KR100810389B1 - Filler for papermaking process - Google Patents

Abstract

The present invention includes cellulose derivatives and calcium salts having a degree of substitution of total ionic groups of about 0.65 or less and relates to fillers substantially free of fibrous or microfibers of cellulose or lignocellulosic. The invention also relates to fillers comprising calcium salts and cellulose derivatives containing a cationic group having a total ionic group substitution degree of about 0.65 or less. The present invention also relates to a method for preparing a filler comprising the step of mixing a calcium salt-containing material with a cellulose derivative having a total ionic substitution degree of about 0.65 or less in the substantially absence of fibrous or microfibers of cellulose or lignocellulosic. do. The present invention also relates to a method of making a filler comprising mixing a calcium salt-containing material with a cellulose derivative having a total ionic group substitution degree of about 0.65 or less and containing a cationic group. The present invention also relates to a filler obtainable by the above method. The invention also provides an aqueous suspension containing cellulose fibers, comprising cellulose derivatives and calcium salts having a total ionic group substitution degree of about 0.65 or less, substantially free of fibrous or microfibers of cellulose or lignocellulose And a process for introducing the filler into the suspension, and dehydrating the suspension to form a paper web or sheet. The present invention also relates to a papermaking process comprising the steps of: providing an aqueous suspension containing cellulose fibers, introducing into the suspension a filler comprising a cellulose derivative and a calcium salt having a total ionic group substitution degree of about 0.65 or less and containing a cationic group And dewatering the suspension to form a paper web or sheet.

Description

FILLER FOR PAPERMAKING PROCESS}

The present invention relates to fillers comprising calcium salts and cellulose derivatives.

The present invention also relates to a method of preparing a filler, the use of a filler in papermaking, a papermaking process in which the filler is used as an additive and a paper comprising the filler.

Background of the Invention

Highly filled papers tend to be established in the paper industry due to improved product quality, such as higher opacity and better printability, as well as savings in terms of reduced fiber use. Typically calcium carbonate-based fillers are used because of their better light scattering properties. A major drawback in the manufacture of highly filled papers, especially papers with high surface area fillers, is the large consumption of sizing agents. Therefore, as the filler content in the paper increases, a larger amount of sizing agent is needed to obtain the corresponding sizing results. Therefore, as the amount of filler increases, the suspension is more difficult to size.

Sizing is mainly performed to realize water repellency in paper or board and to reduce edge wicking. Sizing will also affect the mechanical properties of the paper and board, such as specification stability, coefficient of friction, flexibility, and fracture strength. In addition, sizing can improve printability by controlling ink application and ink adhesion.

The sizing process involves the precipitation of hydrophobic materials, commonly referred to as size agents, on the fibrous surface. Commonly used size agents are, for example, non-cellulose-reactive size agents such as rosin-based size agents, and cellulose-reactive size agents such as, for example, alkyl ketone dimers ("AKD"), and alkenyl succinic anhydrides ("ASA"). Acid anhydrides such as "). However, it is known that cellulose-reactive sizing agents, ie, AKD and ASA, undergo hydrolysis to compete with the intended fiber. Moreover, sizing loss can occur in the final product due to product size conversion or size migration, size evaporation, mechanical wear, and the like.

Bartz and co-workers have observed that while the fluidity of AKD wax is increased, some AKD can be trapped after penetrating into the porous structure of the filler (Bartz, W .; Darroch, ME; FL, "Alkyl ketene dimer sizing efficiency and reversion in calcium carbonate filled papers ", Tappi Journal, Vol. 77, No. 12,1994). This occurs in particular in the form of the triangular form of the PCC, which has a porous rosette structure and high surface area. Voutilainen has shown that high surface area fillers adsorb AKD much better than fiber (Voutilainen, P., "Competitive Adsorption of Alkyl Ketene Dimer on Pulp Fibers and CaC0 ₃ Fillers", Proceedings from International Paper and Coating Chemistry Symposium, 1996). The presence of Al- and Si-oxides on the filler surface can additionally adsorb cationic starch contained in the AKD particles. It has also been suggested that there is a strong interaction or perhaps even a bond between AKD and calcium carbonate filler. This proposed mechanism with fillers is of course undesirable and efforts should be made to minimize this interaction.

To improve sizing efficiency, US Pat. No. 5,514,212 suggests that the surface of the pigment can be modified using anionic starch-soap composites. Cooked starch of corn or potatoes is synthesized with fatty acid salts and settles onto the pigment surface when mixed with a hard calcium slurry or paper finish containing high levels of calcium ions.

U. S. Patent 5,972, 100 proposes a system consisting of cellulose-reactive sizing agents (such as AKD), cationic dispersants (such as cationic starch or polyamides) and fillers. The present invention separately enables independent control of both filler loading and sizing in addition to improved sizing.

Moreover, WO 95/13324 refers to calcium carbonate treated with cellulose derivatives such as sodium carboxymethyl cellulose (“CMC”) having a degree of substitution of 0.7. The treated calcium carbonate is used as a filler in alkaline papermaking suspensions to increase the whiteness of the paper.

U. S. Patent No. 3,730, 830 discloses a method of making paper, in particular a method of making photo paper, comprising the use of synthetic polymer fibers. Prior to adding the synthetic fibers to the fibrous suspension, an inorganic pigment or carbon is added to the slurry containing carboxymethyl cellulose and synthetic fibers, thereby achieving uniform dispersion of the polymer fibers between the cellulose fibers in the paper stock.

