Granted Patent B2

US 9,103,071 · App. 14/125,401 · Granted Aug 11, 2015

Abstract

Claims (41)

1. A process of making paper or paperboard, the process comprising:

introducing a dual retention system into a cellulosic thin stock,

subjecting the cellulosic thin stock to one or more shear stages, and

then draining the cellulosic thin stock on a moving screen to form a dried sheet,

wherein

the dual retention system consists of a first polymeric retention aid and a second polymeric retention aid,

the first polymeric retention aid is a water-soluble cationic polymer exhibiting an intrinsic viscosity of at least 6 dl/g,

the second polymeric retention aid is a water-soluble cationic polymer exhibiting an intrinsic viscosity of from 6 to 8 dl/g,

the second polymeric retention aid has a greater cationic charge density than the first polymeric retention aid,

the second polymeric retention aid comprises from 30 to 50 mol % of cationic monomers and from 50 to 70 mol % of non-ionic ethylenically unsaturated monomer units.

2. The process according to claim 1 , wherein:

the first polymeric retention aid and the second polymeric retention aid are either separately dosed into the cellulosic thin stock after a last point of high shear or centriscreen; or

combined into a mixture, which is then dosed into the cellulosic thin stock after the last point of high shear or centriscreen.

3. The process according to claim 2 , wherein the first and second retention aids are both cationic polyacrylamides.

4. The process according to claim 2 , wherein the first polymeric retention aid is a copolymer comprising:

from 70 to 95 mol % of acrylamide, and

from 5 to 30 mol % of methyl chloride quaternary ammonium salt of dimethyl amino ethyl acrylate.

5. The process according to claim 2 , wherein the second polymeric retention aid is a copolymer comprising:

from 20 to 80 mol % of acrylamide, and

from 20 to 80 mol % of methyl chloride quaternary ammonium salt of dimethylamino ethyl acrylate.

6. The process according to claim 2 , wherein the cellulosic thin stock comprises from 10 to 40 weight % of filler.

7. The process according to claim 1 , wherein the first and second retention aids are both cationic polyacrylamides.

8. The process according to claim 7 , wherein the first polymeric retention aid is a copolymer comprising:

from 70 to 95 mol % of acrylamide, and

from 5 to 30 mol % of methyl chloride quaternary ammonium salt of dimethyl amino ethyl acrylate.

9. The process according to claim 7 , wherein the second polymeric retention aid is a copolymer comprising:

from 20 to 80 mol % of acrylamide, and

from 20 to 80 mol % of methyl chloride quaternary ammonium salt of dimethylamino ethyl acrylate.

10. The process according to claim 7 , wherein the cellulosic thin stock comprises from 10 to 40 weight % of filler.

11. The process according to claim 1 , wherein the first polymeric retention aid is a copolymer comprising:

from 70 to 95 mol % of acrylamide, and

from 5 to 30 mol % of methyl chloride quaternary ammonium salt of dimethyl amino ethyl acrylate.

12. The process according to claim 11 , wherein the second polymeric retention aid is a copolymer comprising:

from 20 to 80 mol % of acrylamide, and

from 20 to 80 mol % of methyl chloride quaternary ammonium salt of dimethylamino ethyl acrylate.

13. The process according to claim 11 , wherein the cellulosic thin stock comprises from 10 to 40 weight % of filler.

14. The process according to claim 1 , wherein the second polymeric retention aid is a copolymer comprising:

from 20 to 80 mol % of acrylamide, and

from 20 to 80 mol % of methyl chloride quaternary ammonium salt of dimethylamino ethyl acrylate.

15. The process according to claim 14 , wherein the cellulosic thin stock comprises from 10 to 40 weight % of filler.

16. The process according to claim 1 , wherein the cellulosic thin stock comprises from 10 to 40 weight % of filler.

Assignments (12)