JPH0140844B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving the cohesiveness of powdered rubber during storage. For more details,
A rubber latex containing an anionic water-soluble polymer is added dropwise to a cationic water-soluble polymer or a cationic surfactant aqueous solution under acidic conditions, and then a fatty acid soap and polyester are added to the powdered rubber slurry containing a synthetic resin emulsion. The present invention relates to a method for producing powdered rubber which prevents agglomeration of powdered rubber during storage and has improved fluidity, characterized by treatment with aluminum chloride. In recent years, with the advancement of rubber processing technology, rubber in the form of pellets or powder, which can be automatically measured and processed continuously, is in high demand and attracting attention in the market for the purpose of saving labor and energy.
Furthermore, with the expansion of its uses, rubber is often blended with various resins and is also used as a modifier for resins. Resins, such as polyvinyl chloride, are often in the form of powders or pellets, and therefore, the rubber used as the modifier described above should be in the form of powders in consideration of mixability and dispersibility. desirable. Furthermore, various rubber latexes have been used as asphalt modifiers, but latexes have the disadvantage of requiring a large amount of energy to remove water. In this case as well, there is an increasing demand for a powdered rubber that has almost no difference in dispersibility and does not require the removal of water. However, due to its nature, rubber is sticky even at room temperature and has high elasticity, so even once it is made into pellets or powder, it usually sticks to each other during processes such as drying and storage and becomes blocks. It is. For this reason, various studies have been made on methods to obtain powdered rubber that does not stick to each other and form blocks. General methods include physically or mechanically pulverizing the rubber and then adding an anti-agglomerating agent such as calcium carbonate or talc, and a physical method that uses a rubber latex coagulant such as a polyvalent metal salt to turn the rubber into powder. There are two types of chemical methods that involve separation and then isolation. In the former method, it is difficult to obtain powdered rubber with small particle size and uniformity due to the heat generation of the rubber during crushing, and the throughput is also limited. Furthermore, it has the disadvantage that a large amount of anti-aggregation agent is required to prevent the powder rubber from agglomerating. On the other hand, the latter case is disadvantageous because a large amount of inorganic salts are mixed into the powdered rubber, which impairs the stability of the powdered rubber. Taking these points into consideration, the present inventors conducted various studies regarding the method of powderizing rubber, and as a result, found that
First, Japanese Patent Publication No. 57-9562 (Patent Application No. 1951)
No. 148732), we have invented a method for producing powdered rubber that is essentially free of inorganic substances. According to this method, an anionic water-soluble polymer is mixed with rubber latex, and this is mixed with a cationic water-soluble polymer or a cationic surfactant that causes coacervation with the anionic water-soluble polymer under acidic conditions. A powdered rubber can be produced by mixing dropwise into an aqueous solution to separate the rubber into powder, then adding a synthetic resin as an emulsion, followed by dehydration and drying. It has been found, however, that the dry powder rubber thus obtained loses its flowability during storage, especially storage under load, and has poor flowability. For example, if stored under no load in a constant temperature room at 23℃, there will be no change in fluidity and the powder form will remain even after one month;
If it is stored in a bag (equivalent to a bag), it will turn into castella-like blocks after 24 hours, lose its fluidity, and will not return to its original uniform particle size powder even if it is re-pulverized, making it difficult to store or transport powdered rubber at low temperatures. It has been found that this method is industrially disadvantageous in that it requires packaging that does not carry any load. Taking these points into consideration, the inventors of the present invention conducted extensive studies to prevent the agglomeration of powdered rubber during storage ^.
The present invention led to the invention of an industrially advantageous method for producing powdered rubber with improved fluidity, which can be stored and transported in the same manner as conventional rubber that retains its powder form even during summer storage. The present invention uses anionic or nonionic rubber latex and 0.1 to 0.1 per dry weight of the rubber latex.
A mixture of 10% by weight of an anionic water-soluble polymer is added under acidic conditions, and a cationic water-soluble polymer that coacervations with the anionic water-soluble polymer or a cationic surfactant is added to the dry weight of rubber latex. 1 to 30% by weight based on the dry weight of the rubber latex.
