A MICROPARTICLE SYSTEM IN THE PAPER MAKING PROCESS

Abstract: A retention and drainage aid comprising a microparticle system for use in the production of an alkaline and an acid paper product comprises a flocculant polymer and an inorganic particulate material comprising an aluminum substituted trioctahedral mineral, and optionally a cationic coagulant. The polymer flocculant is added to the furnish after the fan pump and prior to the pressure screen; the inorganic particulate material is added to the furnish after the pressure screen, and optionally, the coagulant is added prior to the fan pump.

Description: "A MICROPARTICLE SYSTEM IN THE PAPER MAKING PROCESS" BACKGROUND OF THE INVENTION 1. Field Of The Invention The present invention relates to an improved microparticle system and to a method using the improved microparticle system as an aid in making a paper product, i.e., paper or paperboard, with improved properties in the areas of retention, drainage, and sheet formation. 2. Description Of The Background Art In the production of paper or paperboard, a dilute aqueous composition known as "furnish" or "stock" is sprayed onto a moving mesh known as a "wire". Solid components of this composition, such as cellulosic fibers and inorganic particulate filler material, are drained or filtered by the wire to form a paper sheet. The percentage of solid material retained on the wire is known as the "first pass retention" of the paper making process . Retention is believed to be a function of different mechanisms, such as filtration by mechanical entrainment, electrostatic attraction, and bridging between the fibers and the fillers in the furnish. Because both the cellulosic fibers and many common filler materials are negatively charged, they are mutually repellent. Generally, the only factor tending to enhance retention is mechanical entrainment. Therefore, a retention aid is generally used to improve retention of the fibers and fillers on the wire. Drainage relates to the rate of removal of water from the furnish as the paper sheet is formed. Drainage usually refers only to water removal which takes place before any pressing of the paper sheet subsequent to formation of the sheet. Thus, drainage aids are used to improve the overall efficiency of dewatering in the production of paper or paperboard. Formation relates to the formation of the paper or paperboard sheet produced from the paper making process. Formation is generally evaluated by the variance of light transmission within a paper sheet. A high variance is indicative of "poor" formation and low variance is generally indicative of "good" formation. Generally, as the retention level increases, the level of formation generally decreases from good formation to poor formation. It can be appreciated that improvements in retention and drainage and in the formation properties of the final paper or paperboard sheet are particularly desirable for several reasons, the most significant of which is productivity. Good retention and good drainage enable a paper machine to run faster and to reduce machine stoppage. Good sheet formation lessens the amount of paper wastage. These improvements are realized by the use of retention and drainage aids . Retention and drainage aids are additives which are used to flocculate the fine solid material present in the furnish to improve these parameters in the paper making process . The use of such additives is limited by the effect of flocculation on the paper sheet formation. If more retention aid is added so the size of the aggregates of the fine solid material is increased, then this generally results in variations in the density of the paper sheet which, as stated hereinabove, may result in what is referred to as "poor" sheet formation. Over-flocculation can also affect drainage as it may eventually lead to holes in the sheet and a subsequent loss of vacuum pressure in the later stages of dewatering during the paper making process. Added to the furnish in the wet-end of the paper machine, retention and drainage aids are generally of three types, viz: (a) single polymers; (b) dual polymers; or (c) microparticle systems which may be used with a flocculant and/or a coagulant. A microparticle system may generally give the best result as a retention and drainage aid, and has been widely described in the prior art. Examples of publications of microparticle systems include: EP-B-235, 893 wherein bentonite is used as the inorganic material in conjunction with a high molecular weight cationic polymer in a specified addition sequence; WO-A-94/26972 wherein a vinylamide polymer is described for use in conjunction with one of various inorganic materials such as silica, bentonite, china clay, and organic materials; O-A-97/16598 wherein kaolin is described for use in conjunction with one of various cationic polymers; and EPO 805234 wherein bentonite, silica or acrylate polymer is used in conjunction with a cationic dispersion polymer . Additional microparticle systems which include bentonite as being an inorganic material are disclosed in U.S. Patent Nos . 4,749,444; 4,753,710; 4,913,775; 4,969,976; 5,126,014; 5,234,548; 5,393,381; 5,415,740; 5,514,249; and 5,532,308. These several microparticle systems employ a flocculant and/or a coagulant added to the wet end of a paper machine along with the inorganic material in a specified addition sequence. A microparticle system including a water swellable smectite clay used with an anionic polymer dispersant is disclosed in U.S. Patent No. 5,015,334. U.S. Patent No. 5,071,512 discloses a microparticle system using hectorite, in conjunction with a cationic starch. U.S. Patent No. 5,178,730 discloses a microparticle system comprising hectorite used in conjunction with a medium or high molecular weight cationic polymer. U.S. Patent No. 5,194,120 discloses the use of a synthetic amorphous magnesium silicate, e.g., laponite, in conjunction with a medium or high molecular weight cationic polymer. The components of these several microparticle systems are added in the wet end of the paper machine in a specified addition sequence relative to one or more shearing stages, for instance cleaning, mixing, and pumping stages such as those typified by centriscreens, vortex cleaners, fan pumps, and mixing pumps. Several of these prior art microparticle systems discussed hereinabove generally describe "bentonite" as being the inorganic material. However, this term "bentonite" is used loosely and generally should not be considered as including saponite, more about which will be discussed hereinafter. A microparticle system generally comprises a polymer flocculant with or without a cationic coagulant and a fine inorganic particulate material . The inorganic material improves the efficiency of the flocculant and/or allows smaller, more uniform floes to be produced. In spite of the several microparticle