Claims
- 1. A process for preparing water-soluble salts of poly-.alpha.-hydroxyacrylic acid or its alkyl derivatives, comprising:
- (a) thermally dehydrochlorinating, in the gas phase in the presence of a catalyst, .alpha.,.beta.-dichloro-propionic acid, or its alkyl derivatives, to the corresponding .alpha.-chloro-acrylic acid;
- (b) polymerizing the resulting .alpha.-chloro-acrylic acid in water in the presence of a free radical polymerization catalyst to obtain a solid product; and
- (c) neutralizing the solid product with an aqueous solution of an alkali metal hydroxide or ammonium hydroxide.
- 2. The process according to claim 1, wherein the thermal dehydrochlorination of .alpha.,.beta.-dichloro-propionic acid to .alpha.-chloro-acrylic acid is carried out in the presence of calcined alumina as the catalyst and at a temperature of between 200.degree. and 400.degree. C.
- 3. The process according to claim 1, wherein the .alpha.,.beta.-dichloro-propionic acid is diluted with an inert solvent.
- 4. The process according to claim 3, wherein the solvent is a chlorinated hydrocarbon or water.
- 5. The process according to claim 1 wherein the polymerization of the .alpha.-chloro-acrylic acid in water is carried out in the presence of potassium persulphate as the polymerization catalyst.
- 6. The process according to claim 5 wherin the potassium persulphate/.alpha.-chloro-acrylic acid molar ratio is between 0.001 and 0.1 moles of potassium persulphate per mole of .alpha.-chloro-acrylic acid.
- 7. The process according to claim 6 wherein the molar ratio is between 0.005 and 0.05 moles of potassium persulphate per mole of .alpha.-chloro-acrylic acid.
- 8. The process according to claim 1 wherein the polymerization of the .alpha.-chloro-acrylic acid in water is carried out at a temperature of between 40.degree. and 100.degree. C.
- 9. The process according to claim 8 wherein the polymerization of the .alpha.-chloro-acrylic acid in water is carried out at a temperature of between 60.degree. and 80.degree. C.
- 10. The process according to claim 1 wherein the starting .alpha.,.beta.-dichloro-propionic acid and its alkyl derivatives correspond to the general formula ##STR3## wherein R.sub.1 and R.sub.2 independently represent a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms.
- 11. The process according to claim 1 wherein the .alpha.-chloro-acrylic acid obtained from the dehydrochlorination is condensed before it is polymerized.
- 12. A process for making a poly-.alpha.-hydroxyacrylic compound or its alkyl derivatives which comprises treating the corresponding .alpha.-chloroacrylic acid in an aqueous medium in the presence of a free radical polymerization catalyst to bring about polymerization and form a solid product.
- 13. The process according to claim 12 wherein .alpha.-chloroacrylic acid is treated.
- 14. The process according to claim 13 wherein the polymerization of the .alpha.-chloro-acrylic acid in the aqueous medium is carried out at a temperature of between 40.degree. and 100.degree. C.
- 15. A process according to claim 13 wherein the free radical polymerization catalyst is selected from the group consisting of organic peroxides, inorganic per-compounds, redox initiators and diazo compounds.
- 16. A process according to claim 15 wherein the organic peroxide is selected from the group consisting of benzoyl peroxide, dibenzoyl peroxide and cumyl hydroperoxide.
- 17. A process according to claim 15 wherein the inorganic per-compound is selected from the group consisting of hydrogen peroxide, sodium perborate and potassium persulphate.
- 18. A process according to claim 17 wherein the polymerization catalyst is potassium persulphate.
- 19. A process according to claim 18 wherein the potassium persulphate/.alpha.-chloroacrylic acid molar ratio is between 0.001 and 0.1 moles of potassium persulphate per mole of .alpha.-chloroacrylic acid.
- 20. A process according to claim 19 wherein the molar ratio is between 0.005 and 0.05 moles of potassium persulphate per mole of .alpha.-chloroacrylic acid.
- 21. In a process for making poly-.alpha.-oxyacrylic acid by contacting a solution of .alpha.-chloroacrylic acid with radical-yielding polymerization catalysts, heating and thereby hydrolyzing the resulting poly-.alpha.-chloroacrylic acid in aqueous solution with the resultant precipitation of solid poly-.alpha.-oxyacrylic acid, the improvement which comprises contacting and heating an aqueous .alpha.-chloroacrylic acid solution with the radical-yielding polymerization catalysts for a period of two hours while leaving the resulting poly-.alpha.-chloroacrylic acid unseparated, said heating being to temperatures within the range 40.degree. and 100.degree. C.
- 22. A process as claimed in claim 21, wherein potassium peroxo-disulfate-(VI) is used as the radical-yielding polymerization catalyst in proportions within the range 0.001 and 0.1 moles potassium peroxo-disulfate-(VI) per mole of .alpha.-chloroacrylic acid.
- 23. A process as claimed in claim 21, wherein the aqueous .alpha.-chloroacrylic acid solution having a radical-yielding polymerization catalyst or a redox system dissolved therein is maintained at temperatures within the range 40.degree. and 80.degree. C.
- 24. A process as claimed in claim 21, wherein an aqueous .alpha.-chloroacrylic acid solution containing the radical-yielding polymerization catalyst as claimed in claim 22 is heated to temperatures within the range 40.degree. and 100.degree. C.
Priority Claims (1)
Number |
Date |
Country |
Kind |
68037 |
Jul 1973 |
LUX |
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CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of application Ser. No. 489,718, filed July 18, 1974, now abandoned.
US Referenced Citations (16)
Continuations (1)
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Number |
Date |
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Parent |
489718 |
Jul 1974 |
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