KR102134248B1 - Prefloccultation of fillers used in papermaking - Google Patents

Abstract

A method of preparing a stable dispersion of agglomerated filler particles for use in a papermaking process includes the use of microparticles before, simultaneously, and/or after adding the first agglomeration agent to the aqueous dispersion of filler particles, followed by second agglomeration. Formulations are added to the dispersion, and additionally formed filler floes are optionally sheared to the desired particle size to form a shear resistant filler floc with an adjustable size distribution. In addition, a neutralizing coagulant can be added to the dispersion to partially or completely neutralize the charge of the filler before adding the microparticles and/or the first flocculating agent.

Description

Pre-filling of fillers used in papermaking {PREFLOCCULTATION OF FILLERS USED IN PAPERMAKING}

The present invention relates to the preflocculation of fillers used in papermaking, and the production of shear resistant filler floc having a defined and adjustable size distribution, especially in high content filler solids, is described.

Increasing the content of fillers in printing and writing papers is a great concern not only to improve product quality, but also to reduce raw material and energy costs. However, replacing cellulose fibers with fillers such as calcium carbonate and clay reduces the strength of the final sheet. Another problem with increased filler content is the increased difficulty in maintaining a uniform distribution of fillers across the three-dimensional sheet structure. A way to reduce these negative effects of increasing filler content is to pre-agglomerate the filler before adding it to the wet end entry system of the paper machine.

The definition of the term "pre-agglomeration" is to transform the filler particles into agglomerates through treatment with a coagulant and/or flocculant before adding the filler to the paper stock. The flocculation treatment and the shear force of the process determine the size distribution and stability of the floc before it is added to the paper stock. The chemical environment and high fluid shear rates present in modern high-speed paper require that the filler floes become stable and shear resistant. The floc size distribution provided by the pre-agglomeration treatment should increase filler content to minimize sheet strength reduction, minimize loss of optical efficiency from filler particles, and minimize negative effects on sheet uniformity and printability. . Moreover, 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 filler preagglomeration technology. However, filler flocks formed from only low molecular weight coagulants, including starches that are commonly used, tend to have a relatively small particle size that decomposes under the high shear force of the paper machine. Filler flocks formed by a single high molecular weight flocculant tend to have a wide particle size distribution that is difficult to control, and this particle size distribution is more likely at higher filler solids levels, mainly because of poor mixing of viscous flocculant solutions into the slurry. It gets worse. Therefore, there is a continuing need for improved preaggregation techniques.

The technology described in this paragraph is not intended to be an "prior art" to the present invention, unless any patents, publications or other information mentioned herein is specifically designated otherwise. In addition, this paragraph should not be construed to mean that a search has been made or that no other suitable information as defined in 37 C.F.R.§1.56(a) exists.

Summary of the invention

At least one embodiment relates to a method of making 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) adding the first cohesive agent to the dispersion in an amount sufficient to uniformly mix the dispersion with no significant agglomeration of the filler particles, the first cohesive agent being amphoteric; c) adding microparticles to the dispersion in an amount insufficient to result in significant agglomeration of the filler particles before, simultaneously and/or after adding the first flocculating agent, and before adding the second flocculating agent. To do; d) a second cohesive agent is added to the dispersion in an amount sufficient to initiate the agglomeration of the filler particles in the presence of the first cohesive agent, the second cohesive agent being added to the net charge of the first amphoteric cohesive agent. Carrying opposite charges; e) shearing the agglomerated dispersion to provide a dispersion of filler floes having a desired particle size; And f) agglomerating the filler particles before adding the filler particles to the papermaking raw material, wherein no papermaking raw material is present during the agglomeration.

The filler floc can have a medium particle size of 10-100 μm. The filler can 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 (meth)acrylamide, dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylamino Ethyl methacrylate (DEAEM), or copolymers and terpolymers of their quaternary ammonium form made of dimethyl sulfate, methyl chloride or benzyl chloride, and mixtures thereof. The second flocculating agent can be an acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10-50 mol% and an RSV of at least 15 dL/g and/or an RSV of 0.1-2 dL/g It may be a homopolymer of diallyl dimethyl ammonium chloride with. The method may further include adding the second coagulant, followed by adding one or more microparticles to the agglomerated dispersion. The filler can be anionicly dispersed and a low molecular weight, cationic coagulant is added to the dispersion to at least partially neutralize its anionic charge prior to the addition of the first flocculating agent or microparticles. Swollen starch can 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 are silicate materials, silica-based particles, silica microgels, colloidal silica, silica sol, silica gel, polysilicate, cationic silica, aluminosilicate, polyaluminosilicate, borosilicate, polyborosilicate, zeolite, and Synthetic or natural swelling clay, anionic polymeric microparticles, cationic polymeric microparticles, amphoteric organic polymeric microparticles, and any combination thereof.

