CA2235637A1 - Improved papermaking process - Google Patents

Abstract

The claimed invention comprises a papermaking process comprising forming an aqueous cellulosic papermaking slurry, subjecting the slurry to one or more shear stages.
adding to the slurry a mineral filler prior to at least one of the shear stages, adding to the slurry after the addition of the mineral filler and prior to at least one of the shear stages an effective amount of a dispersion polymer selected from the group consisting of copolymers of acrylamide and dimethylaminoethylacrylate methyl chloride quaternary salt (DMAEA.MCQ), dimethylaminoethylmethacrylate methyl chloride quaternary salt (DMAEM.MCQ), dimethylaminoethylacrylate benzyl chloride quaternary salt (DMAEA.BCQ) and dimethylaminoethylmethacrylate benzyl chloride quaternary salt (DMAEM.BCQ) and diallyldimethylammonium chloride (DADMAC), shearing the slurry adding a microparticle selected from the group consisting of organics such as copolymers of polyacrylic acid, inorganics such as bentonite and silica sol, draining the slurry to form a sheet, and drying the sheet to form a paper sheet.

Description

CA 0223~637 1998-07-23 Barl~round of the lnv~nt:ion 1. Field of the Invention The present invention is in the technical field of papenn~king and more particularly in the technical field of wet-end additives to pap~ king furnish.

