# US 2014/0194618 A1 · Method For Preparing Cellulose Ether Having Low Degree Of Polymerization And Cellulose Ether Prepared Thereby

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- Number: US 2014/0194618 A1
- Document ID: US20140194618A1
- Status: Published application
- Kind: A1
- Application number: 14/150,793
- Filed: 2014-01-09
- Published: 2014-07-10
- Earliest claimed: 2013-01-09
- Assignees: Shin-Etsu Chemical Co., Ltd.
- Applicants: Shin-Etsu Chemical Co., Ltd.
- Inventors: Mitsuo NARITA; Yuichi Nishiyama
- Web page: https://patentgrep.com/patent/US20140194618A1

## CPC

- C08B 11/08: with hydroxylated hydrocarbon radicals; Esters, ethers, or acetals thereof
- C08B 1/06: Rendering cellulose suitable for etherification {(etherification per se C08B11/00)}
- C08B 1/08: Alkali cellulose
- C08B 11/02: Alkyl or cycloalkyl ethers
- C08B 11/20: Post-etherification treatments of chemical or physical type, {e.g. mixed etherification in two steps}, including purification
- C08B: POLYSACCHARIDES; DERIVATIVES THEREOF (polysaccharides containing less than six saccharide radicals attached to each other by glycosidic linkages C07H; fermentation or enzyme-using processes C12P19/00; sugar industry C13; production of cellulose D21)

## Abstract

Provided is a method for preparing a cellulose ether having a low degree of polymerization and undergoing less yellowing and a cellulose ether prepared thereby. Specifically, provided is a method for preparing a cellulose ether having a low degree of polymerization, the method including a step of bringing pulp and an alkali metal hydroxide solution into contact with each other or mixing them to obtain a corresponding alkali cellulose, a first depolymerization step of reacting the alkali cellulose with oxygen to adjust a viscosity reduction percentage of the alkali cellulose to from 10 to 95%, a step of reacting the depolymerized alkali cellulose with an etherifying agent, a step of washing and drying the reaction product to obtain a cellulose ether, and a second depolymerization step of bringing the cellulose ether into contact with hydrochloric acid to adjust a viscosity reduction percentage of the cellulose ether from 40 to 99.9%.

## Claims

### Claim 1

A method for preparing a cellulose ether having a low degree of polymerization, the method comprising:
a step of bringing pulp and an alkali metal hydroxide solution into contact with each other or mixing them to obtain a corresponding alkali cellulose,
a first depolymerization step of reacting the alkali cellulose with oxygen to adjust a viscosity reduction percentage of the alkali cellulose to from 10 to 95% to obtain a depolymerized alkali cellulose,
a step of reacting the depolymerized alkali cellulose with an etherifying agent to obtain a reaction product,
a step of washing and drying the reaction product to obtain a cellulose ether of which an aqueous 2% by weight solution has a viscosity of from 30 to 10000 mPa·s, and
a second depolymerization step of bringing the cellulose ether into contact with hydrochloric acid to adjust a viscosity reduction percentage of the cellulose ether to from 40 to 99.9%.

### Claim 2 (depends on 1)

The method for preparing a cellulose ether having a low degree of polymerization according to claim 1, wherein a ratio of the viscosity reduction percentage in the second depolymerization step to the viscosity reduction percentage in the first depolymerization step is from 0.7 to 8.0.

### Claim 3 (depends on 1)

The method for preparing a cellulose ether having a low degree of polymerization according to claim 1, wherein the cellulose ether is an alkyl cellulose, a hydroxyalkyl cellulose or a hydroxyalkylalkyl cellulose.

### Claim 4 (depends on 2)

The method for preparing a cellulose ether having a low degree of polymerization according to claim 2, wherein the cellulose ether is an alkyl cellulose, a hydroxyalkyl cellulose or a hydroxyalkylalkyl cellulose.

### Claim 5 (depends on 1)

A cellulose ether having a low degree of polymerization obtained by the method as claimed in claim 1.

### Claim 6 (depends on 2)

A cellulose ether having a low degree of polymerization obtained by the method as claimed in claim 2.

### Claim 7 (depends on 3)

A cellulose ether having a low degree of polymerization obtained by the method as claimed in claim 3.