At least one embodiment relates to a paper product incorporating a filler floc prepared as described herein.

The following definitions are provided to find out how terms are used in this application, particularly how the claims are to be interpreted. The composition of definitions is for convenience only, and is not intended to limit any definitions to any particular category. For the purposes of this application, the definitions of these terms are as follows:

A “ coagulant ” is a composition having a higher charge density and lower molecular weight than a coagulant, which, when added to a liquid containing finely divided suspension particles, destabilizes and aggregates solids through the mechanism of ionic charge neutralization. ).

“ Coagulant ” means a composition with low charge density and high molecular weight (greater than 1,000,000) which, when added to a liquid containing finely divided suspension particles, destabilizes and aggregates solids through the mechanism of interparticle bridging.

“ Aggregating agent ” means a composition that when added to a liquid destabilizes and aggregates colloidal and finely divided suspension particles in a liquid, and the coagulant and coagulant may be a coagulant.

" GCC " means pulverized calcium carbonate produced by crushing naturally occurring calcium carbonate rocks.

" PCC " means precipitated calcium carbonate produced synthetically.

“Fine particles” refers to particles with a size of 0.1 μm to 100 μm, because microparticles have a much larger surface-to-volume ratio than similar macroscale sized materials whose behavior can be significantly different. , Silicon, ceramics, glass, polymers, and metals.

If the above definitions or descriptions mentioned elsewhere in this application do not coincide (explicitly or implicitly) with the meanings commonly used in the dictionary or referred to in the material incorporated by reference into this application (explicit or implicit), this application and It is understood that the claims terminology in particular should not be construed according to the general definitions, dictionary definitions or definitions incorporated by reference, but should be interpreted according to the definitions or descriptions in this application. In light of the above, the term is only, if it is interpreted by a dictionary, i.e. the term is defined by Kirk-Othmer Encyclopedia of Chemical Technology, 5th Edition, (2005), (Published by Wiley, John & Sons, inc.) As can be understood, this definition will regulate how such terms should be defined in the claims.

At least one embodiment relates to a method of making a stable dispersion of agglomerated filler particles having a specific particle size distribution useful in papermaking processes. The first flocculating agent is uniformly mixed with the dispersion, but added to the aqueous dispersion of filler particles in an amount that does not result in any significant agglomeration of the filler particles and under such conditions. The microparticles are added to the dispersion either before, during or after the addition of the first flocculating agent. After both the first flocculating agent and microparticles are added, 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 and under such conditions. In at least one embodiment, the types of first and second agents and methods of their use, and/or addition, are in accordance with any and all methods and procedures described in U.S. Patent No. 8,088,213.

Optionally, the agglomerated dispersion can be sheared to provide a dispersion of filler floes with optimum particle size.

Microparticles have previously been used in papermaking processes, but their use in this way is very new. In some prior art processes, microparticles are added at the wet end to prevent loss of material from the fiber-filler mixture. However, in the present invention, microparticles are added to the dispersion before the dispersion of filler is brought into contact with the fibers used to make the paper.

In addition, the present invention aims to have an optimal high shear stability at the same time as a sharp particle size distribution, the method for producing a filler dispersion using the previous fine particles is a method for producing fine particles used (e.g., U.S. published patent applications) 2009/0267258 microparticles). Such a prior method used microparticles after the second (aggregation initiation) flocculation agent. In the present invention, microparticles are added to the dispersion before aggregation begins. This is because the present invention utilizes properties that are not known in the art of these microparticles.

Microparticles are known to facilitate agglomeration by strengthening the agglomeration of particles formed by strongly interacting with the agglomeration agent. Therefore, it is already known that they assist only one (shear strength) of two privileges (shear strength and particle size) of interest.

However, the present invention takes advantage of the newly discovered fact that microparticles can interact well with filler particles in the absence of any agglomeration. Without being bound by theory or intention, it is believed that the microparticles form very hard “anchor sites” on the surface of the filler particles. Because these anchorage sites are much harder than the aggregated polymer, the anchorage sites resist bending and hold the polymer aggregates more tightly on the filler particles than the aggregates held in place by the aggregation agent. Thus, the method of the present invention allows the use of microparticles to allow the other of the two privileges, thereby increasing the size of the aggregation.

In at least one embodiment, the microparticles include silicate materials and polymeric microparticles. Representative silicate materials are silica based particles, silica microgels, colloidal silica, silica sol, silica gel, polysilicates, cationic silica, aluminosilicates, polyaluminosilicates, borosilicates, polyborosilicates, zeolites, and synthetic or Contains natural swelling clay. Swelling clays include bentonite, hectorite, smectite, montmorillonite, nontronite, saponite, soconite, mormite, and aterpulsy. It can be attapulgite, and sepiolite. A suitable representative microparticle is the product PosiTEK 8699 (produced by Nalco Company (Naperville IL)).

