JP2015533953A - Filler suspension and its use in the manufacture of paper - Google Patents

Abstract

Provided herein is a filler suspension comprising swollen cationic starch, an anionic water-soluble polymer and filler particles. Pulp furnishes containing the filler suspension and papers containing pulp furnishes are also provided. Also provided are processes for making filler suspensions and processes for their use in the manufacture of paper. Accordingly, in one aspect, the present invention relates to a filler suspension (including filler particles, swollen cationic starch and an anionic water soluble polymer) for use in papermaking.

Description

  Provided herein is a filler suspension comprising swollen cationic starch and an anionic water-soluble polymer, a method of its use for the manufacture of paper and a paper comprising the suspension And paper products.

  In the manufacture of filler paper, the filler slurry is conventionally added to the pulp suspension before being transferred to the forming section of the paper machine. A retention modifier or a retention modifier system comprising several components is generally used to retain the filler in the resulting paper sheet to obtain a pulp / filler suspension (also as a furnish). To be known).

  Adding fillers to the paper can provide many improvements in sheet properties including improved opacity, whiteness, texture, and print sharpness. Further, when the filler is less expensive than pulp, the addition of filler to the sheet can result in cost savings due to the replacement of the pulp fibers by the filler. These savings become substantial when low cost fillers such as precipitated calcium carbonate (PCC) are used to replace expensive chemical pulp fibers. In addition, filled paper can be easier to dry than paper without filler, and as a result, the paper machine can run faster with less steam consumption, which further reduces costs. And can improve productivity.

  However, there is a limit to the amount of filler that can be added for a given sheet weight. Other factors such as retention, drainage and sizing should also be considered, but the resulting paper strength is the most important factor along with the paper machine efficiency that limits the filler content.

  Producing paper with a high filler content requires an efficient retention modifier system. The retention improver should provide good filler retention under the high shear and turbulence that occurs in the paper manufacturing process and should improve drainage without impeding formation. Retention improving chemicals are generally added to the furnish before or at the entrance to the paper machine headbox. Retention modifiers are one, two or three component chemical additives that improve filler and fines retention by a crosslinking and / or agglomeration mechanism. These chemicals can cause filler particles and fines (small fibrous fragments) to adhere to long fibers, or they can agglomerate into larger agglomerated particles that are more easily retained in the web. Help to cause. In order to produce this adhesion and agglomeration, these chemicals must adsorb on the surfaces of fillers, fines and fibers. The degree of adsorption and adhesion of chemicals determines the cleanliness of the furnish and the chemical properties of the furnish, the properties of the added chemical, the level of shear in the papermaking process and the retention modifier and furnish ingredients. It is affected by many things including the contact time between.

  The strength of the paper is not only because there is less fiber in the sheet, thereby reducing the number of fiber-fiber bonds, but also because the presence of the filler reduces the contact between the remaining fibers, Is inevitably reduced by the replacement of the fiber by. The filler particles do not bond between themselves and their positioning in the fiber-fiber bonded region prevents hydrogen bonding from occurring between the pulp fibers. As a result, holding a large amount of filler produces a more fragile sheet that can be more easily torn in paper machines, sizing press machines, coating machines, winders and printing press machines. More fragile fiber-fiber bonds also reduce the surface strength of the paper, causing reduced pick resistance and increased linting. Insufficient bonding of filler particles in the fibrous structure can also increase dust in the press chamber.

  In general, all inorganic fillers commonly used in papermaking (eg, but not limited to, clay, heavy calcium carbonate (GCC), PCC, chalk, talc, titanium dioxide and precipitated calcium sulfate (PCS)) Is known to reduce the strength of paper and increase the need for chemicals. Fillers with large surface areas, such as small trihedral PCCs, have a substantial negative impact on strength and the chemistry of additives used for strength, sizing and retention Increase the need for Due to its shape, narrow particle size distribution and large surface area, PCC has a tendency to reduce bonding in the sheet and also to other sheets of papermaking fillers such as chalk, GCC and clay, and also sheet Gives the sheet an open structure that makes it highly permeable or porous. As the PCC content in the furnish is increased, the need for sizing chemicals such as alkyl ketene dimers (AKD) and alkenyl succinic anhydrides (ASA) increases the desired degree of sizing or waterproofing. Increased to maintain. This is because an unbalanced portion of the sizing chemical is adsorbed on the large surface area PCC. Insufficient sizing efficiency and loss of waterproofing over time (resize) are common problems associated with the use of PCC in highly filled, wood-free paper sized with AKD and ASA. In recent years, many paper mills producing wood-containing paper grades have switched to neutral paper making it possible to use bright calcium carbonate fillers such as GCC and PCC; carbonation in these grades of paper Major concerns regarding the use of calcium remain in the areas of retention, sheet strength and printing operations.

