Method for optically brightening paper

• US 20020084049A1
• Filed: 09/10/2001
• Published: 07/04/2002
• Est. Priority Date: 09/16/1997
• Status: Active Grant

• Current Assignee: Peter Rohringer, Thomas Engelhardt
• Original Assignee: Peter Rohringer, Thomas Engelhardt
• Inventors: Engelhardt, Thomas, Rohringer, Peter
• Granted Patent: US 6,464,832 B2
• Time in Patent Office: Days
• US Class Current: 162/158
• CPC Class Codes: D21H 17/68 siliceous, e.g. clays
• CPC Class Codes: D21H 21/30 Luminescent or fluorescent substances, e.g. for optical bleaching D21H21/40 takes precedence

Abstract

A simplified method for the optical brightening of paper either in the pulp mass, the size or metering press or by coating by the use of a formulation of an optical brightening agent together with a swellable layered silicate.

Claims

1. A method for the optical brightening of paper, which comprises the use of a formulation essentially consisting of a swellable layered silicate and an optical brightener.

2. A method according to claim 1, wherein the formulation is in the form of a dry mixture or an aqueous dispersion.

3. A method according to claim 2, wherein the dry mixture contains 0.1 to 90% by weight of the optical brightener, based on the weight of the swellable layered silicate.

4. A method according to claims 2, wherein the aqueous dispersion contains 0.1 to 15% by weight of optical brightener, based on the amount of the swellable layered silicate.

5. A method according to claim 4, wherein the aqueous dispersion contains 1 to 10% by weight of optical brightener, based on the amount of the swellable layered silicate.

6. A method according to any of claims 2, 4 and 5, wherein the aqueous dispersion contains 2 to 60% by weight of the swellable layered silicate.

7. A method according to claim 6, wherein the aqueous dispersion contains 2 to 60%, preferably 2 to 25% by weight, of synthetic bentonite.

8. A method according to claim 6, wherein the aqueous dispersion contains 2 to 60%, preferably 2 to 50% by weight, of synthetic zeolite.

9. A method according to claim 1, wherein the optical brightener is a derivative of 4,4′

-bis-(triazinylamino)-stilbene-2,2′

-disulphonic acid, or a derivative of 4,4′

-distyryl-biphenyl.

10. A method according to claim 1, wherein the optical brightener is a derivative of a dibenzofuranylbiphenyl.

11. A method according to claim 9, wherein the 4,4′

-bis-(triazinylamino)-stilbene-2,2′

-disulphonic acid optical brightener is of the formula;

12. A method according to claim 9, wherein the 4,4′

distyryl-biphenyl optical brightener is of the formula;

13. A method according to claim 9, wherein the optical brightener is of the formula:

14. A method according to claim 10, wherein the optical brightener is of the formula

15. A method according to claim 1, in which the formulation is added to the pulp mass.

16. A method according to claim 1, in which the formulation is used for paper coating.

18. A method according to claim 1, in which the formulation is added to the size press or metering press.

19. Paper which has been optically brightened by the method according to claim 1.