JPS62207342A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber compsn. suitable for use as a tire tread having high resilience and resistance to wear and wet skid, by blending a copolymer obtd. by reacting a specified arom. vinyl compd./conjugated diene living polymer with an org. compd. having a specified atomic group as a raw rubber component. CONSTITUTION:This rubber compsn. contains at least 20wt% copolymer obtd. by reacting the following copolymer (1) with the following compd. (2) as a raw rubber component. (1) An arom. vinyl compd./conjugated diene copolymer having an active terminal, a bonded arom. vinyl compd. unit content of 35-60wt%, a 1,2-bonded conjugated diene moiety content of not more than 35mol% and a block arom. vinyl compd. content of nor more than 5wt% based on the amount of the bonded arom. vinyl compd., obtd. by carrying out a polymn. reaction in the presence of an organolithium initiator. (2) At least one compd. selected from the group consisting of org. compds. having a group of the formula (wherein X is O or S), benzophenones having an amino group and/or a substd. amino group and thiobenzophenones having an amino group and/or a substd. amino group.

Description

Detailed Description of the Invention The present invention relates to a copolymer obtained by reacting an aromatic vinyl compound-conjugated diene copolymer having an active end obtained using an organolithium initiator with an organic compound having a specific atomic group. The present invention relates to a rubber composition containing a polymer as a raw rubber and having improved wear resistance.

(Prior Art) Hitherto, in order to improve wear resistance, polybutadiene cams with a low vinyl content, styrene-getadiene copolymer cams with a low styrene content, and low vinyl content have been used. However, when these cams are used as the main component of a Group 5 acid compound, there is a drawback that wet skid resistance, which is an important characteristic required for a tire tread, is reduced. On the other hand, when polybutadiene with a high vinyl content or styrene-butadiene copolymer with a high styrene content, which has been used to improve wet skid resistance, is used as the main component of a rubber composition, the wear resistance decreases. Furthermore, styrene-butadiene copolymer rubbers with a high styrene content have a drawback in that impact resilience, which is related to tire rolling resistance, is reduced.

Therefore, conventional techniques cannot satisfy all of the wet skid resistance, abrasion resistance, and rebound resilience required of tires at high levels, and improvements are desired.

(Problems to be Solved by the Invention) As a result of intensive research by the present inventors to solve the above-mentioned drawbacks,
By using a copolymer obtained by reacting a specific aromatic vinyl compound-conjugated diene living copolymer with an organic compound having a specific atomic group, abrasion resistance is improved, and the wear resistance and wet resistance are improved. It was discovered that a rubber composition suitable for tire treads with high skid resistance could be obtained, and based on this knowledge, the present invention was completed.

(Rounding Means for Solving the Problem) Thus, according to the present invention, the amount of bound aromatic vinyl compound having an active end copolymerized using organolithium initiation is 35 to 60% by weight, and the conjugated diene unit portion is 1, 2
- The amount of bonded aromatic vinyl compound is 35 molt or less, and the amount of Glock aromatic vinyl compound is 5% by weight of the amount of bonded aromatic vinyl compound.
Aromatic vinyl compound-conjugated diene copolymer (
1) and at least one compound (2) selected from benzophenones and thiobenzophenones having an amino group and/or a substituted amino group (the molecule represents an oxygen or sulfur atom) A rubber composition containing at least 20% by weight of copolymer t-raw rubber component is provided.

The aromatic vinyl compound-conjugated diene copolymer used in the present invention is obtained by copolymerizing an aromatic vinyl compound and a conjugated diene using an organolithium catalyst in a hydrocarbon solvent. The content of the bound aromatic vinyl compound is from 35 to 60% by weight, preferably from 40% by weight to 50% by weight. If the bound aromatic vinyl compound content is less than 35% by weight, the wear resistance and wet skid resistance will be poor.
Exceeding this is not preferable because the impact resilience will drop significantly.

Among the total bonded aromatic vinyl compounds, the amount of aromatic vinyl compounds forming blocks of 8 or more chains measured by the method described in Kobunshi, Vol. 22, p. 1721 (1981) is the total bonded aromatic vinyl compounds. It is necessary that the amount be 5% by weight or less in order to prevent a decrease in recoil elasticity. Preferably it is 4% by weight or less, more preferably 3% by weight or less.