  An ongoing industry trend is to reduce sheet weighing to reduce costs. Unfortunately, as the weight is reduced, almost all paper properties, including the limiting factors of opacity, bending stiffness and permeability, deteriorate. The reduction in weighing can also reduce filler retention during papermaking and can increase the frequency of sheet tearing both on the paper machine and during print processing and printing. To overcome the loss in sheet opacity, papermakers can add more high opacity fillers, but this causes further deterioration in sheet strength. The industry requires cost effective technology for the production of lightweight grades with good filler retention and drainage and acceptable strength, formation, optical and printing properties.

  Thus, in one aspect, the invention relates to a filler suspension (including filler particles, swollen cationic starch and anionic water soluble polymer) for use in papermaking.

  In one aspect of the invention, the anionic water soluble polymer is lightly crosslinked.

  In one aspect of the invention, the anionic, lightly cross-linked, water-soluble polymer has a tan delta rheological vibration at 0.005 Hz of at least 0.5 in a 1.5% aqueous solution.

  In one aspect of the invention, the anionic, lightly cross-linked, water-soluble polymer includes sodium acrylate, acrylamide and methylene bisacrylamide.

  In one aspect of the invention, the anionic water-soluble polymer is TELIOFORM® M305.

  In one aspect of the invention, the filler particles are selected from the group consisting of clay, talc, heavy calcium carbonate, chalk, precipitated calcium carbonate, precipitated calcium sulfate and combinations thereof.

  In one aspect of the invention, the cationic starch granules are swollen with hot water at a gel point temperature of the cationic starch of ± 10 ° C. without cooking the cationic starch.

  In one aspect of the invention, the temperature at which the cationic starch granules are swollen is the gel point temperature + 10 ° C.

  In one aspect of the invention, the filler particles have a size of 1 to 10 microns.

  In one aspect of the invention, the swollen cationic starch granules have a size of 25 to 100 microns.

  In one aspect of the invention, based on the total solid content of the filler suspension, the filler particles are present in an amount of 60 to 99.5% by weight and the swollen cationic starch is by weight. It is present in an amount of 35 to 0.499% and the water soluble polymer is present in an amount of 5.0 to 0.001% by weight.

  One aspect of the present invention is a pulp furnish comprising pulp fibers and a filler suspension herein.

  In one aspect of the invention, the pulp furnish includes a co-additive selected from the group consisting of sizing agents, wet strength agents, retention modifiers, and combinations thereof.

  One aspect of the present invention is paper containing the pulp furnish.

  One aspect of the present invention is a process for producing a filler suspension for papermaking that includes contacting the filler particles with swollen cationic starch and an anionic water soluble polymer.

  In one aspect of the invention, in the above process, the anionic water soluble polymer is lightly crosslinked.

  One aspect of the present invention is to contact the filler suspension and pulp fibers herein to form a pulp furnish; discharging the pulp furnish through a wire to form a sheet. And a process for producing a paper comprising drying the sheet.

  In one aspect of the invention, in the above process, the pulp furnish further comprises a co-additive selected from the group consisting of a sizing agent, a wet strength agent, a dry strength agent, a retention improver, and combinations thereof. .

FIG. 1 is a schematic diagram of a papermaking process in which an anionic water soluble polymer, a cationic swollen starch and a filler are mixed essentially simultaneously.

FIG. 2 is a schematic diagram of a papermaking process in which an anionic water-soluble polymer is premixed with a swelled cationic starch prior to mixing with a filler.

FIG. 3 is a schematic diagram of a papermaking process in which an anionic water-soluble polymer is premixed with a filler prior to mixing with the swollen cationic starch.

FIG. 4 is a schematic diagram of a papermaking process where swollen cationic starch is premixed with a filler prior to mixing with an anionic water soluble polymer.

FIG. 5 is a graph of the viscosity response of corn starch when heated to and above the gelation temperature.

FIG. 6 includes microscopic images of corn starch granules when heated in water at various temperatures.

(Detailed explanation)
(General)
Unless expressly stated otherwise, the use of the singular herein includes the plural and vice versa. That is, "a" and "the" refer to one or more whatever the word modifies. For example, “a lightly cross-linked polymer” includes one such polymer, two such polymers, or even a larger number of such polymers under the right circumstances. Similarly, such as, but not limited to, “sizing agents” (unless it is clearly stated or otherwise clear from the context) that such is not intended. The term may refer to a plurality of such agents or simply a single such agent.

  Approximate terms (eg, including but not limited to “about”, “substantially”, “essentially” and “approximately”) are such that the features so modified It does not have to be the described feature, which means that it can vary to some extent from the described feature. The extent to which the description can vary is how much change can be enacted, and how much change will allow one of ordinary skill in the art that the modified feature still has the required characteristics and possibilities of the unmodified feature. It depends on whether or not it is recognized that it has. In general, however, in accordance with the above discussion, explicitly stated or implied values modified herein by approximate language may vary ± 15% from the stated values.

(Composition)
In one embodiment herein, for use in papermaking comprising filler particles, swollen cationic starch and an anionic water soluble polymer in a liquid vehicle (typically water). A filler suspension is provided.

  In another embodiment, a pulp furnish is provided that includes a filler suspension and pulp fibers as described herein in an aqueous vehicle. The furnish may also contain other papermaking agents.

