JPS5949249B2 - Manufacturing method of powdered rubber - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing powdered rubber.

Specifically, it relates to a method for preventing stickiness of powdered rubber by treating a coagulated rubber latex coagulated with a coagulant other than a trivalent metal salt with a carboxylate soap in the presence of a trivalent metal salt. It is. Industrial methods have already been established in which rubber latex and oil emulsion are coagulated with acid, dehydrated and dried to obtain a block of rubber, which is then pressed into a bale shape and packaged with polyethylene film to produce a product. It has been implemented.

In this method, the rubber sticks during dehydration and drying, causing the rubber to form into blocks.In order to further form blocks during storage and transportation, the rubber is packaged in a bale shape with polyethylene film, etc. It is. When such bales of rubber are used in rubber processing plants such as tire manufacturing plants, the bales must be shredded for purposes such as automatic metering of the rubber.

Therefore, if this kind of rubber is supplied in the form of powdered rubber, the trouble of shredding at the rubber processing factory will be eliminated.
Not only does it make automatic weighing easier, it also eliminates sulfur and
Antiaging agents, vulcanization accelerators, carbon black, silica, and other rubber compounding agents can be dry-blended and connected directly to the extruder, making it possible to significantly shorten the rubber product manufacturing process. Powderization of rubber has great industrial significance. The present inventors have conducted various studies on a method for advantageously producing powdered rubber from rubber latex and, if necessary, a suitable oil or the like added thereto.

As a result, it was found that there were significant differences in the blocking properties of powdered rubber depending on the type of emulsifier contained in the rubber latex, and that the fine mixture obtained by coagulating rubber latex (hereinafter referred to as "grams") The present invention was achieved based on new findings such as the fact that the blockability can be significantly improved by treatment with carboxylate soap. That is, in the present invention, a coagulant other than a trivalent metal salt is added to a rubber latex containing a carboxylate soap as an emulsifier to coagulate a gram, and a carboxylate soap is added to the gram to form a trivalent metal salt. This is a method for producing powdered rubber, characterized by coagulating carboxylate soap on the surface of the gram in the presence of a powder, separating the gram thus obtained from the coagulation mother liquor, and drying it.

Conventionally, known methods for pulverizing rubber include, for example, immersing granular rubber in an aqueous resin dispersion, or spraying an aqueous resin dispersion onto the granular rubber, and then drying.
(See Japanese Patent Publication No. 49-11460).

However, when this powdering method is applied to powdered rubber that is a coagulated product from rubber latex, it tends to become blocked during the drying process, and even if the blocked product is forcibly powdered, it becomes blocked again during storage. Its storage properties are almost the same as those without resin treatment. In addition, after coagulating the rubber latex, a small amount of hard polymer latex such as polyvinyl chloride or polystyrene is added to it, and the hard polymer is coagulated on the surface of the first coagulated material, washed with water, and dried to produce powder rubber. A method has already been proposed (see Japanese Patent Publication No. 46-13626).

According to such known methods, it is possible to considerably prevent the formation of blocks in powdered rubber, but there are various problems such as mixing of non-rubber hard polymer components into the rubber, which tends to change the properties of the rubber. The rubber latex used in the present invention contains carboxylate soap as its emulsifier.

This is because when carboxylate soap as an emulsifier is coagulated with a coagulant other than a trivalent metal salt, free carboxylic acid or a divalent metal salt of a carboxylic acid is produced, and this is caused by the formation of gram particles that are precipitated at the same time. This is because it is used to coat the surface and to help prevent the powdered rubber from becoming blocky. Such coating effects cannot be obtained when using rubber latexes containing emulsifiers other than carboxylate soaps, such as higher alcohol sulfate salts, alkylbenzene sulfonate salts, nonionic surfactants, and cationic surfactants. The anti-blocking property is poor. The emulsifier carboxylate soap in the present invention refers to alkali metal salts, ammonium salts, etc. of carboxyl group-containing compounds having surface activity.

For example, from soaps of fatty acids (preferably saturated or unsaturated carboxylic acids having 6 to 22 carbon atoms), rosin acid soaps, disproportionated rosin acid soaps, tall oil soaps, α-olefin monomaleic anhydride copolymers. Examples include derived carboxylic acid soaps and carboxylic acid soaps derived from dicyclopentadiene-maleic anhydride reaction products. The amount of carboxylate soap used in rubber latex is usually 2 to 15 parts by weight, preferably 5 to 10 parts by weight, based on 100 parts by weight of rubber. The rubber latex in the present invention is produced by emulsion polymerization of monomers or monomer mixtures such as butadiene, butadiene-styrene, butadiene-acrylonitrile, butadiene-isoprene, isoprene, chloroprene, etc. using the above-mentioned carboxylic hydrochloride soap as an emulsifier. It can be easily obtained by Particularly preferred is a latex of butadiene rubber or butadiene-styrene copolymer rubber, which is used as a general-purpose rubber. In some cases, natural rubber latex,
A rubber solution obtained by solution polymerization or a recovered solid rubber as a raw material, which is re-emulsified in water with carboxylate soap or newly emulsified, can also be used as the rubber latex of the present invention. I can do it. In the present invention, oil can be further mixed with the rubber latex if desired. Such oils are preferably those normally used as rubber extender oils, such as aroma oils, naphthenic oils, and paraffin oils. The amount of oil added is 70 parts by weight or less per 100 parts by weight of rubber. As for the method of adding oil, it is preferable to add the oil by emulsifying it with water using carboxylate soap. In the present invention, coagulants other than trivalent metal salts are used to coagulate the mixture of rubber latex and optionally added oil.

