CA2698811C - Controllable filler prefloculation using a dual polymer system - Google Patents
Controllable filler prefloculation using a dual polymer system Download PDFInfo
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- CA2698811C CA2698811C CA2698811A CA2698811A CA2698811C CA 2698811 C CA2698811 C CA 2698811C CA 2698811 A CA2698811 A CA 2698811A CA 2698811 A CA2698811 A CA 2698811A CA 2698811 C CA2698811 C CA 2698811C
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/69—Water-insoluble compounds, e.g. fillers, pigments modified, e.g. by association with other compositions prior to incorporation in the pulp or paper
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/675—Oxides, hydroxides or carbonates
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
- D21H17/63—Inorganic compounds
- D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
- D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
- D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
- D21H21/18—Reinforcing agents
Abstract
A method of preparing a stable dispersion of flocculated filler particles for use in papermaking processes comprises sequential addition of high and low molecular weight flocculating agents to an aqueous dispersion of filler particles followed by shearing of the resultant filler flocs to the desired particle size resulting in shear resistant filler flocs with a defined and controllable size distribution.
Description
CONTROLLABLE FILLER PREFLOCULATION USING A DUAL POLYMER SYSTEM
TECHNICAL FIELD
This invention relates to the preflocculation of fillers used in papermaking, particularly, the production of shear resistant filler flocs with a defined and controllable size distribution at high filler solids is disclosed.
BACKGROUND OF THE INVENTION
Increasing the filler content in printing and writing papers is of great interest for improving product quality as well as reducing raw material and energy costs.
However, the substitution of cellulose fibers with fillers like calcium carbonate and clay reduces the strength of the finished sheet. Another problem when the filler content is increased is an increased difficulty of maintaining an even distribution of fillers across the three-dimensional sheet structure. An approach to reduce these negative effects of increasing filler content is to preflocculate fillers prior to their addition to the wet end approach system of the paper machine.
The term preflocculation means the modification of filler particles into agglomerates through treatment with coagulants and/or flocculants. The flocculation treatment and shear forces of the process determine the size distribution and stability of the flocs prior to addition to the paper stock. The chemical environment and high fluid shear rates present in modem high-speed papermaking require filler flocs to be stable and shear resistant. The floc size distribution provided by a preflocculation treatment should minimize the reduction of sheet strength with increased filler content, minimize the loss of optical efficiency from the filler particles, and minimize negative impacts on sheet uniformity and printability. Furthermore, the entire system must be economically feasible.
Therefore, the combination of high shear stability and sharp particle size distribution is vital to the success of filler preflocculation technology. However, filler flocs formed by a low molecular weight coagulant alone, including commonly used starch, tend to have a relatively small particle size that breaks down under the high shear forces of a paper machine. Filler flocs formed by a single high molecular weight flocculant tend to have a broad particle size distribution that is difficult to control, and the particle size distribution gets worse at higher filler solids levels, primarily due to the poor mixing of viscous flocculant solution into the slurry.
Accordingly, there is an ongoing need for improved preflocculation technologies.
. .
SUMMARY OF THE INVENTION
This invention is a method of preparing a stable dispersion of flocculated filler particles having a specific particle size distribution for use in papermaking processes comprising a) providing an aqueous dispersion of filler particles; b) adding a first flocculating agent to the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles; c) 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; and d) optionally shearing the flocculated dispersion to provide a dispersion of filler floes having the desired particle size.
This invention is also a method of making paper products from pulp comprising forming an aqueous cellulosic papermaking furnish, adding an aqueous dispersion of filler floes prepared as described herein to the furnish, draining the furnish to form a sheet and drying the sheet. The steps of forming the papermaking furnish, draining and drying may be carried out in any conventional manner generally known to those skilled in the art.
This invention is also a paper product incorporating the filler floes prepared as described herein.
In one embodiment, the preflocculation process of this invention introduces a viscous flocculant solution into an aqueous filler slurry having a high solids content without causing significant flocculation by controlling surface charge of the filler particles. This allows the viscous flocculant solution to be distributed evenly throughout the high solids slurry. The second component, which is much less viscous than the flocculant solution, is introduced to the system to form stable filler floes. This second component is a polymer with lower molecular weight and opposite charge compared to the flocculant. Optionally, a micropartiele can be added as a third component to provide additional flocculation and narrow the floe size distribution. The floe size distribution is controlled by applying extremely high shear for a sufficient amount of time to degrade the floe size to the desired value. After this time, the shear rate is lowered and the floe size is maintained. No significant reflocculation occurs.
TECHNICAL FIELD
This invention relates to the preflocculation of fillers used in papermaking, particularly, the production of shear resistant filler flocs with a defined and controllable size distribution at high filler solids is disclosed.
BACKGROUND OF THE INVENTION
Increasing the filler content in printing and writing papers is of great interest for improving product quality as well as reducing raw material and energy costs.
However, the substitution of cellulose fibers with fillers like calcium carbonate and clay reduces the strength of the finished sheet. Another problem when the filler content is increased is an increased difficulty of maintaining an even distribution of fillers across the three-dimensional sheet structure. An approach to reduce these negative effects of increasing filler content is to preflocculate fillers prior to their addition to the wet end approach system of the paper machine.
The term preflocculation means the modification of filler particles into agglomerates through treatment with coagulants and/or flocculants. The flocculation treatment and shear forces of the process determine the size distribution and stability of the flocs prior to addition to the paper stock. The chemical environment and high fluid shear rates present in modem high-speed papermaking require filler flocs to be stable and shear resistant. The floc size distribution provided by a preflocculation treatment should minimize the reduction of sheet strength with increased filler content, minimize the loss of optical efficiency from the filler particles, and minimize negative impacts on sheet uniformity and printability. Furthermore, the entire system must be economically feasible.
Therefore, the combination of high shear stability and sharp particle size distribution is vital to the success of filler preflocculation technology. However, filler flocs formed by a low molecular weight coagulant alone, including commonly used starch, tend to have a relatively small particle size that breaks down under the high shear forces of a paper machine. Filler flocs formed by a single high molecular weight flocculant tend to have a broad particle size distribution that is difficult to control, and the particle size distribution gets worse at higher filler solids levels, primarily due to the poor mixing of viscous flocculant solution into the slurry.
Accordingly, there is an ongoing need for improved preflocculation technologies.
. .
SUMMARY OF THE INVENTION
This invention is a method of preparing a stable dispersion of flocculated filler particles having a specific particle size distribution for use in papermaking processes comprising a) providing an aqueous dispersion of filler particles; b) adding a first flocculating agent to the dispersion in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles; c) 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; and d) optionally shearing the flocculated dispersion to provide a dispersion of filler floes having the desired particle size.
This invention is also a method of making paper products from pulp comprising forming an aqueous cellulosic papermaking furnish, adding an aqueous dispersion of filler floes prepared as described herein to the furnish, draining the furnish to form a sheet and drying the sheet. The steps of forming the papermaking furnish, draining and drying may be carried out in any conventional manner generally known to those skilled in the art.
This invention is also a paper product incorporating the filler floes prepared as described herein.
In one embodiment, the preflocculation process of this invention introduces a viscous flocculant solution into an aqueous filler slurry having a high solids content without causing significant flocculation by controlling surface charge of the filler particles. This allows the viscous flocculant solution to be distributed evenly throughout the high solids slurry. The second component, which is much less viscous than the flocculant solution, is introduced to the system to form stable filler floes. This second component is a polymer with lower molecular weight and opposite charge compared to the flocculant. Optionally, a micropartiele can be added as a third component to provide additional flocculation and narrow the floe size distribution. The floe size distribution is controlled by applying extremely high shear for a sufficient amount of time to degrade the floe size to the desired value. After this time, the shear rate is lowered and the floe size is maintained. No significant reflocculation occurs.
2 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a typical MCL time resolution profile recorded by Lasentec FBRM. At point one, the first flocculating agent is introduced into the slurry and the MCL
increases then quickly decreases under 800 rpm mixing speed, indicating that the filler flocs are not stable under the shear. At point two, the second flocculating agent is introduced, and the MCL also increases then decreases slightly under 800 rpm mixing. At point three, a microparticle is introduced and the MCL increases sharply then reaches a plateau, indicating that the filler flocs are stable under 800 rpm mixing. Once the shear is raised to 1500 rpm, MCL
starts to decrease.
DETAILED DESCRIPITION OF THE INVENTION
The fillers useful in this invention are well known and commercially available. They typically would include any inorganic or organic particle or pigment used to increase the opacity or brightness, reduce the porosity, or reduce the cost of the paper or paperboard sheet.
Representative fillers include calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, magnesium hydroxide, and the like. Calcium carbonate includes ground calcium carbonate (GCC) in a dry or dispersed slurry form, chalk, precipitated calcium carbonate (PCC) of any morphology, and precipitated calcium carbonate in a dispersed slurry form. The dispersed slurry forms of GCC or PCC are typically produced using polyacrylic acid polymer dispersants or sodium polyphosphate dispersants. Each of these dispersants imparts a significant anionic charge to the calcium carbonate particles. Kaolin clay slurries may also be dispersed using polyacrylic acid polymers or sodium polyphosphate.
In an embodiment, the fillers are selected from calcium carbonate and kaolin clay and combinations thereof.
