JPS6227443A - Rubber composition for tire - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. for tire, which has improved wet skid characteristics, rolling friction resistance and tensile strength, containing a conjugated diene copolymer obtd. by reacting a conjugated diene compd., an arom. vinyl compd. and an isothiocyanate. CONSTITUTION:A rubber compsn. contains at least 30wt% conjugated copolymer having a polymerized vinyl content (in the diene moiety) of 20% or above, an arom. vinyl compd. content of 10wt% or above and a glass transition temp. of -70 deg.C or above, obtd. by copolymerizing a conjugated diene and an arom. vinyl compd. in the presence of a lithium polymn. initiator and reacting the polymerizable terminal of the resulting polymer with an isothiocyanate compd. 10-70pts.wt. said rubber comps. is blended with 100pts.wt. natural rubber to thereby improve the tensile strength and processability. If desired, extender oil such as arom. process oil or naphthenic process oil, other additives and a vulcanizing agent may be added.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a rubber composition of a vulcanizate that has excellent wet skid properties, rolling friction resistance properties, and tensile strength, and has good processability.

b. Conventional technology In recent years, with the demand for safety and low fuel consumption for automobiles, conjugated diene-based rubber materials with excellent wet skid properties, fuel economy properties, and wear properties have been used as rubber materials for tires, especially tire trends. Polymers became sought after.

Conventionally, these conjugated diene polymers were
Conjugated diene compounds are prepared using an organolithium initiator in a hydrocarbon solvent, as described in US Pat. or by copolymerizing a conjugated diene compound and a vinyl aromatic compound, followed by reaction with a tin halide compound or an alkenyltin compound.

C4 Problems to be Solved by the Invention However, since the polymer ends are composed of carbon-tin bonds, the above polymers are susceptible to acidic substances such as inorganic acids, organic carboxylic acids, and Lewis acids, organic phosphorus compounds, and even organic sulfur compounds. The carbon-tin bond at the end of the polymer is easily broken due to chemical reactions with other substances, hydrolysis reactions under strong acids, strong alkalis, etc., resulting in deterioration of physical properties, which limits the types of rubber additives that can be used. There is.

In order to solve the problems of the prior art, the present inventors introduced a tertiary amino group at the end of a conjugated diene polymer,
Furthermore, it was proposed that a branched conjugated diene polymer with excellent processability, tensile strength, and impact resilience could be obtained by combining a camping agent such as a tin compound (Japanese Unexamined Patent Publication No.
No. 9-38.209), the amine compound used here is insufficient in improving the wet skid properties and the rolling friction resistance properties of the vulcanizate.

As a result of intensive studies aimed at further improving the wet skid properties, rolling friction resistance properties, and tensile strength of vulcanizates, the present inventors copolymerized a diene monomer and an aromatic vinyl compound using a lithium-based initiator. Subsequently, it was discovered that a rubber composition containing a diene copolymer obtained by reacting this with a specific isothiocyanate compound has excellent properties as described above, and the present invention has been achieved.

Means for Solving Problem d3 First, the present invention copolymerizes a conjugated diene and an aromatic compound using a lithium-based initiator, and then reacts the polymerization active end with an isothiocyanate compound. The amount of vinyl bond in the diene part is 20% or more, the content of aromatic vinyl compound is 10% by weight or more, and the glass transition temperature is 17% or more.
A rubber composition for tires characterized by containing 30% or more of a conjugated diene copolymer having a temperature of 0° C. or higher.

The vinyl content of the diene moiety in the conjugated diene (co)polymer of the present invention is 20% or more, preferably 30% or more.

The upper limit is at most 95%. It is industrially difficult to achieve more than this. If it is less than 20%, it becomes difficult to simultaneously improve wet skid characteristics and rolling friction resistance characteristics. That is, when an attempt is made to improve the wet skid characteristics, the rolling friction resistance characteristics become inferior, and when an attempt is made to improve the rolling friction resistance characteristics, the wet skid characteristics become inferior.

