JP2003301075A - Styrene butadiene rubber composition for low temperature and its molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a styrene butadiene rubber composition capable of giving a molded body having a high cis 1,4-bonding fraction and good in both of wet characteristics and low temperature characteristics and to provide its molded body. <P>SOLUTION: The styrene butadiene rubber composition (SBR) for low temperature uses 10-50 pts.wt. of a styrene butadiene rubber and 50-90 pts.wt. of a rubber having ≤-50°C glass transition temperature as a rubber raw material and contains a filler, additives, a plasticizer and a crosslinking agent, and the styrene butadiene rubber is a high cis-styrene butadiene rubber (high cis-SBR) obtained by copolymerizing styrene and butadiene by adding (A) a transition metal metallocene catalyst, (B) at least one kind of a compound selected from among organic aluminum compounds and aluminoxane and (C) an electron attractive compound. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a styrene-butadiene rubber composition which gives a vulcanized rubber excellent in low-temperature performance, and a styrene-butadiene rubber molded body obtained by molding and vulcanizing the styrene-butadiene rubber composition.

[0002]

2. Description of the Related Art Needless to say, studless tires are used in cold regions, and are required to have low temperature performance such as maintaining a predetermined hardness even at low temperatures. As a result of emphasizing such low temperature performance, conventionally, rubber having a low glass transition temperature (Tg), specifically natural rubber or butadiene rubber, has been used as a raw material for a tread of a studless tire. All have a problem that the performance on a road surface wet with water, that is, the wet performance is not good.

Styrene-butadiene rubber (SBR) is a widely used synthetic rubber, and is widely used as a rubber material for a tread which is a road ground contact portion of a tire for passenger cars. Conventional SBR is based on emulsion polymerization,
It was manufactured by a solution anion polymerization method.

However, the SBR produced by the emulsion polymerization method and the solution anion polymerization method is excellent in the wet performance of tires, but in any case, the fraction of cis-1,4-bond of butadiene does not exceed 40%. Therefore, the rubber composition using such a conventional SBR does not have sufficient low temperature performance.

In order to improve the low temperature performance of SBR, SBR
With high cis-1,4-bond fraction of butadiene in
It is considered that R is effective, but until now, cis1,
No SBR with a high 4-bond fraction is known. As a polymerization method for increasing the cis-1,4-bond fraction in the polymerization of butadiene, a production method using a transition metal metallocene catalyst is known (Macromol. Chem. Phy.
s. , 201, 393, 2000).

[0006]

However, in the polymerization method using the above transition metal metallocene catalyst, the S
The molecular weight of BR was not high, and the mechanical strength of the molded product as a rubber composition was not sufficient, and it could not be used especially for applications requiring high strength such as tires.

It is an object of the present invention to provide a styrene-butadiene rubber composition which has a high cis 1,4-bond fraction and gives a molded product having both good wet performance and low temperature performance, and a molded product thereof.

[0008]

The low temperature styrene-butadiene rubber (SBR) composition of the present invention comprises 10 to 50 parts by weight of styrene-butadiene rubber and 50 to 90 parts by weight of rubber having a glass transition temperature of -50 ° C or lower. As rubber raw material, filler,
The styrene-butadiene rubber contains an additive, a plasticizer, and a cross-linking agent, and the styrene-butadiene rubber has at least one compound selected from (A) a transition metal metallocene catalyst, (B) an organoaluminum compound and an aluminoxane, and (C) electron withdrawing. -Cis styrene-butadiene rubber (high-cis SBR) obtained by copolymerizing styrene and butadiene by adding a polymerizable compound
Is characterized in that.

By using the above-mentioned composition, a styrene-butadiene rubber composition which gives a molded article having good wet performance and low-temperature performance is obtained.

The amount of high cis SBR used is 100
When the amount is less than 10 parts by weight, the properties of high cis SBR are not sufficiently exhibited, and when it exceeds 50 parts by weight, problems such as low temperature performance and abrasion resistance are deteriorated.

