JPH0791323B2 - Novel random styrene-butadiene copolymer and composition thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a specific functional group having a specific styrene chain distribution of styrene units in the copolymer chain and a specific styrene composition distribution. The present invention relates to a random styrene-butadiene copolymer modified with a binding organic compound, and a composition thereof.

[Prior Art] Conventionally, random styrene-butadiene copolymers have been widely used as rubbers for tires, but in recent years, there have been demands for low fuel consumption, improvement in running safety, and further improvement in durability for automobile tires. With the demand, tire rubbers are required to have high impact resilience to reduce fuel consumption, high wet skid resistance to improve running safety, and excellent abrasion resistance to improve durability.

However, since the relationship between impact resilience and wet skid resistance and the relationship between abrasion resistance and wet skid resistance are contradictory properties, respectively, conventionally, in order to balance these contradictory properties, a blend composition of different rubbers is used. Things have been used. For example, it is a blend composition of styrene-butadiene copolymer rubber and polybutadiene. However, these blend compositions have not yet reached a high level of impact resilience, wet skid resistance, and abrasion resistance.

Recently, various methods have been proposed which are intended to improve impact resilience, wet skid resistance and abrasion resistance by controlling the distribution of styrene in the styrene-butadiene copolymer chain.

For example, a method of greatly increasing the styrene concentration at the terminal end in the copolymer chain (JP-A-56-143209) and a method of highly homogenizing styrene units in the copolymer chain (JP-A-57-1001).
12, JP-A-57-179212 and JP-A-59-140211), a method for blocking two kinds of copolymers having different styrene contents in the same copolymer chain (JP-A-57-165445). , JP Sho
57-200413), and a method of specifying the styrene reaction composition distribution width and the glass transition temperature peak temperature width in the copolymer (JP-A-58-154711).

[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 provides a novel random styrene-butadiene copolymer having a significantly improved balance of impact resilience, wet skid resistance, and abrasion resistance, and a composition thereof. With the goal.

[Means and Actions for Solving Problems] In the present invention, the styrene chain distribution and the styrene composition distribution of styrene units in the styrene-butadiene copolymer chain in which a functional group is bonded to the copolymer chain have been intensively studied. As a result, a random styrene-butadiene copolymer modified with an organic compound having a specific functional group, in which the styrene unit in the copolymer chain has a specific styrene chain distribution and a specific styrene composition distribution, has a high impact resilience. It was made by discovering that the balance between the wet skid resistance and the wear resistance is remarkably excellent and the tensile strength is good.

Hereinafter, the present invention will be described in detail.

The temperature difference between the inflection points in the glass transition temperature region of the random styrene-butadiene copolymer containing a specific functional group of the present invention (hereinafter referred to as ΔT) is 15 ° C. or higher, preferably 25 ° C. or higher, and particularly preferably Is 30 ° C to 70 ° C. When ΔT is less than 15 ° C, the width of styrene composition distribution in the copolymer chain is small, and wet skid resistance and abrasion resistance are not sufficiently improved.
On the other hand, when ΔT is 15 ° C. or higher, the larger ΔT is, the wider the distribution range of styrene composition in the copolymer chain is, the more excellent the property is, and the better the blending property with other rubber is.
When T becomes extremely large over 100 ° C, the number of styrene single chains decreases, and the impact resilience and tensile strength decrease, which is not preferable. As described above, the copolymer of the present invention needs to satisfy a specific styrene chain distribution and ΔT of 15 ° C or higher. The temperature difference (ΔT) between the inflection points in the glass transition temperature range here means the first change point near the glass transition temperature in the endothermic curve obtained by measurement using a differential scanning calorimeter (DSC). It is the temperature range up to the final change point. The DSC measurement was carried out by the method shown in ASTM-D3418-82.