Polymeric microparticles useful in the present invention include anionic, cationic, or amphoteric organic microparticles. These microparticles typically have limited solubility in water, can be crosslinked, and have a non-swelling particle size of less than 750 nm.

Anionic organic microparticles are described in US 6,524,439, by hydrolyzing acrylamide polymer microparticles, or (meth)acrylic acid and salts thereof, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl-(meth) Acrylates, vinylsulfonic acids, styrene sulfonic acids, maleic acids or other dibasic acids or salts thereof or mixtures thereof prepared by polymerizing anionic monomers. These anionic monomers are also nonionic monomers such as (meth)acrylamide, N-alkylacrylamide, N,N-dialkylacrylamide, methyl(meth)acrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.

Cationic organic microparticles are described in US 6,524,439, diallyldialkylammonium halide, acryloxyalkyltrimethylammonium chloride, (meth)acrylates of dialkylaminoalkyl compounds, and monomers as salts and quaterns thereof, and , N,N-dialkylaminoalkyl (meth)acrylamide, (meth)acrylamidopropyl trimethylammonium chloride, and N,N-dimethylaminoethyl acrylate produced by polymerization of monomers such as acid or quaternary salt Includes things. These cationic monomers are also nonionic monomers such as (meth)acrylamide, N-alkylacrylamide, N,N-dialkylacrylamide, methyl(meth)acrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.

Amphoteric organic microparticles are prepared by polymerizing a combination of 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.

Polymerization of the monomer in the organic microparticles is typically carried out in the presence of a multifunctional crosslinking agent. These crosslinking agents have been described in US 6,524,439 as having at least two double bonds, double bonds and reactive groups, or two reactive groups. Examples of these crosslinking agents are N,N-methylenebis(meth)acrylamide, polyethylene glycol di(meth)acrylate, N-vinyl acrylamide, divinylbenzene, triallylammonium salt, and N-methylallylacrylamide glycidyl Dialdehydes such as (meth)acrylate, acrolein, methylolacrylamide, glyoxal, diepoxy compounds, and epichlorohydrin.

In an embodiment, the microparticle dosage is 0.2 to 8 lb/ton of filler treated. In an embodiment, the microparticle dosage is 0.5 to 4.0 lb/ton of filler treated. These doses represent active microparticle pounds per 2000 pounds of dried filler.

In at least one embodiment, the method also includes contacting the filler particles with swollen starch. If the starch slurry is cooked in a steam cooker under controlled temperature (and optionally controlled pH) conditions, as described in U.S. Pat.Nos. 2,805,966, 2,113,034, 2,328,537, and 5,620,510, starch It can absorb large amounts of water without bursting silver. 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 swelled starch is a crosslinked starch, such as one or more of those 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 according to any of the swollen starch-latex compositions and methods described in US patent application 2010/0078138.

As an example, starch-latex compositions swollen with or without co-additives are suitably prepared in a batch or jet cooker, or by mixing a suspension of starch and latex with hot water. For the starch presented, swelling is performed under controlled conditions of temperature, pH, mixing and mixing time to avoid rupture of the swollen starch granules. The composition is quickly added to the filler suspension, which is then introduced to the paper furnish at a certain point in front of the head box of the paper machine or at such a head box. During the drying operation, retained, swollen starch granules with filler particles will rupture, thus causing the amylopectin and amylose macromolecules to dissociate and bind to the solid component of the sheet.

Combinations of swollen starch and latex can be used in treating fillers in an acidic, neutral or alkaline environment. In at least one embodiment, the filler is treated with a swollen starch-latex composition, prepared with or without a co-additive, and then added to the paper slurry. The filler particles agglomerate, and the agglomerated filler particles adsorb on the surfaces of fines and fibers, causing rapid agglomeration in the stock.

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

In at least one embodiment, the at least one swollen starch composition (including the swollen starch-latex composition) is added prior to or at the same time as the microparticles are added, or before the first flocculation agent is added or the microparticles are added. At the same time as it is added, it is added to the filler dispersion before the second flocculating agent is added, or at the same time as the microparticles are added, after the second flocculating agent is added, and any combination thereof.

Fillers useful in the present invention are well known and commercially available. Fillers will typically include any inorganic or organic particles or pigments used to increase opacity or brightness, to increase smoothness, or to reduce the cost of paper or cardboard sheets. Representative fillers include calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, and magnesium hydroxide. Calcium carbonate includes GCC in the form of a dried or dispersed slurry, choke, PCC in any morphology, and PCC in the form of a dispersed slurry. Some examples of GCC and PCC slurries are provided in co-pending U.S. Patent Application Serial No. 12/323,976. 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 significant anionic charge to the calcium carbonate particles. Kaolin clay slurry can also be dispersed using polyacrylic acid polymers or sodium polyphosphate.

