JP2002012702A - Rubber composition - Google Patents

Abstract

(57) [Problem] To provide a rubber composition having excellent mechanical strength, fatigue resistance, wear resistance and low heat generation. SOLUTION: (i) polyisoprene-based rubber, (ii)
A block copolymer comprising a polybutadiene rubber and (iii) a polybutadiene block (A) having a 1,4-cis bond content of 40% by weight or more in a 1,3-butadiene unit and a polyisoprene block (B). A rubber composition prepared by blending a coalesced substance and having a block copolymer (iii) content of 0.5 to 25 parts by weight based on 100 parts by weight of the total of components (i) and (ii).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel rubber composition, and more particularly, to a rubber composition suitable for a tire tread containing a polyisoprene rubber and a polybutadiene rubber as main components.

[0002]

2. Description of the Related Art Conventionally, as a rubber raw material for a tire, a polybutadiene rubber is generally mixed with a polyisoprene rubber represented by a natural rubber. When the polybutadiene rubber is mixed, the abrasion resistance is improved as compared with the case where the natural rubber is used alone, but the mechanical strength is reduced. Therefore, a method of further blending a block copolymer has been proposed for the purpose of improving mechanical strength.

[0003] For example, in J. Apply. Polym. S
ci. , 49 (1993) and RCT. 66 (199
3) describes a method in which a butadiene-isoprene block copolymer produced using n-butyllithium as a polymerization initiator is blended as a compatibilizer. The rubber composition containing this block copolymer has excellent mechanical strength and abrasion resistance.

JP-A-8-134267 discloses that a styrene content of 0 to 30% by weight, a butadiene content of 100 to 70% by weight, and a 1,2-vinyl bond content of 5 to 40%.
Rubber composition for a tire tread, comprising a block copolymer having a styrene content of 0 to 30% by weight and a butadiene content of 100 to 70% by weight and a 1,2-vinyl bond content of 70% or more. Is described. This rubber composition is excellent in tear strength and ice skid resistance.

Further, Japanese Patent Application Laid-Open No. 8-193145 discloses that a styrene content (St) of 35% by weight or less, a butadiene content (Bd) of 65% by weight or more, and a 1,2-vinyl bond content (Vn) of 5 to 80%. A poly (styrene-butadiene) block or a polybutadiene block having a 1,2-vinyl bond content of more than 10% and not more than 30%, and a polyisoprene having a 1,4-cis bond content of not less than 70% by weight and satisfying a relationship of Vn ≦ 2St + 30. A rubber composition containing a block copolymer composed of blocks is described. This rubber composition is excellent in abrasion resistance without lowering grip performance, low fuel consumption performance (low heat generation), and low-temperature flexibility.

[0006] Each of the compounds is excellent in mechanical strength and abrasion resistance as compared with those not containing a block copolymer, but with the recent development of technology, As a material for a tire, a material having better mechanical strength, fatigue resistance, wear resistance and low heat generation is required.

[0007]

An object of the present invention is to provide a rubber composition having excellent mechanical strength, fatigue resistance, abrasion resistance and low heat generation.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object and found that the 1,4-cis bond content in the butadiene block of the block copolymer used as the compatibilizing agent was They have found that they greatly affect the properties of the product, and have completed the present invention based on such findings. Thus, according to the present invention, (i) a polyisoprene-based rubber, (ii) a polybutadiene-based rubber, and (iii) a polybutadiene-based block having a 1,4-cis bond content of 40% by weight or more in 1,3-butadiene unit. A block copolymer comprising (A) and a polyisoprene-based block (B) is blended, and the content of the block copolymer (iii) is 100 parts by weight in total of the components (i) and (ii). The rubber composition is provided in an amount of 0.5 to 25 parts by weight based on the weight of the rubber composition.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Polyisoprene rubber (i) Polyisoprene rubber used in the present invention
Is a polymer having 2-methyl-1,3-butadiene (isoprene) unit as a main component.
It may be a synthetic polyisoprene rubber. The content of isoprene units in the polymer is preferably 60% by weight or more, more preferably 90% by weight or more, and particularly preferably 100% by weight. When the isoprene unit content is low, the mechanical strength and the fatigue resistance are poor.

Other monomer units that can constitute the polyisoprene rubber (i) include 1,3-butadiene and
2,3-dimethyl-1,3-butadiene, 2-chloro-
1,3-butadiene, 1,3-pentadiene, 1,3-
Conjugated dienes other than isoprene such as hexadiene; styrene, o-methylstyrene, p-methylstyrene, m-
Methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene,
aromatic vinyls such as p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene and vinylnaphthalene; olefins such as ethylene, propylene and 1-butene; cyclopentene and 2-norbornene Cyclic olefin; 1,5-hexadiene, 1,
Non-conjugated dienes such as 6-heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-norbornene; acrylates or methacrylates such as methyl acrylate and methyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide, And a monomer unit composed of a monomer such as methacrylamide. Among them, 1,3-butadiene and styrene are preferred, and 1,3-butadiene is more preferred. It is preferable that these monomer units are randomly bonded in the polyisoprene rubber (i).

The 1,4-cis bond content in the isoprene unit of the polyisoprene rubber (i) is preferably at least 50% by weight, more preferably at least 80% by weight, particularly preferably at least 90% by weight. When the 1,4-cis bond content is low,
Poor mechanical strength and fatigue resistance.

