JPH0618932B2 - Random styrene-butadiene copolymer composition - Google Patents

Description

The present invention relates to a linear component modified with a specific urea derivative and a branch modified with a polyfunctional coupling agent having at least 3 reactive sites. The present invention relates to a random styrene-butadiene copolymer composition composed of a linear component and having styrene units in the copolymer chain having a specific styrene chain distribution.

[Prior Art] Random styrene-butadiene copolymers have been widely used as rubbers for tires, but in recent years, with the demand for low fuel consumption and improved driving safety for automobiles, the tire properties have been low. There is a growing demand for excellent fuel economy and steering stability. As rubber for tires, high impact resilience is required to improve fuel economy, and high wet skid resistance is required to improve steering stability. . Further, roll processability, extrusion processability, etc., which are important in tire production, are required.

However, the relationship between impact resilience and wet skid resistance is contradictory, and various methods have been proposed to balance these contradictory properties and improve workability. For example, a method of setting a specific bimodal rubber (JP-A-57-126807), a method of blending a high molecular weight rubber having a specific glass transition temperature and a low molecular weight rubber (JP-A-57-180646), tin. And a method of introducing a specific amount of branched components bonded by a coupling agent other than tin (Japanese Patent Laid-Open No. 59-45338), and highly homogenizing styrene units in a copolymer chain having a bimodal molecular weight distribution. There is a method (Japanese Patent Application No. 59-159123). Further, as a method of improving only processability, a method of setting a branched polymer (Japanese Examined Patent Publication No. 4-4996, Japanese Examined Patent Publication No. 49-36957, Japanese Examined Patent Publication No. 59-5266).
4).

[Problems to be Solved by the Invention] However, although these methods have some improvement effects, they have not been able to satisfy these contradictory properties to a high degree and sufficiently improve workability.

The present invention has been made in view of the above points, and an object thereof is to provide a random styrene-butadiene copolymer composition in which the balance between impact resilience and wet skid resistance is remarkably improved and workability is improved. .

[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, and as a result, a specific urea was obtained. It is composed of a linear component modified with a derivative and a branched component modified with a polyfunctional coupling agent having at least three reactive sites, and the styrene unit in the copolymer chain has a specific styrene chain distribution. It was made based on the finding that the random styrene-butadiene copolymer composition having the above-mentioned composition has a remarkably excellent balance between impact resilience and wet skid resistance and excellent processability.

That is, the present invention is a lithium-terminated copolymer obtained by copolymerizing styrene and butadiene using an organic lithium compound as a polymerization initiator in a hydrocarbon solvent, and a general formula (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) Mooney viscosity (ML ₁₎ comprising a linear component obtained by reacting a urea derivative and a branched component obtained by reacting the lithium-terminated copolymer with a polyfunctional coupling agent having at least 3 reactive sites. ₊ 4,100 ℃) is 30 to 1
A styrene-butadiene copolymer composition of 50, wherein the bound styrene is 5 to 45 wt%, the styrene single chain having one styrene unit is 40 wt% or more of the bound styrene, and the styrene unit is 8 or more. The styrene long chain is 5% by weight or less of the bound styrene, and the linear component is the copolymer composition.
The present invention relates to a random styrene-butadiene copolymer composition characterized in that it is 25 to 75% by weight and the remaining branched component is 75 to 25% by weight.

The random styrene-butadiene copolymer composition of the present invention exhibits excellent vulcanizate properties and processability and is used for various rubber applications, but is also useful for tire applications such as treads and sidewalls.

The present invention will be described in detail below.

The linear component of the random styrene-butadiene copolymer composition of the present invention comprises a lithium-terminated copolymer and a general formula (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) It is important that the straight component of the composition consists of a reaction of a urea derivative having a cyclic structure with a lithium-terminated copolymer and a urea derivative having an acyclic structure, or a substance such as water, alcohol or acid. When it is composed of a reaction, the impact resilience of the composition is poor.