2. Description of the Prior Art In the manufacture of paper an aqueous cellulosic suspension or slurry is formed into a paper sheet. The cellulosic slurry is generally diluted to a consistency (percent dry weight of solids in the slurry) of less than 1 percent and often below 0.5 percent ahead of 10 the paper machine. while the finished sheet must have less then 6 weight percent water.
Hence the dewatering aspects of papermaking are extremely important to the efficiency and cost of the manufacture.
The dewatering method of the least cost in the process is drainage, and thereafter more expensive methods are used. for instance vacuum, pressing, evaporation and the 1~ like. and in practice a combination of such methods are employed to dewater or dry the sheet to the desired water content. Since drainage is both the first dewatering method employed and the least expensive. improvement in the efficiency of drainage will decrease the amount of v~ater required to be removed by other methods and hence improve the overall efficiency of dewatering and reduce the cost thereof.
~0 Another aspect of papermaking that is extremely important to the efficiency and cost of the manufacture is retention of furnish components on and within the fiber mat being formed during papermal;ing. A papermaking furnish contains generally particles - CA 0223~637 1998-07-23 ~ that range in size from about the 2 to 3 millimeter size of cellulosic fibers, to fillers at a few microns, and to colloids. Within this range are cellulosic fines, mineral fillers (employed to increase opacity, brightn~sc and other paper characten~tics) and other small particles that generally, without the inclusion of one or more retention aids, would in significant portion pass through the spaces (pores) between the cellulosic fibers in the fiber mat being fommed during papemmaking.
One method of improving the retention of cellulosic fines, mineral fillers and other fumish components on the fiber mat is the use of a coagulant/flocculant system, added ahead of the paper machine. In such a system there is first added a coagulant, for 10 instance a low molecular weight cationic synthetic polymer or a cationic starch to the furnish. which coagulant generally reduces the negative surface charges present on the particles in the fumish. particularly cellulosic fines and mineral fillers, and thereby accomplishes a degree of agglomeration of such particles, followed by the addition of a flocculant. Such flocculant generally is a high molecular weight anionic synthetic I ~ polymer w hich bridges the particles andlor agglomerates, from one surface to another, bindins~ the particles into large agglomerates. The presence of such large agglomerates in the furnish as the fiber mat of the paper sheet is being formed increases retention. The a~ lomerates are filtered out of the ~hater onto the fiber web, where unagglomerated particles ~ould to a great extent pass through such paper web.
'O While a flocculated ag,~lomerate generally does not interfere with the drainage of the fiber mat to the extent that ~ould occur if the furnish were gelled or contained an amount oi' gelatinous material. ~hhen such flocs are filtered by the fiber web the pores thereof are to a degree reduced, reducing the drainage efflciency therefrom. Hence the retention is being increased with some degree of deleterious effect on the drainage.
Another system employed to provide an improved combination of retention and dewatering is described in United States Patent No. 4,753,710 and United States Patent No. 4.913,775, inventors Langley et al., issued respectively June 28, 1988 and April 3, 1990. incorporated hereinto bv reference. In brief, such method adds to the aqueous cellulosic paperm~king suspension first a high molecular weight linear cationic polymer before shearing the suspension, followed by the addition of b~;lllol~il~ after shearing. The shearin~ generally is provided by one or more of the cleaning, mixing and pumping ] 0 stages of the papermaking process. and the shearing breaks down the large flocs formed by the hi_h molecular weight polymer into microflocs, and further agglomeration then ensues w ith the addition of the bentonite clay particles.
Another svstem uses the combination of cationic starch followed by colloidal silica to increase the amount of material retained on the web by the method of charge 1~ neutralization and adsorption of smaller agglomerates. This system is described in l~nited States Patent No 4.38~ 0. in~entors Sunden et al., issued June 14, 1983.Dewatering generall!. and particularl! dewatering by drainage, is believed impro~ ed ~ hen the pores of the paper weh are less plugged, and it is believed that retention by adsorption in comparison to retention by filtration reduces such pore ~0 pluggin~n Greater retention of fines and fillers permits, for a given grade of paper, a reduction in the cellulosic fber content of such paper. As pulps of less quality are employed to reduce paperm~kin~ costs, the retention aspect of p~p~rm~king becomes even more important because the fines content of such lower quality pulps is greater generally than that of pulps of higher quality.
