JPH0621196B2 - Powdered rubber and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [I] Object of the Invention 1) Field of Industrial Application The present invention relates to a powdery sulfur-modified chloroprene rubber excellent in scorch prevention and a method for producing the same. More specifically, thiurams, thiazoles, and
The present invention relates to a novel powdery sulfur-modified chloroprene rubber containing a sulfur compound selected from the group consisting of and sulfenamides dispersed therein, and a method for producing the same.

2) Conventional technology Rubber is often isolated from rubber litex,
Its shape has been provided in the form of relatively large blocks (blocks or veils) or chips. 2. Description of the Related Art In recent years, powder rubber capable of automatic weighing and continuous processing has been in high demand in the market for the purpose of labor saving or energy saving with the progress of rubber processing technology.

Generally, powdered rubber is produced by physically or mechanically pulverizing and then adding a coagulation inhibitor such as calcium carbonate or talc, and a rubber litex coagulant such as polyvalent metal salt. There are two types of chemical methods, in which powder is separated into powder and then isolated. The former method has a drawback that it is difficult to obtain a rubber powder having a small particle diameter and a uniform size due to heat generation of rubber during pulverization, and a large amount of an anticoagulant is required to prevent coagulation. on the other hand,
The latter case is disadvantageous because a large amount of an inorganic salt is mixed in the rubber powder and the stability of the rubber powder is impaired (scorch).

In consideration of such a point, the inventors of the present invention have previously described a method for producing a powder rubber essentially containing no inorganic substance (JP-A-53-73).
244) was invented. However, the powdery sulfur-modified chloroprene rubber produced by this method has not been sufficiently improved in stability. At present, it is impossible to produce a powdery sulfur-modified chloroprene rubber which is excellent in scorch prevention even if the above-mentioned other methods for producing powdered rubber are used.

The sulfur-modified chloroprene rubber referred to here is a copolymer of sulfur and chloroprene, and in addition to the well-balanced physical properties such as oil resistance, weather resistance, and ozone resistance of chloroprene rubber, Flexural fatigue, high elasticity,
It is a rubber used in various industrial products because of its excellent properties such as high tearability. The powder rubber of the present invention is powdery sulfur-modified chloroprene rubber.

3) Problems to be Solved by the Invention An object of the present invention is to provide a powdery sulfur-modified chloroprene rubber excellent in scorch prevention and a method for producing the same.

[II] Configuration of the invention 1) Means for solving the problem The present inventors have conducted extensive studies for the purpose of providing a powder rubber and a method for producing the same, which have overcome these drawbacks.
It has been found that a powdery sulfur-modified chloroprene rubber having a sulfur compound selected from thiurams, thiazoles, and sulfenamides dispersed therein is excellent in preventing scorch, and the powder rubber of the present invention and The manufacturing method has been completed. The details will be described below.

2) Work A novel powdery sulfur-modified chloroprene rubber having a sulfur compound selected from thiurams, thiazoles, and sulfenamides dispersed in the powder rubber of the present invention has not been achieved so far. A powdered rubber with significantly improved scorch-preventing property, which is prepared by mixing a sulfur-modified chloroprene rubber latex of anionic or nonionic nature with the above sulfur compound and an anionic water-soluble polymer, and then mixing the mixed solution with the anionic water-soluble polymer. The method is characterized by mixing an acidic polymer with an aqueous solution of a cationic polymer or a cationic surfactant that causes coacervation under acidic conditions.

3) Detailed Description of the Invention The rubber targeted by the present invention is chlorobrene (2-
A copolymer of chlorobutadiene-1,3) and sulfur or a copolymer of a third component copolymerizable with chlorobrene, which can be used as long as it is obtained as an anionic or nonionic latex. Is. The amount of sulfur added was 0.
05 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight. The third component copolymerizable with chlorobrene is at least one polymerizable group having the structure CH ₂ ═C <,
For example, vinyl-substituted aromatic compounds (styrene, vinyltoluene, vinylnaphthalene, etc.), acrylic acid and methacrylic acid esters, nitriles (methyl acrylate, acrylonitrile, etc.), conjugated aliphatic dienes (1,3-
Butadiene, isoprene, 2,3-dichloro-1,3-butadiene, etc.). The addition amount is preferably 10 parts by weight or less based on 100 parts by weight of chlorobrene.