Further, 25 to 75% by weight of the copolymer composition is a linear component modified with a specific urea derivative, and the remaining 75 to 25% by weight is a polyfunctional compound having at least 3 reactive sites. It is a branched component modified with a coupling agent. When the linear component is less than 25% by weight or the branched component exceeds 75% by weight, the impact resilience is reduced, and when the linear component exceeds 75% by weight or the branched component is less than 25% by weight. In that case, the workability is lowered, which is not preferable.

The bound styrene content of the copolymer composition of the present invention is 5 to 45% by weight, preferably 10 to 40% by weight. 5 bound styrene
If it is less than 5% by weight, wet skid resistance is lowered, which is not preferable. On the other hand, if the bound styrene content exceeds 45% by weight, impact resilience and abrasion resistance are reduced, which is not preferable.

The styrene single chain having one styrene unit (hereinafter referred to as S ₁ ) of the copolymer composition of the present invention is 40% by weight or more, preferably 55% by weight or more of the bound styrene, and styrene in which 8 or more styrene units are connected. long chain (hereinafter S ₈ referred to as ~) is 5.0 wt% of bound styrene, preferably it must be 2.5 wt% or less. 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.

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

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

Further, as the 1,2 vinyl content is increased, the heat resistance and reversion of vulcanization are improved. H. Nordsiek (Paper Presented
to the Int. Rubber Conf., 1979).

The relationship between these 1,2 vinyl content and physical properties is already known, and in the present invention, the 1,2 vinyl content is not particularly limited, but in terms of impact resilience and abrasion resistance, the 1,2 vinyl content is 10 On the other hand, the content of 1,2 vinyl is preferably 30 to 90% from the viewpoint of wet skid resistance. 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 used, but it is good to decide according to the purpose of use.

The processability of the copolymer composition of the present invention changes greatly by changing the molecular weight distribution. It is known for processing of the relationship between the molecular weight distribution, in the present invention, the weight average molecular weight _(W) and in particular limiting the number average molecular weight _(N) and the molecular weight distribution to be displayed with a ratio _{(W / N)} No, but 1.2-3.5 considering the balance between physical properties and processability
Is preferred. Further, the weight average molecular weight ( _W ') and the number average molecular weight ( _N ') of the linear component and the branched component of the copolymer composition of the present invention ( _W '/ _N ') are also particularly limited. However, 1.1-2.5 is sufficient.

The copolymer composition of the present invention is produced by the method described below. One method is to copolymerize styrene and 1,3-butadiene with an organic lithium compound as an initiator in a hydrocarbon solvent, as disclosed in British Patent 994726, JP-A-59-140211 and JP-A-56-143209. 1,3-butadiene or 1,3-butadiene and styrene so that the content of styrene monomer in the monomer composition ratio of styrene and 1,3-butadiene in the polymerization system falls within a specific concentration range. A lithium-terminated copolymer obtained by continuously or intermittently supplying a mixture of (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) It is obtained by adding a urea derivative and a polyfunctional coupling agent having at least 3 reactive sites in a predetermined ratio.

Another method is to copolymerize styrene and 1,3-butadiene in a hydrocarbon solvent with an organolithium compound as an initiator, as described in JP-B-38-2394. Copolymerization was carried out by adding a mixture of 1,3-butadiene and the obtained lithium-terminated copolymer and the general formula (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) Urea derivative and a polyfunctional coupling agent having at least 3 reactive sites in a given ratio.

