JP3345950B2 - Method for producing conjugated diene polymer rubber and vulcanizable rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a diene polymer capable of achieving high vulcanizability and a high degree of vulcanization, and a vulcanizable rubber composition using the diene polymer obtained by this method. It is about.

[0002]

2. Description of the Related Art When producing a conjugated diene polymer rubber by emulsion polymerization, mercaptans have been conventionally used as a molecular weight modifier. Dodecyl mercaptan is particularly widely used because of its molecular weight adjustment efficiency and availability. The most frequently used mercaptan is t-dodecyl mercaptan, which is a mixture of various isomers and is called t-dodecyl mercaptan, but its composition cannot be analyzed and is unknown.

[0003] In recent years, there has been an increasing demand for high-speed vulcanization from the viewpoint of improving the productivity during the production process of rubber products and saving labor in rubber processing manufacturers. In order to meet this demand, rubber-like polymers have been improved. For example, adding a functional group such as a carboxyl group or an amino group to the polymer,
A method to improve vulcanizability by introducing or adding a vulcanization accelerator as an additive, and minimizing polymerization auxiliary materials such as emulsifiers and coagulants remaining in rubbery polymers that affect vulcanization. Various methods have been proposed, such as a method for performing such operations. However, these methods have problems that not only the desired effect is not sufficient, but also other properties such as cold resistance and compression set are impaired.

[0004]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to develop a conjugated diene polymer rubber obtained by emulsion polymerization capable of high-speed vulcanization. As a result, surprisingly, the mercapcaptan having a specific structure has a molecular weight of By using as a modifier, high-speed vulcanization is possible, and it has been found that a conjugated diene-based polymer rubber with improved rebound resilience and abrasion resistance of the vulcanized product can be obtained. It was completed.

[0005]

Thus, according to the present invention, when emulsion polymerization of a monomer other than a conjugated diene or a conjugated diene and an unsaturated nitrile compound copolymerizable with the conjugated diene, a bond to a tertiary carbon atom is provided. A conjugated diene system comprising a molecular weight modifier containing at least 50% by weight of at least one mercaptan having 8 to 16 carbon atoms and having at least one mercapto group and at least one tertiary butyl group. A method for producing a polymer rubber is provided.

According to the present invention, at least one of mercaptans having a total of 8 to 16 carbon atoms and having a mercapto group and at least one tertiary butyl group bonded to a tertiary carbon atom is added in an amount of 50% by weight. % Of a conjugated diene or a conjugated diene-based polymer rubber obtained by emulsion polymerization of a monomer other than a conjugated diene and an unsaturated nitrile compound copolymerizable therewith using a molecular weight modifier containing at least And a vulcanizable rubber composition characterized by being compounded with a vulcanizing system. .

The conjugated diene used in the emulsion polymerization of the present invention includes 1,3-butadiene, 1,3-dimethylbutadiene, isoprene, chloroprene, and derivatives thereof, and one or a combination of two or more thereof. Can be used. Monomers other than the unsaturated nitrile compound copolymerizable with the conjugated diene include aromatic monomers such as styrene, α-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, hydroxymethylstyrene, and derivatives thereof. Vinyl compound, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid Esters of unsaturated carboxylic acids such as lauryl and hydroxyethyl (meth) acrylate; unsaturated amide compounds such as (meth) acrylamide and N-methyl acrylamide; vinyl monomers such as acrolein, vinyl chloride and vinyl acetate And the like. These monomers are copolymerized with a conjugated diene alone or in combination of two or more. A particularly preferred combination is a conjugated diene and an aromatic vinyl compound.

In this case, the amount of the aromatic vinyl compound is preferably 5 to 60% by weight of the total charged monomers, and if it is less than 5% by weight, the mechanical strength is poor, and if it exceeds 60% by weight, the rubber elasticity is poor. . When combining a monomer other than the conjugated diene and the aromatic vinyl compound, the type and amount of the monomer are appropriately determined according to the properties required for the copolymer rubber, and in the present invention, The type and amount of the monomer are not particularly limited.

In the emulsion polymerization of the present invention, at least one mercapto group bonded to a tertiary carbon atom is contained in the molecular weight modifier.
A molecular weight modifier containing at least 50% by weight of at least one of mercaptans having 8 to 16 carbon atoms having three tertiary butyl groups is used.

The above mercaptan used in the present invention is:
It is necessary to have the above structure in order to improve the vulcanization rate and degree of vulcanization of the obtained conjugated diene polymer rubber. Further, the total number of carbon atoms is 8 to 16, and when the total number of carbon atoms is out of this range, the degree of controlling the molecular weight is reduced. Preferably, it is 8-12. Further, this mercaptan can be used alone or in combination with another molecular weight modifier such as another mercaptan. When used in combination, the content of the mercaptan in the total molecular weight modifier is at least 50% by weight, and if it is less than this, it is difficult to achieve the object of the present invention.