The Mooney viscosity (ML) of polyisoprene (i)
_{1 + 4} , 100 ° C.) is preferably from 10 to 200,
To 150 are more preferable, and 30 to 120 are particularly preferable. If the Mooney viscosity is low, the mechanical strength and low heat build-up are inferior, and if it is high, the processability is inferior.

When the polyisoprene rubber (i) is a synthetic one, it can be produced by using a Ziegler polymerization catalyst, an alkyllithium polymerization catalyst or a radical polymerization catalyst containing titanium or the like as a catalyst component.
Among them, those produced with a Ziegler-based polymerization catalyst containing titanium are preferable because the 1,4-cis bond content in the isoprene unit can be increased.

[0014] polybutadiene rubber used in the polybutadiene rubber present invention (ii)
Is a polymer mainly composed of 1,3-butadiene units, and the content of 1,3-butadiene units is preferably 60% by weight or more, more preferably 90% by weight or more, and 100% by weight.
Is particularly preferred. When the 1,3-butadiene unit content is low, abrasion resistance and low heat generation are inferior.

Other monomer units which can constitute the polybutadiene rubber (ii) include 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3-butadiene,
Conjugated dienes other than 1,3-butadiene such as 2-chloro-1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene; styrene, o-methylstyrene, p-
Methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene,
aromatic vinyl such as p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene, vinylnaphthalene; ethylene;
Olefins such as propylene and 1-butene; cyclic olefins such as cyclopentene and 2-norbornene;
-Hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2
-Non-conjugated dienes such as norbornene; acrylates or methacrylates such as methyl acrylate and methyl methacrylate; and monomer units composed of monomers such as acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide. Above all,
2-Methyl-1,3-butadiene and styrene are preferred, and 2-methyl-1,3-butadiene is more preferred. These monomer units are a polybutadiene rubber (i
It is preferred that they are randomly bonded in i).

1,3-polybutadiene rubber (ii)
The 1,4-cis bond content in the butadiene unit is preferably 50% by weight or more, more preferably 80% by weight or more, and 90% by weight or more.
% By weight or more is particularly preferred. When the 1,4-cis bond content is low, the mechanical strength and the fatigue resistance are poor.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the polybutadiene rubber (ii) is preferably from 10 to 150, more preferably from 20 to 120, and particularly preferably from 30 to 100. If the Mooney viscosity is low, the mechanical strength and low heat build-up are inferior, and if it is high, the processability is inferior.

The polybutadiene rubber (ii) can be produced by using a Ziegler polymerization catalyst, an alkyllithium polymerization catalyst or a radical polymerization catalyst containing titanium, nickel, neodymium or the like as a catalyst component. Above all,
Since the 1,4-cis bond content in the 1,3-butadiene unit can be increased, it is preferable to produce with a Ziegler-based polymerization catalyst.

(Iii) Block copolymer The block copolymer used in the present invention (iii)
Is a polybutadiene block (A) having a 1,4-cis bond content of 40% by weight or more in a 1,3-butadiene unit.
And at least one polyisoprene block (B).

The 1,3-butadiene unit content in the block (A) is preferably at least 60% by weight, more preferably at least 90% by weight, particularly preferably 100% by weight. This one
When the 3-butadiene unit content is low, the mechanical strength and the abrasion resistance are poor. Further, it is preferable from the viewpoint of mechanical strength that the 1,3-butadiene unit content in the polybutadiene-based block (A) and the polybutadiene-based rubber (ii) be as similar as possible.
-The difference in butadiene unit content is preferably 10% by weight or less, more preferably 5% by weight or less.

The 1,4-cis bond content in the 1,3-butadiene unit in the polybutadiene-based block (A) is 4
It is at least 0% by weight, preferably at least 60% by weight, more preferably at least 80% by weight, particularly preferably at least 90% by weight. When this content is low, the mechanical strength and the fatigue resistance are poor. Further, the difference between the 1,4-cis bond content in the 1,3-butadiene unit in the polybutadiene-based block (A) and the polybutadiene-based rubber (ii) is 20% by weight or less, more preferably 10% by weight, in terms of mechanical strength. % By weight or less is preferred.

Examples of other monomer units that can constitute the polybutadiene block (A) include the same units as those in the case of the polybutadiene rubber (ii).
2-Methyl-1,3-butadiene is preferred. It is preferable that these monomer units are randomly bonded in the polybutadiene-based block (A).

The isoprene unit content in the polyisoprene block (B) is preferably at least 60% by weight, more preferably at least 90% by weight, and particularly preferably 100% by weight.
When the isoprene unit content is low, the mechanical strength and the fatigue resistance are poor. Further, it is preferable from the viewpoint of mechanical strength that the isoprene unit content in the polyisoprene-based block (B) and the polyisoprene-based rubber (i) be as similar as possible. From this viewpoint, the difference in the isoprene unit content in both is preferable. It is preferably at most 10% by weight, more preferably at most 5% by weight.

Examples of other monomer units that can constitute the polyisoprene-based block (B) include the same units as in the case of the polyisoprene-based rubber (i).
1,3-butadiene is preferred. It is preferable that these monomer units are randomly bonded in the polyisoprene-based block (B).

