TWI487823B - Preflocculation of fillers used in papermaking - Google Patents

Description

Pre-flocculation for paper filler [related application]

This application is a continuation-in-part of U.S. Patent Application Serial No. 13/449,888 filed on Apr. 18, 2012, which is hereby incorporated by reference. Part of the priority application of No. 854,044 is filed and filed as U.S. Patent No. 8,172,983.

[Statement on Federally Funded Research or Development]

Not applicable.

The present invention relates to pre-flocculation for papermaking fillers, and in particular to the production of shear-resistant filler floes having a defined and controllable particle size distribution at high filler solids.

In order to improve product quality and reduce raw material and energy costs, increased printing and writing paper in the filler content are of great concern. However, replacing cellulose fibers with fillers such as calcium carbonate and clay reduces the strength of the finished sheet. Another problem with increasing filler content is the difficulty of maintaining an even distribution of the filler throughout the three dimensional sheet structure. One way to reduce these negative effects of increasing the filler content is to pre-flocculate the filler prior to adding the filler to the wet end of the paper machine into the system.

The term "preflocculation" is defined as the modification of filler particles to agglomerates by treatment with aggregating agents and/or flocculants prior to flocculation of the filler particles and addition to the papermaking stock. The flocculation process and shear forces of the process determine the flocculation before it is added to the paper stock Particle size distribution and stability. The chemical environment and high fluid shear rates present in modern high speed papermaking require that the filler floes be stable and resistant to shear. The floc size distribution obtained by pre-flocculation treatment should minimize the decrease of the strength of the flakes, increase the loss of light efficiency caused by the filler particles, and minimize the uniformity of the flakes. The negative effects of printability are minimized. In addition, the entire system must be economically viable.

Therefore, the combination of high shear stability and sharp particle size distribution is critical to the success of the filler pre-flocculation technology. However, filler floes formed separately from low molecular weight aggregating agents and including conventional starches tend to have a relatively small particle size which is compromised under the high shear forces of the paper machine. Filler floes formed from a single high molecular weight flocculant tend to have a broad particle size distribution that is difficult to control, and this particle size distribution deteriorates at higher filler solids levels, primarily due to the incorporation of the viscous flocculant solution into the slurry. Poor mixing. Therefore, there is a continuing need for improved pre-flocculation techniques.

The technology described in this section is not intended to be an admission that any of the patents, disclosures, or other information referred to herein are the prior art of the present invention unless otherwise explicitly indicated. In addition, this section should not be understood to mean that research has been conducted or that there is no other relevant information as defined in 37 C.F.R.§ 1.56(a).

At least one specific example relates to a method of preparing a stable dispersion of flocculating filler particles having a particular particle size distribution for use in a papermaking process. The method comprises the steps of: a) providing an aqueous dispersion of filler particles; b) adding a first flocculating agent to the dispersion in an amount sufficient to uniformly mix in the dispersion without causing significant flocculation of the filler particles, and the first flocculating agent Is amphoteric; c) before, simultaneously with and/or after the addition of the first flocculating agent, and prior to the addition of the second flocculating agent, adding particles to the dispersion in an amount insufficient to cause significant flocculation of the filler particles; d) sufficient Adding a second flocculating agent to the dispersion in the presence of the first flocculating agent, wherein the second flocculating agent has a charge opposite to the net charge of the first amphoteric flocculating agent; e) shearing flocculation dispersion Obtaining a dispersion of filler floes having a desired particle size; f) Flocculating the filler particles prior to the addition of the filler particles to the papermaking feedstock, and wherein no papermaking stock is present during flocculation.

The filler floc may have a median particle size of 10-100 μm. The filler may be selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, and magnesium hydroxide, and mixtures thereof. The first flocculating agent can have a net anionic charge. The second flocculating agent may be cationic and/or may be selected from the group consisting of (meth)acrylamide and dimethylaminoethyl methacrylate (DMAEM), dimethylamino acrylate Ethyl ester (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM) or its preparation with dimethyl sulfate, methyl chloride or benzyl chloride Copolymers and terpolymers of the quaternary ammonium form, and mixtures thereof. The second flocculating agent may be acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10 to 50 mol% and an RSV of at least 15 dL/g; and/or may be A homopolymer of diallyldimethylammonium chloride having an RSV of from 0.1 to 2 dL/g. The method can further comprise adding one or more particulates to the flocculated dispersion after the addition of the second flocculating agent. The filler may be dispersed in an anionic form and a low molecular weight cationic aggregating agent is added to the dispersion to at least partially neutralize its anionic charge prior to the addition of the first flocculating agent or particulate. Swelling starch may also be added to the dispersion of filler particles. The swollen starch can be cationic, anionic, amphoteric or nonionic, and/or can be a swollen starch-latex composition. The microparticles may be one selected from the list consisting of enamel materials, cerium oxide-based particles, cerium oxide microgels, colloidal cerium oxide, cerium oxide sol, cerium oxide gel, poly Citrate, cationic ceria, aluminosilicate, polyaluminum silicate, borosilicate, polyborate, zeolite, and synthetic or naturally occurring expanded clay, anionic polymeric particles, cationic Polymeric microparticles, amphoteric organic polymeric microparticles, and any combination thereof.