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

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

The first flocculation agent is preferably a cationic polymer flocculant when used with cationically charged fillers and anionic when used with cationically charged fillers. However, the first flocculating agent can be anionic, nonionic, zwitterionic, or amphoteric, as long as it will be uniformly mixed into a high content solid slurry without causing significant flocculation.

The definition "without causing significant aggregation" is that there is no aggregation of fillers in the presence of the first aggregation agent, or less than those produced upon addition of the second aggregation agent, and no formation of unstable flocs under moderate shear conditions. . A suitable shear is defined as the shear provided by mixing a 300 ml sample into a 600 ml beaker using an IKA RE16 stirring motor at 800 rpm with a 4 cm diameter 4 blade turbine impeller. These flyers should be similar to those present in modern papermaking entry systems.

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

Polymeric flocculants are typically by vinyl addition polymerization of one or more cationic, anionic or nonionic monomers, by copolymerization of one or more cationic monomers with one or more nonionic monomers, one or more anionic monomers and one or more nonionics By copolymerization of the monomers, one or more cationic monomers to produce an amphoteric polymer, one or more anionic monomers, and optionally by copolymerization of one or more nonionic monomers, or one or more zwitteryi to form zwitterionic polymers Prepared by polymerization of an ionic monomer 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 to impart cationic or anionic charge to the zwitterionic polymer. Suitable flocculants generally have a charge content of less than 80 mole percent, often less than 40 mole percent.

Although cationic polymer flocculants can be formed using cationic monomers, it is also possible to prepare cationic charged polymers by reacting certain nonionic vinyl addition polymers. Polymers of this type include those produced through the reaction of polyacrylamide to produce Mannich derivatives, and dimethylamine and formaldehyde.

Likewise, although anionic polymer flocculants can be formed using anionic monomers, it is also possible to modify certain nonionic vinyl addition polymers to form anionic charged polymers. Polymers of this type include, for example, those obtained by hydrolysis of polyacrylamide.

Flocculants can be prepared in solid form as a water-in-oil emulsion, or as a dispersion in water. Representative cationic polymers include (meth)acrylamide, dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), and diethylaminoethyl methacrylate (DEAEM) ), or terpolymers and copolymers of their quaternary ammonium form made of dimethyl sulfate, methyl chloride or benzyl chloride. Representative anionic polymers are acrylamides and/or copolymers of sodium acrylate and/or 2-acrylamido 2-methylpropane sulfonic acid (AMPS) or acrylamide homopolymers that are hydrolyzed to convert a portion of the acrylamide groups to acrylic acid. It includes.

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

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

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

“RSV” as used herein refers to the reduced specific viscosity. In a series of substantially linear, well-solvated polymer homologues, "reduced specific viscosity (RSV)" measurements for diluted polymer solutions are described in Determination of Molecular Weights, by Paul J. Flory, pages 266-316, Principles of Polymer Chemistry , Cornell University Press, Ithaca, NY, Chapter VII (1953)]. RSV is measured at a given polymer concentration and temperature and is calculated as follows:

RSV = [(η/η ₀ )-1]/c (η = viscosity of the polymer solution, η ₀ = viscosity of the solvent at the same temperature, and c = polymer concentration in the solution).

The unit of concentration "c" is (gram/100ml or g/deciliter). Therefore, the unit of RSV is dL/g. Unless otherwise specified, 1.0 mole of sodium nitrate solution is used for RSV measurement. The polymer concentration in this solution is 0.045 g/dL. RSV is measured at 30°C. Viscosities η and η ₀ were measured using a Cannon Ubbelohde semi-micro dilution viscometer, size 75. The viscometer was mounted in a completely vertical position in a thermostat adjusted to 30 ± 0.02°C. A typical error inherent in RSV calculations for the polymers described herein is about 0.2 dL/g. When two polymer homologues in the series have similar RSVs, this is an indication that the two polymer homologues have similar molecular weights.

As discussed above, the first flocculation agent is added in an amount sufficient to uniformly mix into the dispersion without causing significant flocculation of filler particles. In an embodiment, the first coagulant dosage is 0.2 to 6.0 lb/ton of filler to be treated. In an embodiment, the coagulant dosage is 0.4 to 3.0 lb/ton of filler to be treated. For the purposes of the present invention, "lb/ton" is a unit of dosage that means pounds of active polymer (coagulant or flocculant) per 2,000 pounds of filler.

The second flocculating agent can be any material capable of initiating flocculation of the filler in the presence of the first flocculating agent. In an embodiment, the second flocculating agent is selected from fine particles, coagulants, flocculants and mixtures thereof.

Suitable coagulants generally have lower molecular weights than flocculants and have high density cationic charge groups. Coagulants useful in the present invention are well known and commercially available. They can be inorganic or organic. Representative inorganic coagulants, alum, sodium aluminate, polyaluminum chloride or PAC (may also be referred to as aluminum chlorohydroxide, aluminum hydroxide chloride and polyaluminum hydroxychloride), sulfated polyaluminum chloride, polyaluminum silica Sulfate, ferric sulfate, and ferric chloride, and the like, and blends thereof.