Further, the amount of vinyl in the conjugated diene portion is 35 molti or less. If the vinyl lid exceeds 35 moles, the abrasion resistance will be poor, which is not preferable. Preferably it is 30 to 10 mol.

In the present invention, if the above-mentioned requirements are satisfied, the aromatic vinyl compound and/or the vinyl group in the copolymer are uniformly distributed along the molecular chain, or increase or decrease, It's okay.

The copolymer of the present invention is an aromatic vinyl compound such as styrene, methylstyrene (p or m), α-methylstyrene, chloromethylstyrene, vinyltoluene, and 1-tadiene.
It is a copolymer obtained by copolymerizing conjugated dienes such as isoprene, 1,3-pentadiene, and 2,3-dimethylbutadiene with an organolithium initiator in a hydrocarbon solvent used in ordinary solution polymerization. This copolymer is used as a living copolymer with active ends for reaction with specific compounds described below. Further, in order to further increase rebound resilience, it is preferable that the living copolymer has a conjugated diene such as 1,3-butadiene at the terminal end.

X represents an oxygen atom or a sulfur atom), benzophenones and thiobenzophenones (n) having an amino group and/or a substituted amino group.

Examples of compound (1) include formamide, N, N-
dimethylformamide, N,N-jethylformamide, acetamide, N,N-dimethylacetamide, N,
N-diethylacetamide, aminoacetamide, N,
N-trimethyl-N/, N/-dimethylaminoacetamide, N',N'-dimethylaminoacetamide, N'-ethylaminoacetamide, N,N-dimethyl-N'-ethylaminoacetamide, N,N-dimethylamino Acetamide, N-phenyl diacetamide,
Acrylamide, N,N-dimethylacrylamide,
N,N-dimethylmethacrylamide gropionamide, N,N-dimethylgropionamide, 4-pyridylamide, N,N-dimethyl-4-pyridylamide, benzamide, N-ethylbenzamide, N-phenylbenzamide, N, N-dimethylbenzamide, p-aminobenzamide, Nl, Nl -(p-dimethylamino)
Benzamide, N'.

N'-(p-diethylamino)benzamide, N'-
(p-methylamino)benzamide, N'-(p-ethylamino)benzamide, N,N-dimethyl-N'-
(p-Etheramino)benzamide, N,N-dimethyl-N1. Nl-(p-diethylamino)benzamide, N,N-tumethyl-p-7minobenzamide, N-methyldibenzamide, N-acetyl-N-2-naphthylbenzamide, succinic acid amide, maleic acid amide, phthalic acid amide, N, N, N', N'-tetramethylmaleic acid amide, N, N, N', N'-tetramethylphthalic acid amide, succimide, N-methylsuccimide,
i-reimide, N-methylmaleimide, phthalimide, N
-Methylphthalimide, oxamide, N, N, N', N
'-Tetramethyloxamide, N,N-dimethyl-p-
Amino-pendelacetamide, nicotinamide, N
, N-diethylnicotinamide, 1,2-cyclohexanedicarboximide, N-methyl-1,2-cyclohexanedicarboximide, methyl carbamate, N-methyl-methyl carbamate, N,N-'/ethyl- Ethyl carbamate, ethyl carbanylate, p-N, N-
amides such as ethyl dietheraminocarpanylate;
Imide number; urea, N, N'-dimethylurea, N, N, N
Ureas such as ',N'-tetramethylurea; Anilides such as formanilide, N-methylacetanilide, aminoacetanilide, benzanilide, p,p'-di(N,N-diethyl)aminobenzanilide; 8-caglolactam , N-methyl-6-caglolactam, N-acetyl-ε-caglolactam, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone,
Lactams such as 2-biyridone, N-methyl-2-piperidone, 2-quinolone, N-methyl-2-quinolone, 2-indolinone, N-methyl-2-indolinone; isocyanuric acid, N, N', N'' Examples include isocyanuric acids such as -trimethylisocyanuric acid and their corresponding sulfur-containing compounds.Particularly preferred compounds are compounds in which an alkyl group is bonded to nitrogen.