  In yet another embodiment, a method is provided for producing paper by adding a filler suspension of the present invention to a pulp fiber stock to form a pulp furnish and then manufacturing the paper from the furnish. Is done. Anionic and cationic agents can be added to the furnish containing the filler suspension to improve retention and improve drainage. As previously mentioned, the furnish can also include other papermaking agents.

  The present invention also provides a process for producing swollen starch / polymer compositions and combinations thereof with filler particles to form a filler suspension.

  As used herein, “swollen” starch is a raw starch granule, preferably at this time, no more water can be absorbed while breaking the swollen granule. This refers to starch that has absorbed water to its state and has expanded. To accomplish this, swelling the starch is performed under carefully controlled temperature, pH, mixing and time conditions. These parameters vary from starch type to starch and are usually determined empirically for each type of starch before being used in mill-scale paper production. The general procedure is simply to suspend the raw starch in cold water and then heat the suspension until the starch is swollen. This swollen starch is then mixed with the anionic water-soluble polymer and filler particles in any desired order to form a filler suspension. For example, in FIG. 1, swollen starch 1, anionic polymer 8a and filler particles 2 are mixed in a mixer 4 to form a filler suspension, which is then moved to mixer 5; There, it is mixed with pulp fiber 3 to form a finished paper stock. In FIG. 2, the swollen cationic starch 1 and the anionic water-soluble polymer 8a are premixed, and then this combination is mixed with the filler particles 2 in the mixer 4 and then the formed filler. The suspension is mixed with the pulp fiber 3 in the mixer 5. In FIG. 3, anionic water-soluble polymer 8a is premixed with filler particles 2, and the combination is mixed with cationic starch 1 swollen in mixer 4, and this formed filler. The suspension is moved to the mixer 5 where it is mixed with the pulp fibers 3 to form a furnish. In FIG. 4, the swollen cationic starch 1 and fiber particles 2 are premixed in the mixer 4 and this premix is transferred to the mixer 5 where the anionic polymer 8a is essentially mixed with the mixer 4 and the mixer. Add to this premix during the passage between 5. In each of these aspects, the furnish containing the filler suspension is then moved to the paper machine 6 to form paper 9. The co-additive 7 can be added as necessary. During the paper drying operation, the retained swollen starch granules break and act to liberate amylopectin and amylose macromolecules and bind the solid components of the sheet.

  The combination of swollen cationic starch, anionic polymer and filler particles can be used for papermaking under acid, neutral or alkaline conditions. This composition is primarily used to ensure that the filler and starch are well retained in the paper sheet during the papermaking process while having a minimal adverse effect on sheet strength. Using a swollen cationic starch / anionic water-soluble polymer / filler particle composition is larger than using a swollen cationic starch or anionic polymer alone with the filler particles. There is a tendency to result in retention and strength.

  When the filler is mixed with the swollen cationic starch / anionic water-soluble polymer and added to the pulp slurry, the filler particles agglomerate and adsorb to the surface of the slurry fines and fibers. Causes rapid aggregate formation in the stock. This can result in good retention of fillers and fibers and improves fiber drainage even without the addition of retention modifiers. However, under high levels of shear, turbulence and vacuum, filler retention can be reduced due to deagglomeration and detachment of the filler from the fiber surface. It is possible to add anionic microparticles such as colloidal silicic acid to the papermaking furnish containing the filler suspension at or before the headbox and preferably at the present time before the pressure screen of the paper machine. , Retention and drainage can be further improved.

(Filler)
The filler particles can be any known to those skilled in the art, and the filler suspension can contain a single type of filler or more than one type of filler. Filler particles typically have an average particle size ranging from 0.5 to 30 μm, more commonly from 1 to 10 μm, typically inorganic materials such as clay, heavy calcium carbonate (GCC), chalk. , Precipitated calcium carbonate (PCC), talc, precipitated calcium sulfate (PCS), and blends thereof. Currently, PCC is the preferred filler. The pulp slurry to which the filler suspension is added can be composed of mechanical pulp, chemical pulp, regenerated pulp and mixtures thereof.

(Cationic starch)
Starches suitable for use in the present invention include, but are not limited to, starches derived from corn, waxy corn, potato, wheat, tapioca, sorghum, waxy sorghum and rice. Starch is generally made cationic by the inclusion of quaternary ammonium cations in the starch. Cationic starches are commercially available and their preparation is well known to papermakers and therefore need not be described further herein. The average particle size of most raw starch granules is about 5 to 45 μm.

  Starch granules are insoluble in cold water. The starch is heated in an aqueous suspension to disperse or “cook” the starch. As heating proceeds, the starch granules are referred to as “pasting”, “gelatinization” or simply “gel” temperatures, resulting in strong swelling and a significant increase in viscosity. A critical reversible swelling phase is first passed to a critical temperature that causes a significant increase. If maintained for a sufficient period above the gel temperature, the viscosity returns to a lower level due to the breakage of the swollen granules. Each type of starch has its own gel temperature. The gel temperature of many starches is available in the existing literature or can be readily determined empirically by heating a given starch suspension while monitoring the viscosity. Swelled starch granules are different from cooked starch. Cooked starch results when the swollen starch granules break apart at temperatures above the gelling temperature and thereby release amylose and amylopectin that dissolve in the aqueous medium.