The 1,4-cis bond content in the isoprene unit in the polyisoprene block (B) is 60% by weight.
Or more, preferably 80% by weight or more, and 85% by weight or more.
% By weight or more is particularly preferred. When the 1,4-cis bond content is low, the mechanical strength and fatigue resistance are poor. The difference between the 1,4-cis bond content in the isoprene unit of the polyisoprene-based block (B) and the polyisoprene-based rubber (i) is 30% by weight or less, more preferably 20% by weight, in terms of excellent mechanical strength. % Or less is preferable.

The block copolymer (iii) may have at least one polybutadiene block (A) and at least one polyisoprene block (B).
It may be coupled with a coupling agent having at least two reaction sites. As specific examples, (A)-(B), (A)-(B)-(A), (B)
And (A)-(B) and (A)-(B)-(A)-(B). Among them, only one polybutadiene-based block (A) and only one (A) having a polyisoprene-based block (B)
(B) Block copolymers are preferred.

The block copolymer (iii) may be modified with a terminal modifier by a method described later, and by introducing a polar group by this method, the abrasion resistance and low heat build-up are reduced. More improved.

The ratio (weight ratio) between the polybutadiene block (A) and the polyisoprene block (B) is as follows:
(A): (B) is preferably from 10:90 to 90:10, more preferably from 20:80 to 80:20, and particularly preferably from 30:70 to 70:30.

The weight average molecular weight (Mw) of the block copolymer (iii) measured by gel permeation chromatography is 10,000 to 2,000,000.
00 is preferable, 50,000 to 1,500,000 is more preferable, and 100,000 to 1,000,000 is particularly preferable. If the weight average molecular weight is too small or too large, the wear resistance is poor. In addition, the weight average molecular weight (M
w) and the number average molecular weight (Mn) ratio (Mw / Mn) is
2.0 or less is preferable, 1.7 or less is more preferable,
Particularly preferred is 1.4 or less. If this value is large, the mechanical strength and fatigue resistance are inferior. Conversely, if it is smaller than 1.1, it is difficult to manufacture.

The block copolymer (iii) used in the present invention can be produced, for example, by the method described in JP-A-2000-154221. The polymerization catalyst comprises (a) a transition metal compound belonging to Group 4 of the periodic table having a cyclopentadienyl skeleton represented by the following general formula 1 and (ii) an organic aluminum oxy compound.

General formula 1:

Embedded image

(Wherein M is a transition metal of Group 4 of the periodic table, X
Is a hydrogen atom, a halogen, a hydrocarbon group having 1 to 12 carbon atoms,
A hydrocarbon oxy group having 1 to 12 carbon atoms, or 1 to 1 carbon atoms
An amino group which may be substituted with 12 hydrocarbon groups,
They may be different from each other, and may form a cyclic structure by bonding any one of X to the cyclopentadiene ring structure with or without a crosslinking group,
p is 2 or 3, Q is an organic group, and may combine with a cyclopentadiene ring structure to form a cyclic structure, and when Q is two or more, they may be different from each other. , M is an integer of 0 to 5. That is, the transition metal compound represented by the general formula 1 is a so-called half metallocene having only one cyclopentadienyl group or a plurality of fused cyclic substituents such as an indenyl group and a fluorenyl group as ligands. Compound. The transition metal of Group 4 of the periodic table (M in the formula) is
Preferably titanium, zirconium or hafnium, more preferably titanium.

Specific examples of the transition metal compound of Group 4 of the periodic table (a) include methylcyclopentadienyltitanium trichloride, trimethylsilylcyclopentadienyltitanium trichloride, and t-butylcyclopentadienyltitanium trichloride. , triphenylmethyl cyclopentadienyl titanium trichloride, adamantyl cyclopentadienyl titanium trichloride, (2-methoxyethyl) cyclopentadienyl titanium trichloride (MeOCH ₂ CH ₂ Cp
TiCl _3), [2- (t- butoxy) ethyl] cyclopentadienyl titanium trichloride (t-BuO
CH ₂ CH ₂ CpTiCl ₂ ), phenoxyethylcyclopentadienyltitanium trichloride (PhOCH)
_{2 CH 2 CpTiCl 3), 2-} (2- methoxyethoxy) ethyl cyclopentadienyl titanium trichloride _{(MeOCH 2 CH 2 OCH 2 CH} 2 CpTiC
l ₃ ), methoxycarbonylmethylcyclopentadienyltitanium trichloride (MeO (CO) CH ₂ C
pTiCl _3), t- butoxycarbonyl methylcyclopentadienyl titanium trichloride (t-BuO
(CO) CH ₂ CpTiCl ₃ ), phenoxycarbonylmethylcyclopentadienyltitanium trichloride (PhO (CO) CH ₂ CpTiCl ₃ ), 2- (N, N
-Dimethylamino) ethylcyclopentadienyltitanium trichloride (Me ₂ NCH ₂ CH ₂ CpTiC
l ₃ ), 2- (N, N-diethylamino) ethylcyclopentadienyltitanium trichloride (Et ₂ NC
H ₂ CH ₂ CpTiCl ₃ ), 2- (N, N-di-i-propylamino) ethylcyclopentadienyltitanium trichloride (i-Pr ₂ NCH ₂ CH ₂ CpTiC)
l ₃₎ and the like, with preference given to t- butyl cyclopentadienyl titanium trichloride is preferred.