At least one specific example relates to a paper product having a filler floe prepared as described herein.

The following definitions are provided to determine how the terms used in this application and in particular the scope of the patent application should be interpreted. The organization of the definition is for convenience only and it is not intended to limit any of the definitions to any particular category. For the purposes of this application, these terms are defined as follows:

"Aggregating agent (Coagulant)" means flocculant having a higher charge density and composition of relatively low molecular weight compared to substances, which when added to a liquid containing suspended particles of the finely divided, its ionic charge neutralization mechanism via The solids are destabilized and aggregated.

"Coagulant (flocculant)" means having a low charge density and a high molecular weight composition (more than 1,000,000) of the material, which when added to a liquid containing suspended particles of the finely divided, via the inter-particle bridging mechanism The solids are unstable and aggregate.

"Flocculating Agent " means a composition of a substance which destabilizes and aggregates colloidal and finely pulverized suspended particles in a liquid when added to a liquid, and the flocculating agent and the aggregating agent may be a flocculating agent.

" GCC " means ground calcium carbonate produced by grinding naturally occurring calcium carbonate rock.

" PCC " means precipitation of calcium carbonate, which is produced synthetically.

" Microparticle " means a particle having a size between 0.1 μm and 100 μm, which can constitute many materials including bismuth, ceramic, glass, polymer, and metal because of the surface-to-volume ratio of the particles (surface-to- Volume ratio) is much larger than materials of similar large size dimensions, so its behavior can be quite different.

In the event that the above definitions or the descriptions set forth in this application are inconsistent with the meanings (clear or implied) stated in the source of the dictionary, which is commonly used or incorporated by reference in the present application, the present application and In particular, the terms of the patent application are to be understood as being interpreted in accordance with the definition or description of the present application, and not by the definition of the common definition, the definition of the dictionary, or the definition incorporated by reference. According to the above, in the case where the term can only be understood by dictionary interpretation, if the term is defined by Kirk-Othmer Encyclopedia of Chemical Technology , 5th edition, (2005) (published by Wiley, John & Sons), this definition This term should be defined in the scope of the patent application.

At least one specific example relates to a method of preparing a stable dispersion of flocculating filler particles having a particular particle size distribution for use in a papermaking process. The first flocculating agent is added to the aqueous dispersion of the filler particles in an amount and condition that is uniformly mixed with the dispersion without causing any significant flocculation of the filler particles. Microparticles are added to the dispersion before, during or after the addition of the first flocculating agent. After the first flocculating agent and the microparticles have been added, a second flocculating agent is added to the dispersion in an amount and under conditions sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent. In at least one embodiment, the type of first reagent and second reagent, and methods of use and/or addition thereof, are according to any and all of the methods and procedures described in U.S. Patent No. 8,088,213.

Optionally, the flocculated dispersion can be sheared to obtain a filler floc dispersion having an optimum particle size.

Although the particles have previously been used in papermaking processes, their use in this manner is quite novel. In some prior art processes, particulates are added to the wet end to prevent loss of material from the fiber-filler mixture. However, in the present invention, fine particles are added to the filler dispersion before the dispersion is contacted with the fibers for papermaking.

The present invention is also different from the prior particle use method for preparing a filler dispersion, the purpose of which is to have an optimum degree of high shear stability while the particles used, such as the particles of US Published Patent Application No. 2009/0267258, have sharp particle sizes. Sex. Their previous methods used microparticles after the second (flocculation initiation) flocculation reagent. In the present invention, the microparticles are added to the dispersion before the start of flocculation. This is because the present invention utilizes previously unknown characteristics of such particles.

It is known that microparticles promote flocculation by strongly interacting with flocculating agents to enhance coalescence of the resulting particles. Therefore, it has been previously known that particles only contribute to the two properties of interest (cutting One of shear strength and particle size (shear strength).

However, the present invention takes advantage of the new discovery that microparticles can actively interact with filler particles without any flocculation. Without being bound by theory or design, the salt particles form a very hard "anchor site" on the surface of the filler particles. Because these anchoring points are much harder than the flocculated polymer, they resist bending and the fixation of the polymer agglomerates onto the filler particles is more robust than anchoring the agglomerates in place by the flocculating agent. Thus, the method of the invention uses microparticles to promote the other of the two properties, thereby increasing the size of the agglomerates.