Greater retention of fines, fillers and other slurry components reduces the amount 5 of such substances lost to the white water and hence reduces the amount of material w astes. the cost of waste disposal and the adverse environment~l effects therefrom.
Another important characteristic of a given paperm~kin~ process is the formation of the paper sheet produced. Formation is determined by the variance in light transmission within a paper sheet. and a high variance is indicative of poor formation. As 10 retention increases to a high level, for instance a retention level of 80 to 90 percent. the formation parameter generally abruptly declines from good formation to poor formation.
It is at least theoretically believed that as the retention mech~ni~ms of a given papermal;ing process shiR from filtration to adsorption~ the deleterious effect on forrnation. as high retention levels are achieved~ will rlimini~h, and a good combination of ] ~ hi, h retention with good forrnation is attributed to the use of bentonite in U. S. Patent No.
4.9 1 ,.77~.
It is generall- desirable to reduce the amount of material employed in a papermaking process for a ,~iven purpose. ~ithout ~limini~hing the result sought. Such add-on reductions may realize both a material cost savings and handling and processing ~0 benefits.
It is also desirable to use additives that can be delivered to the paper machine ~ithout undue problems. An additive that is difficult to dissolve, slurry or otherwise CA 0223~637 1998-07-23 disperse in the aqueous medium may require expensive equipment to feed it to the paper machine. When difficulties in delivery to the paper m~ ine are encountered, the additive is often m~int~ined in aqueous slurry form by virtue of high energy input equipment. In contrast, additives that are easily dissolved or dispersed in water require less energy and 5 expense and their uniformity of feed is more reliable.
Summan of the Invention The claimed invention comprises a paperrn~kin~ process comprising forming an aqueous cellulosic papermaking slurry, subjecting the slurry to one or more shear stages, adding to the slurry a mineral filler prior to at least one of the shear stages, adding to the 10 slurry after the addition of the mineral filler and prior to at least one of the shear stages an effective amount of a dispersion polymer selected from the group consisting of copol- mers of acrylarnide and dimethylaminoethylacrylate methyl chloride quaternary salt (DMAEA.MCQ). dimethylaminoethylmethacrylate methyl chloride quaternary salt (DMAEM.MCQ)~ dimethylaminoethylacrvlate benzyl chloride quaternary salt I ~ (DMAEA.BCQ) and dimethylaminoethylmethacrylate benzyl chloride quaternary salt (DMAEM.BCQ) and diallyldimethvlammonium chloride (DADMAC), shearing the slurr~ . adding a microparticle selected from the ~roup consisting of organics such as copolymers of polyacrylic acid. inor~anics such as bentonite and silica sol, draining the slurr~ to forrn a sheet. and drvin~ the sheet to form a paper sheet.
'O Descrir)tion of the Preferred Embodiments According to the invention. a water soluble polymer is added to a cellulosic slurry before the formation of a paper product. The water soluble polymer should become substantially dispersed within the slurry before formation of the paper product in any case. The microparticle of the invention is added after ~h~ring of the slurry. The addition of the polymer in an aqueous medium, for instance as a water solution or dispersing, facilitates the dispersion of the polymer of the slurry. In a prefelled 5 embodiment, the polymer is added to the cellulosic slurry before the processing steps of draining and forming the paper sheet.
The present process is believed applicable to all grades and types of paper products. and further applicable for use on all types of pulps including, without limitation. chemical pulps. including sulfate and sulfite pulps from both hard and soft 10 woods and acid pulps. thermo-mechanical pulps, mechanical pulps, recycle pulps and ground wood pulps, although it is believed that the advantages of the process of the present invention are best achieved when the pulp employed is of the chemical pulp type, particularly alkaline chemical pulp.
In preferred embodiment the filler used in the cellulosic slurry is anionic, or at 15 least partially anionic. Other minerak or inorganic~ fillers may, however, be used, such as calcium carbonate. clay. titanium dioxide. or talc or a combination may be present.
The amount of alkaline inorganic filler. such as one of the alkaline carbonates, enerall!~ employed in a papermakin,~ stocl; is from about 10 to about 30 parts by weight of the filler~ as CaC03, per hundred parts by weight of dry pulp in the slurry, but the ~0 amount of such filler may at times be as lou as about 5, or even about 2, parts by weight, and as high as about 40 or even 50 parts by weight, same basis.