The urea derivative and the polyfunctional coupling agent used in the present invention react quantitatively almost instantaneously when they come into contact with the lithium-terminated copolymer. Therefore, in order to obtain the copolymer composition of the present invention, the urea derivative and the polyfunctional coupling agent are added in an equivalent ratio of the urea derivative and the polyfunctional coupling agent to 1 mol of the organolithium compound, respectively. 0.25 to 0.7
5, 0.75-0.25, and the total amount of each added is adjusted to an equivalent ratio of about 1, and after the copolymerization is completed, the urea derivative and the polyfunctional coupling agent are added to the polymerization system at the same time or separately. Good. Alternatively, after completion of the copolymerization, 1,3-butadiene may be added, and then the urea derivative and the polyfunctional coupling agent may be added. Alternatively, a polyfunctional coupling agent may be added during the copolymerization and a urea derivative may be added after the completion of the copolymerization.

Further, the copolymer composition of the present invention is a polyfunctional compound having a linear component obtained by reacting a lithium-terminated copolymer with a specific urea derivative, a lithium-terminated copolymer, and at least three reactive sites. The branched components obtained by reacting the organic coupling agent are separately prepared, and these copolymers are used so that the linear component is 25 to 75% by weight and the branched component is 75 to 25% by weight. It can also be obtained by mixing at a blending ratio.

The copolymer composition of the present invention, by changing the intrinsic viscosity ratio of the branched component and the linear component in the copolymer composition,
The balance between physical properties and workability changes. The relationship between the intrinsic viscosity of these branched components and the linear component and the processability is already known (Japanese Patent Publication No. 59-52664). In the present invention, the intrinsic viscosity ratio is not particularly limited. Considering the balance of physical properties, 1.5 to 5.5 is preferable.

In the present invention, in order to adjust the microstructure of the butadiene portion in the copolymer chain or the randomness in the copolymer chain of styrene and butadiene, ethers, tertiary amines, alkali metal alkoxides, etc. Polar compounds of can be 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-tert-amyl Oxide, potassium tert-butyl oxide and the like. 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 ratio of the organolithium 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
-Multifunctional organolithium compounds such as dilithio-1,2-diphenylmethane and 1,3,5-trithiobenzene. 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, and then a polyvinylaromatic compound Or a reaction product obtained by simultaneously reacting a monoorganolithium compound, a conjugated diene, and / or a monovinylaromatic compound, and a polyvinyl compound with each other (West German Patent 2003384, etc.).

The amount of these organic lithium 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 urea derivative used in the present invention has the general formula (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) Specific examples include 1,3-diethyl-2-imidazolidinone, 1,3-dimethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone, and 1-methyl-
3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-2
-Imidazolidinone, 1-methyl-3-butyl-2-imidazolidinone, 1-methyl-3- (2-methoxyethyl) -2-imidazolidinone, 1-methyl-3- (2-ethoxyethyl) -2-imidazolidinone, 1,3-di- (2-ethoxyethyl) -2-imidazolidinone, 1,3-dimethylethylenethiourea, 1,3-dimethyl-3,4,5,6-tetrahydro- Examples thereof include 2 (1H) -pyrimidinone, and 1,3-dimethyl-2-imidazolidinone is preferable.

The reaction temperature and reaction time of these urea derivative and lithium-terminated copolymer can be adjusted over a wide range, but the reaction temperature is usually 15 to 115 ° C. and the reaction time is usually 1 second to 3 hours.

As the polyfunctional coupling agent used in the present invention,
Epoxidized soybean oil, epoxidized linseed oil, epoxidized liquid polybutadiene, dimethyl terephthalate, diethyl terephthalate, dimethyl phthalate, dimethyl isophthalate, diethyl adipate, diterephthalate dichloride,
Phthalic acid dichloride, isophthalic acid dichloride, adipic acid dichloride, silicon tetrachloride, methyltrichlorosilane, hexachlorosilane, tetramethoxysilane, carbon tetrachloride, stannic chloride, methyltrichlorotin, stannic bromide, dodecyltrichlorotin, Hex
(2-Methyl-1-aziridinyl) triphosphatriazine, pyromellitic dianhydride, polyaryl polyisocyanate and the like can be mentioned. Of these, preferred are silicon tetrachloride, phthalic acid dichloride, and stannic chloride. When a copolymer composition having a branched component coupled with stannic chloride is kneaded with carbon black and process oil, the vulcanized product thereof exhibits excellent impact resilience.
On the other hand, the copolymer composition having a branched component coupled with silicon tetrachloride exhibits excellent processability, particularly excellent extrusion characteristics. Therefore, in order to obtain a copolymer composition having more excellent processability, it is preferable to use silicon tetrachloride as a coupling agent.