systems presently available for use in the paper mills to attain better runnability of the paper machine and/or to obtain a specific end use paper property, such as improved sheet formation for better printability, or improved surface strength, there remains a very real and substantial need for a microparticle system for improving the paper or paperboard by improving drainage, retention, and formation properties during the paper making process. SUMMARY OF THE INVENTION The present invention has met this above described need. The present invention relates to a microparticle system used as a retention and drainage aid in a paper making process. According to a first aspect of the present invention, there is a method of producing paper which comprises adding to a paper stock or furnish a microparticle system as a retention and/or drainage aid which comprises a high molecular weight polymer flocculant and an inorganic particulate material, wherein the inorganic particulate material comprises aluminum substituted trioctahedral minerals, e.g., saponite. According to a second aspect of the present invention, there is an improved microparticle composition which may be added to a paper stock or furnish as a retention and/or drainage aid, and which microparticle composition comprises a high molecular weight polymer flocculant and an inorganic particulate material, wherein the inorganic particulate material comprises aluminum substituted trioctahedral minerals, e.g., saponite. According to a third aspect of the present invention, there is a paper or a paperboard product with improved properties in the area of retention, drainage and formation wherein the paper or paperboard product is made by adding an improved microparticle system to an aqueous cellulosic paper stock or furnish wherein the microparticle system comprises a high molecular weight polymer flocculant and an inorganic material comprising aluminum substituted trioctahedral minerals, e.g., saponite . A fourth aspect of the invention involves a process in which paper or paperboard is made by forming an aqueous cellulosic paper furnish comprising: (a) adding to the thin stock flow of the paper furnish a high molecular weight polymer flocculant after a first shearing stage and an inorganic particulate material comprising aluminum substituted trioctahedral minerals, e.g., saponite, after a second shearing stage to the thin stock flow of the paper furnish; (b) draining the paper furnish to form a sheet; and (c) drying the .sheet. BRIEF DESCRIPTION '' OF THE FIGURES Figure 1 is a sketch illustrating a portion of a typical paper machine and the points σf addition of the components of the microparticle system of the present invention in a preferred form. Figure 2 is a three-dimensional surface graph showing drainage vs. polymer dosage vs. saponite dosage for saponite Sample 1, 5% clay filler of the first set of examples . Figure 3 is a three-dimensional surface graph showing drainage vs. polymer dosage vs. saponite dosage for saponite Sample 1, 20% clay filler of the first set of examples. Figure 4 is a three-dimensional surface graph showing drainage vs. polymer dosage vs. saponite dosage for saponite Sample 2, 20% clay filler of the first set of examples. Figure 5 is a two-dimensional graph showing the turbidity of a sample containing saponite vs. a sample not containing saponite. Figure 6 is a graph plotting the results for drainage, MK formation and first pass ash retention (FPAR (%)) for Examples 5-8 of the present invention in the second set of examples. Figure 7 is a graph plotting the results for drainage, MK formation, and first pass ash retention (FPAR (%) ) for Examples 9-12 of the present invention in the second set of examples . DETAILED DESCRIPTION OF THE INVENTION The instant invention is directed to a microparticle system as a retention and/or drainage aid for particular use in the wet end of a paper machine in the paper making process for both acid and alkaline fine paper. As used herein, the term "paper" includes products comprising a cellulosic sheet material' including paper sheet, paper board and the like. As used herein, "microparticle system or composition" refers to the combination of at least one hydrophilic polymer and at least one inorganic particulate material. The components of this combination may be added together to the stock or furnish to be treated, but are preferably added separately in the manner and order described hereinbelow. The invention can be carried out using a conventional paper making machine. According to conventional practice, the furnish or "thin stock" that is drained to form the paper sheet is often made by diluting a thick stock which typically has been made in a mixing vessel or chest by blending pigment or filler material, the appropriate fiber, any desired strengthening agent and/or other additives, and water which may be recycled water. The thin stock may be cleaned in a conventional manner, e.g., using a vortex cleaner. Usually the thin stock is cleaned by passage through a centriscreen. The thin stock is usually pumped along the paper machine by one or more centrifugal pumps known as fan pumps . For instance the thin stock may be pumped to the centriscreen by a first fan pump. The thick stock can be diluted by water to form the thin stock prior to the point of entry to this first fan pump or prior to the first fan pump, e.g., by passing the thick stock and dilution water through a mixing pump. The thin stock may be cleaned further by passage through a second centriscreen or pressure screen and passed through a head box prior to the sheet forming process of a paper machine. The sheet forming process may be carried out by use of any conventional paper or paperboard forming machine, for example a flat wire fourdrinier, a- twin wire former, or a vat former or any combination of these forming machines . An approach system to a paper machine may comprise the components shown in Figure 1. These components include a fan pump 1, a pressure screen 2, and a headbox 3. The thick stock is diluted by water to the thin stock prior to entry into fan pump 1 by passing the thick stock and dilution water through a mixing pump [not shown] . The thin stock is cleaned of contaminants by passage through pressure screen 2 and the thin stock that leaves pressure screen 2 is passed to headbox 3 prior to the sheet formation. Figure 1 also illustrates the preferred points of addition for the components of the microparticle system of the present invention. Preferably, if a cationic coagulant is used, it is added to the thin stock prior to the thin stock being passed through fan pump 1 which travel is indicated by arrow 4 and which addition is indicated by arrow 5. The flocculant is added to the thin stock as it exits fan pump 1, as indicated by arrow 6, and the inorganic particulate material is added to the thin