A method of producing a 2,4'-dihydroxydiphenylsulfone

Abstract: A method of producing a high purity 2,4'-dihydroxydiphenylsulfone comprises producing a crude 2,4'-dihydroxydiphenylsulfone by mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of catalyst selected from phosphonic acid, phosphinic acid and salts thereof in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C and purifying the crude 2,4'-dihydroxydiphenylsulfone thus produced using (1) a mixed solvent containing 5 to 20 weight % of at least one kind selected from lower aliphatic alcohols and 95 to 80 weight % of at least one kind selected from aromatic hydrocarbons not containing halogen, (2) a mixed solvent containing 10 to 40 weight % of at least one kind selected from ketones and 90 to 60 weight % of at least one kind selected from aromatic hydrocarbons not containing halogen or (3) a mixed solvent containing 10 to 40 weight % of at least one kind selected from esters of acetic acid and 90 to 60 weight % of at least one kind selected from aromatic hydrocarbons not containing halogen. According to the method, 2,4'-dihydroxydiphenylsulfone useful as developer for thermal recording paper can be produced efficiently with high selectivity and a high purity product can be obtained efficiently.

Description: 1. Field of the invention The present invention relates to a novel method of producing a 2,4'-dihydroxydiphenylsulfone. More particularly, it relates to a method of producing a 2,4'-dihydroxydiphenylsulfone useful as developer for thermal recording paper efficiently with high selectivity from phenols and sulfuric acid. The present invention also relates to a novel method of producing a high purity 2,4'-dihydroxydiphenylsulfone. More particularly, it relates to a method of producing a high purity 2,4'-dihydroxydiphenylsulfone useful as developer for thermal recording paper efficiently by purifying a crude 2,4'-dihydroxydiphenylsulfone produced from phenols and sulfuric acid. 2. Description of the prior art Various kinds of phenol compounds have heretofore been proposed as developer for thermal recording paper. Among the phenol compounds, 2,4'-dihydroxydiphenylsulfones have been expected to provide very useful developer for thermal recording paper. Method of producing 4,4'-dihydroxydiphenylsulfones has heretofore been studied extensively and much efforts have been made to obtain high purity 4,4'-dihydroxydiphenylsulfones by minimizing formation of 2,4'-dihydroxydiphenylsulfones which are isomers thereof. However, it is the real situation that no method of producing 2,4'-dihydroxydiphenylsulfone with increased yield have heretofore been reported. Furthermore, when 2,4'-dihydroxydiphenylsulfones are produced by the reaction of phenols with sulfuric acid, high purity products useful as developer for thermal recording paper have not been obtained. For example, when 2,4'-dihydroxydiphenylsulfone is produced by the reaction of phenol and sulfuric acid, a mixture of isomers containing 2,4'-dihydroxydiphenylsulfone and 4,4'-dihydroxydiphenylsulfone in a weight ratio of about 20 to 80 is obtained even under the optimum reaction condition. When 5-methyl-2,4'-dihydroxydiphenylsulfone is produced by using phenol and p-cresol as the material phenols, or when 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone is produced by using phenol and 2,4-xylenol as the material phenols, a product containing at most 10 to 20 weight % of the 2,4'-dihydroxy isomer is obtained in either case. Method of purifying 4,4'-dihydroxydiphenylsulfones has heretofore been studied extensively and much efforts have been made to obtain high purity 4,4'-dihydroxydiphenylsulfones by minimizing the content of 2,4'-dihydroxydiphenylsulfones which are isomers thereof. However, it is the real situation that no method of purifying 2,4'-dihydroxydiphenylsulfones with increased purity have heretofore been reported. FR-A-990161 discloses a method for the preparation of bis(oxyaryl)sulfones. DE-A-2708388 discloses a method for preparation of 4,4'-dihydroxydiphenylsulfone SUMMARY OF THE INVENTION The present invention accordingly has an object to provide a method of producing a 2,4'-dihydroxydiphenylsulfone useful as developer for thermal recording paper with high selectivity and industrially advantageously. The present invention also has an object to provide a method of producing a high purity 2,4'-dihydroxydiphenylsulfone useful as developer for thermal recording paper efficiently by purifying a crude 2,4'-dihydroxydiphenylsulfone produced from phenols and sulfuric acid. Extensive investigations were undertaken by the present inventors with the objects described above and it was discovered that 2,4'-dihydroxydiphenylsulfones are produced with high selectivity by heating phenols and sulfuric acid in the presence of a specific catalyst in the absence of a solvent or in the presence of a specific solvent and that high purity 2,4'-dihydroxydiphenylsulfones can be obtained by using a specific solvent for purification. The present invention has been completed on the basis of the discovery. Thus, the present invention provides a method of producing a 2,4'-dihydroxydiphenylsulfone which comprises mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C. The present invention also provides a