In an embodiment, the fillers are selected from precipitated calcium carbonate, ground calcium carbonate and kaolin clay, and mixtures thereof The first flocculating agent is preferably a cationic polymeric flocculant when used with = 30 cationically charged fillers and anionic when used with anionically charged fillers. However, it can be anionic, nonionic, zwitterionic, or amphoteric as long as it will mix uniformly into a high solids slurry without causing significant flocculation.
As used herein, "without causing significant flocculation" means no flocculation of the filler in the presence of the first flocculating agent or the formation of flocs which are smaller
Figure 1 shows a typical MCL time resolution profile recorded by Lasentec FBRM. At point one, the first flocculating agent is introduced into the slurry and the MCL
increases then quickly decreases under 800 rpm mixing speed, indicating that the filler flocs are not stable under the shear. At point two, the second flocculating agent is introduced, and the MCL also increases then decreases slightly under 800 rpm mixing. At point three, a microparticle is introduced and the MCL increases sharply then reaches a plateau, indicating that the filler flocs are stable under 800 rpm mixing. Once the shear is raised to 1500 rpm, MCL
starts to decrease.
DETAILED DESCRIPITION OF THE INVENTION
The fillers useful in this invention are well known and commercially available. They typically would include any inorganic or organic particle or pigment used to increase the opacity or brightness, reduce the porosity, or reduce the cost of the paper or paperboard sheet.
Representative fillers include calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate, magnesium hydroxide, and the like. Calcium carbonate includes ground calcium carbonate (GCC) in a dry or dispersed slurry form, chalk, precipitated calcium carbonate (PCC) of any morphology, and precipitated calcium carbonate in a dispersed slurry form. The dispersed slurry forms of GCC or PCC are typically produced using polyacrylic acid polymer dispersants or sodium polyphosphate dispersants. Each of these dispersants imparts a significant anionic charge to the calcium carbonate particles. Kaolin clay slurries may also be dispersed using polyacrylic acid polymers or sodium polyphosphate.
In an embodiment, the fillers are selected from calcium carbonate and kaolin clay and combinations thereof.
In an embodiment, the fillers are selected from precipitated calcium carbonate, ground calcium carbonate and kaolin clay, and mixtures thereof The first flocculating agent is preferably a cationic polymeric flocculant when used with = 30 cationically charged fillers and anionic when used with anionically charged fillers. However, it can be anionic, nonionic, zwitterionic, or amphoteric as long as it will mix uniformly into a high solids slurry without causing significant flocculation.
As used herein, "without causing significant flocculation" means no flocculation of the filler in the presence of the first flocculating agent or the formation of flocs which are smaller
3 than those produced upon addition of the second flocculating agent and unstable under conditions of moderate shear. Moderate shear is defined as the shear provided by mixing a 300 ml sample in a 600 ml beaker using an IKA RE16 stirring motor at 800 rpm with a 5 cm diameter, four-bladed, turbine impeller. This shear should be similar to that present in the approach system of a modem paper machine.
Suitable flocculants generally have molecular weights in excess of 1,000,000 and often in excess of 5,000,000.
The polymeric flocculant is typically prepared 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, by copolymerization of one or more anionic monomers with one or more nonionic monomers, by copolymerization of one or more cationic monomers with one or more anionic monomers and optionally one or more nonionic monomers to produce an amphoteric polymer or by 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 cationic or anionic charge to the zwitterionic polymer. Suitable flocculants generally have a charge content of less than 80 mole percent and often less than 40 mole percent.
While cationic polymer flocculants may be formed using cationic monomers, it is also possible to react certain nonionic vinyl addition polymers to produce cationically charged polymers. Polymers of this type include those prepared through the reaction of polyacrylamide with dimethylamine and formaldehyde to produce a Mannich derivative.
Similarly, while anionic polymer flocculants may 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 prepared by the hydrolysis of polyacrylamide.
The flocculant may be prepared in the solid form, as an aqueous solution, as a water-in-oil emulsion, or as a dispersion in water. Representative cationic polymers include copolymers and terpolymers of (meth)acrylarnide with dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM) or their quaternary ammonium forms made with dirnethyl sulfate, methyl chloride or benzyl chloride. Representative anionic polymers include copolymers of acrylamide with sodium acrylate and/or 2-acrylarnido 2-methylpropane sulfonic
Suitable flocculants generally have molecular weights in excess of 1,000,000 and often in excess of 5,000,000.
The polymeric flocculant is typically prepared 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, by copolymerization of one or more anionic monomers with one or more nonionic monomers, by copolymerization of one or more cationic monomers with one or more anionic monomers and optionally one or more nonionic monomers to produce an amphoteric polymer or by 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 cationic or anionic charge to the zwitterionic polymer. Suitable flocculants generally have a charge content of less than 80 mole percent and often less than 40 mole percent.
While cationic polymer flocculants may be formed using cationic monomers, it is also possible to react certain nonionic vinyl addition polymers to produce cationically charged polymers. Polymers of this type include those prepared through the reaction of polyacrylamide with dimethylamine and formaldehyde to produce a Mannich derivative.
Similarly, while anionic polymer flocculants may 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 prepared by the hydrolysis of polyacrylamide.
The flocculant may be prepared in the solid form, as an aqueous solution, as a water-in-oil emulsion, or as a dispersion in water. Representative cationic polymers include copolymers and terpolymers of (meth)acrylarnide with dimethylaminoethyl methacrylate (DMAEM), dimethylaminoethyl acrylate (DMAEA), diethylaminoethyl acrylate (DEAEA), diethylaminoethyl methacrylate (DEAEM) or their quaternary ammonium forms made with dirnethyl sulfate, methyl chloride or benzyl chloride. Representative anionic polymers include copolymers of acrylamide with sodium acrylate and/or 2-acrylarnido 2-methylpropane sulfonic
4 acid (AMPS) or an aerylamide homopolymer that has been hydrolyzed to convert a portion of the acrylamide groups to acrylic acid.
In an embodiment, the flocculants have a RSV of at least 3 dl/g.
In an embodiment, the flocculants have a RSV of at least 10 dLig.
In an embodiment, the flocculants have a RSV of at least 15 dL/g.
As used herein, "RSV" stands for reduced specific viscosity. Within a series of polymer homologs which are substantially linear and well solvated, "reduced specific viscosity (RSV)"
measurements for dilute polymer solutions are an indication of polymer chain length and average molecular weight according to Paul J. Flory, in "Principles of Polymer Chemistry", Cornell University Press, Ithaca, NY, 1953, Chapter VII, "Determination of Molecular Weights", pp.
266-316. The RSV is measured at a given polymer concentration and temperature and calculated as follows:
RSV = [(n/n0)-1 ]/c where 11 = viscosity of polymer solution, no = viscosity of solvent at the same temperature and c = concentration of polymer in solution.
The units of concentration "c" are (grams/100 ml or g/deciliter). Therefore, the units of RSV are dlig. Unless otherwise specified, a 1.0 molar sodium nitrate solution is used for measuring RSV. The polymer concentration in this solvent is 0.045 g/dL. The RSV is measured at 30 C. The viscosities n and rio are measured using a Cannon Ubbelohmsemi-micro dilution viscometer, size 75. The viscometer is mounted in a perfectly vertical position in a constant temperature bath adjusted to 30 0.02 C. The typical error inherent in the calculation of RSV
for the polymers described herein is about 0.2 dLig. When two polymer hornologs within a series have similar RSV's that is an indication that they have similar molecular weights.
As discussed above, the first flocculating agent is added in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles. In an embodiment, the first flocculating agent dose is between 0.2 and 6.0 lb/ton of filler treated. In an embodiment, the flocculent dose is between 0.4 and 3.0 lb/ton of filler treated. For purposes of this invention, "lb/ton" is a unit of dosage that means pounds of active polymer (coagulant or flocculent) per 2,000 pounds of filler.
The second flocculating agent can be any material that can initiate the flocculation of filler in the presence of the first flocculating agent. In an embodiment, the second flocculating agent is selected from microparticles, coagulants, polymers having a lower molecular weight than the first flocculating agent and mixtures thereof Suitable rnicroparticles include siliceous materials and polymeric microparticles.
Representative siliceous materials include silica based particles, silica microgels, colloidal silica,
In an embodiment, the flocculants have a RSV of at least 3 dl/g.
In an embodiment, the flocculants have a RSV of at least 10 dLig.
In an embodiment, the flocculants have a RSV of at least 15 dL/g.
As used herein, "RSV" stands for reduced specific viscosity. Within a series of polymer homologs which are substantially linear and well solvated, "reduced specific viscosity (RSV)"
measurements for dilute polymer solutions are an indication of polymer chain length and average molecular weight according to Paul J. Flory, in "Principles of Polymer Chemistry", Cornell University Press, Ithaca, NY, 1953, Chapter VII, "Determination of Molecular Weights", pp.
266-316. The RSV is measured at a given polymer concentration and temperature and calculated as follows:
RSV = [(n/n0)-1 ]/c where 11 = viscosity of polymer solution, no = viscosity of solvent at the same temperature and c = concentration of polymer in solution.
