Paper and paperboard production process and corresponding novel retention aids, and papers and paperboards thus obtained

Abstract

The invention relates to an improved paper production process according to which a cross-linked polymer prepared in reverse-phase emulsion and sheared before introduction into the fibrous mass is used as the main retention aid, and then bentonite is used as the secondary retention aid (a dual type system). The two additions are not separated by any mandatory stage for intense shearing of the fibrous suspension (or mass). The paper manufacturer can therefore be free from the constraints of shearing the pulp. A distinctly improved retention of the fines is obtained, and also a distinct improvement in drainage. In addition, the bentonite content in the white water is reduced. Lastly, excellent formation is maintained.

1 - 34 . (canceled)  
     
     
         35 . Process for manufacturing a sheet of paper, paperboard or the like having improved retention and drainage properties, of the type which uses a dual system of an acrylic type polymer and bentonite or an optionally treated kaolin as the primary and secondary retention agents, respectively, characterized in that it incorporates operations comprised of adding to the suspension or fibrous mass to be flocculated, or paper pulp, 
 a) as the main retention agent, a (co)polyacrylamide that is cross-linked and exists in the form of a reverse phase or water-in-oil emulsion, or a solution of the powder obtained by drying said reverse phase emulsion, said emulsion or solution being sheared prior to introduction or injection into the fibrous mass; wherein said (co)polyacrylamide is 20 mole % cationic or less, and    b) then a second retention agent,    c) without a stage for intense shearing of the pulp between the additions a) and b), or with an “optional” shearing of the pulp between the additions a) and b); 
 wherein the active material concentration at the point in time when shear occurs is 3 to 15 g/l;  
 characterized in that the polymer used has an intrinsic viscosity i.v. as low as 1 to 3, which becomes an intrinsic viscosity i.v. as high as 3-7 or 8 after the application of the shearing; and characterized in that the quantity of cross-linked polyacrylamide or of cross-linked acrylic (co)polymer introduced in the form of a reverse phase water-in-oil emulsion, Areversed@ in water, or in the form of the solution of the powder obtained by drying said emulsion, is between 0.03 and 1% o, or between thirty and one thousand grams/ton (30 and 1000 g/t) of dry pulp, optionally between 0.15 and 0.5% o (or between 150 and 500 g/t).  
   
     
     
         36 . Process for manufacturing a sheet of paper, paperboard or the like having improved retention and drainage properties, of the type which uses a dual system of an acrylic type polymer and bentonite or an optionally treated kaolin, as main and secondary retention agents, respectively, according to  claim 35 , characterized in the incorporates operations comprised of adding to the suspension or fibrous mass to be flocculated, or papers pulp, 
 a) as the main retention agent, a (co) polyacrylamide that is cross-linked and exists in the form of a reverse phase or water-in-oil emulsion, or a solution of the powder obtained by drying said reverse phase emulsion, said emulsion or solution being sheared prior to introduction or injection into the fibrous mass, and    b) then a second retention agent,    c) without a stage for intense shearing of the pulp between the additions a) and b).    
     
     
         37 . Process for manufacturing a sheet of paper, paperboard or the like according to  claim 35 , characterized in that monomers chosen from among the nonionic monomers are used to prepare said (co) polymer, and/or in that at least some of the monomers used to form the polymer are ionic and/or in that the monomers are monomers with monoethylenic unsaturation, or allylic monomers or vinyl monomers, especially acrylic or methacrylic monomers, and/or in that the cross-linked acrylic (co) polymer prepared in reverse phase emulsion is a cationic copolymer of acrylamide and of an unsaturated cationic ethylenic monomer, chosen from the group comprising dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl methacrylate (MADAME), quaternized or salified by different acids and quaterinizing agents, benzyl chloride, methyl chloride, alkyl or aryl chloride, dimethyl sulfate, diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and meth acrylamidopropyltrimethylammonium chloride (MAPTAC), and/or the cross-linked acrylic (co) polymer prepared in reverse phase emulsion is a copolymer of acrylamide and of ethyl acrylate trimethyl ammonium chloride, and/or in that the cross-linked acrylic (co) polymer prepared in reverse phase emulsion is cross-linked acrylic (co) polymer prepared in reverse phase emulsion is cross-linked by a cross-linking agent constituted by a polyfunctional compound having at least two reagent groups chosen from the group comprising the double bonds, the aldehyde bonds or the epoxy bonds, the cross-linking agents that can be incorporated comprising ionic cross-linking agents such as polyvalent metal salts, formaldehyde, glyoxal, or covalent cross-linking agents that will copolymerize with the monomers, preferably monomers with diethylenic unsaturation optionally the family of diacrylate esters and optionally the diacrylates of polyethylene glycol PEG or polyethylenic unsaturation, and optionally methylenebisacrylamide (MBA).  
     
