JPH0225926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing thermoplastic resin. Generally, production techniques related to addition polymerization are classified into bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and the like. Among these, emulsion polymerization and suspension polymerization have been widely carried out industrially up to now, but the reason for this is that one of the biggest problems is to remove the heat generated by polymerization of vinyl compounds, and as a means to eliminate this, This is because a clever and economical method is to disperse the polymerization system in water as small particles. Suspension polymerization has been used for a long time for vinyl chloride, vinylidene chloride, styrene, methyl methacrylate, etc., and emulsion polymerization for vinyl acetate, SBR, butadiene, etc., and for this reason, most of the basic research on polymerization reaction engineering relies on these two methods. limited to. In the case of suspension polymerization, the polymerization reaction rate of the system is as fast as that of bulk polymerization, and since it is an aqueous medium system, it is easy to control the polymerization temperature, but when the polymerization conversion rate reaches about 20%, adhesion between suspended particles occurs. At the same time, the viscosity of the oil droplets increases, making it difficult for the oil droplets to be redispersed and eventually tending to form agglomerates. Optimal polymerization conditions (polymerization temperature, stirring, etc.) must be selected even for general-purpose monomers such as styrene, methyl methacrylate, vinyl chloride, and vinylidene chloride, but suspension polymerization stabilizers are particularly important factors. becomes. There are groups of monomers that are unsuitable or difficult to apply to such suspension polymerization methods. For example, ionic monomers, monomers with extremely slow polymerization reaction rates, monomers that involve reactions such as crosslinking, and monomers with a low Tg (glass transition point) of the resulting polymer are produced industrially. It cannot be said that it is suitable in terms of suspension polymerization stability or production stability on a large scale. However, the major advantages of the suspension polymerization method compared to other types of processes include ease of controlling the polymerization temperature, simplicity of the manufacturing process, and ease of recovery of the produced polymer. In the case of emulsion polymerization, since the emulsion latex particles are usually extremely small, the polymerization reaction rate is unusually fast when compared to other manufacturing methods. Another feature of this method is that it is a manufacturing method that can easily produce a polymer product with a high degree of polymerization. Furthermore, since emulsion polymerization is a stable reaction within micelles, unlike suspension polymerization, it is less limited by monomer species and the polymerization reaction temperature can be easily controlled. A feature not found in suspension polymerization is that it allows polymerization even when monomers are added in the presence of a polymer, making it possible to perform so-called multilayer polymerization, which allows the polymer composition in each layer to be changed freely. be changed.
However, a major problem in emulsion polymerization is the recovery of the produced polymer. Regarding the recovery of the produced polymer,
The most economical and industrially applied method is
In this method, the emulsifying ability of the emulsifier is reduced by adding an acid or an electrolyte to destroy and aggregate the micelles, thereby recovering the polymer from the aqueous medium. In this method, it is necessary to select the flocculant and the flocculation temperature in order to obtain the optimum shape of the polymer. However, in any case, the use of flocculants and emulsifiers has a large effect on the resulting polymer. Moreover, the coagulation method described above is accompanied by a number of problems depending on the type of polymer produced. For example, this coagulation method can be applied relatively easily to an internally plasticized resin polymer such as a rubber polymer or a graft polymer obtained by graft polymerizing a resin composition to a rubber polymer. This coagulation method is not suitable for a monomer group whose produced polymer has a relatively high Tg, or for a monomer group whose polymer is denatured by the addition of a flocculant and heat. Spray drying, freeze drying, and the like are methods for avoiding such problems, but these methods cannot be said to be advantageous from an economical or industrial point of view. In view of the current situation, the present inventors conducted intensive research to improve the method for producing non-rubber thermoplastic resins, and as a result, they arrived at the present invention. In the present invention, an aqueous dispersion of a non-rubber thermoplastic polymer containing an ethylenic monomer or a monomer mixture as a component is coagulated into a slurry form using a coagulant such as an acid or an electrolyte, and the slurry and A method for producing a thermoplastic resin, which comprises polymerizing an ethylenic monomer or a monomer mixture in the presence of a stabilizer. Conventionally, the above method has been applied in most cases to rubbery polymer latexes or graft polymer latexes obtained by emulsion polymerization of ethylenic monomers to rubbery polymers, that is, in the case of polymers with relatively low Tg. Although limited, the present invention has been found to be possible even when the Tg is in a relatively high range, that is, Tg 20°C or higher, preferably 60°C or higher. The method of the present invention solves all the above-mentioned problems of the conventional suspension polymerization method or emulsion polymerization method. In other words, for monomer groups with slow polymerization rates and monomer groups whose polymerization conversion rate cannot be improved due to gel effect,