Specific examples of the organic aluminum oxy compound (b) include methylaluminoxane, ethylaluminoxane, propylaluminoxane, butylaluminoxane, chloroaluminoxane and the like, and among them, methylaluminoxane is preferable. The organic aluminum oxy compound (b) can be synthesized by reacting an organic aluminum metal compound with water.

Examples of the organoaluminum metal compound include: organoaluminum compounds such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum; dimethylaluminum chloride, diethylaluminum chloride, sesquiethylaluminum chloride, ethylaluminum Organic aluminum halides such as dichloride; and organic aluminum hydride compounds such as diethyl aluminum hydride and sesquiethyl aluminum hydride. Also, a mixture of these can be used.

The polymerization catalysts further include the first and second compounds of the periodic table.
An organometallic compound (C) comprising a Group 2, 12, or 13 metal may be added. Specific examples of the organometallic compound (c) include, for example, organolithium compounds such as methyllithium, butyllithium, and phenyllithium; organomagnesium compounds such as dibutylmagnesium; trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, Organic aluminum compounds such as octyl aluminum; organic magnesium halides such as ethyl magnesium chloride and butyl magnesium chloride; organic aluminum halides such as dimethyl aluminum chloride, diethyl aluminum chloride, sesquiethyl aluminum chloride and ethyl aluminum dichloride; diethyl aluminum hydride, sesqui Hydrogenation of ethyl aluminum hydride Machine aluminum compounds and the like. Of these, trialkylaluminum compounds having an alkyl group having 1 to 5 carbon atoms, such as trimethylaluminum, triethylaluminum, and triisobutylaluminum, are preferable, and trimethylaluminum is more preferable.

(Method for producing block copolymer (iii)) The block copolymer (ii) used in the present invention
The production method i) includes at least a step of forming a polybutadiene-based block (A) and a step of forming a polyisoprene-based block (B). This order may be performed first, but it is preferable to perform the step of forming the block (A) first. In that case, in the presence of a polymerization catalyst, a monomer capable of forming the block (A) is polymerized, and then a monomer capable of forming the block (B) is polymerized to form a block copolymer (iii) ) Can be manufactured.

The amounts of the respective components of the polymerization catalyst used are preferably prepared as follows. The molar ratio of the organoaluminum oxy compound (b) / transition metal compound (a) ((b) is calculated in terms of aluminum equivalent) is preferably from 10 to 10,000, and from 50 to 10,000.
5,000 is more preferable, and 100 to 3,000 is particularly preferable. Even if the amount of the organic aluminum oxy compound (b) used is small or large, the polymerization activity is reduced. Further, when an organometallic compound (c) comprising a metal of Groups 1, 2, 12, or 13 of the periodic table is added, the molar ratio of the organometallic compound (c) / transition metal compound (a) is 0.1 to 1
It is preferably 000, more preferably 1 to 1,000.

The amount of the polymerization catalyst used in the method for producing the block copolymer (iii) is a molar amount of the transition metal compound (a) to 1 mol of the monomer, and is preferably 0.01 to 5 mol.
0 mmol, more preferably 0.05-10 mmol,
Particularly preferably, it is 0.1 to 5 mmol. When the amount of the polymerization catalyst used is small, the polymerization activity decreases, and when it is large, the molecular weight of the obtained polymer decreases.

In the method for producing the block copolymer (iii), the transition metal compound (a) and the organoaluminum oxy compound (b) may be separately brought into contact with the monomer, respectively. It is preferable that the monomer is brought into contact with the monomer after having been brought into contact in advance under a condition satisfying the formula β. Formula α: 0 ≦ T ≦ 50 Formula β: 0.5 ≦ t ≦ 2000exp (−0.0921
T)

That is, the contact temperature (T, ° C.) between the transition metal compound (a) and the organoaluminum oxy compound (b)
Is preferably from 0 to 50 ° C, more preferably from 10 to 40 ° C.
° C, more preferably 15 to 35 ° C. When the contact temperature is low, the Mw / Mn of the obtained polymer increases, and when it is high, the polymerization activity decreases.

The contact time (t, min) between the transition metal compound (a) and the organoaluminum oxy compound (b) preferably satisfies 0.5 ≦ t ≦ 2000 exp (−0.0921T). The time that satisfies ≦ t ≦ 1000exp (−0.0921T) is more preferable. When the contact time is short, the Mw / Mn of the obtained polymer increases, and when it is long, the polymerization activity decreases.

The transition metal compound (a) and the organoaluminum oxy compound (b) can be used in the form of either a solution or a slurry, respectively. Is preferred. Solvents used for preparing solutions or slurries include butane, pentane, hexane, heptane, octane, cyclohexane, mineral oil, hydrocarbon solvents such as benzene, toluene, xylene, or chloroform, methylene chloride, dichloroethane, chlorobenzene,
-Chlorotoluene, 4-chlorotoluene, 2,6-dichlorotoluene, 1,2,4-trichlorobenzene, 2-
Halogenated hydrocarbon solvents such as fluorotoluene and 4-fluorotoluene. These solvents may be used as a mixture of two or more kinds. Of these, aromatic hydrocarbons and halogenated aromatic hydrocarbons are preferred.

