ES2630379T3 - Loading material for a papermaking process - Google Patents

Abstract

A filler material comprising calcium salt and an anionic cellulose derivative having an anionic substitution degree of from 0.05 to 0.50, wherein the filler material is free of cellulose or lignocellulose fibers or fibrils.

Description

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DESCRIPTION

Loading material for a papermaking process

The present invention relates to a filler material comprising calcium salt and a cellulose derivative. The invention also relates to a method for obtaining the loading material, to the use of the loading material in papermaking, to a process for manufacturing paper in which the loading material is used as an additive as well as to the paper which It comprises the loading material.

Background of the invention

A paper highly filled with a filler material constitutes a trend established in the paper industry, not only due to the savings in the decreased use of fiber but also due to the improved quality of the product, such as higher opacity and better printability . Calcium carbonate-based fillers are commonly used, because of their superior light dissemination properties. A major disadvantage in the production of a paper filled in a high degree, particularly with loading materials having a high surface area, lies in the high consumption of a sizing agent. Therefore, as the content of the loading material in the paper increases, a greater amount of sizing agent is required in order to obtain corresponding sizing results. Therefore, cellulosic suspensions are more difficult to glue when the amount of the loading material increases.

Gluing is done mainly in order to achieve water repellency in a paper or cardboard and to reduce adsorption at the edges by wick effect. It will also affect the mechanical properties of paper and cardboard, such as dimensional stability, coefficient of friction, folding and folding resistance. Additionally, a sizing can improve printability, specifically by controlling the spread and adhesion of the ink.

The sizing process involves the deposition of hydrophobic substances, commonly referred to as sizing agents, on the surface of the fibers. Commonly used sizing agents are non-cellulose-reactive sizing agents, eg rosin-based sizing agents, and cellulose-reactive sizing agents, eg cetene alkyl dimer ("AKD") ) and acid antacids such as the antidrido of a sucquenic alkenyl acid ("ASAD"). It is known, however, that cellulose reactive sizing agents, ie AKD and ASA, undergo hydrolysis that competes with the desired reaction with the fibers In addition, there may be losses due to gluing in the final product due to the inversion or migration of the glue, the evaporation of the glue, the mechanical wear of the product, etc.

Bartz and colleagues have observed that during the presence an increased fluidity of an AKD wax, some AKD could penetrate and after that be trapped in the pore structure of the filler material (Bartz, W .; Darroch, ME; Kurrle, FL, "Efficiency and reversion of gluing with a dimer of alkyl cetena in papers filled with calcium carbonate", Tappi Journal, volume 77, No. 12, 1994). This occurs particularly with the scalenohedral form of a PCC, which has the porous rosette structure and a high surface area. Voutilainen has shown that loading materials with a high surface area adsorb the AKD even better than the fibers (Voutilainen, P., "Competitive adsorption of a dimer of alkyl cetena on pulp fibers and CaCO3 fillers", Proceedings from International Paper and Coating Chemistry Symposium, 1996). The presence of Al and Si oxides on the surface of the filler material can additionally adsorb a cationic starch contained in the AKD particles. It has also been proposed that there is a strong interaction or possibly even a union between the AKD and the calcium carbonate filler. These proposed mechanisms with the loading material are naturally unwanted, and efforts should be made to minimize this interaction.

To improve sizing efficiency, it is suggested in US Pat. 5,514,212 that the surface of the pigment can be modified with a complex of a starch and an anionic soap. Cooked starch from corn or potato is converted into a complex with fatty acid salts and precipitated on the pigment surfaces when mixed with a precipitated calcium suspension or with the papermaking supply material containing high levels of ions. of calcium

U.S. Pat. No. 5,972,100 suggests a system comprising a cellulose reactive tail (such as AKD), a cationic dispersing agent (such as a cationic starch or polyamides) and a filler. Apart from improved gluing, the invention allows independent control of both loading with the loading material and gluing separately.

In addition, the international patent application document WO 95/13324 refers to a calcium carbonate treated with a cellulose derivative such as a sodium carboxymethyl cellulose ("CMCD") having a degree of substitution of 0.7 . Said treated calcium carbonate is used as a loading material in alkaline papermaking suspensions, thereby increasing the brightness of the paper.

U.S. Pat. No. 3,730,830 discloses a process for making paper, specifically a photographic paper, comprising the use of synthetic polymer fibers. Prior to the addition of the synthetic fibers to the fiber suspension, an inorganic pigment or carbon is added to a suspension containing a carboxymethyl

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Cellulose and synthetic fibers, thus achieving a uniform dispersion of the polymeric fibers together with the cellulose fibers in the paper pulp.

