JPH0422174B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECT OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing powdered rubber that has excellent dispersibility in asphalt, and more specifically, a powdered rubber that prevents agglomeration during storage and has improved fluidity. The present invention relates to a method for producing powdered rubber in which a foaming agent is dispersed within the powdered rubber. [Prior Art] Powdered rubber has been used not only for its original purpose but also for purposes that take advantage of its powdery nature, unlike veil-like or chip-like rubber. For example, asphalt used for bridge pavement and rooftop construction is modified by adding rubber. As a method for modifying asphalt, rubber latex containing about 50% water is generally added. This method requires a water evaporation operation, but when powdered rubber is used, this operation is unnecessary and is economical. Powdered rubber is also used as a modifying material for asphalt because it is advantageous because it does not transport excess water in the rubber latex. However, as a modification material for asphalt,
When powdered rubber was used, although the asphalt properties were improved to a certain extent, the asphalt properties were not sufficiently improved due to poor dispersion when mixed with asphalt. The present inventors have discovered that powdered rubber in which a blowing agent is dispersed in powdered rubber significantly improves the dispersibility in asphalt, and has developed powdered rubber and its manufacturing method.
It was completed first. 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 and becomes blocks during transportation, storage, etc. It is. [Problems to be Solved by the Invention] The purpose of the present invention is, for example, to solve the problem during storage.
A foaming agent dispersed inside powdered rubber with industrially advantageous improved fluidity that retains its powder form even under the load of 20kg bags and 8 bags (approximately 48g/cm ² ) and storage in the summer. Our objective is to provide powdered rubber that is Structure of the Invention [Means for Solving the Problems] As a result of extensive research aimed at providing a method for producing powdered rubber that overcomes these drawbacks, the present inventors have synthesized an aqueous dispersion of powdered rubber. The present invention was completed based on the discovery that powdered rubber added with a resin emulsion and dehydrated and dried prevents agglomeration during storage and significantly improves fluidity. [Function] The method for producing powdered rubber in which a blowing agent is dispersed inside powdered rubber, which prevents agglomeration during storage and has improved fluidity, according to the present invention, involves adding a blowing agent and an anionic aqueous solution to an anionic or nonionic rubber latex. and dropping the mixed solution under acidic conditions into an aqueous solution of a cationic water-soluble polymer or cationic surfactant that causes coacervation with the anionic water-soluble polymer under acidic conditions. This method is characterized by mixing, then adding a synthetic resin emulsion, and dehydrating and drying. The rubber targeted in the present invention can be any rubber that can be obtained as an anionic or nonionic latex, including natural rubber (NR),
Alternatively, polyisoprene rubber (IR), polybutadiene rubber (BR), polychloroprene rubber (CR), which is a homopolymer of conjugated diene compounds such as isoprene, butadiene, chloroprene, etc., the above conjugated diene compounds and styrene, acrylonitrile, vinylpyridine, acrylic Styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), vinylpyridine butadiene styrene rubber, methyl methacrylate butadiene rubber, which is a copolymer with a vinyl compound such as acid, methacrylic acid, alkyl acrylate, or alkyl methacrylate. , methyl methacrylate butadiene rubber, etc., and isobutylene isoprene rubber (IIR), which is a copolymer of olefins such as ethylene, propylene, isobutylene, and a conjugated diene compound.
etc. Examples of anionic water-soluble polymers 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. There are synthetic products such as methacrylate copolymer, crotonic acid-vinyl acetate copolymer, styrene-maleic acid copolymer, cellulose acetate phthalate, and starch acetate phthalate. These water-soluble polymers are contained in an amount of 0.1 to 10 parts by weight based on the dry weight of the rubber latex.
