Method for making carboxyalkyl cellulose

1. A method for making a carboxyalkyl cellulose product, comprising treating an unbleached or lightly bleached kraft pulp containing lignin and cellulose and having a kappa value of from 7.7 to 65 with a carboxyalkylating agent to provide carboxyalkyl cellulose and lignin or carboxyalkyl lignin.

2. The method of claim 1 , wherein the kraft pulp is a never-dried kraft pulp.

3. The method of claim 1 , wherein the carboxyalkylating agent is chloroacetic acid, a chloroacetic acid salt, 3-chloropropionic acid, or a 3-chloropropionic acid salt.

4. The method of claim 1 , wherein the carboxyalkyl cellulose has a degree of carboxy substitution from about 0.4 to about 1.4.

5. The method of claim 1 , wherein the kraft pulp has a lignin content of from 1 to 8.45 percent by weight of the cellulose.

6. The method of claim 1 , wherein the kraft pulp has a hemicellulose content of from 0.1 to 17 percent by weight of the cellulose.

7. The method of claim 1 further comprising crosslinking the carboxyalkyl cellulose to provide a crosslinked carboxyalkyl cellulose.

8. A method for making a carboxyalkyl cellulose product, comprising:

(a) alkalizing an unbleached or lightly bleached kraft pulp containing lignin and cellulose and having a kappa value of from 7.7 to 65 to provide an alkalized kraft pulp; and

(b) etherifying the alkalized kraft pulp with a carboxyalkylating agent to provide carboxyalkyl cellulose and lignin or carboxyalkyl lignin.

9. The method of claim 8 , wherein the kraft pulp is a never-dried kraft pulp.

10. The method of claim 8 , wherein the carboxyalkylating agent is chloroacetic acid, a chloroacetic acid salt, 3-chloropropionic acid, or a 3-chloropropionic acid salt.

11. The method of claim 8 , wherein the carboxyalkyl cellulose is carboxymethyl cellulose or carboxyethyl cellulose.

12. The method of claim 8 , wherein the carboxyalkyl cellulose has a degree of carboxy substitution from about 0.4 to about 1.4.

13. The method of claim 8 , wherein the kraft pulp has a lignin content of from 1 to 8.45 percent by weight of the cellulose.

14. The method of claim 8 , wherein the pulp has a hemicellulose content of from 0.1 to 17 percent by weight of the cellulose.

15. The method of claim 8 further comprising crosslinking the carboxyalkyl cellulose to provide a crosslinked carboxyalkyl cellulose.

16. A method for making a carboxyalkyl cellulose product, comprising:

(a) crosslinking an unbleached or lightly bleached kraft pulp containing lignin and cellulose and having a kappa value of from 7.7 to 65 to provide a crosslinked kraft pulp;

(b) alkalizing the crosslinked kraft pulp to provide an alkalized kraft pulp; and

(c) etherifying the alkalized kraft pulp with a carboxyalkylating agent to provide carboxyalkyl cellulose and lignin or carboxyalkyl lignin.

17. The method of claim 16 , wherein the kraft pulp is a never-dried kraft pulp.

18. The method of claim 16 , wherein the carboxyalkylating agent is chloroacetic acid, a chloroacetic acid salt, 3-chloropropionic acid, or a 3-chloropropionic acid salt.

19. The method of claim 16 , wherein the carboxyalkyl cellulose is carboxymethyl cellulose or carboxyethyl cellulose.

20. The method of claim 16 , wherein the carboxyalkyl cellulose has a degree of carboxy substitution from about 0.4 to about 1.4.