It is characterized by adding 0.2 to 3% by weight of fatty acid soap based on the dry weight of the rubber latex to the powdered rubber slurry liquid obtained by adding the rubber latex, and further treating with polyaluminum chloride of 0.1 to 2% by weight based on the dry weight of the rubber latex. The present invention relates to a method for producing powdered rubber that prevents agglomeration of powdered rubber during storage and has improved fluidity without agglomeration even when stored under load. The polyaluminum chloride used in the present invention is an inorganic polymer having the composition formula (Al) _o (OH) _n Cl _3o-n , has various degrees of polymerization, and is industrially produced (for example, Toyo Soda Co., Ltd.). Manufactured by Kogyosha, product name
PAC) and are readily available. In addition, polyvalent metal salts are used as coagulants for latex, and polyaluminum chloride is also used as a coagulant for latex.
As seen in No. 137241, polyaluminum chloride is used as a coagulant to separate rubber from rubber latex into powder, but the use of polyaluminum chloride in the present invention is essentially different from these. That is, polyaluminum chloride in the present invention is produced by separating rubber from rubber latex into powder, then adding synthetic resin as an emulsion, adding fatty acid soap to a powdered rubber slurry liquid, and treating this with polyaluminum chloride. Used in the process. As shown in the specification, when polyaluminum chloride is used as a coagulant for rubber as in JP-A-53-137241, the fluidity of wet rubber powder containing water is maintained, but the dry powder is In order to impart fluidity to rubber, it is desirable to add an anti-agglomerating agent such as silica or talc after separate dehydration and before or during drying. , there is no description. In the present invention, it is essential to add synthetic resin and fatty acid soap before adding polyaluminum chloride, and by skipping this step, dehydration and drying are easy and storage under load is possible. The company succeeded in producing powdered rubber with no change in fluidity. There is no point in simply adding polyaluminum chloride to an aqueous dispersion obtained by separating rubber into powder; in such a case, if you dehydrate it under a load, the rubber will agglomerate into lumps, turning the rubber into powdered rubber. You can't get it as. The rubber targeted in the present invention can be any rubber as long as it can be obtained as an anionic or nonionic latex, including natural rubber (NR), isoprene produced by conventional emulsion polymerization method, butadiene, Polyisoprene rubber (IR), polybutadiene rubber (BR), polychloroprene rubber (CR), which are homopolymers of conjugated diene compounds such as chloroprene, the above conjugated diene compounds and styrene, acrylonitrile, vinylpyridine,
Styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), vinylpyridine butadiene styrene rubber, acrylic acid butadiene rubber, methyl acrylate butadiene rubber, which is a copolymer with vinyl compounds such as acrylic acid, methacrylic acid, alkyl acrylate, and alkyl methacrylate. Rubber, methyl methacrylate butadiene rubber, etc., as well as ethylene, propylene,
Examples include isobutylene isoprene rubber (IIR), which is a copolymer of olefins such as isobutylene and a conjugated diene compound. Examples of anionic water-soluble polymers used in the present invention include natural products such as sodium alginate, gum arabic, carrageenan, agar, sodium carboxymethyl cellulose, polyvinyl sulfonic acid, polystyrene sulfonic acid, acrylic acid/methyl acrylate copolymer, There are synthetic products such as methacrylic acid/methyl methacrylate copolymer, crotonic acid/vinyl acetate copolymer, styrene/maleic acid copolymer, cellulose acetate phthalate, and starch acetate phthalate, and these water-soluble polymers are used in rubber latex. relative to dry weight
It is used in a range of 0.1 to 10% by weight, preferably 1 to 5% by weight, and is mixed in the form of an aqueous solution. The anionic water-soluble polymer used in the present invention and the substance that causes coacervation under acidic conditions are acidic and soluble in water, such as polyvinylpyridine, polybenzylaminoethylcellulose, polydiethylaminoethylstyrene, and polyvinylbenzylamine. Cationic water-soluble polymers, dodecyltrimethylamine, cetyltrimethylamine, stearyldimethylbenzylamine, dodecyldimethylbenzylamine, coconut alkyldimethylamine, hardened tallow alkyldimethylamine, polyoxyethylene tallow alkylpropylene diamine, dodecyltriethanolamine, coconut Cationic surfactants such as acetates, hydrochlorides, sulfates, dimethyl sulfates, nitrates, quaternary ammonium salts of higher amines such as amines, dodecylamine, tallow alkylamine, cetylamine, stearylamine, hardened tallow alkylamine, etc. etc. These substances are used in the form of an aqueous solution in a range of 0.1 to 10% by weight, preferably 1 to 5% by weight, based on the dry weight of the rubber latex. In the present invention, first, a mixture of the rubber latex and anionic water-soluble polymer is mixed dropwise under acidic conditions into an aqueous solution of the substance that causes coacervation with the anionic water-soluble polymer, thereby powdering the rubber. It can be separated into two parts. In order to effectively separate powders, there is a suitable ratio between the anionic water-soluble polymer and the substance that causes coacervation, but this can be easily determined through preliminary experiments. Can be done. Powder separation can only occur under acidic conditions, and the pH of the powder separation system should be acidic, preferably 5.