CA 0223~637 1998-07-23 The reduced specific viscosities of the polymers and copolymers as reported herein were determined in 0.125M sodium nitrate solution from published data.
Similarly, all molecular weights of the polymers as reported herein are the approximate weight average molecular weights of the polymers.
The dispersion polymerization process used to m~nllf~,ture the polymers of the invention offer numerous advantages which have previously been unavailable. Since the pol,vmers of the invention are synthesized entirely in water, no oil solvent is required.
This is significant since:
1 ) the pol,vmers of the invention do not present a fire hazard, 2) oil is not added to the water which is to be treated (more environmental friendly);

3) dissolution of the polymers of the invention requires only the addition of water, no special activators are needed;

4) the abilit,v of the polymers of the invention to dissolve/invert is superior to that of oil dispersion latexes; and S) the polymers of the invention may be diluted to virtually any concentration by usin~ appropriatel,v concentrated salt water.
Another major advanta,~e is that the bulk viscosity of the polymer is low, unlike some oil dispersion latex polvmers. This physical property enables any standard chemical pump to deliver the material at the injunction site.
A new class of water-soluble dispersion polymers have been discovered to be more effective in increasin~ draina~e and retention than currently available chemical treatments. As will be discussed in more detail below, the polymer dispersion of the CA 0223=,637 1998-07-23 - invention is prepared in an aqueous solution of a polyvalent anionic salt. The polymer dispersion of the invention achieves fine particle sizes and aqueous solubilities not available with other polymers used for this application. Furthermore, there does not appear to be a problem with overfeeding the polymer dispersion which is a drawback 5 with latex polymers.
According to the method~ the dispersion polymer of the invention is added to a cellulosic papermaking slurry. The polymer is added in an effective amount of from 0.5 to about 100 ppm. More preferably, the amount of the polymer added is from 2 to about 40 ppm: and most preferably from about 4 to about 25 ppm. It is believed, that there does 10 not appear to be a maximum dosage at which the polymers adversely affect the system.
At some higher doses the beneficial effect may plateau, and on a cost basis such higher doses. probably above about 100 ppm. are not cost effective. The polymers of the invention are preferably added to the system in neat form. However, in some applications. the polvmers can be added as an aqueous solution.
I ~ The preferred pol- mers of the invention are manufactured by Hymo Corporation, Japan Methods for manufacturing the polymer dispersion used in the invention is described in detail in IJ . S. Patent No. 5~006.590 and U. S. Patent No. 4,929,655, assigned to 1~;~ oritsu 'r ul;i Co.. Ltd.. To~vo. Japan. The disclosures of these two patents are incorporated herein b~ reference '() ln the preferred embodiment of the invention~ an organic or inorganic microparticle is added to the slurr~ after the introduction of shear. Preferably, the organic microparticle is a medium molecular weight anionic polymer such as the copolymers of acrylic acid described in U.S. Patent No. 5,098,520, the disclosure of which is incorporated herein by reference, or medium molecular weight anionic sulfonated polymers such as those described in U.S. Patent No. S,l 85,062, the disclosure of which is incorporated herein by reference. The inorganic microparticle may be preferably chosen S from among bentonite and silica sol.
According to the invention, the dispersion polymer used to treat the cellulosic papermaking slurry may further be prepared from a water-soluble monomer mixture containing at least S mole % of a cationic monomer represented by the general formula (I) R, CH,=C R1 O=C A1 B1 ~ --CH2 ~ X(~) iO R~

wherein Rl is H or CH3: R~ and R, are each ,an ali;yl group having l to 2 carbon atoms;
Al is an oxv~en atom or NH: Bl is an, li~ roup having 2 to 4 carbon atoms or a 1~ hydro~;ypropyl group and Xl is a counter anion.
The above water-soluble monomer mixture is soluble in the aqueous solution of the pol~ valent anionic salt. The polvmer L~enerated from the monomer mixture is, ho~ ever. insoluble in the aqueous polyvalent anionic salt solution. The polymer of the CA 0223~637 1998-07-23 monomer mixture can also be used as the seed polymer. The seed polymer is described in detail below.
The above cationic monomer represented by the general formula (I) preferably is a quatemary ammonium salt obtained by the reaction of methyl chloride or ben~yl 5 chloride and dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminohydroxypropyl acrylate, dimethylaminopropyl acrylamide, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrvlate and dimethylaminopropyl methacrylamide.
The concentration of the above-mentioned monomers in the polymerization 10 reaction mixture is suitably in the range of 1.0 to 30% by weight for the methyl chloride quatemary ammonium salt. Preferably, the concentration is from about 10 to about 20%
by ~ eight. For the benzyl chloride quaternary ammonium salts, the concentration in the polymerization reaction mixture is suitably in the range of from about 1.0 to about 35%
b~ ~ei~ht. Preferably. the concentration is from about 10 to about 20% by weight.
Monomers preferably copolymerized with the cationic monomer are represented b~ the ~eneral formula (I) includes acrylamide. methacrylamide and the cationic monomers represented by the ~,~eneral formula (11):