Examples of compound (n) include 4-aminobenzophenone, 4-dimethylaminobenzophenone, 4-dimethylamino-4'-methylbenzophenone, 4,4'-diaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, and 4-dimethylaminobenzophenone. .4'-bis(diethylamino)
Benzophenone, 4,4'-bis(ethylamino)benzophenone, 3,3'-dimethyl-4,4'-bis(
diethylamino)benzophenone, 3.3'-dimethoxy-4,4'-bis(dimethylamino)benzophenone, 3.3',5.5'-tetraaminobenzophenone,
2,4,6-triaminobenzophenone, 3,3'
, 5,5'-tetra(diethylamine)benzophenone, and their corresponding thiobenzophenones. The substituted amino group is particularly preferably one having an alkyl group, particularly a dialkyl-substituted amino group. Substituents other than amino groups and substituted amino groups may be present as long as they do not adversely affect the reaction.

The reaction between the living copolymer and these organic compounds is described in Japanese Patent Publication No. 61-362 and Japanese Patent Application Laid-Open No. 60-137913.
This is carried out by adding the compound to a solution of the living copolymer and stirring according to the method disclosed in the publication. The compound is usually used in an amount equivalent to or in excess of the number of moles of lithium atoms in the living copolymer. The compound is bonded to the terminal of the copolymer as an atomic group (wherein - represents a polymer chain, R and R' represent substituents, and X is the same as above).

The aromatic vinyl compound-conjugated diene copolymer (
Hereinafter, it may be referred to as a modified copolymer. ) Mooney viscosity (ML, +4.100°C) is not particularly limited, but is usually in the range of 20 to 150. Moreover, the modified copolymer can also be used after being oil-extended.

The modified copolymer used in the present invention may be used alone as a raw material or mixed with other copolymers. When used in mixture with other rubber, 20,31
It is necessary that the content is 11 or more, and if it is less than 20 by weight, the object of the present invention cannot be achieved.

Other rubbers that can be used in combination with the modified copolymer of the present invention include natural rubber, high-cis or low-cis polybutadiene rubber, high-cis polyimprene rubber, and styrene-butadiene copolymer rubber (such as 5nC64 and sctct4). Those that have a bimodal molecular weight distribution bonded with a known coupling agent, those that have been modified as in the present invention, those that do not use a coupling agent, and those that have not been modified.
The amount of bound styrene is 5 to 351ii%, the amount of 1,2-bonds in the butadiene moiety is 10 to 70 mole), polybentenamer, polyoctenamer, etc., depending on the purpose of use of the rubber composition. , but is not limited to these rubbers.

In the rubber composition of the present invention, various compounding agents are added to the above-mentioned rubber according to the purpose. For example, vulcanization systems consisting of sulfur, zinc white, stearic acid, vulcanization accelerators (thiuram series, sulfenamide series, thiazole series, guanidine series, etc.): carbon blacks such as SAF, HAF, F"EF, silica fillers such as talc and charcoal; process oils such as naphthenic and aromatic; plasticizers; anti-aging agents such as phenolic and amine, and antiozonants. The compounding agent is mixed with raw rubber using a mixer such as a Banbury or roll mixer to form a compounded rubber composition.

By using the rubber composition of the present invention, abrasion resistance,
The comb composition of the present invention is particularly suitable for tire treads because a vulcanizate with excellent anti-resilience properties can be obtained, but it can also be used for shoe soles, flooring materials, etc. .

Incidentally, the amount of 1,2-bond in the present invention is determined by the Hympton method using infrared rays.

The present invention 8Af will be explained in more detail by giving examples below. In addition, parts and parts in Examples and Comparative Examples are based on the weight of an unbroken hook. In addition, various physical properties were measured according to the following methods.

Tensile properties were measured according to JTSK-6301.

The impact resilience at 60°C was determined by testing a test piece left in an atmosphere at 60°C using the test machine described in JrSK-6301 (L'1ipk・
Psndulum). Wet skid resistance was measured using an I-tuple skid tester (manufactured by Stanley, UK) at 23°C according to ASTM E-303-7.
Measurements were made on road surface No. 4 (3M outdoor type B, black Safety Walk). The abrasion test was conducted using a Pico abrasion tester.

