JPS61141741A - Butadiene rubber composition - Google Patents

Abstract

PURPOSE:To improve the wet skid characteristics and rolling frictional resistance of vulcanized products, by (co)polymerizing butadiene alone or a mixture thereof with other monomer in the presence of a lithium polymn. initiator and reacting the resulting polymer with an isocyanate compd. CONSTITUTION:Butadiene or a mixture thereof with at least one monomer selected from among other conjugated dienes and arom. vinyl compds. is (co) polymerized in the presence of a lithium polymn. initiator such as n-butyllithium. The terminals of the resulting (co)polymer are reacted with an isocyanate compd. The resulting (co)polymer contains a polymerized butadiene moiety having a bonded vinyl content of 15% or above and a glass transition temp. of -70 deg.C or above. At least 30wt% said (co)polymer is incorporated in a rubber compsn. to provide a vulcanized product having improved characteristics. Preferred examples of the isocyanate compds. are arom. polyisocyanates (e.g. diphenylmethane diisocyanate).

Description

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

[Conventional technology]

In recent years, with the demand for safety and low fuel consumption for automobiles, conjugated diene polymers with excellent wet skid properties, fuel economy properties, and wear properties have been required as rubber materials for tires, especially tire trends. Became.

Conventionally, these conjugated diene polymers were
996, U.S. Patent No. 3,956.232, JP-A-57-205.414, etc., a conjugated diene compound is prepared using an organolithium initiator in a hydrocarbon solvent. or by copolymerizing a conjugated diene compound and a vinyl aromatic compound, and then reacting it with a tin halide compound or an alkenyl tin compound.

[Problem that the invention seeks to solve]

However, since the polymer ends are composed of carbon-tin bonds, the above polymers are susceptible to chemical reactions with acidic substances such as inorganic acids, organic carboxylic acids, and Lewis acids, organic phosphorus compounds, and even organic sulfur compounds, strong acids, and strong Due to hydrolysis reaction under alkaline conditions, the carbon-tin bond at the end of the polymer is easily broken, resulting in deterioration of physical properties, which limits the types of rubber additives that can be used.

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 to obtain a branched conjugated diene polymer with excellent processability, tensile strength, and impact resilience by combining a coupling agent such as a tin compound (Japanese Unexamined Patent Publication No. 59/1999).
38.209), the amine compound used here is insufficient in improving the rolling friction resistance and wet skid 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 found that after (co)polymerizing a diene monomer using a lithium-based initiator, a specific The present invention was achieved by discovering that a rubber composition containing a diene (co)polymer obtained by reacting an isocyanate compound with the above-mentioned properties is excellent.

[Means for solving problems]

That is, the present invention involves the polymerization of butadiene using a lithium-based initiator, or the (co)polymerization of butadiene and one or more types of heptamines selected from other conjugated dienes and aromatic vinyl compounds, and then the polymerization process. Contains 30% by weight or more of a diene (co)polymer with a vinyl bond content of the butadiene moiety of 15% or more and a glass transition temperature of 170°C or more, which is obtained by reacting the active terminal with an isocyanate compound. This is a characteristic butadiene rubber composition.

The vinyl content of the butadiene moiety in the butadiene copolymer of the present invention is 15% or more, preferably 20% or more, and more preferably 30% or more. Further, from the viewpoint of manufacturing and effectiveness, it is preferably 90% or less.

If it is less than 15%, it will be 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 butadiene-based (co)polymer of the present invention has a glass transition temperature (
Tg) is -70°C or higher, preferably -60°C or higher.

In addition, from the viewpoint of effectiveness, it is preferable that the glass transition temperature is -30°C or less. If the glass transition temperature is lower than this temperature, the wet skid characteristics will be poor and it is not preferable. Amount 12% L
i-system BR: 1108℃, NR: 176℃, emulsion polymerization 5B
R1) 500 is -64°C.

The butadiene-based (co)polymer of the present invention is obtained by solution polymerizing butadiene alone or butadiene and one or more of other conjugated dienes and aromatic vinyl compounds in a hydrocarbon solvent using a lithium-based initiator. After that, it is obtained by reacting an isocyanate compound.

Other conjugated dienes used include isoprene and pentadiene, and aromatic vinyl compounds used include styrene vinyltoluene and α-methylstyrene.

In particular, a styrene-butadiene copolymer having a styrene content of 5% by weight or more is preferable because it has excellent wet skid properties, rolling friction resistance properties, high tensile strength, and processability.

The content of styrene is not particularly limited, but 50
It is less than 45% by weight, preferably less than 45% by weight.

Furthermore, examples of hydrocarbon solvents include pentane, hexane, heptane, octane, methylcyclobencune, cyclohexane, benzene, xylene, and the like.

