JPH0582401B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a method for producing a water-soluble polystyrene sulfonate in high yield. Prior Art A method of sulfonating polystyrene to obtain a water-soluble sulfonated product is to use chlorosulfonic acid as a sulfonating agent and add water as a crosslinking inhibitor to prevent the product from becoming insolubilized due to crosslinking. It has been known. Furthermore, when halogenated hydrocarbons are used as solvents, anionic or nonionic surfactants, polyvinyl alcohol, etc., act as dispersants, since halogenated hydrocarbons do not dissolve in water. Alternatively, it is known to efficiently disperse water in the reaction system using an aqueous solution of a nonionic compound (Japanese Patent Publication No. 37226/1983). However, since water essentially does not dissolve in the solvent and becomes a heterogeneous system, a large amount is required to be added and the yield also decreases. Also,
Since water reacts with the sulfonating agent, a large amount of the sulfonating agent is required, and the generation of inorganic salts such as Na ₂ SO ₄ and NaCl is unavoidable. Furthermore, strong stirring is required to create a uniformly dispersed system, which is disadvantageous from an industrial standpoint. On the other hand, it is known to use an SO ₃ complex as a sulfonating agent when sulfonating polystyrene; for example, US Pat. No. 2,533,210,
Specification No. 2604456, Specification No. 2725368, Specification No. 2725368,
It is described in the specification of No. 2764576, the specification of No. 2945842, or the magazine "Petroleum and Petrochemicals" 10(5), 26 (1960). However, such sulfonating agents cannot sufficiently control the selective reactivity toward polystyrene, and their compatibility with solvents and additives is insufficient. It was not possible to achieve a high yield and efficiently obtain a water-soluble sulfonated product. OBJECT OF THE INVENTION The object of the present invention is to produce a highly pure water-soluble polystyrene sulfonated product in high yield. Structure of the Invention The method for producing a polystyrene sulfonate of the present invention uses a _C1-2 aliphatic halogenated hydrocarbon as a solvent when polystyrene having an average molecular weight of 200 to 5,000 is sulfonated, and a C1-2 aliphatic halogenated hydrocarbon is used as a solvent to produce a polystyrene sulfonate of 0.5 to 100 parts by weight per 100 parts by weight of polystyrene. Part by weight of benzenesulfonic acid and/or alkylbenzenesulfonic acid having a C _1-20 alkyl group is added, and SO ₃ or a complex of SO ₃ with a substance with a dielectric constant of 11.5 or less at 25 ° C is used as a sulfonating agent. It is characterized by using sulfonation. The present invention will be explained in more detail below. The polystyrene used as a raw material in the present invention is
It has an average molecular weight of 200-50000. The average molecular weight
When it exceeds 50,000, the viscosity of the reaction system becomes high, which not only reduces the sulfonation reaction rate but also makes handling difficult. On the other hand, if it is less than 200,
Since styrene monomer is included, polymerization reactions occur in parallel, reducing the yield of water-soluble sulfonated products. As the solvent, an aliphatic halogenated hydrocarbon having 1 to 2 carbon atoms is used. Specific examples of such halogenated hydrocarbons include methylene dichloride, 1,2-dichloroethane, ethyl chloride, carbon tetrachloride, 1,1-dichloroethane, 1,1,2,
Inactive sulfonating agents include 2-tetrachloroethane, chloroform, and ethylene dibromide. The number of carbon atoms in the halogenated hydrocarbon is 3
If it exceeds the above, by-products will be produced by reaction with the sulfonating agent, and the solubility of the sulfonating agent and additives such as alkylbenzene sulfonic acid will deteriorate, which is undesirable. The appropriate amount of the solvent to be used is about 1 to 30 parts by weight based on the raw material polystyrene. In the present invention, first, the raw material polystyrene is dissolved in a halogenated hydrocarbon solvent, and as an additive, benzenesulfonic acid and/or an alkylbenzenesulfonic acid whose alkyl group has 1 to 20 carbon atoms are added in an amount of 0.5 to 100 parts by weight per 100 parts by weight of polystyrene. It is added in an amount of 100 parts by weight, preferably 5 to 50 parts by weight. Since this additive completely mixes with the sulfonating agent and the solvent to form a homogeneous system, even a small amount added can exhibit sufficient effects. If the amount added is less than 0.5 part by weight, intramolecular or intermolecular crosslinking tends to occur, resulting in the formation of a large amount of water-insoluble components, which is not preferable. On the other hand, if the amount exceeds 100 parts by weight, the compatibility with the sulfonating agent and the reaction product will be poor, resulting in non-uniformity, which is not preferable. Furthermore, if the number of carbon atoms in the alkyl group of the alkylbenzene exceeds 20, it is not preferable because the compatibility with the solvent and the sulfonating agent decreases.