As the rubber raw material having a glass transition temperature (Tg) of −50 ° C. or lower, known rubber raw materials can be used, but the vulcanized rubber has excellent mechanical strength and good compatibility with SBR. Therefore, it is preferable to use natural rubber or butadiene rubber. You may use these together.

The high cis styrene butadiene rubber is
It is preferable that the weight average molecular weight is 200,000 or more and the cis 1,4-bond content is 60% or more.

Since the weight average molecular weight is 200,000 or more, the rubber composition using this SBR becomes an SBR-containing rubber molded product having high mechanical strength, and cis-1,4-
When the binding fraction is 60% or more, a tire excellent in both wet performance and low temperature performance can be obtained when this SBR is used as a tire and a red material.

The cis 1,4-bond fraction is the fraction when the total of cis 1,4-bond, trans 1,4-bond and 1,2-bond of butadiene constituting the polymer is 100%. (%). The cis 1,4-bond fraction of the present invention is measured by an infrared absorption spectrum method.

The high cis styrene butadiene rubber used in the low temperature styrene butadiene rubber composition of the present invention is preferably produced by solution polymerization in which a polymerization reaction is carried out in an organic solvent.

By the solution polymerization, a high molecular weight styrene-butadiene rubber having a weight average molecular weight of 200,000 or more can be easily produced.

The styrene-butadiene rubber molded product of the present invention is characterized by being obtained by molding and vulcanizing the low-temperature styrene-butadiene rubber composition according to any one of claims 1 to 3.

The vulcanized rubber molded product is a molded product excellent in rolling resistance and wear resistance, and is particularly suitable for applications requiring wear resistance such as a ground contact portion of a tire, a belt conveyor, rollers and crawlers. It is a molded body.

The hardness of the vulcanized rubber molded body is preferably a Shore A hardness (-5 ° C.) of 45 to 65.

The rubber molding having such hardness is particularly suitable as a tread material for studless tires.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hicis SBR used in the present invention
Will be described. The method for producing a high cis styrene butadiene rubber of the present invention comprises (A) a transition metal metallocene catalyst,
At least one compound selected from (B) an organoaluminum compound and an aluminoxane, and (C) an electron-withdrawing compound are added to copolymerize styrene and butadiene.

The most characteristic feature of the present invention is that (C) an electron-withdrawing compound is added to copolymerize styrene and butadiene.

By the production method having such a constitution, a copolymer having a high molecular weight and a practical mechanical strength and at the same time a high cis 1,4-bond fraction of butadiene can be obtained.

The preferred addition amount of the components (A) to (C) is
For monomer (styrene + butadiene etc.) (A)
Ingredients are monomer / (A) = 10 ² to 10 ⁵ (molar ratio)
Is. The ratio of (A) / (B) is 1 / 0.1 when an organoaluminum compound is used as the component (B).
It is preferably 1/1000 (molar ratio), and (B)
When using aluminoxane as a component, 1/1
It is preferably 0 to 1/5000. Also (A) /
The ratio of (C) is preferably 1 / 0.1 to 1/10.

(A) Metallocene type complex of transition metal compound
Are known compounds of transition metal compounds of Groups 4 to 8 of the periodic table.
Talocene-type complexes can be used. Specifically, titanium, di
Metallocene type of Group 4 transition metals such as ruconium
Complex (eg CpTiCl ₃ Etc.), vanadium, ni
Metalloces of transition metals of Group 5 of the periodic table, such as bromine and tantalum
Group-type complexes, Group 6 transition metal metallocene-type complexes such as chromium
Metals of Group 8 transition metals such as body, cobalt and nickel
Examples thereof include sen-type complexes.

Of these, the use of a metallocene type complex of a transition metal of Group 5 of the periodic table is preferable. Examples of the metallocene-type complex of a transition metal compound of Group 5 of the periodic table include compounds represented by the following general formula. (1) RM · L _a (2) R _n MX _2-n · L _a (3) R _n MX _3-n · L _a (4) RMX ₃ · L _a (5) RM (O) X ₂ · L _a (6) R _n MX _3-n (NR ′) (wherein, n is 1 or 2, and a is 0, 1 or 2) Among the above compounds, (1) RM · L _a , (4 ) RM
It is more preferable to use X ₃ · L _a and (5) RM (O) X ₂ · L _a . The metal M is preferably at least one of vanadium and titanium.

