Processes for cross-linking cellulose ethers under mild conditions

• US 9,024,011 B2
• Filed: 09/02/2010
• Issued: 05/05/2015
• Est. Priority Date: 06/02/2010
• Status: Expired due to Fees

• Current Assignee: University of Calcutta
• Original Assignee: University of Calcutta
• Inventors: Kundu, Patit Paban, Singh, Ratan Pal
• Primary Examiner(s): Lewis, Patrick
• Assistant Examiner(s): White, Everett
• Application Number:
  US13/377,493
• Publication Number:
  US 20120095202A1
• Time in Patent Office: 1,706 Days
• Field of Search: 536/85, 536/88, 536/90, 536/91, 536/95, 536/96, 536/97, 536/98, 536/99, 536/100, 536/124
• US Class Current: 536/124
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 67/0093 Chemical modification
• CPC Class Codes: B01D 67/00931 by introduction of specific groups after membrane formation, e.g. by grafting
• CPC Class Codes: B01D 71/22 Cellulose ethers
• CPC Class Codes: C08G 18/6484 Polysaccharides and derivatives thereof
• CPC Class Codes: C08J 2301/26 Cellulose ethers
• CPC Class Codes: C08J 2301/28 Alkyl ethers
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets

Abstract

The present technology provides processes for cross-linking cellulose ethers under mild conditions. The processes include exposing a substantially dry cellulose ether film to a polyisocyanate to provide a cross-linked cellulose ether film, wherein the substantially dry cellulose ether film comprises alkoxide groups on the cellulose. The resulting cellulose ether films are highly cross-linked by polyurethane linkages and may be used as membranes in a variety of applications.

Claims

1. A process comprising exposing a substantially dry cellulose ether film to a polyisocyanate in a suspension of a base in a suitable organic solvent and drying the resulting cellulose ether film to provide a cross-linked cellulose ether film,

wherein the substantially dry cellulose ether film comprises alkoxide groups on the cellulose and no more than about 0.1% water by weight.

2. The process of claim 1 wherein the cellulose ether is selected from the group consisting of methyl cellulose, ethyl cellulose, 2-hydroxyethyl cellulose, 2-hydroxypropyl cellulose, 3-hydroxybutyl cellulose, carboxymethyl cellulose, carboxymethyl 2-hydroxyethyl cellulose, 2-hydroxyethyl methyl cellulose, 2-hydroxybutyl methyl cellulose, and 2-hydroxyethyl ethyl cellulose.

3. The process of claim 1 wherein the alkoxide groups on the cellulose are alkali metal alkoxide groups.

4. The process of claim 3 wherein the alkali metal is selected from the group consisting of lithium, sodium, potassium, and cesium.

5. The process of claim 1 wherein the polyisocyanate is an alkyl diisocyanate, an aryl diisocyanate, or a poly(diphenylmethane diisocyanate).

6. The process of claim 5 wherein the polyisocyanate is selected from the group consisting of 1,6-hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

7. The process of claim 1 wherein the base is an alkali metal hydroxide.

8. The process of claim 1 wherein the suitable organic solvent is selected from the group consisting of THF and acetone.

9. The process of claim 1 wherein the substantially dry cellulose ether film is exposed to a solution of polyisocyanate ranging in concentration from about 1% to about 100% by weight.

10. The process of claim 1 carried out in the absence of an isocyanate catalyst, added heat or added pressure.

11. The process of claim 1 carried out at ambient temperature.

12. A process comprising treating a methyl cellulose film with a suspension of alkali metal hydroxide in an organic solvent, drying the film to provide a substantially dry methyl cellulose film comprising alkali metal alkoxide groups on the cellulose and no more than about 0.1% water by weight, and exposing said film to a diisocyanate in a suitable organic solvent to provide a cross-linked cellulose ether film.