stock as the thin stock exits pressure screen 2 as indicated by arrow 7. Fan pump 1 and pressure screen 2 produce high shear stages in the paper machine . In the invention, the high molecular weight flocculant polymer of the microparticle system is preferably added before the thin stock reaches the last point of high shear and the resultant thin stock is preferably sheared, e.g., at the last point of high shear, before adding the inorganic particulate material of the microparticle system. In Figure 1, the flocculant is shown as being 'added before the thin stock travels through pressure screen 2 and the microparticle is shown as being added after the stock passes through pressure screen 2. Preferably, the flocculant of the microparticle system of the invention is added to the thin stock (i.e. having a solids content of desirably not more than 2% or, at the most, 3% by weight) rather than to thick stock. Thus, the flocculant may be added directly to the thin stock or it may be added to the dilution water that is used to convert thick stock to thin stock. The high molecular weight flocculant polymer comprises an agent for aggregating the solids, especially the fines, in the paper making furnish. As used herein, "fines" means fine solid particles and fibers as defined in TAPPI Test Methods T261 and T269. Flocculation of the fines of the furnish may be brought about by the high molecular weight polymer itself or by the high molecular weight polymer in combination with another agent, e.g., high charge density cationic coagulant. Flocculation of fines gives better retention of the fines in the fiber structure of the forming paper sheet, thereby giving improved dewatering or drainage. The high molecular weight polymer flocculant is a polymer providing flocculant action preferably by itself. Examples of high molecular weight polymer flocculants suitable for use herein are those having a weight average molecular weight of about 100,000 or more, especially 500,000 or more. Preferably, the molecular weight is about above 1 million and often above about 5 million, for instance in the range 10 to 30 million or more. These polymers may be linear, branched, cationic, anionic, nonionic, amphoteric, or hydrophobically modified polymers of acrylamide or other nonionic monomers. The amounts of high molecular weight polymer flocculant of the microparticle system- added to the stock or furnish in the present invention may be any amount sufficient to give a substantial effect in flocculating the solids, especially the fines, which are present in the stock or furnish. The total amount of water soluble polymer added may be in the range of about 0.0025 wt . % to about 1.0 wt . %, more preferably in the range 0.01 wt . % to 0.2 wt . %, and most preferably in the range of about 0.025 wt. % to about 0.1 wt . % by weight (dry weight of polymer based on the dry weight of the solids present in the stock or furnish) . The addition may be carried out in one or more doses at one or more addition sites and, preferably, is carried out in one dose to the thin stock flow after the fan pump which causes a high shear action. Desirably, the floes formed by the high molecular weight polymer flocculant are subjected to a shearing action before addition of the inorganic particulate material of the microparticle system. Preferably, this shearing action is induced by a pressure screen which causes a high shear action. The amount of inorganic particulate material of the microparticle system added to the stock or furnish in the method according to the present invention may be in the range of about 0.005% to about 2.0%, and preferably in the range of about 0.05% to about 0.5% by dry weight (based on the dry weight of solids present) . The addition may be carried out in one or more doses at one or more addition sites, but preferably in one dose, and preferably after the pressure screen 2 in Figure 1, and at least between pressure screen 2 and headbox 3. The inorganic particulate material of the microparticle system of the invention preferably is saponite which is ; an aluminum substituted trioctahedral mineral . In the patent literature relating , to retention, drainage and sheet formation, there is mentioned a wide variety of clay minerals which are included under the broad heading of "bentonite" or "swelling clays" or merely "microparticles" . Clay mineralogy is a complex field, and, as stated hereinabove, the terminology has often been used loosely. The aforesaid U.S. Patent No. 5,178,730 discusses this issue in column 4, lines 14-32 which includes the following: "For example, U.S. Patent No. 4,753,710 describes bentonite and bentonite-type clays as anionic swelling clays such as sepiolite, attapulgite, or preferably, montmorillonite . This patent also references the broader bentonite description in U.S. Patent No. 4,305,781 (commercial bentonites, montmorillonite clays, Wyoming bentonite and Fullers Earth). U.S. Patent No. 4,749,444 describes bentonites as sheet silicates which are water swellable including nontronite, hectorite, saponite, volkonskoite, sauconite, beidellite, allevanite, illite, halloysite, attapulgite and sepiolite. It is generally accepted in current clay mineralogy texts that many of these minerals are not normally found in bentonite and should not be classified with it, e.g., several of them are not in the smectite group (allevarite, illite, halloysite, attapulgite, and sepiolite) and a few of them do not swell (illite, attapulgite, and sepiolite)." In this aforesaid U.S. Patent No. 5,178,730, a true "bentonite" had been referred to as a "dioctahedral" smectite, and a true "hectorite" as a trioctahedral" smectite which includes naturally occurring clays thereof . The smectite family of clay minerals generally is a three layer mineral containing a central layer of alumina or magnesia octahedral sandwiched between two layers of silica tetrahedral. If the central octahedral layer comprises aluminum ions, then the smectite clay is referred to as a "di-octahedral" mineral. If the central octahedral layer comprises magnesium ions, then the smectite clay is referred to as a "trioctahedral" mineral. The smectite clay minerals are differentiated in structure and chemical composition by what is referred to as "isomorphous substitution" in which a certain percentage of silicon atoms in the two outer tetrahedral layers and/or a certain percentage of aluminum or magnesium atoms in the central octahedral layer are replaced by different atoms. The "base mineral" for the dioctahedral subclass is pyrophyllite which has no isomorphous substitution in either the octahedral or tetrahedral layer. As a consequence of having no interlayer cations or water, pyrophyllite does not swell. Montmorillonite, volchonskoite, beidellite, and nontronite fall under this pyrophyllite subclass with differing substitutions in the three layers. For