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

Polyfunctional amines and ethylenedichloride, such as ethylene dichloride and ammonia, or polymers of ethylene dichloride and dimethylamine, diethylenetriamine, tetraethylenepentamine, and hexamethylenediamine, with or without addition of ammonia. Or condensation polymers of polyfunctional acids such as adipic acid, and polymers prepared by condensation reactions such as melamine formaldehyde resins.

Additional coagulants are (meth)acrylamide, diallyl-N,N-2 substituted ammonium halide, dimethylaminoethyl methacrylate and quaternary ammonium salts thereof, dimethylaminoethyl acrylate and quaternary ammonium salts thereof, Methacrylic amidopropyl trimethylammonium chloride, diallylmethyl (beta-propionamido) ammonium chloride, (beta-methacryloyloxyethyl) trimethyl ammonium methyl sulfate, quaternized polyvinyllactam, vinylamine, and reacted And cationic charged vinyl addition polymers such as polymers, copolymers, and terpolymers of acrylamide or methacrylamide to produce Mannich or quaternary Mannich derivatives. Suitable quaternary ammonium salts can be prepared using methyl chloride, dimethyl sulfate or benzyl chloride. The terpolymer may include anionic monomers such as acrylic acid or 2-acrylamido 2-methylpropane sulfonic acid as long as the overall charge on the polymer is cationic. The molecular weight of both these vinyl addition polymers and condensation polymers ranges from a low range of hundreds to a high range of millions.

Other polymers useful as second flocculation agents include cationic, anionic or amphoteric polymers whose chemical properties are described above as flocculants. 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 additional second flocculating agents. In an embodiment, one or more fine particles are added to the agglomerated filler slurry after the second coagulant is added.

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 an embodiment, the second coagulant dosage is 0.2 to 8.0 lb/ton of filler to be treated. In an embodiment, the second component dose is 0.5 to 6.0 lb/ton of filler to be treated.

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

In an embodiment, the second aggregation agent and the first aggregation agent are oppositely charged.

In an embodiment, the first aggregation agent is cationic and the second aggregation agent is anionic.

In an embodiment, the first flocculating agent is selected from a copolymer of acrylamide and dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof.

In an embodiment, the first flocculating agent is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) with a cationic charge content of 5-50 mol% and RSV >15 dL/g.

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

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

In an embodiment, the first aggregation agent is anionic and the second aggregation agent is cationic.

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

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

In an embodiment, the second flocculating agent is an epichlorohydrin-dimethylamine (EPI-DMA) copolymer, an EPI-DMA copolymer crosslinked with ammonia and a homopolymer of diallyl-N,N-2 substituted ammonium halide. It is selected from the group consisting of.

In an embodiment, the second flocculating agent is a homopolymer of diallyl dimethyl ammonium chloride with an RSV of 0.1-2 dL/g.

In an embodiment, the second flocculating agent is selected from a copolymer of acrylamide and dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof.

In an embodiment, the second flocculating agent is a copolymer of acrylamide and dimethylaminoethyl acrylate (DMAEA) with a cationic charge content of 5-50 mol% and RSV >15 dL/g.

Dispersions of filler flocs according to the invention are prepared before adding them to the papermaking stock. This can be done in a batch or continuous fashion. The filler concentration in these slurries is typically less than 80% by mass. More typically, it is 5 to 65 mass%.

The batch process can consist of a large mixing tank with an overhead propeller mixer. The filler slurry is filled into the mixing tank, and under continuous mixing, the desired amount of the first flocculating agent is supplied to the slurry. The slurry and flocculant are mixed for an amount of time sufficient to uniformly distribute the first flocculation agent throughout the system, typically for about 10 to 60 seconds, depending on the mixing energy used. Thereafter, depending on the mixing energy used, the desired amount of the second flocculating agent is added with stirring at a mixing time sufficient to crush the filler floc at increasing mixing time, typically a few seconds to several minutes. The fine particles are added to the filler slurry before adding the first flocculating agent, simultaneously with adding the first flocculating agent, and/or after adding the first flocculating agent, and before adding the second flocculating agent. Optionally, fine particles are added after the second flocculating agent. The addition of fine particles increases the shear stability of the filler floe and narrows the particle size distribution of the floe. Once the proper size distribution of filler floes is obtained, the mixing rate is lowered to a level where the flocs are stable. The batch of these agglomerated fillers is then transferred to a larger mixing tank with sufficient mixing to maintain a uniformly suspended filler floc in the dispersion. Aggregated filler is pumped from this mixing tank to the paper stock.

