JP2015533392A - Pre-agglomeration of fillers used in papermaking - Google Patents

Abstract

A method for preparing a stable dispersion of agglomerated filler particles for use in a papermaking process includes the step of adding, before, simultaneously and / or after adding the microparticles to the aqueous dispersion of filler particles. Use, followed by the addition of a second flocculant to the dispersion, optionally shearing the resulting filler floc further to the desired particle size to have a shear-resistant packing with limited controllable size distribution Generating an agent floc. In addition, prior to the addition of the particulates and / or the first flocculant, a neutralizing coagulant can be added to the dispersion to partially or fully neutralize the charge on the filler.

Description

  The present invention relates to the pre-agglomeration of fillers used in papermaking, and in particular, the production of shear resistant filler flocs having a limited and controllable size distribution in high filler solids.

  Increasing filler content in printing and writing papers is of great concern for improving product quality and reducing raw material and energy costs. However, replacing the cellulose fibers with fillers such as calcium carbonate and clay reduces the strength of the finished sheet. Yet another problem with increasing filler content is the difficulty of maintaining a uniform distribution of filler throughout the three-dimensional sheet structure. An approach to reduce these undesirable effects of increasing filler content is to preaggregate the fillers before adding them to the wet end approach system of the papermaking machine.

  The definition of the term “pre-agglomeration” is that the filler particles are transformed into agglomerates by treatment with a coagulant and / or flocculant before they are agglomerated and added to the papermaking stock. The shearing force of the agglomeration process and process determines the size distribution and stability of the floc before addition to the papermaking stock. The chemical environment and high fluid shear rates present in modern high speed papermaking require that the filler floc be stable and shear resistant. The floc size distribution provided by the pre-agglomeration process minimizes the decrease in sheet strength with increased filler content and minimizes the decrease in optical efficiency due to filler particles to ensure sheet uniformity and printing. It should minimize adverse effects on sex. In addition, the entire system must be economically feasible.

US Pat. No. 8,172,983

  Therefore, the combination of high shear stability and narrow particle size distribution is essential to the success of the filler pre-agglomeration technique. However, filler flocs formed only by low molecular weight coagulants, including commonly used starches, tend to have relatively small particle sizes that disintegrate under the high shear forces of paper machines. Filler flocs formed by a single high molecular weight flocculant tend to have a broad particle size distribution that is difficult to control, mainly due to poor mixing of the viscous flocculant solution into the slurry. The particle size distribution gets worse as the filler solids level increases. Thus, there remains a need for improved pre-aggregation techniques.

  The technology described in this section is not intended to constitute an admission that any patent, publication or other information cited herein is “prior art” to the present invention, unless otherwise specified. In addition, this section contains information on whether a survey was conducted or 37C. F. R. It should not be construed to mean that there is no other directly related information specified in §1.56 (a).

  At least one embodiment is directed to a method of preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process. The method comprises: a) providing an aqueous dispersion of filler particles; b) mixing the first flocculant uniformly in the dispersion without causing significant aggregation of the filler particles. Adding to the dispersion in an amount sufficient for the first flocculating agent to be amphoteric; c) the microparticles before, simultaneously with and / or after the addition of the first flocculating agent; As well as before the second flocculating agent, adding to the dispersion in an amount insufficient to cause significant flocculation of the filler particles; d) in the presence of the first flocculating agent, Adding a second flocculant to the dispersion in an amount sufficient to initiate agglomeration of the filler particles, wherein the second flocculant is the net charge of the amphoteric first flocculant and A step having the opposite charge; e) shearing the agglomerated dispersion to a desired particle size. Steps and to provide a dispersion of the agent floc; After f) papermaking raw materials were aggregated filler particles in the absence, and a step of adding them to the paper stock.

  The filler floc may have a median particle size of 10-100 μm. The filler can be selected from the group consisting of precipitated calcium carbonate, heavy calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate and magnesium hydroxide, and mixtures thereof. The first flocculant may have a net anionic charge. The second flocculant may be cationic and / or (meth) acrylamide and dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl It may be selected from the group consisting of copolymers and terpolymers with methacrylate (DEAEM) or their quaternary ammonium form (formed using dimethyl sulfate, methyl chloride or benzyl chloride) and mixtures thereof. The second flocculating agent may be an acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10-50 mole percent and an RSV of at least 15 dL / g, and / or 0.1 It may be a homopolymer of diallyldimethylammonium chloride having an RSV of ˜2 dL / g. The method can further include adding a second flocculant prior to adding the one or more particulates to the agglomerated dispersion. This filler may be dispersed as an anion and have a low molecular weight, and after the cationic coagulant is added to the dispersion to at least partially neutralize the anionic charge, the first flocculant Or fine particles are added. Swollen starch can also be added to the dispersion of filler particles. The swollen starch may be cationic, anionic, amphoteric or nonionic and / or may be a swollen starch-latex composition. Fine particles are siliceous materials, silica-based particles, silica microgel, colloidal silica, silica sol, silica gel, polysilicate, cationic silica, aluminosilicate, polyaluminosilicate, borosilicate, polyborosilicate, zeolite, and synthesis Or it may be one item selected from the list consisting of naturally occurring swellable clay, anionic polymer microparticles, cationic polymer microparticles, amphoteric organic polymer microparticles, and any combination thereof.