instance, montmorillonite is characterized by having some substitution of aluminum by magnesium in the octahedral layer (typically around 15-20% by number of atoms) . Beidellite has some substitution of silicon by aluminum in the tetrahedral layer. Bentonite (Wyoming clay, Fullers Earth) is a rock type formed usually by weathering of volcanic ash which primarily contains montmorillonite and often some beidellite. Nontronite has essentially complete substitution of aluminum by iron in the octahedral layer, and also some substitution of silicon by aluminum in the tetrahedral layer. Volchonskoite is similar to nontronite, but contains chromium in the octahedral layer rather than iron. The bentonite of most of the prior art literature is this type of smectite clay, i.e., falling generally under montmorillonite . The "base mineral" for the trioctahedral subclass, containing no isomorphous substitution in either the central octahedral layer or the outer tetrahedral layers is talc, and as pyrophyllite shows no swelling behavior. Hectorite, saponite, sauconite, and oftentimes vermiculite fall under the trioctahedral subclass. Hectorite generally has some substitution of magnesium by lithium in the central octahedral layer. Saponite has some substitution of magnesium by aluminum in the central octahedral layer and also some substitution of silicon by aluminum in the outer tetrahedral layer. In sauconite, the predominant atom in the central octahedral layer is zinc rather than magnesium, with some of the zinc atoms replaced by aluminum and some of the silicon atoms in the outer tetrahedral layers substituted by aluminum. Vermiculite has a high degree of substitution of silicon by aluminum or iron with magnesium cations between the layers whereas most of the other naturally occurring smectites, such as those above have either calcium or sodium cations between the layers. As used herein, the term "saponite" is a trioctahedral clay mineral having an aluminum substitution in the central octahedral layer and in the outer tetrahedral layers. Preferably, saponite is the inorganic particulate material of the microparticle system of the present invention. However, it is to be understood that the other aluminum substituted trioctahedral clay minerals such as sauconite and vermiculite can also be used. These trioctahedral minerals are distinguished from hectorites of the prior art in that hectorite contains a lithium substitution in the central octahedral layer and are distinguished from montormillonite, e.g., bentonite of the prior art in that montmorillonite is a dioctahedral mineral with magnesium substitution in the central octahedral layer. The addition of the high molecular weight flocculant polymer generally will cause the formation of large floes of the suspended solids in the stock or furnish to which the polymer is added. These large floes are immediately or subsequently broken down by high shear to very small floes that are known in the art as "microfIocs" . This "high shear" may be induced by passing the flocced furnish through the pressure screen 2 of Figure 1. Still referring to Figure 1, a water soluble polymer generally lower in molecular weight than the flocculant may be employed as a coagulant by addition to the thick stock and preferably is added to the stock prior to the stock passing through fan pump 1. This coagulant, preferably, is a high charge density cationic polymer. For instance, if the coagulant polymer is a nitrogen containing cationic polymer, it may have a charge density of above 0.2, preferably, at least 0.35 and, most preferably, 0.4 to 2.5 or more, equivalents of nitrogen per kilogram of polymer. When the polymer is formed by polymerization of cationic, ethylenically unsaturated, monomer optionally with other monomers, the amount of cationic monomer will normally be above 2 mole % and usually above 5 mole % and preferably at least about 10 mole % based on the total amount of monomers used for forming the polymer. Suitable cationic coagulants include: inorganic aluminum salts, polyaluminum chlorides (PAC) , polydiallyldimethyl ammonium chloride (p-DADMAC) ; polyalkylamines; cationic polymers of epichlorohydrin with dimethylamine and/or ammonia or other primary and secondary amines; polyamidoamines; copolymers of a nonionic monomer, such as acrylamide, with a cationic monomer, such as DADMAC or acryloyloxyethyltrimethyl ammonium chloride; cyanoguanidine modified polymers of urea/formaldehyde resins; melamine/formaldehyde polymers; urea/formaldehyde polymers; polyethylene imines; cationic starches; amphoteric polymers possessing a net cationic charge; and blends of the aforementioned coagulants. The amounts of cationic coagulant polymer of the microparticle system of the invention added to the stock or furnish may be any amount sufficient to give a substantial effect in coagulating the solids present in the stock or furnish. The total amount of water soluble coagulant polymer may be in the range of about 0.0025 wt . % to 1.0 wt. %, more preferably in the range of about 0.005 wt . % to about 0.50 wt. % (dry weight based on the dry weight of the solids present in the stock or furnish) . As mentioned hereinabove, a cationic coagulant may be added to the thick stock prior to the fan pump 1, the high molecular weight flocculant polymer may be added to the thin stock after the stock's passage through fan pump 1, and the inorganic particulate material may be added to the thin stock after the stock's passage through pressure screen 2. The initial thick stock can be made from any conventional paper making stock such as traditional chemical pulps, for instance bleached and unbleached sulphate or sulphite pulp, mechanical pumps such as groundwood, thermomechanical or chemi-thermochemical pulp or recycled pulp such as deinked waste, fiber filler composites from aggregating or recycling processes and any mixtures thereof. The stock employed in the method of the invention, and the final paper, can be substantially unfilled (e.g., containing less than 10% and generally less than 5% by weight filler in the final paper) or filler can be provided in an amount of up to 50% based on the dry weight of the solids of the stock or up to 40% based on the dry weight of paper. When filler is used, any conventional white pigment filler such as calcium carbonate, kaolin clay, calcined kaolin, titanium dioxide or talc, or a combination thereof may be present. The filler (if present) is preferably incorporated into the stock in a conventional manner, and before addition of the components of the microparticle system. The stock employed in the method of the invention may include other known optional additives, such as, rosin, alum, neutral sizes or optical brightening agents. It may include a strengthening or binding agent and this can, for example, comprise a starch, such as cationic starch. The pH of