The content of the aromatic vinyl compound in the conjugated diene copolymer of the present invention is 10% by weight or more, preferably 15% by weight or more. If it is less than 10% by weight, the tensile strength will be poor, and the upper limit is not particularly limited, but it is 50% by weight or less, preferably 45% by weight.
It is as follows.

The conjugated diene copolymer of the present invention has a glass transition temperature (Tg
) is -70°C or higher, preferably -60°C or higher. The upper limit is preferably -20°C. If the glass transition temperature is lower than this temperature, the wet skid properties will be poor, which is not preferable. When Tg exceeds -20°C, tensile strength and rolling friction resistance properties tend to be poor.

The glass transition temperature (Tg) shows the value measured by DSC, and by the way, Li-based BR with a vinyl bond content of 12% is 1108°C, NR is 176°C, and emulsion polymerization 5BR 11500°C.
The temperature is 164°C.

Furthermore, the conjugated diene copolymer contains random copolymer blocks (A) and (B) having different vinyl bond content and aromatic vinyl compound content in the diene moiety in a weight ratio of 15 to 15.
It is a block copolymer containing 85/85 to 15, the amount of vinyl bonds in the block part (A) is 20% or more, preferably 25 to 50%, and the aromatic vinyl compound is 30% or less, preferably 25% or less. and the vinyl bond amount of the block part (B) is 60% or less, preferably 30 to 55%, the aromatic vinyl compound is 50% or less, preferably 20 to 50%, and the total vinyl bond amount of the block copolymer is is 20-7
A random type block copolymer with a total aromatic vinyl compound content of 5 to 40% provides a rubber composition with excellent ice skid properties, and has a low tan δ of vulcanizate.
It has a wide temperature distribution pattern, excellent breaking strength, and because it does not contain a poly (aromatic vinyl compound) block copolymer, it has excellent rolling friction resistance.

The conjugated diene copolymer of the present invention is produced by solution polymerizing butadiene and one or more of other conjugated diene compounds and aromatic vinyl compounds in a hydrocarbon solvent using a lithium-based initiator. , obtained by reacting isothiocyanate compounds.

The solution polymerization is performed using an organolithium compound as an initiator in the presence of an ether or a tertiary amine in a hydrocarbon solvent, and 0 to 35 parts by weight of an aromatic vinyl compound and 90 to 65 parts by weight of a conjugated diene compound. The monomer mixture can be charged all at once or intermittently or continuously for polymerization.

The polymerization method may be either a batch polymerization method or a continuous polymerization method.

Conjugated diene compounds used in the present invention include 1゜3-butadiene, isoprene, 1,3-pentadiene, 2,3-
Examples include dimethylbutadiene, preferably 1.3
-butadiene, isoprene.

Examples of the aromatic vinyl compound include styrene, P-methylstyrene, 0-methylstyrene, P-butylstyrene, and vinylnaphthalene, with styrene being preferred.

The hydrocarbon solvent used may be one or more selected from butane, pentane, 2-methylbutene, 1-methylbutene, hexane, heptane, cyclohexane, methylcyclopenkune, octane, benzene, and the like. The amount of hydrocarbon solvent used is 2 to 10 parts by weight per 1 part by weight of monomer.

Examples of organic lithium compounds include n-butyllithium, 5
ec-butyllithium, tert-butyllithium,
n-hexyllithium, 1,4-dilithiobutane, a reaction product of butyllithium and divinylbenzene, etc. are used.

The amount of the organic lithium compound used is 0.01 to 2.0 parts by weight per 100 parts by weight of the monomer.

Ethers and tertiary amines include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, 2
-Methoxymethyltetrahydrofuran, 2,5-dimethoxymethyltetrahydrofuran, N, N, N'N'
Ethers and tertiary amines such as -tetramethylethylenediamine, 1,2-dipiperidinoethane, diethyl ether, tetrahydrofuran, dioxane, pyridine, triethylamine can be used.