The units of concentration "c" are (grams/100 ml or g/deciliter). Therefore, the units of RSV are dlig. Unless otherwise specified, a 1.0 molar sodium nitrate solution is used for measuring RSV. The polymer concentration in this solvent is 0.045 g/dL. The RSV is measured at 30 C. The viscosities n and rio are measured using a Cannon Ubbelohmsemi-micro dilution viscometer, size 75. The viscometer is mounted in a perfectly vertical position in a constant temperature bath adjusted to 30 0.02 C. The typical error inherent in the calculation of RSV
for the polymers described herein is about 0.2 dLig. When two polymer hornologs within a series have similar RSV's that is an indication that they have similar molecular weights.
As discussed above, the first flocculating agent is added in an amount sufficient to mix uniformly in the dispersion without causing significant flocculation of the filler particles. In an embodiment, the first flocculating agent dose is between 0.2 and 6.0 lb/ton of filler treated. In an embodiment, the flocculent dose is between 0.4 and 3.0 lb/ton of filler treated. For purposes of this invention, "lb/ton" is a unit of dosage that means pounds of active polymer (coagulant or flocculent) per 2,000 pounds of filler.
The second flocculating agent can be any material that can initiate the flocculation of filler in the presence of the first flocculating agent. In an embodiment, the second flocculating agent is selected from microparticles, coagulants, polymers having a lower molecular weight than the first flocculating agent and mixtures thereof Suitable rnicroparticles include siliceous materials and polymeric microparticles.
Representative siliceous materials include silica based particles, silica microgels, colloidal silica,
5 silica sols, silica gels, polysilicates, cationic silica, alumino silicates, polyaluminosilicates, borosilicates, polyborosilicates, zeolites, and synthetic or naturally occurring swelling clays. The swelling clays may be bentonite, hectorite, smectite, montmorillonite, nontronite, saponite, sauconite, morrnite, attapulgite, and sepiolite.
Polymeric microparticles useful in this invention include anionic, cationic, or amphoteric organic microparticles. These microparticles typically have limited solubility in water, may be crosslinked, and have an unswollen particle size of less than 750 nm.
Anionic organic microparticles include those described in US 6,524,439 and made by hydrolyzing acrylamide polymer microparticles or by polymerizing anionic monomers as (meth)acrylic acid and its salts, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic or other dibasic acids or their salts or mixtures thereof. These anionic monomers may also be copolymerized with nonionic monomers such as (meth)acrylamide, N-alkylacrylamides, N,N-dialkylactylamides, methyl (meth)acrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.
Cationic organic microparticles include those described in US 6,524,439 and made by polymerizing such monomers as diallyldialkylarnmonium halides, acryloxyalkyltrimethylammonium chloride, (meth)acrylates of dialkylaminoalkyl compounds, and salts and quaternaries thereof and, monomers of N,N-dialkylaminoalkyl(meth)acrylamides, (meth)acrylamidopropyltrimethylammonium chloride and the acid or quaternary salts of N,N-dimethylaminoethylacrylate and the like. These cationic monomers may also be copolymerized with nonionic monomers such as (meth)acrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl (meth)acrylate, acrylonitile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.
Amphoteric organic microparticles are made by polymerizing combinations 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 monomers in an organic microparticle typically is done in the presence of a polyfunctional crosslinking agent. These crosslinking agents are described in US
Polymeric microparticles useful in this invention include anionic, cationic, or amphoteric organic microparticles. These microparticles typically have limited solubility in water, may be crosslinked, and have an unswollen particle size of less than 750 nm.
Anionic organic microparticles include those described in US 6,524,439 and made by hydrolyzing acrylamide polymer microparticles or by polymerizing anionic monomers as (meth)acrylic acid and its salts, 2-acrylamido-2-methylpropane sulfonate, sulfoethyl-(meth)acrylate, vinylsulfonic acid, styrene sulfonic acid, maleic or other dibasic acids or their salts or mixtures thereof. These anionic monomers may also be copolymerized with nonionic monomers such as (meth)acrylamide, N-alkylacrylamides, N,N-dialkylactylamides, methyl (meth)acrylate, acrylonitrile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.
Cationic organic microparticles include those described in US 6,524,439 and made by polymerizing such monomers as diallyldialkylarnmonium halides, acryloxyalkyltrimethylammonium chloride, (meth)acrylates of dialkylaminoalkyl compounds, and salts and quaternaries thereof and, monomers of N,N-dialkylaminoalkyl(meth)acrylamides, (meth)acrylamidopropyltrimethylammonium chloride and the acid or quaternary salts of N,N-dimethylaminoethylacrylate and the like. These cationic monomers may also be copolymerized with nonionic monomers such as (meth)acrylamide, N-alkylacrylamides, N,N-dialkylacrylamides, methyl (meth)acrylate, acrylonitile, N-vinyl methylacetamide, N-vinyl methyl formamide, vinyl acetate, N-vinyl pyrrolidone, and mixtures thereof.
Amphoteric organic microparticles are made by polymerizing combinations 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 monomers in an organic microparticle typically is done in the presence of a polyfunctional crosslinking agent. These crosslinking agents are described in US
6,524,439 as having at least two double bonds, a double bond and a reactive group, or two reactive groups. Examples of these agents are N,N-methylenebis(meth)acrylamide, polyethyleneglycol di(meth)acrylate, N-vinyl acrylamide, divinylbenzene, triallylammonium salts, N-rnethylallylacrylamide glycidyl (meth)acrylate, acrolein, methylolacrylamide, dialdehydes like glyoxal, diepoxy compounds, and epichlorohydrin.
In an embodiment, the microparticle dose is between 0.5 and 8 lb/ton of filler treated. In an embodiment, the microparticle dose is between 1.0 and 4.0 lb/ton of filler treated.
Suitable coagulants generally have lower molecular weight than flocculants and have a high density of cationic charge groups. The coagulants useful in this invention are well known and commercially available. They may be inorganic or organic. Representative inorganic coagulants include alum, sodium aluminate, polyaluminum chlorides or PACs (which also may be under the names aluminum chlorohydroxide, aluminum hydroxide chloride, and polyaluminum hydroxychloride), sulfated polyaluminum chlorides, polyaluminum silica sulfate, ferric sulfate, ferric chloride, and the like and blends thereof.
Many organic coagulants are formed by condensation polymerization. Examples of polymers of this type include epichlorohydrin-dimethylamine (EPI-DMA) copolymers, and EPI-DMA copolymers crosslinked with ammonia.
Additional coagulants include polymers of ethylene dichloride and ammonia, or ethylene dichloride and dimethylamine, with or without the addition of ammonia, condensation polymers of multifunctional amines such as diethylenetriamine, tetraethylenepentamine, hexamethylenediamine and the like with ethylenedichloride or polyfunctional acids like adipic acid and polymers made by condensation reactions such as melamine formaldehyde resins.
Additional coagulants include cationically charged vinyl addition polymers such as polymers, copolymers, and terpolymers of (meth)acrylamide, diallyl-N,N-disubstituted ammonium halide, dimethylaminoethyl methacrylate and its quaternary ammonium salts, dimethylaminoethyl actylate and its quaternary ammonium salts, methacrylamidopropyltrimethylammonium chloride, diallylmethyl(beta-propionamido)ammonium chloride, (beta-methacryloyloxyethyptrimethyl ammonium methylsulfate, quaternized polyvinyllactam, vinylamine, and acrylamide or methactylamide that has been reacted to produce the Mannich or quaternary Mannich derivatives.
Suitable quaternary ammonium salts may be produced using methyl chloride, dimethyl sulfate, or benzyl chloride.
The terpolymers 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 weights of these polymers, both vinyl addition and condensation, range from as low as several hundred to as high as several million. Preferably, the molecular weight range should be from 20,000 to 1,000,000.
Other polymers useful as the second flocculating agent include cationic, anionic, or amphoteric polymers whose chemistry is described above as a flocculant. The distinction between these polymers and flocculants is primarily molecular weight. The second flocculating
In an embodiment, the microparticle dose is between 0.5 and 8 lb/ton of filler treated. In an embodiment, the microparticle dose is between 1.0 and 4.0 lb/ton of filler treated.
Suitable coagulants generally have lower molecular weight than flocculants and have a high density of cationic charge groups. The coagulants useful in this invention are well known and commercially available. They may be inorganic or organic. Representative inorganic coagulants include alum, sodium aluminate, polyaluminum chlorides or PACs (which also may be under the names aluminum chlorohydroxide, aluminum hydroxide chloride, and polyaluminum hydroxychloride), sulfated polyaluminum chlorides, polyaluminum silica sulfate, ferric sulfate, ferric chloride, and the like and blends thereof.
Many organic coagulants are formed by condensation polymerization. Examples of polymers of this type include epichlorohydrin-dimethylamine (EPI-DMA) copolymers, and EPI-DMA copolymers crosslinked with ammonia.
Additional coagulants include polymers of ethylene dichloride and ammonia, or ethylene dichloride and dimethylamine, with or without the addition of ammonia, condensation polymers of multifunctional amines such as diethylenetriamine, tetraethylenepentamine, hexamethylenediamine and the like with ethylenedichloride or polyfunctional acids like adipic acid and polymers made by condensation reactions such as melamine formaldehyde resins.