In at least one embodiment, the microparticles comprise a enamel material and polymeric microparticles. Representative enamel materials include cerium oxide-based particles, cerium oxide microgels, colloidal cerium oxide, cerium oxide sol, cerium oxide gel, polysilicate, cationic cerium oxide, aluminum lanthanum Acid salts, polyaluminum silicates, borosilicates, polyborates, zeolites and synthetic or naturally occurring expanded clays. The expanded clay may be bentonite, laponite, bentonite, montmorillonite, nontronite, saponite, saponite, mulmite, attapulgite and sepiolite. A suitable representative particle is the product PosiTEK 8699 (manufactured by Nalco Corporation (Naperville IL)).

Polymeric microparticles suitable for use in the present invention include anionic, cationic or amphoteric organic microparticles. These particles typically have limited solubility in water, are crosslinkable, and have an unexpanded particle size of less than 750 nm.

Anionic organic microparticles include such microparticles as described in US 6,524,439 and are prepared by hydrolyzing acrylamide polymer microparticles or by polymerizing an anionic monomer such as (methyl) Acrylic acid and its salts, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl (meth)acrylate, vinyl sulfonic acid, styrene sulfonic acid, maleic acid or other dibasic acids Or a salt thereof or a mixture thereof. These anionic monomers may also be copolymerized with nonionic monomers such as (meth) acrylamide, N-alkyl acrylamide, N, N-dialkyl acrylamide, (meth) acrylate Methyl ester, acrylonitrile, N-vinylmethylacetamide, N-vinylmethylformamide, vinyl acetate, N-vinylpyrrolidone, and mixtures thereof.

Cationic organic microparticles include such microparticles as described in US 6,524,439 and are prepared by polymerizing monomers such as diallyldialkylammonium halide, propyleneoxyalkylene trimethylammonium chloride. a monomer of a dialkylaminoalkyl (meth)acrylate compound, and a salt thereof and a quaternary salt thereof, and an N,N-dialkylaminoalkyl(meth)acrylamide, chlorinated (A) a monomer of acrylamidopropyltrimethylammonium, and an acid of N,N-dimethylaminoethyl acrylate or a quaternary salt thereof and the like. These cationic monomers may also be copolymerized with nonionic monomers such as (meth) acrylamide, N-alkyl acrylamide, N,N-dialkyl acrylamide, (meth)acrylic acid. Methyl ester, acrylonitrile, N-vinylmethylacetamide, N-vinylmethylformamide, vinyl acetate, N-vinylpyrrolidone, and mixtures thereof.

The amphoteric organic microparticles by the at least one of the above-mentioned anionic monomers, at least one of the above-exemplified cationic monomers, and, as the case may be, the nonionic monomers listed above A combination of at least one of them is prepared by polymerization.

The polymerization of the monomers in the organic microparticles is typically carried out in the presence of a multifunctional crosslinking agent. Such crosslinkers are described in US 6,524,439 as having at least two double bonds, one double bond and one reactive group, or two reactive groups. Examples of such agents are N,N-methylenebis(meth)acrylamide, polyethylene glycol di(meth)acrylate, N-vinyl acrylamide, divinylbenzene, triallyl Ammonium salt, N-methylallyl acrylamide glycidyl (meth)acrylate, acrolein, methylol acrylamide, dialdehyde such as glyoxal, diepoxide, and epichlorohydrin.

In one embodiment, the particulate dose is between 0.2 and 8 pounds per ton of treated filler. In one embodiment, the particulate dose is between 0.5 pounds and 4.0 pounds per ton of treated filler. These doses refer to the number of pounds of active particles per 2,000 pounds of dry filler.

In at least one embodiment, the method also involves contacting the filler particles with the swollen starch. As described in U.S. Patent Nos. 2,805,966, 2,113,034, 2,328,537, and 5,620,510, when the starch slurry is cooked in a steam cooker at a controlled temperature (and optionally at a controlled pH), the starch may not rupture. Undertake a lot of water. The addition of such swollen starch can also The size of the filler floes used in the present invention is increased. In at least one embodiment, the swollen starch is one or more of the crosslinked starches, such as those described in U.S. Patent No. 8,298,508 and International Patent Application No. WO/97/46,591.

In at least one embodiment, the swollen starch added to the filler particles and/or method of use thereof is according to any of the swollen starch-latex compositions and methods described in U.S. Patent Application Serial No. 2010/0078138.

As an example, a swollen starch-latex composition, in the presence or absence of a co-additive, is suitably prepared in a batch digester or jet digester or by mixing a suspension of starch and latex with hot water. . For a given starch, swelling is carried out under conditions controlled by temperature, pH, mixing and mixing time to avoid rupture of the swollen starch granules. The composition is quickly added to the filler suspension and subsequently introduced into the papermaking furnish at some point before or during the headbox of the paper machine. During the drying operation, the swollen starch granules retained with the filler particles will rupture, releasing the amylopectin and amylose macromolecules to bind the solid components of the flakes.