The amount of ether or tertiary amine used is in the range of 0.01 to 5 mol per 1 atomic equivalent of lithium in the organolithium compound, and the amount is 0.01 to 5 mol per 1 atomic equivalent of lithium in the organolithium compound.
The total amount of the four bonding metals is adjusted to be in the range of 20 to 70%.

Examples of thioisocyanate compounds include allylisothiocyanate, eosin-5-isothiocyanate, ethylisothiocyanate, P-sulfophenyl sodium isothiocyanate, tetramethylrhodamine inthiocyanate, naphthylisothiocyanate, and phenylisothiocyanate. , tar t-butylisothiocyanate, fluorescein isothiocyanate, 3-fluorophenylisothiocyanate, 4-fluorophenylisothiocyanate, methylisothiocyanate, rhodamine B isothiocyanate, phenyl-1°3-diisothiocyanate phenyl-1,3°5-triisothiocyanate, preferably aromatic thioisocyanate and aromatic polythioisocyanate compounds. The aromatic isocyanate compound is used in an amount of 0.1 to 10 equivalents, preferably 0.2 to 3 equivalents of isothiocyanate groups per mole of lithium atoms. Outside this range, the effect of improving rolling friction resistance and tensile strength cannot be obtained.

The copolymerization reaction using a lithium-based initiator and the reaction between the active end and aromatic polyisothiocyanate after copolymerization are 0
It is carried out in the range of ~150°C, and may be performed under isothermal conditions or under elevated temperature conditions.

The above-mentioned conjugated diene copolymer must be contained in an amount of 30% by weight or more in 100 parts by weight of raw rubber in the composition of the present invention, and if it is less than 30% by weight, the desired wet skid properties and rolling friction resistance properties may be impaired. , it is not possible to obtain a rubber composition with excellent tensile strength.

The conjugated diene copolymer of the present invention is a polymer with a uniform composition along the molecular chain of a side chain bond such as a vinyl bond, an aromatic vinyl derivative, or a polymer with a continuously changing composition, or a block Including those that are combined.

Mooney viscosity (M L
+. 4+100°C) is preferably in the range of 10 to 150; if it is less than 10, the tensile properties and rolling friction resistance properties will be poor, and on the other hand, if it exceeds 150, the workability will be poor, which is not preferred.

The rubber composition of the present invention contains the conjugated diene copolymer as an essential component, and contains natural rubber, high cis polyisoprene,
Emulsion-polymerized styrene-butadiene copolymers, 10-40% by weight of bound styrene, other solution-polymerized styrene-butadiene copolymers with a vinyl content of 10-80%, obtained using nickel, cobalt, titanium, neodymium catalysts High cis polybutadiene, ethylene-propylene-diene terpolymer, halogenated butyl rubber, halogenated ethylene-
It is used by blending with one or more rubbers selected from propylene-diene terpolymers. In particular, it is preferable to contain 10 to 70 parts by weight of natural rubber based on 100 parts by weight of the rubber content, since the tensile strength processability is improved. It is obtained by blending oil extenders such as aromatic process oils and naphthenic process oils, and various other compounding agents and vulcanizing agents as necessary.

82 Effect The conjugated diene copolymer used in the rubber composition of the present invention has a specific isothiocyanate modified group at the polymer end by reacting the lithium atom at the end of the polymer with an aromatic isothiocyanate compound. In this way, a rubber composition with excellent tensile strength, wet skid properties, ice skid properties, and rolling friction resistance properties of the vulcanizate is obtained.

r. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the Examples unless it goes beyond the gist of the present invention.

The reaction between the lithium atom at the end of the polymer and the aromatic isothiocyanate was confirmed by the change in molecular weight distribution before and after the reaction.

In addition, various measurements in the examples were based on the following.