the stock is generally in the range 4 to 9 and a particular advantage of the method of the invention is that it functions effectively at low pH values, for instance, below pH 7. The amounts of fiber, filler, and other additives, such as, strengthening agents or alum can all be conventional. Typically, the thin stock has a solids content of 0.1% to 3% by weight or a fiber content of 0.1% to 2% by weight. The thin stock will usually have a solids content of from 0.1% to 2% by weight. The inorganic particulate material employed in the microparticle system of the invention includes a trioctahedral aluminum containing clay material selected from the group consisting of saponite, sauconite, and vermiculite, and preferably, saponite. These particles are readily dispersed in an aqueous pulp suspension in a paper making process to enhance the surface characteristics of the final paper product. These particles, in general, will have an average dry particle size less than 80 μm, typically in the range 1 μm to 10 μm, and more typically from 2 nm to 2 μm, preferably from 1 nm to 1.2 μm. Particles having an average size of less than 1 μm, which may exist in that size before addition to the stock or may be broken down to that size after addition to the stock are preferred. A conventional dispersing agent, e.g., a water soluble anionic polymer, such as an acid polymer containing acrylic or methacrylic groups of a salt thereof, may be employed in a conventional manner, e.g., by addition of from about 0.1% to about 3% by weight of dispersing agent based on the dry weight of the inorganic particulate material, to ensure that the appropriate fine particle size is achieved. We have found that saponite (Nao.g [Mg 6 . 0 ] ) (Si .ι AI 0 . 9 ) 0 20 (OH 4 ) in conjunction with a flocculant or a flocculant/coagulant system can increase drainage and retention, and improve sheet formation in the paper making process. Two sets of lab experiments were performed. The first set employed a flocculant and saponite at the feed points indicated in Figure 1 to obtain drainage and retention results. The second set employed both a flocculant and saponite added to the thin stock at the feed points shown in Figure 1 and a flocculant, a coagulant, and saponite at the feed points shown in Figure 1 to obtain drainage, retention and sheet formation results. The following examples demonstrate the invention in greater detail. These examples are not intended to limit the scope of the invention. Experiments - Set No.- i In the examples for set No. 1, the following products were used: Hydrocol 875 is a high molecular weight cationic polyacrylamide polymer flocculant available from Allied Colloids, Ltd. Imvite 1016 is a dry saponite clay available from IMV Nevada, Amargosa Valley, NV. SMI 200 H-200 mesh is a ground dry saponite clay available from GSA Resources, Inc., Tucson, Arizona. Acme Clay is kaolin clay available from ECC International Inc., Roswell, Georgia. Example 1 Pulp Slurry An alkaline paper furnish was prepared. The furnish consisted of a blend containing 80% Weyerhauser, Prince Albert HW pulp and 20% of repulped Georgia Spectrum DP (Xerox grade) . The furnish was beaten with a laboratory scale Voith Allis Valley Beater to a Canadian Standard Freeness (CSF) of 250 ml and diluted to a consistency of 0.5 wt . % solids. The pH of the slurry was kept at around 7.8. Two batches of this furnish were made. To the first batch of furnish, 5 wt . %, based on the weight percent consistency of pulp slurry, of Acme Clay was added as a filler. To the second batch of furnish, 20 wt . %, based on the weight percent consistency of the pulp slurry, of Acme Clay was added as a filler. Makedown Of Reagents Preparation Of Water Soluble Polymer Using a magnetic stirrer, the Hydrocol 875 polymer was first made down to 1.0 ■ wt . % headbox consistency in deionized water and then made down to 0.1 wt . %, based on the amount of the' deionized water, for final use in the two batches of pulp slurry in the drainage and retention testing procedures herein. Preparation Of The Saponite Samples Two samples of saponite were used during the course of these Examples for set No. 1. The SMI 200 H-200 mesh saponite was identified as Sample 1 and the Imvite 1016 saponite was identified as Sample 2. Five grams of each saponite Samples 1 and 2 were made down with 100 ml of deionized water and mixed in a Hamilton Beach mixer for 15 minutes and then diluted to 1000 ml with deionized water. Both Sample 1 and Sample 2 were mixed for another 15 minutes with a magnetic stirrer and allowed to hydrate for a minimum of 16 hours. Each Sample 1 and Sample 2 was mixed before being added to the pulp slurry as described hereinafter. Drainage Testing A one liter aliquot of each of the first and second batches of pulp slurry containing the 5 wt . % Acme Clay Filler and the 20 wt. % Acme Clay Filler, respectively was mixed in a square jar using a Lightning mixer. The mixer speed was kept constant for 10 seconds at 1500 rpm (shear mixing) . These two batches of pulp slurry were then dosed with the above polymer solution and stirred at 1500 rpm for an additional minute. The mixer was turned off and the slurries were allowed to stand for three minutes . Saponite Sample 1 was added to the first batch of furnish containing the 5 wt . % kaolin clay filler and to the second batch of furnish containing the 20 wt. % clay filler and saponite Sample 2 was added to the second batch of furnish containing the 20 wt. % kaolin clay filler. The resultant pulp slurries comprising the saponite, the filler, and the polymer were poured back and forth between two beakers five times. The resultant pulp slurry was then poured into a drainage jar which was then shaken three times before the pulp ' slurry was drained. The drainage water was collected for 30 seconds and then weighed using a tarred beaker. Drainage testing for these resultant pulp slurries was performed and plotted in Figures 2-4. Retention Testing Turbidity Turbidity of the drainage water can be a measurement of the filler and fines retention of the system. 