The combination of swollen starch and latex can be used for filler treatment in an acidic, neutral or alkaline environment. In at least one embodiment, the filler is treated with a swollen starch-latex composition prepared in the presence or absence of a co-additive and subsequently added to the pulp. The filler particles coalesce and the coalesced filler particles are adsorbed on the surface of the fine particles and the fibers to promote rapid flocculation of the filler particles in the furnish.

In at least one embodiment, the swollen starch-latex composition is prepared by adding a latex to the uncooked starch, which is then partially cooked at a temperature slightly below the gel point to produce a swollen starch.

In at least one specific example, prior to or simultaneously with the addition of the microparticles, prior to or simultaneously with the addition of the first flocculating agent, prior to or simultaneously with the addition of the second flocculating agent, after the addition of the second flocculating agent, and any combination thereof, One or more swollen starch compositions (including swollen starch-latex compositions) are added to the filler dispersion.

Fillers suitable for use in the present invention are well known and commercially available. It will typically include any inorganic or organic particles or pigments used to increase opacity or brightness, increase smoothness, or reduce the cost of paper or paperboard flakes. Representative fillers include calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, magnesium hydroxide, and the like. Calcium carbonate includes GCC in the form of a dry or dispersed slurry, chalk, PCC in any form, and PCC in the form of a dispersed slurry. Some examples of GCC and PCC slurries are provided in U.S. Patent Application Serial No. 12/323,976, the disclosure of which is incorporated herein. The dispersed slurry form of GCC or PCC is typically produced using a polyacrylic acid polymer dispersant or a sodium polyphosphate dispersant. Each of these dispersants imparts a large amount of anionic charge to the calcium carbonate particles. The kaolin clay slurry can also be dispersed using a polyacrylic acid polymer or sodium polyphosphate.

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

In one embodiment, the filler is selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate, and kaolin clay, and mixtures thereof.

When used with a cationically charged filler, the first flocculating agent is preferably a cationic polymeric flocculant; and when used with an anionically charged filler, the first flocculating agent is preferably an anionic polymeric flocculant. However, it may be anionic, nonionic, zwitterionic or amphoteric as long as it is uniformly mixed into the high solids slurry without causing significant flocculation.

"Without causing significant flocculation" is defined as the absence of filler flocculation in the presence of the first flocculating agent, or the formation of flocs is less than that produced by the addition of the second flocculating agent and under moderate shear conditions. Unstable. Medium shear was defined as shearing by mixing 300 ml samples in a 600 ml beaker with a 5 cm diameter four-blade turbine wheel at 800 rpm using an IKA RE16 agitator motor. This shear should be similar to the shear present in the entry system of modern paper machines.

In general, suitable flocculants have a molecular weight in excess of 1,000,000 and often in excess of 5,000,000.

Polymeric flocculants are typically prepared by the following polymerization: vinyl addition polymerization of one or more cationic, anionic or nonionic monomers, one or more cationic monomers and one or more nonionic monomers Copolymerization, copolymerization of one or more anionic monomers with one or more nonionic monomers, one or more cationic monomers with one or more anionic monomers and, optionally, one or more nonionic monomers Copolymerization of the body produces an amphoteric polymer, or polymerization of one or more zwitterionic monomers and, optionally, one or more nonionic monomers to form a zwitterionic polymer. One or more zwitterionic monomers and, optionally, one or more nonionic monomers may also be copolymerized with one or more anionic or cationic monomers to impart a cationic or anionic charge to the zwitterionic polymer. In general, suitable flocculants have a charge content of less than 80 mole percent and often less than 40 mole percent.

While cationic polymeric flocculants can be formed using cationic monomers, certain nonionic vinyl addition polymers can also be reacted to produce cationically charged polymers. Polymers of this type include those polymers prepared by the reaction of polypropylene decylamine with dimethylamine and formaldehyde to produce Mannich derivatives.

Similarly, while anionic polymeric flocculants can be formed using anionic monomers, it is also possible to modify certain nonionic vinyl addition polymers to form anionically charged polymers. Polymers of this type include, for example, those polymers prepared by hydrolysis of polyamidamine.

The flocculating agent can be prepared as an aqueous solution, a water-in-oil emulsion or a dispersion in water depending on the solid form. Representative cationic polymers include (meth)acrylamide and dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate ( DEAEA), diethylaminoethyl methacrylate (DEAEM) or a copolymer and terpolymer of the quaternary ammonium form thereof prepared with dimethyl sulfate, methyl chloride or benzyl chloride. Representative anionic polymers include copolymers of acrylamide with sodium acrylate and/or 2-propenylamino 2-methylpropane sulfonic acid (AMPS) or by hydrolysis to convert a portion of the acrylamide group to acrylic acid. Acrylamide homopolymer.