method of producing a high purity 2,4'-dihydroxydiphenylsulfone which comprises producing a crude 2,4'-dihydroxydiphenylsulfone by mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C and purifying the crude 2,4'-dihydroxydiphenylsulfone thus produced using (1) a mixed solvent containing 5 to 20 weight % of at least one kind selected from the group consisting of lower aliphatic alcohols and 95 to 80 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen, (2) a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of ketones and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen or (3) a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of esters of acetic acid and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen. Other and further objects, features and advantages of the invention will appear more fully from the following description. DETAILED DESCRIPTION OF THE INVENTION The invention is described in more detail in the following. Examples of the phenol used as the raw material in the present invention are phenols of which at least one of the ortho-positions and the para-position are both unsubstituted, such as phenol, o-cresol, m-cresol, 2,3-xylenol, 2,5-xylenol, 3,5-xylenol and the like; mixtures of two kinds thereof; and mixtures of one kind selected from the aforesaid phenols and one kind selected from phenols of which the two ortho-positions or the para-position are substituted, such as p-cresol, 2,4-xylenol, 2,6-xylenol, 3,4-xylenol and the like. The phenols and sulfuric acid are used preferably in a mol ratio of the phenols to sulfuric acid in the range of 2:1 to 4:1. In the present invention, the reaction is conducted by heating in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C. It is necessary for conducting the reaction that at least one kind selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof is present in the reaction system as catalyst. Amount of the catalyst present in the reaction system is selected generally in the range of 2 weight % or more, preferably 5 to 10 weight %, based on the amount of the sulfuric acid. When the amount of the catalyst is less than 2 weight %, effect of enhancing the selectivity of a 2,4'-dihydroxydiphenylsulfone is not sufficiently exhibited. When the amount is more than 10 weight %, effect of enhancing the selectivity is not so much increased as expected from the increase in the amount. When the reaction is conducted in the absence of a solvent, it is preferable that the reaction is conducted by heating to a temperature in the range of 140 to 170°C under a reduced pressure, preferably under a pressure of 79980 to 6665 Pa (600 to 50 mmHg). When the reaction is conducted in the presence of a solvent, an aromatic hydrocarbon having a boiling point at atmospheric pressure in the range of 130 to 200°C is used as the solvent. Examples of the aromatic hydrocarbon solvent are xylene, ethylbenzene, butylbenzene, diethylbenzene, mesitylene, cymene, cumene, pseudocumene, Shellsol A (a product of Shell Chemical Co., a trade name), Shellsol AB (a product of Shell Chemical Co., a trade name) and the like. The solvent may be used singly or as a combination of two or more kinds. An aromatic petroleum solvent having a boiling at atmospheric pressure in the range of 130 to 200°C may be used as well. When the reaction is conducted in the presence of the solvent, the reaction is generally conducted while water formed by the reaction is removed from the reaction system by azeotropic distillation at atmospheric pressure or at a slightly reduced pressure. In the method of production in the presence of the aforesaid solvent, phenolsulfonic acids formed as by-products can be separated from dihydroxydiphenylsulfones easily by filtration. The phenolsulfonic acids and the solvent can be reused. In the conventional method of producing 4,4'-dihydroxydiphenylsulfone, content of a 2,4'-dihydroxydiphenylsulfone which is formed along with the 4,4'-dihydroxy isomer is kept at about 20 weight % or less when the reaction conditions are adjusted in such as manner that a mixture of dihydroxydiphenylsulfone isomers is obtained in a yield of 80 mol % or more. On the other hand, the reaction conditions have to be adjusted in such a manner that yield of a mixture of dihydroxydiphenylsulfone isomers is decreased to 80 mol % or less for increasing the content of a 2,4'-dihydroxydiphenylsulfone to 20 weight % or more. Thus, application of the conventional method to production of a 2,4'-dihydroxydiphenylsulfone causes economically unfavorable results. In contrast, according to the method of the present invention, ratio of a 2,4'-dihydroxydiphenylsulfone to a 4,4'-dihydroxydiphenylsulfone in the reaction product can be increased almost to a weight ratio of 50 : 50 and yield of a mixture of the dihydroxydiphenylsulfone isomers can also be increased to 80 mol % or more at the same time in the case where phenol is used as the material phenol, for example. As other examples, in the case where phenol and p-cresol are used as the material phenols for producing 5-methyl-2,4'-dihydroxydiphenylsulfone or in the case where phenol and 2,4-xylenol are used as the material phenols for producing 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone, content of the 2,4'-dihydroxy isomer can be