  For the purposes of the present invention, the swelling of the starch granules is carefully controlled to form swollen starch in which a minimal amount of swollen granule breakage occurs. Depending on the source of starch, the ultimate particle size of the swollen starch granules ranges from about 25 μm to about 100 μm. Representative non-limiting examples of the preparation of swollen starch are shown in this example.

(Anionic water-soluble polymer)
The anionic water-soluble polymer may be linear or lightly crosslinked. By lightly crosslinked is meant that the crosslinked polymer remains water soluble. That is, lightly cross-linked polymers appear to resemble “branched” polymers rather than fully cross-linked polymers in which the polymer chains are intertwined intimately and thus rendered insoluble in water. As used herein, lightly crosslinked and branched are used interchangeably to refer to a polymer that is crosslinked but still water soluble. Examples of anionic, branched, water-soluble polymers are described in US Pat. Nos. 5,958,188, 6,391, incorporated by reference in their entirety as if fully set forth herein. 156 B1, 6,395,134 B1, 6,406,593 B1, and 6,454,902 B1.

In certain embodiments, the anionic, branched, water-soluble polymer is:
(A) prepared by adding a crosslinker or branching agent to the monomer charge;
(B) has an intrinsic viscosity greater than about 3 dl / g; and (c) has a tan delta rheological oscillation value at 0.005 Hz of at least 0.5, or no branching agent is present. It has a deionized SLV viscosity number that is at least three times the salt addition SLV viscosity number of polymers made from the same monomer raw material under the same conditions.

  The polymer can be made by reacting the monomer or monomer blend under polymerization conditions such as reverse phase emulsion polymerization in a conventional process using a crosslinker or branching agent contained in the monomer feed. The amount of branching agent and polymerization conditions are selected in such a way that the polymerization results in a water soluble polymer and no water insoluble crosslinked polymer.

  For the purposes of the present invention, there is no need to specify the numerical range (ie, percent) of cross-linking that results in a water-soluble branched polymer that can be used. Rather, the properties of the resulting polymer are monitored until a specific range in those properties is achieved. One indication that a branched polymer behaves as a solution polymer rather than a microparticulate polymer is the tan delta value. Without being bound by any particular theory, at low frequencies such as 0.005 Hz, the rate of deformation of the polymer sample is slow enough to allow linear or branched entangled chains to be unwound. It is believed that high tan delta values result. On the other hand, network or heavily crosslinked polymers are permanently entangled and exhibit low tan delta values over a wide range of frequencies. Thus, by determining the tan delta at a low frequency of 0.005, a measure of the degree of branching can be confirmed. For purposes of the present invention, the tan delta value is greater than 0.5, preferably greater than 0.7, and even more preferably greater than 0.9, 1.3, or even greater. A tan delta value of less than 0.5 indicates a polymer that is too heavily crosslinked and preferably avoided to act as a true solution polymer.

  The tan delta value at 0.005 Hz can be obtained using a Controlled Stress Rheometer in Oscillation mode for a solution of 1.5 wt% polymer in deionized water. The value of the tan delta is the ratio of the loss (viscosity) rate G ″ to the storage (elastic) rate G ′.

  The branched polymers herein are preferably the corresponding unbranched polymers (ie, polymers made under the same conditions except for the absence of branching agents that result in higher intrinsic viscosities). With a tan delta value at 0.005 Hz reasonably close to the value of. For example, the branched polymer preferably has a tan delta that is at least 50%, and often at least 80% (eg, up to or above 120%) of the tan delta of the corresponding unbranched polymer.

  Another indication that the polymer is in solution rather than being microparticulate is that the deionized SLV viscosity number of the branched polymer is the same when no branching agent is present under the same polymerization conditions. It is at least 3 times the salt-added SLV viscosity number of the polymer produced by reacting the monomer raw materials. This was referred to as “corresponding unbranched polymer”.

  “Same monomer feed” and “Same polymerization conditions” are reasonable in commercial production, except that the feed and conditions are deliberate in the amount of branching agent and, if appropriate, chain transfer agent. Is constant enough to be achieved.

  The branching agent can be any cross-linked object capable of reacting with pendant groups on the main polymer chain, including but not limited to, for example, carboxylic acid groups of acrylic acid, but preferably The branching agent is a polyethylenically unsaturated monomer. The polyethylenic branching agent can be a bifunctional material such as methylenebisacrylamide, or can be a trifunctional, tetrafunctional or higher functional branching agent such as tetrachloride Allyl ammonium is mentioned. Preferably, the branching agent itself is water soluble.