WO 02/086238 discloses a filler material comprising cellulose or lignocellulose fibrils on which particles of a light disseminating material have been deposited, wherein an alkyl cellulose derivative is absorbed into the fibrils, and a process to prepare the loading material. Cellulose or lignocellulose fibrils are essential features of the invention.

EP-A 0 758695 refers to water dispersible sheets capable of easily resolving or dissolving in water, and to cigarettes using said water dispersible leaves. According to one form of the invention, the water dispersible sheet comprises a water-soluble base paper produced from a mixture of water dispersible fibers and a fibrous carboxymethyl cellulose acid or a fibrous carboxy ethyl cellulose acid. Water dispersible fibers are selected from cellulose fibers. The carboxymethyl cellulose fibrous salt and the carboxymethyl cellulose fibrous salt include a salt of an alkali metal or a mixed salt of a salt of an alkali metal and another salt such as a calcium salt. Such a mixture contains cellulose or lignocellulose fibers or fibrils, which are essential features of the invention.

The US patent application document U.S. 2003/188738 refers to a composition of filler material intended for use in papermaking, comprising particles of a filler material, swollen starch granules and a latex, in an aqueous carrier, where the particles of the material loading may be a calcium carbonate. The composition may optionally include concomitant additives for swollen starch granules and latex. Typically, concomitant additives are anionic, for example a carboxymethyl cellulose, but no degree of substitution for carboxymethyl cellulose is mentioned.

U.S. Patent Document 5,492,560 includes an inorganic filler material that has been treated with a cellulose derivative, preferably with a sodium carboxymethyl cellulose having a substitution degree of about 0.70. This US patent It refers to some mussels in the shine in the production of alkaline paper products containing fillers of the type of inorganic pigments.

There is still a need for a loading material that provides an improved papermaking process and better properties of the paper produced. It is desirable to provide a filler material that would make it possible to produce a paper filled in a high degree, showing excellent printing and mechanical properties. It is also desirable to provide a loading material that reduces the sizing demand and thus results in an improved sizing efficiency. It is also desirable to provide a loading material that is compatible with the auxiliary agents of drainage and retention and thus lead to good drainage, good retention and good machinability in the paper machine. It will also be desirable to provide a simple and efficient process for producing a loading material that shows the above characteristics.

Summary of the invention

The present invention generally relates to a filler material comprising calcium salt and an ionic cellulose derivative according to claim 1.

The invention also relates to a papermaking process according to claim 9.

Detailed Description of the Invention

The present invention provides a new load that is suitable for use in papermaking. It has surprisingly been found that the loading material according to the invention makes it possible to reduce some of the problems that are associated with the loading materials commonly used in papermaking and that are incorporated into a paper. More specifically, by using the loading material of this invention in papermaking processes it is possible to provide a paper with excellent printing properties, eg high smoothness, high opacity and high whiteness, improved mechanical properties, eg dry strength, tensile strength, Scott bonding and flexural stiffness, and an improved sizing effect. Additional advantages shown by the present invention include good and / or improved dehydration and retention of fine materials, which leads to benefits in terms of machinability in the paper machine.

When the filler material is used in conjunction with a sizing agent, it has been found that the present invention makes it possible to reduce the sizing demand and, therefore, generally improve the sizing efficiency. The improved sizing efficiency is exhibited for different types of sizing agents, including non-cellulose-reactive and cellulose-reactive sizing agents, specifically cellulose-reactive sizing agents such as cetena dfimers and acid anhydrides. In particular, the invention provides improved gluing efficiency and gluing stability of a filled paper, especially with high loading with a loading material and / or when loading materials with high surface areas are used.

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In accordance with the present invention it has also been observed, unexpectedly, that the cellulose derivative can be mixed with, and adsorbed on, or more effectively bound with, the material containing a calcium salt during a simple elaboration. The filler material of the present invention can be considered as an improved filler material or a filler material treated with a cellulose derivative.

In accordance with the present invention it has been found that very good results can be obtained by adding the material containing calcium salt and cellulose derivative to a cellulosic suspension together in a pre-mixed or pre-treated form. Pretreatment of the material containing the calcium salt with the cellulose derivative provides a convenient way to separately process only one component of the cellulosic suspension to produce a modified filler material, which can be used instead of or partially replacing the material of conventional load Without being bound to any teona, it is believed that the cellulose derivative is adsorbed by the material that contains the calcium salt when the components are mixed.