Additional coagulants include cationically charged vinyl addition polymers such as polymers, copolymers, and terpolymers of (meth)acrylamide, diallyl-N,N-disubstituted ammonium halide, dimethylaminoethyl methacrylate and its quaternary ammonium salts, dimethylaminoethyl actylate and its quaternary ammonium salts, methacrylamidopropyltrimethylammonium chloride, diallylmethyl(beta-propionamido)ammonium chloride, (beta-methacryloyloxyethyptrimethyl ammonium methylsulfate, quaternized polyvinyllactam, vinylamine, and acrylamide or methactylamide that has been reacted to produce the Mannich or quaternary Mannich derivatives.
Suitable quaternary ammonium salts may be produced using methyl chloride, dimethyl sulfate, or benzyl chloride.
The terpolymers 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 weights of these polymers, both vinyl addition and condensation, range from as low as several hundred to as high as several million. Preferably, the molecular weight range should be from 20,000 to 1,000,000.
Other polymers useful as the second flocculating agent include cationic, anionic, or amphoteric polymers whose chemistry is described above as a flocculant. The distinction between these polymers and flocculants is primarily molecular weight. The second flocculating
7 =
, _ agent must be of low molecular weight so that its solution can be mixed readily into a high solids filler slurry. In an embodiment, the second flocculating agent has an RSV of less than 5 dL/g.
The second flocculating agent may be used alone or in combination with one or more = additional second flocculating agents. In an embodiment, one or more microparticles are added = 5 to the flocculated filler slurry subsequent to 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 an embodiment, the second flocculating agent dose is between 0.2 and 8.0 lb/ton of filler treated. In an embodiment, the second component dose is between 0.5 and 6.0 lb/ton of filler treated.
In an embodiment, one or more microparticles may be added to the flocculated dispersion prior to shearing to provide additional flocculation and/or narrow the particle size distribution.
In an embodiment, the second flocculating agent and first flocculating agent are oppositely charged.
In an embodiment, the first flocculating agent is cationic and the second flocculating agent is anionic.
In an embodiment, the first flocculating agent is selected from copolymers of acrylamide with dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof In an embodiment, the first flocculating agent is an acrylamide and dimethylaminoethyl acrylate (DMAEA) copolymer with a cationic charge content of 10-50 mole % and an RSV of >
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 acrylamide-sodium acrylate copolymer having an anionic charge of 5-40 mole percent and a RSV of 0.3-5 dL/g.
In an embodiment, the first flocculating agent is anionic and the second flocculating agent is cationic.
In an embodiment, the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.
In an embodiment, the first flocculating agent is a copolymer of acrylamide and sodium acrylate having an anionic charge of 5-75 mole percent and an RSV of at least 15 dL/g.
In an embodiment, the second flocculating agent is selected from the group consisting of epichlorohydrin-dimethylamine (EPI-DMA) copolymers, EPI-DMA copolymers crosslinked with ammonia, and homopolymers of diallyl-N,N-disubstituted ammonium halides.
, _ agent must be of low molecular weight so that its solution can be mixed readily into a high solids filler slurry. In an embodiment, the second flocculating agent has an RSV of less than 5 dL/g.
The second flocculating agent may be used alone or in combination with one or more = additional second flocculating agents. In an embodiment, one or more microparticles are added = 5 to the flocculated filler slurry subsequent to 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 an embodiment, the second flocculating agent dose is between 0.2 and 8.0 lb/ton of filler treated. In an embodiment, the second component dose is between 0.5 and 6.0 lb/ton of filler treated.
In an embodiment, one or more microparticles may be added to the flocculated dispersion prior to shearing to provide additional flocculation and/or narrow the particle size distribution.
In an embodiment, the second flocculating agent and first flocculating agent are oppositely charged.
In an embodiment, the first flocculating agent is cationic and the second flocculating agent is anionic.
In an embodiment, the first flocculating agent is selected from copolymers of acrylamide with dimethylaminoethyl methacrylate (DMAEM) or dimethylaminoethyl acrylate (DMAEA) and mixtures thereof In an embodiment, the first flocculating agent is an acrylamide and dimethylaminoethyl acrylate (DMAEA) copolymer with a cationic charge content of 10-50 mole % and an RSV of >
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 acrylamide-sodium acrylate copolymer having an anionic charge of 5-40 mole percent and a RSV of 0.3-5 dL/g.
In an embodiment, the first flocculating agent is anionic and the second flocculating agent is cationic.
In an embodiment, the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.
In an embodiment, the first flocculating agent is a copolymer of acrylamide and sodium acrylate having an anionic charge of 5-75 mole percent and an RSV of at least 15 dL/g.
In an embodiment, the second flocculating agent is selected from the group consisting of epichlorohydrin-dimethylamine (EPI-DMA) copolymers, EPI-DMA copolymers crosslinked with ammonia, and homopolymers of diallyl-N,N-disubstituted ammonium halides.
8 In an embodiment, the second flocculating agent is a homopolymer of diallyl dimethyl ammonium chloride having an RSV of 0.1-2 dlig.
Dispersions of filler flocs according to this invention are prepared prior to their addition to the papermaking furnish. This can be done in a batch-wise or continuous fashion. The filler concentration in these slurries is typically less than 80% by mass. It is more typically between 5 and 65% by mass.
A batch process can consist of a large mixing tank with an overhead, propeller mixer.
The filler slurry is charged to the mix tank, and the desired amount of first flocculating agent is fed to the slurry under continuous mixing. The slurry and flocculant are mixed for an amount of time sufficient to distribute the first flocculating agent uniformly throughout the system, typically for about 10 to 60 seconds, depending on the mixing energy used. The desired amount of second flocculating agent is then added while stirring at a mixing speed sufficient to break down the filler flocs with increasing mixing time typically from several seconds to several minutes, depending on the mixing energy used. Optionally, a microparticle is added as a third component to cause reflocculation and narrow the floc size distribution. When the appropriate size distribution of the filler flocs is obtained, the mixing speed is lowered to a level at which the flocs are stable. This batch of flocculated filler is then transferred to a larger mixing tank with sufficient mixing to keep the filler flocs uniformly suspended in the dispersion. The flocculated filler is pumped from this mixing tank into the papermaking furnish.
In a continuous process the desired amount of first flocculating agent is pumped into the pipe containing the filler and mixed with an in-line static mixer, if necessary. A length of pipe or a mixing vessel sufficient to permit adequate mixing of filler and flocculant may be included prior to the injection of the appropriate amount of second flocculating agent.
The second flocculating agent is then pumped into the pipe containing the filler.
Optionally, a microparticle is added as a third component to cause reflocculation and narrow the floc size distribution. High speed mixing is then required to obtain the desired size distribution of the filler flocs. Adjusting either the shear rate of the mixing device or the mixing time can control the floc size distribution.
A continuous process would lend itself to the use of an adjustable shear rate in a fixed volume device. One such device is described in US Patent 4,799,964. This device is an adjustable speed centrifugal pump that, when operated at a back pressure exceeding its shut off pressure, works as a mechanical shearing device with no pumping capacity. Other suitable shearing devices include a nozzle with an adjustable pressure drop, a turbine-type emulsification device, or an adjustable speed, high intensity mixer in a fixed volume vessel. After shearing, the flocculated filler slurry is fed directly into the papermaking furnish.
Dispersions of filler flocs according to this invention are prepared prior to their addition to the papermaking furnish. This can be done in a batch-wise or continuous fashion. The filler concentration in these slurries is typically less than 80% by mass. It is more typically between 5 and 65% by mass.
A batch process can consist of a large mixing tank with an overhead, propeller mixer.
The filler slurry is charged to the mix tank, and the desired amount of first flocculating agent is fed to the slurry under continuous mixing. The slurry and flocculant are mixed for an amount of time sufficient to distribute the first flocculating agent uniformly throughout the system, typically for about 10 to 60 seconds, depending on the mixing energy used. The desired amount of second flocculating agent is then added while stirring at a mixing speed sufficient to break down the filler flocs with increasing mixing time typically from several seconds to several minutes, depending on the mixing energy used. Optionally, a microparticle is added as a third component to cause reflocculation and narrow the floc size distribution. When the appropriate size distribution of the filler flocs is obtained, the mixing speed is lowered to a level at which the flocs are stable. This batch of flocculated filler is then transferred to a larger mixing tank with sufficient mixing to keep the filler flocs uniformly suspended in the dispersion. The flocculated filler is pumped from this mixing tank into the papermaking furnish.
In a continuous process the desired amount of first flocculating agent is pumped into the pipe containing the filler and mixed with an in-line static mixer, if necessary. A length of pipe or a mixing vessel sufficient to permit adequate mixing of filler and flocculant may be included prior to the injection of the appropriate amount of second flocculating agent.
The second flocculating agent is then pumped into the pipe containing the filler.
Optionally, a microparticle is added as a third component to cause reflocculation and narrow the floc size distribution. High speed mixing is then required to obtain the desired size distribution of the filler flocs. Adjusting either the shear rate of the mixing device or the mixing time can control the floc size distribution.
A continuous process would lend itself to the use of an adjustable shear rate in a fixed volume device. One such device is described in US Patent 4,799,964. This device is an adjustable speed centrifugal pump that, when operated at a back pressure exceeding its shut off pressure, works as a mechanical shearing device with no pumping capacity. Other suitable shearing devices include a nozzle with an adjustable pressure drop, a turbine-type emulsification device, or an adjustable speed, high intensity mixer in a fixed volume vessel. After shearing, the flocculated filler slurry is fed directly into the papermaking furnish.