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" means a reduced specific viscosity. Within a series of polymer homologs that are substantially linear and well solvated, according to Determination of Molecular Weights , Paul J. Flory, pp. 266-316, Principles of Polymer Chemistry , Cornell University Press, Ithaca, NY, Section VII In Chapter (1953), the "increasing ratio thick viscosity (RSV)" measurement of the dilute polymer solution indicates the polymer chain length and average molecular weight. RSV is measured at a given polymer concentration and temperature and is calculated as follows: RSV = [(η / η ₀ ) - 1] / c, where η = viscosity of the polymer solution, η ₀ = viscosity of the solvent at the same temperature And c = the concentration of the polymer in the solution.

The unit of concentration "c" is (g/100 ml or g/d). Therefore, the unit of RSV is dL/g. RSV was measured using a 1.0 molar solution of sodium nitrate unless otherwise stated. The polymer concentration in this solvent was 0.045 g/dL. RSV was measured at 30 °C. Viscosity η and η ₀ were measured using a Cannon Ubbelohde semi-microdilution viscometer (size 75). The viscometer is mounted in a fully vertical position in a constant temperature bath adjusted to 30 ± 0.02 °C. A typical error inherent in the RSV calculation of the polymers described herein is about 0.2 dL/g. When two polymer homologs in a series have similar RSV, they are indicated to have similar molecular weights.

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 flocculating agent dose is between 0.2 pounds and 6.0 pounds per ton of treated filler. In one embodiment, the flocculant dosage is between 0.4 pounds and 3.0 pounds per ton of treated filler. For the purposes of the present invention, "lb/ton" is a dosage unit which means the number of pounds of active polymer (aggregator or flocculant) per 2,000 pounds of filler.

The second flocculating agent can be any material that can initiate flocculation of the filler in the presence of the first flocculating agent. In one embodiment, the second flocculating agent is selected from the group consisting of microparticles, aggregating agents, flocculating agents, and mixtures thereof.

In general, suitable aggregating agents have a lower molecular weight than the flocculating agent and have a high density of cationic charge groups. Agglutinators suitable for use in the present invention are well known and commercially available. It can be inorganic or organic. Representative inorganic aggregating agents include barium, sodium aluminate, polyaluminum chloride or PAC (which may also be called aluminum chlorohydroxide, aluminum chloride and polyhydroxyaluminum chloride), sulfated polyaluminum chloride, polyoxygen dioxide Aluminum sulphate, ferric sulphate, ferric chloride, and the like, and blends thereof.

Many organic aggregating agents are formed by condensation polymerization. Examples of polymers of this type include epichlorohydrin-dimethylamine (EPI-DMA) copolymers and EPI-DMA copolymers crosslinked with ammonia.

Other aggregating agents include polymers of ethylene dichloride with ammonia or ethylene dichloride and dimethylamine with or without the addition of ammonia, polyfunctional amines such as di-ethyltriamine, tetraethylidene pentaamine a condensation polymer of hexamethylenediamine and the like thereof with ethylene dichloride or a polyfunctional acid such as adipic acid, and a polymer obtained by a condensation reaction such as a melamine formaldehyde resin.

Other aggregating agents include cationically charged vinyl addition polymers such as polymers, copolymers and terpolymers of the following materials: (meth) acrylamide, diallyl-N, N-disubstituted Ammonium halide, dimethylaminoethyl methacrylate and its quaternary ammonium salt, dimethylaminoethyl acrylate and its quaternary ammonium salt, methacrylamidopropyltrimethylammonium chloride, Diallylmethyl (β-propionyl) ammonium chloride, methyl sulfuric acid (β-methacryloxyethyl) trimethylammonium, quaternized ammonium polyvinylamine, ethylene An amine, and acrylamide or methacrylamide, which has been reacted to produce a Mannich or a quaternary Mannich derivative. Suitable quaternary ammonium salts can be produced using methyl chloride, dimethyl sulfate or benzyl chloride. The terpolymer may include an anionic monomer such as acrylic acid or 2-propenylamino 2-methylpropanesulfonic acid as long as the total charge on the polymer is cationic. The molecular weight of these polymers (vinyl addition and condensation) ranges from as low as hundreds to as high as several million Inside.

Other polymers suitable for use as the second flocculating agent include cationic, anionic or amphoteric polymers whose chemistry is described above as a flocculating agent. The difference between these polymers and flocculants is primarily molecular weight.

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

The second flocculating agent is added to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent. In one embodiment, the second flocculating agent dose is between 0.2 pounds and 8.0 pounds per ton of treated filler. In one embodiment, the second component dose is between 0.5 pounds and 6.0 pounds per ton of treated filler.

In one embodiment, one or more particulates may be added to the flocculation dispersion prior to shearing to provide additional flocculation and/or to narrow the particle size distribution.

In one embodiment, the second flocculating agent is oppositely charged to the first flocculating agent.

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

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

In one embodiment, the first flocculating agent is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) having a cationic charge content of from 5 to 50 mole percent and an RSV of greater than 15 dL/g.