The lithium-based initiator used is an alkyllithium such as n-butyllithium, 5ec-butyllithium, 1,4-dilithiobutane, or the like.

The lithium-based initiator is used in an amount of 0.1 to 100 equivalents of lithium atoms per 100 g of monomer.

In particular, by combining 1,4-dilithiobutane or alkyl monolithium with a polyfunctional polymer such as divinylbenzene, and copolymerizing a conjugated diene monomer, the resulting polyfunctional polymer terminal is reacted with an isocyanate compound. A (co)polymer with excellent tensile strength is obtained.

Examples of the isocyanate compound include 2.4-)lylene diisocyanate, 2.6-tolidine diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, triphenylmethane triisocyanate, and P-phenylene diisocyanate. Diisocyanate, tris(isocyanate compound) thiophosphate, xylylene diisocyanate, Hensen-1,2
゜4-triisocyanate, naphthalene-1,2゜5.
7-titraisocyanate, naphthalene-1°3.7-
) diisocyanate, phenyl isocyanate, hexamethylene diisocyanate, methylcyclohexane diisocyanate, and the like. Preferably, aromatic isocyanate compounds such as aromatic diisocyanates or triisocyanates, dimers and trimers of various aromatic isocyanate compounds, and adducts obtained by reacting the above aromatic isocyanates with polyols or polyamines are preferable. used. More preferred are aromatic polyisocyanate compounds such as 2.4-)lylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate. The aromatic isocyanate compound is used in an amount of 0.1 to 10 equivalents, preferably 0.2 to 3 equivalents of isocyanate groups per mole of lithium atoms.

Outside this range, the effect of improving rolling friction resistance and tensile strength cannot be obtained.

The (co)polymerization reaction using a lithium-based initiator and the reaction between the active end and isocyanate after copolymerization are carried out at 0°C to 150°C.
℃ range, and may be performed under isothermal or elevated temperature conditions. The polymerization method may be either a batch polymerization method or a continuous polymerization method.

The microstructure of the butadiene moiety of the butadiene copolymer is tetrahydrofuran, diethyl ether, dimethoxybenzene, dimethoxyethane, ethylene glycol dibutyl ether, triethylamine, pyridine, N, N,
By adding ethers and tertiary amine compounds such as N',N'-tetramethylethylenediamine and dimethoxyethane to the polymerization system, the vinyl bond content can be changed freely.

In addition, the butadiene content in the butadiene-based (co)polymer is preferably 300 equivalents or more from the viewpoint of tensile strength.
It is necessary to contain 30% by weight or more, more preferably 400 equivalents or more in 100 parts by weight of raw rubber, and if it is less than 31%, a rubber composition with excellent wet skid properties, rolling friction resistance properties, and tensile strength as desired will be obtained. I can't do it.

The butadiene (co)polymer of the present invention has a side chain bond such as a vinyl bond, a polymer with a uniform composition along the molecular chain of an aromatic vinyl derivative, or a polymer with a continuously changing composition, or Including those connected in blocks.

The butadiene type (co) of the present invention also has a Mooney viscosity (
M L +-a, 100°C) is preferably in the range of 10 to 150; if it is less than 10, tensile properties and rolling friction resistance properties will be poor, and on the other hand, if it exceeds 150, it will be poor in workability, which is not desirable. .

The rubber composition of the present invention has the butadiene (co)polymer as an essential component, and contains natural rubber, high cis polyisoprene, emulsion polymerized styrene-butadiene copolymer, bound styrene in an amount of 10 to 40% by weight, vinyl Other solution polymerized styrene-butadiene copolymers with a content of 10-80%, nickel, cobalt, titanium, high cis polybutadiene obtained using neodymium catalysts, ethylene-propylene-diene terpolymers, halogenated One or two of butyl rubber, halogenated ethylene-propylene-diene terpolymer
It is obtained by blending with at least one selected rubber, and adding an oil extender such as an aromatic process oil or a naphthenic process oil, other compounding agents, and a vulcanizing agent as necessary.

[Effect]

The butadiene-based (co)polymer used in the rubber composition of the present invention has an isocyanate-modified group at the polymer end by reacting the lithium atom at the end of the polymer with an isocyanate compound. A rubber composition with excellent tensile strength, wet skid properties, and rolling friction resistance properties of sulfur is obtained.

〔Example〕

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

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

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

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

The molecular weight distribution (Mw/Mn) is 20
0 type GPC unit measurement site. 1i-7 Muha, 5TYRAG
EL-10', 10', 10', 10' (4 feet x 4) was used. Tetrahydrofuran was used as a solvent.