In the general formulas (1) to (6), R is
Is a cyclopentadienyl group, substituted cyclopentadienyl
Group, indenyl group, substituted indenyl group, fluorenyl group
Alternatively, it represents a substituted fluorenyl group. Substituted cyclopentadiene
Nyl group, substituted indenyl group or substituted fluorenyl group
As the substituent, methyl, ethyl, propyl, i-
Propyl, n-butyl, i-butyl, sec-butyl,
Linear aliphatic hydrocarbon groups such as t-butyl and hexyl
Or branched aliphatic hydrocarbon groups, phenyl, tolyl, naphth
Aromatic hydrocarbon groups such as chill and benzyl, trimethylsilyl
And hydrocarbon groups containing silicon atoms such as
Be done. In addition, the cyclopentadienyl ring is partially linked to X.
Sea urchin dimethyl silylene (Me₂ Si), dimethyl methyle
(Me ₂ C), methylphenylmethylene (PhMe
C), diphenylmethylene (Ph₂C), ethylene,
Also included are those linked by a bridging group such as ethylene.

Specific examples of the substituted cyclopentadienyl group are methylcyclopentadienyl group, 1,2-dimethylcyclopentadienyl group, 1,3-dimethylcyclopentadienyl group, 1,2,3- Trimethylcyclopentadienyl group, 1-benzyl-2,3,4,5-tetramethylcyclopentadienyl group, 1-trimethylsilyl-
2,3,4,5-tetramethylcyclopentadienyl group and the like can be mentioned.

Specific examples of the substituted indenyl group include 1,
2,3-trimethylindenyl group, heptamethylindenyl group, 1,2,4,5,6,7-hexamethylindenyl group and the like can be mentioned. Specific examples of the substituted fluorenyl group include a methylfluorenyl group and the like.

Among the R's exemplified above, a cyclopentadienyl group (Cp), a methylcyclopentadienyl group,
Pentamethylcyclopentadienyl group, indenyl group,
The use of 1,2,3-trimethylindenyl group is more preferred.

In the general formulas (1) to (6), X is hydrogen, halogen (F, Cl, Br, I), and has 1 to 2 carbon atoms.
0 represents a hydrocarbon group, an alkoxy group, or an amino group.
All Xs may be the same or different from each other. Specific examples of the hydrocarbon group having 1 to 20 carbon atoms include:
A linear or branched aliphatic hydrocarbon group such as methyl, ethyl, propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, phenyl, tolyl, An aromatic hydrocarbon group such as naphthyl and benzyl. Among these, methyl,
Benzyl and the like are preferable. R may be a trimethylsilylmethyl group.

Examples of the alkoxy group include alkyloxy groups such as methoxy, ethoxy, phenoxy, propoxy and butoxy. Examples of the amino group include dimethylamino, diethylamino, diisopropylamino and the like.

In the general formulas (1) to (6), L is a Lewis base, which is a general Lewis basic inorganic or organic compound capable of coordinating with a metal. Compounds having no active hydrogen are particularly preferable, and specific examples thereof include ethers, esters, ketones, amines, phosphines, silyloxy compounds, olefins, dienes, aromatic compounds and alkynes.

In the general formula (6) R _n MX _3-n (NR ′), NR ′ is an imide group, and R ′ has 1 to 25 carbon atoms.
Is a hydrocarbon substituent. Specific examples of R'include methyl, ethyl, propyl, i-propyl, n-butyl, i.
-Butyl, sec-butyl, t-butyl, hexyl, octyl, neopentyl and other straight-chain aliphatic hydrocarbon groups or branched aliphatic hydrocarbon groups, phenyl, naphthyl, benzyl, 1-phenylethyl, 6-dimethylphenyl And aromatic hydrocarbon groups such as It may be an alkylsilyl group such as trimethylsilyl.