There is still a need for fillers that provide improved papermaking processes and produced paper of better properties. It would be desirable to provide fillers that allow the manufacture of highly filled papers that exhibit excellent print and mechanical properties. It would also be desirable to provide a filler that reduces the demand for sizing thereby resulting in improved sizing efficiency. It would also be desirable to provide fillers that are compatible with dehydration and retention agents and that result in good dehydration, retention and paper machine operability. It would also be desirable to provide a simple and efficient method for preparing fillers exhibiting these properties.

Summary of the Invention

The present invention generally relates to fillers comprising calcium salts and cellulose derivatives. The present invention also generally relates to fillers comprising calcium salts and carboxyalkyl cellulose derivatives. The present invention also generally relates to a process for preparing a filler by mixing a calcium salt-containing material with a cellulose derivative, the use of the filler as an additive in papermaking and a paper comprising the filler. The present invention also generally relates to a papermaking process in which filler is introduced into an aqueous cellulose suspension.

More particularly, the present invention relates to fillers comprising calcium salts and cellulose derivatives having a total ionic group substitution degree of about 0.65 or less. The present invention also relates to a filler comprising a calcium salt and a cellulose derivative having a degree of substitution of carboxyalkyl groups of about 0.65 or less. The present invention also relates to a method of making a filler comprising mixing a calcium salt-containing material with a cellulose derivative having a total ionic group substitution degree of about 0.65 or less. The present invention also relates to a method of preparing a filler comprising mixing a calcium salt-containing material with a cellulose derivative having a degree of substitution of carboxyalkyl groups of about 0.65 or less. The present invention also relates to fillers obtainable by these methods. The present invention also provides an aqueous suspension containing cellulose fibers, introducing into said suspension a filler comprising a cellulose derivative and calcium salt having a total ionic degree of substitution of about 0.65 or less, and dehydrating said suspension. It relates to a papermaking process comprising the step of forming a paper web or sheet. The present invention also provides an aqueous suspension containing cellulose fibers, introducing a filler comprising a cellulose derivative having a carboxyalkyl group substitution degree of about 0.65 and a calcium salt into the suspension, and dehydrating the suspension to provide a paper web. Or a papermaking process comprising the step of forming a sheet. In the papermaking process, the filler may be introduced into the suspension by adding the calcium salt and the cellulose derivative together as a single composition.

Detailed description of the invention

The present invention provides new fillers suitable for use in papermaking. The fillers according to the present invention have surprisingly been found to reduce some of the problems associated with fillers commonly used in papermaking and incorporated into paper. More specifically, by using the filler of the present invention in the papermaking process, excellent printability such as high smoothness, high opacity and whiteness, improved mechanical properties such as dry strength, tensile strength, Scott bond and flexural rigidity, and improved It is possible to provide a paper having a sizing effect. Additional advantages exhibited by the present invention include excellent improved dewatering and fine retention, which bring advantages with regard to the operability of the paper machine.

It has been observed that when fillers are used with sizing agents, the present invention reduces the sizing demand and, therefore, can generally improve sizing efficiency. Improved sizing efficiency is seen with respect to different types of sizing agents including non-cellulose and cellulose-reactive sizing agents, in particular cellulose-reactive sizing agents such as ketone dimers and acid anhydrides. In particular, the present invention provides improved sizing efficiency and sizing stability of filled paper when fillers with high filler loads and / or high surface areas are used.

According to the invention, it was unexpectedly observed that during a simple process, the cellulose derivative could be mixed with the calcium salt-containing material and more effectively adsorbed or attached onto the calcium salt-containing material. Fillers of the invention can be considered modified fillers, or cellulose derivative-treated fillers.

According to the present invention, it has been found that very good results can be obtained by adding the calcium salt-containing material and cellulose derivative together in a pre-mixed or pre-treated form to the cellulose suspension. Pre-treatment of calcium salt-containing materials with cellulose derivatives provides a convenient way to prepare modified fillers by individually treating only one component of the cellulose suspension, wherein the modified fillers can replace conventional fillers or It may be used in part. Without being limited by any theory, it is believed that the cellulose derivative is adsorbed to the calcium salt-containing material when mixing the components.

Fillers according to the present invention include calcium salts and cellulose derivatives. Examples of suitable calcium salts are calcium carbonate, calcium sulfate and calcium oxalate, preferably calcium carbonate, and mixtures thereof. Calcium carbonate is a major constituent in limestone, marble, chalk and dolomite. Calcium carbonate can be obtained directly from the above mentioned natural stone, which is referred to as heavy calcium carbonate ("GCC"). Calcium carbonate may also be prepared synthetically, which may be commonly referred to as hard calcium carbonate ("PCC").

Calcium carbonate is preferably obtained from materials that produce carbonate ions in the aqueous phase, such as alkali metal carbonates or carbon dioxide, and calcium hydroxide. In the present invention, both GCC and PCC, preferably PCC, can be used, and they are present, for example, as rhombus crystals, prismatic, tubular, cuboidal and cuboidal forms, and agarite in the form of needles. To include any of a variety of crystalline forms. Typically the PCC has a surface area of about 2 to about 20 m ² / g, suitably about 7 to about 12 m ² / g.