240 ml of a batch of furnish containing 5 wt . % kaolin clay filler were mixed at 1500 rpm (shearing mixing) . The batch of furnish, while being stirred, was dosed with 6 lbs. dry polymer per ton of dry furnish, and mixed for 15 seconds. Turbidity of the drainage water for the furnish containing the polymer solution and 5 wt . % filler was determined and plotted in Figure 5 as Sample 3. Saponite Sample 1 was then added to the f rnish at a dosage of 12 lbs. dry saponite per ton of dry furnish. The resultant pulp slurry was mixed for an additional 5 seconds. Turbidity of this furnish was determined and plotted in Figure 5 as Sample 4. The turbidity testing was performed using a Hach 2100P Turbidimeter. Hand Sheets Another 240 ml of furnish containing the 5 wt . % kaolin clay filler were dosed with the polymer solution prepared hereinabove. Doses of the saponite solution slurry of Sample 1 was added to the furnish and mixed at 1500 rpm for an additional 5 seconds. These dosages are shown in Table 1 where the dosages are 6 lbs. of dry polymer per ton of dry furnish and 0, 6, and 12 lbs. of dry saponite, respectively, per ton of dry furnish. TABLE 1 Hand sheets were made using the standard TAPPI mold and standard hand-making paper sheet procedure. The paper sheets were made and ashed at 500°C. Pulp pads were also made using a porcelain Buchner Filter Funnel from Coors Company, U.S.A., and equipped with a Whatman 41 Ashless Filter Paper. Drainage Results The drainage data obtained from the first batch of furnish containing 5% kaolin clay filler is plotted in a three dimensional surface graph of Figure 2 showing drainage vs. polymer dosage vs. saponite (Sample 1) . The polymer dosage was varied from 1.2 lbs. of dry polymer/ton of dry furnish to 6.0 lbs. of dry polymer/ton of dry furnish, and the saponite (Sample 1) dosage was varied from 0 to 18 lbs. of dry saponite/ton of dry furnish. From the graph of Figure 2, it can be seen that the drainage in ml increased as the dosages of polymer and saponite increased. Second Batch Furnish-20% Clay Filler - Saponite Sample 1 Figure 3 illustrates the data for saponite Sample 1 where drainage vs . polymer dosage vs . saponite dosage for the furnish containing 20% clay filler is plotted. Second Batch Furnish-20% Clay Fillers - Saponite Sample 2 Figure 4 illustrates the data for saponite Sample 2 where drainage vs . polymer dosage vs . saponite dosage for the furnish containing 20% clay filler is plotted. For both Figures 3 and 4, the saponite dosages ranged from 0 to 24 lbs. of dry saponite/ton of dry furnish and the polymer dosages ranged from 2.4 to 6.0 lbs. of dry polymer/ton of dry furnish'. Here again, a drainage increase was observed as the polymer and saponite dosages were increased. Retention Results Turbidity can be a measurement of retention. The higher turbidity indicates more fines and fillers in the drainage water and, therefore, less retention of the fines and fillers in the paper. The results are plotted in Figure 5 for Samples 3 and 4, discussed hereinabove. From the results plotted in Figure 5, it can be seen that the turbidity of Sample 4 containing the saponite and polymer is considerably lower than Sample 3 without saponite, which means that the retention of the fillers and fines is greater with Sample 4 containing the polymer and saponite. Hand Sheets The results of these experiments are given in Table 1. The filler retention values given were determined by ashing the handsheets at 500°C. Again, it can be seen in Table 1 that an increase in the filler retention occurs when the saponite is added to the furnish. As this first set of experiments indicate, the drainage and retention of fines and filler may be increased by the use of a two-component microparticle system, namely saponite and a flocculant polymer. Set No. 2 Experiments This set of experiments indicates that the drainage and retention of fines and fillers may be increased with either a two or a three component microparticle system comprising saponite and a polymer flocculant, and optionally, a coagulant. Examples The following examples demonstrate the invention in greater detail. These examples are not intended to limit the scope of the invention in any way.' In these examples the following products were used: Polymer A is a high molecular weight, cationic, acrylamide / acryloyloxyethyltrimethylammonium chloride copolymer available from Calgon Corp. (Pittsburgh, PA), comprising about 90 mole % acrylamide and about 10 mole % acryloyloxyethyltrimethylammonium chloride . Polymer B is a medium molecular weight homopolymer of diallyldimethylammonium chloride available from Calgon Corp. (Pittsburgh, PA) . Polymer C is a high molecular weight, cationic acrylamide copolymer, comprising about 25 wt. % cationic charge, available from Ciba Specialty Chemicals. Hydrocol 2D1 is a dry bentonite clay, i.e. montmorillonite, available from Ciba Specialty Chemicals. Polymer D is a medium molecular weight, dimethylamine / epichlorohydrin cationic polymer available from Calgon Corp. (Pittsburgh, PA) . Polymer E is a high molecular weight, anionic acrylamide copolymer, available from Calgon Corp. (Pittsburgh, PA), comprising about 70 mole % acrylamide and about 30 mole % acrylic acid. Polymer F is a polyaluminum chloride available from ECC International (Pittsburgh, PA) Polymer G is a medium molecular weight, cationic copolymer of acrylamide and diallyldimethylammonium chloride available from ECC International (Pittsburgh, PA) . Polymer H is a medium molecular weight, terpolymer of acrylamide, diallydimethylammonium chloride, and acrylic acid available from ECC International (Pittsburgh, PA) . IMVITE 1016 is a dry saponite clay available from IMV Nevada, Amargosa Valley, NV. Carbital 60 is a dry, ground calcium carbonate available from ECC International, Atlanta, GA. Stalok 400 and Interbond C are cationic starches available from A.E. Staley. Hereon 70 is an AKD size available from Hercules Inc. Examples 1 - 26 Examples 1-26 demonstrate the effectiveness of various formulations of the instant invention in improving drainage, retentions, and various sheet properties, including formation, brightness, and opacity, of a synthetic, aqueous cellulosic furnish. The composition of this furnish was designed to mimic a typical alkaline, wood-free furnish used to manufacture base sheet for coated and uncoated magazine or printing and writing grades . Furnish Preparation The synthetic furnish used for drainage and retention tests and for making handsheets was prepared with the following components: Fiber: 50/50 wt . % bleached hardwood kraft/bleached softwood kraft Filler: 50/50 wt . % ground calcium carbonate (Carbital 60) /precipitated calcium carbonate . Filler loading: 20 wt. % based on fiber solids Starch: 0.5 wt . % (Interbond C) based on fiber solids Size: 0.25 wt. % Hereon 70 (AKD) The dry lap pulp is soaked in tepid water for 10 minutes and then diluted to 2 wt . % solids in water and refined with a laboratory scale Valley Beater to a Canadian Standard Freeness of 590 ml. The starch, size, and fillers, are added in that order to the refined pulp slurry. The pH of the pulp slurry is typically 7.5 + 0.3. The pulp slurry is diluted further with tap water to approximately 1.0 wt . % consistency to form thin stock for testing. Drainage Test Procedure 1. Pour 200 ml (2g solids) of stock at 1 wt . % headbox consistency into a square mixing jar and dilute to 500 ml with tap water. 