  At least one embodiment is directed to a paper product that incorporates a filler flock prepared as described herein.

  The following definitions are provided to determine the terms used in this application, and in particular how the claims are to be interpreted. The organization of definitions is for convenience only and is not intended to limit any of the definitions for a particular category. In this application, these terms are defined as follows.

  “Coagulant” means a composition of matter having a higher charge density and lower molecular weight than a flocculant, ie it is added to a liquid containing finely divided and suspended particles to charge the ions Solids are destabilized and aggregated through a mechanism that neutralizes the water.

  “Flocculant” means a composition of matter having a low charge density and high molecular weight (greater than 1,000,000), which was added to a liquid containing finely divided and suspended particles In some cases, the solid is destabilized and aggregated through a mechanism of interparticle crosslinking.

  “Aggregating agent” means a substance composition that, when added to a liquid, destabilizes and agglomerates colloidal fine suspension particles in the liquid. possible.

“GCC” means heavy calcium carbonate, which is produced by grinding naturally occurring calcium carbonate rock.
“PCC” means synthetically produced precipitated calcium carbonate.

  “Fine particle” means a particle having a size between 0.1 μm and 100 μm, which can be composed of several materials including silicon, ceramics, glass, polymer, and metal, Because they have a much larger surface area to volume ratio than similar macroscale sized materials, their behavior can be quite different.

  The above definitions or statements elsewhere in this application shall have the commonly used meaning (clearly or implicitly) as stated in the sources cited and incorporated in this application by dictionary or reference. In the event of a discrepancy, it is understood that the terms in this application and particularly the claims are to be interpreted according to the definitions or explanations in this application, rather than according to the usual definition dictionary definitions or definitions incorporated by reference. In light of the foregoing, if a term can be understood by the dictionary for the first time, it can be understood for the first time by Kirk-Othmer Encyclopedia of Chemical Technology, 5th Edition, (2005), (Published by Wiley, John & Sons, Inc.). This definition will regulate how the term should be defined in the claims.

  At least one embodiment is directed to a method of preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process. The first flocculant is added to the aqueous dispersion of filler particles in an amount and conditions that are uniformly mixed with the dispersion but do not cause significant aggregation of the filler particles. The fine particles are added to the dispersion either before, during or after the addition of the first flocculant. After both the first flocculant and the particulates have been added, the second flocculant is in an amount and conditions sufficient to initiate agglomeration of the filler particles in the presence of the first flocculant. Added to the dispersion. In at least one embodiment, the type of first agent and second agent and methods of their use and / or addition are any of the methods and procedures described in US Pat. No. 8,088,213. Or obey all.

  Optionally, the agglomerated dispersion can be sheared to provide a dispersion of filler floc having an optimal particle size.

  Although microparticles have been used previously in the papermaking process, their use in this manner is entirely new. In some prior art processes, microparticles are added at the wet end to prevent loss of material from the fiber filler mixture. In the present invention, however, the microparticles are added to the filler dispersion before the fibers and dispersion used to make the paper come into contact.

  The present invention relates to previous microparticles (such as those of US 2009/0267258) that use a method of preparing filler dispersions that are targeted to have optimum high shear stability at the same time as narrow particle sizes. In contrast, fine particles were used. In these previous methods, microparticles were used after the second (onset of aggregation) flocculant. In the present invention, the fine particles are added to the dispersion before the aggregation starts. This is because the present invention uses previously unknown properties of these microparticles.

  It is known that microparticles promote aggregation by strongly interacting with an aggregating agent to strengthen the resulting particle agglomeration. Thus, it has long been known that microparticles promote only one (shear strength) of two related excellence (shear strength and particle size).

  The present invention, however, uses the newly discovered fact that microparticles can interact well with filler particles without any agglomeration. Without being bound by theory or scenario, it is believed that the microparticles form a very hard “anchor site” on the surface of the filler particles. Since these anchor sites are much harder than the polymer that forms the flocs, they resist bending and cause the polymer agglomerates on the filler particles to be much tighter than the agglomerates fixed in situ by the aggregating agent. Hold on. Thus, the method of the present invention uses a microparticle that promotes the other of the above two excellences to increase the agglomerate size.

  In at least one embodiment, the microparticles include siliceous material and polymer microparticles. Representative siliceous materials include silica-based particles, silica microgel, colloidal silica, silica sol, silica gel, polysilicate, cationic silica, aluminosilicate, polyaluminosilicate, borosilicate, polyborosilicate, zeolite, and Synthetic or naturally occurring swellable clays. The swellable clay may be bentonite, hectorite, smectite, montmorillonite, nontronite, saponite, sauconite, morphite, attapulgite, and sepiolite. A suitable representative microparticle is the product PosiTEK 8699 (manufactured by Nalco Company, Naperville, Ill.).