For example, free acids, divalent metal salts, etc. may be used alone or in combination. Examples of free acids include inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, and organic acids such as acetic acid. The amount of acid coagulant to be used is sufficient as long as the pH of the mixed solution is in the acidic range, and is usually in the range of 1 to 6, preferably 3 to 5.
This is the amount to make. Examples of divalent metal salts include calcium chloride, calcium bromide, calcium sulfate, calcium nitrate, magnesium chloride, magnesium sulfate, zinc sulfate, zinc chloride, barium chloride, etc., but from a practical standpoint, calcium chloride, zinc sulfate, etc. More water-soluble metal salts are preferred.

The amount used may be equivalent to that of the carboxylate soap in the rubber latex. Note that it is effective to add a monovalent metal salt such as sodium chloride or potassium chloride as a creaming agent prior to the coagulation treatment using the coagulant in order to stabilize the coagulation operation.

When the rubber latex is coagulated according to the present invention, the rubber is coagulated as particulate grams, and at the same time, the carboxylate soap in the rubber latex is also coagulated by the coagulant to produce free carboxylic acid or divalent metal salt of carboxylic acid, etc. The gram particles are thereby primarily coated.

The size of the gram particles generated at this time is usually 5 mm.
Hereinafter, it preferably has a particle size of about 1 ml or less, and the powdered rubber in the present invention refers to particles of this size. In the present invention, a carboxylate soap is then added to the gram particles that are primarily coated with free carboxylic acid or a divalent metal salt of a carboxylic acid, and then a trivalent metal salt is added. The carboxylate soap is coagulated in the presence of a carboxylic acid and the grams are recoated (secondary coated) with a trivalent metal salt of a carboxylic acid.

As the carboxylate soap, the same carboxylate soap as used as an emulsifier for rubber latex is used. The carboxylate soap solution is added to the gram by directly adding the carboxylate soap solution to the gram separated from the primary coagulation mother liquor by filtration, or by adding the carboxylate soap solution to the gram that has been slurried with water or an aqueous solution of a trivalent metal salt. Added. The amount of carboxylate soap added is 1 to 10 parts by weight, preferably 2 to 6 parts by weight, per 100 parts by weight of rubber. Trivalent metal salts added for coagulation of carboxylate soaps include water-soluble trivalent metal salts such as aluminum sulfate, aluminum chloride, aluminum nitrate, ferric sulfate, ferric chloride, and ferric nitrate. Preferably, it is usually used as a 5-20% aqueous solution.

The amount used may be at least equivalent to that of the carboxylate soap added during secondary coagulation, but it is usually used in an equivalent amount to about three times the amount. When a carboxylate soap is coagulated, if the amount of trivalent metal salt is insufficient, the carboxylate soap will not be liberated and will remain in the form of an alkali metal salt or ammonium salt type soap, resulting in the formation of powder. Conditions that prevent carboxylic acid salts from remaining in the form of alkali metal salt or ammonium salt type soaps, i.e., trivalent metal salts of carboxylic acids (so-called metal soaps), as they cause various problems during rubber processing. Solidify under conditions such that it takes the form of The thus obtained gram coated with the trivalent metal salt of carboxylic acid is subjected to post-treatments such as filtration, water washing, and filtration, and then dried to obtain the desired powdered rubber.

The powdered rubber of the present invention obtained in this way does not become blocky even when compressed under its own weight during heating, storage, or transportation, and it does not form blocks when it is rolled during processing of powdered rubber. The windability is also good.

This is because the powdered rubber particles obtained by the production method of the present invention are coated with a free carboxylic acid or a divalent metal salt of a carboxylic acid that is generated during the primary coagulation with a free acid or a divalent metal salt, and a coating with a trivalent metal salt. It is presumed that this is because the rubber particles do not come into direct contact with each other due to the coating treatment with the trivalent metal salt of carboxylic acid produced during secondary coagulation with the salt. Furthermore, since there is no risk that the powdered rubber will become blocky during drying, there is an advantage that highly efficient drying methods such as powder fluidized drying and flash drying can be employed. In addition, the trivalent metal salt of carboxylic acid that coats the surface of the powdered rubber of the present invention exhibits similar properties to calcium stearate, etc., which are used as additives for rubber compounding.・There is no need to worry about foreign substances or impurities forming in the application. This is also one of the major features of the present invention. Next, examples and reference examples will be given and explained.

