SK285211B6 - Aqueous dispersion containing sizing agent, method for preparation the same and using of it, composition containing sizing agent and using of it - Google Patents

Abstract

The invention relates to an aqueous dispersion containing a cellulose-reactive sizing agent and a dispersant system comprising a low molecular weight cationic organic compound having a molecular weight less than 10 000 and an anionic stabilizer, its preparation and use in the production of paper. The invention further re-lates to a substantially water-free composition containing a cellulose-reactive sizing agent, a low molecular weight cationic organic compound having a molecular weight less than 10 000 and an anionic stabilizer, its preparation and use in the preparation of an aqueous dispersion of cellulose-reactive sizing agent. Suitable anionic stabilizers for use in this invention include anionic compounds functioning as stabilizers and/or being effective in combination with the cationic compounds to stabilize the sizing agent in an aqueous phase as well as anionic compounds known as useful as dispersants in the preparation of size dispersions. Preferably the anionic compound is water-soluble or water-dispersable. The anionic stabilizer can be selected from organic or inorganic compounds and it can be derived from natural or synthetic sources.

Description

Technical field

The present invention relates to the sizing of paper and more specifically to the dispersion of cellulose-reactive sizing agents, their preparation and use.

BACKGROUND OF THE INVENTION

Cellulose-reactive glues such as alkyl ketene dimer (AKD) and substituted succinic anhydride (ASA) glues are widely used in paper making at neutral or slightly alkaline pH of the pulp to provide paper and cardboard with a degree of wetting and water penetration resistance fluids. Sizing paper based on cellulose-reactive sizing agents are usually provided in the form of dispersions comprising an aqueous phase and finely dispersed particles or sizing droplets dispersed therein. Dispersions are usually prepared in the presence of a dispersing system consisting of anionic compounds, such as sodium lignosulfonate, in combination with a high molecular weight amphoteric or cationic polymer, such as a cationic starch, polyamine, polyamide-amine or vinyl addition polymer. Depending on the overall charge of the compounds of the dispersing system, the glejacic dispersions may be cationic or anionic in nature. However, dispersions of these types usually tend to have poor stability and high viscosity, even at a relatively low solids content, which obviously leads to difficulties in handling dispersions, such as storage and use. A further disadvantage is that the products are to be supplied as low-concentration dispersions, which further increases the cost of transporting the active hydrophobic material.

Sizing agents usually provide good sizing even with a low dosage of sizing. However, the efficacy of conventional cellulose-reactive glues has been shown to be impaired when used with pulps that have high cationic requirements and contain substantial amounts of lipophilic wood extracts such as bitumen acids, fatty acids, fatty esters, triacylglycerols, etc. Due to the anionic nature of lipophilic substances containing carboxylate or carboxylic acid groups, pulps containing substantial amounts of lipophilic extracts usually have a higher cationic requirement. It has been found that lipophilic substances may be detrimental to the adsorption of sizing agents into fibers, causing poor sizing results. In order to improve the sizing of these papers, paper manufacturers need to increase the sizing batches, but this loses economic advantage and also leads to the accumulation of sizing in the white water recirculating in paper products. These problems are even more pronounced in paper mills, where white water is extensively recirculated with the supply of only small amounts of fresh water to the process, increasing the need for cations and accumulation of lipophilic extracts and non-retained glue in the white water and paper stock to be dewatered.

EP-A-275 851 relates to an aqueous sizing dispersion comprising a dispersion phase in the form of a sizing composition comprising a rosin-type substance and a synthetic size and furthermore a polyaluminium compound.

EP-A-208 667 relates to an aqueous sizing dispersion comprising a dispersion phase in the form of a mixture of sizing comprising a rosin-based substance and a synthetic size.

WO 96/17127 relates to an anionic size dispersion comprising a cellulose-reactive size.