In one embodiment, the second flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and a copolymer of acrylamide and sodium acrylate.

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

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

In one embodiment, the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and a copolymer of acrylamide and sodium acrylate.

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

In one embodiment, the second flocculating agent is selected from the group consisting of epichlorohydrin-dimethylamine (EPI-DMA) copolymers, EPI-DMA copolymers crosslinked with ammonia, and diallyl-N,N-disubstituted A group of homopolymers of ammonium halides.

In one embodiment, the second flocculating agent is a homopolymer of diallyldimethylammonium chloride having an RSV of from 0.1 to 2 dL/g.

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

In one embodiment, the second flocculating agent is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) having a cationic charge content of from 5 to 50 mole percent and an RSV of greater than 15 dL/g.

The dispersion of filler floes according to the invention is prepared prior to its addition to the papermaking furnish. This can be done in batch or continuous mode. The filler concentration in such slurries is typically less than 80% by mass. It is more typically between 5% and 65% by mass.

The batch process can consist of a large mixing tank and an overhead propeller mixer. The filler slurry is fed into the mixing tank and the desired amount of the first flocculating agent is fed to the slurry under continuous mixing. Mixing the slurry with the flocculant for a sufficient amount to evenly distribute the first flocculating agent throughout the system The amount of time, typically lasting about 10 to 60 seconds, depends on the mixing energy used. The desired amount of the second flocculating agent is then added while stirring at a mixing rate sufficient to destroy the filler floes, typically increasing the mixing time from a few seconds to a few minutes, depending on the mixing energy used. The microparticles are added to the filler slurry before, simultaneously with and/or after the addition of the first flocculating agent, and prior to the second flocculating agent. Optionally, particles are added after the second flocculating agent. The addition of particulates increases the shear stability of the filler floes and narrows the particle size distribution of the floes. When a filler floc of a suitable particle size distribution is obtained, the mixing speed is lowered to the level at which the floc is stabilized. This batch of flocculated filler is then transferred to a larger mixing tank while being thoroughly mixed to keep the filler floes uniformly suspended in the dispersion. The flocculated packing is pumped from the mixing tank pump to the papermaking furnish.

In a continuous process, if necessary, the desired amount of the first flocculating agent is pumped into a tube containing the packing and mixed using an in-line static mixer. The length of the tube or mixing vessel sufficient to allow the filler to be thoroughly mixed with the flocculant can be included prior to injecting the appropriate amount of the second flocculating agent. If necessary, the second flocculating agent is then pumped into a tube containing the packing and mixed using an in-line static mixer. If necessary, the particles are pumped into a tube containing the filler slurry and mixed using an in-line static mixer. The addition point is before, concurrently with, and/or after pumping the first flocculating agent, and prior to the addition of the second flocculating agent. Optionally, the particles are pumped after the second flocculation reagent. The addition of particulates increases the shear stability of the filler floes and narrows the particle size distribution of the floes. High speed mixing is then required to obtain the desired particle size distribution of the filler floes. Adjusting the shear rate or mixing time of the mixing device controls the floc size distribution. A continuous process will help to use an adjustable shear rate in a fixed volume device. One such device is described in U.S. Patent 4,799,964. The device is a variable speed centrifugal pump that operates as a mechanical shearing device that does not have pumping capability when operating at a back pressure that exceeds its closing pressure. Other suitable shearing devices include nozzles with adjustable pressure drop in fixed volume containers, turbine emulsifiers or adjustable speed high intensity mixers. After shearing, the flocculating filler slurry is fed directly into the papermaking furnish.

In the batch and continuous processes described above, filters or screens can be used To remove oversized filler floes. This eliminates potential machine operability and paper quality issues resulting from the inclusion of large filler floes in paper or board.

In one embodiment, the filler floe has a median particle size of at least 10 [mu]m. In one embodiment, the filler floe has a median particle size between 10 μm and 100 μm. In one embodiment, the filler floc median particle size is between 10 [mu]m and 70 [mu]m.

In at least one embodiment, the invention is practiced using at least one of the compositions and/or methods described in U.S. Patent Application Serial No. 12/975,596. In at least one embodiment, the invention is practiced using at least one of the compositions and/or methods described in U.S. Patent No. 8,088,213. In at least one embodiment, the invention is practiced using at least one of the compositions and/or methods described in U.S. Patent No. 8,172,983.

Example

The foregoing is a better understanding of the invention, and is not intended to limit the scope of the invention.