  The amount of polyethylene branching agent is generally less than 10 ppm molar, preferably less than 5 ppm molar. Useful results can be obtained at about 0.5 to 3.8 ppm molar, but in some cases amounts from 4.1 to 7 ppm molar or even 10 ppm molar can be used. In fact, sometimes molar amounts up to 20 ppm or even molar concentrations up to 30 ppm or 40 ppm (generally in the presence of chain transfer agents) can be used, but smaller amounts are typically subject to tan delta limits. Is required for. The designation “ppm molar” refers to the moles of branching agent per million moles of monomer. (Ie ppm molar concentration)

  This branched polymer can be made under polymerization conditions that are intended to be free of intentional chain transfer agents during the reaction. The amount of branching agent described above, especially 1 to 10 ppm molar and preferably 0.5 to 3.8 ppm molar, is particularly suitable when no chain transfer agent is added. However, it may be desirable to add some chain transfer agent and the amount of branching agent up to 20 ppm molar or up to 30 ppm molar or even up to 40 ppm molar while still maintaining the characteristic properties and performance of the polymer. Can be increased. The amount of chain transfer agent selected will depend on the particular material used as well as the amount of branching agent, monomer feedstock and polymerization conditions.

  Although very large amounts of branching agent can be used, this amount is preferably small since it has been observed that the best results are obtained with small amounts of chain transfer agent. A preferred chain transfer agent is sodium hypophosphite. Although many amounts can be used, best results generally require an amount (by weight based on the weight of the monomer) of less than 50 ppm, and preferably less than 20 ppm. Best results are generally obtained when not greater than 10 ppm. However, if the amount is too low, such as below about 2 ppm, the benefits of using a chain transfer agent may be insufficient.

  Any chain transfer agent suitable for use in aqueous polymerization of water soluble acrylic monomers such as but not limited to isopropanol or mercapto compounds may be used as a hypophosphorous acid alternative. . If a material other than hypophosphorous acid is used, it should be used in an amount that provides a chain transfer effect that is substantially similar to the amount of hypophosphorous acid substituted.

  It is preferable to use a small amount of chain transfer agent, but if the combination of raw materials and polymerization conditions is such that the polymer has the desired physical properties, it will generally result in less efficient, but more Can be used (eg 100 ppm or more)

  One desirable physical property is the intrinsic viscosity of the polymer. This is measured using a suspension level viscometer in 1 M NaCl buffered to pH 7.5 at 25 ° C. It is usually at least 3 or 4 dl / g and preferably at least 6 dl / g. It can be as high as 18 dl / g, for example, but is usually less than 12 dl / g and often less than 10 dl / g.

  Suitable branched polymers may be characterized by comparison with the corresponding unbranched polymer. Unbranched polymers generally have an intrinsic viscosity of at least 6 dl / g, and preferably at least 8 dl / g. Usually it is 16 to 30 dl / g. The amount of branching agent is usually such that the intrinsic viscosity is reduced by at least 10% of the value of the unbranched polymer, and usually by at least 25% or 40%, up to 70% or sometimes up to 90%.

  Instead of or in addition to the intrinsic viscosity, the polymer may be characterized by its saline Brookfield viscosity. Brine Brookfield viscosity is measured by preparing a 0.1 wt% solution of the polymer in 1 M aqueous NaCl at 25 ° C. A Brookfield viscometer equipped with a UL adapter at 60 rpm can be used. Thus, the powdered polymer is added to the 1M aqueous NaCl solution or the reverse emulsion polymer is added to the solution. The viscosity of the aqueous salt solution is generally 2.0 mPa.s. s and usually at least 2.2, and preferably at least 2.5 mPa.s. s. Generally, it is 5 mPa.s. A value of 3 to 4 is usually preferred, not greater than s.

  It is also possible to use a ratio between the deionized SLV viscosity number and the salted SLV viscosity number instead of or in addition to the tan delta value as an indicator of the absence of insoluble crosslinked microparticles.

The SLV viscosity number is determined by use of a glass suspension level viscometer at 25 ° C., which is selected according to the viscosity of the solution. The viscosity number is η−η ₀ / η ₀ where η and η ₀ are the viscosity results of the aqueous polymer solution and the solvent blank, respectively. This can also be referred to as specific viscosity. The deionized SLV viscosity number is the number obtained for a 0.05% solution of the polymer in deionized water. The salted SLV viscosity number is the number obtained for a 0.05% solution of the polymer in 1M aqueous sodium chloride solution.

  The deionized SLV viscosity number is preferably at least 3 and generally at least 4. The best results are obtained when it exceeds 5 (eg 7 or 8). Preferably it is higher than the deionized SLV viscosity number for the unbranched polymer. If the deionized SLV viscosity number is not greater than the deionized SLV viscosity number of the unbranched polymer, preferably it is at least 50% of the deionized SLV viscosity number of the unbranched polymer, and usually at least 75%. The salted SLV viscosity number is usually less than 1. The deionized SLV viscosity number is often at least 5 times and preferably at least 8 times the salted SLV viscosity number.

  The polymer can be obtained from commercial sources, but may be made by any conventional suitable polymerization process known for making water soluble acrylic and other additive polymers such as bead or gel polymerization. . A preferred type of polymerization process is reverse phase emulsion polymerization that forms a reverse phase emulsion of water soluble polymer particles in a non-aqueous liquid. The product typically has an initial particle size of at least 95% by weight and less than 10 μm, and preferably at least 90% by weight and less than 2 μm, for example down to 0.1 or 0.5 μm. Thus, it can be a conventional reverse emulsion or microemulsion and can be made by any known technique for making such materials. If desired, the number average size can be typical of a microemulsion, for example down to 0.05 or 0.1 μm.