2. Mix the contents using a standard Britt Jar style propeller mixer (1 inch diameter) under the following mixing time and speed conditions to simulate chemical addition to the secondary fan pump inlet, fan pump outlet, and pressure screen outlet: Time Speed (rpm) Additive Feed Point to 1200 Coagulant Pre-fan tio 1200 Flocculant Pre-screen t 20 600 D/R/F aid Post-screen t 30 stop 3. Transfer the contents of the mixing jar to a 500 ml graduated drainage tube fitted on the bottom with a 100 mesh screen. Invert the tube 5 times to ensure the stock is homogenous. Remove the bottom stopper and measure elution times for 100, 200, and 300 ml elution volumes. The elution time at 300 ml for an untreated stock blank should be preferably >60 seconds. 4. The improvement in drainage provided by a treatment was calculated as follows based on the drainage time for an untreated, blank sample: % Drainage Improvement = ( Drain time with no treatment - Drain time with treatment ) x 100 Drain time with no treatment Retention Test Procedure (FPR, FPAR, FPFR) 1. Pour 500 ml of stock at- headbox consistency (1.0%) into a Britt Jar with a . 70 mesh screen while stirring at 1200 rpm. 2. Use the same mixing time / speed sequence as that used in the drainage test procedure to simulate chemical addition points and add the following steps: Time Speed (rpm) Additive Feed Point to 1200 Coagulant Pre-fan tio 1200 Flocculant Pre-screen t 20 600 D/R/F aid Post-screen t 0 open the bottom stop cock and collect the first 100 ml of eluate a. Filter this eluate through Whatman 4 filter paper and dry the pad at 105°C. Burn the pad at 500°C for 2 hours to determine ash retention. Hand Sheet Preparation and Testing Handsheets were prepared at 70 gs basis weight using a Noble & Wood Hand Sheet Mold. This apparatus generates a 20cm x 20 cm square handsheet . The mixing time / speed sequence used in preparing handsheets is the same as the sequence used for the drainage test procedure. The treated furnish sample is poured into the deckle box of the Noble & Wood handsheet machine and the sheet is prepared employing standard techniques well known by those skilled in the art. The results are shown in Table 2 E-0031 TABLE 2 r>o CO Examples 5-8, plotted in Figure 6, show that the simulated addition of Polymer A before the pressure screen and saponite after the pressure screen at dosages ranging from 3-9 lb/ton leads to significant increases in stock drainage with only minor losses in sheet formation. First pass ash retention (FPAR) increases to a maximum at 3 lb/ton saponite and decreases at higher dosages. Examples 9-12, plotted in Figure 7, show that the addition of a third component, a cationic coagulant Polymer B, selectively improves first pass ash retention (FPAR) and with little change in drainage and sheet formation up to a dosage of 0.1 lb active / ton. At higher dosages, FPAR continues to increase while drainage decreases slightly and sheet formation drops off sharply. In the absence of saponite, as shown in examples 14, 17, and 23-26, drainage and retentions are significantly lower . Tables 3 and 4 represent results for Examples 27-50. Table 3 Examples 27-50 of Table 3 compare the drainage performance of the present invention (examples 28-32) with a conventional dual polymer program (examples 46-50) and colloidal silica (examples 38-42 and 43-45) and bentonite (examples 33-37) microparticle programs. At roughly equivalent levels of drainage performance for each of these programs (examples 29, 37, 40, 45, and 47) a much lower total dosage of the present invention (example 29) is needed to match drainage performance of the prior art examples. Also, as shown in Table 4, first pass ash retention is higher for the present invention than the prior art at comparable sheet formation values . Table 4 Examples 51 - 77 Examples 51- 77 of Table 5, demonstrate the effectiveness of various formulations of the instant invention in improving drainage, retentions, and various sheet properties, including formation, brightness, and opacity, of a synthetic aqueous furnish. The composition of this furnish represents a typical furnish used to manufacture the base sheet for lightweight coated grades. Furnish Preparation The synthetic furnish used for drainage and retention tests and for making hand sheets was prepared with the following components: Fiber: 45 wt. % bleached softwood kraft (SWK) /55 wt. % chemi- thermomechanical pulp (CTMP) Filler: Calcined clay Filler loading: 10 wt. % based on oven dry fiber weight Alum: 0.5 wt . % based on oven dry fiber weight The CTMP was soaked in hot water for 15-20 minutes and then diluted to 1.56 wt . % solids in water and refined to a Canadian Standard Freeness (CSF) of 200 ml. The kraft softwood fiber (SWK) was soaked separately in water, diluted to 1.56 wt . %, and refined to 550 CSF. The fibers were then blended to the proportions listed above with the calcined clay filler. The pH of the combined furnish was adjusted to 5.0 with dilute sulfuric acid and the conductivity was adjusted to 2000 μS/cm with sodium sulfate . Table 5 Examples 78 - 110 Examples 78 - 110 of Table 6 demonstrate the effectiveness of various formulations of the instant invention in improving drainage, retentions, and sheet formation of a synthetic aqueous furnish. The composition of this furnish represents a typical furnish used in the manufacture of the base sheet for paperboard. At roughly equivalent drainage performance, the present invention provides significant improvements in first pass ash retention and sheet formation over the prior art. Furnish Preparation The synthetic furnish used for drainage and retention tests and for making hand sheets was prepared using the following procedure. Disintegrate 360 grams of unbleached, old corrugated cardboard (OCC) in tepid water and dilute to 23 liters with deionized water. Refine the pulp to 300 CSF. Dilute 18 liters of this stock to 0.5 wt . % consistency and add the following salts and amounts to adjust the water chemistry to the proper ionic strength (2000 μS/cm) : a. 5.61 grams Calcium chloride b. 0.96 grams Potassium chloride c. 8.17 grams Alum (50 wt. %) d. 15.96 grams Sodium sulfate e. 0.59 grams Sodium bicarbonate f. 0.97 grams Sodium silicate Adjust the pH to 5.0 with dilute sulfuric acid. Table 6 Examples 111 - 118 of Table 7 compare the performance of the present invention in a 100% OCC paperboard furnish with bentonite and colloidal silica programs of the prior art. At equivalent drainage, the present program provides significant improvements in ash retention, total retention, and sheet formation (MK) . Table 7 Examples 119 - 145 Examples 119 - 145 of Table 8 demonstrate the effectiveness of various formulations in improving drainage, retentions, and various sheet properties, including formation, brightness, and opacity, of a synthetic aqueous furnish. The composition of this furnish represents a typical groundwood furnish used to manufacture the base sheet for newsprint. Furnish Preparation The synthetic furnish used for drainage and retention tests and for making hand sheets was