The polymerization method in the present invention may be either a batch polymerization method or a continuous polymerization method. The polymerization temperature is in the range of 20 to 130 ° C, and it is recommended that the polymerization is started at 30 to 87 ° C in the batch polymerization method and the temperature is elevated so that the maximum temperature reaches 90 to 125 ° C.

After completion of the prescribed reaction, an antioxidant such as 2,6-di-tert-butyl-p-cresol is added, and then the resulting polymer is subjected to usual post-treatments such as separation, washing and drying to obtain a desired co-product. A polymer composition can be obtained.

The copolymer composition 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 composition 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 used by blending with natural rubber or other synthetic rubber, at least 30% by weight or more of the raw material rubber needs to be the copolymer composition of the present invention in order to exhibit the excellent properties of the present invention. .

Further, the copolymer composition of the present invention is blended with a known compounding agent, for example, carbon black, process oil, etc., and after mixing and vulcanization, as a product, for example, tire applications such as tire tread, carcass, sidewalls, Alternatively, it can be used in applications such as extruded products, automobile window frames, industrial products, anti-vibration rubber, etc., but because it has excellent impact resilience and wet skid resistance balance and excellent processability, it is particularly fuel efficient tires. Can be used as tread rubber.

[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 composition is analyzed by the method recently developed by Tanaka et al. Specifically, the styrene chain distribution is analyzed by a gel permeation chromatogram (GPC) of a decomposition product obtained by ozone cleavage of all double bonds of the butadiene unit (Proceedings of the Polymer Society of Japan, Vol. 29, No. 9, 2055). page). The proportion of branched components in the copolymer composition is calculated by the peak area on the high molecular weight side by GPC. The proportion of the linear component of the copolymer composition is calculated from the difference between the total peak area of the copolymer composition by GPC and the peak area on the high molecular weight side. 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. The processability was judged by the Mooney viscosity of the compound or the roll wrapping property of the compound. The roll wrapping property of the blend was evaluated by the wrapping property, operability, etc. of the carbon blend using a 6 inch roll.

Examples 1 to 3 and Comparative Examples 1 to 3 In a nitrogen atmosphere, cyclohexane (6.2 kg) and tetrahydrofuran
4 g, 0.28 kg of styrene and 0.42 kg of 1,3-butadiene were charged, and while vigorously stirring the mixture in the polymerization vessel, the temperature of this mixture was adjusted to about 70 ° C., and then a predetermined amount of the mixture was added as shown in Table 1. Copolymerization was initiated by adding n-butyllithium.
When the temperature in the polymerization vessel increased and the polymerization conversion rate of the final copolymer reached about 20% by weight, the remaining 1,3-butadiene (0.30 kg) was pumped at a constant rate for 10 minutes using a metering pump. Was continuously fed to the polymerization system. The maximum polymerization temperature (about 98
C.) and the copolymerization is completed, a predetermined amount of silicon tetrachloride is added as shown in Table 1, and then a predetermined amount of 1,3-
Diethyl-2-imidazolidinone was added and reacted for about 10 minutes. To the copolymer solution thus obtained, 5 g of 2,6-di-tert-butyl-p-cresol was added as a stabilizer,
The solvent was removed by heating to obtain a copolymer composition. However, in Comparative Example 3, 1,3-diethyl-2-imidazolidinone was changed to 1 g of methanol to carry out the copolymerization. The basic properties of the copolymer composition thus obtained are shown in Table 1. The unvulcanized rubber composition obtained by kneading and mixing these copolymer compositions in a Banbury mixer according to the formulation of Table 2 was vulcanized at 145 ° C. and physical properties were evaluated. The measurement results are shown in Table-1.