increased to 80 weight % or more and yield of a mixture of the isomers of dihydroxydiphenylsulfone derivatives can be increased to 80 mol % or more at the same time. A mixture of isomers of a dihydroxydiphenylsulfone obtained by the method of the present invention can be purified to produce a high purity dihydroxydiphenylsulfone. A crude 2,4'-dihydroxydiphenylsulfone is treated with (1) a mixed solvent containing 5 to 20 weight % of at least one kind selected from the group consisting of lower aliphatic alcohols and 95 to 80 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen, (2) a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of ketones and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen or (3) a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of esters of acetic acid and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen. Examples of the lower aliphatic alcohol in the mixed solvent (1) are methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol and the like. The lower aliphatic alcohol may be used singly or as a combination of two or more kinds. Examples of the aromatic hydrocarbon not containing halogen are benzene, toluene, xylene, ethylbenzene, butylbenzene, diethylbenzene, mesitylene, cymene, cumene, pseudocumene and the like. The aromatic hydrocarbon not containing halogen may be used singly or as a combination of two or more kinds. When contents of the lower aliphatic alcohol and the aromatic hydrocarbon not containing halogen in the mixed solvent (1) are out of the specified ranges, the object of the invention cannot be achieved sufficiently. Examples of the ketone in the mixed solvent (2) are acetone, methyl ethyl ketone, methyl isobutyl ketone, 2-pentanone, 3-pentanone, 2-heptanone, 4-heptanone, diisobutyl ketone, cyclohexanone and the like. The ketone may be used singly or as a combination of two or more kinds. Examples of the aromatic hydrocarbon not containing halogen are the same as those described as examples of the aromatic hydrocarbon not containing halogen in the mixed solvent (1). The aromatic hydrocarbon not containing halogen may be used singly or as a combination of two or more kinds. When contents of the ketone and the aromatic hydrocarbon not containing halogen in the mixed solvent (2) are out of the specified ranges, the object of the invention cannot be achieved sufficiently. Examples of the ester of acetic acid in the mixed solvent (3) are methyl acetate, ethyl acetate, propyl acetate, butyl acetate and the like. The ester of acetic acid may be used singly or as a combination of two or more kinds. Examples of the aromatic hydrocarbon not containing halogen are the same as those described as examples of the aromatic hydrocarbon not containing halogen in the mixed solvent (1). The aromatic hydrocarbon not containing halogen may be used singly or as a combination of two or more kinds. When contents of the ester of acetic acid and the aromatic hydrocarbon not containing halogen in the mixed solvent (3) are out of the specified ranges, the object of the invention cannot be achieved sufficiently. In the method of the present invention, the crude 2,4'-dihydroxydiphenylsulfone obtained by the reaction of phenols and sulfuric acid is added to the mixed solvent described above and dissolved into the solvent by heating. The solution is then cooled and the undissolved part which contains other isomers etc. is removed by a conventional method, such as filtration and centrifugal separation. By removing the lower aliphatic alcohol, the ketone or the ester of acetic acid from the remaining solution by distillation, the desired high purity 2,4'-dihydroxydiphenylsulfone can be obtained. In this method, ratio of mixing the components of the mixed solvent and amount of the mixed solvent used in the purification can be suitably decided according to purity and amount of the crude 2,4'-dihydroxydiphenylsulfone for purification. Temperature of the heating and temperature of the cooling can be suitably selected according to the kind of solvent used for the purification. According to the method of the present invention, it is possible to produce a 2,4'-dihydroxydiphenylsulfone having purity of 95 weight % or more by suitably selecting the conditions of purification. Furthermore, the method of the present invention does not employ a halogenated hydrocarbon having adverse effects on the environment, such as dichloroethane, o-dichlorobenzene and the like, and can be very advantageously practiced with respect to the environmental health and from the industrial point of view. To summarize the advantages obtained by the invention: according to the method of the present invention, 2,4'-dihydroxydiphenylsulfones can be obtained efficiently with high selectivity from phenols and sulfuric acid. By purifying the product with a specific solvent, high purity 2,4'-dihydroxydiphenylsulfones useful as developer for thermal recording paper can be obtained efficiently. Said 2,4'-dihydroxydiphenylsulfones are useful as developer for thermal recording paper having good storage property and can replace diaryldihydroxydiphenylsulfones and 4-isopropoxy-4'-hydroxydiphenylsulfone. The invention will be understood more readily with reference to the following examples; however, these examples are intended