The compound of the general formula (1) RM · L _a , that is, _a transition metal compound of Group 5 of the periodic table having a cycloalkadienyl group ligand and an oxidation number of +1 includes cyclopentadienyl (benzene) vanadium, Cyclopentadienyl (toluene) vanadium, cyclopentadienyl (xylene) vanadium, cyclopentadienyl (ferrocene)
Vanadium, tetramethyl cyclopentadienyl (benzene) vanadium, indenyl (benzene) vanadium, cyclopentadienyl tetracarbonyl vanadium, etc. can be mentioned.

Among the compounds represented by the general formula (2) R _n MX _2-n · L _a , when n = 1, that is, when one cycloalkadienyl group is used as a ligand, another sigma bond is used. As a hydrogen atom, a halogen atom such as chlorine,
Methyl group, phenyl group, benzyl group, neopentyl group,
It may have a hydrocarbon group such as a trimethylsilyl group, an alkoxy group such as a methoxy group, an ethoxy group and an isopropoxy group, and a dialkylamino group such as a dimethylamino group and a diisopropylamino group.

Further, as another ligand, a neutral Lewis base such as amine, amide, phosphine, ether, ketone, ester, olefin, diene, aromatic hydrocarbon or alkyne can be contained. Lewis bases without active hydrogen are preferred.

In the compound represented by the general formula (2) R _n MX _2-n · L _a , when n = 2, that is, when two cycloalkadienyl groups are contained as ligands, each cycloalkadiene The enyl rings may be linked to each other by a cross-linking group such as dimethylsilylene, dimethylmethylene, methylphenylmethylene, diphenylmethylene, ethylene and substituted ethylene.

Among the compounds represented by R _n MX _2-n · L _a of (2) of the present invention, n = 1 and the oxidation number +2, a specific example of the periodic table group 5 transition metal compound is chloro. Cyclopentadienyl (tetrahydrofuran) vanadium,
Chlorocyclopentadienyl (trimethylphosphine)
Examples include vanadium.

(2) Of the compounds represented by R _n MX _2-n · L _a of the present invention, n = 2, that is, the periodic table having an oxidation number of +2 having two cycloalkadienyl groups as ligands. 5
Specific examples of the group transition metal compound include biscyclopentadienyl vanadium, bis (methylcyclopentadienyl) vanadium, and bis (1,2-dimethylcyclopentadienyl) vanadium.

(3) Among the specific compounds represented by R _n MX _3-n · L _a , the compounds with n = 1 include cyclopentadienyl vanadium dichloride, methylcyclopentadienyl vanadium dichloride, and fullerene. Examples thereof include dichlorides such as oleyl vanadium dichloride, and methyls obtained by substituting the chlorine atom of these compounds with a methyl group.

(3) Examples of the compound represented by R _n MX _3-n · L _a include cyclopentadienyl vanadium dimethoxide and cyclopentadienyl vanadium dii.
-Propoxide, cyclopentadienyl vanadium dit-butoxide, cyclopentadienyl vanadium diphenoxide, cyclopentadienyl vanadium methoxy chloride, cyclopentadienyl vanadium i-
Examples thereof include alkoxides such as propoxycyclolide, cyclopentadienyl vanadium t-butoxycyclolide, and cyclopentadienyl vanadium phenoxycyclolide, and methyl compounds in which chlorine atoms of these compounds are substituted with methyl groups.

(3) Among the specific compounds represented by R _n MX _3-n · L _a , as the compound of n = 2, dicyclopentadienyl vanadium chloride and bis (methylcyclopentadienyl) Chloride such as vanadium chloride, bis (1,3-dimethylcyclopentadienyl) vanadium chloride, bis (trimethylsilylcyclopentadienyl) vanadium chloride, diindenyl vanadium chloride, or the chlorine atom of these compounds with a methyl group Examples include substituted methyl compounds.

In the compound represented by the general formula (3) R _n MX _3-n · L _a , R may be bonded by a hydrocarbon group or a silyl group. Examples of such compounds include chlorides such as dimethylbis (η5-cyclopentadienyl) silanevanadium chloride and dimethylbis (tetramethyl-η5-cyclopentadienyl) silanevanadium chloride, or chlorine atoms of these compounds in which a methyl group is used. And a methyl form substituted with.

