Paper and materials and processes for its production

Abstract

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 stabilised wholly or mainly by 0.5 to 30 parts by weight (per part by weight size) of water soluble, anionic, polymeric stabiliser selected from water soluble synthetic-polymers, naturally occurring polymers and anionic modified naturally occurring polymers.  
     
     
         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 homogenising the size into an aqueous solution of the water soluble polymeric stabiliser and thereby forming an emulsion in which the amount of size is 0.5 to 5% and the amount of stabiliser is 0.2 to 20% and the amount of water is at least 75%, all amounts being by weight of the emulsion.  
     
     
         6 . An emulsion according to  claim 1  which is an emulsion of 0.2 to 5% of the size in water containing 0.2 to 20% (by weight of the emulsion) of a water-soluble polymeric stabiliser selected from anionic starch and water-soluble synthetic anionic polymers having molecular weight above 10,000 and which contain groups selected from hydroxylic, carboxylic, sulphuric, sulphonic and phosphoric groups, wherein the acid groups are in the form of free acid or in the form of water soluble salts.  
     
     
         7 . An emulsion according to  claim 1  having an average particle size of below 750 nm.  
     
     
         8 . An emulsion according to  claim 1  which is an emulsion of anhydride size in-water stabilised by anionic starch, wherein the amount of anionic starch is 0.5-10 parts per part by weight size, the average particle size of the emulsion is below 750 nm, preferably below 600 nm, and the emulsion is stable for at least one day.  
     
     
         9 . A process of making internally sized paper (including paper board) comprising mixing an anionic aqueous size emulsion according to  claim 1  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.  
     
     
         10 . A process according to  claim 9  in which a cationic retention aid is mixed into the cellulosic suspension, and the size emulsion and an anionic bridging agent are then mixed into the suspension, and the suspension is then drained to form a sheet and the sheet is dried.  
     
     
         11 . A process according to  claim 10  in which the anionic bridging agent is an anionic microparticulate material.  
     
     
         12 . A process according to  claim 9  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.  
     
     
         13 . A process according to  claim 12  in which the anionic size emulsion is mixed into an anionic thinstock suspension.  
     
     
         14 . A process according to  claim 12  or  claim 13  in which an anionic bridging agent is mixed into the suspension after the cationic retention aid and before the suspension is drained.  
     
     
         15 . A process of making an internally sized paper (including paper board) comprising mixing an emulsion of a size into an anionic cellulosic suspension, mixing retention aid into the suspension and thereby flocculating the suspension, draining the suspension to form a sheet and drying the sheet, characterised in that the size is provided as an anionic aqueous emulsion, the anionic emulsion is mixed into the anionic cellulosic suspension, and the retention aid is subsequently mixed into the suspension and the suspension is thereby flocculated.  
     
     
         16 . A process according to  claim 15  in which the anionic emulsion of size is stabilised by a water soluble anionic stabiliser selected from anionic starch, other oligomeric or polymeric stabilisers which have acidic groups, and other stabilisers which have both hydroxyl groups and acidic groups.  
     
     
         17 . A process according to  claim 16  in which the stabiliser is selected from anionic starch, anionic dry strength resins, synthetic copolymers having both hydroxylic groups and acidic groups, naturally occurring carbohydrate polymers and hydrolysed derivatives of naturally occurring carbohydrate polymers.  
     
     
         18 . A process according to  claims 15  to  17  in which the size is a reactive anhydride size, preferably ASA.  
     
     
         19 . A process according to  claim 15  in which the emulsion has an average particle size of below 1 μm, preferably 0.5 μm or less.  
     
     
         20 . A process according to  claim 15  in which the stabiliser is anionic starch in an amount of at least 1 part, preferably above 2 parts, per part by weight size.  
     
     
         21 . A process according to  claim 15  in which the retention aid is a cationic retention aid.  
     
     
         22 . A process according to  claim 21  in which an anionic bridging agent is mixed into the suspension after the cationic retention aid and before draining.  
     
     
         23 . A process according to  claim 22  in which the anionic bridging agent is an anionic microparticulate material.