R~
CH,=C R4 O=C A2 B2 ~ R~ X9 (II) I

R~, CA 0223~637 1998-07-23 5 wherein R4 is H or CH3; R, and R6 are each an alkyl group having 1 to 2 carbon atoms;
A7 is H or an alkyl group having 1 to 2 carbon atoms; A2 is an oxygen atom or NH; B2 is an alkyl group having 2 to 4 carbon atoms or a hydroxypropyl group and X2 is a counter anion Preferable monomers represented by the formula (II) include the ammonium salts 10 of dimethylaminoethyl acrylate. diethylaminoethyl acrylate, dimethylaminopropyl acrylamide. diethylaminopropyl acrylarnide and dimethylhydroxypropyl acrylate, dimethylaminoethyl methacrylate~ diethylaminoethyl methacrylate, dimethylaminopropyl methacrylamide~ diethvlarninopropyl methacrylamide and dimethylhydroxypropyl methacrylate as well as the methvlated and ethylated quaternary salts. Among the more I ~ preferable cationic monomers represented by the general formula (II) are the salts and methylated quaternary salts of dial~;ylaminoethyl acrylate and dialkylaminoethyl methacrylate The poly v alent anionic salt to be incorporated in the aqueous solution according to the present invention is suitabl! a sulfate. a phosphate or a mixture thereof. Preferable 'O salts include ammonium sulfate. sodium sulfate. magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate. sodium hydrogenphosphate and potassium CA 0223~637 1998-07-23 hydrogenphosphate. In the present invention, these salts may be each used as an aqueous solution thereof having a concentration of 15% or above.
A dispersant is present in the aqueous anionic salt solution in which the polymerization of the above monomers occurs. The dispelsallt is a water-soluble high 5 molecular weight cationic polymer. The di~ t is soluble in the above-mentioned aqueous salt solution. The dispersant is preferably used in an amount of from 1 to 10%
by weight based on the total weight of the monomers. The dispersant is composed of 20 mole % or more of cationic monomer units leplesellted by the formula (II). Preferably the residual mole % is acrylamide or methacrylarnide. The performance of the dispersant 10 is not greatly affected by molecular weight. However, the molecular weight of the dispersant is preferably in the range of 10,000 to 10,000,000 daltons. According to one embodiment of the invention a multifunctional alcohol such as glycerin or polyethylene glycol is coexistent in the polymerization system. The deposition of the fine particles is smoothl~ carried out in the presence of these alcohols.
I ~ For the polvmerizations a usual water-soluble radical-forming agent can be emploved. but preferably water-soluble azo compounds such as 2,2'-azobis(2-amidinopropane) hvdrochloride and '.~'-azobis(N.N'-dimethyleneisobutylamine) h-drochloride are used.
According to one embodiment of the invention, a seed polymer is added before ~() the beginning of the polymerization of the above monomers for the purpose of obtaining a fine dispersion. The seed pol~mer is a water-soluble cationic polymer insoluble in the aqueous solution of the pol~ valent anionic salt. The seed polymer is preferably a polymer prepared from the above monomer mixture by the process described herein.
Nevertheless, the monomer composition of the seed polymer need not always be equal to that of the water-soluble cationic polymer formed during polymerization. However, like the water-soluble polymer formed during polymerization, the seed polymer should contain at least ~ mole percent of cationic monomer units represented by the general formula (I). According to one embodiment of the invention, the seed polymer used in one polvmerization reaction is the water-soluble polymer prepared in a previous reaction which used the same monomer mixture.
Examples The following examples are presented to describe preferred embodiments and utilities of the invention and are not meant to limit the invention unless otherwise stated in the claims appended hereto. In the following examples, common terms used throu~hout have the following meanings.
Microparticle A (colloidal silica) I ~ Dispersed silica in water with a particle size of 4 nm.
Microparticle B
Copol~ mer of acrvlic acid Microparticle C (bentonite) H~ drated suspension of powdered bentonite in water ~0 Dispersion Polymers Polymer A 10 mole% DMAEA.BCQ RSV 19.6 dl/g Polymer B 10 Mole % DMAEA.MCQ RSV 21.4 dl/g Polymer C 20 mole % DMAEA.MCQ RSV 27.6 dl/g Latex Polymer Polymer D 10 mole% DMAEA.MCQ RSV 19.7 dl/g The Reduced Specific Viscosity (RSV) was measured at a concentration of 0.045% polymer in a solution of 0.125M NaNO3 solution.
Britt Jar Test The Britt Jar Test employed in Examples I to 3 used a Britt CF Dynamic 10 Drainage Jar developed b- K. W. Britt of New York State University, which generally consists of an upper charnber of about 1 liter capacity and a bottom drainage chamber, the charnber being separated bv a support screen and a drainage screen. Below the drainage chamber is a downward extending flexible tube equipped with a clamp for closure. The upper chamber is provided w ith a v ariable speed. high torque motor equipped with a 2-I 5 inch ~-bladed propeller to create controlled shear conditions in the upper chamber. The tes~ ~as conducted bv placing the cellulosic stocl; in the upper chamber and then subjectins~ the stock to the followin sequence:

CA 0223~637 1998-07-23 Time Action 0 seconds Commence shear stirring at 750 rpm, (add starch, if needed).
Add the cationic polymer, increase speed to seconds 2000 rpm.
Reduce shear stirring to 750 rpm.
seconds Add the microparticle.
seconds Open the tube clamp to commence drainage, seconds and continue drainage for 30 seconds.

