Granted Patent B2

US 9,187,572 · App. 13/822,118 · Granted Nov 17, 2015

Abstract

Claims (29)

1. A process for treating a cellulose ether with 0.1 to 4% by weight, based on dry cellulose ether, of a dialdehyde in the presence of from 10 to 40 weight percent of water, based on the total weight of cellulose ether and water, in a mixing device characterized by a FROUDE number FR w of at least 200, wherein

Fr

w

=

ω

w

2

⁢

R

w

g

,

wherein ω w is the angular frequency in sec −1 and is defined as 2*π*RPM/60,

RPM is the rotational speed of the mixing device in revolutions per minute,

R w is the radius of the mixing device in m, and

g is the acceleration due to gravity in m/s 2 .

2. The process of claim 1 wherein the cellulose ether is treated with the dialdehyde in the presence of from 15 to 40 weight percent of water.

3. The process of claim 1 wherein the cellulose ether is a methyl cellulose or a hydroxy-C 1-3 -alkyl methyl cellulose.

4. The process of claim 3 wherein the process is conducted in the presence of from 10 to 30 weight percent of water.

5. The process of claim 1 wherein the cellulose ether is a carboxymethyl cellulose, carboxymethyl hydroxyethyl cellulose, hydroxyethyl cellulose or ethyl hydroxyethyl cellulose.

6. The process of claim 5 wherein the process is conducted in the presence of from 20 to 40 weight percent of water.

7. The process of claim 1 wherein the mixing device is a mixer with a mixing shaft.

8. The process of claim 1 wherein the mixing device is a continuous high speed horizontal paddle mixer.

9. The process of claim 1 wherein the dialdehyde is glyoxal.

10. The process of claim 1 wherein the treatment is conducted in the presence of an acid.

11. The process of claim 1 wherein the treatment is conducted in the presence of an aqueous salt solution comprising at least two salts, one of the salts being a weak acid having a pK a of from 5.5 to 8.5, and the other salt being the salt of the weak acid having a pK a of from 5.5 to 8.5.

12. The process of claim 1 wherein the cellulose ether is milled and dried simultaneously after the treatment with a dialdehyde.

13. A method of reducing lumps in a process for dispersing and dissolving water-soluble cellulose ethers in water, wherein the cellulose ether is treated with a dialdehyde according to the process of claim 1 and the treated cellulose ether is dispersed in water.

14. The process of claim 1 wherein the mixing device has a FROUDE number FR w of at least 500.

Assignments (10)