to illustrate the invention and are not to be construed to limit the scope of the invention. Example 1 Into a reactor, 793 g of phenol, 334 g of sulfuric acid and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under a reduced pressure of 74648 to 34658 Pa (560 to 260 mmHg) at 150 to 165°C for 3 hours. When amount of the distillate reached 250 g, 165 g of phenol was added. Dehydration reaction was further continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for 2 hours and 180 g of the distillate was obtained. Then, additional 165 g of phenol was added and dehydration reaction was continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for additional 2 hours. The reaction was finished when amount of the distillate reached 140 g. The reaction mixture was washed with water to remove phenolsulfonic acid and then dried. A mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 85 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 49 weight % of 2,4'-dihydroxydiphenylsulfone, 50 weight % of 4,4'-dihydroxydiphenylsulfone and 1 weight % of other components. Example 2 Into a reactor, 793 g of phenol, 334 g of sulfuric acid and 16.5 g of phosphinic acid were charged. Dehydration reaction was conducted under a reduced pressure of 74648 to 34658 Pa (560 to 260 mmHg) at 150 to 165°C for 3 hours. When amount of the distillate reached 240 g, 165 g of phenol was added. Dehydration reaction was further continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for 2 hours and 170 g of the distillate was obtained. Then, additional 165 g of phenol was added and dehydration reaction was continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for additional 2 hours. The reaction was finished when amount of the distillate reached 125 g. The reaction mixture was washed with water to remove phenolsulfonic acid and then dried. A mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 82 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 40 weight % of 2,4'-dihydroxydiphenylsulfone, 58 weight % of 4,4'-dihydroxydiphenylsulfone and 2 weight % of other components. Example 3 Into a reactor, 793 g of phenol, 334 g of sulfuric acid, 950 milliliter of mesitylene and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under the refluxing condition for 6 hours. The reaction mixture was then cooled to room temperature, filtered to remove phenolsulfonic acid and dried. A mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 85 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 51 weight % of 2,4'-dihydroxydiphenylsulfone, 48 weight % of 4,4'-dihydroxydiphenylsulfone and 1 weight % of other components. Example 4 Into a reactor, 793 g of phenol, 334 g of sulfuric acid, 950 milliliter of Shellsol A® and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under the refluxing condition for 6 hours. The reaction mixture was then cooled to room temperature, filtered to remove phenolsulfonic acid and dried. A mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 80 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 52 weight % of 2,4'-dihydroxydiphenylsulfone, 47 weight % of 4,4'-dihydroxydiphenylsulfone and 1 weight % of other components. Example 5 Into a reactor, 793 g of phenol, 334 g of sulfuric acid, 940 g of Shellsol AB® and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under the refluxing condition for 6 hours and a specified amount of water was removed. The reaction mixture was then cooled to room temperature. Crystalline precipitate was separated by filtration, washed and dried. Filtrate was neutralized and washed. After removing the solvent from the filtrate, the remaining product was dried and a crystalline product was obtained. Thus, a mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 82 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 51 weight % of 2,4'-dihydroxydiphenylsulfone, 47 weight % of 4,4'-dihydroxydiphenylsulfone and 2 weight % of other components. Example 6 Into a reactor, 368 g of p-cresol, 334 g of sulfuric acid, 2000 milliliter of Shellsol A® and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under the refluxing condition for 2 hours. Then, 384 g of phenol was added and the dehydration reaction was continued for additional 4 hours. The reaction mixture was then cooled to room temperature. Crystalline precipitate was separated, washed with a dilute aqueous alkali solution, then washed with water to remove phenolsulfonic acid and dried. Thus, a mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 81 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 90 weight % of 5-methyl-2,4'-dihydroxydiphenylsulfone (m.p. 179°C) and 10 weight % of other components. Example 7 Into a reactor, 416 g of 2,4-xylenol, 334 g of sulfuric acid, 2000 milliliter of Shellsol AB® and 16.5 g of phosphonic acid were charged. Dehydration reaction was conducted under the refluxing condition for 3 hours. Then, 384 g of phenol was added and the dehydration reaction was continued for additional 4 hours. The reaction mixture was then cooled to room temperature. Crystalline precipitate was separated, washed with a dilute aqueous alkali solution, then washed with water to remove phenolsulfonic acid and dried. Thus, a mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 80 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 