9 In both the batch and continuous processes described above, the use of a filter or screen to remove oversize filler flocs can be used. This eliminates potential machine runnability and paper quality problems resulting from the inclusion of large filler flocs in the paper or board.
In an embodiment, the median particle size of the filler flocs is at least 10 gm, In an embodiment, the median particle size of the filler flocs is between 10 and 100 pm. In an embodiment, the median particle size of the filler flocs is between 10 and 70 inn.
The foregoing may be better understood by reference to the following Examples, which are presented for purposes of illustration and are not intended to limit the scope of the invention.
Examples 1-7 The filler used for each example is either undispersed or dispersed, scalenohedral TM
precipitated calcium carbonate (FCC) (available as Albacar HO from Specialty Minerals Inc., ' Bethlehem, PA USA). When undispersed FCC is used, the dry product is diluted to 10% solids using tap water. When dispersed PCC is used, it is obtained as a 40% solids slurry and is diluted to 10% solids using tap water. The size distribution of the FCC is measured at three second intervals during flocculation using a Lasentee S400 FBRM (Focused Beam Reflectance Measurement) probe, manufactured by Lasentec, Redmond, WA. A description of the theory behind the operation of the FBRM can be found in Preikschat, F. K. and Preikschat, E., "Apparatus and method for particle analysis," U. S. Patent 4,871,251. The mean chord length (MCL) of the PCC flocs is used as an overall measure of the extent of flocculation. The laser probe is inserted in a 600 ml, beaker containing 300 mL of the 10% PCC slurry.
The solution is stirred using an IKA RE16 stirring motor at 800 rpm for at least 30 seconds prior to the addition of flocculating agents.
The first flocculating agent is added slowly over the course of 30 seconds to 60 seconds using a syringe. When a second flocculating agent is used, it is added in a similar manner to the first flmoulating agent after waiting 10 seconds for the first flocculating agent to mix. Fin211y, when a microparticle is added, it is in a similar manner to the flocculating agents after waiting 10 seconds for the second flocculating agent to mix. FIocculants are diluted to a concentration of 0.3% based on solids, coagulants are diluted to a concentration of 0.7% based on solids, starch is dilated to a concentration of 5% based on solids, and microparticles are diluted to a concentration of 0.5% based on solids prior to use. A typical MCL time resolution profile is shown in Fig. 1.
For every filler flocculation experiment, the maximum MCL after addition of the flocculating agent is recorded and listed in Table II. The maximum MCL
indicates the extent of flocculation. The slurry is then stirred at 1500 rpm for 8 minutes to test the stability of the filler flocs under high shear conditions. The MCL values at 4 minutes and 8 minutes are recorded and listed in Tables III and IV, respectively.
The particle size distribution of the filler flocs is also characterized by laser light TM
scattering using the Mastersizer Micro from Malvern Instruments Ltd., Southborough, MA USA.
The analysis is conducted using a polydisperse model and presentation 4PAD.
This presentation assumes a 1.60 refractive index of the filler and a refractive index of 1.33 for water as the continuous phase. The quality of the distribution is indicated by the volume-weighted median floc size, D(V,0.5), the span of the distribution, and the uniformity of the distribution. The span and uniformity are defined as:
span D(V,0.9) D(V,0.1) =
D(V ,0 .5) Evio(v,0.5)-D, unifornzity = _____________ D(V ,0.5)EV, Here D(v, 0.1), D(v,0.5) and D(v, 0.9) are defined as the diameters that are equal or larger than
In an embodiment, the median particle size of the filler flocs is at least 10 gm, In an embodiment, the median particle size of the filler flocs is between 10 and 100 pm. In an embodiment, the median particle size of the filler flocs is between 10 and 70 inn.
The foregoing may be better understood by reference to the following Examples, which are presented for purposes of illustration and are not intended to limit the scope of the invention.
Examples 1-7 The filler used for each example is either undispersed or dispersed, scalenohedral TM
precipitated calcium carbonate (FCC) (available as Albacar HO from Specialty Minerals Inc., ' Bethlehem, PA USA). When undispersed FCC is used, the dry product is diluted to 10% solids using tap water. When dispersed PCC is used, it is obtained as a 40% solids slurry and is diluted to 10% solids using tap water. The size distribution of the FCC is measured at three second intervals during flocculation using a Lasentee S400 FBRM (Focused Beam Reflectance Measurement) probe, manufactured by Lasentec, Redmond, WA. A description of the theory behind the operation of the FBRM can be found in Preikschat, F. K. and Preikschat, E., "Apparatus and method for particle analysis," U. S. Patent 4,871,251. The mean chord length (MCL) of the PCC flocs is used as an overall measure of the extent of flocculation. The laser probe is inserted in a 600 ml, beaker containing 300 mL of the 10% PCC slurry.
The solution is stirred using an IKA RE16 stirring motor at 800 rpm for at least 30 seconds prior to the addition of flocculating agents.
The first flocculating agent is added slowly over the course of 30 seconds to 60 seconds using a syringe. When a second flocculating agent is used, it is added in a similar manner to the first flmoulating agent after waiting 10 seconds for the first flocculating agent to mix. Fin211y, when a microparticle is added, it is in a similar manner to the flocculating agents after waiting 10 seconds for the second flocculating agent to mix. FIocculants are diluted to a concentration of 0.3% based on solids, coagulants are diluted to a concentration of 0.7% based on solids, starch is dilated to a concentration of 5% based on solids, and microparticles are diluted to a concentration of 0.5% based on solids prior to use. A typical MCL time resolution profile is shown in Fig. 1.
For every filler flocculation experiment, the maximum MCL after addition of the flocculating agent is recorded and listed in Table II. The maximum MCL
indicates the extent of flocculation. The slurry is then stirred at 1500 rpm for 8 minutes to test the stability of the filler flocs under high shear conditions. The MCL values at 4 minutes and 8 minutes are recorded and listed in Tables III and IV, respectively.
The particle size distribution of the filler flocs is also characterized by laser light TM
scattering using the Mastersizer Micro from Malvern Instruments Ltd., Southborough, MA USA.
The analysis is conducted using a polydisperse model and presentation 4PAD.
This presentation assumes a 1.60 refractive index of the filler and a refractive index of 1.33 for water as the continuous phase. The quality of the distribution is indicated by the volume-weighted median floc size, D(V,0.5), the span of the distribution, and the uniformity of the distribution. The span and uniformity are defined as:
span D(V,0.9) D(V,0.1) =
D(V ,0 .5) Evio(v,0.5)-D, unifornzity = _____________ D(V ,0.5)EV, Here D(v, 0.1), D(v,0.5) and D(v, 0.9) are defined as the diameters that are equal or larger than
10%, 50% and 90% by volume of filler particles, respectively. Viand Di are the volume fraction and diameter of particles in size group i. Smaller span and uniformity values indicate a more uniform particle size distribution that is generally believed to have better performance in papermaking. These characteristics of filler flocs at maximum MCL, 4 minutes and 8 minutes under 1500 rpm shear are listed in Tables II, III and IV for each example. The FCC type, flocculating agents, and doses of flocculating agents used in each example are listed in Table I.
Example 8 This experiment demonstrates the feasibility of using a continuous process to flocculate the PCC slurry. A batch of 18 liters of 10% solids undispersed FCC (available as Albacar 110 from Specialty Minerals Inc., Bethlehem, PA USA) in tap water is pumped using a centrifugal pump at 7.6 Ilmin into a five gallon bucket. A 1.0 lb/ton active dose of I%
flocculant A solution is fed into the FCC slurry at the centrifugal pump inlet using a progressive cavity pump. The FCC is then fed into a static mixer together with 1.0 lb/ton active dose of a 2% solids solution of coagulant A. The size distribution of the filler flocs is measured using the Mastersizer Micro and reported in Table II. 300 mL of the resultant slurry is stirred in a beaker at 1500 Lina for 8 minutes in the same manner as in Examples 1-7. The characteristics of the filler flocs at 4 minutes and 8 minutes are listed in Tables fll and IV, respectively.
Example 8 This experiment demonstrates the feasibility of using a continuous process to flocculate the PCC slurry. A batch of 18 liters of 10% solids undispersed FCC (available as Albacar 110 from Specialty Minerals Inc., Bethlehem, PA USA) in tap water is pumped using a centrifugal pump at 7.6 Ilmin into a five gallon bucket. A 1.0 lb/ton active dose of I%
flocculant A solution is fed into the FCC slurry at the centrifugal pump inlet using a progressive cavity pump. The FCC is then fed into a static mixer together with 1.0 lb/ton active dose of a 2% solids solution of coagulant A. The size distribution of the filler flocs is measured using the Mastersizer Micro and reported in Table II. 300 mL of the resultant slurry is stirred in a beaker at 1500 Lina for 8 minutes in the same manner as in Examples 1-7. The characteristics of the filler flocs at 4 minutes and 8 minutes are listed in Tables fll and IV, respectively.
11 Example 9 The filler slurry and experimental procedure are the same as in Example 8, except that coagulant A is fed into the centrifugal pump and flocculant A is fed into the static mixer. The size characteristics of the filler flocs are listed in Tables II, III and IV.