EP-A-220 941 discloses a dry composition comprising a ketene dimer and an encapsulating agent which can be selected from gelatin, tristearin, acacia, sugar, ethylcellulose, carboxymethylcellulose, polyacrylamide, silicates, polyethers, polyesters, polyamides, starches and polyvinyl alcohol.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found that improved stability and sizing conditions can be obtained with aqueous dispersions of cellulose-reactive sizing agents in which the sizing agent is dispersed in the aqueous phase by a dispersion system comprising a low molecular weight cationic compound and an anionic stabilizer. The sizing dispersions according to the invention have excellent stability and low viscosity and are particularly suitable for the production of papermaking products which have high cationic requirements and / or contain large amounts of lipophilic substances.

It has also been found that the sizing improvement can be achieved by using these dispersions in papermaking processes where white water is recirculated extensively. More particularly, the present invention relates to an aqueous dispersion comprising a cellulose-reactive sizing agent and a dispersing system comprising a low molecular weight cationic compound and an anionic stabilizer, its preparation and uses as defined in the claims below.

The present sizing dispersions make it possible to produce paper with improved sizing over conventional sizing dispersions at an appropriate dosage of cellulose-reactive sizing and using a lower dose of cellulose-reactive sizing to obtain an appropriate level of sizing. The possibility of using lower amounts of sizing to achieve sizing in the description further reduces the risk of accumulating unadsorbed sizing in the white water recirculating in the process, thereby further reducing the risk of sizing aggregation and deposition in the paper machine. Thus, the present invention offers substantial economic and technical advantages.

The cellulose-reactive size according to the invention can be selected from any of the cellulose-reactive sizes known in the art. The sizing agent is preferably selected from the group consisting of hydrophobic ketene dimers, ketene multimers, acid anhydrides, organic isocyanates, carbamoyl chlorides and mixtures thereof, preferably ketene dimers and acid anhydrides, even more preferably ketene dimers.

Preferred ketene dimers have the general formula (I) below, wherein R ¹ and R ² are saturated or unsaturated hydrocarbon groups, usually saturated hydrocarbons, hydrocarbon groups preferably having 8 to 36 carbon atoms, usually straight or branched chain chains of 12 to 20 alkyl groups carbon atoms such as hexadecyl or octadecyl. Preferred acid anhydrides can be characterized by the general formula (II) below, wherein R ⁵ and R ⁴ may be the same or different and represent saturated or unsaturated hydrocarbon groups preferably containing 8 to 30 carbon atoms, or R ³ and R ⁴ together with the -COC moiety they may form a 5- to 6-membered ring which is preferably further substituted by a hydrocarbon group containing up to 30 carbon atoms. Examples of acid anhydrides that are commonly used include alkyl and alkenyl succinic anhydrides and especially isooctadecenyl succinic anhydride.

R ^! - CH = C - CH - P. ² ! and (f)

C - C »O

OC

II II (II) 'C - O - C - R' ·

Preferred ketene dimers, acid anhydrides and organic isocyanates include the compounds described in U.S. Patent 4,522,686, which is incorporated herein by reference. Examples of suitable carbamoyl chlorides include those described in U.S. Patent 3,887,427, which is also incorporated herein by reference.

In addition to the cellulose-reactive sizing agent, the sizing dispersions may also comprise a cellulose-non-reactive sizing agent. Examples of suitable sizing agents of this type include rosins such as esterified and / or fortified rosin, waxes, fatty acids and bituminous acid derivatives such as amides and fatty acid esters such as glycerol esters of natural fatty acids.

The dispersions of the present invention comprise a dispersant or dispersion system comprising a cationic organic compound and an anionic stabilizer. The compounds are preferably bound together by an electrostatic attraction force indicating coacervation of the dispersant. When used in combination, these compounds are effective as dispersants for the sizing agent, although the anionic and / or cationic compound may not be effective as a dispersant when used alone. Particularly preferred dispersions of the invention include those comprising a cationic surfactant and an anionic stabilizer as defined herein. In a preferred embodiment of the invention, the dispersion is anionic, thus the dispersion system has an overall anionic charge.