The filler material according to the invention comprises a calcium salt and a cellulose derivative. Examples of suitable calcium salts include calcium carbonate, calcium sulfate and calcium oxalate, preferably calcium carbonate, and mixtures thereof. Calcium carbonate is the main constituent in a limestone, a marble, a clay and a dolomite. Calcium carbonate can be obtained directly from the previous natural rock species mentioned above and referred to then as crushed calcium carbonate ("GCC" = acronym for ground calcium carbonate). Calcium carbonate can also be produced synthetically, which is commonly referred to as precipitated calcium carbonate ("PCC" acronym for precipitated calcium carbonate). Calcium carbonate is preferably obtained from calcium hydroxide and a material that produces carbonate ions in the aqueous phase, such as an alkali metal carbonate, or carbon dioxide. Both a GCC and a PCC, preferably a PCC, can be used in the present invention, including any of the various crystalline forms or morphologies that exist, eg a rhombohedral, prismatic, tabular, cuboid and scalenoedcal calcite and an aragonite in an acicular way. The PCC usually has a specific area of from about 2 to about 20 m2 / g, suitably from about 7 to about 12 m2 / g.

The calcium salt may be present in the form of an essentially pure calcium salt, including mixtures of one or more calcium salts. It may also be present in the form of a mixture together with one or more other components. The term "material containing a calcium salt", as used in the present context, refers to a material comprising a calcium salt, and optionally one or more other components. Examples of other suitable components of this type include inorganic clays, caolm, talc, titanium dioxide, hydrogenated aluminum oxides, barium sulfate, etc. Preferably, when used, the other components are suitable for use in papermaking.

The filler material according to the invention further comprises a cellulose derivative. It is preferred that the cellulose derivative be soluble in water or at least partially soluble in water or dispersible in water, preferably soluble in water or at least partially soluble in water. The cellulose derivative is ionic. The cellulose derivative can be anionic or amphoteric, preferably anionic. Examples of suitable cellulose derivatives include cellulose ethers, eg anionic and amphoteric cellulose ethers, preferably anionic cellulose ethers. The cellulose derivative preferably has ionic or charged groups, or substituents. Examples of suitable ionic groups include anionic and cationic groups. Examples of suitable anionics include a carboxylate, eg carboxyalkyl, a sulfonate, eg sulfoalkyl, phosphate and phosphonate groups in which the alkyl group can be methyl, ethyl, propyl and mixtures thereof, suitably methyl; suitably the cellulose derivative contains an anionic group comprising a carboxylate group, eg a carboxyalkyl group. The opposite sign ion of the anionic group is usually an alkali metal or an alkaline earth metal, suitably sodium.

Examples of suitable cationic groups of cellulose derivatives according to the invention include amine salts, suitably tertiary amine salts, and quaternary ammonium groups, preferably quaternary ammonium groups. The substituents attached to the nitrogen atom of the amines and the quaternary ammonium groups may be the same or different and may be selected from alkyl, cycloalkyl and alkoxyalkyl groups, and one, two, or more of the substituents together with the nitrogen atom may form a heterodclic ring. The substituents, independently of one another, usually comprise from 1 to about 24 carbon atoms, preferably from 1 to about 8 carbon and hydrogen atoms and optionally O and / or N atoms. Usually the atom chain is an alkylene group with from 2 to 18 and suitably from 2 to 8 carbon atoms, optionally interrupted or substituted with one or more heteroatoms, eg O or N, such as an alkyleneoxy group or a hydroxy propylene group. Preferred cellulose derivatives containing cationic groups include those obtained by reacting a cellulose or a derivative thereof with a quaternization agent selected from 2,3-epoxypropyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride and mixtures thereof.

The cellulose derivatives of this invention may contain non-ionic groups such as alkyl or hydroxy alkyl groups, eg hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and mixtures thereof, eg hydroxyethyl methyl, hydroxypropyl methyl, hydroxybutyl methyl, hydroxyethyl ethyl, hydroxypropyl, and the like. In a preferred embodiment of the invention, the cellulose derivative contains both ionic and non-ionic groups.

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Examples of suitable cellulose derivatives according to the invention include carboxyalkyl cellulose, eg a carboxymethyl cellulose, a carboxymethyl cellulose, a carboxypropyl cellulose, a sulfoethyl carboxymethyl cellulose, a carboxymethyl hydroxyethyl cellulose ("CM-HEC"), a carboxymethyl cellulose wherein the cellulose is substituted with one or more non-ionic substituents, preferably a carboxymethyl cellulose ("CMC"). Examples of appropriate cellulose derivatives and methods for their preparation include those disclosed in US Pat. No. 4,940,785, which is incorporated by reference herein.

In a preferred embodiment of the invention, the filler material comprises a calcium salt that is free of cellulose or lignocellulose fibers or fibrils, and a cellulosic derivative that can be either anionic or amphoteric.