FIG. 1 shows endothermic curves by DSC of the styrene-butadiene copolymers obtained in Examples and Comparative Examples. First
As shown in the figure, (A) and (B) of the embodiment of the present invention are ΔT
Is large and has excellent characteristics.

Further, in the present invention, a copolymer containing a copolymer having two or more glass transition temperatures, for example, two copolymers having different styrene contents in the same copolymer chain as a block as in (c) is present as a block copolymer. The coalescence has two glass transition temperatures, a large ΔT, and favorable characteristics.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the copolymer of the present invention is 10
˜150, preferably 30˜100. When the Mooney viscosity is less than 10, the effects of improving impact resilience, wear resistance and tensile strength are not sufficient.

When the Mooney viscosity exceeds 150, problems remain in the processability such as calendering processability and extrusion processability of the compound.

The ratio w / n of the weight average molecular weight (w) to the number average molecular weight (n) of the copolymer of the present invention is 1.1 to 3.0, preferably 1.3 to 2.5. When w / n exceeds 3.0, workability is improved but impact resilience and wear resistance are reduced, which is not preferable. If it is less than 1.1, the workability is deteriorated, which is not preferable.

The bound styrene of the copolymer of the present invention is 10% to 45% by weight.
And preferably 15 to 40% by weight. If the bound styrene content is less than 10% by weight, wet skid resistance and tensile strength are deteriorated, which is not preferable. On the other hand, bound styrene
If it exceeds 45% by weight, impact resilience and wear resistance decrease, which is not preferable.

The styrene single chain having one styrene unit of the copolymer of the present invention (hereinafter referred to as S ₁ ) is 65% by weight or more of the bound styrene,
It is preferably at least 75% by weight and has 8 styrene units.
FOB continuous styrene length 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 65% by weight of the total bound styrene and S ₈ is more than 5.0% by weight, impact resilience, abrasion resistance, wet skid resistance and tensile strength are unfavorably lowered.

The copolymer of the present invention is i) And a compound having at least one N—R ₁ group (wherein Y represents an oxygen atom or a sulfur atom, R ₁ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group or an aryl group). Ii) Isocyanates represented by the general formula R ₃ -(-N = C = Y) _n (wherein Y represents an oxygen atom or a sulfur atom, R ₃
Is aliphatic, cycloaliphatic, aromatic, or having 2 to 20 carbon atoms
Represents a hydrocarbon group, and n represents an integer of 1,2,3) iii) An organometallic compound represented by the general formula (R ₄ ) _3- MX (wherein R ₄ has 1 to 20 carbon atoms). Represents an alkyl group, an alkoxyalkyl group, an aryl group, M represents a metal atom of Group IVb of the periodic table, and X represents a halogen atom), and is modified with at least one organic compound selected from the group It is a random styrene-butadiene copolymer, and the copolymer thus obtained is compounded with a compounding agent such as carbon black or process oil, kneaded, and flowed, and the flowed product has excellent impact resilience and wetness. It shows a balance between skid resistance and wear resistance, and also has excellent tensile strength.

Further, a method of reacting a lithium terminal polymer with an isocyanate compound (Japanese Patent Publication No. Sho 42-24174) is known,
It is a completely new finding that the targeted performance of the present invention can be obtained by using the limited styrene-butadiene copolymer as in the present invention, and it cannot be easily inferred from the above known facts. Further, in JP-A-58-189203, a polymer rubber composition formed by the reaction of a lithium-terminated polymer and a benzophenone derivative is disclosed, and in JP-A-61-42552, a polymer rubber composition formed by a reaction of a lithium-terminated polymer and an amide compound. Compositions, and USP-384503, disclose polymeric compositions comprising the reaction of a lithium-terminated polymer with an organometallic compound. However, the composition has not yet achieved a high level of balance between impact resilience, wet skid resistance, wear resistance and tensile strength, which are the objectives of the present invention.