It is preferably used in an amount of 1 to 5 parts by weight, and is usually mixed in the form of an aqueous solution. If it is less than 0.1 parts by weight, coacervation will not be successful, and if it exceeds 10 parts by weight, side reactions will occur and it will be meaningless from an economic point of view. As the blowing agent used in the present invention, general ones used in various industries such as the rubber industry, resin industry, and food industry can be used. A blowing agent that generates a gas such as ammonia is preferable.Blowing agents can generally be divided into inorganic blowing agents such as baking soda and ammonium carbonate, and organic blowing agents such as nitroso compounds, azo compounds, and sulfonyl hydrazides. For example, N,N'-dinitroso pentamethylene tetramine, N,N'-dimethyl-N,N'-
Nitroso compounds such as dinitroso terephthalamide, azo compounds such as azodicarbonamide, azobis isobutyronitrile, azocyclohexyl nitrile, diazoaminobenzene, barium diazodicarboxylate, benzene sulfonyl hydrazide, toluene sulfonyl hydrazide, etc. There are sulfonyl hydrazides such as hydrazide, diphenylsulfone-3,3'-disulfonyl hydrazide, and P,P'-oxybis(benzenesulfonyl hydrazide). Although these blowing agents may be added to the rubber latex as they are, it is preferable to add them as an aqueous slurry. As a method for turning the foaming agent into a water slurry, it is preferable to disperse the foaming agent as fine particles as uniformly as possible in water using a colloid mill, a centrifugal pump, a high-speed mixer, or the like. Foaming agent water slurry concentration is 3-40
Parts by weight are used, preferably from 5 to 20 parts by weight.
These blowing agents are used in an amount of 0.1 to 100 parts by weight, preferably 1 to 30 parts by weight, based on the dry weight of the rubber latex. If the amount of foaming material is less than 0.1 parts by weight, the mixing and dissolving effect will be small and the rubber will form aggregates in the asphalt. Furthermore, if the amount of the blowing agent exceeds 100 parts by weight, the foaming of the blowing agent will continue for a long time in the asphalt, and the mixing and dissolving operation will take a long time. The anionic water-soluble polymer used in the present invention and the substance that causes coacervation under acidic conditions include acidic polymers such as polyvinylpyridine, polybenzylaminoethylcellulose, polydiethylaminoethylstyrene, polyvinylbenzylamine, and dodecyl Higher amines such as trimethylamine, coconut alkyldimethylamine, hardened beef tallow alkyldimethylamine, polyoxyethylene tallow alkylpropylene diamine, dodecyltriethanolamine, coconut alkylamine, dodecylamine, tallow alkylamine, cetylamine, stearylamine, hardened beef tallow alkylamine, etc. Examples of the acetate include cationic surfactants such as hydrochloride, sulfate, dimethyl sulfate, nitrate, and quaternary ammonium salt. These substances are added in an amount of 0.1 to 10 parts by weight, preferably 1 part by weight, based on the dry weight of the rubber latex.
It is used in a water-soluble form in a range of 5 parts by weight. In the present invention, first, a mixture of the rubber latex, a foaming agent, and an anionic water-soluble polymer is mixed with a cationic water-soluble polymer or a cationic surfactant that causes coacervation with the anionic water-soluble polymer under acidic conditions. Rubber can be separated into powder by mixing it in an aqueous solution. 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 selected through appropriate experiments. It is something. 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, and the pH at the end of powder separation is
as long as it 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 appropriate experiments. The synthetic resin emulsion is then added to the powdered rubber. The synthetic resin emulsion used here 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. As such a synthetic resin emulsion,
Polystyrene, polymethyl methacrylate, methyl methacrylate/methyl acrylate copolymer, polyvinyl chloride, vinyl chloride-vinylidene chloride copolymer, polyvinyl acetate, styrene-acrylonitrile copolymer, styrene-itaconic acid copolymer, styrene - There are emulsions such as vinyl chloride copolymers, styrene-methyl methacrylate copolymers, polyvinyl fluorides, and fluororesins such as polychlorotrifluoroethylene. 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 parts by weight, preferably 2 to 15 parts by weight. When the amount of synthetic resin is less than 1 part by weight, it is difficult to obtain sufficient effects and there is a tendency for blocks to form. Moreover, if it is used in an amount exceeding 30 parts by weight, the properties as a rubber will be impaired, which is not preferable. Through the above operations, the isolated powdered rubber containing a blowing agent dispersed inside the powdered rubber can be easily dehydrated using, for example, a centrifuge, and has fluidity or can be easily pulverized by a light pulverization operation. can. The material is then 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. In order to obtain a dry powdered rubber having a uniform particle size, it is preferable to use a fluidized drying method or a flash drying method that allows drying in a state of motion. [Effects of the Invention] The powdered rubber obtained by the method of the present invention has good dispersibility in asphalt, prevents agglomeration during storage, and has good fluidity, and is expected to expand the field of application and become industrially and economically viable. The effect is great. [Example] Examples will be described below, but the present invention is not limited thereto. In the examples, unless otherwise specified, parts represent weight. The cohesiveness of powdered rubber under load in the present invention 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 packed with 8 bags. Force equivalent to 48g/cm ²
The rubber powder was stored at 35°C for 24 hours under a load of 100 mL, and then removed from the box and evaluated based on the force required to break it and the particle size of the powdered rubber before and after storage. Production example of rubber latex and synthetic resin emulsion used in Examples (A) Polychloroprene rubber latex (hereinafter referred to as
(abbreviated as RCR) 4.0 parts of rosin potassium soap, 0.4 parts of caustic soda, and 0.4 parts of a formaldehyde-sodium naphthalene sulfonate condensate are dissolved in water in a nitrogen stream.