Although the suspension polymerization method was considered to be unsuitable, according to the present invention, even when using such a monomer group, an emulsion is first produced by an emulsion polymerization method, and then the emulsion is treated with an acid or Adding an electrolyte, coagulating it to form a slurry, suspending the ethylenic monomer or monomer mixture in the presence of the slurry and a suspension polymerization stabilizer, and recovering the polymer in the form of beads. becomes possible. Next, although it is possible to polymerize monomers with a high Tg (over 100℃) in the emulsion polymerization method, in the coagulation process for extracting the polymer, coagulation is not very successful due to the high Tg. The resulting polymer becomes finely powdered, making it difficult to handle. In contrast, according to the method of the present invention, a flocculant is added to the obtained emulsion to form a slurry, and the ethylenic monomer or monomer mixture is immediately added to the emulsion in the presence of the slurry and a suspension polymerization stabilizer. By carrying out suspension polymerization, the polymer can be recovered in the form of beads. In addition, in the case of monomer groups whose polymers are denatured when a coagulant and heat are applied, a coagulant is added to the obtained polymer latex to form a slurry, and the ethylenic monomer or monomer mixture is The polymer can be recovered in the form of beads by rapidly carrying out suspension polymerization in the presence of the slurry and a suspension polymerization stabilizer. The aqueous dispersion used in the present invention can be obtained by many common emulsion polymerization methods, for example, by polymerizing an ethylenic monomer or monomer mixture in the presence of a common emulsifier using a common polymerization initiator as a catalyst. . In addition, there are also those obtained by dispersing a non-rubber thermoplastic polymer obtained by solution polymerization in an aqueous medium using a conventional dispersant, and those obtained by pulverizing the polymer using a pulverizer. It can also be used which is then dispersed in water using a conventional dispersant. Examples of the flocculant used in the present invention include acids or water-soluble inorganic salts. Acids include mineral acids such as sulfuric acid and hydrochloric acids, and organic ^acids (benzoic acid, salicylic acid, salts include, but are not limited to, sulfates such as magnesium sulfate, sodium sulfate, chlorides, and acetates. As the suspension polymerization stabilizer, ordinary inorganic dispersants and organic dispersants can be used. Examples of inorganic dispersants include magnesium carbonate and tricalcium phosphate, and examples of organic dispersants include polymer dispersants such as starch, gelatin, acrylamide, partially saponified polyvinyl alcohol, polyacrylic acid and its salts, and cellulose. , methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyalkylene oxide, polyvinylpyrrolidone, polyvinylimidazole,
Examples include sulfonated polystyrene, and examples of low-molecular dispersants include common emulsifiers such as alkylbenzene sulfonates and fatty acid salts. Ethylene monomers used in the present invention include aromatic monomers such as styrene, α-methylstyrene, and p-substituted styrene, acrylic esters, methacrylic esters, acrylonitrile,
Examples include methacrylonitrile, lower alkoxy acrylate, cyanoethyl acrylate, acrylamide, acrylic acid, methacrylic acid, etc.
Lower alkyl acrylates are also used as comonomers. It is also possible to use a crosslinking agent such as a crosslinking monomer as a comonomer for these ethylenic monomers. The emulsifier used to obtain the aqueous dispersion used in the present invention is a known emulsifier such as sodium alkylbenzenesulfonate, and the polymerization initiator is a peroxide such as kyumene hydroperoxide and a persulfate such as ammonium persulfate. Examples include redox systems consisting of salts, peroxides (kyumene hydroperoxide, t-butyl peroxide, etc.)-reducing agent systems. When a chain transfer agent is used in emulsion polymerization, in addition to alkyl mercaptans, halogenated alkyl sulfides, alkyl disulfides, thioglycolic acid esters, and α-methylstyrene dimers are also used. Mercaptans are preferred. Peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile are used as initiators in suspension polymerization. When a chain transfer agent is used in suspension polymerization, the same chain transfer agent as used in emulsion polymerization is used. During suspension polymerization, it is also possible to add plasticizers, lubricants, stabilizers, ultraviolet absorbers, etc. that are soluble in the monomers and do not hinder the progress of polymerization. It is also possible to blend the resin obtained by the above method with other thermoplastic resins, such as ABS resin, polystyrene resin, polymethacrylic resin, AS resin, polyester resin, polyolefin resin, polyester resin, etc. Examples include phenylene oxide resins and vinyl chloride resins. Parts and % in the following Examples and Comparative Examples represent parts by weight and % by weight. Example 1 Methyl methacrylate 70 parts Kyumene hydroperoxide 1.0 part t-dodecyl mercaptan 0.5 part Nonsal TK-1 (manufactured by NOF Corporation) 2 parts Sodium formaldehyde sulfoxylate
0.1 part Ferrous sulfate 0.01 part Ethylenediaminetetraacetic acid disodium salt 0.04 part Deionized water 140 parts The mixture of the above composition was charged into a reaction vessel, and after replacing the inside of the reactor with nitrogen, the mixture was stirred at a stirring speed of 200 rpm for 70 minutes.
The reaction was completed by polymerizing at ℃ for 3 hours to obtain an acrylic resin latex. The polymerization conversion rate was 93%.
The temperature of the obtained acrylic resin latex (PH10.0) was returned to room temperature, and stirred at 350 rpm for 10 minutes.
% sulfuric acid aqueous solution to form a highly viscous partial aggregate (PH3.0), and then a suspension polymerization stabilizer polymethyl methacrylate partially saponified product (number average molecular weight
After adding 10 parts of 0.3% aqueous solution of 30000), 30 parts of methyl methacrylate, benzoyl peroxide
A mixture of 0.2 parts of t-dodecyl mercaptan and 2 parts of t-dodecyl mercaptan was added dropwise over 30 minutes. The dispersion went from a high viscosity state to a low viscosity state (10 centipoise). This dispersion was polymerized by heating at 85° C. for 5 hours. After the polymer was separated, it was washed, dehydrated, and dried using a basket-type centrifugal dehydrator. The polymerization conversion rate was 98%, and the obtained polymer was a beautiful spherical bead body having a particle size distribution as shown below. The dried particles were directly pelletized and molded into test pieces using an injection molding machine. The molded product had no tropical color and had extremely excellent surface gloss.