The terms "degree of substitution" or "DS", as used in the present context, mean the number of substituted ring sites of the beta-anhydroglucose rings of the cellulose derivative. Since there are three hydroxyl groups in each cellulose anhydroglucose ring, which are available for substitution, the maximum value of DS is 3.0.

According to the invention, the cellulose derivative has a degree of substitution of net ionic groups ("DSni") of up to about 0.60, that is, the cellulose derivative has an average degree of net ionic substitution per glucose unit of up to 0.60. The net ionic substitution is net anionic or net neutral. When the net inonic substitution is net anionic, there is an excess of anionic groups (net anionic groups = the average number of anionic groups minus the average number of cationic groups, if any, per glucose unit) and DSni is the same as the degree of substitution of net anionic groups ("DSna"). When the net neutral substitution is net neutral, the average number of ccationic and anionic groups, if any, per unit of glucose, is the same, and DSni, as well as DSna are 0. According to another preferred embodiment of the invention, the Cellulose derivative has a degree of substitution of carboxyalkyl groups ("DSca") up to about 0.60, that is to say that the cellulose derivative has an average degree of substitution with carboxyalkyl per unit of glucose up to about 0.60. The carboxy alkyl groups are suitably carboxymethyl groups and then the DSca referred to herein is the same as the degree of substitution of carboxymethyl groups ("DScm"). According to these embodiments of the invention, DSni, DSna, and DSca independently from each other are up to 0.60, suitably up to 0.50, preferably up to about 0.45 and more preferably up to 0.40, while DSni, DSna , and DSca are independently from each other usually at least 0.01, suitably at least about 0.05, preferably at least about 0.10, and more preferably at least about 0.15. The ranges of DSni, DSna, and DSca are independently from sf from about 0.01 to 0.60, suitably from about 0.05 to about 0.50, preferably from about 0.10 to about 0.45 and more preferably from about 0.15 to about 0.40.

Cellulose derivatives that are anionic or amphoteric normally have an anionic substitution gradient ("DSa") in the range of from 0.01 to about 1.0 as long as DSni and DSna are as defined herein; suitably from about 0.05, preferably from about 0.10, and more preferably from about 0.15 to 0.60, preferably to about 0.5, and more preferably to about 0.4. Cellulose derivatives that are amphoteric may have a degree of cationic substitution ("DSc") in the range of from 0.01 to about 1.0 as long as DSni is as defined herein; suitably from about 0.02, preferably from about 0.03 and more preferably from about 0.05 and suitably to about 0.75, preferably to about 0.5 and more preferably to about 0.4. The cationic groups are suitably quaternary ammonium groups and then DSc referred to herein is the same as the degree of substitution of the quaternary ammonium groups ("DSQN"). For amphoteric cellulose derivatives of this invention DSa or DSc may of course be higher than 0.65 as long as DSna and DSnc, respectively, are as defined in the present context. For example, if DSa is 0.75 and DSc is 0.15 then DSna is 0.60.

Examples of suitable cellulose derivatives that have degrees of substitution as defined above include those derived from a water soluble carboxyalkyl cellulose with a low DS, which are disclosed in corresponding patent applications also pending, filed on behalf. of Akzo Nobel NV on the same date. The water soluble cellulose derivatives suitably have a solubility of at least 85% by weight, based on the total weight of the dried cellulose derivative, in an aqueous solution, preferably at least 90% by weight, more preferably by at least 95% by weight, and most preferably at least 98% by weight.

The cellulose derivative usually has an average molecular weight that is at least 20,000 Daltons, preferably at least 50,000 Daltons, and the average molecular weight is usually up to 1,000,000 Daltons, preferably up to 500,000 Daltons.

Preferably, in the filler material according to the invention, the cellulose derivative is at least part adsorbed onto or bound to the calcium salt or other components present in the material containing the calcium salt. Suitably, at least about 10% by weight, preferably at least 30% by weight, more preferably at least about 45% by weight and most preferably 60% by weight of the derivative of

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Cellulose is adsorbed onto or bound to the calcium salt or other components present in the material that contains the calcium salt.

The filler material according to the invention usually has a calcium salt content of at least 0.0001% by weight, the calcium salt content can be from about 0.0001 to about 99.5% suitably from about 0.1 to about 90% by weight, and preferably from about 60 to about 80% by weight, based on the weight of the solid materials of the filler material, that is based on the dry weight of the filler material . The filler material usually has a cellulose derivative content of at least 0.01% by weight; the content of the cellulose derivative may be from about 0.01 to about 30% by weight, suitably from about 0.1 to about 20% by weight, and preferably from about 0.3 to about 10% by weight, based on the weight of the solid materials of the load material.