Calcium salts may be present as inherently pure calcium salts and may comprise a mixture of one or more calcium salts. It may also be present in the form of a mixture with one or more other ingredients. As used herein, the term "calcium salt-containing material" refers to a material comprising calcium salt, and optionally one or more other ingredients. Examples of other components suitable for this type include the fibrous or microfibers of cellulose, or similar vegetable materials, inorganic clay, kaolin, talc, titanium dioxide, hydrogenated aluminum oxide, barium sulfate, and the like. Preferably, when other ingredients are used, they are suitable for use in papermaking.

In calcium salt-containing materials comprising fibrous or microfibers of cellulose or lignocellulosic, or similar vegetable materials, at least the calcium salt portion can be deposited on the fibrous or microfibers. The average thickness of the microfibers may be about 0.01 to about 10 μm or less, suitably about 5 μm or less, and preferably about 1 μm or less. The average length of the microfibers may be about 10 μm to about 1500 μm or less. Examples of suitable calcium salt-containing materials include US Pat. No. 5,731,080; 5,824,364; 6,251,222; 6,375,794; And 6,599,391, which are hereby incorporated by reference. A commercially available type of this composite is SuperFill® from M-Real Oy.

Fillers according to the invention also comprise cellulose derivatives. The cellulose derivative may be water soluble or at least water soluble or water-dispersible, preferably water soluble or at least partially water soluble. Preferably, the cellulose derivative is ionic. The cellulose derivative may be anionic, cationic or amphoteric, preferably anionic or amphoteric. Examples of suitable cellulose derivatives are, for example, cellulose ethers, such as anionic and amphoteric cellulose ethers, preferably anionic cellulose ethers. Cellulose derivatives preferably have ionic groups or charged groups, or substituents. Examples of suitable ionic groups are anionic groups and cationic groups.

Examples of suitable anionic groups include carboxylates such as carboxyalkyl, sulfonates such as sulfoalkyl, phosphates and phosphonate groups, where the alkyl groups can be methyl, ethyl, propyl and mixtures thereof, suitably methyl ; Suitably the cellulose derivative contains an anionic group comprising a carboxylate group such as a carboxyalkyl group. The counter-ion of the anionic group is usually an alkali or alkaline earth metal, suitably sodium.

Examples of suitable cationic groups of the cellulose derivative according to the invention include salts of amines, suitably salts of tertiary amines, and quaternary ammonium groups, preferably quaternary ammonium groups. Substituents attached to the nitrogen atom of the amine and the quaternary ammonium group may be the same or different and may be selected from alkyl, cycloalkyl, and alkoxyalkyl groups, and one or more substituents may form a heterocyclic ring with the nitrogen atom. . Substituents typically comprise 1 to about 24 carbon atoms, preferably 1 to about 8 carbon atoms, independently of one another. The nitrogen of the cationic group can be attached to cellulose or a derivative of cellulose by means of an atomic chain, suitably comprising carbon and hydrogen atoms and optionally comprising O and / or N atoms. Typically an atomic chain has 2 to 18, suitably 2 to 8 carbon atoms, optionally interrupted or substituted by one or more heteroatoms such as O or N, such as, for example, alkyleneoxy groups or hydroxy propylene groups Alkylene group. Preferred cellulose derivatives containing cationic groups are obtained by reacting a cellulose or a derivative of cellulose with a quaternizing agent selected from 2, 3-epoxypropyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and mixtures thereof. Derivatives.

The cellulose derivative of the present invention is hydroxymethyl, hydroxyethyl, hydroxypropyl, alkyl or hydroxy alkyl groups such as hydroxybutyl, hydroxyethyl methyl, hydroxypropyl methyl, hydroxybutyl methyl, hydroxyethyl ethyl, hydroxy Mixtures thereof, such as oxypropyl, and the like. In a more preferred embodiment of the invention, the cellulose derivative contains both ionic and non-ionic groups.

Examples of suitable cellulose derivatives according to the invention include carboxyalkyl celluloses such as carboxymethyl cellulose, carboxyethyl cellulose, carboxypropyl cellulose, sulfoethyl carboxymethyl ("CM-HEC"), carboxymethyl cellulose, preferably carboxymethyl Cellulose (“CMC”), wherein the cellulose is substituted with one or more non-ionic substituents. Suitable cellulose derivatives and methods for their preparation include those disclosed in US Pat. No. 4,940,785, which is hereby incorporated by reference.

According to a preferred embodiment of the present invention, the filler comprises a cellulose derivative containing a cationic group and a calcium salt containing fibrous or microfibers of cellulose or lignocellulosic. The cationic group may be one of the cationic groups listed in the present application.

In another preferred embodiment of the invention the filler comprises calcium salts substantially free of fibrous or microfibers of cellulose or lignocellulose, and cellulose derivatives which may be anionic, cationic or amphoteric.