  Polymeric fine particles useful in the present invention include anionic, cationic or amphoteric organic fine particles. These microparticles typically have finite solubility in water, may be cross-linked, and have a non-swelled particle size of less than 750 nm.

  As anionic organic fine particles, described in US Pat. No. 6,524,439, by hydrolyzing acrylamide polymer fine particles, or (meth) acrylic acid and its salts, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl -Those made by polymerizing anionic monomers such as (meth) acrylates, vinyl sulfonic acid, styrene sulfonic acid, maleic acid or other dibasic acids or their salts or mixtures thereof. These anionic monomers are (meth) acrylamide, N-alkylacrylamide, N, N-dialkylacrylamide, methyl (meth) acrylate, acrylonitrile, N-vinylmethylacetamide, N-vinylmethylformamide, vinyl acetate, N-vinyl. It can also be copolymerized with nonionic monomers such as pyrrolidone and mixtures thereof.

  Cationic organic microparticles described in US Pat. No. 6,524,439 and diallyldialkylammonium halides, acryloxyalkyltrimethylammonium chloride, (meth) acrylates of dialkylaminoalkyl compounds, and their salts and quaternary And monomers such as acid salts or quaternary salts of N, N-dialkylaminoalkyl (meth) acrylamide, (meth) acrylamidepropyltrimethylammonium chloride and N, N-dimethylaminoethyl acrylate What is produced by this is mentioned. These cationic monomers are (meth) acrylamide, N-alkylacrylamide, N, N-dialkylacrylamide, methyl (meth) acrylate, acrylonitrile, N-vinylmethylacetamide, N-vinylmethylformamide, vinyl acetate, N-vinyl. It can also be copolymerized with nonionic monomers such as pyrrolidone and mixtures thereof.

  Amphoteric organic particulates are at least one of the anionic monomers listed above, at least one of the cationic monomers listed above, and optionally at least one of the nonionic monomers listed above. It is made by polymerizing one kind of combination.

  The polymerization of the monomer in the organic fine particles is typically performed in the presence of a polyfunctional crosslinking agent. These crosslinkers are described in US Pat. No. 6,524,439 as having at least two double bonds, a double bond and one reactive group, or two reactive groups. Examples of these crosslinking agents are N, N-methylenebis (meth) acrylamide, polyethylene glycol di (meth) acrylate, N-vinylacrylamide, divinylbenzene, triallylammonium salt, N-methylallylacrylamide, glycidyl (meth) acrylate. Dialdehydes such as acrolein, methylolacrylamide, glyoxal, diepoxy compounds, and epichlorohydrin.

  In one embodiment, the particulate input is between 0.2 lb / ton (filler to be treated) and 8 lb / ton (filler to be treated). In one embodiment, the particulate input is between 0.5 lb / ton (filler to be treated) and 4.0 lb / ton (filler to be treated). These inputs apply to an effective pound of particulate per 2000 pounds of dry filler.

  In at least one embodiment, the method also includes contacting the filler particles with swollen starch. The starch slurry is controlled in a steam cooker as described in US Pat. Nos. 2,805,966, 2,113,034, 2,328,537, and 5,620,510. When heated under controlled temperature (and optionally controlled pH) conditions, starch can absorb large amounts of water without rupturing. The addition of such swollen starch can also increase the size of the filler floc used in the present invention. In at least one embodiment, the swollen starch is one or more cross-linked starches described in US Pat. No. 8,298,508 and International Patent Application WO / 97/46591.

  In at least one embodiment, the swollen starch added to the filler particles and / or the method of use thereof is any one of the swollen starch-latex compositions and methods described in US Patent Application 2010/0078138. by.

  By way of example, swollen starch-latex compositions are suitably prepared in the presence or absence of co-additives, in batches or jet cookers, or by mixing starch suspensions and latexes with hot water. For a given starch, the swelling is performed under controlled conditions of temperature, pH, mixing and mixing time to avoid rupture of the swollen starch granules. The composition is rapidly added to the filler suspension, which is then introduced into the paper finish at a point or headbox in front of the papermaking machine. During the drying operation, the retained swollen starch granules containing the filler particles rupture, thereby releasing the amylopectin and amylose polymers and binding them to the solid components of the sheet.

  The combination of swollen starch and latex can be used in filler treatments in acidic, neutral or alkaline environments. In at least one embodiment, the filler is treated with the swollen starch-latex composition, made with or without co-additives, and then added to the paper slurry. The filler particles agglomerate and the agglomerated filler particles adsorb to the fine fibers and fiber surfaces, causing their rapid agglomeration in the finish.

  In at least one embodiment, the swollen starch-latex composition is made by adding latex to uncooked starch followed by partial heating at a temperature slightly below the gel point to produce swollen starch. Is done.