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. Stir for at least 30 seconds before adding any chemical additives. The agitator was an IKA ^® EUROSTAR digital overhead mixer and a R1342 50mm four-bladed propeller (both from IKA ^® Works, Wilmington, NC USA). The final floc size distribution was characterized by laser light scattering using a Malvern Mastersizer Micro from Malvern Instruments, Inc. (Southborough, MA USA). Analysis was performed using a polydisperse model and image 4PAD. This image exhibited a 1.60 real component and a 0 imaginary component for the refractive index of the filler and a refractive index of 1.33 for water as a continuous phase. The distribution quality is indicated by the volume-weighted median floc size, D( V, 0.5 ), and the distribution span, which are defined as follows:

Here, D( V, 0.1 ), D( V, 0.5 ), and D( V, 0.9 ) are respectively defined as diameters of filler flocs having a volume equal to or greater than 10%, 50%, and 90%. Smaller span values indicate a more uniform particle size distribution, which is believed to have better performance in papermaking. The values of D( V, 0.5 ) and span of each example are listed in Tables I and II.

Example 1

The filler used was a scalenohedral precipitated calcium carbonate (PCC) dry powder (available as Albacar HO from Specialty Minerals, Bethlehem, PA, USA). This PCC powder was dispersed in tap water at a 10% solids content. The slurry was stirred at 800 rpm and a small amount of sample was taken to measure the particle size distribution using a Malvern Mastersizer. Experimental use: a) Flocculating reagent DEV115 (which is a commercially available anionic sodium acrylate-acrylamide copolymer having a charge content of about 32 dL/g RSV and 29 mol%, available from Nalco, Naperville, Ill. , USA), b) flocculating reagent DEV125 (which is a commercially available cationic acrylamide-dimethylaminoethyl acrylate-methyl chloride grade 4 having a charge content of about 25 dL/g RSV and 10 mol%) Salt copolymers available from Nalco, Naperville, Ill., USA.), and c) particulate Nalco-8699 (a commercially available colloidal ceria dispersion available from Nalco, Naperville, Ill., USA.).

The results in Table 1 show that the untreated PCC has 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, 1.5 lb/ton of Nalco DEV 115 was slowly added to the slurry using a syringe, followed by slow addition of 1.0 lb/ton of Nalco DEV 125 using another syringe. After the addition of the DEV 125, a portion of the filler sample was taken for particle size measurement (time = 0 minutes), and then the stirring rate was increased to 1500 rpm for 8 minutes. Samples were taken at intervals of two minutes to measure the particle size distribution (time = 2, 4, 6 and 8 minutes). This shearing is carried out for the purpose of evaluating the stability of the filler floes. The results are shown in Table 1.

Example 2

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. Add 0.5 lb/ton of Nalco-8699 before adding DEV115.

Example 3

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. Add 1.0 lb/ton of Nalco-8699 before adding DEV115.

Example 4

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. Add 1.5 lbs/ton of Nalco-8699 before adding DEV115.

Example 5

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. After adding DEV115, but before adding DEV125, add 1.0 lb/ton of Nalco-8699.

Example 6

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. After adding DEV125, 1.0 lb/ton of Nalco-8699 was added.

Example 7

Experiment 1 was repeated with the microparticles as a component of the treatment protocol. 1.0 lb/ton of Nalco-8699 was premixed with 1.5 lbs/ton of DEV115 prior to addition to the filler slurry, followed by the addition of DEV125.

The results in Table I show that in the case of Nalco-8699 microparticles, in the flocculation scheme, whether it is added before the anionic flocculating agent, after the anionic flocculating agent, premixed with the anionic flocculating agent or at the cationic After the flocculating agent is added, the flocculation and shear stability of the obtained filler floc are significantly improved.

Example 8

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

After mixing 10% GCC slurry at 800 rpm for 30 seconds, 1.5 lbs/ton of Nalco DEV120 was added to the slurry, followed by a slow addition of 0.75 lbs/ton of Nalco DEV115 to the slurry using a syringe, and finally a slow addition of 0.60 pounds using another syringe. /t Nalco DEV125. After the addition of the DEV 125, a portion of the filler sample was taken for particle size measurement (time = 0 minutes), and then the stirring rate was increased to 1500 rpm for 8 minutes. Samples were taken at intervals of two 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 the microparticles as a component of the treatment protocol. Add 0.5 lb/ton of Nalco-8699 before adding DEV115.

Example 10

Experiment 8 was repeated with the microparticles as a component of the treatment protocol. Add 1.0 lb/ton of Nalco-8699 before adding DEV115.

Example 11

Experiment 8 was repeated with the microparticles as a component of the treatment protocol. After adding DEV115, but before DEV125, add 1.0 lb/ton of Nalco-8699.

Example 12

Experiment 8 was repeated with the microparticles as a component of the treatment protocol. After adding DEV125, 1.0 lb/ton of Nalco-8699 was added.

Example 13

Experiment 8 was repeated with the microparticles as a component of the treatment protocol. 1.0 lb/ton of Nalco-8699 was premixed with 0.75 lbs/ton of DEV115 prior to addition to the filler slurry, followed by the addition of DEV125.