As used herein, the term "degree of substitution" or "DS" refers to the number of substituted ring sites in the beta-anhydroglucose ring of the cellulose derivative. Since there are three substitutable hydroxyl groups on each anhydroglucose ring of cellulose, the maximum value of DS is 3.0. In one preferred embodiment of the invention, the cellulose derivative has a total ionic group substitution degree (“DS _NI ”) of about 0.65 or less, ie, the cellulose derivative has an average total ion substitution degree of about 0.65 or less per unit of glucose. Total ion substitution can be total anionic, total cationic or total neutral. When the total ion substitution is total anionic, there is an excess of total anionic groups (total anion group = average number of anionic groups per glucose unit-if present, average number of cationic groups), and DS _NI is the substitution of the total anionic group Same as the degree (“DS _NA ”). When the total ion substitution is total cationic, there is an excess of total cationic groups (total cationic group = average number of cationic groups per glucose unit-if present, the average number of anionic groups), and DS _NI is the total cationic group substitution Same as the degrees ("DS _NC "). When the total ion substitution is total neutral, if present, the average number of anion and cationic groups per glucose unit is the same, and DS _NI and DS _NA and DS _NC are zero. According to another preferred embodiment of the invention, the cellulose derivative has a carboxyalkyl group substitution degree (“DS _CA ”) of about 0.65 or less, ie, the cellulose derivative has an average carboxyalkyl substitution degree of about 0.65 or less per glucose unit. . The carboxyalkyl group is suitably a carboxymethyl group, wherein the DS _CA mentioned here is equal to the degree of substitution of the carboxymethyl group ("DS _CM "). According to this embodiment of the present invention, typically DS _NI , DS _NA , DS _NC and DS _CA are independently of each other about 0.60 or less, suitably about 0.50 or less, preferably about 0.45 or less, more preferably 0.40 or less On the other hand, DS _NI , DS _NA , DS _NC and DS _CA are usually independently of each other at least 0.01, suitably at least about 0.05, preferably at least about 0.10 and more preferably at least about 0.15. Typically the ranges of DS _NI , DS _NA , DS _NC and DS _CA are independently from each other about 0.01 to about 0.60, suitably about 0.05 to about 0.50, preferably about 0.10 to about 0.45 and more preferably about 0.15 to About 0.40.

DS _{NI and} DS _NA are suitably herein about 0.05, preferably about 0.10, and more preferably about 0.15, to suitably about 0.75 or less, preferably about 0.5 or less, and more preferably about If defined below 0.4, anionic or amphoteric cellulose derivatives typically have an anionic substitution degree (“DS _A ”) in the range of 0.01 to about 1.0. The DS _NI and DS _NC herein suitably are about 0.02, preferably about 0.03, and more preferably about 0.05, to about suitably about 0.75 or less, preferably about 0.5 or less, and more preferably about If defined below 0.4, the cationic or amphoteric cellulose derivative may have a cationic degree of substitution (“DS _C ”) in the range of 0.01 to about 1.0. The cationic group is suitably a quaternary ammonium group, where the DS _C mentioned here is equal to the degree of substitution of the quaternary ammonium group (“DS _QN ”). With respect to amphoteric cellulose derivatives of the present invention, if DS _NA and DS _NC are each defined herein, then DS _A or DSc is of course higher than 0.65. For example, if DS _A is 0.75 and DSc is 0.15, DS _NA is 0.60.

Examples of suitable cellulose derivatives having a degree of substitution as defined above are water soluble low DS carboxyalkyl cellulose derivatives disclosed in the co-pending patent application filed under the name Akzo Nobel N. V. on the same. The water-soluble cellulose derivative is suitably 85% by weight, preferably 90% by weight, more preferably 95% by weight, and most preferably 98% by weight in an aqueous solution based on the total weight of the dry cellulose derivative. Has solubility.

Typically the cellulose derivative has an average molecular weight of at least 20,000 Daltons, preferably at least 50,000 Daltons, and the average molecular weight is usually at most 1,000,000 Daltons, preferably at most 500,000 Daltons.

Preferably, in the fillers according to the invention, the cellulose derivative is at least partially adsorbed or attached to the calcium salt or other components present in the calcium salt-containing material. Suitably, at least about 10%, preferably at least about 30%, more preferably at least about 45%, and most preferably at least about 60% by weight of the cellulose derivative is present in the calcium salt-containing material Adsorbed or attached to calcium salts or other components.

Fillers according to the invention typically have a calcium salt content of at least 0.0001% by weight; The calcium salt content is about 0.0001 to about 99.5 weight percent, suitably about 0.1 to about 90 weight percent, and preferably about 60 to about 80 weight based on the solid weight of the filler, ie based on the dry weight of the filler Can be%. Fillers typically have a cellulose derivative content of at least 0.01% by weight; The cellulose derivative content is about 0.01 to about 30 weight percent, suitably about 0.1 to about 20 weight percent, and preferably about 0.3 to about 10 weight percent, based on the solid weight of the filler.

The filler according to the invention can be supplied as a solid material which can be essentially free of water. It may also be supplied as an aqueous composition. The aqueous phase, or the content of water, can vary within wide limits depending upon the method of preparation and intended use.

The invention also relates to calcium comprising a cellulose derivative, such as, for example, one of the cellulose derivatives defined herein, and a calcium salt and optionally one or more other components, such as, for example, one of the calcium salt-containing materials defined herein. A method of making a filler comprising mixing a salt-containing material. Cellulose derivatives and calcium salt-containing materials are suitably used in amounts to provide a filler according to the invention having a cellulose derivative and calcium salt content as defined herein.