Examples of the anionic water-soluble polymer used in the present invention include natural products such as sodium alginate, gum arabic, carrageenan, and agar, sodium carboxymethyl cellulose, polyvinyl sulfonic acid, polystyrene sulfonic acid, methyl acrylate copolymer, and methyl methacrylate. These are synthetic products such as methacrylate copolymer, vinyl acetate / crotonic acid copolymer, styrene / maleic acid copolymer, cellulose acetate phthalate, starch acetate phthalate. These water-soluble polymers are used in an amount of 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on chloroprene rubber, and mixed with the rubber litex in the form of an aqueous solution.

The sulfur compounds used in the present invention are thiurams, thiazoles, and sulfenamides.

Examples of thiurams are tetramethyl thiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD), tetramethyl thiuram monosulfide (TMTS), dipentamethylene.
Examples include thiuram / tetrasulfide, tetrabutyl / thiuram / disulphide (TBTD). Examples of thiazoles include 2-mercapto penzothiazole (M
BT), dibendithiazyl disulfide (MBT
S), 2,4-dinitrophenyl benzothiazyl sulfide (DBM) and the like. Sulfenamides include N-cyclohexylbenzothiazyl-2-sulfenamide (CBS), N-oxydiethylene benzothiazyl-2-sulfenamide (NOBS), diisopropyl benzothiazyl-2-sulfenamide (DIBS). ), Diethyl benzothiazyl-2-sulfenamide and the like. These sulfur compounds may be added to the rubber latex as they are, but it is preferable to add them as an aqueous slurry. As a method of making the sulfur compound into a water slurry, a method of dispersing the sulfur compound in water as fine particles as uniformly as possible using a colloid mill, a vortex pump, a high speed mixer or the like is preferable.
The water slurry concentration of the sulfur compound is 1.0 to 40.
It is used in the range of weight%, preferably 2 to 10 weight%. These sulfur compounds are used in an amount of 0.05 to 10 parts by weight, preferably 0.1 to 100 parts by weight of chloroprene rubber.
It is used in the range of up to 5 parts by weight. The amount of sulfur compounds is 0.
If it is less than 05 parts by weight, the effect of preventing scorch is small. When it is used in an amount of more than 10 parts by weight, the scorch preventing effect is excellent but other rubber properties are adversely affected.

The anionic water-soluble polymer used in the present invention and the substance that causes coacervation under acidic conditions include polyvinyl pyridine, polybenzylaminoethyl cellulose, polydiethylaminoethylstyrene, polyvinylbenzylamine, and other acidic polymers, dodecyltrimethylamine. , Coconut alkyl dimethylamine, cured tallow alkyl dimethyl amine, polyoxyethylene tallow alkyl propylene diamine, dodecyl triethanol amine, coco alkyl amine, dodecyl amine, tallow alkyl amine,
Examples thereof include cationic surfactants such as acetates, hydrochlorides, sulfates, dimethylsulfates, nitrates and quaternary ammonium salts of higher amines such as cetylamine, stearylamine, hardened tallow alkylamine and the like. These substances are 0.1 to 10 parts by weight based on 100 parts by weight of chloroprene rubber,
It is preferably used in the form of an aqueous solution in the range of 1 to 5 parts by weight.

In the present invention, a mixture of a sulfur-modified chloroprene rubber latex, a sulfur compound and an anionic water-soluble polymer is mixed with an aqueous solution of a cationic water-soluble polymer or a cationic surfactant to give the chloroprene rubber a powder. Can be separated.

The powdery sulfur-modified chloroprene rubber obtained by the above operation can be easily dehydrated using a centrifuge or the like, and can be easily ground by a light grinding operation.

Next, it is dried, but the drying method is not particularly limited, and methods such as ventilation drying, hot air drying, vacuum drying, and fluidized drying can be freely selected and used.

4) Examples Hereinafter, examples will be shown and described, but the present invention is not limited thereto.

Method for producing sulfur-modified chloroprene rubber litex used in Examples A) Method for producing sulfur-modified chloroprene rubber latex (abbreviated as R-22) Chloroprene and other chemicals were added to a stainless steel reactor having an internal volume of 10 by the polymerization recipe shown in Table 1. Was charged, and polymerization was carried out at 40 ° C. in a nitrogen stream using calcium persulfate as a catalyst. When the conversion reached 84%, dimethylammonium dimethyldithiocarbamate was dissolved in water to stop the reaction, and then an emulsion containing 20% by weight of tetraethylthiuramyl sulfide was added, and the temperature was raised to 40 ° C., followed by deflocculation for 5 hours. Litex steam distillation was performed to remove unreacted monomers, and a sulfur-modified chloroprene rubber latex having a dry weight of 35% was obtained.