Examples 4 to 7 and Comparative Examples 6 and 7 In a nitrogen atmosphere, the same polymerization vessel as that used in Example 1 was used.
As shown in Fig. 3, a predetermined amount of cyclohexane, tetrahydrofuran, styrene, 1,3-butadiene (hereinafter referred to as "first butadiene") was charged, and while vigorously stirring the mixture in the polymerization vessel, the temperature of the mixture was adjusted to a predetermined temperature. After adjusting
Copolymerization was initiated by adding a predetermined amount of n-butyllithium as shown in Table 1. Then, as shown in Table 1, the remaining 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 stannic chloride was added as shown in Table 3, and then a predetermined amount of 1,3 -Dimethyl-2-imidazolidinone was added and reacted for about 10 minutes. 5 g of 2,6-di-tert-p-cresol was added as a stabilizer to the copolymer solution thus obtained, and the solvent was removed by heating to obtain a copolymer composition. The basic properties of the copolymer composition thus obtained are shown in Table 3. These copolymer compositions were kneaded and mixed in a Banbury mixer in accordance with the formulation of Table 2 to obtain an unvulcanized rubber compound, which was vulcanized at 145 [deg.] C. for evaluation of physical properties. The measurement results are shown in Table-4.

Comparative Examples 4 and 5 In a nitrogen atmosphere, the same polymerization vessel as that used in Example 1 was used.
As shown in 3, a predetermined amount of cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged, the temperature in the polymerization vessel was adjusted to a predetermined temperature, and then a predetermined amount of n-butyllithium was added to perform copolymerization. After starting, add a predetermined amount of stannic chloride as shown in Table-3, then add a predetermined amount of 1,
3-Dimethyl-2-imidazolidinone was added and reacted for about 10 minutes. However, in Comparative Example 5, 0.065 g of potassium tert-butyl oxide (KTB) was newly added to the polymerization system. The copolymer solution thus obtained contained 2,6-di-ter as a stabilizer.
5 g of tp-cresol was added, and the solvent was removed by heating to obtain a copolymer composition. The basic properties and vulcanizate properties of the copolymer composition thus obtained are shown in Tables 3 and 4.

[Effects of the Invention] The random styrene-butadiene copolymer composition according to the present invention has an excellent balance of impact resilience, wet skid resistance and abrasion resistance, and is used for tire applications such as tire treads, carcasses, and sidewalls, or It can be used for applications such as extruded products, automobile window frames, anti-vibration rubber, and industrial products, and its industrial significance is great.

Claims (1)

[Claims] 1. A lithium-terminated copolymer obtained by copolymerizing styrene and butadiene using an organic lithium compound as a polymerization initiator in a hydrocarbon solvent; (Wherein R ₁ and R ₂ are each independently a C _{1 to} C ₄ alkyl group or an alkoxyalkyl group, Y is an oxygen atom or a sulfur atom, and n is an integer of 2 to 4) Mooney viscosity (ML ₁₎ comprising a linear component obtained by reacting a urea derivative and a branched component obtained by reacting the lithium-terminated copolymer with a polyfunctional coupling agent having at least 3 reactive sites. ₊ 4,100 ℃) is 30 to 1
A styrene-butadiene copolymer composition of 50, wherein the bound styrene is 5 to 45 wt%, the styrene single chain having one styrene unit is 40 wt% or more of the bound styrene, and the styrene unit is 8 or more. The styrene long chain is 5% by weight or less of the bound styrene, and the linear component is the copolymer composition.
A random styrene-butadiene copolymer composition, characterized in that it is 25 to 75% by weight, and the remaining branched component is 75 to 25% by weight.