The cationic compound comprises one or more cationic groups of the same or different type and include cationic compounds with one cationic group and cationic compounds with two or more cationic groups, i.e. cationic polyelectrolytes. Examples of suitable cationic groups include sulfonium groups, phosphonium groups, acid addition salts of primary, secondary and tertiary amines or amino groups and quaternary ammonium groups, e.g. The cationic polyelectrolytes may have a degree of substitution varying within a wide range; the degree of cationic substitution (DS _C ) may be from 0.01 to 1.0, preferably from 0.1 to 0.8, and even more preferably from 0.2 to 0.6.

Preferred cationic organic compounds for use in the present invention include cationic compounds capable of functioning as a surfactant and / or dispersant and / or a coupling agent between particles or drops of the sizing agent and an anionic stabilizer. Preferably, the cationic compound is a surfactant. Preferred cationic surfactants include compounds of formula

R ₄ N ⁺ X ', wherein each R group is independently selected from (i) hydrogen;

(ii) hydrocarbon groups, preferably aliphatic and preferably alkyl groups having 1 to about 30 carbon atoms, preferably 1 to 22 carbon atoms; and (iii) hydrocarbon groups, preferably aliphatic and preferably alkyl groups having up to about 30 carbon atoms, preferably 4 to 22 carbon atoms, and which are interrupted by one or more heteroatoms such as oxygen or nitrogen and / or heteroatom containing groups such as carbonyl and acyloxy; wherein at least one, preferably at least three, and preferably all, said R groups contain carbon atoms; preferably at least one and preferably at least two of said R groups contain at least 7 carbon atoms, preferably at least 9 carbon atoms, and even more preferably at least 12 carbon atoms; and where

X 'is an anion, typically a halogen such as chloride, or an anionic group present in the anionic compound of the dispersant, i.e. where the surfactant is a protonated amine of formula

R ₃ N, wherein R and N are as defined.

Examples of suitable surfactants include dioctyldimethylammonium chloride, didecyldimethylammonium chloride, dicocodimethylammonium chloride, cocobenzyldimethylammonium, coco (fractionated) benzyldimethylammonium, oktadecyltrimetylamóniumchlorid, dieicosyl, dihexadecyl dimethylammonium chloride, di (hydrogenated lojjdimetylamóniumchlorid, di (hydrogenated tallow) benzylammonium chloride, (hydrogenated lojjbenzyldimetylamóniumchlorid, dioleyldimethylammonium chloride, di (ethylene) dimethyl Thus, particularly preferred cationic surfactants include those containing at least one C 9 -C 30 hydrocarbon group, and in particular quaternary ammonium compounds.

Other suitable cationic surfactants include quaternary di- and polyammonium compounds containing at least one hydrocarbon group, preferably aliphatic and preferably alkyl of 9 to 30 carbon atoms, preferably 12 to 22 carbon atoms. Examples of suitable surfactants of this type include N-octadecyl-N-dimethyl-N'-trimethylpropylene diammonium dichloride.

Preferred cationic polyelectrolytes further include low molecular weight cationic organic polymers, optionally degraded, i.e., those derived from polysaccharides such as starches and guar gums, cationic condensation products such as cationic polyurethanes, polyamidamines, such as polyamidamine-epichlorohydrin copolymers, such as polyamines, such as polyamines, dimethylamine-epichlorohydrin copolymers, dimethylamine-ethylenediamine-epichlorohydrin copolymers, ammonium ethylene dichloride copolymers, vinyl addition polymers formed from monomers having cationic groups, such as homopolymers and copolymers of diallyldimethylammonium acrylamide, present as acid addition salts or quaternary ammonium salts, optionally copolymerized with non-ionic monomers, including acrylamide, alkyl acrylates, styrene and acrylonitrile, and derivatives thereof, vinyl esters and the like.

The molecular weight of the cationic organic compound is usually up to about 10,000, usually up to about 5,000, preferably up to about 3,000 and preferably up to about 800. The molecular weight is usually at least about 200. Preferably, the cationic surfactants may have a molecular weight up to about 3,000 and preferably the surfactants have a molecular weight between about 200 and about 800.