Must be kept below. Acids used for this purpose include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid, but there are no restrictions on the method of adding these acids.
As long as the PH is kept acidic. This operation can be easily and well controlled by simply mixing each solution under stirring, and the rubber immediately separates into powder. In this case, it is affected by the amount of water in the solution or the strength of stirring, but these are not important factors, and the suitable amount of water or strength of stirring can be easily determined in each case by conducting preliminary experiments in advance. The powdered rubber obtained at this stage can be easily separated and washed using a cotton cloth, etc. However, if it is dehydrated under load, it tends to turn into blocks after dehydration, and the rubber cannot be left in a powdered state. difficult to obtain. In the present invention, this problem was solved by adding a synthetic resin as an emulsion. By adsorbing the synthetic resin to the surface of the powdered rubber particles, adhesion between the rubber particles is prevented, and a fluid and wet material is created. Can be made into powdered rubber. The synthetic resin emulsion used herein refers to an emulsion in which synthetic resin particles having a glass transition temperature of 30° C. or higher are dispersed in an aqueous medium. Such synthetic resin emulsions include polystyrene emulsion, polymethyl methacrylate emulsion, methyl methacrylate/methyl acrylate copolymer emulsion, polyvinyl chloride emulsion, vinyl chloride/vinylidene chloride copolymer emulsion, and polyvinyl acetate emulsion. , styrene/acrylonitrile copolymer emulsion, styrene/itaconic acid copolymer emulsion, styrene/methyl methacrylate copolymer emulsion, styrene/vinyl chloride copolymer emulsion, fluororesins such as polyvinyl fluoride and polychlorotrifluoroethylene. There are emulsion etc. These synthetic resin emulsions have a dry weight of 1 to 30% of the dry weight of rubber latex.
It is added in an amount of 2 to 15% by weight, preferably 2 to 15% by weight. If the amount of synthetic resin is less than 1% by weight, it is difficult to obtain a sufficient effect and tends to form blocks, and if it is used in excess of 30% by weight, the properties as a rubber will be impaired. undesirable for this reason. In order to sufficiently adsorb the synthetic resin particles onto the surface of the powdered rubber particles, it is necessary to mix thoroughly after adding the synthetic resin emulsion, but stirring for 10 minutes or more is sufficient. Furthermore, for the purpose of rapid and sufficient adsorption, inorganic electrolytes such as sodium chloride, potassium chloride, sodium sulfate, calcium chloride, magnesium sulfate, zinc sulfate, and aluminum chloride, or lower alcohols such as methanol and ethanol are used. , acetone, etc. may be added. These additives can be easily removed by washing the powdered rubber with water after isolating the powdered rubber using a suitable method, and are not contained in the final powdered rubber. Next, it is easily dehydrated using a centrifuge or the like, but at this point, it does not stick to each other and form blocks, and it is a wet material that is fluid or can be easily crushed by a light crushing operation. A powdered rubber is obtained. Furthermore, it is possible to obtain a free-flowing dry powder rubber with a diameter of approximately 2 mm or less by fluidized drying, etc. However, such powder rubber can be produced under a load equivalent to a 20 kg bag or 8 bags (approximately 48 g/dry powder).
cm ² ) and stored at 35°C, it turned out to form a castella-like block after 24 hours. Even if these are re-pulverized, they do not return to the original powdered rubber, making it difficult to use them as a powdered rubber material and being industrially disadvantageous. In order to improve this point, as a result of intensive research, we added fatty acid soap and polyaluminum chloride to the powdered rubber slurry liquid containing synthetic resin emulsion while maintaining the pH at an acidic level. This was a successful production of powdered rubber that does not cohere with each other. The fatty acid soap used here has 12 carbon atoms.