In a continuous process, the desired amount of the first flocculating agent is pumped to the pipe containing the filler and, if necessary, mixed with an in-line static mixer. Pipes or mixing vessels of sufficient length to allow sufficient mixing of the filler and flocculant may be included prior to injection of the appropriate amount of the second flocculant. Thereafter, the second cohesive agent is pumped to the pipe containing the filler and, if necessary, mixed with a stationary mixer. The microparticles are pumped into a pipe containing the filler slurry and, if necessary, mixed with a stationary mixer. The time of addition is before, simultaneously, and/or after pumping the first flocculating agent, and before adding the second flocculating agent. Optionally, the fine particles are pumped after the second flocculating agent. The addition of fine particles increases the shear stability of the filler floe and narrows the particle size distribution of the floe. Accordingly, high speed mixing is required to obtain the desired size distribution of the filler floes. The floc size distribution can be adjusted by adjusting either the shear rate or the mixing time of the mixing device. The continuous process would be suitable for use with adjustable shear rates in a fixed volume device. One such device is described in US Pat. No. 4,799,964. The device is a speed-adjustable centrifugal pump that acts as a mechanical shearing device without pumping capability when operated at back pressure exceeding its shut off pressure. Other suitable shearing devices include nozzles with adjustable pressure drop, turbine type emulsifying devices or high-strength mixers of adjustable speed in fixed volume vessels. After shearing, the aggregated filler slurry is fed directly to the paper stock.

In both the batch and continuous processes described above, filters or screens can be used to remove filler plugs that are too large in size. This eliminates potential machine runability and paper quality problems due to the inclusion of many filler flocks in paper or cardboard.

In an embodiment, the median particle size of the filler flux is at least 10 μm. In an embodiment, the median particle size of the filler floes is 10-100 μm. In an embodiment, the median particle size of the filler floes is 10 to 70 μm.

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 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 US Pat. No. 8,172,983.

Example

The above may 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.

Experimental method

In the filler agglomeration experiment, the filler slurry was diluted with tap water to 10% solids, and 300 mL of this diluted slurry was placed in a 500 mL glass beaker. Stirring was performed for at least 30 seconds before adding any chemical additives. The stirrer was an IKA® EUROSTAR digital overhead mixer with R1342, 50 mm, four-blade propeller (both available from IKA® Works, Inc. (Wilmington, NC USA). ). The final floc size distribution was characterized by laser light scattering using a Mastersizer Micro from Malvern Instruments Ltd. (Southborough, MA USA). Analysis was performed using a polydispersity model and presentation 4PAD. This presentation estimates a refractive index of 1.33 for the refractive index of the filler, 1.60 real components and 0 image components and water as a continuous phase. The quality of the distribution is indicated by the volume-weighted median floc size, D(V,0.5), and the span of the distribution. Spans are defined as follows:

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

Example One

The filler used was a precipitated calcium carbonate (PCC) dry powder of scalenohedral (available as Albacar HO from Specialty Minerals Inc. (Bethlehem, PA, USA)). The PCC powder was dispersed as 10% solids in tap water. The slurry was stirred under 800 rpm, and a small amount of sample was taken to measure the particle size distribution by using a Malvern Mastersizer. The experiment a) a commercially available anionic sodium acrylate with a RSV of about 32 dL/g and a charge content of 29 mol%, available from the flocculation agent DEV115 (which is available from Nalco Company (Naperville, Ill., USA)) Acrylamide copolymer), b) a commercially available cation having an RSV of about 25 dL/g and a charge content of 10 mol%, available from the flocculation agent DEV125 (which is available from Nalco Company (Naperville, Ill., USA)) Sex acrylamide-dimethylaminoethyl methacrylate-methyl chloride quaternary salt copolymer), and c) microparticles Nalco-8699 (which is a commercially available colloid available from Nalco Company (Naperville, Ill., USA)) Silica dispersion).

The results in Table I show that the untreated PCC has a monomodal particle size distribution with a median particle size of 3.75 μm and a span of 1.283. After 30 seconds of mixing of 10% PCC slurry at 800 rpm, 1.5 lb/ton of Nalco DEV115 was slowly added to the slurry using a syringe, and then another syringe was used to slowly add 1.0 lb/ton of Nalco DEV125. Was added. After adding DEV125, one filler sample was taken for particle size measurement (time = 0 min), then the stirring speed was increased to 1500 rpm and held for 8 min. Samples were taken every 2 minutes to measure particle size distribution (times =2, 4, 6 and 8 minutes). The shearing was done for the purpose of evaluating the stability of the filler floe. Results are shown in Table I.

Example 2

Experiment 1 was repeated with microparticles as one component of the treatment program. Before adding DEV115, 0.5 lb/ton Nalco-8699 was added.

Example 3

Experiment 1 was repeated with microparticles as one component of the treatment program. Before adding DEV115, 1.0 lb/ton Nalco-8699 was added.