Preferred anionic stabilizers for use in the present invention include anionic compounds functional as stabilizers and / or effective in combination with a cationic compound to stabilize the aqueous sizing agent, as well as anionic compounds known as dispersants in the preparation of sizing dispersions. Preferably, the anionic compound is water soluble or water dispersible. The anionic stabilizer may be selected from organic or inorganic compounds and may be derived from natural or synthetic sources. The anionic stabilizer of the dispersing system comprises one or more anionic groups of the same or different types and including anionic compounds with one anionic group and anionic compounds with two or more anionic groups, referred to herein as anionic polyelectrolyte. By anionic polyelectrolyte is meant to also include anionic compounds acting as polyelectrolytes, i.e., by chemical non-ionic interaction or attraction. In a preferred embodiment, the anionic stabilizer is an anionic polyelectrolyte. Examples of suitable anionic groups, i.e. groups that are anionic or behave as anionic in water, include phosphate, phosphonate, sulfate and sulfonate groups, sulfonic acid and carboxylic acid groups, and salts thereof, usually ammonium or alkali metal salts (usually sodium salts) ). The anionic groups may be original or introduced by chemical modification in a known manner. The anionic stabilizer may have a degree of substitution varying within a wide range; the degree of anionic substitution (DS _a ) may be from 0.01 to 1.4, preferably from 0.1 to 1.2, and more preferably from 0.2 to 1.0. The anionic polylelectrolytes may contain one or more cationic groups as long as they have a total anionic charge.

In a preferred embodiment, the anionic stabilizer is selected from organic compounds. Preferred anionic stabilizers of this type include polymeric compounds such as compounds based on polysaccharides such as starches, guargams, celluloses, chitins, chitosans, glycans, galactans, glucans, xanthan gums, mannans, dextrins, etc., preferably phosphated, sulfonated and carboxylated polysaccharides as well as synthetic organic polymers such as condensation products such as anionic polyurethanes and naphthalene-based polymeric anionic compounds such as condensed naphthalenesulfonates, and other vinyl addition polymers formed from anionic monomers such as acrylic acid, methacrylic acid, maleic acid , itaconic acid, crotonic acid, vinylsulphonic acid, sulphonated styrene and phosphates of hydroxyalkyl acrylates and methacrylates, optionally copolymerized with non-ionic monomers including acrylamide, alkyl acrylates, styrene and acrylonitrile, as well as derivatives thereof, vi nylesters and the like. Particularly preferred organic anionic stabilizers are anionic polysaccharides such as cellulose derivatives such as carboxymethylcellulose, condensed naphthalenesulfonates, anionic acrylamide-based polymers and polymers based on acrylic acid and similar acidic monomers.

In a preferred embodiment of the invention, the anionic stabilizer is hydrophobically modified and comprises at least one or more hydrophobic groups, preferably hydrophobically modified polysaccharides, preferably carboxymethylcellulose. Examples of suitable groups include hydrophobic substituents containing from 4 to about 30 carbon atoms, especially hydrophobic amide, ester and ether substituents containing a saturated or unsaturated hydrocarbon chain of at least 4 and preferably 8 to 30 carbon atoms, optionally interrupted by one or more heteroatoms such as oxygen or nitrogen and / or heteroatom-containing groups such as carbonyl or acyloxy. Preferred anionic polysaccharides, anionic hydrophobically modified polysaccharides, and methods for introducing hydrophobic substituents into polysaccharides are described, for example, in U.S. Patent 4,687,519 and in International Patent Application WO 94/24169, which are incorporated herein by reference. In another preferred embodiment, the anionic stabilizer is selected from inorganic anionic materials, preferably anionic inorganic polyelectrolytes, such as compounds containing silicon atoms, i.e., various forms of condensed or polymerized silicic acid having negative hydroxyl groups such as oligomeric silica, polysilicic acid. polysilicates and polyaluminosilicates.