Part and ? in these examples? Unless otherwise noted,
Weight part and weight? shows. Further, in these examples, the blocking test (measurement) of the powdered rubber after drying and its evaluation were carried out in the following manner. That is, 351! Add 159 powdered rubber into a cylinder of 0.251<g
After applying a load of /Cd and leaving it for 5 minutes, the load and cylinder were removed, and weights of various weights were placed on the obtained powder rubber moldings, and the load was applied at the time when the powder rubber moldings would collapse. The degree of blocking was evaluated, and the case where the shape collapsed without applying a load was rated 01, the case where the shape collapsed with a load of 1009 was rated 1, and the case where the shape collapsed with a load of 2009 was rated 2 (the same applies hereinafter). Example 1 SBR latex (styrene/butadiene = 2 by weight)
3/77, rubber content 22.2%, emulsifier is fatty acid soda/
This is a mixed soap containing sodium rosin acid = 1/1, and the amount of emulsifier is 6.5 parts per 100 parts of rubber.

) 1809 in a 21-capacity tank with a stirrer, and
After adding 150 d of 10% aqueous sodium chloride solution and stirring for 3 minutes, 10 TILI of 10% aqueous calcium chloride solution was added to produce grams. Then, the grams were filtered and thoroughly washed with water, and then put into a 21-volume tank equipped with a stirrer, and about 1,400 grams of warm water was added to form a gram slurry. After that, add KS soap (trade name, semi-cured beef tallow potash soap manufactured by Kao Atlas Co., Ltd.) 50 TILI (solid content 29
, corresponding to 5 parts of solids per 100 parts of rubber. and 1
0% aluminum sulfate aqueous solution 15a was added and stirring continued for an additional 10 minutes. The powdered rubber thus obtained was washed with water, filtered, and dried in a drier at a temperature of 80° C. for 3 hours, but no block formation occurred during drying.

The test evaluation of blockability was 3. Examples 2 to 4 In Example 1, 10% aqueous calcium chloride solution 10
Instead of mt, 10% zinc sulfate aqueous solution 14d110%
A powdered rubber was produced in the same manner as in Example 1, except that 12d of aqueous magnesium sulfate solution or 40wL1 of a 1% aqueous sulfuric acid solution was used.

The test evaluation of blockability of the obtained powdered rubber was 3 in the case of zinc sulfate, 4 in the case of magnesium sulfate, and 5 in the case of sulfuric acid. Example 5 In Example 1, in addition to carboxylate soap as an emulsifier for SBR latex, sodium naphthalene sulfonate/formalin condensate was added at 0.2 parts per 100 parts of rubber.
A powdered rubber was produced in the same manner as in Example 1, except that 6 parts of the powder was contained.

The test evaluation of the blockability of the obtained powdered rubber was 4.

Reference Examples 1 to 4 In Examples 1 to 4, when an attempt was made to carry out the same formulation without using KS soap, a blocking phenomenon was observed in the drying process and good powder rubber could not be obtained.

Reference Examples 5 to 7 In Example 1, KS soap 50m/! (soap part 2
9, equivalent to 5 parts per 100 parts of rubber), Pellex 0TR (sodium dialkyl sulfosuccinate),
Example 1 except that 5% aqueous solution 80a of Emulgen 920 (polyoxyethylene nonylphenol ether) or Cortamine 24p (lauryl trimethyl ammonium chloride), both manufactured by Kao Soap Co., was used.
When an attempt was made to produce powdered rubber in the same manner as above, a blocking phenomenon was observed in the drying process and a good powdered rubber could not be obtained.

Example 6 In Example 1, instead of SBR latex 1809, BR latex 187f! obtained by emulsion polymerization method was used. (
The rubber content is 21.4%, the emulsifier is a mixed soap of fatty acid soda and rosin acid soda, and the amount of emulsifier is 8 parts per 100 parts of rubber.
Department.

) Powdered rubber was produced in the same manner as in Example 1 except that the following was used. The test evaluation of the blockability of the obtained powdered rubber was 3. Example 7 In Example 1, the SBR latex and the oil emulsion obtained by emulsifying naphthenic oil 159 with tall oil soap were simultaneously charged into the stirring tank, and the amount of calcium chloride used was changed to 10 m11 and 10 m11 instead of 15 WLt. The amount of KS soap used is 707 instead of 50d! Lllll
Furthermore, the amount of aluminum sulfate aqueous solution used was increased to 15TnI1.
I changed it to 17d instead.

Claims (1)

[Claims] 1. Adding a coagulant other than a trivalent metal salt to rubber latex containing carboxylate soap as an emulsifier to coagulate a fine mixture of rubber (hereinafter referred to as "crumb"), A carboxylate soap is added to the crumb, the carboxylate soap is coagulated on the surface of the crumb in the presence of a trivalent metal salt, and the crumb thus obtained is separated from the coagulation mother liquor and dried. A method for producing powdered rubber.