     
         38 . Process according to  claim 35  characterized in that the cross-linked acrylic (co)polymer in reverse phase emulsion or in a solution of the powder obtained by drying the synthetic reverse phase emulsion is introduced into the paper pulp at a concentration of 0.03 to one per mill (0.03 to 1% o) by weight of the dry weight of the fibrous suspension of paper pulp, optionally 0.15 to 0.5 per mill (0.15 to 0.5% o).  
     
     
         39 . Process according to  claim 35  characterized in that the MBA is introduced at a concentration of 5 to 200 moles per million moles of monomers.  
     
     
         40 . Process according to  claim 35  characterized in that the bentonite is a semisodic bentonite, used at a rate of 0.1 to 0.5 percent (0.1 to 0.5%) of the dry weight of the fibrous suspension.  
     
     
         41 . Process according to  claim 35 , characterized in that the pulp used, which contains the filler, is diluted, then the polymer is added as the main retention agent, after which bentonite is added as the secondary retention agent.  
     
     
         42 . Process according to  claim 35 , characterized in that the sheared cross-linked polymer in reverse phase emulsion form, “reversed” in water, or in the form of the sheared solution of the powder obtained by drying of said emulsion, is injected or introduced into the diluted paper pulp or fibrous mass to be flocculated or “thin stock,” optionally a pulp diluted to about 1.5% solid matter optionally including cellulose fibers, fillers, and various paper and paperboard additives, and the second retention agent, or secondary retention agent, such as bentonite or an optionally pretreated kaolin, is then added between 5 and 30 s after the introduction of the polymer.  
     
     
         43 . Process for manufacturing a sheet of paper, paperboard or the like according to  claim 35 , characterized in that the shearing of the reverse phase emulsion of the polymer or of the solution obtained by the redissolution in water of the powder obtained by drying the synthetic reverse phase emulsion, is carried out before injection into the pulp, with a concentration of 3-5 to 10-15 g of active material optionally the polymer/liter of emulsion of the polymer, optionally between 5 and 10 g/l, in an “Ultra Turrax”™ machine, optionally at 10,000 rpm or in a household mixer of the “Moulinex”™ type, substantially at the same magnitude of rotation speed, for a duration that can last between 15-30 seconds and 2-5 minutes, or in that the shearing is carried out in high pressure recirculation pumps or turbines.  
     
     
         44 . Process for manufacturing a sheet of paper, paperboard or the like according to  claim 35 , characterized in that the shearing the reverse phase emulsion “reversed” in water, or the solution of the dried powder of the synthetic emulsion, before injection into the pulp results in an ion regain IR of 40 to 50%, which can reach at least 60 or 70% and even more, up to values greater or far greater than 100%, with:  
         Ion regain  IR= ( X−Y )/ Y× 100  with X: ionicity after shearing in meg/g.    Y: ionicity before shearing in meg/g.    
     
     
         45 . Novel retention agent for the manufacture of a sheet of paper, paperboard or the like, characterized in that it comprises a sheared cross-linked polyacrylamide or a cross-linked acrylic (co)polymer in reverse phase or water-in-oil emulsion, or in the form of the sheared solution of the powder obtained by drying said emulsion, and optionally characterized in that the cross-linking agent is a cross-linking agent constituted by a polyfunctional compound having at least two reagent groups chosen from the group comprising the double bonds, the aldehyde bonds or the epoxy bonds, the cross-linking agents that can be incorporated comprising ionic cross-linking agents such as polyvalent metal salts, formaldehyde, glyoxal, or covalent cross-linking agents that will copolymerize with the monomers, optionally monomers with diethylenic unsaturation the family of diacrylate esters which can include the diacrylates of polyethylene glycol (PEG) or polyethylenic unsaturation, and optionally methylenebisacrylamide (MBA), and in that the cross-linking agent is introduced at a rate of five to two hundred (5 to 200) moles per million moles of monomers characterized in that the polymer used has an intrinsic viscosity i.v. as low as 1 to 3, which becomes an intrinsic viscosity i.v. as high as 3-7 or 8 after the application of the shearing; and characterized in that the quantity of cross-linked polyacrylamide or of cross-linked acrylic (co)polymer introduced in the form of a reverse phase water-in-oil emulsion, “reversed” in water, or in the form of the solution of the powder obtained by drying said emulsion, is between 0.03 and 1% o, or between thirty and one thousand grams/ton (30 and 1000 g/t) of dry pulp, optionally between 0.15 and 0.5% o (or between 150 and 500 g/t).  
     
