atmosphere, the same polymerization vessel as that used in Example 1 was used.
As shown in 1, a predetermined amount of cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged, the mixture in the polymerization vessel was vigorously stirred, and the temperature of the mixture was adjusted to a predetermined temperature. -Butyllithium was added to start the copolymer. After the polymerization temperature reached the maximum temperature and the copolymerization was completed, a predetermined amide compound was added as shown in Table 1 and reacted for about 10 minutes. However, in Comparative Example 4, potassium-tert-butyl oxide (KTB) 0.059 was newly added.
g was added to the polymerization system. From the copolymer solution thus obtained, a copolymer was obtained in the same manner as in Example 1. From the copolymer solution thus obtained, a copolymer was obtained in the same manner as in Example 1. Table 3 shows the basic properties and vulcanizate properties of the copolymer thus obtained.

As can be seen from Table-3, Examples 1 to 6 have an excellent balance of impact resilience, wet skid resistance and wear resistance.

[Effect of the Invention] The styrene-butadiene copolymer according to the present invention is obtained by reacting a specific amide compound with the copolymer having a lithium atom bonded to the end of the copolymer chain, and Since the styrene unit in the copolymer chain has a specific styrene chain distribution, this copolymer has an excellent balance of impact resilience, wet skid resistance and abrasion resistance, and is suitable for tire treads, carcasses, sidewalls, etc. Tire applications, extruded products, automobile window frames, anti-vibration rubber,
It can be used for applications such as industrial goods, and its industrial significance is great.

Claims (1)

[Claims] 1. Styrene and 1,3 with an organic lithium compound as a polymerization initiator in a hydrocarbon solvent in the presence of a polar compound.
-When copolymerizing butadiene, the copolymerization of the total amount of styrene and a part of 1,3-butadiene is started, and after the start of polymerization or during the polymerization until the conversion of styrene reaches 98% by weight, The remaining 1,3-butadiene is continuously or intermittently adjusted so that the concentration of the styrene monomer in the polymerization-type monomer is not more than twice the amount of the finally obtained bound styrene (% by weight of bound styrene in the copolymer). Added to
Lithium-terminated copolymer obtained by copolymerization, and a general formula (In the formula, R ₁ is a C ₁ -C ₆ alkyl group, a cycloalkyl group or an alkoxyalkyl group, Y is an oxygen atom, and n is 3
Represents an integer of 4) or an amide compound represented by In one or more hydrogen atoms of the polymethylene chain C ₁ ~ shown
A Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 30 to 30 is characterized by reacting an amide compound substituted with an alkyl group of C _6.
150, 5-45% by weight of bound styrene, 1 styrene unit
A method for producing a random styrene-butadiene copolymer, wherein each styrene single chain is 40% by weight or more of the bound styrene, and the styrene long chain in which 8 or more styrene units are linked is 5% by weight or less of the bound styrene.