87 weight % of 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone (m.p. 176°C) and 13 weight % of other components. Comparative Example 1 Into a reactor, 628 g of phenol and 334 g of sulfuric acid were charged. Dehydration reaction was conducted under a reduced pressure of 74648 to 34658 Pa (560 to 260 mmHg) at 150 to 165°C for 3 hours. When amount of the distillate reached 160 g, 165 g of phenol was added. Dehydration reaction was further continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for 2 hours and 120 g of the distillate was obtained. Then, additional 120 g of phenol was added and dehydration reaction was continued under a reduced pressure of 34658 to 13330 Pa (260 to 100 mmHg) for additional 2 hours. The reaction was finished when amount of the distillate reached 90 g. The reaction mixture was washed with water to remove phenolsulfonic acid and then dried. A mixture of dihydroxydiphenylsulfone isomers was obtained with a yield of 76 mol %. Result of analysis by high performance liquid chromatography showed that the product contained 18 weight % of 2,4'-dihydroxydiphenylsulfone, 77 weight % of 4,4'-dihydroxydiphenylsulfone and 5 weight % of other components. Example 8 Into a mixed solvent containing 205 g of xylene and 45 g of isopropanol, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol and sulfuric acid in Example 1 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40 to 30°C. Crystalline precipitate was separated by filtration and dried to obtain 42 g of 4,4'-dihydroxydiphenylsulfone. Isopropanol was removed from filtrate and crystalline precipitate was separated by filtration and dried to obtain 53 g of 2,4'-dihydroxydiphenylsulfone. Result of analysis by high performance liquid chromatography showed that purities of 4,4'-dihydroxydiphenylsulfone and 2,4'-dihydroxydiphenylsulfone were 97.0 weight % and 80.5 weight %, respectively. Example 9 Into a mixed solvent containing 220 g of xylene and 30 g of isopropanol, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol and sulfuric acid in Example 2 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40 to 30°C. Crystalline precipitate was separated by filtration and dried to obtain 45 g of 4,4'-dihydroxydiphenylsulfone. Isopropanol was removed from filtrate and crystalline precipitate was separated by filtration and dried to obtain 50 g of 2,4'-dihydroxydiphenylsulfone. Result of analysis by high performance liquid chromatography showed that purities of 4,4'-dihydroxydiphenylsulfone and 2,4'-dihydroxydiphenylsulfone were 97.0 weight % and 75.5 weight %, respectively. Example 10 Into a mixed solvent containing 160 g of xylene and 90 g of methyl ethyl ketone, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol and sulfuric acid in Example 3 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40 to 30°C. Crystalline precipitate was separated by filtration and dried to obtain 42 g of 4,4'-dihydroxydiphenylsulfone. Methyl ethyl ketone was removed from filtrate and crystalline precipitate was separated by filtration and dried. After recrystallization from a water/methanol mixed solvent, 43 g of 2,4'-dihydroxydiphenylsulfone was obtained. Result of analysis by high performance liquid chromatography showed that purities of 4,4'-dihydroxydiphenylsulfone and 2,4'-dihydroxydiphenylsulfone were 97.0 weight % and 97.0 weight %, respectively. Example 11 Into a mixed solvent containing 155 g of mesitylene and 95 g of butyl acetate, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol and sulfuric acid in Example 4 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40 to 30°C. Crystalline precipitate was separated by filtration and dried to obtain 45 g of 4,4'-dihydroxydiphenylsulfone. Butyl acetate was removed from filtrate and crystalline precipitate was separated by filtration and dried to obtain 41 g of 2,4'-dihydroxydiphenylsulfone. Result of analysis by high performance liquid chromatography showed that purities of 4,4'-dihydroxydiphenylsulfone and 2,4'-dihydroxydiphenylsulfone were 96.5 weight % and 97.0 weight %, respectively. Example 12 Into a mixed solvent containing 150 g of mesitylene and 90 g of methyl isobutyl ketone, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol, 2,4-xylenol and sulfuric acid in Example 7 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40°C or lower and precipitate formed was removed by filtration. Methyl isobutyl ketone was removed from filtrate to obtain 67 g of 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone. Result of analysis by high performance liquid chromatography showed that purity of the product was 97.5 weight %. Example 13 Into a mixed solvent containing 140 g of xylene and 100 g of butyl acetate, 100 g of the mixture of dihydroxydiphenylsulfone isomers obtained by the reaction of phenol, 2,4-xylenol and sulfuric acid in Example 7 was dispersed and the dispersion was heated to the refluxing condition for 2 hours. The reaction mixture was then cooled to 40°C or lower and precipitate formed was removed by filtration. Butyl acetate was removed from filtrate to obtain 65 g of 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone. Result of analysis by high performance liquid chromatography showed that purity of the product was 97.0 weight %.