12 Table I. PCC type, flocculating agent descriptions, and flocculating agent doses for examples 1 through 9.
Polymer 1 Polymer 2 Microparticle PCC Dose Dose Dose Ex Type Name (lb/ton) Name (lb/ton) Name (lb/ton) 1 Undispersed Stalok 400 20 None None 2 Undispersed Flocculant A 1 Coagulant A 1 None 3 Undispersed Coagulant A 1 Flocculant A 1 None 4 Undispersed Flocculant B 1 Coagulant B 3 B 2 Undispersed Coagulant B 3 Flocculant B 1 B 2 6 Dispersed Flocculant A 1.5 Coagulant A 4 None 7 Dispersed Coagulant A 1 Flocculant A 1.5 None 8 Undispersed Flocculant A 1 Coagulant A 1 None 9 Undispersed Coagulant A 1 Flocculant A 1 None Stalok 400 Cationic starch available from Tate 8z Lyle, Decatur, IL USA
Flocculant A Anionic sodium acrylate-acrylamide copolymer flocculant with an RSV of about 32 dL/g and a charge content of 29 mole % available from Nalco Co., Naperville, IL USA.
Flocculant B Cationic acrylamide-dimethylaminoethyl methacxylate-methyl chloride quaternary salt copolymer flocculant with an RSV of about 25 dL/g and a charge content of 20 mole % available from Nalco Co., Naperville, IL USA.
Coagulant A Cationic poly(diallyldimethylammonium chloride) coagulant with an RSV of about 0.7 dL/g available from Nalco Co., Naperville, IL USA.
Coagulant B Anionic sodium acrylate-acrylamide copolymer with an RSV of about 1.8 dL/g and a charge content of 6 mole % available from Nalco Co., Naperville, IL USA.
Microparticle B Anionic colloidal borosilicate microparticle available from Nalco Co., Naperville, IL USA.
Polymer 1 Polymer 2 Microparticle PCC Dose Dose Dose Ex Type Name (lb/ton) Name (lb/ton) Name (lb/ton) 1 Undispersed Stalok 400 20 None None 2 Undispersed Flocculant A 1 Coagulant A 1 None 3 Undispersed Coagulant A 1 Flocculant A 1 None 4 Undispersed Flocculant B 1 Coagulant B 3 B 2 Undispersed Coagulant B 3 Flocculant B 1 B 2 6 Dispersed Flocculant A 1.5 Coagulant A 4 None 7 Dispersed Coagulant A 1 Flocculant A 1.5 None 8 Undispersed Flocculant A 1 Coagulant A 1 None 9 Undispersed Coagulant A 1 Flocculant A 1 None Stalok 400 Cationic starch available from Tate 8z Lyle, Decatur, IL USA
Flocculant A Anionic sodium acrylate-acrylamide copolymer flocculant with an RSV of about 32 dL/g and a charge content of 29 mole % available from Nalco Co., Naperville, IL USA.
Flocculant B Cationic acrylamide-dimethylaminoethyl methacxylate-methyl chloride quaternary salt copolymer flocculant with an RSV of about 25 dL/g and a charge content of 20 mole % available from Nalco Co., Naperville, IL USA.
Coagulant A Cationic poly(diallyldimethylammonium chloride) coagulant with an RSV of about 0.7 dL/g available from Nalco Co., Naperville, IL USA.
Coagulant B Anionic sodium acrylate-acrylamide copolymer with an RSV of about 1.8 dL/g and a charge content of 6 mole % available from Nalco Co., Naperville, IL USA.
Microparticle B Anionic colloidal borosilicate microparticle available from Nalco Co., Naperville, IL USA.
13 Table II Characteristics of filler flocs at maximum MCL or 0 min under 1500 rpm shear.
Example MCL (gm) 'D(v,0.1) (p.m) D(v,0.5) (gm) D(v,0.9) (gin) Span Uniformity 1 12.52 10.42 23.07 46.48 1.56 0.49 2 16.81 13.48 32.08 98.92 2.66 0.83 3 30.13 53.94 130.68 228.93 1.34 0.41 4 18.52 19.46 43.91 90.86 1.63 0.51 5 38.61 67.2 147.73 240.04 1.17 0.36 6 34.39 53.21 111.48 209.04 1.40 0.43 " 7 45.63 34.17 125.68 240.63 1.64 0.52 8 NA 24.4 58.17 125.47 1.74 0.52 9 NA 29.62 132.79 234.62 1.54 0.46 Table III. Characteristics of filler flocs after 4 minutes under 1500 rpm shear.
Example MCL (p.m) D(v,0.1) (pm) D(v,0.5) (pm) D(v,0.9) (pm) Span Uniformity 1 7.46 4.76 9.51 17.39 1.33 0.41 :
2 13.21 11.29 27.26 91.78 2.95 0.92 3 16.13 13.25 42.73 142.37 3.02 0.92 , 4 13.86 14.91 28.46 51.63 1.29 0.4 5 17.66 21.8 58.08 143.31 2.09 0.65 6 14.77 15.77 35.62 85.29 1.95 0.6 7 21.26 12.88 45.00 197.46 4.10 1.24 8 NA 14.91 35.88 76.29 1.71 0.53 9 NA 8.08 48.64 152.89 2.98 0.93
Example MCL (gm) 'D(v,0.1) (p.m) D(v,0.5) (gm) D(v,0.9) (gin) Span Uniformity 1 12.52 10.42 23.07 46.48 1.56 0.49 2 16.81 13.48 32.08 98.92 2.66 0.83 3 30.13 53.94 130.68 228.93 1.34 0.41 4 18.52 19.46 43.91 90.86 1.63 0.51 5 38.61 67.2 147.73 240.04 1.17 0.36 6 34.39 53.21 111.48 209.04 1.40 0.43 " 7 45.63 34.17 125.68 240.63 1.64 0.52 8 NA 24.4 58.17 125.47 1.74 0.52 9 NA 29.62 132.79 234.62 1.54 0.46 Table III. Characteristics of filler flocs after 4 minutes under 1500 rpm shear.
Example MCL (p.m) D(v,0.1) (pm) D(v,0.5) (pm) D(v,0.9) (pm) Span Uniformity 1 7.46 4.76 9.51 17.39 1.33 0.41 :
2 13.21 11.29 27.26 91.78 2.95 0.92 3 16.13 13.25 42.73 142.37 3.02 0.92 , 4 13.86 14.91 28.46 51.63 1.29 0.4 5 17.66 21.8 58.08 143.31 2.09 0.65 6 14.77 15.77 35.62 85.29 1.95 0.6 7 21.26 12.88 45.00 197.46 4.10 1.24 8 NA 14.91 35.88 76.29 1.71 0.53 9 NA 8.08 48.64 152.89 2.98 0.93
14 _ , Table W. Characteristics of filler flocs after 8 minutes under 1500 rpm shear.
Example MCL (lam) D(v,0.1) (i_tm) D(v,0.5) (pin) D(v,0.9) (pm) Span Uniformity 1 7.02 - 4.01 8.03 15 1.37 0.43 2 12.43 8.57 20.47 48.67 L96 0.67 3 13.62 9.46 28.93 110.3 3.49 1.06 4 12.88 12.48 23.48 42.36 1.27 0.45
Example MCL (lam) D(v,0.1) (i_tm) D(v,0.5) (pin) D(v,0.9) (pm) Span Uniformity 1 7.02 - 4.01 8.03 15 1.37 0.43 2 12.43 8.57 20.47 48.67 L96 0.67 3 13.62 9.46 28.93 110.3 3.49 1.06 4 12.88 12.48 23.48 42.36 1.27 0.45
15.30 15.64 41.16 106.73 2.21 0.7 6 12.06 10.47 23.88 52.81 1.77 0.62 7 17.42 9.2 30.37 176 5.49 1.53 8 NA 12.67 30.84 65.95 1.73 0.53 9 NA 6.66 34.82 116.3 3.15 0.99 As shown in Tables filler flocs formed in Example 1, where only cationic starch is 5 used, are not shear stable. On the other hand, filler flocs formed by multiple polymers exhibit enhanced shear stability, as demonstrated in Examples 2 to 9. Examples 2,4, 6 and 8 show filler flocs prepared according to this invention and Examples 3, 5, 7 and 9 show filler flocs prepared using existing methods. The filler flocs prepared according to the invention generally have narrower particle size distributions after being sheared down (as shown by the smaller values of span and uniformity in Tables III and IV) compared with those formed by existing methods.
Example 10 The purpose of this example is to evaluate the effects of different sizes of PCC flocs on the physical properties of handsheets. The PCC samples are obtained using the procedure described in Example 2, except that the PCC solids level is 2%. Four samples of preflocculated filler flocs (10-A, 10-B, 10-C and 10-D) are prepared with different particle sizes by shearing at 1500 rpm for different times. The shear times and resulting particle size characteristics are listed in Table V.
Thick stock with a consistency of 2.5% is prepared from 80% hardwood dry lap pulp and 20% recycled fibers obtained from American Fiber Resources (AFR) LLC, Fairmont, WV. The hardwood is refined to a freeness of 300 mL Canadian Standard Freeness (TAPPI
Test Method T
227 om-94) in a Valley Beater (from Voith Sulzer, Appleton, WI). The thick stock is diluted with tap water to 0.5% consistency.