The polymerization method which can be employed in the method for producing the block copolymer (iii) is not particularly limited, but includes a bulk polymerization method, a solution polymerization method and a slurry polymerization method in an inert solvent, and a gas-phase stirring tank. A gas-phase polymerization method using a gas-phase fluidized bed is exemplified. Among these methods, the solution polymerization method is preferable because the molecular weight distribution can be narrowed. Further, both a batch polymerization method and a continuous polymerization method can be employed.

The inert solvent used in the solution polymerization is not particularly limited, but may be a hydrocarbon solvent such as butane, pentane, hexane, heptane, octane, cyclohexane, mineral oil, benzene, toluene, xylene, or chloroform, methylene chloride. And halogenated hydrocarbon solvents such as dichloroethane, chlorobenzene, 2-chlorotoluene, 4-chlorotoluene, 2,6-dichlorotoluene, 1,2,4-trichlorobenzene, 2-fluorotoluene and 4-fluorotoluene. These solvents may be used as a mixture of two or more kinds. Among these, aromatic hydrocarbon solvents and halogenated aromatic hydrocarbon solvents are preferred.

The polymerization temperature in the method for producing the block copolymer (iii) is not particularly limited, but is preferably −
The temperature is from 100 ° C to + 100 ° C, more preferably from -60 ° C to 30 ° C, particularly preferably from -40 ° C to -5 ° C. When the polymerization temperature is high, Mw / Mn of the obtained polymer increases. Further, a polymerization reaction at an extremely low temperature such as -100 ° C or lower is not preferable from the viewpoint of production cost. The polymerization time is about 1 minute to 50 hours, and the polymerization pressure is 1 to 30 kg / c.
m ² .

In the method for producing the block copolymer (iii), a chain transfer agent can be added to adjust the molecular weight of the polymer. As the chain transfer agent, 1,4
-Those conventionally used in the production of cis-polybutadiene rubber can be similarly used, and specific examples thereof include 1,
Allenes such as 2-butadiene; cyclic dienes such as cyclooctadiene; hydrogen;

Since the polymerization reaction proceeds in a living manner, before stopping the polymerization reaction, a reagent capable of reacting with a living polymer having a catalytic metal at a molecular terminal is added to the polymerization system and reacted with the living polymer. be able to. Usually, monofunctional reagents are called terminal modifiers, and polyfunctional reagents are called coupling agents. In the case of a terminal modifier, it forms a structure bonded to the end of the living polymer, and in the case of a coupling agent, a structure formed by bonding two or more living polymers. They can be used in combination.

The terminal modifier is not particularly restricted but includes, for example, epoxy compounds such as ethylene oxide and styrene oxide; isocyanate compounds such as phenyl isocyanate and butyl isocyanate;
4'-bis (diethylamino) benzophenone, 4,
N-substituted aminoketones such as 4'-bis (diphenylamino) benzophenone; N-substituted benzaldehydes such as 4-dimethylaminobenzaldehyde and 4-diphenylaminobenzaldehyde; N, N-diethylacetamide, N, N-dimethylaminoacetamide Carboxylic acid amides such as N-methyl-2-pyrrolidone, N
N-substituted pyrrolidones such as -phenyl-2-pyrrolidone; and the like. In the case of a terminal modifying agent, it may cause a structural change when bound to the terminal of the living polymer and further react with another terminal of the living polymer to act as if it were a coupling agent.

The coupling agent is not particularly restricted but includes, for example, silicon halides containing at least two halogen atoms such as silicon tetrachloride, silicon tetrabromide, trichloromethylsilane, hexachlorodisilane; tetramethoxysilane; Organosilicon compounds containing two or more alkoxy groups having 1 to 8 carbon atoms, such as tetraethoxysilane, methyltrimethoxysilane, and phenyltrimethoxysilane; at least two compounds such as tin tetrachloride, tin tetrabromide, and dimethyltin dichloride; And a halogenated tin compound containing a halogen atom.

To the block copolymer (iii) used in the present invention, an appropriate amount of an antioxidant may be added in order to prevent the polymer from deteriorating during removal or storage. Antioxidants include, for example, 2,6-di-t-butyl-
4-methylphenol, 2,6-di-t-butyl-4-
A phenolic antioxidant such as isobutylphenol;
Sulfur-based antioxidants such as dilaurylthiodipropionate and distearylthiodipropionate; tris (nonylphenyl) phosphite, tris (2,4-di-
phosphorus-based anti-aging agents such as t-butylphenyl) phosphite; amine-based anti-aging agents such as phenyl-α-naphthylamine and p-isopropoxydiphenylamine. These antioxidants may be used as a mixture of two or more.

Usually, the polymerization reaction is stopped at a predetermined time.
It is carried out by adding a polymerization terminator to the polymerization system.
Examples of the polymerization terminator include water; alcohols such as methanol, ethanol, propanol, butanol and isobutanol; inorganic acids such as hydrochloric acid; and organic acids such as citric acid, versatic acid and dodecylbenzenesulfonic acid. These polymerization terminators may be used as a mixture of two or more.

The method of recovering the polymer after the termination of the polymerization reaction may be a conventional method, such as a steam stripping method or a method of precipitating the polymer in a poor solvent.