  In at least one embodiment, the one or more swollen starch compositions (including the swollen starch-latex composition) are the first flocculant before or simultaneously with the addition of the microparticles to the filler dispersion. Is added before or simultaneously with, before or simultaneously with the addition of the second flocculant, after the second flocculant is added, and in any combination thereof.

  Fillers useful in the present invention are well known and commercially available. They typically contain any inorganic or organic particles or pigments used to increase milkiness or brightness, to increase smoothness, or to reduce the cost of paper or paperboard sheets. Including. Typical fillers include calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, magnesium hydroxide and the like. Calcium carbonate includes GCC, chalk, any form of PCC in dry or dispersed slurry form, and PCC in dispersed slurry form. Some examples of GCC and PCC slurries are shown in co-pending US patent application Ser. No. 12 / 323,976. GCC or PCC dispersed slurry forms are typically made using polyacrylic acid polymer dispersants or sodium polyphosphate dispersants. Each of these dispersants imparts a significant anionic charge to the calcium carbonate particles. Kaolin clay slurries can also be dispersed using polyacrylic acid polymer or sodium polyphosphate.

  In one embodiment, the filler is selected from calcium carbonate and kaolin clay and combinations thereof.

  In one embodiment, the filler is selected from precipitated calcium carbonate, heavy calcium carbonate and kaolin clay, and mixtures thereof.

  The first flocculant is preferably a cationic polymer flocculant when used with a cationic charged filler, and anionic when used with a filler charged with an anion. However, it may be anionic, non-ionic, zwitterionic, or amphoteric as long as it mixes uniformly and results in a highly solid slurry without causing significant agglomeration.

  The definition of “without significant agglomeration” is defined as medium, small in the absence of filler agglomeration in the presence of the first aggregating agent or smaller than that produced by the addition of the second aggregating agent. There is the formation of unstable flocs under shearing conditions. Medium shear is defined as the shear provided by mixing 300 ml of sample in a 600 ml beaker at 800 rpm using an IKA RE16 stirring motor with a 5 cm diameter, 4-blade turbine impeller. Is done. This shear should be similar to that present in modern paper machine approach systems.

  Suitable flocculants generally have molecular weights in excess of 1,000,000 and often in excess of 5,000,000.

  The polymer flocculant is typically a copolymerization of one or more cationic monomers and one or more nonionic monomers by vinyl addition polymerization of one or more cationic, anionic or nonionic monomers. By copolymerization of one or more anionic monomers and one or more nonionic monomers with one or more cationic monomers, one or more anionic monomers and optionally one or more nonionic monomers, Or by polymerization to form a zwitterionic polymer of one or more zwitterionic monomers and optionally one or more nonionic monomers. One or more zwitterionic monomers and optionally one or more nonionic monomers can also be copolymerized with one or more anionic or cationic monomers, and the zwitterionic polymer can be cationic or An anionic charge is imparted. Suitable flocculants generally have a charge content of less than 80 mole percent and often less than 40 mole percent.

  Cationic polymer flocculants can be formed using cationic monomers, but certain nonionic vinyl addition polymers can also be reacted to form a cationic charged polymer. This type of polymer includes those prepared by reacting polyacrylamide with dimethylamine and formaldehyde to produce a Mannich derivative.

  Similarly, anionic polymer flocculants can be formed using anionic monomers, but certain nonionic vinyl addition polymers can be modified to form charged anionic polymers. is there. This type of polymer includes, for example, those prepared by hydrolysis of polyacrylamide.

  The flocculant can be prepared in solid form, as an aqueous solution, as a water-in-oil emulsion, or as a dispersion in water. Typical cationic polymers include (meth) acrylamide and dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM) or dimethyl sulfate, methyl chloride or chloride. Mention may be made of copolymers and terpolymers with their quaternary ammonium form made with benzyl. As a typical anionic polymer, a copolymer of acrylamide and sodium acrylate and / or 2-acrylamide 2-methylpropanesulfonic acid (AMPS) or an acrylamide homopolymer in which a part of the acrylamide group is converted to acrylic acid by hydrolysis. Polymers.

  In one embodiment, the flocculant has an RSV of at least 3 dL / g.

  In one embodiment, the flocculant has an RSV of at least 10 dL / g.

  In one embodiment, the flocculant has an RSV of at least 15 dL / g.

As used herein, “RSV” represents reduced specific viscosity. Within a series of substantially linear and well solvated polymer homologs, the “reduced specific viscosity (RSV)” measurement for dilute polymer solutions is described by Paul J. Deletion of Molecular Weights by Flory, pages 266-316, Principles of Polymer Chemistry, Cornell University Press, Ithaca, New York, Chap. RSV is measured at a given polymer concentration and temperature and calculated as follows:
RSV = [(η / η ₀ ) −1] / c
[Where η = viscosity of polymer solution, η ₀ = viscosity of solvent at the same temperature and c = concentration of polymer in solution].