The material so drained from the Britt jar (the "filtrate") is collected and diluted ~ ith u ater to one-fourth of its initial volume. The turbidity of such diluted filtrate, measured in Formazin Turbidity Units or FTU's, is then determined. The turbidity of such a filtrate is inversely proportional to the papermaking retention performance; the lou er the turbidity value. the higher is the retention of filler and/or fines. The turbidity ~alues uere determined usin~ a Hach Spectrophotometer, model DR2000.
The turbidity values (in FTU) that were determined were converted to (Percent 10 Impro~ement) ~alues usin(l the formula:

Percent Improvement= 100 X (Turhidir~ Turhidityt)/Turbidityu where Turbidityu is the turbidit~ readin~ result for the blank for which no polymer or I ~ microparticle. and uherein Turhiditl l is the turbidity reading result ofthe test using pol~ mer or polymer and microparticle.

CA 0223~637 1998-07-23 Filtration Test The filtration tests used in Examples 1 to 8 me~llred the drainage (water removal) rate of the test stock subjected to the various chemical tre~tment~. A filtration 5 cell, mounted upright on a stand, was used. The capacity of this cell is about 220 milliliters. A 200 mesh drainage screen (7611m screen with 8% opening) served as the filter medium. The stock was filtered by gravity. The filtrate was collected in a cup placed on a weighing balance below the cell. This balance was interfaced with a computer so that the displayed weight was recorded continuously over time. The 10 computer automatically recorded the change of weight over time.
The cellulosic stock was treated in the aforementioned Britt jar. The treated stock was transferred to the cell and filtered until completion. The rate of filtrate collection is an indication of the drainage performance; the higher the filtrate collection rate, the higher is the improvement in drainage.
I 5 Test Stocks All;aline Test Stock The cellulosic stock or slurry used in Examples I to 3 and 8 was comprised of 70 weight percent fiber and 30 wei ht percent filler. diluted to an overall consistency of 0.5 percent with formulation water. The fiber was a 60/40 blend by weight of bleached 20 hardwood Kraft and bleached softwood ~raft. separately beaten to a C~n~ n Freeness v alue range of from 320 to 360 C.F.S. The filler was a commercial calcium carbonate, provided in dry form. The formulation water contained 60 ppm calcium hardness (added CA 0223~637 1998-07-23 as CaC12 ), 18 ppm ma~nesium hardness (added as MgSO4) and 134 ppm bicarbonate alkalinity ( added as NaHC03). The pH of the final thin stock was pH 7.~.

Acid Test Stock The cellulosic stock or slurry used in Examples 4 to ~ was comprised of 93 5 weight percent fiber and 7 weight percent filler, diluted to an overall consistency of 0.54 percent with formulation water. The fiber was a 50/50 blend by weight of bleached hardwood Kraft and bleached softwood Kraft, separately beaten to a C~n~ n Freeness value range of from 320 to 360 C.F.S. The fillers were clay as predispersed kaolin and titanium dioxide. commercially provided in dry forrn. The pH was adjusted to pH 4.00 10 usin~ dilute sulfuric acid. following which alum (0.005% of final slurry) and sizing agent rosin (0.00~ wt% of final slurry) were added. The formulation water contained 60 ppm calcium hardness (added as CaCI,). 18 ppm magnesium hardness (added as MgSO4) and 13~ ppm bicarbonate alkalinity ( added as NaHCO3).