Rubber Composition In the present invention, the block copolymer (iii) is added in an amount of 0.5 to 25 based on 100 parts by weight of the total of the polyisoprene rubber (i) and the polybutadiene rubber (ii).
Parts by weight, preferably 1 to 20 parts by weight, particularly preferably 3 parts by weight.
-10 parts by weight. If the content of the block copolymer (iii) is too low, the effect of the present invention is not exhibited, and if it is too high, the mechanical strength and the low heat build-up are poor.

The use ratio of the polyisoprene rubber (i) and the polybutadiene rubber (ii) is 100
The amount of (i) is usually 10 to 90 parts by weight, preferably 30 to 85 parts by weight, more preferably 50 parts by weight based on parts by weight.
８０80 parts by weight. If the amount is small, the mechanical strength and the fatigue resistance decrease, and if it is high, the abrasion resistance decreases.

The rubber composition of the present invention may contain other rubbers other than the components (i) to (iii) as long as the effects of the present invention are not impaired. Other rubbers include
Styrene-butadiene copolymer rubber, acrylonitrile-
Conjugated diene rubbers such as butadiene copolymer rubber and chloroprene rubber; ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, butyl rubber, acrylic rubber, ethylene-acryl copolymer rubber, chlorosulfonated polyethylene, chlorinated polyethylene Olefin rubbers such as epichlorohydrin rubber and silicone rubber. Among them, conjugated diene rubbers such as styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and chloroprene rubber are preferable, and styrene-butadiene copolymer rubber is more preferable. When other rubber is compounded, the compounding amount is usually 70 parts by weight or less, preferably 50 parts by weight or less, more preferably 100 parts by weight based on 100 parts by weight of the total of components (i) and (ii). Is 30 parts by weight or less.

The rubber composition of the present invention can contain a reinforcing material such as carbon black or silica, and if necessary, other compounding agents. As the carbon black, for example, furnace black, acetylene black, thermal black, channel black, graphite, and the like can be used. Furnace black is particularly preferable, and specific examples thereof include SAF, ISAF,
ISAF-HS, ISAF-LS, IISAF-HS,
Various grades such as HAF, HAF-HS, HAF-LS, FEF and the like can be mentioned. These carbon blacks can be used alone or in combination of two or more.

The nitrogen adsorption specific surface area of carbon black (N
The lower limit of ₂ SA) is preferably 5 to 200 m ² / g, more preferably 50 to 150 m ² / g, particularly preferably 80
１３０130 m ² / g. When the nitrogen adsorption specific surface area is in this range, the mechanical strength and the abrasion resistance are excellent, which is preferable.

The lower limit of the amount of DBP adsorbed by carbon black is preferably 5 to 300 ml / 100 g, more preferably 50 to 200 ml / 100 g, and particularly preferably 80 to 160 ml / 100 g. When the DBP adsorption amount is in this range, the mechanical strength and the wear resistance are excellent, which is preferable.

Further, as carbon black, the adsorption (CTAB) specific surface area of cetyltrimethylammonium bromide disclosed in JP-A-5-230290 is 110 to 170 m ² / g, and 24,000 ps.
DBP (24
(M4DBP) High-structure carbon black having an oil absorption of 110 to 130 ml / 100 g is more preferably used because of its excellent abrasion resistance.

As the silica, for example, dry white carbon, wet white carbon, colloidal silica, precipitated silica disclosed in JP-A-62-262838, and the like are preferably used. Particularly preferred is a wet-process white carbon having as a main component. These silicas can be used alone or in combination of two or more.

When the rubber composition of the present invention contains silica as a reinforcing agent, low heat buildup and abrasion resistance are further improved by adding a silane coupling agent. The silane coupling agent is not particularly limited. For example, vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane ,
Bis (3- (triethoxysilyl) propyl) tetrasulfide, bis (3- (triethoxysilyl) propyl) disulfide and the like, and γ-trimethoxysilylpropyldimethylthiocarbamyl described in JP-A-6-248116 Examples thereof include tetrasulfides such as tetrasulfide and γ-trimethoxysilylpropylbenzothiazyltetrasulfide. Since scorch during kneading can be avoided, the silane coupling agent is preferably one containing four or less sulfur in one molecule.

These silane coupling agents can be used alone or in combination of two or more. The lower limit of the amount of the silane coupling agent relative to 100 parts by weight of silica is preferably 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight.

The lower limit of the nitrogen adsorption specific surface area (BET method) of silica is preferably from 50 to 400 m ² / g, more preferably from 100 to 220 m ² / g, particularly preferably from 120 to 220 m ² / g.
190 m ² / g. When it is in this range, it is preferable because it has excellent mechanical strength, abrasion resistance, low heat generation, and the like. Note that the nitrogen adsorption specific surface area is ASTM D303
It is a value measured by the BET method according to 7-81.

The amount of the reinforcing material is preferably 10 to 200 parts by weight, more preferably 20 to 150 parts by weight, particularly preferably 30 to 100 parts by weight, based on 100 parts by weight of the total rubber component.
Parts by weight.

When silica and carbon black are used in combination as a reinforcing material, the mixing ratio is appropriately selected according to the use and purpose.
10: 90-99: 1 is preferred, and 30: 70-95:
5 is more preferable, and 40:60 to 90:10 is particularly preferable.

The rubber composition of the present invention may contain, in addition to the above components, a crosslinking agent, a crosslinking accelerator, a crosslinking activator, an antioxidant, an activator, a process oil, a plasticizer, a lubricant, a filler according to a conventional method. The compounding agents other than the reinforcing material such as the above can be contained in necessary amounts.