The vinyl bond content of the butadiene portion of the copolymer of the present invention is not particularly limited, but is preferably 16% to 48%, particularly preferably 16% or more and less than 35%.
When the vinyl bond content is less than 16%, the abrasion resistance is improved, but the wet skid resistance is lowered, which is not preferable.

On the other hand, if the vinyl bond content exceeds 48%, the impact resilience, abrasion resistance and tensile strength decrease, which is not preferable.

Regarding the distribution of 1,2-vinyl groups in the copolymer chain, even if it is uniform in the polymer chain,
As shown in U.S. Pat. No. 875, it may be gradually changed along the polymer chain, or may be distributed in blocks (USP-3301840), that is, it may be determined depending on the purpose of use.

The copolymer of the present invention is produced by the method described below. One method is that when styrene and butadiene are copolymerized with an organolithium compound in a hydrocarbon solvent containing at least one Lewis base, the styrene monomer content in the monomer composition ratio in the polymerization system is a specific concentration. Butadiene is continuously supplied to the polymerization system under specific conditions so that it falls within the range,
After completion of the copolymerization, at least one organic compound having a specific functional group is then added to obtain a modified random styrene-butadiene.

Another method is to use a polymerization system as described in JP-A-59-140211 when copolymerizing styrene and butadiene with an organic lithium compound in a hydrocarbon solvent containing at least one Lewis base. Butadiene is continuously fed so that the styrene monomer content in the inside monomer composition ratio falls within a specific concentration range to obtain a copolymer block having a certain monomer composition ratio. A copolymer block or a butadiene polymer having a monomer composition ratio different from that of the polymer is obtained, and then at least one organic compound having a specific functional group is added, and the same copolymer chain has a different monomer composition ratio. A method for obtaining a modified random styrene-butadiene copolymer having two types of random copolymer blocks.

The organolithium compound used as the polymerization initiator of the random styrene-butadiene copolymer of the present invention,
monoorganolithium compounds such as n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, dilithiomethane,
1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,2-dilithio-1,2-diphenylmethane,
Polyfunctional organolithium compounds such as 1,3,5-trilithiobenzene and the like, which are used alone or as a mixture of two or more kinds.

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 polyvinyl aromatic compound (Japanese Patent Publication No. 55-6652), a reaction product of a monoorganolithium compound and a conjugated diene, and / or a monovinylaromatic compound, or a monoreaction product. A reaction product (West German Patent 2003384) or the like obtained by simultaneously reacting an organolithium compound, a conjugated diene, and / or a monovinyl aromatic compound, and a polyvinyl compound.

Aliphatic, alicyclic, and aromatic hydrocarbons can be used as the hydrocarbon solvent used in the present invention. For example, as the hydrocarbon solvent, 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.

As the Lewis base used in the present invention, diethyl ether, ethylene glycol dimethyl ether,
Ethylene glycol di-n-butyl ether, ethylene glycol n-butyl tert-butyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetrahydrofuran,
α-methoxymethyltetrahydrofuran, dioxane,
1,2-dimethoxybenzene, triethylamine, N, N,
Examples thereof include N ', N'-tetramethylethylenediamine and potassium-tert-amyl oxide. These compounds are used alone or as a mixture of two or more kinds.

An organic compound having a specific functional group used in the present invention, And a compound having at least one N—R ₁ group (wherein Y represents an oxygen atom or a sulfur atom, R ₁ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group or an aryl group). Represents 4,4'-bis (dimethylamino) benzophenone, 4,4'-bis (dimethylamino) thiobenzophenone, 1,3-dimethyl-
2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-dipropyl-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, N, N'-diethylpropyleneurea, N
- methyl -N'- ethyl propylene urea, 1,3-dimethyl-3,4,5,6-tetrahydro--2 ₍₁ H) - pyrimidinone, N- methyl acridone, tetramethylurea, tetramethyl thiourea, N, N-diphenylacetamide,
N, N-dimethylbenzamide, N, N-dimethylacetamide, 1,1,3,3-tetrabutylurea, N, N'-carbonyldiimidazole, N-methyl-2-pyrrolidone, N-methyl-ε-caprolactam , Succinimide, N-methylsuccinimide, methyl carbamate and the like.