The results in Table II show that in the case of Nalco-8699 microparticles, in the flocculation scheme, whether it is added before the anionic flocculating agent, after the anionic flocculating agent, premixed with the anionic flocculating agent or at the cationic After the flocculating agent is added, the flocculation and shear stability of the obtained filler floc are significantly improved.

Although the invention may be embodied in many different forms, the present invention is described in detail herein. Specific preferred embodiments of the invention. The invention is exemplified by the principles of the invention, and is not intended to limit the invention. All patents, patent applications, scientific papers, and any other reference materials referred to herein are incorporated by reference in their entirety. Furthermore, the 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 also specifically excludes any or all of the various embodiments described herein and/or incorporated herein.

The above disclosure is intended to be illustrative and not exhaustive. This specification will present many variations and alternatives to the general practitioner. All such alternatives and variations are intended to be included within the scope of the patent application, the term "comprise" means "including (but not limited to)". Other equivalents to the specific embodiments described herein will be recognized by those skilled in the art, and such equivalents are also intended to be covered by the scope of the claims.

All ranges and parameters disclosed herein are to be understood as inclusive of any and all sub- For example, the specified range of "1 to 10" shall be considered to include any and all subranges between the minimum 1 and the maximum 10 (and including the endpoints); that is, all subranges shall have a minimum of 1 Or starting with greater than 1 (eg 1 to 6.1) and ending with a maximum of 10 or less than 10 (eg 2.3 to 9.4, 3 to 8, 4 to 7), and finally to each number 1, 2 contained in the range , 3, 4, 5, 6, 7, 8, 9 and 10. All percentages and ratios are by weight unless otherwise stated.

This completes the description of the preferred and alternative embodiments of the invention. Other equivalents to the specific embodiments described herein will be apparent to those skilled in the art.

Claims (15)

A method of preparing a stable dispersion of flocculating filler particles having a specific particle size distribution for use in a papermaking process, comprising: a) providing an aqueous dispersion of filler particles; b) being sufficient to uniformly mix in the dispersion without causing the Adding a first flocculating agent to the dispersion, such as the amount of significant flocculation of the filler particles, and the first flocculating agent is amphoteric; c) before, simultaneously with and/or after the addition of the first flocculating agent, and adding a second Prior to flocculating the reagent, the microparticles are added to the dispersion in an amount insufficient to cause significant flocculation of the filler particles; d) to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent Adding the second flocculating agent, wherein the second flocculating agent has a charge opposite to the net charge of the first amphoteric flocculating agent; e) shearing the flocculating dispersion to obtain a dispersion of the filler floc having the desired particle size And f) flocculation of the filler particles prior to the addition of the filler particles to the papermaking material, and wherein no papermaking stock is present during the flocculation. The method of claim 1, wherein the filler floes have a median particle size of from 10 to 100 μm. The method of claim 1, wherein the filler is selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, and magnesium hydroxide, and mixtures thereof . The method of claim 1, wherein the first flocculating agent has a net anionic charge. The method of claim 4, wherein the second flocculating agent is cationic, selected from the group consisting of (meth)acrylamide and dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM) or its dimethyl sulfate, A Copolymers and terpolymers of the quaternary ammonium form prepared from chloro or benzyl chloride, and mixtures thereof. The method of claim 5, wherein the second flocculating agent is acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10 to 50 mol% and at least RSV of 15dL/g. The method of claim 4, wherein the second flocculating agent is a homopolymer of diallyldimethylammonium chloride having an RSV of from 0.1 to 2 dL/g. The method of claim 1, further comprising adding one or more particulates to the flocculation dispersion after the addition of the second flocculating agent. The method of claim 1, wherein the filler is dispersed in an anionic form and a low molecular weight cationic aggregating agent is added to the dispersion to at least partially neutralize its anionic charge prior to adding the first flocculating agent or particulate. . The method of claim 8 wherein the filler is dispersed in an anionic form and a low molecular weight cationic aggregating agent is added to the dispersion to at least partially neutralize its anionic charge prior to the addition of the first flocculating agent or particulate. . The method of claim 1, further comprising adding the swollen starch to the dispersion of the filler particles. The method of claim 11, wherein the swollen starch is added before and/or after the addition of the first flocculating agent and prior to the addition of the second flocculating agent. The method of claim 11, wherein the swollen starch is cationic, anionic, amphoteric or nonionic. The method of claim 11, wherein the swollen starch is a swollen starch-latex composition. The method of claim 1, wherein the microparticles are one selected from the group consisting of enamel materials, cerium oxide-based particles, cerium oxide microgels, colloidal cerium oxide, and Cerium oxide sol, cerium oxide gel, polysilicate, cationic cerium oxide, aluminosilicate, polyaluminum silicate, borosilicate, polyborate, zeolite, and synthetic or naturally occurring Expanded clay, anionic polymeric microparticles, cationic polymeric microparticles, amphoteric organic polymeric microparticles, and any combination thereof.