The unit of concentration “c” is (gram / 100 ml or g / deciliter). Therefore, the unit of RSV is dL / g. Unless otherwise noted, 1.0 molar sodium nitrate solution is used to measure RSV. The polymer concentration in this solvent is 0.045 g / dL. RSV is measured at 30 ° C. The viscosities η and η ₀ are measured using a size 75 Canon Ubbeloh desemi-microdilution viscometer. The viscometer is installed in a completely vertical position in a constant temperature bath adjusted to 30 ± 0.02 ° C. A typical inherent error in the calculation of RSV for the polymers described herein is about 0.2 dL / g. If two polymer homologues in the series have similar RSV, it indicates that they have similar molecular weight.

  As discussed above, the first flocculating agent is added in an amount sufficient to uniformly mix in the dispersion without causing significant flocculation of the filler particles. In one embodiment, the first flocculant charge is between 0.2 and 6.0 lb / ton (filler to be treated). In one embodiment, the flocculant charge is between 0.4 and 3.0 lb / ton (filler to be treated). For purposes of the present invention, “lb / ton” is a unit of charge, which means pounds of effective polymer (coagulant or flocculant) per 2,000 pounds of filler.

  The second flocculating agent may be any material that can initiate the flocculation of the filler in the presence of the first flocculating agent. In one embodiment, the second flocculant is selected from microparticles, coagulants, flocculants and mixtures thereof.

  Suitable coagulants generally have a lower molecular weight than the flocculant and have a higher density of cationic charge groups. Coagulants useful in the present invention are well known and commercially available. They may be inorganic or organic. Typical inorganic coagulants include alum, sodium aluminate, polyaluminum chloride or PAC (which may also be referred to as aluminum chlorohydroxide, aluminum hydroxide chloride, and polyaluminum hydroxychloride), sulfuric acid Polyaluminum chloride, polyaluminum silica sulfate, ferric sulfate, ferric chloride and the like and blends thereof.

  Many organic coagulants are formed by condensation polymerization. Examples of this type of polymer include epichlorohydrin-dimethylamine (EPI-DMA) copolymer, and EPI-DMA copolymer crosslinked with ammonia.

  Additional coagulants include polyfunctional amines such as ammonia, diethylenetriamine, tetraethylenepentamine, hexamethylenediamine and ethylene dichloride or adipic acid, as well as polymers of ethylene dichloride and ammonia or ethylene dichloride and dimethylamine. And those with or without the addition of a polymer prepared by a condensation reaction such as a condensation polymer with a polyfunctional acid such as melamine formaldehyde resin.

  Further coagulants include (meth) acrylamide, diallyl-N, N-disubstituted ammonium halide, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminoethyl acrylate and its quaternary ammonium salt, methacrylamidopropyltrimethyl To produce ammonium chloride, diallylmethyl (β-propionamido) ammonium chloride, (β-methacryloyloxyethyl) trimethylammonium methyl sulfate, quaternized polyvinyl lactam, vinylamine, and Mannich or quaternary Mannich derivatives And cationically charged vinyl addition polymers such as reacted acrylamide or methacrylamide polymers, copolymers, and terpolymers. Suitable quaternary ammonium salts can be formed using methyl chloride, dimethyl sulfate, or benzyl chloride. The terpolymer may contain an anionic monomer such as acrylic acid or 2-acrylamido 2-methylpropane sulfonic acid as long as the overall charge of the polymer is cationic. The molecular weight of these polymers, both vinyl addition and condensation, range from as low as several hundred to as high as several million.

  Other polymers useful as the second flocculant include cationic, anionic, or amphoteric polymers, and their chemical properties have been described above as flocculants. The distinction between these polymers and flocculants is primarily molecular weight.

  The second flocculant can be used alone or in combination with one or more additional second flocculants. In one embodiment, following the addition of the second flocculating agent, one or more particulates are added to the flocculated filler slurry.

  The second flocculant is added to the dispersion in an amount sufficient to initiate agglomeration of the filler particles in the presence of the first flocculant. In one embodiment, the input of the second flocculant is between 0.2 and 8.0 lb / ton (filler to be treated). In one embodiment, the input of the second component is between 0.5 and 6.0 lb / ton (filler to be treated).

  In one embodiment, one or more microparticles may be added to the agglomerated dispersion prior to shearing, providing additional agglomeration and / or narrow particle size distribution.

  In one embodiment, the second flocculant and the first flocculant are opposite in charge.

  In one embodiment, the first flocculant is cationic and the second flocculant is anionic.

  In one embodiment, the first flocculant is selected from copolymers of acrylamide with dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof.

  In one embodiment, the first flocculant is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) and has a cationic charge content of 5-50 mol% and an RSV of greater than 15 dL / g.

  In one embodiment, the second flocculant is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.

  In one embodiment, the second flocculating agent is an acrylamide-sodium acrylate copolymer having an anionic charge of 5-40 mole percent and an RSV of 0.3-5 dL / g.

  In one embodiment, the first flocculant is anionic and the second flocculant is cationic.

  In one embodiment, the first flocculant is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.