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

The present invention also relates to a method of manufacturing a filler material comprising mixing a cellulose derivative, for example any of the cellulose derivatives defined herein, with a material containing a calcium salt, for example , any of the materials containing calcium salt defined herein, comprising calcium salt, and optionally one or more other components. The cellulose derivative and the material containing calcium salt are suitably used in amounts such that they provide a filler material according to the invention having cellulose derivative contents and calcium salt as defined herein.

The cellulose derivative and the material containing the calcium salt used may be present as solids or in aqueous compositions, and mixtures thereof. The material that contains the calcium salt is properly present as a finely divided material. The mixture can be achieved by adding the cellulose derivative or vice versa, in a batch, semi-continuous or continuous process. According to a preferred embodiment of the invention, the cellulose derivative is added as a solid to an aqueous composition of the material containing the calcium salt and the composition obtained below is suitably subjected to effective dispersion to dissolve the cellulose derivative, Preferably, The mixture is made by first signing an aqueous phase from neutral to alkaline, suitably an aqueous solution, of cellulose derivative, which is then mixed with an aqueous composition of material containing the calcium salt. Before mixing with the material containing the calcium salt the aqueous phase of cellulose derivative can be subjected to a pretreatment, for example, homogenization, centrifugation and / or filtration, for example to separate undissolved cellulose derivative, if there would be, of the aqueous phase.

Preferably, the cellulose derivative is mixed with the material containing the calcium salt to allow at least that part of the cellulose derivative is adsorbed on or attached to the material containing the calcium salt, preferably so that it is difficult to remove from the material by dissolution with water, This can be done by carrying out the mixing in a period of time that is sufficient to allow adsorption on the joint. Suitably, the mixing time is at least about 1 min, preferably at least about 5 min, more preferably at least about 10 min, and most preferably at least about 20 min. Without possible mixing periods of even several hours (1 -10 h) if a high degree of union is desired. 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 60% by weight of the cellulose derivative is transferred from the aqueous phase and adsorbed on or attached to the calcium salt or other components present in the material containing the calcium salt.

The pH of the aqueous cellulose derivative phase is usually adjusted by sorption of the specific cellulose derivative used to a value of from about 4 to about 13, preferably from about 6 to about 10, more preferably from about 7 to about 8.5 . A suitable base or acid can be used to adjust the pH. Examples of suitable bases include alkali metal bicarbonates and carbonates and alkali metal hydroxides, suitably sodium bicarbonate, sodium carbonate and sodium hydroxide. Examples of suitable acids include mineral acids, organic acids and acid salts, suitably sulfuric acid and its acid salts, such as alum. In general, at a lower pH, that is, at a pH of about 4.0 to neutral, the adsorption of the cellulose derivative is increased, but the solubility decreases, while at a higher pH the adsorption is redone but the solubility increases.

The temperature is not critical, in operations under non-pressurized conditions the temperature is typically from about 10 to about 100 ° C, preferably from about 20 to about 80 ° C. However, higher temperatures are more favorable, suitably the temperature of the aqueous composition during mixing is from about 30 to about 70 ° C, more preferably from about 40 to about 60 ° C.

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When a material containing a calcium salt is used that also contains other components in addition to the calcium salt, e.g., cellulose or lignocellulose fibers or fibrils, the mixing and joining of the cellulose derivative can be performed simultaneously with the precipitation of the calcium salt on the fibrils or fibers or after the precipitation. It is also possible to add the cellulose derivative before precipitation. In that case, the cellulose derivative is added either during tapping or in a separate sorption after tapping. The cellulose derivative can be adsorbed on or bonded to the surfaces of the material containing the calcium salt or fiber or fibril and / or sipped into the fibers or fibrils. Adsorption methods of cellulose derivatives similar to similar fillers are described in US Pat. Nos. 5,731,080; 5,824,364; 6,251,222; 6,375,794; and 6,599,391, the descriptions of which are incorporated herein by reference.

The filler material obtained by the method of the invention can be used as such, for example in papermaking. If present as an aqueous composition, it can be used directly or dried, if desired, for example, to simplify transport.

The present invention relates to a process for the production of paper, which comprises providing an aqueous suspension containing cellulosic fibers (= "cellulosic suspension"), introducing a filler material into the cellulosic suspension, eg any of the materials of load that have been defined here, and dehydrate the cellulosic suspension to form a continuous band or a sheet of paper. Preferably the filler material is introduced into the cellulosic suspension by adding it as a single composition. Alternatively, the calcium salt or the material containing the calcium salt (eg any one of the materials containing a calcium salt, which have been defined here and the cellulose derivative (eg any of the Cellulose derivatives which have been defined here can be added separately to the cellulosic suspension and the filler material is formed in situ in the cellulosic suspension.