Example 4

Experiment 1 was repeated with microparticles as one component of the treatment program. Before adding DEV115, 1.5 lb/ton Nalco-8699 was added.

Example 5

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

Example 6

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

Example 7

Experiment 1 was repeated with microparticles as one component of the treatment program. 1.0 lb/ton Nalco-8699 and 1.5 lb/ton DEV115 were premixed before being added to the filler slurry, followed by DEV125.

Table I.

Characterized by particle size distribution of PCC (precipitated calcium carbonate) flocs formed by different chemical programs and sheared at 1500 rpm for various times.

The results in Table I show that when Nalco-8699 microparticles are used in the flocculation program, they may be added before the anionic flocculation agent, added after the anionic flocculation agent, premixed with the anionic flocculation agent, or after the cationic flocculation agent. Whether added to or not, indicates that both the filler aggregation and the shear stability of the formed filler flocs have improved significantly.

Example 8

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

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

Example 9

Experiment 8 was repeated with microparticles as one component of the treatment program. 0.5 lb/ton Nalco-8699 was added before the addition of DEV115.

Example 10

Experiment 8 was repeated with microparticles as one component of 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 component of the treatment program. 1.0 lb/ton Nalco-8699 was added after the addition of DEV115, but before the addition of DEV125.

Example 12

Experiment 8 was repeated with microparticles as one component of 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 component of the treatment program. 1.0 lb/ton Nalco-8699 and 0.75 lb/ton DEV115 were premixed before adding the filler slurry, followed by DEV125.

Table II.

Characterized by particle size distribution of GCC (pulverized calcium carbonate) flocs formed by different chemical programs and sheared at 1500 rpm for various times.

The results in Table II show that when Nalco-8699 microparticles are used in the flocculation program, they may be added before the anionic flocculation agent, added after the anionic flocculation agent, premixed with the anionic flocculation agent, or after the cationic flocculation agent. Whether added to or not, indicates that both the filler aggregation and the shear stability of the formed filler flocs have improved significantly.

The invention can be implemented in many different forms, but certain preferred embodiments of the invention are described in detail herein. This disclosure is an illustration of the principles of the invention, and is not intended to limit the invention to the specific embodiments illustrated. All patents, patent applications, scientific papers, and any other reference materials mentioned herein are incorporated by reference in their entirety. Moreover, the present invention encompasses any possible combination of some or all of the various embodiments described herein and/or included herein. In addition, the present invention encompasses any possible combination that specifically excludes one or some of the various embodiments described herein and/or included herein.

The above disclosure is intended to be illustrative, not exhaustive. This description will present many variations and alternatives to those skilled in the art. The term "comprising" is intended to include all of these alternatives and modifications within the scope of the claims meaning "including but not limited to". Those skilled in the art can recognize other equivalents for certain embodiments described herein that are also intended to cover equivalents by the claims.

It is understood that all ranges and variables disclosed herein encompass any subranges and all subranges included therein, and all numbers between endpoints. For example, the specified range "1 to 10" means any subrange and all subranges between a minimum value of 1 and a maximum value of 10 (including 1 and 10): that is, a minimum value of 1 or more (eg, 1 to 10) 6.1) all subranges beginning with a maximum value of 10 or less (e.g., 2.3 to 9.4, 3 to 8, 4 to 7) and finally each number 1, 2, 3, each of which falls within the range. It should be considered to include 4, 5, 6, 7, 8, 9, and 10. All percentages are by weight, unless otherwise specified.

This completes the detailed description of preferred and alternative embodiments of the invention. Those skilled in the art can recognize other equivalents for the specific embodiments described herein that are intended to cover the equivalents by the claims appended hereto.

Claims (15)