[0045] As a general formula (4) Specific compound represented by RMX ₃ · L _a include compounds of the following (i) ~ (vii).

(I) Cyclopentadienyl vanadium trichloride, mono-substituted cyclopentadienyl vanadium trichloride, cyclopentadienyl titanium trichloride (ii) 1,2- or 1,3-disubstituted cyclopentadienyl vanadium Trichloride, 1,2- or 1,3-
Tri-substituted cyclopenta such as di-substituted cyclopentadienyl titanium trichloride (iii) (1,2,3-trimethylcyclopentadienyl) vanadium trichloride, 1,2,4-trimethylcyclopentadienyl) vanadium trichloride Dienyl vanadium trichloride may be mentioned.

(Iv) tetra-substituted or penta-substituted cyclopentadienyl vanadium trichloride (v) indenyl vanadium trichloride, (vi)
Substituted indenyl vanadium trichloride (vii); monoalkoxides, dialkoxides, trialkoxides etc. in which the chlorine atom of the compounds of (i) to (vi) are substituted with an alkoxy group are represented by the general formula (5) RM (O) X ₂ . Specific examples of the compound include cyclopentadienyloxovanadium dichloride, methylcyclopentadienyloxovanadium dichloride, benzylcyclopentadienyloxovanadium dichloride, (1,3-dimethylcyclopentadienyl) oxovanadium dichloride, etc. Is mentioned. Also included are methyl compounds in which the chlorine atom of each of the above compounds is replaced with a methyl group.

Examples of the compound represented by the general formula (5) RM (O) X ₂ include cyclopentadienyloxovanadium dimethoxide and cyclopentadienyloxovanadium di-propoxide. A methyl form in which the chlorine atom of each of the above compounds is replaced with a methyl group,
(Cyclopentadienyl) bis (diethylamido) oxovanadium, (Cyclopentadienyl) bis (di-
Propylamido) oxovanadium and the like.

Specific examples of the compound represented by the general formula (6) R _n MX _3-n (NR ′) include cyclopentadienyl (methylimido) vanadium dichloride, cyclopentadienyl (phenylimido) vanadium dichloride, Examples thereof include cyclopentadienyl (2,6-dimethylphenylimide) vanadium dichloride.

(6) The compound represented by R _n MX _3-n (NR ′) further includes cyclopentadienyl vanadium (phenylimido) dimethoxide, cyclopentadienyl vanadium (phenylimido) di i-propoxide. Cyclopentadienyl vanadium (phenylimide) (i-propoxy) chloride, (cyclopentadienyl) bis (diethylamido) vanadium (phenylimide), (cyclopentadienyl) bis (di-propylamido) vanadium (phenylimide) ) And the like.

As the organoaluminum compound used as the component (B), known organoaluminum compounds can be used. Specific examples include trialkylaluminum such as trimethylaluminum, triethylaluminum and triisobutylaluminum, and dialkylhalides such as diethylaluminum chloride.

The chain aluminoxane which can be used as the component (B) is obtained by contacting an organoaluminum compound with a condensing agent, and has the general formula (-Al (R ') O-). The chain | strand-shaped aluminoxane shown by n is mentioned. R'is a hydrocarbon group having 1 to 10 carbon atoms, and includes those partially substituted with a halogen atom and / or an alkoxy group. n is the degree of polymerization of the chain aluminoxane, and is 5 or more, preferably 10 or more.
Examples of R'include methyl, ethyl, propyl and isobutyl groups. Of these, a methyl group and an ethyl group are preferable. Examples of the organoaluminum compound used as a raw material for the aluminoxane include the above-mentioned trialkylaluminums such as trimethylaluminum, triethylaluminum and triisobutylaluminum, and mixtures thereof.

Typical examples of the condensing agent used in the production of the chain aluminoxane include water, but in addition to this, any condensing agent with which the trialkylaluminum undergoes a condensation reaction, such as adsorbed water such as an inorganic substance, or geo -Ru and the like.