  In one embodiment, the first flocculant is a copolymer of acrylamide and sodium acrylate and has an anionic charge of 5 to 75 mole percent and an RSV of at least 15 dL / g.

  In one embodiment, the second flocculant is an epichlorohydrin-dimethylamine (EPI-DMA) copolymer, an EPI-DMA copolymer cross-linked with ammonia, and a diallyl-N, N-disubstituted ammonium halide. Selected from the group consisting of homopolymers.

  In one embodiment, the second flocculant is a homopolymer of diallyldimethylammonium chloride having an RSV of 0.1-2 dL / g.

  In one embodiment, the second flocculant is selected from copolymers of acrylamide with dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof.

  In one embodiment, the second flocculant is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) and has a cationic charge content of 5-50 mol% and an RSV of greater than 15 dL / g.

  Dispersions of filler floc according to the invention are prepared prior to their addition to the papermaking finish. This can be done in a batch mode or in a continuous mode. The filler concentration in these slurries is typically less than 80% by weight. It is more typically between 5% and 65% by weight.

  The batch process may consist of a large mixing vessel equipped with a superscript propeller mixer. The filler slurry is loaded into the mixing vessel and a desired amount of the first flocculant is fed to the slurry under continuous mixing. The slurry and flocculant are typically mixed for about 10 to 60 seconds, depending on the mixing energy used, for a time sufficient to uniformly distribute the first flocculant throughout the system. The desired amount of second flocculant is then added, during which mixing time is typically a few seconds depending on the mixing energy used, at a mixing rate sufficient to disrupt the filler floc. Stir while increasing to a few minutes. The microparticles are added to the filler slurry prior to, simultaneously with, and / or after adding the first flocculant prior to the second flocculant. Optionally, the microparticles are added after the second flocculant. The addition of fine particles improves the shear stability of the filler floc and narrows the floc particle size distribution. Once a suitable size distribution of the filler floc is obtained, the mixing speed is reduced to a level at which the floc is stable. This batch of agglomerated filler is then transferred to a larger mixing vessel, and with sufficient mixing, the filler floc is kept uniformly suspended in the dispersion. Agglomerated filler is pumped from this mixing vessel to the papermaking finish.

  In a continuous process, the desired amount of first flocculant is pumped into a pipe containing filler and mixed with an in-line static mixer if necessary. After a sufficient length of pipe or mixing vessel is included to allow proper mixing of the filler and flocculant, an appropriate amount of the second flocculant can be injected. The second flocculant is then pumped into the pipe containing the filler and, if necessary, mixed using an in-line static mixer. The particulates are pumped into a pipe containing the filler slurry and mixed using an in-line static mixer if necessary. The point of addition is before, simultaneously with and / or after the first flocculant is pumped and before the addition of the second flocculant. Optionally, the microparticles are pumped after the second flocculating agent. The addition of fine particles improves the shear stability of the filler floc and narrows the floc particle size distribution. Next, high speed mixing is required to obtain the desired size distribution of the filler floc. By adjusting either the shear rate or the mixing time of the mixing device, the floc size distribution can be controlled. The continuous process itself can use an adjustable shear rate in a fixed volume device. One such device is described in US Pat. No. 4,799,964. This device is a centrifugal pump with adjustable speed, which acts as a mechanical shear device without pumping capacity when operated with a back pressure that exceeds its shut-off pressure. Other suitable shearing devices include nozzles with adjustable pressure drop, turbine type emulsifying devices, or high intensity mixers with adjustable speed in fixed volume vessels. After shearing, the agglomerated filler slurry is fed directly to the papermaking finish.

  Both the batch and continuous processes described above can use filters or screens to remove filler flocs that are too large. This eliminates the mechanical maneuverability and paper quality problems that can arise from the large filler flocs contained in the paper or cardboard.

  In one embodiment, the median particle size of the filler floc is at least 10 μm. In one embodiment, the median particle size of the filler floc is between 10 μm and 100 μm. In one embodiment, the median particle size of the filler floc is between 10 μm and 70 μm.

  In at least one embodiment, the present invention is practiced using at least one composition and / or at least one method described in US patent application Ser. No. 12 / 975,596. In at least one embodiment, the present invention is practiced using at least one composition and / or at least one method described in US Pat. No. 8,088,213. In at least one embodiment, the present invention is practiced using at least one composition and / or at least one method described in US Pat. No. 8,172,983.

  The foregoing can be better understood with reference to the following examples, which are presented for purposes of illustration and are not intended to limit the scope of the invention.