The mercaptan having the above structure includes 2,4,4'-trimethyl-2-thiol, 2,2 ',
4,6,6'-pentamethyl-heptane-4-thiol,
2,2 ', 4,4', 6-pentamethyl-heptane-6-thiol, 2,2 ', 4,6,6', 88'-heptamethyl-
Nonane-4-thiol and the like are included, but not limited thereto.

The feature of the method of the present invention resides in that the above-mentioned molecular weight controlling agent containing mercaptan is used. Thus, high-speed vulcanization, which cannot be obtained by using a commercially available t-dodecyl mercaptan, which is conventionally used, is achieved. It is possible to produce a conjugated diene-based polymer rubber which gives a vulcanized rubber having a degree of sulfurization (the maximum torque in a vulcanization curve measured by an oscillating disk rheometer being at a high level). .

Other molecular weight regulators used in combination with the above mercaptans include, for example, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-
Mercaptans such as hexadecyl mercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan; xanthogen disulfides such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl thiol Thiuram disulfides; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate, terpinolene, α- Terpinene, γ-terpinene, dipentene, α-methylstyrene dimer (2-
Preferably, the content of 4-diphenyl-4-methyl-1-pentene is 50% by weight or more), 2,5-dihydrofuran,
Examples thereof include 3,6-dihydro-2H-pin, phthalane, 1,2-butadiene, and 1,4-hexadiene.

The amount of the molecular weight modifier used in the present invention is usually
Monomer or monomer mixture 10 subjected to polymerization or copolymerization
0.05 to 3 parts by weight, preferably 0.1, relative to 0 parts by weight.
To 1 part by weight, and the amount used in this range is advantageous in adjusting the molecular weight of the polymer rubber.

In the emulsion polymerization of the present invention, emulsifiers, polymerization initiators and other polymerization agents conventionally used in emulsion polymerization can be used except for the use of the above-mentioned molecular weight regulator. Is not particularly limited. The method of emulsion polymerization is not particularly limited, and a conventional method is used.

The polymerization is carried out, and when a predetermined conversion is reached, the polymerization is terminated by adding hydroxylamine, sodium carbamate or the like. Next, after removing residual monomers by heating, steam distillation, etc., an inorganic coagulant such as calcium chloride or aluminum sulfate, a coagulant used in a normal emulsion polymerization such as a polymer coagulant or a thermosensitive coagulant is added. Then, the polymer is coagulated and recovered. Wash the recovered polymer with water,
Dry to obtain the desired conjugated diene polymer rubber. Mooney viscosity of the polymer rubber [ML _{1 + 4} (100 ° C)]
Is usually 20 to 15 in terms of mechanical strength, workability, and the like.
It is in the range of 0. When the polymer rubber is used as the oil-extended rubber, it may exceed 150.

The vulcanizable rubber composition of the present invention comprises a conjugated diene-based polymer rubber produced by emulsion polymerization using the above-mentioned specific molecular weight modifier as at least a raw rubber component, and a vulcanization system is added thereto. It is a rubber composition that is compounded.
Although the vulcanization system varies depending on the type of component rubber used and the intended use (use) of the rubber composition, the most suitable vulcanization system can be appropriately selected from vulcanization systems conventionally used. In the present invention, the vulcanization system is not particularly limited.

Specifically, a sulfur vulcanization system (sulfur-donating compound such as sulfur or sulfur monochloride, morpholine disulfide, tetramethylthiuram disulfide / stearic acid) which is a general vulcanization system of a conjugated diene polymer rubber /
Zinc white / Vulcanization accelerators (thiourea, guanidine, thiazole, imidazoline, thiuram, dithioate, etc.)], organic peroxides (t-butyl hydroperoxide, cumene hydroperoxide, etc.) Di-t-butyl peroxide, t-butyl cumyl peroxide,
2,5-dimethyl-t-butylperoxyhexane, 2,
5-dimethyl-t-butylperoxyhexyne, 1.3
-Bis (t-butylperoxyisopropyl) benzene, p-chlorobenzoyl peroxide, t-butylperoxybenzoate,

T-butyl peroxyisopropyl carbonate, t-butyl benzoate and the like, or polyfunctional such as trimethylolpropane trimethacrylate, divinylbenzene, ethylene dimethacrylate, triallyl isocyanurate and the like. In combination with a cross-linking aid such as a hydrophilic compound), and metallic soap which is a vulcanization system of acrylic rubber /
Sulfur, triazine / dithiocarbamate, polycarboxylic acid / onium salt, polyamine (hexamethylenediamine, triethylenetetramine, hexamethylenediaminecarbamate, ethylenediaminecarbamate, triethylenediamine, etc.), ammonium benzoate, etc. Can be

The amount of these vulcanizing systems used is not particularly limited in the present invention, and can be appropriately determined so as to satisfy the characteristics required in the conventional range of use for each vulcanizing system.

In the rubber composition of the present invention, if necessary, other compounding agents, such as reinforcing agents (various carbon black, silica, talc, etc.), fillers (calcium carbonate, clay, etc.), processing, Conventional rubber compounding agents such as auxiliaries, process oils (including plasticizers), antioxidants and antiozonants can be added.