Claims: A method of producing a 2,4'-dihydroxydiphenylsulfone which comprises mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C. A method of producing a 2,4'-dihydroxydiphenylsulfone as claimed in Claim 1, wherein one or more kinds of phenol and sulfuric acid are mixed and heated to a temperature of 140 to 170°C under reduced pressure in the absence of a solvent to bring them into reaction with each other. A method of producing a 2,4'-dihydroxydiphenylsulfone as claimed in Claim 1, wherein one or more kinds of phenol and sulfuric acid are mixed and heated to bring them into reaction with each other in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C while water formed by the reaction is removed from the reaction system by azeotropic distillation. A method of producing a 2,4'-dihydroxydiphenylsulfone as claimed in Claim 1, 2 or 3, wherein said 2,4'-dihydroxydiphenylsulfone is 2,4'-dihydroxydiphenylsulfone obtained by using phenol as said phenol. A method of producing a 2,4'-dihydroxydiphenylsulfone as claimed in Claim 1, 2 or 3, wherein said 2,4'-dihydroxydiphenylsulfone is 5-methyl-2,4'-dihydroxydiphenylsulfone obtained by using phenol and p-cresol as said phenols. A method of producing a 2,4'-dihydroxydiphenylsulfone as claimed in Claim 1, 2 or 3, wherein said 2,4'-dihydroxydiphenylsulfone is 3,5-dimethyl-2,4'-dihydroxydiphenylsulfone obtained by using phenol and 2,4-xylenol as said phenols. A method of producing a high purity 2,4'-dihydroxydiphenylsulfone which comprises producing a crude 2,4'-dihydroxydiphenylsulfone by mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C and purifying the crude 2,4'-dihydroxydiphenylsulfone thus produced using a mixed solvent containing 5 to 20 weight % of at least one kind selected from the group consisting of lower aliphatic alcohols and 95 to 80 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen. A method of producing a high purity 2,4'-dihydroxydiphenylsulfone which comprises producing a crude 2,4'-dihydroxydiphenylsulfone by mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C and purifying the crude 2,4'-dihydroxydiphenylsulfone thus produced using a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of ketones and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen. A method of producing a high purity 2,4'-dihydroxydiphenylsulfone which comprises producing a crude 2,4'-dihydroxydiphenylsulfone by mixing and heating one or more kinds of phenol and sulfuric acid to bring them into reaction with each other in the presence of at least one kind of compound selected from the group consisting of phosphonic acid, phosphinic acid and salts thereof as catalyst in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130 to 200°C and purifying the crude 2,4'-dihydroxydiphenylsulfone thus produced using a mixed solvent containing 10 to 40 weight % of at least one kind selected from the group consisting of esters of acetic acid and 90 to 60 weight % of at least one kind selected from the group consisting of aromatic hydrocarbons not containing halogen. A method of producing a high purity 2,4'-dihydroxydiphenylsulfone as claimed in Claim 7, 8 or 9, wherein said high purity 2,4'-dihydroxydiphenylsulfone is high purity 2,4'-dihydroxydiphenylsulfone obtained by using phenol as said phenol.

Inventors: HOSODA MASAAKI, KUROSE MIKIHIKO, MAKINO MASAHIRO, SAITO HAJIME, SASADA YOSHIHIRO, HOSODA, MASAAKI, KUROSE, MIKIHIKO, MAKINO, MASAHIRO, SAITO, HAJIME, SASADA, YOSHIHIRO
Applicants: NICCA CHEMICAL CO, NICCA CHEMICAL CO., LTD.
Application year: 1993
Main classification: C07C315
IPC codes: C07C315, C07C317