として定義される分布のスパンによって示した。 Experimental Method In the filler flocculation experiment, the filler slurry was diluted to 10% solids with tap water and 300 mL of this diluted slurry was placed in a 500 mL glass beaker. Stirring was carried out for at least 30 seconds before any chemical additives were added. The stirrer was an IKA® EUROSTAR digital top-end mixer equipped with an R1342, 50 mm, 4-blade propeller (both from IKA® Works, Inc. (Wilmington, NC, USA). Available). The final floc size distribution was calculated using Malvern Instruments Ltd. Characterized by laser light scattering using a Malvern Mastersizer Micro from (Southborough, Massachusetts, USA). Analysis was performed using a polydisperse model and presentation 4PAD. This presentation assumes a refractive index of 1.33 for the real and zero imaginary components for the refractive index of the filler and water as the continuous phase. The characteristics of the distribution are the median D (V, 0.5) of the flock size weighted with

Indicated by the span of the distribution defined as

  Where D (V, 0.1), D (V, 0.5), and D (V, 0.9) are diameters of 10%, 50%, and 90% or more of the filler floc volume. As defined respectively. Smaller span values indicate a more uniform particle size distribution, which is considered to have better performance in papermaking. The D (V, 0.5) and span values for each example are listed in Tables I and II.

Example 1
The filler used was a dry powder of declinated trihedral precipitated calcium carbonate (PCC), available as Albacar HO from Specialty Minerals Inc. (Bethlehem, PA, USA). This PCC powder was dispersed in tap water at 10% solids. The slurry was stirred at 800 rpm and a small sample was taken and the particle size distribution was measured using a Malvern Mastersizer. In the experiment, a) the flocculant DEV115 (which is a commercially available anionic sodium acrylate-acrylamide copolymer having an RSV of about 32 dL / g and a charge content of 29 mole percent, Nalco Company (Naperville, Ill.) B) flocculant DEV125, which is a commercially available cationic acrylamide-dimethylaminoethyl acrylate-methyl chloride quaternary having an RSV of about 25 dL / g and a charge content of 10 mole percent. Salt copolymers, Nalco Company (available from Naperville, Illinois, USA), and c) Fine Particles Nalco-8699 (this is Nalco Company (Naperville, Illinois, USA) ) Was a commercially available a colloidal silica dispersion) available from.

  The results in Table 1 indicate that the untreated PCC had a unimodal particle size distribution with a median particle size of 3.75 μm and a span of 1.283. After mixing 10% PCC slurry at 800 rpm for 30 seconds, use a syringe to slowly add 1.5 lb / ton Nalco DEV115 to the slurry, followed by 1.0 lb / ton Nalco DEV125 using another syringe. And slowly added. After the addition of DEV125, one filler sample was taken for particle size measurement (time = 0 minutes) and then the stirring speed was increased to 1500 rpm and held for 8 minutes. Samples were taken every 2 minutes to measure the particle size distribution (time = 2, 4, 6, and 8 minutes). This shearing was performed for the purpose of evaluating the stability of the filler floc. The results are shown in Table 1.

(Example 2)
Experiment 1 was repeated with microparticles as one of the components in the treatment program. After adding 0.5 lb / ton Nalco-8699, DEV115 was added.

(Example 3)
Experiment 1 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added followed by DEV115.

Example 4
Experiment 1 was repeated with microparticles as one of the components in the treatment program. DEV115 was added after 1.5 lb / ton Nalco-8699 was added.

(Example 5)
Experiment 1 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added after DEV115 but before DEV125.

(Example 6)
Experiment 1 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added after the addition of DEV125.

(Example 7)
Experiment 1 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 and 1.5 lb / ton DEV115 were premixed and then added to the filler slurry followed by DEV125.

  The results in Table I show that for Nalco-8699 microparticles in the aggregation program, added before or after the anionic flocculant, premixed with the anionic flocculant, or cationic flocculant It was not a problem whether it was added after, indicating that both the filler agglomeration and the shear stability of the resulting filler floc were significantly improved.

(Example 8)
The filler used was 70% solid heavy calcium carbonate (GCC) slurry. The slurry was diluted with tap water to 10% solids. The slurry was stirred at 800 rpm, a small sample was taken, and the particle size distribution was measured using a Malvern Mastersizer. The results in Table II show that the untreated GCC had a unimodal particle size distribution with a median particle size of 1.51 μm and a span of 2.029.

  After mixing the 10% GCC slurry at 800 rpm for 30 seconds, 1.5 lb / ton Nalco DEV120 is added to the slurry followed by a slow addition of 0.75 lb / ton Nalco DEV115 to the slurry using a syringe. To this, 0.60 lb / ton Nalco DEV125 was slowly added using another syringe. After the addition of DEV125, one filler sample was taken for particle size measurement (time = 0 minutes), then the stirring speed was increased to 1500 rpm and held for 8 minutes. Samples were taken every 2 minutes to measure the particle size distribution (time = 2, 4, 6, and 8 minutes). The results are shown in Table II.

Example 9
Experiment 8 was repeated with microparticles as one of the components in the treatment program. 0.5 lb / ton Nalco-8699 was added prior to the addition of DEV115.

(Example 10)
Experiment 8 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added prior to the addition of DEV115.

(Example 11)
Experiment 8 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added after DEV115 but before DEV125.

(Example 12)
Experiment 8 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 was added after the addition of DEV125.

