Method for producing polyvinyl alcohol

Patent metadata

Field	Value
Publication number	US-10000586-B2
Application number	US-201415101142-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 6, 2013
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A method for producing polyvinyl alcohols by means of catalytic reactions of alcoholic polyvinyl ester solutions in extruders, wherein the polyvinyl esters are based exclusively on ethylenically unsaturated monomers and wherein one or more neutralizing agents are added to the product of the catalytic reaction.

First claim

The invention claimed is:

1. A method for producing polyvinyl alcohols comprising catalytic reaction of alcoholic polyvinyl ester solutions in extruders, wherein the polyvinyl esters are based solely on ethylenically unsaturated monomers and the polyvinyl ester solutions do not comprise polyvinyl esters containing a polyether unit or a polyether group, wherein one or more neutralizing agents are added to the product of the catalytic reaction while said product is still in the extruder, and wherein the polyvinyl alcohols are partially or fully saponified, have a degree of hydrolysis from 70 to 99.5 mol. %, and have only one distinct maximum in a saponification number distribution reversed phase gradient HPLC trace.

2. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the polyvinyl esters are homopolymers or copolymers of one or more vinyl esters of aliphatic carboxylic acids having from 1 to 13 carbon atoms and optionally up to 50% by weight of one or more comonomers selected from the group consisting of olefins, acrylic acid esters or methacrylic acid esters of unbranched or branched alcohols having from 1 to 22 carbon atoms, isopropenyl acetate, N-vinylpyrrolidone, N-vinylcaprolactam, vinyl formamide, ethylenically unsaturated mono- and di-carboxylic acids, maleic anhydride and ethylenically unsaturated carboxylic acid amides.

3. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the content of polyvinyl ester in an alcoholic polyvinyl ester solution in which the catalytic reaction takes place is from 20 to 80% by weight.

4. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the catalytic reaction of the alcoholic polyvinyl ester solutions takes place in the presence of one or more acidic or alkaline catalysts.

5. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein one or more polyvinyl esters and one or more catalysts are introduced in the form of a premixture into an extruder.

6. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the extruder comprises from 5 to 18 cylinders.

7. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the extruder comprises feed elements, optionally kneading disks and optionally mixing elements, but no backfeed elements.

8. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the extruder comprises the following zones in the following order:
an intake zone for feeding of the polyvinyl esters, or a premixture of one or more polyvinyl esters and one or more catalysts (1st zone); optionally an intake zone for the catalyst (2nd zone); mixing zone (3rd zone); reaction zone (4th zone); neutralization zone (5th zone); optional degassing zone (6th zone); and discharge zone (7th zone).

9. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the extruder comprises one or more screws and the screws are operated at a speed of rotation of from 10 to 1200 revolutions per minute.

10. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the dwell time of the reaction mixture in the extruder is from 0.2 to 5 minutes.

11. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the polyvinyl ester solutions do not comprise polyvinyl esters that are graft copolymers.

12. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the polyvinyl alcohols have a degree of hydrolysis from 70 to 95 mol. %.

13. The method for producing polyvinyl alcohols as claimed in claim 1 , wherein the polyvinyl alcohols have a degree of hydrolysis from 85 to 95 mol. %.

Assignees

• Wacker Chemie Ag

Inventors

• Köhler Thomas
• Belitzer Martina
• Windt Oliver

Classifications

• C08F8/12 Primary

  Hydrolysis · CPC title

• C08F18/08

  Vinyl acetate · CPC title