The microstructure of the butadiene moiety (vinyl bond content) is
Obtained by infrared method (Morello method).

The styrene content was measured using an infrared method based on the absorption of phenyl groups at 699 cm-' using a predetermined calibration curve.

The molecular weight distribution (Ms/Mn) was measured using a Haters Model 200 GPC. The column is 5TYRA
GEL-10', 106.10', 10' (4
Feet x 4) were used. Tetrahydrofuran was used as a solvent.

Mooney viscosity is determined by preheating for 1 minute, measuring for 4 minutes, and temperature at 100°C.
It was measured with

The tensile strength was measured according to JIS K6301.

For the rolling friction resistance, the tan δ value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho was used as an index. The ice skid characteristics and the sea urchin skid characteristics were measured using a skid tester manufactured by Stanley.

Examples 1 to 13 Comparative Examples 1 to 4 The rubber compositions obtained in Examples 1 to 5 and 10 to 13 had a better balance of tensile strength, wet skid characteristics, and rolling friction resistance characteristics than Comparative Examples 1 to 4. Excellent. In particular, Examples 6 to 9 have better ice skid characteristics than Comparative Examples 1 to 4.

Polymer A> Add 20% of cyclohexane to a 5x reaction vessel purged with nitrogen.
00g, butadiene 400g, styrene 100g, and tetrahydrofuran 10g, and the temperature was set to 20°C.
3 g of -BuLi O was charged and adiabatic polymerization was carried out. After the polymerization was completed, 1 mol of phenylisothiocyanate was added per 1 mol of n-BuLi.

Met.

Polymer B> 200 ml of cyclohexane was added to a 51 reaction vessel purged with nitrogen.
0g, butadiene 385g, styrene 100g, and tetrahydrofuran Log, and the temperature was set to 20°C.
- 0.3 g of BuLi was charged and adiabatic polymerized. When the degree of polymerization reached a peak, 15 g of butadiene was added over 5 minutes, and after the polymerization was completed, 1 mol of phenylisothiocyanate was added to 1 mol of n-BuLi. Added.

was 28.

Polymer C> Add 20% cyclohexane to a 5j2 reaction vessel purged with nitrogen.
00 g, butadiene 385 g, styrene 100 g, and ethylene glycol diptyle ether 0.15 g were charged, and the temperature was raised to 20° C., and n -BuLi 0.3 g was charged, followed by adiabatic polymerization. When the polymerization temperature reached its peak, 15 g of butadiene was added over 5 minutes, and after the polymerization was completed, 1 mol of phenylisothiocyanate was added per 1 mol of n-BuLi.

was 35.

<Polymer D> 200 ml of cyclohexane was added to 52 reaction vessels purged with nitrogen.
0g, butadiene 400g, styrene 100g, Tei
・Prepare lahydrofuran Log and set the temperature to 20℃.
-0.3 g of BuLi was charged and adiabatic polymerization was carried out. After the polymerization was completed, 1 mol of naphthylisothiocyanate was added per mol of n-BuLiI.

was 35.

Polymer E) Add 200 g of cyclohexane to a 51 reaction vessel purged with nitrogen.
0g, butadiene 400g, styrene 100g, and tetrahydrofuran Log were prepared, and the temperature was set to 20°C.
-0.3 g of BuLi was charged and adiabatic polymerization was carried out. After completion of polymerization, phenyl-1,3-diisothiocyanate is added to n-B
1 mol was added per 1 mol of uLi.

was 45.

The molecular weight distribution curves of polymers A and H measured by gel permeation chromatography are shown in FIGS. 1 and 2.

The figure shows that the molecular weight distribution of the sample changes, indicating that the isothiocyanate compound is bonded to the polymer end by adding an aromatic isothiocyanate compound after copolymerizing a butadiene monomer with a lithium-based initiator. Suggests.