[Table] Comparative Example 1 Using the acrylic resin latex obtained in Example 1, after replacing the inside of the reactor with nitrogen, the
The temperature was raised to 70°C while stirring at a stirring speed of . Then 30 parts of methyl methallylate, 0.5 part of kyumene hydroperoxide, 2 parts of t-dodecyl mercaptan.
A mixed solution of 1 part was added dropwise over a period of 30 minutes, and the mixture was kept as it was for 60 minutes to complete the polymerization. The polymerization rate was 98%. This latex was salted out and coagulated to obtain acrylic resin powder. The obtained powder was in the form of a fine powder with extremely fine particles. The powder was washed, dehydrated and dried using a basket-type centrifugal dehydrator, and the dried powder was directly pelletized and molded into a test piece using an injection molding machine. Comparative Example 2 Methyl methacrylate 100 parts Benzoyl peroxide 0.5 parts t-dodecyl mercaptan 1.0 parts Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts Sodium sulfate 1.0 parts Deionized water 150 parts The mixture of the above composition was charged into a reaction vessel, and after the inside of the reactor was replaced with nitrogen, 85
The reaction was completed by suspension polymerization at ℃ for 5 hours to obtain acrylic resin pearl particles. The polymerization conversion rate was 90%. After the polymer was separated, it was washed, dehydrated, and dried using a basket-type centrifugal dehydrator. The dried particles were directly pelletized and molded into test pieces using an injection molding machine. The results are summarized in Table 1.

