Process for preparing methylhydroxyalkylcellulose having a small number of coloured particles

• US 20070210014A1
• Filed: 09/15/2006
• Published: 09/13/2007
• Est. Priority Date: 09/17/2005
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: Wolff Cellulosics GmbH & Co. KG (Dow, Inc.)
• Inventors: Kowollik, Martin, Dannhorn, Wolfgang, Schlesiger, Hartwig, Klohr, Erik-Andreas, Sonnenberg, Gerd, Kranz, Bernhard, Holste, Helmut
• Granted Patent: US 8,197,699 B2
• Time in Patent Office: Days
• US Class Current: 210/784
• CPC Class Codes: B01D 33/06 with rotary cylindrical filtering surfaces, e.g. hollow drums B01D33/044 takes precedence ; rotating drums for paper-making D21B
• CPC Class Codes: B01D 33/073 arranged for inward flow filtration
• CPC Class Codes: C08B 11/193 Mixed ethers, i.e. ethers with two or more different etherifying groups
• CPC Class Codes: C08B 11/20 Post-etherification treatments of chemical or physical type, e.g. mixed etherification in two steps, including purification
• CPC Class Codes: C08B 11/22 Isolation

Abstract

The present invention describes a process for preparing methylhydroxyalkylcellulose having a small number of coloured particles by separation of methylhydroxyalkylcellulose from aqueous suspension with subsequent washing of the methylhydroxyalkylcellulose using a specially equipped rotary pressure filter.

Claims

1. A rotary pressure filter which comprises a plurality of zones separated from one another by separation plates, including at least one drying zone characterized in that the separation plates which seal off the drying zone(s) comprise heat-resistant, abrasion-resistant plastic and in that the separation plates which seal off the other zones comprise plastics having good sliding and abrasion properties.

2. The rotary pressure filter according to claim 1, wherein the plastic of the separation plates which seal off the drying zone(s) is heat resistant above 145°

C., and has a coefficient of sliding friction against steel, dry, of from 0.5 to 0.31.

3. The rotary pressure filter according to claim 1, wherein the plastic of the separation plates which seal off the drying zone(s) is heat resistant above 165°

C., and has a coefficient of sliding friction against steel, dry, of from 0.5 to 0.31.

4. The rotary pressure filter according to claim 1, wherein the plastic of the separation plates which seal off the other zones is heat-resistant up to 140°

C. and has a coefficient of sliding friction against steel, dry, of less than 0.4.

5. The rotary pressure filter according to claim 3, wherein the plastic of the separation plates which seal off the other zones is heat-resistant up to 140°

C. and has a coefficient of sliding friction against steel, dry, of less than 0.35.

6. The rotary pressure filter according to claim 1, wherein the separation plates which seal off the drying zone(s) comprise polyether ether ketone (PEEK).

7. The rotary pressure filter according to claim 5, wherein the separation plates which seal off the drying zone(s) comprise polyether ether ketone (PEEK).

8. The rotary pressure filter according to claim 1, wherein the separation plates which seal off the other zones comprise polyvinylidene fluoride (PVDF).

9. The rotary pressure filter according to claim 7, wherein the separation plates which seal off the other zones comprise polyvinylidene fluoride (PVDF).

10. A process for preparing methylhydroxyalkylcellulose, which comprises the separation of the methylhydroxyalkylcellulose from an aqueous suspension using a rotary pressure filter according to claim 1.

11. The process according to claim 10, wherein the methylhydroxyalkylcellulose is a methylhydroxyethylcellulose (MHEC) or a methylhydroxypropylcellulose (MHPC).

12. The process according to claim 10, wherein the methylhydroxyalkylcellulose is a methylhydroxypropylcellulose (MHPC) which has a proportion by mass of hydroxypropoxy groups of from 3.0 to 35.0% and a proportion by mass of methoxyl groups of from 15.0 to 35.0.

13. The process according to claim 10, wherein the methylhydroxyalkylcellulose is a methylhydroxypropylcellulose (MHPC) which has a proportion by mass of hydroxypropoxy groups of from 4.0 to 32.0% and a proportion by mass of methoxyl groups of from 16.5 to 30.0%.

14. The process according to claim 10, wherein the methylhydroxyalkylcellulose is a methylhydroxyethylcellulose (MHEC) which has a degree of substitution MS (HE) of from 0.10 to 1.00 and a degree of substitution DS (M) of from 1.25 to 2.20.

15. The process according to claim 10, wherein the methylhydroxyalkylcellulose is a methylhydroxyethylcellulose (MHEC) which has a degree of substitution MS (HE) of from 0.15 to 0.80, and a degree of substitution DS (M) of from 1.40 to 2.00.