Method for producing water-soluble cellulose ether having low degree of polymerization and method for producing film coating composition comprising same

Patent metadata

Field	Value
Publication number	US-9926385-B2
Application number	US-201414447846-A
Country	US
Kind code	B2
Filing date	Jul 31, 2014
Priority date	Aug 12, 2013
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

Provided are a method for producing a water-soluble cellulose ether having a low degree of polymerization and enhanced whiteness, and the like. The method includes the steps of: bringing a pulp powder having a multiplication product of less than 0.004 mm 2 which is obtained by multiplying a number-average fiber length by a number-average fiber width, each measured with a Kajaani fiber length analyzer, into contact with an alkali metal hydroxide to obtain an alkali cellulose; reacting the alkali cellulose with an etherifying agent to obtain a crude water-soluble cellulose ether having a high degree of polymerization; purifying the crude water-soluble cellulose ether; drying the purified water-soluble cellulose ether; grinding the dried water-soluble cellulose ether into a water-soluble cellulose ether powder; and depolymerizing the water-soluble cellulose ether powder to obtain the water-soluble cellulose ether having a low degree of polymerization.

First claim

The invention claimed is:

1. A method for producing a water-soluble cellulose ether having a low degree of polymerization, comprising the steps of:
bringing a pulp powder having a multiplication product of less than .004 mm 2 which is obtained by multiplying a number-average fiber length by a number-average fiber width each measured with a fiber length analyzer, into contact with an alkali metal hydroxide to obtain an alkali cellulose;
reacting the alkali cellulose with an etherifying agent to obtain a crude water-soluble cellulose ether having a high degree of polymerization;
purifying the crude water-soluble cellulose ether having a high degree of polymerization to obtain a purified water-soluble cellulose ether having a high degree of polymerization;
drying the purified water-soluble cellulose ether having a high degree of polymerization to obtain a dried water-soluble cellulose ether having a high degree of polymerization;
grinding the dried water-soluble cellulose ether having a high degree of polymerization into a water-soluble cellulose ether powder having a high degree of polymerization; and
depolymerizing the water-soluble cellulose ether powder having a high degree of polymerization to obtain the water-soluble cellulose ether having a low degree of polymerization.

2. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder is derived from eucalyptus.

3. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has been obtained by grinding a pulp having an intrinsic viscosity of less than 900 ml/g.

4. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has a loose bulk density of from 70 to 300 g/l.

5. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has a weight-average particle size D 50 of not greater than 250 μm as measured by sifting with a ro-tap sieve shaker.

6. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein a viscosity at 20° C. of an aqueous 2% by weight solution of the cellulose ether having a low degree of polymerization thus obtained is not greater than 20 mPa·s.

7. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein a viscosity at 20° C. of an aqueous 2% by weight solution of the cellulose ether having a low degree of polymerization thus obtained is from 3 to 15 mPa·s.

8. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has a multiplication product of greater than 0.001 mm 2 .

9. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has a number-average fiber length from 0.05 to 0.6 mm.

10. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the pulp powder has a number-average fiber width from 0.005 to 0.050 mm.

11. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein the concentration of alkali metal hydroxide in the alkali metal hydroxide solution is from 10 to 60% by weight.

12. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein a viscosity at 20° C. of an aqueous 2% by weight solution of the dried water-soluble cellulose ether having a high degree of polymerization is from 50 to 3000 mPa·s.

13. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein purifying the crude water-soluble cellulose ether having a high degree of polymerization comprises washing the crude water-soluble cellulose ether having a high degree of polymerization to an ash content of less than 0.5% by weight.

14. The method for producing a water-soluble cellulose ether having a low degree of polymerization according to claim 1 , wherein depolymerizing the water-soluble cellulose ether powder having a high degree of polymerization comprises adding hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or combinations thereof.

15. A method for producing a film coating composition, comprising the respective steps of the method for producing a water-soluble cellulose ether having a low degree of polymerization as claimed in claim 1 and further comprising a step of dissolving the produced water-soluble cellulose ether having a low degree of polymerization in a solvent.

16. The method for producing a film coating composition according to claim 15 , wherein a content of the cellulose ether in the composition for film coating is from 0.5 to 30% by weight.

Assignees

• Shinetsu Chemical Co

Inventors

• Kitamura Akira
• Narita Mitsuo
• Yokosawa Takuya
• Nishiyama Yuichi

Classifications

• C08B11/00

  Preparation of cellulose ethers {(rendering cellulose suitable for etherification C08B1/06)} · CPC title

• D21H19/52

  Cellulose; Derivatives thereof · CPC title

• C08B1/06

  Rendering cellulose suitable for etherification {(etherification per se C08B11/00)} · CPC title

• D21H19/34

  comprising cellulose or derivatives thereof · CPC title

• C08B1/08

  Alkali cellulose · CPC title