[Table] Example 2 Styrene 16.8 parts Acrylonitrile 18.2 parts α-methylstyrene 35 parts Kyumene hydroperoxide 1.0 part t-dodecyl mercaptan 0.5 part Nonsal TK-1 (manufactured by NOF Corporation) 2 parts Sodium formaldehyde sulfoxylate
0.1 part ferrous sulfate 0.001 part ethylenediaminetetraacetic acid disodium salt
0.004 parts deionized water 140 parts The mixture with the above composition was charged into a reaction vessel, and after replacing the inside of the reactor with nitrogen, the mixture was stirred at a stirring speed of 200 rpm to
C. for 3 hours to complete the reaction, and a styrene-acrylonitrile-.alpha.-methylstyrene copolymer latex was obtained. The polymerization conversion rate was 87%. The temperature of the obtained acrylic resin latex (PH10.0) was returned to room temperature, and 10%
After adding 8 parts of a sulfuric acid aqueous solution to produce a highly viscous partial aggregate (PH3.0), and then adding 5 parts of a 0.3% aqueous solution of sulfonated polystyrene sodium salt (number average molecular weight 20,000) as a suspension polymerization stabilizer. , 7.2 parts of styrene, 7.8 parts of acrylonitrile, 15 parts of α-methylstyrene, 0.2 parts of benzoyl peroxide, t
- A mixture of 2 parts of dodecyl mercaptan was added dropwise over 30 minutes. Thereafter, 5 parts of the above 0.3% aqueous solution of sulfonated polystyrene sodium salt was further added. The dispersion went from a high viscosity state to a low viscosity state (10 centipoise). This dispersion was polymerized by heating at 80°C for 5 hours. After the polymer was separated, it was washed, dehydrated, and dried using a basket-type centrifugal dehydrator. The polymerization conversion rate was 93%, and the obtained polymer was in the form of beautiful spherical beads. The dried particles were directly pelletized and molded into test pieces using an injection molding machine. The molded product had excellent surface gloss. Example 3 Acrylonitrile 24 parts α-methylstyrene 50 parts Kyumene hydroperoxide 1.0 parts t-dodecyl mercaptan 0.5 parts Nonsal TK-1 (manufactured by NOF Corporation) 2.0 parts Sodium formaldehyde sulfoxylate
0.1 part ferrous sulfate 0.001 part ethylenediaminetetraacetic acid disodium salt
0.004 parts deionized water 140 parts The mixture with the above composition was charged into a reaction vessel, and after replacing the inside of the reaction vessel with nitrogen, the mixture was stirred at a stirring speed of 200 rpm.
Polymerization was carried out at 70°C for 3 hours to complete the reaction and obtain a latex. The polymerization conversion rate was 70%. The temperature of the obtained latex (PH10.0) was returned to room temperature, and the temperature was heated at 350 rpm.
Under stirring, 8 parts of a 10% sulfuric acid aqueous solution was added to form a highly viscous partial aggregate (PH3.0), and then 0.3% of the suspension polymerization stabilizer sulfonated polystyrene sodium salt (number average molecular weight 20,000) was added. 10 parts of aqueous solution, 26 parts of styrene, 0.2 parts of benzoyl peroxide, t-
A mixture of 2 parts of dodecyl mercaptan was simultaneously added dropwise over 30 minutes. The dispersion went from a high viscosity state to a low viscosity state (10 centipoise). This dispersion was polymerized by heating at 80°C for 5 hours. After the polymer was separated, it was washed, dehydrated, and dried using a basket-type centrifugal dehydrator. The polymerization conversion rate was 94%, and the obtained polymer was in the form of beautiful spherical beads. The dried particles were directly pelletized and molded into test pieces using an injection molding machine. The molded product had excellent surface gloss. Comparative Example 3 After purging the inside of the reactor with nitrogen using the styrene-acrylonitrile-α-methylstyrene latex obtained in Example 2, the temperature was raised to 70° C. while stirring at a stirring speed of 200 rpm. Then styrene
7.2 parts, acrylonitrile 7.8 parts, α-methylstyrene 15 parts, kyumene hydroperoxide 0.5 parts,
A mixed solution of 2 parts of t-dodecyl mercaptan was added dropwise over 30 minutes, and the mixture was kept for 60 minutes to complete polymerization. The polymerization rate was 93%. This latex was salted out and coagulated to produce styrene-acrylonitrile-α-
A methylstyrene copolymer was obtained. However, salting out coagulation was not sufficient, a considerable amount of polymer was lost as latex, and the polymerization conversion rate was 89%. The obtained powder was in the form of a fine powder with extremely fine particles. It was washed, dehydrated and dried using a basket type centrifugal dehydrator. The dried powder was pelletized as it was, and a test piece was molded using an injection molding machine. Comparative Example 4 Styrene 24 parts Acrylonitrile 26 parts α-methylstyrene 50 parts Calcium phosphate paste (solid content 10%) 3 parts Deionized water 150 parts A mixture of the above composition was charged into a reaction vessel, and after purging the inside of the reaction vessel with nitrogen, With stirring speed of 350rpm
Polymerization was carried out at 80°C for 5 hours to complete the reaction and obtain pearl-like particles. The polymerization conversion rate was 65%. After the polymer was separated, it was washed, dehydrated, and dried using a basket-type centrifugal dehydrator. The dried particles were directly pelletized and molded into test pieces using an injection molding machine.