B) Copolymerized sulfur modified chloroprene rubber litex (R
(Abbreviated as "-10") Chloroprene and other chemicals were charged in a polymerization reactor shown in Table 1 in a stainless steel reactor having an internal volume of 10 and polymerization was carried out in a nitrogen stream using potassium persulfate as a catalyst. Less than
By the same operation as in (A), a copolymerized sulfur-modified chloroprene rubber latex having a dry weight of 35% was obtained.

Examples 1 to 7 Powder rubbers containing a sulfur compound dispersed therein were manufactured according to the following formulations using the combinations of the reagents shown in Table-2.

To 3000 g of rubber latex, 1050 g of a 1% aqueous solution of an anionic water-soluble polymer (sodium carboxymethyl cellulose: abbreviated as CMC) and a sulfur compound (5% water slurry) were added and mixed, and the pH was adjusted to 6.3 with an aqueous acetic acid solution. . Next, this mixed solution was added with a 0.5% aqueous solution of a higher amine acetate (polyoxyethylene beef tallow alkyl propylene diamine: abbreviated as N-DT203) 4200.
It was added to g with stirring.

The rubber separated in powder form.

Then, it was dehydrated by a centrifuge and further dried by a fluidized dryer to obtain a rubber powder.

The obtained rubber powder was blended according to the formulation shown in Table 3, and Mooney scorch measurement (method described in JIS K 6300) and rheometer measurement (150 ° C Monsanto ARC).
± 1 °). The results are shown in Table-2 and Figure-1.

It can be seen that the powder rubbers of Examples 1 to 7 have a long Mooney scorch time and are excellent in preventing scorch. Further, it can be seen from the rheometer vulcanization curve that the powder rubbers of Examples 1 and 2 are excellent in preventing scorch.

Comparative Examples 1 and 2 Powder rubbers were produced with the same formulation as in Examples. However, the sulfur compound was not added to the rubber latex, but was dry blended with the dried powder rubber. Therefore, a powder rubber was obtained in which the sulfur compound was not dispersed and contained inside the powder rubber, and the sulfur compound was present outside the powder rubber.

The obtained rubber powder was blended according to the formulation shown in Table 3, and Mooney scorch measurement (method described in JIS K 6300) and rheometer measurement (150 ° C Monsanto ARC ±
1 °). The results are shown in Table-2 and Figure-1.

It can be seen that the powder rubbers of Examples 1 to 7 have a longer Mooney scorch time than the powder rubbers of Comparative Examples 1 and 2 and are excellent in preventing scorch. Also, from the rheometer vulcanization curve, it is also excellent in preventing scorch.

[III] Effect of the Invention As described above, a novel powdery sulfur-modified chloroprene rubber obtained by dispersing and containing a sulfur compound selected from thyliums, thiazoles, and sulfenamides in the powder rubber of the present invention is A rubber powder that is excellent in preventing scorch.

[Brief description of drawings]

FIG. 1 shows the rheometer vulcanization curves of the powder rubbers of Examples and Comparative Examples.

Claims (2)

[Claims] 1. A powdery sulfur-modified chloroprene rubber containing a sulfur compound selected from thiurams, thiazoles and sulfenamides in an amount of 0.05 to 10 parts by weight per 100 parts by weight of sulfur-modified chloroprene rubber. Powder rubber made from. 2. Anionic or nonionic sulfur-modified chloroprene rubber latex containing 0.05 to 10 parts by weight of a sulfur compound selected from thiurams, thiazoles and sulfenamides per 100 parts by weight of sulfur-modified chloroprene rubber. And an anionic water-soluble polymer are mixed, and then the mixture is added to the anionic water-soluble polymer and an aqueous solution of a cationic water-soluble polymer or a cationic surfactant which causes coacervation under acidic conditions. A method for producing a powdery rubber, wherein the above sulfur compound is dispersedly contained in a powdery sulfur-modified chloroprene rubber, which is characterized by mixing.