prepared using the following recipe and procedure. Fiber: 80 wt . % CTMP/10 wt . % SWK/10 wt . % recycled newsprint Filler: Calcined clay Filler loading: 4 wt . % based on oven dry solids Alum: 50 lb/ton pH: 4.8 - 5.2 Soak the CTMP in hot water (140°F) and defiber in a blender for 15-20 minutes. The recycle newsprint was soaked separately in hot water and then defibered in a blender for 15-20 minutes. The kraft softwood was soaked for two hours in tepid water and defibered in a blender for 15-20 minutes. The CTMP, recycle newsprint, and kraft softwood were blended together in the proportion described above and refined at 1.56 wt . % consistency to 50 - 75 CSF. The calcined clay filler and then alum were added to the stock to give a pH of about 4.8 - 5.2. The conductivity of the stock was adjusted to 2000 μS/cm using sodium chloride . Table 8 Examples 146 - 150 of Table 9 compare the performance of the present invention to the prior art at roughly equivalent drainage and at maximum drainage for a typical newsprint furnish. As shown in Table 9 the present invention provides significantly higher maximum stock drainage and significant improvements at equivalent drainage in sheet formation (MK) and sheet brightness at significantly lower product dosages than the prior art. Table 9 Example 151 Commercial Machine Applications Light Weight Coated Papers The performance of the instant invention was evaluated on a commercial paper machine producing 60 lb / 3300 ft 2 light weight coated, wood-containing paper and compared to a commercial, colloidal silica based program typical of the prior art. For this evaluation, Polymer A was fed at 0.2 lb dry polymer / dry ton of paper to the inlet of the pressure screen and saponite clay was fed at 4 lb / ton of dry paper to the outlet of the pressure screen. As shown in Table 10, the instant invention gave significant improvements in steam usage, sheet formation, and first pass retention at equivalent machine speed. Variability in retention control and cross directional sheet moisture were also significantly reduced with the instant invention. Table 10 The effectiveness of the instant invention was also demonstrated on another commercial paper machine producing 40 lb / 3300 ft 2 light weight coated, wood- containing paper and compared to a commercial, colloidal silica based program typical of the prior art. For this evaluation, Polymer A was fed at 0.25 lb dry polymer / dry ton of paper to the inlet of the pressure screen and saponite clay was fed at 4 lb / ton of dry paper to the outlet of the pressure screen. As shown in Table 11, the instant invention gave significant improvements in steam usage, sheet formation, headbox ash consistency, and sheet brightness. Table 11 Example 152 Commercial Machine Application - Linerboard The performance of the present invention was evaluated on a commercial paper machine producing two ply linerboard grades . Polymer A was fed to the inlet of the pressure screen at dosages between 0.2 and 0.75 lb product per dry ton of paper. Saponite was fed to the discharge side of the pressure screen at dosages between 3 and 7 lb product per dry ton. First pass retention (FPR) increased from 63 to 86% and first pass ash retention (FPAR) increased from 10 to 50%. Thick stock flow decreased 10-17% and clear and cloudy leg save all solids were reduced by 50%. "MK Formation" discussed hereinabove represents sheet formation measured by a M/K Formation Tester. Whereas particular embodiments of the present invention have been described for purposes of illustration, it will be evident to those skilled in the art that numerous variations and details of the invention may be made without departing from the invention as defined in the appended claims.

Claims: WHAT IS CLAIMED IS: 1. A paper product furnish containing a retention and drainage aid composition, comprising: a high molecular weight polymer flocculant being present in an amount of from about 0.0025 % to about 1.0% by weight based on the dry weight of the solids in said furnish, and an inorganic particulate material comprising an aluminum substituted trioctahedral clay mineral being present in an amount of from about 0.005% to about 2.0% by weight based on the dry weight of the solids in said furnish. 2. A paper product furnish of Claim 1 further comprising: a high charge density cationic coagulant being present in an amount of from about 0.0025% to about 0.5% by weight based on the dry weight of the solids in said furnish. 3. A paper product furnish of Claim 1 wherein said aluminum substituted trioctahedral clay mineral is selected from the group consisting of saponite, sauconite, and vermiculite. 4. A paper product furnish of Claim 3 wherein said aluminum substituted trioctahedral clay mineral is saponite. 5. A method for producing a paper product, the steps comprising : after a first high shearing stage and prior to a second high shearing stage, adding a high molecular weight polymer flocculant to the furnish in an amount of from about 0.0025% to about 1.0% by weight based on the dry weight of the solids in the furnish; and after said second high shearing stage, adding an inorganic particulate material comprising an aluminum substituted trioctahedral clay mineral to the furnish in an amount of from about 0.005% to about 2.0% by weight based on the dry weight of the solids in said furnish. 6. A process of Claim 5 further comprising: prior to said first high shearing stage, adding a high charge density cationic coagulant to the furnish in an amount of about 0.0025% to about 0.5% by weight based on the dry weight of the solids in said furnish. 7. A process of Claim 5 wherein said aluminum substituted trioctahedral clay mineral is selected from the group consisting of saponite, sauconite, and vermiculite . 8. A process of Claim 7 wherein said aluminum substituted trioctahedral clay mineral is saponite. 9. A microparticle composition suitable for use as a retention and drainage agent in paper making process comprising a high molecular weight polymer flocculant, and an inorganic particulate material comprising an aluminum substituted trioctahedral clay mineral. 10. A composition of Claim 9 further comprising a high charge density cationic coagulant. 11. A composition of Claim 9 wherein said aluminum substituted trioctahedral clay mineral is selected from the group consisting of saponite, sauconite, and vermiculite. 12. A composition of Claim 11 wherein said aluminum substituted trioctahedral clay mineral is saponite.

Inventors: PANFIL DANIEL J, RODRIGUEZ JOSE M, VAUGHAN CRAIG W, PANFIL, DANIEL, J., RODRIGUEZ, JOSE, M., VAUGHAN, CRAIG, W.
Applicants: ECC INT INC, PANFIL DANIEL J, RODRIGUEZ JOSE M, VAUGHAN CRAIG W, ECC INTERNATIONAL INC., PANFIL, DANIEL, J., RODRIGUEZ, JOSE, M., VAUGHAN, CRAIG, W.
Application year: 1999
Main classification: D21H21
IPC codes: D21H11, D21H17, D21H21, D21H23