Next, 0.2 parts of n-dodecyl mercaptan, 2,
A chloroprene monomer in which 0.1 part of 6-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. Polymerization was stopped at 70% addition rate, and unreacted chloroprene monomer was distilled off to obtain PCR with a dry weight of 35%. (B) Acrylonitrile-butadiene rubber latex (hereinafter abbreviated as NBR) High NBR (trade name "Nipol 1571" manufactured by Nippon Zeon Co., Ltd.) was adjusted to have a dry weight of 35%. (C) Polybutadiene rubber latex (hereinafter abbreviated as BR) BR (product name "JSR0700" manufactured by Japan Synthetic Rubber Co., Ltd.)
was adjusted so that the dry weight was 35%. (D) Styrene-butadiene rubber latex (hereinafter
SBR (abbreviated as SBR) (product name "JSR0561" manufactured by Japan Synthetic Rubber Co., Ltd.) was adjusted to have a dry weight of 35%. (E) Polymethyl methacrylate emulsion (hereinafter abbreviated as PMMA) In a nitrogen stream, 7.5 parts of sodium alkylarylpolyoxyethylene sulfonate and 0.75 parts of sodium dodecylbenzenesulfonate were dissolved in 200 parts of water, and then 150 parts of methyl methacrylate was dissolved. was added and polymerized at 75°C using potassium persulfate as an initiator. The dry weight of the obtained PMMA is 40%
It was hot. (F) Polyvinyl chloride emulsion (hereinafter abbreviated as PVC)
15'') was used. The dry weight was 40%. (G) Polystyrene emulsion (hereinafter abbreviated as PSt) Dissolve 7.5 parts of sodium alkylaryl polyoxyethylene sulfonate and 0.7 parts of sodium lauryl sulfate in 100 parts of water in a nitrogen stream, then add 65 parts of styrene and filtrate at 70°C. Polymerization was carried out using potassium sulfate as an initiator. The dry weight of the PSt obtained was 40
It was %. Examples Examples 1 to 6 Using the combinations of reagents shown in Table 1, powdered rubber containing a foaming agent dispersed inside the powdered rubber was produced. That is, 3000 g of rubber latex, 1050 g of a 1% aqueous solution of anionic water-soluble polymer, and 105 g of a blowing agent.
g was added as a 20% aqueous slurry, mixed until a homogeneous solution was obtained, and the pH was adjusted to 6.3 by slowly adding a 10% acetic acid aqueous solution. Next, this mixed solution was poured into 4200 g of a 0.5% aqueous solution containing 2 parts by weight of higher amine acetate at room temperature with stirring, and the rubber was immediately separated into powder. PH after powder separation
was 4.9. Next, a synthetic resin emulsion was added in an amount of 5 parts by weight based on the dry weight of the rubber latex, and mixing was continued for about 10 minutes. After separating and washing with a cotton cloth, the mixture was dehydrated using a centrifuge to obtain a wet powder rubber that was 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. Comparative Examples 1-3 Using the combinations of reagents shown in Table 1, powdered rubber containing a blowing agent dispersed inside the powdered rubber was produced in the same manner as in Examples 1-6. As shown in Table 2, when synthetic resin emulsion is not added,
When the obtained powdered rubber is stored under load at 35°C for 24 hours, it aggregates like a sponge after storage and is impossible to break, and even if it can be broken, it remains in the powder state before storage. It can be seen that the properties of powdered rubber were lost.

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Claims (1)

[Claims] 1. A cationic water-soluble polymer that mixes a foaming agent and an anionic water-soluble polymer with an anionic or nonionic rubber latex, and coacervations with the anionic water-soluble polymer under acidic conditions. Alternatively, a method for producing powdered rubber, which comprises dropping and mixing a cationic surfactant in an aqueous solution under acidic conditions, then adding a synthetic resin emulsion, and dehydrating and drying.