Cellulose derivatives and calcium salt-containing materials used may be provided in solid or aqueous compositions, and mixtures thereof. The calcium salt-containing material is suitably provided as a finely divided material. Mixing can be accomplished by adding the cellulose derivative to the filler in a batch, semi-batch or continuous process, or vice versa. According to a preferred embodiment of the invention, the cellulose derivative is added to the aqueous composition of calcium salt-containing material as a solid, and the composition obtained is then subjected to an effective dispersion, suitably for dissolving the cellulose derivative. Preferably, the mixing is carried out by first forming the neutral into the alkaline aqueous phase of the cellulose derivative, suitably with an aqueous solution, and then mixing with the aqueous composition of calcium salt-containing material. Prior to mixing with the calcium salt-containing material, the aqueous phase of the cellulose derivative is pre-treated, such as homogenization, centrifugation and / or filtration, for example, to separate the insoluble cellulose derivative from the aqueous phase if present. Pre-treatment such as

Preferably, the cellulose derivative is admixed with the calcium salt-containing material so that at least a portion of the cellulose derivative is adsorbed or attached onto the calcium-salt containing material, and is rarely removed from the material by dilution with water, preferably. This can be accomplished by performing the mixing for a long time sufficient to be able to adsorb on the attachment. Suitably the mixing time is at least about 1 minute, preferably at least about 5 minutes, more preferably at least about 10 minutes, and most preferably at least about 20 minutes. Several hours of mixing time (1-10 hours) are also possible if desired to achieve a high degree of adhesion. Suitably, at least about 10% by weight, preferably at least about 30% by weight, more preferably at least about 45% by weight and most preferably at least about 60% by weight of cellulose derivatives are transferred from the aqueous phase, containing calcium-salts Adsorbed or attached to calcium salts or other components present in the material.

The pH of the aqueous phase of the cellulose derivative is usually adjusted for adsorption of certain cellulose derivatives used at values of about 4 to about 13 hours, preferably about 6 to about 10, more preferably about 7 to about 8.5. Suitable bases or acids can be used to adjust the pH. Examples of suitable bases are bicarbonates and carbonates of alkali metals and alkali metal hydroxides, suitably sodium bicarbonate, sodium carbonate and sodium hydroxide. Examples of suitable acids are mineral acids, organic acids and acid salts, suitably their acid salts such as sulfuric acid and alum. In general, at lower pHs, ie from about 4.0 to neutral pH, the adsorption of the cellulose derivative is higher but the solubility is reduced, while at higher pH the adsorption is reduced but the solubility is increased.

The temperature is not strict; Under unpressurized conditions during operation, the temperature is typically from about 10 to about 100 ° C, preferably from about 20 to about 80 ° C. However, higher temperatures are more preferred and suitably the temperature of the aqueous composition during mixing is about 30 to about 70 ° C. or less, more preferably about 40 to about 60 ° C. or less.

When using calcium salt-containing materials that contain other ingredients, such as fibrous or microfibers of cellulose or lignocellulosic, in addition to calcium salts, the mixing and attachment of cellulose derivatives may occur simultaneously with or after sedimentation of calcium salts on the microfibers or fibrous Can be done on. It is also possible to add cellulose derivatives prior to sedimentation. In this case the cellulose derivative is added during or after the beating in a separate absorption step. The cellulose derivative may be adsorbed or attached onto the calcium salt-containing material or on the fiber or microfiber surface or may be absorbed into the fiber or microfiber. Methods for adsorbing similar cellulose derivatives to similar filler materials are described in US Pat. No. 5,731,080; 5,824,364; 6,251,222; 6,375,794; And 6,599,391, which are incorporated herein by reference.

Fillers obtained by the process of the invention can be used, for example, in papermaking. If the filler is present as an aqueous composition, it may be used directly or may be dried if necessary, for example to simplify transportation.

The present invention also provides an aqueous suspension containing cellulose fibers (“cellulose suspension”), such as introducing a filler of one of the fillers defined herein into the cellulose suspension, dehydrating the cellulose suspension to form a paper web or sheet. It relates to a paper manufacturing process comprising the step of forming a. Preferably, the filler is introduced into the cellulose suspension by adding it as a single composition. Alternatively, the calcium salt, or calcium salt-containing material (eg, one of the calcium salt-containing materials as defined herein), and the cellulose derivative (eg, one of the cellulose derivatives as defined herein), are individually added to the cellulose suspension. Fillers may be added in situ to the cellulose suspension.

In this process, other components may also be incorporated into the cellulose suspension. Examples of such ingredients include traditional fillers, optionally optical brighteners, size agents, dehydrating and retention agents, dry strength agents, wet strength agents, and the like. Examples of suitable traditional fillers include kaolin, clay, titanium dioxide, gypsum, talc, natural and synthetic calcium carbonates such as chalk, abrasive marble and precipitated calcium carbonate, hydrogenated aluminum oxide (aluminum trihydroxide), calcium sulfate, sulfuric acid Barium, calcium oxalate, and the like. When the fillers according to the invention are used together with conventional fillers, the fillers of the invention are based on the dry weight of all the fillers of at least 1% by weight, suitably at least 5% by weight, preferably at least 10% by weight, more preferably Is at least about 20% by weight, and suitably at most about 99% by weight. Examples of suitable sizing agents include, but are not limited to, non-cellulose-reactive sizing agents such as rosin-based soaps, rosin-based emulsions / dispersions, and alkenyl succinic anhydrides (ASA), alkenyl and Cellulose-reactive sizing agents such as emulsions / dispersions of acid anhydrides such as alkyl ketone dimers (AKDs) and multimers. Examples of suitable dehydrating and retaining agents include, for example, cationic, anionic and cationic polyethylene imines, cationic, anionic and nonionic polyacrylamides, cationic polyamines, cationic starches, and cationic guar. Organic polymer products such as non-ionic polymers; Inorganic materials such as aluminum compounds, anionic materials such as colloidal silica-based particles such as smectite type clays such as bentonite, montmorillonite; Colloidal alumina, and combinations thereof. Examples of suitable combinations of dehydration and retention agents include cationic polymers and anionic materials such as cationic starch and anionic colloidal silica-based particles, cationic polyacrylamides and bentonite or montmorillonite. Examples of suitable wet strength agents are polyamines and polyaminoamides. Paper containing fillers and cationic starches according to the invention exhibit very good strength properties.