In the process, other components can of course be introduced into the cellulosic suspension. Examples of such components include conventional fillers, optical brightening agents, sizing agents, auxiliary agents for drainage and retention, agents for conferring dry strength, agents for conferring wet strength, etc. Examples of suitable conventional fillers include caolm, a china clay, titanium dioxide, a gypsum, a talcum, natural and synthetic calcium carbonates, eg a clay, a crushed marble and precipitated calcium carbonate, oxides of Hydrogenated aluminum (aluminum trihydroxides), calcium sulfate, barium sulfate, calcium oxalate, etc. When the filler material according to the invention is used in conjunction with a conventional filler material, the filler material according to the invention can be present in a proportion of at least 1% by weight, suitably of at least 5 % by weight, preferably at least 10% by weight, more preferably at least about 20% by weight and suitably up to about 99% by weight, based on the dry weight of all fillers. Examples of suitable sizing agents include non-cellulose reactive sizing agents, eg rosin-based sizing agents, such as rosin-based soaps, rosin-based emulsions / dispersions and sizing agents reactive with cellulose, eg emulsions / dispersions of acid anhydrides such as sucralle alkenyl anhydrides (ASA), alkenyl and alkyl ketene dimer (AKD) and multimers. Examples of suitable auxiliary agents for drainage and retention include organic polymeric products, eg cationic, anionic and non-ionic polymers that include cationic polyethylene imines, cationic, anionic and non-ionic poly (acrylamides), polyamines cations, a cationic starch and a cationic guar: inorganic materials, eg aluminum compounds, anionic microparticulate materials such as colloidal silica based particles, smectite type clays, eg a bentonite, a Montmorillonite; a colloidal alumina, and combinations thereof. Examples of appropriate combinations of auxiliary drainage and retention agents include cationic polymers and microparticulate materials eg anionic particles based on a cationic starch and a colloidal silica, a cationic polyacrylamide and particles based on a colloidal silica. anionic as well as a cationic polyacrylamide and a bentonite or montmorillonite. Examples of suitable wet strength conferring agents include polyamines and polyaminoamides. A paper containing fillers according to the invention and a cationic starch shows very good strength properties.

According to a preferred embodiment of the invention, at least one sizing agent is introduced into the cellulosic suspension to produce a glued paper containing a filler. Preferably, the sizing agents are cellulose reactive sizing agents, of the types mentioned herein. Suitable cetena dimers have the following general formula (I), wherein R1 and R2 represent saturated or unsaturated hydrocarbyl groups, usually saturated hydrocarbons. the hydrocarbyl groups having suitably 8 to 36 carbon atoms, these being usually straight or branched chain alkyl groups having 12 to 20 carbon atoms, such as the hexadecyl and octadecyl groups. Cetena dimers may be liquid at room temperature, that is at 25 ° C, suitably at 20 ° C. Currently, acid anhydrides can be characterized by the following general formula (II), wherein R3 and R4 can be identical or different and represent saturated or unsaturated hydrocarbyl groups that suitably contain 8 to 30 carbon atoms or where R3 and R4, together with the radical -COC-, can form a 5 to 6 member ring, which is optionally further substituted with hydrocarbyl groups containing up to 30 carbon atoms. Examples of commercially used acid anhydrides include succinic alkyl and alkenyl anhydrides and particularly succinic isooctadecenyl anhydride.

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(i) R1 — CH

 :C -

 0 X 1 * (il) O or

 one

 one

   II

 one

 or-

 or II or R3- i 0 1 0 1 -c-

Suitable cetena dimers, acid acids and organic isocyanates include the compounds disclosed in US Pat. No. 4,522,686 which is incorporated herein by reference.

The filler material according to the invention can be added to the cellulosic suspension in proportions that can vary within wide limits, depending, among other things, on the type of cellulose suspension, on the type of paper produced, on the site of the addition. , etc. The filler material is usually added in a proportion within the range of from 1 to about 50% by weight, suitably from about 5 to about 40% by weight, and usually from about 10 to about 30% by weight, based on in the weight of dry fibers. Correspondingly, the paper according to the invention usually has a content of the filler material of the invention that is within the range of from 1 to about 50% by weight, suitably from about 5 to about 40% by weight and usually from about 10 to about 30% by weight, based on the weight of dry fibers.