As alkylbenzene sulfonic acid, linear type,
Either branch type can be used. As the sulfonic agent, SO ₃ or a complex of SO ₃ and a substance having a dielectric constant of 11.5 or less at 25° C. is used. Examples of SO ₃ include liquid SO ₃ , gaseous SO ₃ , oleum, and SO ₃ diluted with an inert gas such as nitrogen, dry air, and argon. Dilution with an inert gas is suitably carried out so that the SO ₃ concentration is 1 to 12 vol%, preferably 3 to 4 vol%. As the substance that forms a complex with SO ₃ , a gaseous or liquid inorganic or organic compound having a dielectric constant (at 25° C.) of 11.5 or less, preferably 9 or less is used. If the dielectric constant (ε) exceeds 11.5, the solubility of the sulfonating agent will be poor due to the fact that it is used in combination with benzenesulfonic acid and/or alkylbenzenesulfonic acid as an additive, and the reaction will not proceed uniformly. The reactivity of the curing agent itself also decreases. Lewis bases with ε=11.5 or less include dioxane (ε=2.2) and thioxane (ε=
3.7), dimethylaniline (ε = 4.8), triethylamine (ε = 2.4), hydrogen chloride (ε = 4.6) (equivalent to chlorosulfonic acid), benzoic acid (ε = 5.8), triethyl phosphate (ε = 6.0) , ethyl acetate (ε=6.0), ethyl palmitate (ε=2.3), diethyl ether (ε=4.2), chlorobenzene (ε
=5.6), morpholine (ε=7.4), and isoquinoline (ε=10.7). The sulfonation is suitably carried out using a sulfonating agent in an amount of 0.5 to 2.0 molar moles per styrene monomer in the starting polystyrene, preferably in the range of 0.7 to 1.5. If the molar ratio is too small, the degree of sulfonation is insufficient and the water-insoluble content increases, while if the molar ratio is too large, intra- or intermolecular cross-linking tends to occur, resulting in an increase in by-products and water-insoluble content. . The appropriate temperature for the sulfonation reaction is 10 to 80°C.
Preferably it is 30-40°C. If the temperature is too low, the reaction will be difficult to proceed, and if the temperature is too high, not only will scattering of the solvent become a problem, but also intramolecular or intermolecular crosslinking of polystyrene will easily occur, which is undesirable. The sulfonation reaction produces polystyrene sulfonic acid dispersed in a halogenated hydrocarbon solvent. By neutralizing this and separating the solvent, a highly pure water-soluble polystyrene sulfonate can be obtained. Benzenesulfonic acid or alkylbenzenesulfonic acid used as an additive is also simultaneously neutralized and turned into a salt. Since these have the same charge as polystyrene sulfonate, they have no effect on the dissociation effect. Benzene sulfonates and lower alkylbenzene sulfonates act as hydrotropes, and higher alkylbenzene sulfonic acids act as anionic surfactants, so they can be used effectively, for example,
It can also be used in a wide range of applications, such as as a slurrying agent for highly concentrated water slurries, without being separated and removed. Effects of the Invention According to the present invention, by combining specific raw material polystyrene, a solvent, an additive, and a sulfonating agent, a highly purified polystyrene sulfonate with less water-insoluble matter can be obtained in high yield. This is because by adopting the above specific combination, the uniform solubility and reactivity of the sulfonating agent can be controlled, which improves the selective reaction of the sulfonating agent to the aromatic nucleus of polystyrene, and as a result, the formation of the crosslinked structure. This is thought to be because the yield of less water-soluble polystyrene sulfonate is improved. Additionally, the additives work effectively in small amounts, and the sulfonating agent may also be used in low molar amounts. Furthermore, the production of by-products such as inorganic salts is small, and separation and purification operations for by-products are eliminated, so the process is simplified and industrially advantageous. Example As shown in Table 1, 50 g of polystyrene was dissolved in a predetermined amount of solvent, and then, after dissolving the additives, sulfonation was carried out using a sulfonating agent while maintaining the reaction temperature at 30°C. After sulfonation, add sodium hydroxide,
The resulting polystyrene sulfonic acid was neutralized to obtain sodium polystyrene sulfonate. The introduction rate of sulfone groups was determined by sulfur analysis, and the results are shown in Table 1. The abbreviations in Table 1 indicate the following.

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Claims (1)

[Claims] 1. When polystyrene with an average molecular weight of 200 to 50,000 is sulfonated, a C _{1 to 2} aliphatic halogenated hydrocarbon is used as a solvent, and 0.5 to 100 parts by weight of benzenesulfonic acid and/or C _{1 to 20 are} added per 100 parts by weight of polystyrene. A sulfone of polystyrene _, characterized in that the sulfonation is carried out by adding an _{alkylbenzenesulfonic} acid having an alkyl group of method.