These are sodium salts, potassium salts, etc. of fatty acids having a concentration of 20 to 20, and the fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., and these include the dry weight of rubber latex. 0.2-3 against
It is used in an amount of 0.5% to 2% by weight. It is preferable to use fatty acid soap in the form of an aqueous solution, but since the solubility in water is limited depending on the type of fatty acid soap, in this case, the purpose is to disperse the fatty acid soap quickly and uniformly. It is desirable to raise the powder rubber slurry liquid to the melting temperature of the fatty acid soap. These temperatures can be easily found from literature. After the addition of these fatty acid soaps, polyaluminum chloride may be added immediately or in parallel, but considering that the aqueous solution of fatty acid soaps is essentially alkaline, the pH of the powdered rubber slurry liquid should be
For the purpose of maintaining acidity, it is neutralized with inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, organic acids such as acetic acid, or polyvalent metal salts such as calcium chloride, barium sulfate, zinc sulfate, and magnesium chloride. Polyaluminum chloride may be added after the addition of polyaluminum chloride. The polyaluminum chloride used here is preferably 0.1 to 3% by weight based on the dry weight of the rubber latex.
It is used in a range of 0.2 to 1% by weight. In the present invention, these are both necessary components, and if the fatty acid soap is less than 0.2% by weight and polyaluminum chloride is added, or if treated with the fatty acid soap alone, a free-flowing powder rubber can be obtained by drying. However, it is not possible to prevent agglomeration of powdered rubber during storage under load. In addition, using more than 3% by weight of fatty acid soap and more than 3% by weight of polyaluminum chloride may cause a delay in vulcanization of the rubber or worsen the stability of the rubber, which may affect the properties of the rubber. It is not desirable because it damages the The powdered rubber slurry thus obtained can be easily dehydrated using a centrifugal separator or the like to obtain a wet powdered rubber that is fluid or can be easily crumbled by hand. Next, 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. The present invention is a method for producing powdered rubber that does not agglomerate during storage under load, having the above-mentioned structure. It can be easily and quickly manufactured. In the present invention, the cohesiveness of powdered rubber under load is determined by filling a box with approximately 130g of dry powdered rubber into a box measuring 60mm in length and width and 70mm in depth, and applying a load to the bottom of a 20Kg bag and a stack of 8 bags. It is stored at 35℃ for 24 hours under a corresponding force of 48 g/ ^cm2 , and then taken out of the box and broken into powdered rubber, and the particle size of the powdered rubber before and after storage. I evaluated it. Examples will be described below, but the invention is not limited thereto. In the examples, unless otherwise stated, parts and percentages represent weight. Rubber latex and synthetic resin emulsion (A) used in Examples Polychloroprene rubber latex (abbreviated as CR) 4.0 parts of rosin potassium soap, 0.4 parts of caustic soda, and 0.4 parts of formaldehyde-sodium naphthalene sulfonate condensate were mixed with water in a nitrogen stream. Dissolved in 100 parts,
Next, 0.2 parts of n-dodecyl mercaptan, 2,6
Chloroprene in which 0.1 part of -di-t-butyl-p-cresol was dissolved was added and emulsified, and polymerization was carried out at 40°C while dropping a 1% aqueous solution of potassium persulfate. The polymerization was stopped at a conversion rate of 70%, and unreacted chloroprene was distilled off to obtain a polychloroprene rubber latex with a dry weight of 35%. (B) Acrylonitrile-butadiene rubber latex (abbreviated as NBR) High-acrylonitrile-butadiene rubber latex (trade name: Nipol 1571) manufactured by Nippon Zeon Co., Ltd. was adjusted to have a dry weight of 35%. (C) Polybutadiene rubber latex (abbreviated as BR) Polybutadiene rubber latex (trade name JSR0700) manufactured by Japan Synthetic Rubber Co., Ltd. was adjusted to have a dry weight of 35%. (D) Styrene-butadiene rubber latex (abbreviated as SBR) Styrene-butadiene rubber latex (trade name JSR0561) manufactured by Japan Synthetic Rubber Co., Ltd. with a dry weight of 35%.
I adjusted it so that (E) Polymethyl methacrylate emulsion (abbreviated as PMMA) In a nitrogen stream, 7.5 parts of sodium alkylaryl polyoxyethylene sulfonate and 0.75 parts of sodium dodecylbenzenesulfonate were dissolved in 200 parts of water, and then 150 parts of methyl methacrylate was dissolved. In addition, polymerization was carried out at 75°C using potassium persulfate as an initiator.