According to a preferred embodiment of the invention, one or more size agents are introduced into the cellulose suspension to produce a sized paper containing the filler. Preferably, the sizing agent is a cellulose-reactive sizing agent of the type mentioned herein. Suitable ketene dimers have the general formula (I) below, wherein R ¹ and R ² represent saturated or unsaturated hydrocarbon groups, usually saturated hydrocarbon groups, and the hydrocarbon groups suitably have 8 to 36 carbon atoms, typically Straight or branched chain alkyl groups having 12 to 20 carbon atoms, such as hexadecyl and octadecyl groups. The ketene dimer may be liquid at ambient temperature, ie 25 ° C., suitably 20 ° C. Typically, acid anhydrides can be characterized by the following general formula (II), where R ³ and R ⁴ are the same or different and suitably represent saturated or unsaturated hydrocarbon groups containing 8 to 30 carbon atoms, R ³ and R ⁴ together with the —COC— moiety may form a 5 to 6 membered ring, optionally further substituted with a hydrocarbon group containing up to 30 carbon atoms. Examples of acid anhydrides used commercially are alkyl and alkenyl succinic anhydrides and in particular isooctadecenyl succinic anhydride.

Suitable ketene dimers, acid anhydrides and organic isocyanates include compounds disclosed in US Pat. No. 4,522,686, which is hereby incorporated by reference.

Fillers according to the invention can vary within wide limits, in particular depending on the type of cellulose suspension, the type of paper produced, the time of addition, and the like. Fillers are usually added in amounts ranging from 1 to about 50 weight percent, suitably from about 5 to about 40 weight percent, and typically from about 10 to about 30 weight percent, based on the dry fiber weight. Thus, the paper according to the invention is usually based on the dry fiber weight, the filler of the invention in the range of 1 to about 50% by weight, suitably about 5 to about 40% by weight, and usually about 10 to about 30% by weight. Has content.

When using other components in the process, these components may vary in a wide range, especially depending on the type and number of components, the type of cellulose suspension, the filler content, the type of paper produced, the time of addition, etc. May be added to the cellulose suspension. The sizing agent is typically introduced into the cellulose suspension in an amount of at least about 0.01% by weight, suitably at least about 0.1% by weight, based on the weight of the dry fiber, with an upper limit typically being about 2% by weight, preferably about 0.5% by weight. %to be. Dehydration and retention agents are generally introduced into cellulose suspensions in amounts that provide better dehydration and / or retention than those obtained when dehydration and retention agents are not used. Dehydration and retention agents, dry strength agents and wet strength agents, independently of one another, are usually introduced in amounts of at least about 0.001% by weight, often at least about 0.005% by weight, based on dry fibers, with an upper limit typically being about 5% and Suitably about 1.5% by weight.

The term "paper" as used herein includes not only paper and its manufacture, but also other cellulosic fibre-containing sheets or web-like products such as, for example, boards and cardboard and their manufacture. It can be used for making paper from aqueous suspensions of different types of cellulose (cellulose-containing) fibers, which suspension should suitably contain at least 25% by weight, preferably at least 50% by weight, based on the dry matter. . Cellulose fibers may be based on the first fibers and / or recycled fibers, including wood or annual or perennial plants. Cellulose suspensions may be wood-containing or wood-free, and include both fibrous, thermo-mechanical pulp, chemical thermomechanical pulp, refiner pulp and hardwood and softwood of chemical pulp such as sulfate, sulfite and organosolve pulp. It may be based on the fibers of mechanical pulp, such as groundwood pulp of, and may be based on recycled fibers, optionally deinking pulp, and mixtures thereof. The cellulose suspension suitably has a pH in the neutral to alkaline range, for example of about 6 to about 10, preferably about 6.5 to about 8.0.

The paper produced can be dried, coated and calendered. The paper may be coated with, for example, calcium carbonate, gypsum, aluminum silicate, kaolin, aluminum hydroxide, magnesium silicate, talc, titanium dioxide, barium sulfate, zinc oxide, synthetic pigments, and mixtures thereof.

The grammage of the paper produced can vary within wide limits depending on the type of paper produced; Typically the basis weight is in the range of about 20 to about 500 g / m ² , suitably about 30 to about 450 g / m ² , and preferably 30 to about 110 g / m ² . Preferably the present invention is used in the manufacture of uncoated or coated set paper, electrophotographic paper, uncoated or coated fine paper, and writing paper and printing paper, optionally containing mechanical pulp. do. Particularly preferred products are coated offset papers which combine high gloss and high opacity with high bulk.