Preparation Example A method for producing a styrene-getadiene copolymer (hereinafter referred to as a modified copolymer) with a high styrene content obtained by reacting with the compound of the present invention used in the following examples is shown.

After washing and drying a stainless steel autoclave with an internal volume of 101, and purging with dry nitrogen, 1,3-getadiene so
, p, 400 g of styrene 4501 cyclohexane was charged. When the temperature of the contents reached 65°C, t''8 m mot of n-butyllithium (n-hexane solution) was added to initiate polymerization.The polymerization temperature was gradually raised to 90°C.
℃, 1,3-butadiene 500. P was added and polymerization was continued. When the polymerization conversion rate reached approximately 1ook, 8 m rnoL of the compound 4 listed in Table 2 such as N, N, N', N'-tetramethylurea as a reactant was added.
was added and reacted for 20 to 30 minutes. After that, 5 d of methanol was added to stop the reaction, and the polymer solution tl-2.6
-di-t-butyl-p-cresol (BHT) 1.
The resulting polymer was taken out into a 5% methanol solution and coagulated and dried. In this way, the invention examples 1 to 1 listed in Table 2
A modified copolymer of No. 6 was obtained. In Comparative Example 7, the polymer solution was coagulated and dried without adding any reactants.

Depending on the styrene content in the styrene-butadiene copolymer, the amount of styrene and 1,3-butadiene to be charged are changed,
Tetrahydrofuran (
Modified copolymers listed in Table 3 were obtained by the same operations as above except that an appropriate amount of THF)'i was added.

The content of bound styrene and the amount of vinyl in the butadiene moiety of the modified copolymer thus obtained were determined by infrared spectroscopy (Hangton method).

Example 1 The modified copolymer listed in Table 2 obtained in the production example and the compounding agent listed in Table 1 were mixed using a 0.251' Banbury type mixer and a roll, and the resulting compounded rubber The composition was press-vulcanized at 160° C. for 10 to 20 minutes to prepare test pieces for measuring physical properties, and the vulcanized physical properties were measured. The results are shown in Table 2.

Table 1 Note> (11N-Inglobiru N/-7EnilouP-
Phenylenediamine (2) N-cyclohexyl 2-
Penzothiazyl sulfenamide From the results in Table 2, it can be seen that compared to the modified copolymer of the present invention and the unmodified copolymer, there is no decrease in wet skid resistance, wear resistance,
It can be seen that the rebound resilience is greatly improved. Comparative Example 8 shows the results for a standard tire tread dem, and it can be seen that the inventive example has almost the same wear resistance as this, but has high wet skid resistance and high rebound resilience. .

Example 2 Vulcanized physical properties were measured in the same manner as in Example 1 using the modified copolymers listed in Table 3 prepared in the same manner as in the Production Examples. The results are also listed in Table 3.

The results in Table 3 show that when the styrene content or vinyl content falls outside the range of the present invention, either abrasion resistance, wet skid resistance, or impact resilience decreases.

Example 3 Table 4 shows the physical properties of a blend of the modified copolymer of the present invention and natural rubber or high-cis polybutadiene rubber, which are typical examples of existing rubbers. A test piece was prepared in the same manner as in Example 1.

From the results in Table 4, it is clear that if the proportion of the modified copolymer of the present invention contained in the rubber component is outside the claimed range, the abrasion resistance or wet skid resistance will drop significantly, making it impossible to achieve the object of the present invention. Recognize.

Claims (1)

[Claims] The amount of bound aromatic vinyl compound having an active terminal copolymerized using an organolithium initiator is 35 to 60% by weight.
, an aromatic vinyl compound-conjugated diene copolymer in which the amount of 1,2-bonds in the conjugated diene unit portion is 35 mol% or less, and the amount of block aromatic vinyl compound is 5% by weight or less of the amount of bonded aromatic vinyl compounds. Combined (1) and ▲There are mathematical formulas, chemical formulas, tables, etc. in the molecule▼Organic compounds with bonds (
(wherein X represents an oxygen or sulfur atom), a copolymer obtained by reacting with at least one compound (2) selected from benzophenones and thiobenzophenones having an amino group and/or a substituted amino group 1. A rubber composition comprising at least 20% by weight of a rubber compound as a raw rubber component.