Examples of the crosslinking agent include sulfur such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur and highly dispersible sulfur; sulfur halide such as sulfur monochloride and sulfur dichloride;
Organic peroxides such as dicumyl peroxide and ditert-butyl peroxide; p-quinonedioxime, p,
quinone dioximes such as p'-dibenzoylquinone dioxime; organic polyamine compounds such as triethylenetetramine, hexamethylenediaminecarbamate and 4,4'-methylenebis-o-chloroaniline; alkylphenol resins having a methylol group; Among these, sulfur is preferred, and powdered sulfur is particularly preferred. These crosslinking agents are used alone or in combination of two or more. The amount of the crosslinking agent is usually 0.1 to 15 parts by weight, preferably 0.3 to 10 parts by weight, based on 100 parts by weight of all rubber components.

Examples of the crosslinking accelerator include N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N- Sulfenamide-based cross-linking accelerators such as oxyethylene-2-benzothiazolesulfenamide and N, N'-diisopropyl-2-benzothiazolesulfenamide; guanidines such as diphenylguanidine, diol-tolyl guanidine, and ortho-tolyl biguanidine Thiourea-based crosslinking accelerators such as diethylthiourea; thiazole-based crosslinking accelerators such as 2-mercaptobenzothiazole, dibenzothiazyldisulfide, and 2-mercaptobenzothiazole zinc salt; tetramethylthiuram monosulfide Thiuram-based cross-linking accelerators such as dimethyl and tetramethylthiuram disulfide; dithiocarbamic acid-based cross-linking accelerators such as sodium dimethyldithiocarbamate and zinc diethyldithiocarbamate; xanthogenic acids such as sodium isopropylxanthate, zinc isopropylxanthate and zinc butylxanthate Crosslinking accelerator; and the like. These crosslinking accelerators may be used alone or in combination of two or more, but those containing a sulfenamide-based crosslinking accelerator are particularly preferred. All rubber components 100
The amount of the crosslinking accelerator is usually 0.1 to 10 parts by weight.
It is 10 parts by weight, preferably 0.5 to 5 parts by weight.

As the crosslinking activator, for example, higher fatty acids such as stearic acid, zinc oxide and the like can be used. As zinc oxide, those having a high surface activity and a particle size of 5 μm or less are preferably used.
Active zinc white of 2 μm and zinc white of 0.3 to 1 μm can be exemplified. Zinc oxide may be surface-treated with an amine-based dispersant or wetting agent. These crosslinking activators can be used alone or in combination of two or more. The mixing ratio of the crosslinking activator is
It is appropriately selected depending on the type. For example, the higher fatty acid is preferably used in an amount of 0.1 to 100 parts by weight of the total rubber component.
1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, zinc oxide is preferably used at 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight. Is done.

Further, for example, diethylene glycol,
Activators such as polyethylene glycol and silicone oil; fillers such as calcium carbonate, talc and clay; waxes and the like may be added.

The rubber composition of the present invention can be obtained by kneading each component according to a conventional method. For example, a rubber component and a desired compounding agent are mixed at 80 to 200 ° C., preferably
Mix at 40-180 ° C, 100 ° C or less, preferably 8 ° C
After cooling to 0 ° C. or lower, a rubber composition can be obtained by mixing the mixture with a crosslinking agent and a crosslinking accelerator for about 0.5 to 30 minutes.

The rubber composition of the present invention is usually used after crosslinking. The crosslinking method is not particularly limited, and may be selected according to the shape, size, and the like of the crosslinked product. The mold may be filled with the crosslinkable rubber composition and heated to carry out crosslinking at the same time as molding, or a previously molded uncrosslinked rubber composition may be heated to carry out crosslinking. The crosslinking temperature is usually from 120 to 2
00 ° C, preferably 140 to 200 ° C, and the crosslinking time is usually about 1 to 120 minutes.

The rubber crosslinked product of the present invention thus obtained can be used, for example, in components such as tires, cable coating agents, hoses, transmission belts, conveyor belts, roll covers, shoe soles, sealing rings, and vibration-proof rubbers. And particularly suitably used for tire treads.

[0075]

EXAMPLES The present invention will be specifically described below with reference to examples. Parts and percentages are by weight unless otherwise specified. According to the method described in JP manufacturing JP 2000-154221 (Example 1) block copolymer (I), was synthesized t- butylcyclopentadienyl trichloro titanium (t-BuCpTiCl _3). Methylaluminoxane (PMAO-S, manufactured by Tosoh Akzo) 20
In a 0 mmol toluene solution, t-BuCpTiCl ₃
A 0.2 mmol toluene solution was added dropwise,
Aged for minutes. Under a nitrogen atmosphere, 639 g of toluene and 18.0 butadiene were placed in a sealed pressure-resistant glass flask.
g and cooled to -15 ° C. The aged catalyst was added to this ampoule and polymerized at -15 ° C for 4 hours. After sampling 18.2 g of the polymerization solution for analysis, it was rapidly cooled to -25 ° C to constant temperature. 30.7 g of isoprene was added to the polymerization solution for polymerization, and after 4 hours, methanol was added to stop the polymerization reaction. The polymerization solution and the sampling solution were subjected to precipitation of a polymer by pouring into acidic methanol, dissolution in toluene, removal of ash by centrifugation, precipitation of a polymer by pouring into acidic methanol, and drying. Polymer (I) was obtained.