In addition, isocyanates represented by the general formula R ₃ -(-N = C = Y) _n (wherein Y represents an oxygen atom or a sulfur atom,
R ₃ is aliphatic, cycloaliphatic, aromatic, or has 2 to 2 carbon atoms
Represents 20 hydrocarbon groups, and n represents an integer of 1,2,3) as methyl isocyanate, ethyl isocyanate, n-butyl isocyanate, phenyl isocyanate, 1-naphthyl isocyanate, and isothiocyanate. Methyl acid, ethyl isothiocyanate, isothiocyanic acid-i
-Butyl, isothiocyanate-n-butyl, isothiocyanate-tert-butyl, isothiocyanate allyl, phenyl isothiocyanate, benzyl isothiocyanate, isothiocyanate-p-tolyl, diphenyl ether-4,
4'-diisocyanate, lysine diisocyanate, 4,
4'-diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, toluene diisocyanate, benzene -1,2,4-triisocyanate and the like can be mentioned.

Moreover, the general formula (R ₄₎ 3 organometallic compound represented by _-M-X (wherein R ₄ is alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group, an aryl group, M is the Periodic Table IV Group b
Represents a metal atom and X represents a halogen atom), trimethylchlorosilane, triphenylchlorosilane, triethoxychlorosilane, triethylgermanium chloride, triphenylgermanium chloride, trimethyltin chloride, triethyltin chloride, tri-n -Butyltin chloride, tri-n-butyltin bromide, tripropyltin chloride, butyldimethyltin iodide, di-n-butylvinyltin bromide, trimethoxy-n-butyltin chloride, n-butyldicyclohexyltin bromide, triphenyltin chloride, Examples thereof include diethylphenyltin bromide, tri-n-butyllead chloride, triphenyllead chloride and the like.

The amount of the organic compound having a specific functional group used in the present invention is usually 0.25 mol to 2.0 mol, preferably 0.4 mol to 1.5 mol, per 1 mol of the organic alkali metal compound.
It is mol, and particularly preferably 1.0 mol.

In the present invention, 25% by weight or more, preferably 40% by weight or more of all polymer molecules must be modified with an organic compound having a specific functional group.

Further, the copolymer modified with a functional group used in the present invention may have a part thereof having a branched structure. Such a branched structure improves the low temperature flow of the polymer,
Introduced to improve workability. In order to have a branched structure, a method of copolymerizing a small amount of a difunctional or higher functional monomer, for example, divinylbenzene, or a part of the active terminal having trifunctional or higher functional activity such as silicon tetrachloride or tin tetrachloride. A method of reacting with a halogen compound, a polyepoxy compound, polyester or the like is adopted. It is desirable to introduce these branched structures within a range that does not lose the characteristics of the modified copolymer.

The method of adding the organic compound having these specific functional groups is not particularly limited, but the following method is preferable in the copolymerization of styrene and butadiene.

For example, one method is a method of adding an organic compound after completion of the copolymerization, or a method of adding an organic compound and then a coupling agent, or a method of adding a coupling agent and then an organic compound. , Or butadiene, and then an organic compound. Another method is to add an organic compound in an amount that does not stop the copolymerization reaction during the copolymerization of styrene and butadiene, and then add a coupling agent after completion of the copolymerization, or add an organic compound, Then, an organic lithium compound is added.

In short, the method of adding the organic compound containing a specific functional group may be determined according to the purpose of use.

The polymerization method in the present invention may be either a batch polymerization method or a continuous polymerization method.

The polymerization temperature in the present invention is in the range of 20 to 130 ° C. In the batch polymerization method, it is recommended to start the polymerization at 36 to 87 ° C, and to perform the polymerization at an elevated temperature 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 the desired weight. You can get coalesced.