Corru~ated Coated Test Stocli I ~ The stock used in E~;amples 6 and 7 was obtained as thick stock (consistency of .1 1 ~,0) from a paper mill. It ~as a mi~;ture of OCC. newsprint~ and boxboard. It was diluted to an o~ erall consistenc! of 0 8~/o ~ith formulation water containing 60 ppm calcium hardness (added as CaCI~ ). 18 ppm mapnesium hardness (added as MgSO4) and 1 ~ ppm bicarbonate alkalinit~ ( added as ~aHC03). The final pH of the thin stock was 'O pH 6.~. The percent ash of the thin stocli ~as 7.3 wt%.

Example 1 - ' Usin_ the alkaline test stock described above, the Britt jar test, also described above was employed to determine the retention performances of dispersion Polymer A in comparison to the inverse emulsion Polymer D, with microparticle A as the microparticle. In each test. cationic potato starch was charged to the test stock in the amount of 10 Ib/ton of dry wei~ht of slurry solids. The various programs tested are shown below in Table l. The test results are reported in Table l below as diluted filtrate turbidity values (FTU) and (Percent Improvement), as defined earlier, for each of the pro_rams tested.
The drainage performance of these programs was measured for the same alkaline furnish using the filtration test described above. In each test starch was charged to the I 5 test stocli in the amount of 10 Ib/ton of dry weight of slurry solids. The results are shown for each of the programs tested in Fi~ure I as graphs of collected filtrate weight versus time.
Example 2 Using the alkaline test stock described above. the Britt jar test, also described 'O above uas employed to deterrnine the retention performances of dispersion Polymer B in comparison to the inverse emulsion Polvmer D with microparticle A as the microparticle. In each test. cationic potato starch was charged to the test stock in the amount of 10 Ib/ton of dry weight of slurry solids. The various programs tested are shown below in Table 2. The test results are reported in Table 2 below as diluted filtrate turbidity values (FTU) and (Percent Improvement), as defined earlier, for each of the prograrns tested.
The drainage perforrnance of these programs was measured for the sarne alkaline furnish using the filtration test described above. In each test starch was charged to the test stock in the amount of 10 lb/ton of dry weight of slurry solids. The results are shown for each of the programs tested in Figure 2 as graphs of collected filtrate weight versus time.
Table I
Britt Jar Retention Tests Alkaline Furnish I~io. Polvmer Polymer Microparticle Turbidity Percent Dosage A Dosage (FTU)Improvement Ib/ton Ib/ton blank 0 0 359 5 A 1.6 0 289 20 2 A 1.6 2 84 77 3 D 1.6 0 291 19 4 D 1.6 2 162 55 Table II
Britt Jar Retention Tests Alkaline Furnish No.PolymerPolvmerMicroparticle Turbidity Percent Dosage A Dosage (FTU) lmprovement Ib/ton Ib/ton blank O 0 359.5 B 1.6 0 252 30 2 B 1.6 2 74 79 3 D 1.6 0 291 19 4 D 1.6 2 162 55 FYanlple 3 Using the ~lk~line test stock described above, the Britt jar test, also described above was employed to determine the retention performances of dispersion Polymer C in comparison to the inverse emulsion Polymer D, with microparticle A as the 5 microparticle. In each test. cationic potato starch was charged to the test stock in the amount of 10 lb/ton of drv weight of slurry solids. The various programs tested are shown below in Table 3. The test results are reported in Table 3 below as diluted filtrate turbidity values (FTU) and (Percent Improvement), as defined earlier, for each of the programs tested Table III
Britt Jar Retention Tests Alkaline Furnish 1~ o.Polvmer Polvmer Microparticle Turbidity Percent DosageA Dosage (FTU)Improvement Ib/ton Ib/ton blan~; 0 0 359 ~
C 1.6 0 266 26 C I .6 ' 1 20 67 D 1.6 0 291 19 D 1.6 ~ 162 1( E~;ample ~
IJsing the acid test stocli described above. the filtration test, also described above ~as employed to determine the dr~in~e performances of dispersion Polymer A in comparison to the inverse emulsion Pol~ mer D. with microparticle A as the I ~ microparticle. The results are sho~n for each of the programs tested in Figure 3 as graphs of collected filtrate ~ei~ht v ersus time.