When other components are used in the process, these components can be added to the cellulosic suspension in proportions that can vary within wide limits, depending, among other things, on the type and number of components, on the type of cellulosic suspension, on the content of loading material, the type of paper produced, the site of the addition, etc. Sizing agents are usually introduced into the cellulosic suspension in a proportion of at least about 0.01% by weight, suitably at least about 0.1% by weight, based on the weight of dry fibers, and the upper limit it is usually about 2% by weight, suitably about 0.05% by weight. Generally, auxiliary agents for drainage and retention are introduced into the cellulosic suspension in proportions that

provide better drainage and / or retention than what is obtained when these agents are not used

auxiliary Auxiliary drainage and retention agents, dry strength conferring agents and wet strength conferring agents, independently of each other, are usually introduced in a proportion of at least about 0.001% by weight, often of least

about 0.005% by weight, based on dry fibers, and the upper limit is usually of

about 5% and suitably about 1.5% by weight.

The term "paper", as used in the present context, includes not only a paper and its production but also other products in the form of sheets or continuous bands, containing cellulosic fibers, such as for example cardboard and cardboard , and their production. The process can be used in the production of paper from different types of aqueous suspensions of cellulosic fibers (containing cellulose) and the suspensions should suitably contain at least 25% by weight and preferably at least 50% by weight of said fibers, based on a dry substance. The cellulosic fibers may be based on virgin fibers and / or recycled fibers, including annual or perennial wood or plant fibers. The cellulosic suspension can contain wood or be free of wood, and can be used in fibers from a chemical paste, such as sulfate, sulphite and organosolve process pastes, a mechanical paste such as a thermomechanical paste, a chemo paste. thermo-mechanics, a refiner pulp and a crushed wood pulp from both hardwood and softwood and can also be based on recycled fibers, optionally from pastes and mixtures thereof. The cellulosic suspension suitably has a pH in the range from neutral to alkaline, eg from about 6 to about 10, preferably from about 6.5 to about 8.0.

The paper produced can be dried, coated and calendered. The paper can be coated with, for example, calcium carbonate, gypsum, aluminum silicate, caolm, aluminum hydroxide, magnesium silicate, talc, titanium dioxide, barium sulfate, zinc oxide, a synthetic pigment and mixtures of the same.

The weight of the paper produced may vary within wide limits, depending on the type of paper produced, usually the weight is within the range of from about 20 to about 500 g / m2, suitably from about 30 to about 450 g / m2 and preferably from 30 to approximately 110 g / m2. Preferably, the invention is used for the production of an uncoated or coated offset printing paper, an electrophoto paper, a thin, uncoated and coated paper that optionally contains a mechanical paste, as well as writing and printing papers. A particularly preferred product is a coated offset printing paper, in which high gloss and high opacity and bulkiness are combined.

The invention is further illustrated in the following Examples, which, however, are not intended to limit it. Parts and% refer to parts by weight and% by weight respectively unless otherwise indicated.

Example 1

The fillers according to the invention and by comparison were prepared by treating the material containing the calcium salt with cellulose derivatives. The cellulose derivatives used were carboxymethyl celluloses ("CMC") having DSni (DSca = DScm = DSa = DSna = DSni) of 0.3, 0.32 and 0.7, respectively, Other CMC used were 5 carboxymethyl celluloses of quaternary ammonium ("QN-CMC") that have DSca = DScm = DSa = 0.4; DSc = DSqn = 0.17; and DSni = DSna = 0.4 - 0.17 = 0.23. The degree of molecular weights of the cellulose derivatives used was in the range of from 100,000 to 400,000. The materials containing calcium salt used were different precipitated calcium carbonates ("PCC") having a specific surface area of 5.7 and 10.0 m2 / g, respectively. Another material containing calcium salt used was SuperFill ® (PCC on pulp fines).

10 The fillers were prepared by dissolving CMC in water at a consistency of 0.5% by weight. Then, the CMC composition obtained was added to the PCC filler suspension and mixed for 25 to 45 minutes at a temperature of approximately 50 ° C. The loading materials according to the invention ("Pridcuto of the Invention") and by comparison ("Comparison Product") were the following:

 Product of Invention 1 ("IP1"):

 CMC (DSni 0.3) -PCC treated (5.7 m2 / g)

 Product of Invention 2 ("IP2"):

 CMC (DSni 0.3) - PCC treated (10 m2 / g)

 Product of Invention 4 ("IP4"):

 QN-CMC (DSni 0.23) - SuperFill ® treated.

 Comparison Product 1 ("CP1"):

 CMC (DSni 0.7) - PCC treated (5.7 m2 / g)

 Comparison Product 1 ("CP2"):

 SuperFill ®.

 Comparison Product 3 ("CP3"):

 CMC (DSni 0.32) - SuperFill ® treated

15 Example 2

The gluing of the paper produced according to the invention was evaluated and compared to the paper used for comparison purposes. The paper according to the invention was produced using IP1 according to Example 1. The paper used for comparison was produced using CP1 according to Example 1 and using non-cellulose-derived filler material.