The copolymer of the present invention is mixed with a process oil in a solution state,
After mixing, the solvent may be removed and used as an oil-extended rubber.

The copolymer of the present invention is used alone or in a blend with another synthetic rubber or natural rubber, and as a raw material rubber for various rubber applications, 5 to 60 parts by weight of process oil is added to 100 parts by weight of the raw material rubber
30 to 100 parts by weight of carbon black can be blended and used. In this case, at least 30% by weight of the raw rubber needs to be the copolymer of the present invention in order to exhibit the excellent properties of the present invention. Further, as other synthetic rubber or natural rubber used as a blend, preferred are styrene-butadiene copolymer, cis-1,4-polybutadiene, 1,2-syndiopolybutadiene, and 1,2-vinyl bond content 10%. Up to 90% of polybutadiene rubber, polyisoprene or natural rubber may be used, and one or more of them may be used.

Process oils used for rubber compounding consist of high boiling point components of petroleum fractions and are usually classified into three types according to the chemical structure of the hydrocarbon molecules of the oil. The criteria for classification are the viscosity specific gravity constant (abbreviated as VGC). Depending on the size. VGC is generally 0.790 to 0.849
Those of 0.850 to 0.899 are classified as paraffinic, those of 0.850 to 0.899 are classified as naphthenic, and those of 0.900 or more are classified as aromatic. Among them, since the copolymer of the present invention is used by blending carbon black, an aromatic type is generally used as a process oil, and an aromatic type having VGC of 0.930 or more is particularly preferable.

The amount of the process oil used in the present invention is 100
It is 5 to 60 parts by weight, preferably 5 to 35 parts by weight, based on parts by weight. If the amount of the process oil is less than 5 parts by weight, the dispersion of other compounding agents such as carbon black and a fluxing accelerator is not good, and conversely
If it exceeds 60 parts by weight, the physical properties of the accelerating material obtained are inferior.

Carbon black used in the present invention is FEF, HAF, ISAF
Etc., which are usually used,
30 to 100 parts by weight, preferably 100 parts by weight of the raw rubber,
40 to 75 parts by weight. If it is less than 30 parts by weight, the reinforcing effect is not sufficient, while if it exceeds 100 parts by weight, impact resilience, breaking strength and the like decrease.

The copolymer of the present invention, in addition to the above-mentioned carbon black and process oil for rubber, may further contain other reinforcing agents and fillers such as white carbon, calcium carbonate and magnesium carbonate, and zinc oxide, Stearic acid, an antioxidant, an ozone deterioration inhibitor, a flow accelerating agent, a flow accelerating agent, a wax and the like can be selected and blended as necessary.

The mixing of any of the above-mentioned compounding agents is carried out by a usual means such as Banbury, kneader or open roll.

The rubber composition of the present invention thus obtained, after undergoing a vulcanization step, has many useful applications, for example, tire applications such as tire treads, carcasses, and sidewalls, or extruded products,
It can be used for applications such as automobile window frames and industrial products.

[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 styrene-butadiene copolymer is
It is analyzed by the method recently developed by Tanaka et al. Specifically, the styrene chain distribution is analyzed by gel permeation chromatogram (GPC) of the degradation product obtained by ozone cleavage of all double bonds of the butadiene unit (Proceedings of the Polymer Society of Japan, Vol. 29, No. 9, Item 2055). ).

The temperature difference between the inflection points in the glass transition temperature range of the copolymer (Δ
T) is a DSC (trade name: SSC58) manufactured by Seiko Instruments Inc.
The temperature range from the first change point near the glass transition temperature to the final change point in the endothermic curve obtained by measurement using (0). The measurement conditions were in accordance with ASTM-D3418-82. The ratio w / n of the weight average molecular weight (w) to the number average molecular weight (n) is GPC (trade name: 204 compact type) manufactured by Water Co., and the GPC curve obtained by using tetrahydrofuran as a mobile phase is converted into polystyrene. The weight average molecular weight (w) and the number average molecular weight (n) of were calculated. The styrene monomer content and the polymerization conversion rate in the monomer composition of the polymerization system were measured by a gas chromatography (trade name: G
It was calculated using the monomer conversion obtained by analysis using C7A).