For GPC analysis, THF was used as an eluent,
Columns G7000, G5000, G4 manufactured by Tosoh Corporation
000 were connected as a detector using a differential refractive index detector (RI).

For NMR analysis, LA600NM manufactured by JEOL Ltd.
The measurement was performed at room temperature on a deuterated chloroform solution of the sample using an R apparatus. The microstructure of the butadiene portion in the polymer was determined by ¹ H-NMR analysis to show 1,4-bonds (5.4-bonds).
5.6 ppm) and 1,2-bond (5.0-5.1 pp)
m) was determined and the ratio of cis to trans (32.7 ppm) was determined from ¹³ C-NMR analysis. The microstructure of the isoprene moiety in the polymer is ¹³ C-
Methyl carbon signal in the NMR spectrum (cis: 2
3.3 ppm, transformer: 15.9 ppm, 3,4: 1
(8.6 ppm, 1, 2: 13.1 ppm). Table 1 shows the results of the polymerization and analysis.

[0078]

[Table 1]

The yield in the first stage living polymerization of butadiene is 100%. The cis content of the obtained butadiene block was 92%, and the molecular weight distribution was 1.11. The molecular weight distribution of the finally obtained block copolymer (I) is narrow at 1.25, and the isoprene content calculated from the ¹ H-NMR spectrum is 52%. Also, ¹³ C-N
1,4 in isoprene unit calculated from MR spectrum
The cis content is 85%;

Rubber composition 70 parts of natural rubber (RSS # 3), polybutadiene (B
R1220: Nippon Zeon Co., Ltd.) 26 parts, block copolymer (I) 4 parts, carbon black (Seast 6:
50 parts of Tokai Carbon Co., Ltd., 3 parts of zinc oxide, 1 part of stearic acid and an antioxidant (Santofflex 1)
3: Monsanto Co.) 1 part 1 with Banbury mixer
Kneaded at 00 ° C for 5 minutes, and then the resulting kneaded material, sulfur 2
Parts and 1.5 parts of a crosslinking accelerator (Santocure NS: manufactured by Monsanto Co.) were kneaded with an open roll machine at 50 ° C. for 4 minutes to obtain a rubber composition. The obtained rubber composition was mixed with 160
Vulcanized rubber test pieces were prepared by press vulcanization at 12 ° C. for 12 minutes, and the following characteristic values were measured. Table 2 shows the results.

(1) Tensile test: According to JIS K6251. (2) Fatigue resistance test: According to JIS K6260. It is indicated by an index with Comparative Example 1 being 100. The larger the value, the better the fatigue resistance. (3) Abrasion resistance test: Measured using a pico abrasion tester according to JIS K 6264. It is indicated by an index with Comparative Example 1 being 100. . The larger the value, the better the wear resistance. (4) Low heat build-up test: RDA-I manufactured by Rheometrics
Using I, tan δ at 0.5% twist, 20 Hz, 0 ° C. and 60 ° C. was measured, and tan δ (0 ° C.) / Tan δ (6
0 ° C.). When this value is large, the heat generation is excellent. The index is shown as an index with Comparative Example 1 being 100. The larger the value, the better the low heat buildup.

[0082]

[Table 2]

(Comparative Example 1) A block copolymer comprising a poly (butadiene-styrene) block having the properties shown in Table 1 and a polyisoprene block was prepared by a solution polymerization method using n-butyllithium as a polymerization initiator. II) was prepared. A rubber composition was prepared in the same manner as in Example 1, except that the block copolymer (II) was used in place of the block copolymer (I). Table 2 shows the results.

Comparative Example 2 A block copolymer (III) comprising a polybutadiene block and a polyisoprene block having the properties shown in Table 1 was produced by a solution polymerization method using n-butyllithium as a polymerization initiator. . A rubber composition was prepared in the same manner as in Example 1, except that the block copolymer (III) was used in place of the block copolymer (I). Table 2 shows the results.

Comparative Example 3 In the preparation of a rubber composition,
Without mixing the block copolymer, polybutadiene (BR
1220: manufactured by Zeon Corporation) from 26 parts by weight to 3
The procedure was performed in the same manner as in Example 1 except that the amount was changed to 0 parts by weight. Table 2 shows the results.

As described above, the rubber composition containing the block copolymer (I) comprising the polybutadiene block having a high 1,4-cis bond content in the 1,3-butadiene unit and the polyisoprene block in Example 1 was obtained. Excellent in mechanical strength, fatigue resistance, abrasion resistance and low heat generation.

[0087]

According to the present invention, a rubber composition having excellent mechanical strength, fatigue resistance, abrasion resistance and low heat generation is provided.

Claims (1)

[Claims] 1. (i) a polyisoprene rubber, (ii)
A block copolymer comprising a polybutadiene rubber and (iii) a polybutadiene block (A) having a 1,4-cis bond content of 40% by weight or more in a 1,3-butadiene unit and a polyisoprene block (B). A rubber composition prepared by blending a coalesced substance and having a block copolymer (iii) content of 0.5 to 25 parts by weight based on 100 parts by weight of the total of components (i) and (ii).