As the electron-withdrawing compound (C), a known electron-withdrawing compound can be used. Specific examples thereof include acetic acid derivatives such as trichloroacetic acid and trifluoroacetic acid, tetrachlorobenzoquinone (chloranil), benzoquinone derivatives such as tetrafluorobenzoquinone, and tetracyanoquinodimethane (TCNQ). These electron-withdrawing compounds may be used alone or in combination of two or more kinds.

The high cis SBR of the present invention comprises styrene and butadiene as monomers,
The use of a copolymer of another monomer in a range that does not impair the characteristics of (1) is a preferred embodiment from the viewpoint of improving the characteristics. As such other copolymerizable monomer,
Conjugated diene monomers such as isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2,4-hexadiene, 4-methylpentadiene, ethylene, propylene, butene-1, butene-2, isobutene, pentene-
1, mono-olefins such as hexene-1 and octene-1,
Examples thereof include cyclic monoolefins such as norbornene and aromatic monoolefins such as α-methylstyrene.

As the solvent used in the production of the high cis styrene butadiene rubber of the present invention, known solvents used in the polymerization of styrene butadiene rubber can be used without limitation. Specifically, aromatic solvents such as toluene, xylene, and tetralin, n-hexane, n-pentane, n
Examples of suitable solvents include aliphatic or alicyclic solvents such as heptane, cyclohexane, cyclopentane, cycloheptane, decalin and the like.

As a polymerization method for producing SBR, a known method can be used. The polymerization may be either solution polymerization or bulk polymerization, but is preferably solution polymerization as described above.

The solution polymerization method is carried out by, for example, charging an organic solvent, a styrene monomer and a butadiene monomer in a predetermined ratio into a reaction vessel, adjusting the temperature to a predetermined temperature, and adding a catalyst.

The polymerization temperature is about -10 ° C to 150 ° C, more preferably 0 to 120 ° C. The polymerization time is appropriately set depending on the temperature and the target molecular weight, but is about 3 minutes to 10 hours.

The polymerization reaction is stopped by adding a solvent such as alcohol or a solvent containing an inhibitor to the polymerization system and stirring. After the completion of the polymerization, the SBR can be obtained by, for example, reprecipitating the solution in a non-solvent of SBR, filtering and then drying, or removing the solvent from the solution after the polymerization.

In the SBR composition of the present invention, the above S
As the rubber material which can be used in combination with BR, the rubber material which is usually blended with SBR can be used without limitation,
Examples of suitable rubber materials include natural rubber and butadiene rubber (BR).

In the SBR composition of the present invention, necessary fillers, additives, process oils, vulcanizing agents and vulcanization accelerators are used. As these materials, known materials in the technical field of rubber can be used without limitation (see “Rubber Technology Fundamentals” edited by Japan Rubber Association).

[0063]

EXAMPLES Examples and the like specifically showing the constitution and effects of the present invention will be described below. <Production Example of SBR> (Production Example 1) A 1.5 L capacity autoclave equipped with a stirrer was replaced with nitrogen, 300 ml of toluene was used as a solvent, and cyclopentadienyl titanium trichloride (CpTiCl) was used.
₃ ) 2.1 mmol, methylaluminoxane (MA
O) 210 mmol, chloranil 2.1 mmol
(CpTiCl ₃ / chloranil = 1/1 (molar ratio)) was charged, and 37.5 ml of butadiene and 37.5 ml of styrene.
Was added and polymerization was carried out at 60 ° C. for 30 minutes. 10 minutes after the start of polymerization, a methanol solution in which a small amount of pt-butylcatechol as a polymerization inhibitor was dissolved was added to the polymerization solution,
The polymerization reaction was stopped. By removing toluene from this solution, an SBR polymer (Sample 1) was obtained.

Production Example 2 SBR was prepared in the same manner as in Production Example 1 except that the polymerization temperature was 0 ° C. and the polymerization time was 120 minutes.
A polymer (Sample 2) was obtained.