The Mooney viscosity is 10 using the L rotor in the usual way.
It was measured at 0 ° C. 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 tensile strength of the accelerating material was measured according to JIS K6301. The impact resilience was measured at a test temperature of 70 ° C. using a Dunlop tripmeter.
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 11 and Comparative Examples 1 to 11 Samples shown in Table 2 were prepared by the method described below.

Samples A to S were placed under a nitrogen atmosphere in a polymerization vessel with a stirrer made of stainless steel and having an internal volume of about 10 l, and as shown in Table 1, a predetermined amount of cyclohexane, styrene (hereinafter referred to as "first styrene"), 1,3-butadiene. (Hereinafter referred to as “first butadiene”) and tetrahydrofuran were charged, the temperature in the polymerization vessel was adjusted, and then a predetermined amount of n-butyllithium was added to start copolymerization, and the polymerization temperature reached the maximum temperature. After the completion of the copolymerization, a predetermined amount of an organic compound was added as shown in Table 1 and after the reaction for about 10 minutes, 2,6-di-tert-butyl-p-cresol 5g was added as a stabilizer, Obtained by removing the solvent by heating. However, samples A, C, D, F, G, H, I, K, M, N, O,
Q, R, S are from the beginning of the copolymerization, and the samples B, E, J, L, P
From the time of the polymerization conversion rate shown in Table-1, a predetermined amount of the additional addition primary butadiene shown in Table-1 is continuously additionally supplied to complete the copolymerization, and then a predetermined amount of the organic compound shown in Table-1 is added. Obtained. Further, in Sample J, after the completion of the first stage copolymerization, a predetermined amount of the second styrene and the second butadiene were simultaneously charged as shown in Table-1, and the copolymerization was started, and the polymerization conversion rate was 71%. It was obtained by continuously additionally feeding the predetermined amount of the second-added secondary butadiene shown in 1.

Further, in Sample I, after completion of the copolymerization, 0.075 mol (0.3 equivalent) of stannic chloride was added as a coupling agent to 1 mol of active lithium at the terminal to make a part of the copolymer branched, and then It was obtained by adding a predetermined amount of the organic compound shown in Table-1.

In Sample M, 0.18 g of 1,2-butadiene was added to the polymerization system simultaneously with the first styrene and the first butadiene. Further, in sample S, 0.05 g of potassium tert-amyl alcoholate was added to the polymerization system at the start of copolymerization.

Table-2 shows the basic characteristics of Samples A to S. These samples were kneaded in a small pressure kneader according to the formulation of Table 3 and mixed to obtain an unfluxed rubber composition at 145 ° C.
And the physical properties were evaluated. The measurement results are shown in Table-4.
Shown in.

Examples 1 to 11 are particularly excellent in balance of impact resilience, wet skid resistance and wear resistance, and also improved tensile strength, as compared with Comparative Examples 1 to 11.

In Table 1, Ti is the polymerization initiation temperature and Tp is the maximum temperature.

[Effect of the Invention] The random styrene-butadiene copolymer according to the present invention is one in which a specific functional group is bonded to the copolymer chain, and the styrene unit in the copolymer chain has a specific styrene chain. Since it has a distribution and has a specific styrene composition distribution, this copolymer has an excellent balance of impact resilience, wet skid resistance, and abrasion resistance, and an excellent tensile strength. It can be used for tires such as sidewalls, extruded products, automobile window frames, anti-vibration rubber, industrial products, etc., and its industrial significance is great.

