Method for producing polyvinyl alcohol

Patent metadata

Field	Value
Publication number	US-2021189028-A1
Application number	US-201917057556-A
Country	US
Kind code	A1
Filing date	Jul 3, 2019
Priority date	Jul 27, 2018
Publication date	Jun 24, 2021
Grant date	—

Abstract

Provided is a method for producing a polyvinyl alcohol having improved mechanical strength without significantly impairing productivity. A method for producing a polyvinyl alcohol having an average degree of polymerization of 5.0×103 or more and 1.5×104 or less, the method including steps of: subjecting a vinyl ester-based monomer to suspension polymerization at a polymerization temperature of 10° C. or more and 50° C. or less with a polymerization rate of 10% or more and 70% or less to obtain a vinyl ester-based polymer; dissolving the vinyl ester-based polymer in an alcohol-based solvent; and carrying out a saponification reaction by adding a saponification catalyst to an alcohol-based solution of the dissolved vinyl ester-based polymer.

First claim

1 . A method for producing a polyvinyl alcohol having an average degree of polymerization of 5.0×10 3 or more and 1.5×10 4 or less, the method comprising steps of:
subjecting a vinyl ester-based monomer to suspension polymerization at a polymerization temperature of 10° C. or more and 50° C. or less with a polymerization rate of 10% or more and 70% or less to obtain a vinyl ester-based polymer;
dissolving the vinyl ester-based polymer in an alcohol-based solvent to provide an alcohol-based solution containing the vinyl ester-based polymer; and
carrying out a saponification reaction by adding a saponification catalyst to the alcohol-based solution.

2 . The method for producing a polyvinyl alcohol according to claim 1 , wherein a polymerization temperature (T) and a polymerization rate (X) of the vinyl ester-based monomer in the suspension polymerization are set so as to satisfy a following equation (1):
X≤− 0.05 T 2 +1.5 T+ 60  Equation (1)
in which equation (1), T represents a polymerization temperature (° C.), and X represents a polymerization rate (% by mass) (0<X<100).

3 . The method for producing a polyvinyl alcohol according to claim 1 , wherein the vinyl ester-based polymer used in the step of dissolving the vinyl ester-based polymer in the alcohol-based solvent has a median diameter of from 100 to 800 μm.

4 . The method for producing a polyvinyl alcohol according to claim 1 , wherein the suspension polymerization comprises a step of adding a modified polyvinyl alcohol having a structure represented by a following chemical formula I:

in which chemical formula I, n represents an integer of 0 or more and 3 or less, and X 1 and X 2 each independently represent an alkyl group having 1 to 12 carbon atoms, a hydrogen atom or a metal atom.

5 . The method for producing a polyvinyl alcohol according to claim 1 , wherein the vinyl ester-based polymer used in the step of dissolving the vinyl ester-based polymer in the alcohol-based solvent has a CV value of from 0.4 to 0.9, the CV value (σ50/d50×100) being calculated from a standard deviation (σ50) based on a median diameter (d50), the standard deviation being measured from a particle size distribution on volume basis as measured by a laser diffraction/scattering particle size distribution measurement method.

6 . The method for producing a polyvinyl alcohol according to claim 1 , wherein the suspension polymerization comprises a step of adding a polymerization terminator to stop the polymerization of the vinyl ester-based monomer.

7 . The method for producing a polyvinyl alcohol according to claim 6 , wherein the polymerization terminator comprises a compound having a structure represented by the following chemical formula II:

in which chemical formula II, R 1 , R 2 , R 3 and R 4 each independently represent a hydrogen atom; a lower alkyl group having 1 to 8 carbon atoms; a lower alkyl group having 1 to 8 carbon atoms, a lower alkyl group having 1 to 8 carbon atoms with a carbonyl group and/or an amide group; or a halogen group.

8 . The method for producing a polyvinyl alcohol according to claim 6 , wherein the polymerization terminator comprises an unsaturated carboxylic acid compound having a conjugated diene structure represented by the following chemical formula III:

in which formula III, R 5 represents a hydrogen atom; a lower alkyl group having 1 to 4 carbon atoms; a phenyl group; or an alkylphenyl group having a lower alkyl group having 1 to 4 carbon atoms; and X 3 represents an alkyl group having 1 to 8 carbon atoms; a hydrogen atom; or a metal atom.

9 . The method for producing a polyvinyl alcohol according to claim 6 , wherein the polymerization terminator comprises a nitroso compound.

10 . The method for producing a polyvinyl alcohol according to claim 1 , comprising using an oxygen-containing gas as the polymerization terminator.

11 . The method for producing a polyvinyl alcohol according to claim 1 , wherein the step of dissolving the vinyl ester-based polymer in the alcohol-based solvent comprises a step of adjusting a non-volatile component to 30 to 90% by mass.

Assignees

• Denka Company Ltd

Inventors

• Yamashita Akihiro

Classifications

• C08F8/12 Primary

  Hydrolysis · CPC title

• C08L31/04

  Homopolymers or copolymers of vinyl acetate · CPC title

• C08F216/06

  Polyvinyl alcohol {; Vinyl alcohol} · CPC title

• C08F18/08

  Vinyl acetate · CPC title

• C08F18/04 Primary

  Vinyl esters · CPC title