Handsheets are prepared by mixing 650 mL of 0.5% consistency furnish at 800 rpm in a Dynamic Drainage Jar with the bottom screen covered by a solid sheet of plastic to prevent drainage. The Dynamic Drainage Jar and mixer are available from Paper Chemistry Consulting Laboratory, Inc., Cannel, NY. Mixing is started and 1 g of one of the PCC
samples is added after 15 seconds, followed by 6 lb/ton (product based) of GC7503 polyaluminum chloride solution (available from Gulbrandsen Technologies, Clinton, NJ, USA) at 30 seconds, 1 lb/ton (product based) of a sodium acrylate-acrylarnide copolymer flocculant with an RSV of about 32 dL/g and a charge content of 29 mole % (available from Nalco Company, Naperville, IL USA) at 45 seconds, and 3.5 lb/ton (active) of a borosilicate microparticle (available from Nalco Company, Naperville, IL USA) at 60 seconds.
Mixing is stopped at 75 seconds and the furnish is transferred into the deckle box of a Noble & Wood handsheet mold. The 8"x 8" handsheet is formed by drainage through a 100 mesh forming wire. The handsheet is couched from the sheet mold wire by placing two blotters and a metal plate on the wet handsheet and roll-pressing with six passes of a 25 lb metal roller.
The forming wire and one blotter are removed and the handsheet is placed between two new blotters and the press felt and pressed at 50 psig using a roll press. All of the blotters are removed and the handsheet is dried for 60 seconds (top side facing the dryer surface) using a rotary drum drier set at 220 F. The average basis weight of a handsheet is 84 g/m2. The handsheet mold, roll press, and rotary drum dryer are available from Adirondack Machine Company, Queensbury, NY. Five replicate handsheets are produced for each PCC
sample tested.
The finished handsheets are stored overnight at TAPPI standard conditions of 50%
relative humidity and 23 C. For each sheet, the basis weight is determined using TAPPI Test Method T 410 om-98, the ash content is determined using TAPPI Test Method T
211 om-93, brightness is determined using ISO Test Method 2470:1999, and opacity is determined using ISO
Test Method 2471:1998. Sheet formation, a measure of basis weight uniformity, is determined using a Kajaane Formation Analyzer from Metso Automation, Helsinki, Fl. The results from these measurements are listed in Table VI. The tensile strength of the sheets is measured using TAPPI Test Method T 494 om-01, Scott Bond is measured using TAPPI Test Method T 569 pm-00, and z-directional tensile strength (ZDT) is measured using TAPPI Test Method T 541 om-89.
These results are listed in Table VII.
Example 10 The purpose of this example is to evaluate the effects of different sizes of PCC flocs on the physical properties of handsheets. The PCC samples are obtained using the procedure described in Example 2, except that the PCC solids level is 2%. Four samples of preflocculated filler flocs (10-A, 10-B, 10-C and 10-D) are prepared with different particle sizes by shearing at 1500 rpm for different times. The shear times and resulting particle size characteristics are listed in Table V.
Thick stock with a consistency of 2.5% is prepared from 80% hardwood dry lap pulp and 20% recycled fibers obtained from American Fiber Resources (AFR) LLC, Fairmont, WV. The hardwood is refined to a freeness of 300 mL Canadian Standard Freeness (TAPPI
Test Method T
227 om-94) in a Valley Beater (from Voith Sulzer, Appleton, WI). The thick stock is diluted with tap water to 0.5% consistency.
Handsheets are prepared by mixing 650 mL of 0.5% consistency furnish at 800 rpm in a Dynamic Drainage Jar with the bottom screen covered by a solid sheet of plastic to prevent drainage. The Dynamic Drainage Jar and mixer are available from Paper Chemistry Consulting Laboratory, Inc., Cannel, NY. Mixing is started and 1 g of one of the PCC
samples is added after 15 seconds, followed by 6 lb/ton (product based) of GC7503 polyaluminum chloride solution (available from Gulbrandsen Technologies, Clinton, NJ, USA) at 30 seconds, 1 lb/ton (product based) of a sodium acrylate-acrylarnide copolymer flocculant with an RSV of about 32 dL/g and a charge content of 29 mole % (available from Nalco Company, Naperville, IL USA) at 45 seconds, and 3.5 lb/ton (active) of a borosilicate microparticle (available from Nalco Company, Naperville, IL USA) at 60 seconds.
Mixing is stopped at 75 seconds and the furnish is transferred into the deckle box of a Noble & Wood handsheet mold. The 8"x 8" handsheet is formed by drainage through a 100 mesh forming wire. The handsheet is couched from the sheet mold wire by placing two blotters and a metal plate on the wet handsheet and roll-pressing with six passes of a 25 lb metal roller.
The forming wire and one blotter are removed and the handsheet is placed between two new blotters and the press felt and pressed at 50 psig using a roll press. All of the blotters are removed and the handsheet is dried for 60 seconds (top side facing the dryer surface) using a rotary drum drier set at 220 F. The average basis weight of a handsheet is 84 g/m2. The handsheet mold, roll press, and rotary drum dryer are available from Adirondack Machine Company, Queensbury, NY. Five replicate handsheets are produced for each PCC
sample tested.
The finished handsheets are stored overnight at TAPPI standard conditions of 50%
relative humidity and 23 C. For each sheet, the basis weight is determined using TAPPI Test Method T 410 om-98, the ash content is determined using TAPPI Test Method T
211 om-93, brightness is determined using ISO Test Method 2470:1999, and opacity is determined using ISO
Test Method 2471:1998. Sheet formation, a measure of basis weight uniformity, is determined using a Kajaane Formation Analyzer from Metso Automation, Helsinki, Fl. The results from these measurements are listed in Table VI. The tensile strength of the sheets is measured using TAPPI Test Method T 494 om-01, Scott Bond is measured using TAPPI Test Method T 569 pm-00, and z-directional tensile strength (ZDT) is measured using TAPPI Test Method T 541 om-89.
These results are listed in Table VII.
16 Table V. Filler floc size characteristics for samples 10-A through 10-E.
The 10-E sample is an untreated PCC slurry.
Shear Time D(v, 0.1) D(v,0.5) D(v, 0.9) Example (s) MCL (pm) (pm) (1-11n) (pm) Span Uniformity 10-A 210 70.4 30.4 83.6 181.2 1.8 0.55 10-B 330 49.3 29.2 64.0 129.1 1.6 0.49 10-C 450 39.4 22.5 45.1 87.4 1.4 0.44 10-D 1500 29.8 13.8 25.8 46.3 1.3 0.39 10-E NA 9.24 0.64 1.54 3.28 1.7 0.66 _ Table VI. The optical properties of sheets with different size filler flocs.
PCC from Basis weight Ash content Opacity at Brightness Formation Ex. No. (g/m2) (%) 60Wm2(% ISO) (% ISO) Index 10-A 84.3 15.0 89.6 87.8 87.6 10-B 83.8 13.3 89.1 87.8 93.3 10-C 84.6 14.4 89.6 87.9 94.3 10-D 83.5 13.9 89.8 87.8 102.6 10-E 83.0 14.5 92.8 87.6 101.2
The 10-E sample is an untreated PCC slurry.
Shear Time D(v, 0.1) D(v,0.5) D(v, 0.9) Example (s) MCL (pm) (pm) (1-11n) (pm) Span Uniformity 10-A 210 70.4 30.4 83.6 181.2 1.8 0.55 10-B 330 49.3 29.2 64.0 129.1 1.6 0.49 10-C 450 39.4 22.5 45.1 87.4 1.4 0.44 10-D 1500 29.8 13.8 25.8 46.3 1.3 0.39 10-E NA 9.24 0.64 1.54 3.28 1.7 0.66 _ Table VI. The optical properties of sheets with different size filler flocs.
PCC from Basis weight Ash content Opacity at Brightness Formation Ex. No. (g/m2) (%) 60Wm2(% ISO) (% ISO) Index 10-A 84.3 15.0 89.6 87.8 87.6 10-B 83.8 13.3 89.1 87.8 93.3 10-C 84.6 14.4 89.6 87.9 94.3 10-D 83.5 13.9 89.8 87.8 102.6 10-E 83.0 14.5 92.8 87.6 101.2
17 .
I
, % ` _ ....,v . , _ = _, _ . _ Table VII. Mechanical strength properties of sheets with different size filler flocs.
Mechanical Strength Improvement (%) PCC from ZDT Scott Bond Tensile Index TEA Scott Tensile Ex. No. (kPa) (psi) (N=m/g) (N.crn/cm2) ZDT Bond Index TEA
10-A 733.2 226.3 82.9 2.6 14 26 3.8 44 10-B 709.7 = 254.8 81.7 2.2 10 52 2.3 20 10-C 675.9 217.2 83.0 2.5 4.8 29 3.9 36 10-D 681.4 219.6 85.5 2.3 5.7 31 7.0 30 10-E 644.9 179.0 79.9 1.8 0 0 0 0 . As shown in Table V, the size of the filler flocs decreases as the time under 1500 rpm shear increases, demonstrating the feasibility of controlling the size of filler flocs by the time under high shear. Handsheets prepared from each of the four preflocculated fillers (10-A through 10-D) and the untreated filler (10-E) have roughly equivalent ash contents and basis weight, as listed in Table VI. Increasing the floc size does not hurt brightness, but decreases the formation and opacity of the sheets slightly. The mechanical strength of the sheets, as measured by z-directional tensile strength, Scott Bond, tensile index, and tensile energy absorption (TEA) increases significantly with increasing filler floc size. This is shown in Table VII. In general, higher median PCC floc size leads to increased sheet strength. In practice, the slight loss of opacity could be compensated for by increasing the PCC content of the sheet at constant to improved sheet strength.