[Brief description of drawings]

FIG. 1 shows endothermic curves by DSC measurement of the copolymers obtained in each Example and Comparative Example. ΔT in FIG. 1 indicates the temperature difference between the inflection points in the glass transition temperature region, (a) is sample A, (b) is sample C, (c) is sample J, (d).
Shows the DSC endothermic curve of sample L.

Claims (2)

[Claims] 1. A copolymer of styrene and butadiene using an organolithium compound as a polymerization initiator in a hydrocarbon solvent containing at least one Lewis base, and then i) in the molecule. And a compound having at least one N—R ₁ group (wherein Y represents an oxygen atom or a sulfur atom, R ₁ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group or an aryl group). Ii) Isocyanates represented by the general formula R ₃ -(-N = C = Y) _n (wherein Y represents an oxygen atom or a sulfur atom, R ₃
Is aliphatic, cycloaliphatic, aromatic, or having 2 to 20 carbon atoms
Represents a hydrocarbon group, and n represents an integer of 1,2,3) iii) An organometallic compound represented by the general formula (R ₄ ) _3- MX (wherein R ₄ has 1 to 20 carbon atoms). Represents an alkyl group, an alkoxyalkyl group, and an aryl group, and M is a group IV b of the periodic table.
Represents a metal atom of X, and X represents a halogen atom), and has a Mooney viscosity (ML _{1 + 4} , 100 ° C) of 10 to 150, a weight measured by GPC, to which at least one organic compound selected from the group consisting of Average molecular weight (w) Number average molecular weight (
n), the ratio w / n is 1.1 to 3.0, and the bound styrene content is
10% by weight to 45% by weight, the styrene single chain of one styrene monomer unit of the copolymer is 65% by weight of the total bound styrene.
As described above, the styrene long chain in which 8 or more styrene monomer units are connected is 5% by weight or less of the total bound styrene, and the change in the glass transition temperature range in the endothermic curve analyzed by the differential scanning calorimeter (DSC). Temperature difference between bending points is 15 ℃
The above is a random styrene-butadiene copolymer. 2. Styrene and butadiene are copolymerized with an organolithium compound as a polymerization initiator in a hydrocarbon solvent containing at least one Lewis base, and then i) in the molecule. And a compound having at least one N—R ₁ group (wherein Y represents an oxygen atom or a sulfur atom, R ₁ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group or an aryl group). Ii) Isocyanates represented by the general formula R ₃ -(-N = C = Y) _n (wherein Y represents an oxygen atom or a sulfur atom, R ₃
Is aliphatic, cycloaliphatic, aromatic, or having 2 to 20 carbon atoms
Represents a hydrocarbon group, and n represents an integer of 1,2,3) iii) An organometallic compound represented by the general formula (R ₄ ) _3- MX (wherein R ₄ has 1 to 20 carbon atoms). Represents an alkyl group, an alkoxyalkyl group, and an aryl group, and M is a group IV b of the periodic table.
Represents a metal atom and X represents a halogen atom), and has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10 to 150, a weight measured by GPC, to which at least one organic compound selected from the group consisting of Average molecular weight (w) Number average molecular weight (
n), the ratio w / n is 1.1 to 3.0, and the bound styrene content is
10% by weight to 45% by weight, the styrene single chain of one styrene monomer unit of the copolymer is 65% by weight of the total bound styrene.
As described above, the styrene long chain in which 8 or more styrene monomer units are connected is 5% by weight or less of the total bound styrene, and the change in the glass transition temperature range in the endothermic curve analyzed by the differential scanning calorimeter (DSC). Temperature difference between bending points is 15 ℃
In the raw material rubber containing at least 30% by weight or more of the random styrene-butadiene copolymer, the raw material rubber
A rubber composition comprising 5 to 60 parts by weight of a process oil for rubber and 30 to 100 parts by weight of carbon black, based on 100 parts by weight.