  The emulsion may be supplied in a prepared form (as an emulsion of aqueous polymer droplets in oil or other immiscible liquid) or, if desired, it may be substantially anhydrous dispersed in the oil. It may be substantially dehydrated to form a stable dispersion of polymer droplets. Conventional surfactants and optionally polymeric amphiphilic stabilizers may be included in a known manner to stabilize the emulsion.

  The reverse phase or other polymerization process is usually performed on the raw material of the desired monomer or monomer blend in aqueous solution.

  In general, anionic branched polymers comprise 5 to 97% by weight acrylamide or other water soluble, nonionic, ethylenically unsaturated monomers and 95 to 3% by weight ethylenically unsaturated carboxylic acids, sulfones. A copolymer with an acid or other anionic monomer is preferred. Examples include, but are not limited to acrylic acid, methacrylic acid, crotonic acid, vinyl sulfonic acid and AMPS, and any conventional water-soluble carboxylic acid and sulfonic acid monomer can be used. The presently preferred anionic monomer is often acrylic acid as sodium acrylate or other water soluble salt. Preferred copolymers contain 20 to 80% by weight, often 40 to 75% by weight acrylic acid, the remainder being acrylamide.

  In a particular embodiment, the anionic water soluble polymer is TELIOFORM® M305 (BASF, commercially available).

(Swelled cationic starch / anionic polymer / filler particle suspension)
Generally, this suspension comprises 60 to 99.5% by weight filler, 35 to 0.499% by weight swollen cationic starch and 5.0 to 0.001% by weight anionic polymer. , Based on the total solid content of filler particles, cationic starch and anionic polymer, totaling 100%. This suspension contains a complex of anionic polymer bound to swollen cationic starch, but it is understood that it may contain free swollen cationic starch and free anionic polymer particles. Is done.

  The swollen cationic starch and anionic polymer are suitably utilized in an amount of 0.5 to 10% by weight as dry solids based on the weight of the filler particles.

(Paper making agent)
The compositions, suspensions and furnishes herein further include sizing agents such as conventional papermaking agents (eg, alkyl ketene dimers, alkenyl succinic anhydrides and rosins; wet strength agents and cationic or anionic Non-limiting polymeric polymeric retention modifiers). This composition consists of a single chemical (eg anionic microparticles (colloidal silicic acid, bentonite), anionic polyacrylamide, cationic polymer (cationic polyacrylamide, cationic starch)), two-component chemical system (Cationic polymer / anionic microparticle, cationic polymer / anionic polymer) or three-component system (cationic polymer / anionic microparticle / anionic polymer, cationic polymer / anionic micropolymer / anionic polymer) Possible retention modifiers may be included. The selection of retention modifier chemicals and their point of addition in the papermaking process depends on the nature of the treated filler slurry and the ionic feedstock of the papermaking furnish.

  Generally, the filler suspensions herein are used in amounts of 5% to 60% as dry solids, based on the dry weight of the pulp in the furnish.

  A paper sheet made with a filler can exhibit better internal bond strength than a control sheet made without the filler, as measured by the Scott bond technique. With the same filler content, the wet and dry strength properties of sheets made using this filler suspension can be greater than sheets made with filler alone.

  The use of the filler suspension of the present invention enables the production of filled papers such as fine coated and uncoated paper, supercalender paper and newsprint paper with minimal strength loss and good optical properties. . Thus, using the filler suspension of the present invention may allow a papermaker to produce a filled paper having a higher filler content in the paper sheet. In general, the potential benefits from using the treated filler suspensions of the present invention are improved sizing, wet strength, dry strength, opacity and print quality and reduced use of expensive reinforced chemical pulp fibers. including.

  Under certain conditions, the combination of swollen cationic starch and anionic polymer can be used to enhance other grades that do not include fillers such as bag paper and paperboard products.

(General)
The suspensions and methods of the present invention can be described and understood by the following examples. In the examples, the results were obtained using laboratory scale techniques. However, these examples should not be construed as limiting in any way or intended.

  Starch that is 2 to 20% solids in the slurry at room temperature can be swollen at a temperature near the starch gel point in a batch digester, jet digester, or by mixing with hot water. A preferred method is to swell the granules by mixing a starch slurry prepared in cold water with hot water. The temperature of the hot water used depends on the consistency of the initial starch slurry in the cold water, the final target temperature of the swollen starch, the temperature of the cold water, the pH and the residence time. The temperature and reaction time for preparing the swollen starch / polymer composition depends on the type of starch used, the pH of the starch slurry and the heating time. The following is an example of a process for the preparation of swollen starch for the purposes of the present invention.