The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
'18
I
, % ` _ ....,v . , _ = _, _ . _ Table VII. Mechanical strength properties of sheets with different size filler flocs.
Mechanical Strength Improvement (%) PCC from ZDT Scott Bond Tensile Index TEA Scott Tensile Ex. No. (kPa) (psi) (N=m/g) (N.crn/cm2) ZDT Bond Index TEA
10-A 733.2 226.3 82.9 2.6 14 26 3.8 44 10-B 709.7 = 254.8 81.7 2.2 10 52 2.3 20 10-C 675.9 217.2 83.0 2.5 4.8 29 3.9 36 10-D 681.4 219.6 85.5 2.3 5.7 31 7.0 30 10-E 644.9 179.0 79.9 1.8 0 0 0 0 . As shown in Table V, the size of the filler flocs decreases as the time under 1500 rpm shear increases, demonstrating the feasibility of controlling the size of filler flocs by the time under high shear. Handsheets prepared from each of the four preflocculated fillers (10-A through 10-D) and the untreated filler (10-E) have roughly equivalent ash contents and basis weight, as listed in Table VI. Increasing the floc size does not hurt brightness, but decreases the formation and opacity of the sheets slightly. The mechanical strength of the sheets, as measured by z-directional tensile strength, Scott Bond, tensile index, and tensile energy absorption (TEA) increases significantly with increasing filler floc size. This is shown in Table VII. In general, higher median PCC floc size leads to increased sheet strength. In practice, the slight loss of opacity could be compensated for by increasing the PCC content of the sheet at constant to improved sheet strength.
The scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
'18
Claims (16)
1. A method of preparing a stable dispersion of flocculated filler particles having a predefined particle size distribution for use in papermaking processes, the method comprising:
a) providing an aqueous dispersion of filler particles;
b) adding a first flocculating agent to the dispersion to mix uniformly in the dispersion, the first flocculating agent being anionic and having a reduced specific viscosity (RSV) of at least 3 dL/g;
c) adding a second flocculating agent to the dispersion to initiate flocculation of the filler particles in the presence of the first flocculating agent, wherein the second flocculating agent is cationic; and d) shearing the flocculated dispersion to provide the dispersion of flocculated filler particles having the predefined particle size distribution, wherein the filler particles are flocculated prior to adding them to a paper stock and wherein no paper stock is present during steps a) to d), and wherein step b) causes either no flocculation of the filler particles or formation of flocs smaller than the flocculated filler particles provided in step d).
a) providing an aqueous dispersion of filler particles;
b) adding a first flocculating agent to the dispersion to mix uniformly in the dispersion, the first flocculating agent being anionic and having a reduced specific viscosity (RSV) of at least 3 dL/g;
c) adding a second flocculating agent to the dispersion to initiate flocculation of the filler particles in the presence of the first flocculating agent, wherein the second flocculating agent is cationic; and d) shearing the flocculated dispersion to provide the dispersion of flocculated filler particles having the predefined particle size distribution, wherein the filler particles are flocculated prior to adding them to a paper stock and wherein no paper stock is present during steps a) to d), and wherein step b) causes either no flocculation of the filler particles or formation of flocs smaller than the flocculated filler particles provided in step d).
2. The method of claim 1 wherein the flocculated filler particles have a median particle size of 10-100 µm.
3. The method of claim 1 wherein the filler is selected from the group consisting of calcium carbonate, kaolin clay, talc, titanium dioxide, alumina trihydrate, barium sulfate and magnesium hydroxide.
4. The method of claim 1 wherein the second flocculating agent is selected from the group consisting of copolymers of acrylamide with dimethylaminoethyl acrylate, copolymers of acrylamide with dimethylaminoethyl methacrylate, and mixtures thereof.
5. The method of claim 4 wherein the second flocculating agent is the copolymers of acrylamide with dimethylaminoethyl acrylate having a cationic charge of 10-50 mole percent and a RSV of at least 15 dL/g.
6. The method of claim 4 wherein the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.
7. The method of claim 6 wherein the filler particles are selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate, kaolin clay, and mixtures thereof.
8. The method of claim 7 wherein the flocculated filler particles have a median particle size of 10-70 µm.
9. The method of claim 1 wherein the first flocculating agent is selected from the group consisting of partially hydrolyzed acrylamide and copolymers of acrylamide and sodium acrylate.
10. The method of claim 9 wherein the first flocculating agent is a copolymer of acrylamide and sodium acrylate having an anionic charge of 5-75 mole percent and an RSV
of at least 15 dL/g.
of at least 15 dL/g.
11. The method of claim 9 wherein the second flocculating agent is selected from the group consisting of epichlorohydrin-dimethylamine (EPI-DMA) copolymers, EPI-DMA
copolymers crosslinked with ammonia, and homopolymers of diallyl-N,N-disubstituted ammonium halides.
copolymers crosslinked with ammonia, and homopolymers of diallyl-N,N-disubstituted ammonium halides.
12. The method of claim 11 wherein the second flocculating agent is a homopolymer of diallyl dimethyl ammonium chloride having an RSV of 0.1-2 dL/g.
13. The method of claim 1 wherein the filler particles are selected from the group consisting of precipitated calcium carbonate, ground calcium carbonate, kaolin clay, and mixtures thereof.
14. The method of claim 13 wherein the flocculated filler particles have a median particle size of 10-70 µm.
15. The method of claim 1 further comprising adding microparticles to the flocculated dispersion after addition of the second flocculating agent.
16. A method of making paper products from pulp comprising forming an aqueous cellulosic papermaking furnish, adding an aqueous dispersion of flocculated filler particles prepared according to the method of claim 1 to the furnish, draining the furnish to form a sheet and drying the sheet.
Applications Claiming Priority (3)
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| US11/854,044 US8172983B2 (en) | 2007-09-12 | 2007-09-12 | Controllable filler prefloculation using a dual polymer system |
| PCT/US2008/076167 WO2009036271A1 (en) | 2007-09-12 | 2008-09-12 | Controllable filler prefloculation using a dual polymer system |
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| JP (1) | JP5616791B2 (en) |
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-
2007
- 2007-09-12 US US11/854,044 patent/US8172983B2/en active Active
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2008
- 2008-08-08 TW TW097130170A patent/TWI378168B/en active
- 2008-09-12 WO PCT/US2008/076167 patent/WO2009036271A1/en active Application Filing
- 2008-09-12 KR KR1020107007835A patent/KR101443950B1/en active IP Right Grant
- 2008-09-12 CL CL2008002731A patent/CL2008002731A1/en unknown
- 2008-09-12 NZ NZ583681A patent/NZ583681A/en unknown
- 2008-09-12 CN CN2008801065472A patent/CN101802304B/en active Active
- 2008-09-12 AU AU2008298684A patent/AU2008298684B2/en active Active
- 2008-09-12 AR ARP080103989A patent/AR068444A1/en active IP Right Grant
- 2008-09-12 RU RU2010109347/05A patent/RU2471033C2/en active
- 2008-09-12 JP JP2010525026A patent/JP5616791B2/en active Active
- 2008-09-12 CA CA2698811A patent/CA2698811C/en active Active
- 2008-09-12 MY MYPI2010000950A patent/MY159380A/en unknown
- 2008-09-12 EP EP08799500.7A patent/EP2188448B2/en active Active
- 2008-09-12 MX MX2010002553A patent/MX2010002553A/en active IP Right Grant
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2010
- 2010-03-11 ZA ZA2010/01783A patent/ZA201001783B/en unknown
- 2010-04-12 CO CO10041901A patent/CO6270159A2/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| AU2008298684B2 (en) | 2013-04-04 |
| EP2188448A1 (en) | 2010-05-26 |
| US20090065162A1 (en) | 2009-03-12 |
| JP2010539344A (en) | 2010-12-16 |
| MX2010002553A (en) | 2010-06-08 |
| BRPI0815518A2 (en) | 2015-02-03 |
| WO2009036271A1 (en) | 2009-03-19 |
| CO6270159A2 (en) | 2011-04-20 |
| JP5616791B2 (en) | 2014-10-29 |
| NZ583681A (en) | 2011-06-30 |
| MY159380A (en) | 2016-12-30 |
| RU2010109347A (en) | 2011-10-20 |
| CL2008002731A1 (en) | 2009-01-16 |
| CN101802304B (en) | 2013-07-31 |
| EP2188448B2 (en) | 2022-05-25 |
| ZA201001783B (en) | 2010-11-24 |
| AR068444A1 (en) | 2009-11-18 |
| TW200914686A (en) | 2009-04-01 |
| EP2188448B1 (en) | 2016-08-17 |
| CA2698811A1 (en) | 2009-03-19 |
| KR101443950B1 (en) | 2014-09-24 |
| US8172983B2 (en) | 2012-05-08 |
| RU2471033C2 (en) | 2012-12-27 |
| KR20100085910A (en) | 2010-07-29 |
| TWI378168B (en) | 2012-12-01 |
| AU2008298684A1 (en) | 2009-03-19 |
| CN101802304A (en) | 2010-08-11 |
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