     
         46 . Novel retention agent for the manufacture of a sheet of paper, paperboard or the like according to  claim 45 , characterized in that the cross-linked polyacrylamide is a cationic copolymer of acrylamide and of an unsaturated cationic ethylenic monomer, chosen from the group comprising dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl methacrylate (MADAME), quaterinized or alified by different acids and quaterinizing agents, benzyl chloride, methyl chloride, alkyl or aryl chloride, dimethyl sulfate, diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and meth acrylamidopropyltrimethylammonium chloride (MAPTAC).  
     
     
         47 . Retention agent according to  claim 45 , characterized in that it is sheared at a concentration on the order of 1-5 to 10-15 g of active material, optionally the polymer/liter of emulsion of the polymer, optionally between 5 and 10 g/l, in an “Ultra Turrax”™ machine optionally, at 10,000 rpm, or in a household mixer of the “Moulinex”™ type, substantially at the same magnitude of rotation speed, for a duration that can last between 15-30 seconds and 2-5 minutes, or in high-pressure recirculation pumps or turbines.  
     
     
         48 . Retention agent according to  claim 45 , characterized in that it uses a polymer having an intrinsic viscosity i.v. as low as 1 to 3, which becomes an intrinsic viscosity as high as 3-7 or 8 after the application of the shearing, or in that an ion regain IR of 40 to 50% in obtained, which can reach at least 60 or 70% or even more, up to values greater or far greater than 100%, with:  
         Ion regain  IR= ( X−Y )/ Y× 100  with X: ionicity after shearing in meg/g.    Y: ionicity before shearing in meg/g.    
     
     
         49 . A sheet of paper or paperboard prepared in a process utilizing a retention agent according to  claim 45 .  
     
     
         50 . Sheet of paper, paperboard or the like, characterized in that it is obtained with the use of a process according to  claim 35 .  
     
     
         51 . The process of  claim 35  wherein the active material concentration at the point in time when shear occurs in 5 to 10 g/l.  
     
     
         52 . The process according to  claim 35  characterized in that the cross-linked acrylic (co)polymer in reverse phase emulsion or in a solution of the powder obtained by drying the synthetic reverse phase emulsion is introduced into the paper pulp at a concentration of 0.15 to 0.5 per mill (0.15 to 0.5% o) by weight of the dry weight of the fibrous suspension of paper pulp, optionally 0.15 to 0.5 per mill (0.15 to 0.5% o), or between 30 and 1000 g/t preferably 150 and 500 g/t.  
     
     
         53 . The process according to  claim 35  characterized in that the cross-linked acrylic (co)polymer in reverse phase emulsion or in a solution of the powder obtained by drying the synthetic reverse phase emulsion is introduced into the paper pulp at a concentration of 0.15 to 0.5 per mill (0.15 to 0.5% o) by weight of the dry weight of the fibrous suspension of paper pulp.  
     
     
         54 . The process according to  claim 39  characterized in that the MBA is introduced at a concentration of 5 to 50 moles per million moles of monomers.  
     
     
         55 . The process according to  claim 54  characterized in that the MBA is introduced at a concentration of 10 to 20 moles per million moles of monomers.  
     
     
         56 . The process according to  claim 42  characterized in that the second retention agent, or secondary retention agent or optionally pretreated kaolin, is added between 10-20 s after the introduction of the polymer.  
     
     
         57 . The process according to  claim 42  characterized in that the second retention agent, or secondary retention agent or optionally pretreated kaolin, is added up to about 5 minutes after the introduction of the polymer.  
     
     
         58 . The novel retention agent of  claim 45  characterized in that the cross-linking agent is introduced at a rate of 5 to 50 moles per million moles of monomers.  
     
     
         59 . The novel retention agent of  claim 58  characterized in that the cross-linking agent is introduced at a rate of 10 to 20 moles per million moles of monomers.  
     
     
         60 . The novel retention agent of  claim 59  characterized in that the cross-linking agent is introduced at a rate of 20 moles per million moles of monomers.