Mooney viscosity is determined by preheating for 1 minute, measuring time for 4 minutes, and temperature at 100.
Measured at °C.

The tensile strength was measured according to JIS K6301.

Wet skid resistance was measured at room temperature (25° C.) using a Stanley skid tester, and expressed as an index with Comparative Example 4 set as 100, and the larger the value, the better.

The rolling friction resistance characteristics were measured using rebound resilience as a substitute characteristic. 50℃ as an indicator of tire rolling friction resistance
The measurement was carried out using a Danronop trypsometer as the measuring instrument.

Examples 1 to 17 Comparative Examples 1 to 8 (Polymer A to
0> Cyclohexane, monomers, and tetrahydrofuran were charged into a nitrogen-substituted reactor with an internal volume of 51 cm according to the recipe shown in Table 1, and then a lithium-based initiator was added and the polymerization reaction was carried out at 30 to 90°C under heat insulation. I did it.

After the polymerization conversion rate reached 100%, the isocyanate compound was added in the amount shown in Table 1 and reacted. (0.7g of G-tert-butyl-P-cresol was added as an anti-aging agent to 100g of rubber, and desolubilized and
Drying was performed.

In addition, Figures 1 and 2 show samples (poly?-B, D, H
, C). From the figure, the sample has a bi-modal molecular weight distribution, and it is confirmed that the isocyanate compound is bonded to the polymer terminal by (co)polymerizing the butadiene monomer with a lithium-based initiator and then adding the isocyanate compound. It shows.

Table 2 shows the results of measuring the properties of the obtained polymer.

Polymer P-Q> A butadiene-based (co)polymer was obtained in the same manner as Polymer-A using the recipe shown in Table 1, except that silicon tetrachloride or diethyl adipate was used in place of the isocyanate compound.

Table 2 shows the results of measuring the properties of the copolymer.

(Polymer RT> A butadiene-based (co)polymer was obtained using the recipe shown in Table 1 in the same manner as Polymer A except that no isocyanate compound was used.

The results of measuring the properties of the (co)polymer are shown in Table 2.

<Polymer-U> Butadiene 12g/wi as a reactor with an internal volume of 102 equipped with a stirrer and a heating jacket.
n, styrene at 3g/l1lin, cyclohexane as solvent at 75g/win, tetrahydrofuran at 1g/win.
win, monomer 1 using n-butyllithium as a solvent
The reactor temperature was controlled at 70°C.

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

At the inlet of the second reactor (101), diphenylmethane diisocyanate was added in an amount of 1 equivalent of isocyanate group per 1 mole of lithium atom and reacted. 2
Apply anti-aging agent (G-tert-butyl-P-cresol) at the outlet of the base glue actor to rubber 1
0.73 g was added to 0.00 g, and desolubization and drying were performed in a conventional manner. Polymer obtained in Table 3 (Polymer U)
The measurement results of the cord characteristics are shown.

The polymer A-U obtained above was kneaded using a 250cc plastomill according to the formulation shown in Table 4, and
Vulcanization was performed at 45°C for 30 minutes. The physical property evaluation results are shown in Table-5.

The rubber compositions obtained in Examples 1 to 17 are rubber compositions with excellent tensile strength, wet skid resistance, and rebound resilience of vulcanizates, and can be used in tire treads, sidewalls, or various industrial materials. It is a rubber material suitable for

Table 3-4 Parts by weight of blended polymer 100RAP carbon 5° stearic acid
2 Zinc white
3 sulfur
1.5 [Effects of the Invention] The rubber composition of the present invention can be used for tire applications such as tire tread parts, carcass parts, and sidewall parts, and applications such as belts, anti-vibration rubber, window frames, bows, and industrial products. It can be suitably used.

[Brief explanation of the drawing]

Figures 1 and 2 show the molecular weight distribution pattern of the sample (polymer, D. H, C) measured by gel vermini-silane chromatography. HiXR HiXR

Claims (4)

[Claims] (1) After polymerizing butadiene using a lithium-based initiator, or copolymerizing butadiene with one or more monomers selected from other conjugated dienes and aromatic vinyl compounds, the polymerization active terminal is converted into an isocyanate compound. The vinyl bond content of the butadiene moiety obtained by reacting with is 15
% or more, and a butadiene-based (co)polymer having a glass transition temperature of -70° C. or more by 30% by weight or more. (2) The rubber composition according to claim 1, wherein the isocyanate compound is an aromatic isocyanate compound. (3) The rubber composition according to claim 1, wherein the isocyanate compound is an aromatic polyisocyanate compound. (4) The butadiene type (co)polymer has a styrene content of 5
The rubber composition according to any one of claims 1 to 3, which is a random styrene-butadiene copolymer in an amount of at least % by weight.