Example 1
The raw starch dispersion mixed with the polymer in cold water is swollen and the swollen starch / polymer composition is added to the stirred filler suspension. In this method, the starch powder is first dispersed in cold water, after which the polymer is incorporated into the dispersion under shear. The starch / anionic polymer mixture is mixed with hot water or heated to a temperature close to the starch gel point. The swollen starch / anionic polymer composition is then rapidly mixed with the filler suspension at a temperature below the starch gelling temperature.

(Example 2)
The cationic starch dispersion is first swollen and then added to the stirred filler suspension followed by the introduction of the anionic polymer. In this method, the starch powder is dispersed in cold water and then mixed with hot water or heated to a temperature close to the starch gel point. The swollen starch is then rapidly mixed with the filler suspension at a temperature below the starch gel point, followed by the addition of the anionic polymer.

  The combination of swollen cationic starch, anionic water-soluble polymer and filler is performed under good mixing conditions. Other anionic agents or cationic agents can be added during the preparation of the swollen cationic starch / anionic water-soluble polymer combination to form a complex prior to the addition of the filler, and They can be added to the sheared and treated filler suspension to develop crosslinked filler particles. These treatment methods can produce a homogeneous filler suspension that is stable during prolonged storage.

  The treated filler suspension can be introduced directly into the pulp slurry, or can be diluted if desired, and at the entrance of a sheet forming process (eg, mixing chest, machine chest, or fan pump). ) Can be added to the pulp stock of the paper machine. The introduction of the treated filler into the pulp suspension causes agglomeration of the pulp slurry. However, the degree of aggregation is affected by the level of shear and the residence time. In general, treated filler suspensions tend to maintain agglomeration characteristics over time when added to a papermaking pulp slurry. Anionic microparticles (eg, including but not limited to silica), anionic polymers (eg, including but not limited to CMC) or conventional polymeric retention to improve filler retention Improving agents (such as but not limited to polyarylamides) can be added to the furnish, preferably before or at the headbox or pressure screen. Retention and drainage improved substantially upon the addition of silica or CMC to the pulp stock containing the treated filler.

(Example 3)
A 0.3% strength stock was prepared by mixing the internal cationic starch with a pulp furnish, followed by pre-treated PCC, and finally a retention modifier. An 80 g / m ² wood-free handsheet was made using a dynamic sheet former (DSF) followed by dynamic sheet pressing and dried at 120 ° C. Prior to paper testing, the paper sheet was calendered under the same conditions and then placed under conditions of 50% relative humidity and 22 ° C.

The raw materials used in the sheet making were:
Fiber: 100% eucalyptus was used as the pulp and was beaten to a SR value of 30 (at 20 ° C.) using a Valley Beater lab beater.
Filler: Specialty Minerals Inc. Precipitated calcium carbonate (Albacar LO PCC), average particle size 2.3 μm. The PCC content in the sheet varied between 19.3% and 25.9% by weight.
Swelled cationic starch used for PCC pretreatment: Cationic potato starch. The swollen cationic starch was prepared by mixing dry cationic starch powder with water to make a 3% solids slurry and then heated to 63 ° C. with mixing. The swollen cationic starch was used for PCC pretreatment by mixing 20% solid swollen cationic starch of 5 kg / metric ton (metric ton) paper with PCC. Some filler samples were only pretreated with swollen cationic starch, and some were pretreated with swollen starch and anionic co-additives.
Co-additives used for PCC pretreatment with swollen cationic starch: anionic micropolymer (TELIOFORM M305®, registered trademark of BASF). PCC treatment was performed by mixing swollen cationic starch and anionic micropolymer with PCC. Different addition sequences were used and the amount of swollen cationic starch was fixed on 5 kg / metric ton paper while the amount of anionic micropolymer was 0.05% as received material / dry PCC weight. Yes and 0.1% as received material / dry PCC weight.
Internal starch: Cationic potato starch. The dried starch powder was mixed with water to obtain a 1% solid slurry, which was then digested at 97 ° C. with mixing. The cooked cationic starch was used at 8 kg / metric metric ton by mixing with pulp furnish.
Retention modifier: 0.2 kg / metric ton of cationic polyacrylamide (CPAM) was used for retention.

ＰＣＣ：沈降炭酸カルシウム、ＳＳＴ：カチオン性膨潤させられた澱粉、ＡＭＰ：アニオン性マイクロポリマー。
引張および剛性の値は、縦方向（ｍａｃｈｉｎｅ ｄｉｒｅｃｔｉｏｎ）および横方向（ｃｒｏｓｓ ｄｉｒｅｃｔｉｏｎ）からの幾何平均である。 Example 4
Table 1 shows the properties of sheets made from PCC treated with swollen starch only, and PCC treated with swollen starch followed by anionic micropolymer. The amount of anionic micropolymer was 0.05% to 0.1% as received material / dry PCC weight. Compared to PCC treated with only swollen starch, the sheet with anionic micropolymer in PCC pretreatment exhibits better strength properties-tensile, internal bond, bending stiffness. The best strength performance was achieved with the highest 0.1% / PCC anionic micropolymer content. This allows for an increase in filler by 6% without loss in strength properties.