The rubber composition of the present invention is produced by kneading a rubber component with a vulcanizing system and other compounding agents using a conventional mixer such as a roll or a Banbury mixer. In the rubber composition of the present invention, other polymer rubbers other than the conjugated diene-based polymer rubber of the present invention can be used in combination, provided that the amount thereof is within a range that does not impair the effects of the present invention. There is no particular limitation. Usually, it is 90% by weight or less in all rubber components. Other polymer rubbers include natural rubber, cis 1,4-polyisoprene rubber, solution-polymerized and emulsion-polymerized styrene-butadiene copolymer rubber, cis 1,4-polybutadiene rubber, and ethylene-propylene-diene terpolymer. Coalesced rubber (EPDM) and acrylonitrile-butadiene copolymer rubber.

[0023]

The present invention will be described more specifically with reference to the following examples. Parts and% in Examples, Comparative Examples and Reference Examples are based on weight unless otherwise specified. In addition,
Evaluation of the physical properties of the rubber composition of the present invention is mainly based on JIS K
-6301. The degree of vulcanization was determined by SRIS 310
2 (Japan Rubber Association standard), the scorch time (T ₅ ) and the maximum torque (V _max )
Measured using a disk rheometer.

Example 1 Emulsion polymerization was carried out at 5 ° C. in an autoclave having an internal volume of 10 liters using the emulsion polymerization recipe shown below. The following and Table 1 molecular weight modifiers were used. Water 200 butadiene 70 styrene 30 disproportionated rosin acid K / fatty acid Na 4.5 chloride K 0.1 2,4,4'-trimethyl-pentan-2-thiol 0.25 cumene hydroperoxide 0.1 Sodium formaldehyde sulfoxylate 0.2 Ferric sulfate 0.01

When the polymerization conversion reached 90%, the polymerization was terminated by adding 0.2 parts of hydroxylamine sulfate per 100 parts of monomer. Subsequently, after heating and recovering the residual monomer by steam distillation at about 70 ° C. under reduced pressure,
Add 2 parts of alkylated phenol as anti-aging agent,
Next, a polymer latex was added to a saline / sulfuric acid aqueous solution to coagulate the polymer. The generated crumb was taken out, washed with water and dried under reduced pressure at 50 ° C. to obtain a polymer rubber I for evaluation. Similarly, polymer rubbers II to VIII were obtained. Table 1 shows the polymerization results.

[0026]

[Table 1]

Example 2 The polymer rubber obtained in Example 1 was kneaded with a Banbury mixer according to the compounding recipe shown in Table 2 to obtain a rubber composition, and then press-vulcanized at 160 ° C. for 20 minutes. The physical properties of the obtained vulcanized product were measured according to JIS K6301. Table 3 shows the results.

[0028]

[Table 2]

Example 3 Each of the rubbery polymers I and III of Example 1 and styrene-butadiene copolymer rubber (SBR: Nipol 1502 manufactured by Nippon Zeon Co., Ltd.), cis 1,4-polybutadiene rubber (BR: Nippon Zeon) Nipol 1220)
Alternatively, a 50:50 mixture with natural rubber (NR) was used as a raw rubber, and the properties of the vulcanized product were measured in the same manner as in Example 2. The results are shown in Table 3.

[0030]

[Table 3]

[0031]

As described above, according to the present invention, the vulcanization rate is high, the vulcanization efficiency is high, and the excellent physical properties are obtained by emulsion-polymerizing a conjugated diene monomer or the like using a specific molecular weight modifier. A conjugated diene polymer rubber having a balance is obtained. Therefore, it can be suitably used for the production of various rubber products such as vulcanizable rubber compositions, packings, sealing materials, belts, hoses, rolls, shoe soles and flooring materials using the polymer rubber of the present invention as a raw rubber component.

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Claims (4)

(57) [Claims] 1. An emulsion polymerization of a monomer other than a conjugated diene or a conjugated diene and an unsaturated nitrile compound copolymerizable with the conjugated diene and a mercapto group bonded to a tertiary carbon atom and at least one tertiary carbon atom. A method for producing a conjugated diene-based polymer rubber, comprising using a molecular weight modifier containing at least one kind of mercaptan having 8 to 16 carbon atoms having a butyl group in an amount of 50% by weight or more. 2. The method according to claim 1, wherein the conjugated diene is butadiene or isoprene, and the copolymerizable monomer is an aromatic vinyl compound. 3. The method according to claim 2, wherein the molecular weight modifier is a mercaptan.
3. The method for producing a conjugated diene-based polymer rubber according to claim 1, which is a mixture with a mixture of graded dodecyl mercaptan. 4. A molecular weight control containing at least 50% by weight of at least one of mercaptans having 8 to 16 carbon atoms and having a mercapto group and at least one tertiary butyl group bonded to a tertiary carbon atom. Using a conjugated diene or a conjugated diene and a conjugated diene-based polymer rubber obtained by emulsion polymerization of a monomer other than a conjugated diene and an unsaturated nitrile compound copolymerizable therewith as at least a raw material rubber, and vulcanizing A vulcanizable rubber composition characterized by comprising a system.