The invention is further described in the following examples, which are not intended to limit the invention. Parts and percentages relate to parts by weight and percentages, respectively, unless stated otherwise.

Example  One

Fillers for comparison with fillers according to the invention were prepared by treating calcium salt-containing materials with cellulose derivatives. Cellulose derivatives used were carboxymethyl cellulose ( "CMC") with 0.3, 0.32 and 0.7 _NI of DS (DS = DS _{CM CA} = _A DS = DS = DS _{NA NI),} respectively. Another CMC used was DS _CA = DS _CM = DS _A = 0.4; DS _C = DS _QN = 0.17; And quaternary ammonium carboxymethyl cellulose ("QN-CMC") with DS _NI = DS _NA = 0.4-0.17 = 0.23. The average molecular weight of the cellulose derivatives used ranged from 100,000 to 400,000 .. The calcium salt-containing materials used were different precipitated calcium carbonates (“PCCs”) with surface areas of 5.7 and 10.0 m ² / g, respectively. Another calcium salt-containing material used was SuperFill® (PCC on pulp fines).

Fillers were prepared by dissolving CMC in water to a concentration of 0.5% by weight. The CMC composition obtained was then added to the PCC filler slurry and mixed at a temperature of about 50 ° C. for 25-45 minutes. Fillers according to the invention ("invented products") and fillers for control ("control products") are as follows:

Invention 1 ("IP1"): CMC (DS _NI 0.3) -treated PCC (5.7 m ² / g)

Invention 2 ("IP2"): CMC (DS _NI 0.3) -treated PCC (10 m ² / g)

Invention Product 4 ("IP4"): QN-CMC (DS _NI 0.23) -treated SuperFill®

Control Product 1 ("CP1"): CMC (DS _NI 0.7) -treated PCC (5.7 m ² / g)

Control Product 2 ("CP2"): SuperFill®

Control Product 3 ("CP3"): CMC (DS _NI 0.32) -treated SuperFill®

Example  2

The sizing of the paper made according to the invention was evaluated and contrasted with the paper used for control purposes. Paper according to the invention was made using IP1 of Example 1. The paper used for the control was prepared using CP1 of Example 1, and a filler containing no cellulose derivative was used.

Paper sheets were made of pulp containing various amounts of untreated PPC (% by weight, based on dry paper), as shown in Table 1, and composed of chemical pulp. A filler which contains 2.0 kg / ton of dry fiber of the filler according to Example 1 and no cellulose derivative in the suspension; 3.0 kg / ton of dry fiber of AKD (aqueous dispersion Eka Keydime C223) and a retention system (holding agent) comprising cationic starch (Eka PL 1510) and silica particles (Eka NP 780) were added. Both cationic starch and silica particles were added in an amount of 0.15 kg / ton dry fiber. The order of addition was as follows:

Addition of CMC-treated PCC: 0 seconds.

Addition of AKD dispersion: 30 seconds.

Addition of cationic starch: 45 seconds.

Addition of silica particles: 60 seconds.

Sheet formation: 75 seconds.

Sheets were prepared according to standard methods using Dynamic Sheet Former ("Formette", CTP Grenoble). The Cobb ₆₀ (SCAN-P 12:64) method was used to implement the sizing results. Table 1 shows the results obtained.

Test number. Paper PCC  content Filler Cobb ₆₀ One 18% CP1 45 2 19% IP1 25

Example  3

In this example, the papermaking process according to the present invention was evaluated, in which (i) CMC-treated PCC was added to the pulp suspension, and (ii) CMC and PCC (untreated) were separately added to the pulp suspension. Added.

Paper sheets were made from the same type of pulp as used in Example 2, and based on dry paper, 30% by weight of untreated PCC (surface area 10 m ² / g) or CMC (DS _NI 0.3) -untreated PCC (10 m ² / g) (IP2 according to example 1). 4 kg / ton of dry fiber of cationic starch (PB 970), 3.0 kg / ton of dry fiber of AKD (aqueous sizing dispersion Eka Keydime C223), and cationic polyacrylamide (Eka PL 1310) and silica particles in the pulp suspension A retention system containing (Eka NP 780) was added. Both cationic polyacrylamide and silica particles were added in an amount of 0.20 kg / ton of dry paper. When untreated PCC was used, 1.0 kg / ton of CMC with a DS _NI of 0.3 was added separately. When adding CMC-treated PCC, no CMC was added at all. The order of addition is as follows:

Addition of cationic starch: 0 seconds.

CMC-treated PCC / untreated PCC: 30 seconds.

Individual addition of CMC: 35 seconds.

Addition of AKD: 45 s.

Addition of cationic polyacrylamide: 60 seconds.

Addition of silica particles: 75 seconds.

Sheet formation: 90 seconds.

Paper sheets were evaluated as in Example 2. The results are shown in Table 2.

