Paper and materials and processes for its production
Paper is made by providing an anionic aqueous emulsion of a size, usually a reactive anhydride size, and mixing it into a cellulosic suspension prior to drainage of the suspension to form a sheet which is then dried to provide paper (including paper board). The emulsion is preferably stabilised wholly or mainly by 0.5 to 30 parts by weight (per part by weight size) of water soluble, anionic, polymeric stabiliser, which is preferably anionic starch. Alternatively, the emulsion may be added to the cellulosic suspension while it is anionic, before mixing retention into it. The emulsion may be added to the cellulosic suspension after cationic retention aid has been added to it, the emulsion being added with, before or after mixing anionic microparticulate material or other anionic bridging aid, prior to drainage of the suspension.
1. An anionic aqueous emulsion of size stabilized wholly or mainly by 1.5 to 30 parts by weight (per part by weight size) of water soluble, anionic, polymeric stabilizer which is anionic starch and wherein the average particle size of the emulsion is below 750 nm.
2. An emulsion according to claim 1 in which the size is a reactive size.
3. An emulsion according to claim 2 in which the size is an anhydride size.
4. An emulsion according to claim 3 in which the anhydride size is the only size in the emulsion.
5. An emulsion according to any preceding claim obtainable by homogenizing the size into an aqueous solution of the water soluble polymeric stabilizer and thereby forming an emulsion in which the amount of size is 0.2 to 5% by weight of the emulsion.
6. An emulsion according to claim 1 , 2 , 3 or 4 which is an emulsion of 0.2 to 5% of the size in water containing 0.5 to 20% (by weight of the emulsion) of anionic starch.
7. An emulsion according to claim 1 , 2 , 3 or 4 having an average particle size of below 600 nm.
8. A process of making internally sized paper (including paper board) comprising mixing an anionic aqueous size emulsion according to any of claims 1 to 4 into a cellulosic suspension, mixing a retention aid into the suspension before, with or after mixing the size emulsion into the suspension, draining the suspension to form a sheet, and drying the sheet.
9. A process of making internally sized (including paper board) comprising a cationic retention aid into a cellulosic suspension, and then mixing the size emulsion of claim 1 , 2 , 3 or 4 and an anionic bridging agent into the suspension, and the suspension is then drained to form a sheet and the sheet is dried.
10. A process according to claim 9 in which the anionic bridging agent is an anionic microparticulate material.
11. A process according to claim 8 in which the anionic size emulsion is mixed into the cellulosic suspension while the cellulosic suspension is anionic, and the retention aid is subsequently mixed into the suspension and the suspension is thereby flocculated, and the flocculated suspension is drained to form a sheet and the sheet is dried.
12. A process according to claim 11 in which the anionic size emulsion is mixed into an anionic thinstock suspension.
13. A process according to claim 12 in which an anionic bridging agent is mixed into the suspension after the cationic retention aid and before the suspension is drained.
14. An emulsion according to claim 2 obtainable by homogenizing the size into an aqueous solution of the water soluble polymeric stabilizer and thereby forming an emulsion in which the amount of size is 0.25 to 5% by weight of the emulsion.
15. An emulsion according to claim 5 which is an emulsion of 0.2 to 5% of the size in water containing 0.5 to 30% (by weight of the emulsion) of anionic starch.
16. An emulsion according to claim 5 having an average particle size of below 600 nm.
17. An emulsion according to claim 6 having an average particle size of below 600 nm.
18. A process of making internally sized paper (including paper board) comprising mixing an anionic aqueous size emulsion according to claim 5 into a cellulosic suspension, mixing retention aid into the suspension before, with or after mixing the size emulsion into the suspension, draining the suspension to form a sheet, and drying the sheet.
19. A process of making internally sized paper (including paper board) comprising mixing an anionic aqueous size emulsion according to claim 6 into a cellulosic suspension, mixing retention aid into the suspension before, with or after mixing the size emulsion into the suspension, draining the suspension to form a sheet, and drying the sheet.
20. A process of making internally sized paper (including paper board) comprising mixing an anionic aqueous size emulsion according to claim 7 into a cellulosic suspension, mixing retention aid into the suspension before, with or after mixing the size emulsion into the suspension, draining the suspension to form a sheet, and drying the sheet.