PCC: precipitated calcium carbonate, SST: cationic swollen starch, AMP: anionic micropolymer.
Tensile and stiffness values are geometric means from the machine direction and the cross direction.

ＰＣＣ：沈降炭酸カルシウム、ＳＳＴ：カチオン性膨潤させられた澱粉、ＡＭＰ：アニオン性マイクロポリマー
引張および剛性の値は、縦方向および横方向からの幾何平均である。 (Example 5)
Table 2 presents the properties of PCCs treated with swollen starch only, and sheets made with PCC treated with starch and anionic micropolymers swelled using different order of addition: swollen PCC treated with an anionic micropolymer following the modified starch, and a PCC treated with the starch that was subsequently swollen after being treated with the anionic micropolymer. The presence of anionic micropolymers improves the strength properties of sheets made of PCC treated with swelled starch independent of the order of addition.

PCC: precipitated calcium carbonate, SST: cationic swollen starch, AMP: anionic micropolymer tensile and stiffness values are geometric averages from the machine and transverse directions.

(Example 6)
These microscopic images in FIG. 6 illustrate how the starch granules swell and how the viscosity increases until it begins to decrease due to breakage of the swollen starch granules. These images show samples of corn starch at 25 ° C, 56 ° C, 60 ° C, 66 ° C, and 95 ° C.

  For the purposes of the present invention, the swollen starch begins with the majority of the granules beginning to swell as in the 56 ° C image, and the large swollen granules as seen in the 66 ° C image. Characterized to the point that it is still visible. Thus, along with microscopic images, the viscosity curve can be used to determine when the starch is swollen for use in preparing the filler suspension of the present invention. The maximum viscosity region in FIG. 5 is where most of the starch granules are swollen but not broken. The temperature range over which useful swollen starch granules can be obtained is in the peak region of FIG. 5 +/− 10 ° C., where most starch granules are swollen but still completely broken. Absent. The temperature at which the preferred raw starch granule suspension is heated is peak + 10 ° C., where all starch granules are swollen and all unswelled granules are excluded.

  All patents and patent applications cited herein are hereby incorporated by reference as if each individual patent and patent application was clearly and individually described herein. Although the claimed invention has been described in terms of various embodiments, those skilled in the art will recognize that various changes, substitutions, omissions and changes may be made without departing from the spirit of the invention. Therefore, it is intended that the scope of the invention be limited only by the scope of the following claims, including equivalents thereof.

Claims (19)

A filler suspension for use in papermaking comprising:
Filler particles;
Swollen cationic starch, and
An anionic water-soluble polymer;
A filler suspension.   The filler suspension according to claim 1, wherein the anionic water-soluble polymer is lightly crosslinked.   The filler suspension according to claim 2, wherein the anionic lightly crosslinked water-soluble polymer has a tan delta rheological vibration value at 0.005 Hz of at least 0.5 in a 1.5% aqueous solution.   The filler suspension according to any one of claims 1 to 3, wherein the anionic lightly crosslinked water-soluble polymer comprises sodium acrylate, acrylamide and methylenebisacrylamide.   The filler suspension according to claim 1, wherein the anionic water-soluble polymer is TELIOFORM® M305.   The filler suspension according to claim 2, wherein the anionic water-soluble polymer is TELIOFORM® M305.   The filler suspension according to claim 1, wherein the filler particles are selected from the group consisting of viscosity, talc, heavy calcium carbonate, chalk, precipitated calcium carbonate, precipitated calcium sulfate, and combinations thereof. The filler suspension according to claim 1, wherein the cationic starch granules are swollen with hot water at a gel point temperature of the cationic starch of ± 10 ° C without cooking the cationic starch.
  The filler suspension according to claim 8, wherein the temperature at which the cationic starch granules are swollen is the gel point temperature + 10 ° C.   The filler suspension according to claim 1, wherein the filler particles have a size of 1 to 10 microns.   The filler suspension according to claim 1, wherein the swollen cationic starch granules have a size of 25 to 100 microns.   Based on the total solid content of the filler suspension, the filler particles are present in an amount of 60 to 99.5% by weight and the swollen cationic starch is 35 to 0.499% by weight. And the anionic water-soluble polymer is present in an amount of from 5.0 to 0.001% by weight.   A pulp furnish comprising pulp fibers and a filler suspension according to claim 1.   The pulp furnish of claim 12, further comprising a co-additive selected from the group consisting of sizing agents, wet strength agents, retention modifiers, and combinations thereof.   A paper comprising the pulp furnish according to claim 13 or 14.   A process for producing a filler suspension for papermaking comprising contacting filler particles with swollen cationic starch and anionic water-soluble polymer.   The process of claim 16, wherein the anionic, water-soluble polymer is lightly crosslinked.   A process for producing paper, comprising contacting the filler suspension of claim 1 with pulp fibers to form a pulp furnish; discharging the pulp furnish through a wire; Forming a sheet; and drying the sheet.   The process of claim 18, wherein the pulp furnish further comprises a co-additive selected from the group consisting of a sizing agent, a wet strength agent, a dry strength agent, a retention modifier, and combinations thereof.

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