[Table] Example 4 Acrylic resin latex was produced in the same manner as in Example 1 using the following formulation. Methyl acrylate 51.8 parts Methyl methacrylate 16.8 parts Kyumene hydroperoxide 1.0 parts t-dodecyl mercaptan 0.5 parts Nonsal TK-1 (manufactured by NOF Corporation) 2.0 parts Sodium formaldehyde sulfoxylate
0.1 part ferrous sulfate 0.001 part ethylenediaminetetraacetic acid disodium salt
0.004 parts Deionized water 140 parts The latex obtained under the above conditions was subjected to suspension polymerization in the same manner as in Example 1 under the following conditions to obtain spherical beads. Methyl acrylate 22.2 parts Methyl methacrylate 7.2 parts Benzoyl peroxide 0.2 parts t-Dodecyl mercaptan 2.0 parts Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts After drying the obtained spherical beads with hot air, the particle distribution was measured.

【table】

[Table] Example 5 An acrylic resin latex was produced in the same manner as in Example 1 using the following formulation. Methyl methacrylate 35 parts 2-hydroxyethyl methacrylate 35 parts t-dodecyl mercaptan 0.5 parts Kyumene hydroperoxide 1.0 parts Nonsal TK-1 2.0 parts Sodium formaldehyde sulfoxylate
0.1 part ferrous sulfate 0.001 part ethylenediaminetetraacetic acid disodium salt
0.004 parts Deionized water 140 parts The latex obtained under the above conditions was subjected to the same operation as in Example 1 and suspension polymerized under the following conditions.
Spherical beads were obtained. Methyl methacrylate 30 parts Benzoyl peroxide 0.2 parts t-dodecyl mercaptan 2.0 parts Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts The polymerization conversion rate was 95%, and the particle size distribution was beautiful beads as shown below.

[Table] Comparative Example 5 Using the acrylic resin latex obtained in Example 5, the same procedure as in Comparative Example 1 was carried out to add 30 parts of methyl methacrylate and kyumene hydroperoxide.
A mixed solution of 0.5 part of t-dodecyl mercaptan and 2 parts of t-dodecyl mercaptan was added dropwise over a period of 30 minutes, and the mixture was maintained for 60 minutes to complete polymerization. After the polymerization was completed, the mixture was cooled, 5 parts of concentrated sulfuric acid was added thereto, and the mixture was coagulated by heating to extract the polymer, which was then dried. The polymerization rate was 95%. Comparative Example 6 Methyl methacrylate 65 parts 2-hydroxyethyl methacrylate 35 parts Benzoyl peroxide 0.5 part t-dodecyl mercaptan 1.0 part Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts Sodium sulfate 1.0 parts Deionized water 150 parts A mixture having the above composition was charged into a reaction vessel, and after purging with nitrogen, suspension polymerization was carried out, but the mixture immediately formed into lumps after the temperature was raised to 85°C. Example 6 Methyl methacrylate 35 parts Methacrylic acid 35 parts t-dodecyl mercaptan 0.5 parts Kyumene hydroperoxide 1.0 parts Nonsal TK-1 (manufactured by NOF Corporation) 2.0 parts Sodium formaldehyde sulfoxylate
0.1 part ferrous sulfate 0.001 part ethylenediaminetetraacetic acid disodium salt
0.004 parts Deionized water 140 parts The latex obtained under the above conditions was subjected to exactly the same operation as in Example 1, and as a result of suspension polymerization under the following conditions, spherical beads were obtained. Methyl methacrylate 30 parts Benzoyl peroxide 0.2 parts t-dodecyl mercaptan 2.0 parts Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts The polymerization rate was 96%, and the particle size distribution was beautiful beads as shown below.