The anionic stabilizer may also be selected from a microparticulate material containing both inorganic and organic anionic material. Suitable particulate materials of this type include highly cross-linked anionic vinyl and addition polymers such as acrylamide-based polymers and acrylate-based polymers, anionic condensation polymers such as melamine-sulfonic acid soles, inorganic silica-based materials such as those of the type aqueous silicas based soles such as silica soles, alumina silica soles, aluminosilicate soles, polysilicate microgels and polyaluminosilicate microgels, as well as silica gels and precipitated silica. The microparticulate material is preferably colloidal, i.e. with a particle size in the colloidal range. The colloidal particles preferably have a particle size of from about 1 nm to about 80 nm, preferably from 2 to 35 nm, and most preferably from 2 to 10 nm.

The molecular weight of the anionic compound can vary over a wide range from a few hundred or thousands to many millions. Usually the molecular weight is above 200 and preferably above 500, while the upper limit is usually 10 million and preferably 2 million. In a preferred embodiment, the molecular weight is up to about 50,000.

The amount of cationic and anionic compounds present in the dispersion according to the invention can vary widely, depending inter alia on the type and charge density of the cationic and anionic material, the type of sizing agent, the desired "anionicity" / "cation" and the solids content of the resulting dispersion. The present dispersion is preferably anionic and thus means that the anionic charge of the anionic stabilizer is higher than the cationic charge of the cationic compound. The cationic compound may be present in the dispersion in an amount of up to 100% by weight, usually from 0.01 to 20% by weight, preferably from 1 to 10% by weight and preferably from 2 to 7% by weight relative to the sizing agent, and the anionic stabilizer may be present. in an amount of up to 100% by weight, usually from 0.1 to 20% by weight, preferably from 0.2 to 10% by weight and preferably from 0.3 to 6% by weight with respect to the sizing agent, while the total charge of the cationic compound and anionic stabilizer which are not present in the dispersions is anionic or negative.

It has been found that the dispersions of the present invention can be prepared with high solid contents and yields and have very good storage stability and low viscosity. Thus, the present invention provides sizing dispersions with improved storage stability, higher solids content and / or lower viscosity. Another advantage expected with the present dispersions is an improvement in the dilution stability, which means less aggregation of glue particles or drops, thereby producing lower amounts of larger aggregates with lower sizing efficiency, as well as less deposition of the hydrophilic glue in the paper machine and less contamination contamination. necessity of paper machine maintenance. The present dispersions may generally have a sizing content of from about 0.1 to about 50% by weight and preferably above 20% by weight. Dispersions containing a ketene dimer as the size according to the present invention should have a ketene dimer content of from 5 to about 50% by weight and preferably from about 10 to about 35% by weight. The dispersion or emulsion containing the acid anhydride as the sizing agent according to the invention should have an acid anhydride content in the range of from about 0.1 to about 30% by weight and usually from about 1 to about 20% by weight.

The dispersions according to the invention can be produced by mixing the aqueous phase with an anionic stabilizer, a cationic compound and a sizing agent, preferably at a temperature at which the sizing agent is liquid, and homogenizing the mixture thus obtained, preferably under pressure. Suitable temperatures for the ketene dimer sizing compositions are in the range of about 55 ° C to about 95 ° C, while lower temperatures can be used for acid anhydrides. The resulting emulsion, which contains glue drops of a conventional size from 0.1 to 3.5 µm in diameter, is then cooled. Other materials such as anionic and non-ionic dispersants and stabilizers, diluents such as urea and urea derivatives, and preservatives may also be incorporated into the size dispersion. It is contemplated that the negative and positive charges of the dispersing system compounds may be formed in situ, for example by bringing the compounds into contact with each other and / or by mixing the compounds with the aqueous phase and / or lowering the pH of the aqueous phase. For example, the loss of hydrogen from the acidic group creates an anionic charge and the basic amine or amine group can be converted to cationic protonation or hydrogen removal. Therefore, it is possible to start with non-charged compounds when preparing the dispersion. For example, an organic compound with a basic amino group or a basic amine of the formula R 11 N can be used, wherein during the preparation the corresponding ammonium moiety R 11 N 'X' is formed, where R, N and X can be as defined.

