Composition comprising cross-linked anionic, organic polymeric microparticles, its preparation and use in paper and paperboard making processes
The present invention concerns a composition being an inverse emulsion comprising cross-linked anionic, organic polymeric microparticles, said microparticles having an unswollen z-average particle size diameter of less than 0.75 μm, wherein the organic polymeric microparticles are formed from a monomer mixture comprising (a) an ethylenically unsaturated carboxylic acid, or a salt thereof; (b) an ethylenically unsaturated non-ionic monomer; and (c) from 1 to 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof. The invention also provides a process for preparing the composition, the use of the composition in a paper or paperboard making process and methods of making paper or paperboard employing said composition.
1. A composition comprising cross-linked anionic, organic polymeric microparticles, said microparticles having an unswollen z-average particle size diameter of less than 0.75 μm, wherein the organic polymeric microparticles are formed from a monomer mixture comprising
(a) an ethylenically unsaturated carboxylic acid, or a salt thereof;
(b) an ethylenically unsaturated non-ionic monomer; and
(c) from about 1 to about 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof.
2. A composition according to claim 1 , wherein the monomer mixture comprises a multi functional compound selected from the group of N,N′-methylenebisacrylamide, N,N′-methylenebismethacrylamide, polyethyleneglycol dimethacrylate, polyethyleneglycol diacrylate, N-vinylacrylamide, glycidyl acrylate, divinylbenzene, tetraallyl ammonium chloride, acrolein, aldehydes, glyoxal, diepoxy compounds, epichlorohydrin and mixtures thereof.
3. A composition according to claim 1 , wherein the ethylenically unsaturated carboxylic acid (a) is selected from the group of acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, mixtures thereof, and salts thereof.
4. A composition according to claim 1 , wherein the ethylenically unsaturated non-ionic monomer (b) is selected from acrylamide, methacrylamide or mixtures thereof.
5. A composition according to claim 1 , wherein the monomer mixture comprises,
(a) from about 40 to about 90 mole % of an ethylenically unsaturated carboxylic acid, or a salt thereof;
(b) from about 5 to about 55 mole % of an ethylenically unsaturated non-ionic monomer; and
(c) from about 1 to about 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof.
6. A composition according to claim 1 , wherein component (c) of the monomer mixture is present in an amount of from about 2 to about 8 mole %.
7. A composition according to claim 1 , wherein the monomer mixture comprises,
(a) from about 45 to about 65 mole % of acrylic acid, or salts thereof;
(b) from about 30 to about 50 mole % of acrylamide; and
(c) from about 1 to about 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof.
8. A composition according to claim 1 , wherein the unswollen number average particle size diameter is less than 0.5 μm.
9. A composition according to claim 1 , wherein component (c) of the monomer mixture is present in an amount of from about 2.5 to about 7.5 mole %.
10. A process for the preparation of a composition defined in claim 1 , said process comprising:
(A) admixing
(i) an aqueous solution of a monomer mixture comprising
(a) an ethylenically unsaturated carboxylic acid, or a salt thereof;
(b) an ethylenically unsaturated non-ionic monomer; and
(c) from about 1 to about 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof;
(ii) an oil phase comprising at least one hydrocarbon liquid;
(iii) an effective amount of surfactant or surfactant mixture, so as to form an inverse emulsion; and
(B) subjecting the inverse emulsion obtained in step (A) to polymerisation conditions.
11. A method of producing paper or paperboard wherein a cellulosic suspension is provided and drained on a screen to form a sheet which is dried,
wherein the method comprises applying a retention system to the cellulosic suspension,
wherein the retention system comprises an aqueous formulation prepared from the composition defined in claim 1 .
12. A method according to claim 11 wherein the retention system comprises (i) the aqueous formulation; and (ii) a cationic polymer.
13. A method according to claim 12 wherein the cationic polymer (ii) is added to the cellulosic suspension prior to a shear stage and the aqueous formulation (i) is added after that shear stage.
14. A method according to claim 11 wherein the retention system comprises (i) the aqueous formulation; (ii) a cationic polymer; and (iii) an inorganic microparticle.
15. A method according to claim 14 wherein the cationic polymer (ii) is added to the cellulosic suspension prior to a shear stage and the aqueous formulation (i) and the inorganic microparticle are each added after that shear stage.
16. A method according to claim 11 , wherein the monomer mixture comprises,
(a) from about 45 to about 65 mole % of acrylic acid, or salts thereof;
(b) from about 30 to about 50 mole % of acrylamide; and
(c) from about 1 to about 10 mole % of 2-acrylamido-2-methylpropanesulphonic acid, or a salt thereof.