Polymer F> Cyclohexane 24
00g, butadiene 500g, tetrahydrofuran L
n-BuLiO,3 at a temperature of 20°C.
g was charged and polymerization was carried out. After the polymerization was completed, 1 mol of phenylisothiocyanate was added per 1 mol of n-BuLi.

The vinyl content of the butadiene portion was 54%.

<Polymer G> Cyclohexane 240 was added to a 51 reaction vessel purged with nitrogen.
0 g 1 360 g of butadiene, 40 g of styrene, 0.6 g of tetrahydrofuran, and heated to 50°C.
- BuLi 0.40g was charged, and the copolymer block (A) was polymerized under heat insulation. At the time when the zero polymerization salinity reached the peak (the monomer conversion rate was 97% at a temperature of 95°C) , ethylene glycol dibutyl ether 0.2
g, 80 g of styrene was added over 4 minutes, and 120 g of butadiene was added over 20 minutes, and the copolymer block (B) was polymerized in the range of 75 to 80°C. After the polymerization was completed, 1 mol of phenylisothiocyanate was added per 1 mol of n-BuLi.

The vinyl content of the butadiene moiety of copolymer block (A) was 25%, and the amount of bound styrene was 10%. The vinyl content of the butatsuene portion of the copolymer block (B) was 50%, and the amount of bound styrene was 40%.

The total bound styrene content of the block copolymer was 20%.

Polymer H> Add 24 cyclohexane to a 5Il reaction vessel purged with nitrogen.
00g, 315g of butadiene, 135g of styrene, and 15g of tetrahydrofuran, and heated to 15℃.
-0.35 g of BuLi was charged, and the copolymer block (A) was polymerized under heat insulation. When the polymerization temperature reached its peak (the monomer conversion was 97% at a temperature of 95°C), 0.0% of ethylene glycol dibutyl ether was added.
15 g of butadiene were added over 10 minutes, and the copolymer block (B) was polymerized in the range of 75 to 80°C. After polymerization, phenyl isothiocyanate is converted into n-
1 mol was added per 1 mol of BuLi.

The vinyl content of the butadiene moiety of copolymer block (A) was 60%, and the amount of bound styrene was 30%. The vinyl content of the butadiene portion of the copolymer block (B) was 50%.

was 30.

Furthermore, the proportion of long chain styrene blocks in which five or more styrenes were connected was 5% or less.

Polymer■〉 Add 240 ml of cyclohexane to a 51 reaction vessel purged with nitrogen.
0g, butadiene 400g, tetrahydrofuran 0.
Charge 5g of n-BuLi and adjust the temperature to 50°C to reduce n-BuLi to 0.4g.
0 g was charged, and the copolymer block (A) was polymerized under heat insulation. When the polymerization temperature reaches its peak (temperature 95℃)
(The monomer conversion rate was 97%), 0.2 g of ethylene glycol dibutyl ether, 80 g of styrene were added over 4 minutes, and 120 g of butadiene was added over 30 minutes. (B) was polymerized. After polymerization, phenyl isothiocyanate is converted into n-
1 mol was added per 1 mol of BuLi.

The vinyl content of the butadiene portion of the copolymer block (A) was 20%. The vinyl content of the butadiene moiety of the copolymer block (B) was 50%, and the amount of bound styrene was 40%.

The total bound styrene content of the block copolymer was 13%.

The proportion of long-chain styrene blocks in which five or more styrenes were connected was 5% or less.

Polymer J) Nitrogen-substituted 57! 20 cyclohexane in a reaction vessel
00g, butadiene 375g, styrene 125g, and tetrahydrofuran 10g, and heated to 30°C.
-BuLi 0.3g was charged and adiabatic polymerization was carried out. After the polymerization was completed, 1 mol of phenylisothiocyanate was added to 1 mol of n-BuLi.

Met.