The dry weight of the polymethyl methacrylate obtained is
It was 42%. (F) Polyvinyl chloride emulsion (abbreviated as PVC) Polyvinyl chloride emulsion (trade name: Geon 150×15) manufactured by Nippon Zeon Co., Ltd. was used. Dry weight is 50
It was %. (G) Polystyrene emulsion (abbreviated as PSt) 7.5 parts of sodium alkylarylpolyoxyethylene sulfonate and 0.7 parts of sodium lauryl sulfate are dissolved in 100 parts of water in a nitrogen stream, and then styrene 65
of the mixture was added, and polymerization was carried out at 70°C using potassium persulfate as an initiator. The dry weight of the resulting polystyrene emulsion was 40%. Examples 1 to 6 Powdered rubber was produced using the combinations of reagents shown in Table 1. That is, 285 parts of rubber latex was mixed with a 1% aqueous solution of anionic water-soluble polymer.
Add 200 parts and mix until a homogeneous solution, 10%
Aqueous acetic acid solution was slowly added to adjust the pH to 6.3. Next, this mixed solution was poured into 900 parts of an acidic aqueous solution containing 2 parts of higher amine acetate at room temperature with vigorous stirring, and the rubber was immediately separated into powder. The pH after powder separation was 4.9. Next, a synthetic resin emulsion was added in an amount of 5% by weight based on the dry weight of the rubber latex, and mixing was continued for about 10 minutes. Approximately
The mixture was heated to 50°C, and the fatty acid soaps shown in Table 1 were added at the respective ratios, and the mixture was neutralized with equimolar amount of hydrochloric acid.
Subsequently, polyaluminum chloride was added in the respective proportions and mixing continued for 30 minutes. After separating and washing with a cotton cloth, the mixture was dehydrated by centrifugation to obtain a wet powder rubber that could be easily powdered by hand. Then, it was dried in a fluidized fluid dryer to obtain a powdered rubber having a uniform particle size as shown in Table 2. When these powdered rubbers were stored under load at 35° C. for 24 hours, their cohesiveness was evaluated. As shown in Table 2, they could be easily broken down by hand, indicating that they were hardly cohesive. Furthermore, the particle size after storage was almost unchanged from before storage, indicating that the properties as a powdered rubber were not impaired. As shown in the comparative example, when treatment with fatty acid soap and polyaluminum chloride was not performed,
When only treated with fatty acid soap and further only treated with polyaluminum chloride, when stored under load at 35℃ for 24 hours, it aggregates in a castella-like shape after storage and is impossible to break. It can also be seen that even if it could be destroyed, it would not turn into the powder state before storage and would lose its properties as a powdered rubber.

【table】

【table】

[Table] Example 7 100 parts of a 1% aqueous solution of sodium carboxymethylcellulose was added to 100 parts of CR latex and mixed to form a homogeneous solution. Add 10% acetic acid aqueous solution
After adjusting the pH to 6.3, this mixed solution was poured into 500 parts of a 0.2% acidic aqueous solution of polyvinylpyridine hydrochloride at room temperature with vigorous stirring, and the rubber was separated into powder. PMMA emulsion was added at 6% by weight based on the dry weight of the rubber latex and mixing was continued for 10 minutes. Next, the temperature was raised to about 50°C to dissolve 0.7 parts of sodium stearate, and polyaluminum chloride (trade name: PAC, solid content of about 10
%, manufactured by Toyo Soda Co., Ltd.) was added and mixing was continued for 30 minutes. After separating with a cotton cloth and dehydrating with a centrifuge after washing, a wet powder rubber which can be easily crushed was obtained. It was then dried to obtain a dry powder rubber of 96.1% less than 20 mesh. This powdered rubber was applied under a load of 35℃ (48g/
cm ² ), and when stored for 24 hours, the powder moldings showed no load
It crumbles easily at 3.0Kg, and the powder quality is less than 20mesh.
It was 95.7%, almost unchanged from before storage. Comparative Example 4 Rubber was separated into powder from CR latex in the same manner as in Example 1. The pH after powder separation is 4.9, and polyaluminum chloride (manufactured by Toyo Soda Co., Ltd., trade name PAC, solid content approximately 10%) is added to this powder separation liquid.
Added a section. When the thus obtained powdered rubber slurry liquid was dehydrated using a centrifugal separator, the rubber turned into blocks and powdered rubber could not be obtained.

Claims (1)

[Claims] 1 Rubber latex containing an anionic water-soluble polymer is placed under acidic conditions in an aqueous solution of a cationic water-soluble polymer or a cationic surfactant that causes coacervation with the anionic water-soluble polymer under acidic conditions. A method for preventing agglomeration of powdered rubber during storage, characterized in that a powdered rubber slurry obtained by dropping and mixing and then adding a synthetic resin as an emulsion is treated with fatty acid soap and polyaluminum chloride.