Paper sheets were produced from pulp consisting of chemical pulp and containing untreated PCC in 20 variable amounts (% by weight, based on dry paper), as indicated in Table 1. To the pulp suspension were added 2.0 kg / tonne of dry fibers of cargo material according to Example 1 and non-counting material that does not contain cellulose, 3.0 kg / ton of dry fibers of AKD (aqueous dispersion of Eka Keydime C223), and a retention system comprising cationic starch (Eka PL 1510) and silica particles (Eka Np 780). Both cationic starch and silica particles were added in an amount of 0.15 kg / ton of dry fibers. 25 The sequence of addition was as follows:

Addition of CMC-PCC treated: 0 s

AKD dispersion addition: 30 s

Adding cationic starch: 45 s

Addition of silica particles: 60 s

30 Sheet formation: 75 s

The sheets were obtained according to a standard method using Dynamical Sheet Former ("Formette", CTP Grenoble). The Cobb60 method (SCAN-P 12:64) was used to establish the sizing results. Table 1 shows the results obtained.

Table 1

 Essay No.

 PCC paper content Cobb60 loading material

 one

 18% CP1 45

 2

 19% IP1 25

Example 3

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

Paper sheets of the same type used in Example 2 and containing 30% by weight, based on 5 dry paper, of untreated PCC (specific area of 10 m2 / g) or CmC (DSni0.3) -PCC treated were produced (10 m2 / g) (IP2 according to Example 1). To the pulp suspension were added 4 kg / ton of dry cationic starch fiber (PB 970), 3.0 kg / ton of dry AKD fibers (Eka Keydime C223 aqueous gluing dispersion), and a retention system comprising cationic polyacrylamide (Eka PL 1310) and silica particles (Eka NP 780). 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 having a DSni of 0.3 was added separately. No separate addition of CMC was made when CMC-PCC treated was added. The sequence of addition was as follows:

 Adding cationic starch:

 0 s

 Addition of treated CMC-PCC / untreated PCC:

 30 s

 Separate addition of CMC:

 35 s

 Adding AKD:

 45 s

 Addition of cationic polyacrylamide:

 60s

 Addition of silica particles:

 75 s

 Sheet formation:

 90s

The sheets of paper were evaluated as in Example 2. The results are shown in Table 2. Table 1

 Test No.

 Addition Mode Load material Cobb60

 one

 Separately added untreated PCC + CMC 65

 2

 Add CMC-PCC treated IP2 35

fifteen

Example 4

The products of Example 1 were used and evaluated in papermaking processes. The paper sheets were manufactured from a fiber supplier containing 70% by weight of mixed hardwood pulp and 30% by weight of refined softwood at 22 ° and 25 ° SR, respectively, in a method similar to Example 3 except 20 that no cationic starch was used and use of untreated SuperFill® filler material (CP2) or treated CMC-SuperFill® filler material (IP3 and IP4), which was added in an amount to provide a sheet of paper containing 30% by weight of SuperFill ® filler. The sequence of addition was as follows:

 Adding SuperFill® loading material:

 0 s

 Addition of cationic polyacrylamide:

 45 s

 Addition of silica particles:

 75 s

 Adding AKD:

 90s

The results are shown in Table 3.

Table 3

 Essay No.

 Load material Cobbao

 one

 CP2 80

 2

 CP3 50

 3

 IP4 21

Claims (7)

1. A filler material comprising calcium salt and an anionic cellulose derivative having an anionic substitution degree of from 0.05 to 0.50, wherein the filler material is free of cellulose or lignocellulose fibers or fibrils . The loading material according to claim 1, characterized in that the degree of anionic substitution is 0.15 a 0.4. 3. The filler material according to claim 1 or 2, characterized in that the cellulose derivative is a cellulose ether. 4. The filler material according to one of the preceding claims, characterized in that the cellulose derivative 10 contains carboxymethyl groups. 5. The filler material according to one of the preceding claims, characterized in that the cellulose derivative is at least partially soluble in water. 6. The filler material according to one of the preceding claims, characterized in that the filler material has a calcium salt content of from 60 to 80% by weight, based on the weight of the solids of the filler material. The filler material according to one of the preceding claims, characterized in that the calcium salt is calcium carbonate. 8. The filler material according to one of the preceding claims, characterized in that the calcium salt is precipitated calcium carbonate. 9. A process for the production of paper comprising providing an aqueous suspension containing cellulosic fibers, introducing into the suspension a filler material according to any one of claims 1 to 8, and dehydrate the suspension to form a continuous web or a sheet of paper, where the process also comprises adding a cellulose reactive sizing agent to the suspension.