A process for obtaining 4,4'-dichlorodiphenyl sulfone from an organic mixture comprising 4,4'-dichlorodiphenyl sulfone and a linear C 6 to C 10 carboxylic acid as organic solvent, comprising: (a) cooling the organic mixture by (a1a) mixing the organic mixture with water in a crystallization vessel to obtain a liquid mixture; (a1b) cooling the liquid mixture obtained in (a1a) to a temperature below the saturation point of 4,4'-dichlorodiphenyl sulfone by (i) reducing the pressure in the crystallization vessel to a pressure at which the water starts to evaporate, (ii) condensing the evaporated water by cooling, (iii) mixing the condensed water into the liquid mixture in the crystallization vessel, to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone; or by bringing the organic mixture into contact with at least one coolable surface and thereby reducing the temperature in the organic mixture with a cooling rate in the range from 5 to 50 K/h until a temperature in the range from 0 to 30°C is reached, wherein the organic mixture and the at least one coolable surface have a temperature difference which is kept during the whole cooling process in the range from1 to 30 K to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone. (b) carrying out a solid-liquid-separation of the suspension obtained in (a1b) or in to obtain a residual moisture containing solid 4,4'-dichlorodiphenyl sulfone as product and mother liquor comprising the organic solvent and water. (a) cooling the organic mixture by (a1a) mixing the organic mixture with water in a crystallization vessel to obtain a liquid mixture; (a1b) cooling the liquid mixture obtained in (a1a) to a temperature below the saturation point of 4,4'-dichlorodiphenyl sulfone by (i) reducing the pressure in the crystallization vessel to a pressure at which the water starts to evaporate, (ii) condensing the evaporated water by cooling, (iii) mixing the condensed water into the liquid mixture in the crystallization vessel, to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone; or by bringing the organic mixture into contact with at least one coolable surface and thereby reducing the temperature in the organic mixture with a cooling rate in the range from 5 to 50 K/h until a temperature in the range from 0 to 30°C is reached, wherein the organic mixture and the at least one coolable surface have a temperature difference which is kept during the whole cooling process in the range from1 to 30 K to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone. (a1a) mixing the organic mixture with water in a crystallization vessel to obtain a liquid mixture; (a1b) cooling the liquid mixture obtained in (a1a) to a temperature below the saturation point of 4,4'-dichlorodiphenyl sulfone by (i) reducing the pressure in the crystallization vessel to a pressure at which the water starts to evaporate, (ii) condensing the evaporated water by cooling, (iii) mixing the condensed water into the liquid mixture in the crystallization vessel, to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone; or by (i) reducing the pressure in the crystallization vessel to a pressure at which the water starts to evaporate, (ii) condensing the evaporated water by cooling, (iii) mixing the condensed water into the liquid mixture in the crystallization vessel, bringing the organic mixture into contact with at least one coolable surface and thereby reducing the temperature in the organic mixture with a cooling rate in the range from 5 to 50 K/h until a temperature in the range from 0 to 30°C is reached, wherein the organic mixture and the at least one coolable surface have a temperature difference which is kept during the whole cooling process in the range from1 to 30 K to obtain a suspension comprising crystallized 4,4'-dichlorodiphenyl sulfone. (b) carrying out a solid-liquid-separation of the suspension obtained in (a1b) or in to obtain a residual moisture containing solid 4,4'-dichlorodiphenyl sulfone as product and mother liquor comprising the organic solvent and water.