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

Abstract

The invention concerns an improved method for making paper, which uses a branched polymer prepared in invert emulsion as the main retention agent, and bentonite as a secondary retention agent (dual type system). The two additions are separated by a step for shearing the fibrous suspension (or mass). The invention results in highly improved retention and also highly improved dewatering. Moreover, it enables the bentonite content in white water to be reduced.

1 - 23 . (canceled)  
   
   
       24 . Process for manufacturing a sheet of paper or paperboard having improved retention and drainage properties, of the type comprising utilizing a dual system of (a) an acrylic polymer as a primary retention agent and (b) either bentonite or a treated kaolin as a secondary retention agent, the introductions of which are separated by a stage for shearing the suspension or fibrous mass or paper pulp, characterized in that said polymer is a branched, cationic, acrylic (co)polymer prepared in the form of a reverse phase water-in-oil emulsion, used either in emulsion reversed in water, or in a solution of the powder obtained by drying the emulsion; wherein the dual system has a UL viscosity that is greater than 3.  
   
   
       25 . Process according to  claim 24 , characterized in that the branched acrylic (co) polymer prepared in reverse phase emulsion is introduced into the paper pulp at a concentration of 0.03 to 1% by weight, or 30 to 1,000 g/t, of the dry weight of the fibrous suspension of paper pulp, optionally 0.15 to 0.5 percent, or 150 to 500 g/t.  
   
   
       26 . Process according to  claim 24 , characterized in that the branched acrylic (co)polymer prepared in reverse phase emulsion is a cationic copolymer of acrylamide and of an unsaturated cationic ethylenic monomer chose from the group comprising dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl methacrylate (MADAME), quaternized or salified by benzyl chloride, methyl chloride, alkyl or aryl chlorides, dimethyl sulfate, diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and methacrylamidopropyltrimethylammonium chloride (MAPTAC).  
   
   
       27 . Process according to  claim 24 , characterized in that the branched acrylic (co)polymer in reverse phase emulsion is branched by means of a branching agent constituted by a polyfunctional compound having at least two reagent groups chosen from the group comprising double bonds, aldehyde bonds or epoxy bonds.  
   
   
       28 . Process according to  claim 24 , characterized in that the branched acrylic (co)polymer in reverse phase emulsion is branched by means of a branching agent constituted by methylenebisacrylamide (MBA) at a concentration of 5 to 200 moles per million moles of monomers.  
   
   
       29 . Process according to  claim 24 , characterized in that the bentonite is a semisodic bentonite, used at a rate of 0.1 to 0.5 percent of the dry weight of the fibrous suspension.  
   
   
       30 . Process according to  claim 28 , characterized in that the pulp used, which contains filler, is diluted, after which the polymer is added as the main retention agent, then the bentonite is added as the secondary retention agent, or the bentonite is replaced by kaolin, optionally pretreated with an electrolyte, as the secondary retention agent.  
   
   
       31 . Process according to  claim 30 , characterized in that the quantity of branched polyacrylamide optionally of branched acrylic (co)polymer, introduced either in reverse phase water-in-oil emulsion reversed in water, or in a solution of the powder obtained by drying the emulsion, is between 0.03 and 1%, or between 30 and 1,000 grams per ton of dry pulp.  
   
   
       32 . Process according to  claim 30 , characterized in that a quantity of branched polyacrylamide or of branched acrylic (co)polymer, introduced either in reverse phase water-in-oil emulsion reversed in water, or in a solution of the powder obtained by drying the emulsion, is between 0.15 and 0.5% or between 150 and 500 g/t.  
   
   
       33 . Process according to  claim 24 , characterized in that the branched polymer prepared in reverse phase emulsion is injected or introduced, either in emulsion reversed in water, or in a solution of the powder obtained by drying the emulsion, before a shearing stage, into the paper pulp or fibrous mass to be flocculated, which is diluted into diluted paper pulp or thin stock that is a pulp diluted to about 0.7-1.5% solid matter that can be cellulose fibers, fillers, and/or other.  
   
   
       34 . Process according to  claim 24 , characterized in that some of the branched polymer in emulsion is introduced at the level of the stage for preparing the thick stock with about 5% or more solid matter, or at the level of the preparation of the thick stock before a shearing stage.  
   
   
       35 . Novel retention agent for the manufacture of a sheet of paper or paperboard characterized in that it comprises a) a branched polyacrylamide or optionally a branched acrylic (co)polymer which is a cationic copolymer of acrylamide and an unsaturated cationic ethylenic monomer, chosen from the group comprising dimethylaminoethyl acrylate (ADAME), dimethylaminoethyl methacrylate (MADAME), quaternized or salified by different acids and quaternizing agents, benzyl chloride, methyl chloride, alkyl or aryl chlorides, dimethyl sulfate, diallyldimethylammonium chloride (DADMAC), acrylamidopropyltrimethylammonium chloride (APTAC), and methacrylamidopropyltrimethylammonium chloride (MAPTAC) in reverse phase emulsion, either in reverse phase emulsion dissolved or reversed in water, or in a solution of the powder obtained by drying or spray-drying the reverse phase emulsion; in combination with either bentonite or treated kaolin, and in combination with a branching agent.  
   
   
       36 . Novel retention agent for the manufacture of a sheet of paper or paperboard according to 35, characterized in that its UL viscosity is greater than 3.  
   
   
       37 . Sheet of paper or paperboard obtained utilizing a retention agent according to  claim 35 .  
   
   
       38 . Sheet of paper or paperboard produced by a process according to  claim 24 .  
   
   
       39 . A process for manufacturing a sheet of paper or paperboard having improved retention and drainage properties, comprising: 
 introducing an acrylic polymer as a primary retention agent to a suspension or fibrous mass or paper pulp wherein said acrylic polymer is a branched, cationic, acrylic(co)polymer in the form of a reverse phase water-in-oil emulsion used either in emulsion reversed in water, or in a solution of powder obtained by drying the emulsion,    shearing the suspension or fibrous mass paper pulp, and    introducing bentonite or a treated kaolin as a secondary retention agent.    
   
   
       40 . The method of  claim 26  wherein said unsaturated cationic ethylenic monomer is dimethylaminoethyl acrylate (ADAME).  
   
   
       41 . The method of  claim 26  wherein said unsaturated cationic ethylenic monomer is dimethylaminoethyl methacrylate (MADAME).  
   
   
       42 . Process according to  claim 24 , wherein the dual system has a UL viscosity that is greater than 3.5.  
   
   
       43 . Process according to  claim 24 , wherein the dual system has a UL viscosity that is greater than 4.  
   
   
       44 . Process according to  claim 30 , wherein, before the bentonite is added, a shearing stage is carried out in the mixing pump or fan pump.  
   
   
       45 . Process according to  claim 30 , wherein the bentonite is replaced by kaolin that is pretreated with an electrolyte.  
   
   
       46 . Novel retention agent according to  claim 36  wherein its UL viscosity is greater than 3.5.  
   
   
       47 . Novel retention agent according to  claim 36  wherein its UL viscosity is greater than 4.