Test number. Addition method Filler Cobb ₆₀ One Added individually Unprocessed PCC + CMC 65 2 CMC-treated PCC addition IP2 35

Example  4

The product of Example 1 was used and evaluated in the papermaking process. A paper sheet was prepared in a similar manner to Example 3 from fibrous finished stock containing 70% by weight mixed hardwood pulp and 30% by weight softwood pulp refined at 22 ° and 25 ° SR, respectively. Untreated SuperFill® filler (CP2) or CMC-treated SuperFill® fillers (CP3 and IP4) were used and filler was added in an amount to provide a paper sheet containing 30% by weight of SuperFill® filler. It differs from the method of Example 3 only in that it is. The order of addition was as follows:

Addition of SuperFill®: 0 seconds.

Addition of cationic polyacrylamide: 45 seconds.

Addition of silica particles: 75 seconds.

Addition of AKD: 90 seconds.

The results are described in Table 3.

Test number. Filler Cobb ₆₀ One CP2 80 2 CP3 50 3 IP4 21

The present invention includes cellulose derivatives and calcium salts having a degree of substitution of total ionic groups of about 0.65 or less and relates to fillers substantially free of fibrous or microfibers of cellulose or lignocellulosic. The invention also relates to fillers comprising calcium salts and cellulose derivatives containing a cationic group having a total ionic group substitution degree of about 0.65 or less. The present invention also relates to a method for preparing a filler comprising the step of mixing a calcium salt-containing material with a cellulose derivative having a total ionic substitution degree of about 0.65 or less in the substantially absence of fibrous or microfibers of cellulose or lignocellulosic. do. The present invention also relates to a method of making a filler comprising mixing a calcium salt-containing material with a cellulose derivative having a total ionic group substitution degree of about 0.65 or less and containing a cationic group. The present invention also relates to a filler obtainable by the above method. The invention also provides an aqueous suspension containing cellulose fibers, comprising cellulose derivatives and calcium salts having a total ionic group substitution degree of about 0.65 or less, substantially free of fibrous or microfibers of cellulose or lignocellulose And a process for introducing the filler into the suspension, and dehydrating the suspension to form a paper web or sheet. The present invention also relates to a papermaking process comprising the steps of providing an aqueous suspension containing cellulose fibers, introducing into the suspension a filler comprising a cellulose derivative and a calcium salt having a total ionic group substitution degree of about 0.65 or less and containing a cationic group And dewatering the suspension to form a paper web or sheet.

Claims (25)

A cellulose derivative-treated filler composition comprising a cellulose derivative and a calcium salt having a total ionic group substitution degree of 0.65 or less, and free of fibrous or microfibers of cellulose or lignocellulosic. A cellulose derivative-treated filler composition having a total ionic group substitution degree of 0.65 or less and comprising a cellulose derivative and a calcium salt containing a cationic group. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the degree of substitution is at least 0.05. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the degree of substitution is 0.15 to 0.40. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the cellulose derivative is cellulose ether. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the cellulose derivative contains a carboxymethyl group. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the cellulose derivative contains quaternary ammonium groups. The cellulose derivative-treated filler composition according to claim 1, wherein the cellulose derivative is anionic. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the cellulose derivative is amphoteric. 3. The cellulose derivative-treated filler composition of claim 1 or 2, wherein the cellulose derivative is at least partially water soluble. 3. The cellulose derivative-treated according to claim 1 or 2, wherein the cellulose derivative-treated filler composition has a cellulose derivative content of 0.3 to 10% by weight based on the solid weight of the cellulose derivative-treated filler composition. Filler composition. 3. The cellulose derivative-treated according to claim 1 or 2, wherein the cellulose derivative-treated filler composition has a calcium salt content of 60 to 80% by weight based on the solid weight of the cellulose derivative-treated filler composition. Filler composition. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the calcium salt is calcium carbonate. 3. The cellulose derivative-treated filler composition according to claim 1 or 2, wherein the calcium salt is hard calcium carbonate. 3. The cellulose derivative-treated filler composition of claim 1 or 2, wherein the cellulose derivative-treated filler composition further comprises fibrous or microfibers of cellulose or lignocellulosic. 3. The cellulose derivative-treated filler composition of claim 2, wherein the cellulose derivative-treated filler composition is free of fibrous or microfibers of cellulose or lignocellulosic. A paper comprising the cellulose derivative-treated filler composition of claim 1. 18. The paper of claim 17 wherein the total filler composition content of the paper is from 5 to 40 weight percent based on the dry paper. A process for preparing a cellulose derivative-treated filler composition comprising mixing a calcium salt-containing material with a cellulose derivative having a total ionic group substitution degree of 0.65 or less in the absence of fibrous or microfibers of cellulose or lignocellulosic. A method of preparing a cellulose derivative-treated filler composition having a degree of substitution of carboxyalkyl groups of 0.65 or less and comprising mixing a calcium salt-containing material with a cellulose derivative containing a cationic group. A cellulose derivative-treated filler composition obtainable according to the method of claim 19 or 20. Providing an aqueous suspension containing cellulose fibers, introducing the cellulose derivative-treated filler composition of claim 1 into the suspension, and dehydrating the suspension to form a paper web or sheet. Paper manufacturing method comprising a. 23. The method of claim 22, wherein the cellulose derivative-treated filler composition is introduced to the suspension by adding a single composition containing calcium salt and cellulose derivative to the suspension. 23. The method of claim 22, wherein the cellulose derivative-treated filler composition is added in an amount of 5 to 30 weight percent based on dry fibers. 23. The method of claim 22, further comprising adding a cellulose-reactive sizing agent to the suspension.