Process for the manufacture of bisphenol-A

Abstract

A process for producing a dihydric phenol preferably bisphenol-A consisting of the steps of (1) formulating reaction ingredients of phenol, acetone, recycle bisphenol A, impurities, an acid catalyst and water, (2) reacting the ingredients to form a product mix consisting of bisphenol-A, unreacted phenol, by-products, acetone and water, (3) crystallizing the product mix forming a slurry of bisphenol-A/phenol adduct crystals solid phase, (4) separating the solid phase from the liquid phase by filtration, (5) removing the phenol from the bisphenol-A/phenol adduct to obtain a crude bisphenol-A, and (6) purifying the crude bisphenol by fractional melt crystallization to obtain a bisphenol-A of at least 99.5% purity. Optionally, the process may include the steps of recycling the liquid phase from step (3) back to the reaction step after removal of the water of reaction, and further removing entrained phenol and acetone from the removed water of reaction which phenol and acetone is also recycled back to the reaction step.

What is claimed is:  
     
       1. A process for preparing a dihydric phenol comprising the steps of (1) formulating the reactor ingredients for forming a dihydric phenol, (2) reacting the ingredients to form a product mixture comprising dihydric phenol, unreacted phenol, carbonyl compound and water, (3) subjecting the product mixture to crystallization wherein a slurry is formed comprising a mother liquor phase and a solid phase, said solid phase is an adduct of dihydric phenol and phenol, (4) separating the solid dihydric phenol and phenol phase from the liquid phase, (5) extracting the phenol from the solid dihydric phenol and phenol phase to obtain a crude dihydric phenol, and (6) purifying the crude dihydric phenol by fractional melt crystallization to obtain a dihydric phenol of at least about 95% purity. 
     
     
       2. The process of claim  1  wherein the dihydric phenol is bisphenol-A 
     
     
       3. The process of claim  1  wherein the promoter is a mecaptan. 
     
     
       4. The process of claim  1  wherein the mother liquor from the crystallizing step is dehydrated to remove water of reaction, a portion of unreacted carbonyl compound and a portion of phenol. 
     
     
       5. The process of claim  4  wherein the dehydrated mother liquor is recycled to the formulating reactor. 
     
     
       6. The process of claim  4  wherein the process consists essentially of the additional steps of (a) extracting entrained phenol and carbonyl compound from the water of reaction, (b) recycling the extracted phenol and carbonyl compound to the reaction step, and (c) disposing of the reaction waste water. 
     
     
       7. The process of claim  4  wherein the carbonyl compound is acetone. 
     
     
       8. A process for preparing polycarbonate of high purity comprising preparing bisphenol A by the process of claim  2 , melting the bisphenol A, mixing the molten bisphenol A with diphenyl carbonate, reacting the molten bisphenol A with the diphenyl carbonate. 
     
     
       9. A process for making an article comprising preparing a high purity polycarbonate by the process of claim  8  and forming the polycarbonate prepared into the article. 
     
     
       10. The process of claim  9  wherein the article is formed by injection molding. 
     
     
       11. An article made by the process of claim  10  wherein the article is an optical disk. 
     
     
       12. An article made by the process of claim  10  wherein the article is an electronic component. 
     
     
       13. An article made by the process of claim  10  wherein the article is a lens. 
     
     
       14. The process of claim  9  wherein the article is formed by extrusion. 
     
     
       15. The process of claim  10  wherein the article is formed by vacuum forming. 
     
     
       16. The process of claim  1  wherein the reaction ingredients comprise phenol, acetone and a promoter.