Polymer K〉 200 ml of cyclohexane was added to a 51 reaction vessel purged with nitrogen.
0 g, 425 g of butadiene, 75 g of styrene, 1 log of tetrahydrofuran, the temperature was set to 15°C, and n-
0.3 g of BuLi was charged and adiabatic polymerization was carried out. After the polymerization was completed, 1 mol of phenylisothiocyanate was added per 1 mol of n-BuLi.

Met.

Polymer L) The internal volume with the stirrer and heating jacket is IOJ.
Add 12g/butadiene as a monomer to the glue actor.
3 g/win of styrene, 75 g/tn of cyclohexane as a solvent, 1.2 g/Ta1n of tetrahydrofuran, and 0.07 g of n-butyllithium per 100 g of monomer as a catalyst were continuously supplied with a pump. The reactor temperature was controlled at 70°C.

The polymerization conversion rate at the reactor outlet was 95% or more.

At the second reactor (101) population, phenyl isothiocyanate was added in an amount of 1 equivalent of phenyl thiocyanate group per mol of leutium atom, and the reaction was carried out.

there were.

(Polymer M) 200 ml of cyclohexane was added to a 51 reaction vessel purged with nitrogen.
0g 1 400g of butadiene, 100g of styrene, and 10g of tetrahydrofuran were charged and heated to 20°C.
-0.28 g of BuLi was charged and adiabatic polymerization was carried out.

Met.

Polymer N〉 Add 20% cyclohexane to a 5j2 reaction vessel purged with nitrogen.
00g, butadiene 475g, styrene 25g, and tetrahydrofuran 0.1g, and heated to 50°C.
-BuLiO, 35g was charged and adiabatic polymerization was carried out.

After completion of polymerization, phenylisothiocyanate is converted into nBu
1 mol was added per 1 mol of Lt.

Met.

According to the formulation shown in Table 1, the mixture was kneaded using a 250cc blast mill and vulcanized at 145°C for 30 minutes.

The physical property evaluation results are shown in Table-2.

The rubber compositions obtained in Examples 1 to 12 are excellent in the tensile strength of the vulcanizate, wet skid resistance, and rolling friction resistance properties. In particular, the rubber compositions obtained in Examples 6 to 9 are rubber compositions with excellent ice skin resistance.

g8 Effects of the invention The rubber composition of the invention is suitable for use in tire applications such as tire treads, carcass parts, and sidewall parts, belts, anti-vibration rubber, window frames, hoses, and industrial products. be able to.

The rubber composition containing the block copolymer obtained by the present invention has good wet skid properties, ice skid properties, and rolling friction properties, and has excellent breaking properties, so it can be used as a rubber material for tire treads. It can be suitably used as

[Brief explanation of the drawing]

Figures 1 and 2 are molecular weight distribution curves of samples (Polymers A and E) measured by gel permeation chromatography. HiXR~ ) (iXR~

Claims (3)

[Claims] (1) After copolymerizing a conjugated diene compound and an aromatic vinyl compound using a lithium-based initiator, the polymerization active terminal is reacted with an isothiocyanate compound, and the amount of vinyl bond in the diene part is 20 % or more, a conjugated diene copolymer having an aromatic vinyl compound content of 10% by weight or more and a glass transition temperature of -70° C. or more. (2) The conjugated diene copolymer contains random copolymer blocks (A) and (B) having different vinyl bond content and aromatic vinyl compound content in the diene moiety in a weight ratio of 15 to 85.
/85 to 15, the amount of vinyl bonds in the block part (A) is 20% or more, the amount of vinyl bonds in the block part (B) is 30% or less, and the amount of vinyl bonds in the block part (B) is 60% or less , the aromatic vinyl compound is 50% or less, and the total vinyl bond content of the block copolymer is 20 to 20%.
70%, and the total content of aromatic vinyl compounds is 5 to 40%. (3) 30 to 90% by weight of the conjugated diene copolymer;
The rubber composition for tires according to claim 1 or 2, which has a rubber component consisting of 70 to 10% by weight of natural rubber.