Core/shell polymer particles as surface sizing agents

Patent metadata

Field	Value
Publication number	US-10640926-B2
Application number	US-201615756900-A
Country	US
Kind code	B2
Filing date	Sep 2, 2016
Priority date	Sep 4, 2015
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

The present invention provides a core/shell polymer particle for surface sizing of cellulosic products, wherein the core polymer and the shell polymer of the core/shell polymer particle are polymerized from monomers comprising at least 40%, by weight of monomers selected from branched C3-10-alkyl (meth)acrylate, styrene, linear C1-10-alkyl (meth)acrylate, and acrylonitrile, based on the total weight of the monomers of the core/shell polymer particle; provided that the polymer of the core/shell polymer particle comprises at least 40% by weight of branched C3-6-alkyl (meth)acrylate and at least 50% by combined weight of branched C3-10-alkyl (meth)acrylate and styrene, linear C1-10-alkyl (meth)acrylate, and/or acrylonitrile, based on the total weight of the monomers of the core/shell polymer particle.

First claim

The invention claimed is:

1. A core/shell polymer particle for surface sizing of cellulosic products,
wherein the core polymer and the shell polymer of the core/shell polymer particle are polymerized from monomers comprising one or more selected from tert-butyl acrylate, n-butyl acrylate, and acrylonitrile;
provided that the polymer of the core/shell polymer particle comprises at least 40% by weight of tert-butyl acrylate and at least 50% by combined weight of at least one of tert-butyl acrylate, n-butyl acrylate, and acrylonitrile, based on the total weight of the monomers of the core/shell polymer particle;
wherein the core/shell polymer comprises:
(a) a core polymer polymerized from monomers comprising at least 25% by weight, of monomers selected from tert-butyl acrylate, n-butyl acrylate, and acrylonitrile; and
(b) a shell polymer polymerized from monomers comprising at least 25% by weight, of tert-butyl acrylate, based on total weight of the monomers of the core/shell polymer particle, and wherein the shell polymer encapsulates the core polymer; and
wherein 10 to 60 wt % of the core/shell polymer particle is degraded starch with a molecular weight M n of 500 to 10,000.

2. The core/shell polymer particle as claimed in claim 1 , wherein the core/shell polymer comprises at least 50% by weight branched C 3-10 -alkyl (meth)acrylate and at least 75% by total weight, of branched C 3-6 -alkyl acrylate and acrylonitrile, based on the total weight of the monomers of the core/shell polymer particle.

3. The core/shell polymer particle as claimed claim 1 , wherein the core/shell polymer comprises at least 60% by weight, of branched C 3-10 -alkyl (meth)acrylate based on the total weight of the monomers of the core/shell polymer particle.

4. The core/shell polymer particle as claimed in claim 1 , wherein the shell polymer comprises at least 50% by weight of branched C 3-10 -alkyl (meth)acrylate, based on the total weight of the shell polymer monomers.

5. The core/shell polymer particle as claimed in claim 1 , wherein the core polymer comprises 50 to 100% by weight of monomers selected from branched C 3-10 -alkyl (meth)acrylate, styrene, linear C 1-10 -alkyl (meth)acrylate, and acrylonitrile, and any mixtures thereof, based on the total weight of the core polymer monomers.

6. The core/shell polymer particle as claimed in claim 5 , wherein the branched C 3-10 -alkyl (meth)acrylate is tert-butyl acrylate.

7. The core/shell polymer particle as claimed in claim 5 , wherein the linear C 1-10 -alkyl (meth)acrylate is n-butyl acrylate.

8. The core/shell polymer particle as claimed in claim 1 , wherein the ratio of the weight of the core polymer monomers to the weight of the shell polymer monomers is preferably from 75:25 to 25:75.

9. The core/shell polymer particle as claimed in claim 1 , wherein the shell polymer has a glass transition temperature from 35 to 75° C.

10. The core/shell polymer particle as claimed in claim 1 , wherein the core polymer has a glass transition temperature below 75° C.

11. The core/shell polymer as claimed in claim 1 , wherein the particle size distribution D50 of the core/shell polymer particle is below 110 nm.

12. The core/shell polymer as claimed in claim 1 , wherein the core polymer and the shell polymer of the core/shell polymer particle are polymerized from monomers in presence of degraded starch or water-soluble natural or synthetic polymer.

13. A surface sizing composition comprising core-shell polymer as defined in claim 1 .

14. The surface sizing composition as claimed in claim 13 , wherein the starch is anionic starch.

15. A method of surface sizing a cellulosic product, comprising applying to at least one surface of the cellulosic product a sizing composition comprising core-shell polymer particles as defined in claim 14 .

16. A surface-sized cellulosic product comprising the surface sizing composition as defined in claim 13 .

17. A method of surface sizing a cellulosic product, comprising applying to at least one surface of the cellulosic product a surface sizing composition as defined in claim 13 .

18. The method as claimed in claim 17 , wherein the cellulosic product is paper.

19. A surface-sized cellulosic product comprising the core-shell polymer particles as defined in claim 1 .

20. A method of surface sizing a cellulosic product, comprising applying to at least one surface of the cellulosic product a core-shell polymer as defined in claim 1 .

21. The core/shell polymer particle as claimed in claim 1 , wherein at least 80 wt % of the monomers are one or more monomers selected from the group consisting of tert-butyl (meth)acrylate, n-butyl (meth)acrylate, styrene and acrylonitrile.

Assignees

• Kemira Oyj

Inventors

• Lepo Anneli
• Turunen Elsi
• Turkki Tarja
• Überbacher Bernhard

Classifications

• D21H23/22 Primary

  Addition to the formed paper · CPC title

• D21H19/22

  Polyalkenes, e.g. polystyrene · CPC title

• D21H21/54

  being spherical, e.g. microcapsules, beads · CPC title

• D21H21/16

  Sizing or water-repelling agents · CPC title

• C08F212/08 Primary

  Styrene · CPC title