A method for preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process,
a) providing an aqueous dispersion of filler particles;
b) The first flocculating agent is added to the dispersion in an amount sufficient to uniformly mix it in the dispersion without causing significant flocculation of the filler particles, the first flocculating agent being amphoteric and having a net charge. step;
c) adding microparticles to the dispersion in an amount insufficient to result in significant agglomeration of the filler particles before, simultaneously and/or after adding the first flocculating agent, and before adding the second flocculating agent. To do;
d) a second cohesive agent is added to the dispersion in an amount sufficient to initiate the agglomeration of the filler particles in the presence of the first cohesive agent, the second cohesive agent having an opposite charge to the net charge of the first amphoteric cohesive agent step;
e) shearing the agglomerated dispersion to provide a dispersion of filler floc having a desired particle size; And
f) agglomerating the filler particles prior to adding the filler particles to the paper stock, but comprising no papermaking raw material during agglomeration,
A method in which the filler is anionicly dispersed and a cationic coagulant is added to the dispersion to partially or fully neutralize its anionic charge prior to the addition of the first flocculating agent or microparticles. The method of claim 1, wherein the filler flux has a median particle size of 10-100 μm. The filler of claim 1, wherein the filler consists of precipitated calcium carbonate, ground calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate and magnesium hydroxide, and mixtures thereof. Method selected from the group. The method of claim 1, wherein the first flocculating agent has a net anionic charge. The method according to claim 4, wherein the second flocculating agent is cationic, (meth)acrylamide, dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA). , Copolymers and terpolymers of their quaternary ammonium form formed of diethylaminoethyl methacrylate (DEAEM), or dimethyl sulfate, methyl chloride or benzyl chloride, and mixtures thereof. 6. The method of claim 5, wherein the second flocculating agent is an acrylamide-dimethylaminoethyl acrylate methyl chloride quaternary copolymer having a cationic charge of 10-50 mol% and an RSV of at least 15 dL/g. 5. The method of claim 4, wherein the second flocculating agent is a homopolymer of diallyl dimethyl ammonium chloride with RSV of 0.1-2 dL/g. A method for preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process,
a) providing an aqueous dispersion of filler particles;
b) The first flocculating agent is added to the dispersion in an amount sufficient to uniformly mix it in the dispersion without causing significant flocculation of the filler particles, the first flocculating agent being amphoteric and having a net charge. step;
c) adding microparticles to the dispersion in an amount insufficient to result in significant agglomeration of the filler particles before, simultaneously and/or after adding the first flocculating agent, and before adding the second flocculating agent. To do;
d) a second cohesive agent is added to the dispersion in an amount sufficient to initiate the agglomeration of the filler particles in the presence of the first cohesive agent, the second cohesive agent having an opposite charge to the net charge of the first amphoteric cohesive agent step;
e) after adding the second flocculating agent, adding one or more microparticles to the flocculated dispersion;
f) shearing the agglomerated dispersion to provide a dispersion of filler floc having a desired particle size; And
g) agglomerating the filler particles prior to adding the filler particles to the paper stock, but comprising no papermaking raw material during agglomeration,
A method in which the filler is anionicly dispersed and a cationic coagulant is added to the dispersion to partially or fully neutralize its anionic charge prior to the addition of the first flocculating agent or microparticles. A method for preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process,
a) providing an aqueous dispersion of filler particles;
b) The first flocculating agent is added to the dispersion in an amount sufficient to uniformly mix it in the dispersion without causing significant flocculation of the filler particles, the first flocculating agent being amphoteric and having a net charge. step;
c) adding microparticles to the dispersion in an amount insufficient to result in significant agglomeration of the filler particles before, simultaneously and/or after adding the first flocculating agent, and before adding the second flocculating agent. To do;
d) a second coagulant is added to the dispersion in an amount sufficient to initiate agglomeration of the filler particles in the presence of the first coagulant, the second coagulant having a charge opposite to the net charge of the first amphoteric coagulant. step;
e) adding the swollen starch to the dispersion of filler particles;
f) shearing the aggregated dispersion to provide a dispersion of filler floc having a desired particle size; And
g) A method comprising the step of agglomerating the filler particles before adding the filler particles to a paper stock, wherein no papermaking material is present during the agglomeration. 10. The method of claim 9, wherein the swollen starch is added before and/or after adding the first flocculating agent and before adding the second flocculating agent. 10. The method of claim 9, wherein the swollen starch is cationic, anionic, amphoteric or nonionic. 10. The method of claim 9, wherein the swollen starch is a swollen-starch-latex composition. The method of claim 1, wherein the fine particles are silicate material, silica-based particles, silica microgel, colloidal silica, silica sol, silica gel, polysilicate, cationic silica, aluminosilicate, polyaluminosilicate, borosilicate, polybo A method selected from the list consisting of silicates, zeolites, and synthetic or natural swelling clays, anionic polymeric microparticles, cationic polymeric microparticles, amphoteric organic polymeric microparticles, and any combinations thereof. A method for preparing a stable dispersion of agglomerated filler particles having a specific particle size distribution for use in a papermaking process,
a) providing an aqueous dispersion of filler particles;
b) adding the first cohesive agent to the dispersion in an amount sufficient to uniformly mix the dispersion with no significant agglomeration of the filler particles, the first cohesive agent being anionic;
c) adding microparticles to the dispersion in an amount insufficient to result in significant agglomeration of the filler particles before, simultaneously and/or after adding the first flocculating agent, and before adding the second flocculating agent. To do;
d) adding a second flocculating agent to the dispersion in an amount sufficient to initiate flocculation of the filler particles in the presence of the first flocculating agent, wherein the second flocculating agent is cationic;
e) shearing the aggregated dispersion to provide a dispersion of filler floc having a desired particle size; And
f) agglomerating the filler particles before adding the filler particles to the paper stock, but comprising no papermaking raw material during agglomeration,
A method in which the filler is anionicly dispersed and a cationic coagulant is added to the dispersion to partially or fully neutralize its anionic charge prior to the addition of the first flocculating agent or microparticles. delete