CA 0223~637 1998-07-23 FY~nlPIe5 Using the acid test stock described above, the filtration test, also described above was employed to determine the drainage performances of dispersion Polymer A in 5 comparison to the inverse emulsion Polymer D, with microparticle B as the micropanicle.
The results are shown for each of the programs tested in Figure 4 as graphs of collected filtrate weight versus time.

Example 6 Using the corru~ated coated test stock described above, the filtration test. also described above was emploved to deterrnine the drainage perforrnances of dispersion Pol! mer A. with micropanicle A as the micropanicle. The results are shown for each of the programs tested in Figure 5 as graphs of collected filtrate weight versus time.

I 5 E~;ample 7 l~sing the corrugated coated test stocl; described above, the filtration test, also described above was emplo~ ed to determine the drainage performances of dispersion Pol~ mer A. with micropanicle B as the micropanicle. The results are shown for each of the pronrams tested in Fl~ure 6 as ~raphs of collected filtrate weight versus time.
~O
Example 8 CA 0223~637 1998-07-23 Using the alkaline test stock described above, the filtration test, also described above was employed to determine the drainage performances of dispersion Polymer A in comparison to the inverse emulsion Polymer D, with microparticle C as the microparticle.
In each test, cationic potato starch was charged to the test stock in the amount of 10 lb/ton 5 of dr- weight of slurry solids. The results are shown for each of the programs tested in Figure 7 as graphs of collected filtrate weight versus time.
Changes can be made in the composition, operation and arrangement of the method of the present invention described herein without departing from the concept and scope of the invention as defined in the following claims:

Claims (10)

1. A papermaking process comprising forming an aqueous cellulosic papermaking slurry, subjecting the slurry to one or more shear stages, adding to the slurry a mineral filler prior to at least one of the shear stages, adding to the slurry after the addition of the mineral filler and prior to at least one of the shear stages an effective amount of a cationic dispersion polymer selected from the group consisting of copolymers of acrylamide and dimethylaminoethylacrylate methyl chloride quaternary salt. dimethylaminoethylmethacrylate methyl chloride quaternary salt, dimethylaminoethylacrylate benzyl chloride quaternary salt, dimethylaminoethylmethacrylate benzyl chloride quaternary salt and diallyldimethylammonium chloride;
shearing the slurry;
adding a microparticle selected from the group consisting of a copolymer of acrylic acid, bentonite and silica sol:
draining the slurry to form a sheet; and drying the sheet to form a paper sheet.

2. The process of claims 1 wherein the dispersion polymer has a molecular weight of from about 10.000 to 10,000.000 daltons.

3. The process of claim 1 wherein the slurry is drained on a papermaking screen and is pumped to the site of the papermaking screen prior to draining.

4. The process of claim 1 wherein the slurry is selected from the group consisting of an acid pulp slurry, alkaline chemical pulp slurry, thermo-mechanical pulp slurry, mechanical pulp slurry recycle pulp slurry and ground wood pulp slurry.

5. The process of claim 1 wherein the mineral filler is selected from the group consisting of titanium dioxide, clay and, talc calcium alkaline carbonate.

6. The process of claim 1 wherein the mineral filler is added to the slurry in an amount of from about 2 to about 50 parts per hundred parts by weight of dry pulpcontained in the slurry.

7. The process of claim 1 wherein the concentration of methyl chloride quaternary salt is from about 1.0 to about 30 mole percent.

8. The process of claim 7 wherein the concentration of methyl chloride quaternary salt is from about 10 to about 20 mole percent.

9. The process of claim 1 wherein the concentration of benzyl chloride quaternary salt is from about 1.0 to about 35 mole percent.

10. The process of claim 9 wherein the concentration of benzyl chloride quaternary salt is from about 10 to about 20 mole percent.