(Example 13)
Experiment 8 was repeated with microparticles as one of the components in the treatment program. 1.0 lb / ton Nalco-8699 and 0.75 lb / ton DEV115 were premixed and then added to the filler slurry followed by DEV125.

  The results in Table II show that for Nalco-8699 microparticles in the aggregation program, added before or after the anionic flocculant, added premixed with the anionic flocculant, or cationic aggregation It did not matter whether it was added after the agent, indicating that both the filler agglomeration and the shear stability of the resulting filler floc were significantly improved.

  While this invention may be expressed in many different forms, there are described in detail herein specific preferred embodiments of the invention. This disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. All patents, patent applications, scientific articles, and any other references cited herein are incorporated by reference in their entirety. Furthermore, the present invention encompasses any possible combination of some or all of the various embodiments described herein and / or incorporated herein. In addition, the present invention encompasses any possible combination that specifically excludes any one or several of the various embodiments described and / or incorporated herein.

  The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and modifications are intended to be included within the scope of the claims, and in the claims, the term “comprising” means “including but not limited to”. Those skilled in the art will recognize other equivalent forms for the specific embodiments described herein, which equivalent forms are also intended to be encompassed by the claims.

  It is understood that all ranges and parameters disclosed herein include any and all subranges subsumed therein and all numbers between the endpoints. For example, a range stated as “1 to 10” should be considered to include any and all subranges between 1 being the minimum and 10 being the maximum (including 1 and 10) . That is, all the partial ranges start with a minimum value of 1 or more (for example, 1 to 6.1) and have a maximum value of 10 or less (for example, 2.3 to 9.4, 3 to 8, 4 to 7). At the end, the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 are also included in the range. All percentages and ratios are by weight unless otherwise indicated.

  This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art will recognize other equivalent forms for the specific embodiments described herein, which equivalent forms are intended to be encompassed by the claims appended hereto.

Claims (15)

A method of preparing a stable dispersion of aggregated filler particles having a specific particle size distribution for use in a papermaking process comprising:
a) providing an aqueous dispersion of filler particles;
b) adding the first flocculating agent to the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles; A step wherein the agent is amphoteric;
c) the microparticles in an amount insufficient to cause significant aggregation of the filler particles before, simultaneously with and / or after the addition of the first flocculant and prior to the second flocculant. Adding to the dispersion;
d) adding a second flocculant to the dispersion in an amount sufficient to initiate agglomeration of filler particles in the presence of the first flocculant; Having a charge opposite to the net charge of the amphoteric first flocculant;
e) shearing the agglomerated dispersion to provide a dispersion of filler floc having a desired particle size;
and f) agglomerating the filler particles in the absence of the papermaking raw material and then adding them to the papermaking raw material.   2. A method according to claim 1, wherein the filler floc has a median particle size of 10 to 100 [mu] m.   The method of claim 1, wherein the filler is from precipitated calcium carbonate, heavy calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate and magnesium hydroxide, and mixtures thereof. A method characterized in that it is selected from the group consisting of:   2. The method of claim 1, wherein the first flocculant has a net anionic charge.   5. The method of claim 4, wherein the second flocculant is cationic and comprises (meth) acrylamide, dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEEAA). ), Diethylaminoethyl methacrylate (DEAEM) or their quaternary ammonium forms made using dimethyl sulfate, methyl chloride or benzyl chloride and copolymers and mixtures thereof with terpolymers And how to.   6. The method of claim 5, wherein the second flocculant is an acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10 to 50 mole percent and an RSV of at least 15 dL / g. A method characterized by being.   5. The method of claim 4, wherein the second flocculant is a homopolymer of diallyldimethylammonium chloride having an RSV of 0.1-2 dL / g.   The method of claim 1, further comprising adding one or more microparticles to the agglomerated dispersion after the addition of the second aggregating agent.   The method of claim 1, wherein the filler is dispersed as an anion and a low molecular weight cationic coagulant is added to the dispersion to neutralize its anionic charge at least partially. A method comprising adding 1 flocculant or microparticles.   9. The method of claim 8, wherein the filler is dispersed as an anion and a low molecular weight cationic coagulant is added to the dispersion to neutralize its anionic charge at least partially. A method comprising adding 1 flocculant or microparticles.   2. The method of claim 1, further comprising adding swollen starch to the dispersion of filler particles.   12. A method according to claim 11, characterized in that the swollen starch is added before and / or after the addition of the first flocculant and before the addition of the second flocculant.   12. The method according to claim 11, wherein the swollen starch is cationic, anionic, amphoteric or nonionic.   11. The method of claim 10, wherein the swollen starch is a swollen starch-latex composition.   The method according to claim 1, wherein the fine particles are siliceous material, silica-based particles, silica microgel, colloidal silica, silica sol, silica gel, polysilicate, cationic silica, aluminosilicate, polyaluminosilicate, One selected from the list consisting of borosilicates, polyborosilicates, zeolites, and synthetic or naturally occurring swellable clays, anionic polymer particles, cationic polymer particles, amphoteric organic polymer particles, and any combination thereof A method characterized in that