<Production of Compositions> (Examples 1 to 3 and Comparative Examples 1 and 2) The composition shown in Table 1 (total 100 parts by weight of rubber raw material) was used as a rubber raw material, and carbon black (ISAF class) 40 was used. By weight, 10 parts by weight of silica (wet silica) and 20 parts by weight of naphthenic process oil were kneaded with a Banbury mixer to prepare a masterbatch. After the master batch discharged from the Banbury mixer is made into a sheet with a kneading roll and cooled,
1.5 parts by weight of sulfur (5% oil-treated powdered sulfur) as a vulcanizing agent using a kneading roll, vulcanization accelerator Nt-butyl-2
-1.5 parts by weight of benzothiazyl sulfenamide was kneaded to obtain an SBR composition. Other rubber materials used as a rubber raw material are RSS # 1 for natural rubber, BR-01 (manufactured by JSR) and butadiene rubber for SBR1502 (manufactured by JSR).

[0066]

[Table 1] The unvulcanized rubber compositions obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were heated in a mold at 160 ° C. for 20 minutes to obtain molded products, and low temperature performance evaluation and wet performance evaluation were performed. .
The evaluation results are shown in Table 3.

<Evaluation> (Molecular weight) GPC LC-10 (manufactured by Shimadzu Corporation) was used, tetrahydrofuran (THF) was used as a mobile phase, and measurement was carried out at 40 ° C. to obtain a weight average molecular weight (Mn in terms of standard polystyrene). ), Number average molecular weight (Mw) and M
n / Mw was calculated.

(Polymer Microstructure) The cis 1,4-bond fraction and the 1,2-bond fraction were measured by infrared absorption spectroscopy. Paragon 1000 (manufactured by Perkin Elmer) was used for the measurement. The measurement was performed by the transmission method.
The result is absorption intensity of 735cm ^-1 attributed to cis 1,4 bond of butadiene units, absorption intensity of 967 cm ^-1 attributed to trans 1,4 bond, attributed to 1,2-linked 911cm The absorption intensity of ^-1 was measured and calculated from the intensity ratio. In Table 2, SBR (Sample 1),
The measurement results of the molecular weight and microstructure of SBR (Sample 2) and SBR1502 are shown.

(Low temperature performance) The low temperature performance was evaluated by the hardness at -5 ° C. The hardness is measured according to JIS K 6253.
Shore A hardness was measured in accordance with.

(Wet Performance) Wet performance was evaluated by using a Lupke type impact resilience tester. Measurement is JISK
It carried out based on 6301. The results are shown as an index with the result of Comparative Example 1 using natural rubber and butadiene rubber as 100. The smaller this index, the better the wet performance.

[Table 2]

[Table 3] From the results of Table 2, SB constituting the SBR composition of the present invention
R is a high cis SBR with more than 60% cis 1,4-bonds
In addition, the weight average molecular weight is 365,000 (Sample 1) and 585,000 (Sample 2), which is a high molecular weight equivalent to that of the conventional emulsion polymerization SBR.

From the results shown in Table 3, it is understood that the vulcanized rubber obtained by vulcanizing the SBR composition of the present invention is superior to the conventional low temperature rubber in both low temperature performance and wet performance.

Claims (4)

[Claims] 1. A rubber raw material comprising 10 to 50 parts by weight of styrene-butadiene rubber and 50 to 90 parts by weight of rubber having a glass transition temperature of -50 ° C. or less, and containing a filler, an additive, a plasticizer and a crosslinking agent, The styrene-butadiene rubber is copolymerized with styrene and butadiene by adding (A) a transition metal metallocene catalyst, (B) at least one compound selected from an organoaluminum compound and an aluminoxane, and (C) an electron-withdrawing compound. A low-temperature styrene-butadiene rubber composition, which is a high-cis styrene-butadiene rubber (high-cis SBR) obtained by the above. 2. The low-temperature styrene-butadiene rubber composition according to claim 1, wherein the high-cis styrene-butadiene rubber has a weight average molecular weight of 200,000 or more and a cis 1,4-bond content of 60% or more. 3. The low-temperature styrene-butadiene rubber composition according to claim 1, wherein the high-cis styrene-butadiene rubber is polymerized in an organic solvent. 4. A styrene-butadiene rubber molded body obtained by molding and vulcanizing the styrene-butadiene rubber composition for low temperature according to claim 1.