[Table] Comparative Example 7 Using the acrylic resin latex obtained in Example 6, after purging the reaction vessel with nitrogen,
The temperature was raised to 70°C while stirring at a stirring speed of . Then 30 parts of methyl methacrylate, 0.5 parts of kyumene hydroperoxide, 2.0 parts of t-dodecyl mercaptan.
A mixed solution of 1 part was added dropwise over a period of 30 minutes, and the mixture was kept as it was for 60 minutes to complete the polymerization. The polymerization rate was 95%. Thereafter, the polymer was extracted by the same treatment as in Comparative Example 6. Comparative Example 8 Methyl methacrylate 65 parts Methacrylic acid 35 parts Benzoyl peroxide 0.5 parts t-dodecyl mercaptan 1.0 parts Partially saponified polymethyl methacrylate 0.3%
Aqueous solution 10 parts Sodium sulfate 1.0 parts Deionized water 150 parts After charging the mixture with the above composition into a reaction vessel and purging it with nitrogen, suspension polymerization was attempted at 85°C with a stirring speed of 350 rpm, but the temperature did not rise to 85°C. It formed into a lump.

【table】

[Table] Example 7 Polybutadiene latex (solid content) ^*
60 parts (30 parts) Styrene 51.8 parts Acrylonitrile 18.2 parts Ferrous sulfate 0.003 parts Dextrose 0.5 parts Kyumene hydroperoxide 0.33 parts t-Dodecylmercaptan 0.3 parts Sodium pyrophosphate 0.2 parts Disproportionated rosin acid soap 0.5 parts Caustic soda 0.1 parts Sodium methylene bisnaphthalene sulfonate
0.2 parts Deionized water 150 parts (*Sumitomo Nogatatsuku SN-800B solid content 50
%) The mixture with the above composition was charged into a reaction vessel, and after purging the inside of the reaction vessel with nitrogen, the mixture was stirred at a stirring speed of 200 rpm.
C. for 3 hours to complete the reaction and obtain a graft polymer latex. The polymerization conversion rate was 97%. Calcium chloride 5
ABS powder was obtained by salting out and coagulating using 50% of the powder and drying with hot air at 70°C overnight. Obtained ABS powder and Example 3
were mixed with the styrene-acrylonitrile-α-methylstyrene copolymer beads obtained in Table 5, and then added with calcium stearate.
0.4 parts were mixed using a 10 volume Henschel mixer at 3000 rpm, pelletized and molded into test pieces using an injection molding machine. The molded product had no tropical color and had extremely excellent surface gloss. Comparative Example 9 50 parts of ABS powder obtained in Example 7, Comparative Example 3
50 parts of the obtained styrene-acrylonitrile-α-methylstyrene copolymer powder and 0.4 parts of calcium stearate were mixed using a 10 volume Henschel mixer at 3000 rpm, pelletized, and a test piece was molded using an injection molding machine. A molded product with a strong yellow tinge was obtained.

【table】

Claims (1)

[Claims] 1 An aqueous dispersion of a non-rubber thermoplastic polymer containing an ethylenic monomer or a monomer mixture as a component is coagulated using a coagulant to form a slurry, and the slurry is mixed with a suspension polymerization stabilizer in the presence of a suspension polymerization stabilizer. A method for producing a thermoplastic resin, comprising polymerizing an ethylenic monomer or a monomer mixture.