It has been found that the components of the present dispersions can be readily homogenized in the presence of an aqueous phase. Usually, these processes require less energy and lower shear forces compared to processes for preparing conventional dispersions, and thus a simpler device can be used. Thus, a further process for preparing dispersions comprises (i) mixing the cellulose-reactive sizing agent with a dispersion system comprising an anionic stabilizer and a cationic compound as defined to obtain an intermediate composition and (ii) homogenizing the intermediate composition in the presence of an aqueous phase as described. Preferably, the components are homogeneously mixed in step (i). The sizing agent used in step (i) may be solid, although it is preferred that it be liquid, as this will facilitate homogeneous mixing. If desired, the intermediate composition can be removed after the mixing step (i) and optionally cooled to solidification to form a substantially anhydrous intermediate sizing composition, allowing easier loading in an economically attractive manner. At the site of contemplated use or elsewhere, the sizing composition may be homogenized in the presence of water by conventional techniques. This process is of particular interest when dispersions of ketene dimers and acid anhydrides are prepared, the latter usually being prepared in a direct bond paper mill using them as a sizing agent in papermaking. The storage condition of a stable, substantially anhydrous composition thus brings desirable economic and technical advantages. Accordingly, the present invention relates to a substantially anhydrous sizing composition comprising a cellulose-reactive sizing agent, a cationic organic compound and an anionic stabilizer, wherein the cationic and anionic compounds, when used in combination, are effective as a dispersing system for the aqueous phase sizing agent, compositions and uses as defined in the claims.

The components present in the composition (composition) of the invention, i.e. the cellulose-reactive sizing agent, the cationic compound and the anionic stabilizer, are preferably as defined above. The present composition is substantially anhydrous, that is, it may contain a small amount of water; the water content may be from 0 to 10% by weight, preferably with a content of less than 5% by weight and preferably less than 2%. Most preferably, it contains no water. The composition preferably comprises cellulose-reactive sizing agent in a predominant amount by weight, i.e. at least 50% by weight, and preferably the composition has a sizing content ranging from 80 to 99.9% by weight, and preferably from 90 to 99.7% by weight. The cationic compound, preferably the surfactant, and the anionic stabilizer may be present in the sizing compositions in defined amounts with respect to dispersions where the percentages are based on the weight of the sizing agent. In the compositions, the anionic stabilizer may be present in an amount of up to 100% by weight, usually from 0.1 to 20% by weight, and preferably from 0.2 to 10% by weight and preferably from 0.3 to 6% by weight, based on the sizing agent and the cationic compound. the surfactant may be present in an amount of up to 100% by weight, usually from 0.1 to 20% by weight, and preferably from 1 to 10% by weight and preferably from 2 to 7% by weight, based on the sizing agent, the total cationic charge The compound and the anionic stabilizer present in the composition are preferably negative and anionic.

The dispersions of the present invention can be used by conventional paper making processes using any type of cellulosic fiber and can be used for surface sizing as well as internal sizing or sizing of paper. The term "paper" as used herein means that it includes not only paper but all types of cellulose-based products in the form of sheets or strips, including, for example, cardboard and paperboard. The pulp contains cellulose fibers, optionally in combination with mineral fillers, and typically the cellulosic fiber content is at least 50% by weight relative to the dry stock. Examples of conventional mineral fillers include kaolin, aluminum silicate, titanium dioxide, gypsum, talc, and natural or synthetic calcium carbonates such as chalk, ground marble, and precipitated calcium carbonate. The present invention also relates to a papermaking process, wherein the aqueous dispersion as defined is used as a surface or paper size. Preferably, the amount of cellulose-reactive sizing agent either added to the pulp containing the cellulose fibers and optionally fillers that will be dewatered when wound to form paper or applied to the paper surface as a surface sizing typically in the sizing press, is from 0.01 to 1% by weight. to the dry weight of the cellulosic fibers and optionally fillers, preferably from 0.05 to 0.5% by weight, the dosage depending mainly on the quality of the pulp or paper to be sized, the size of sizing used and the desired sizing level.

The dispersions of the invention, in particular anionic dispersions, are particularly suitable for sizing pulp of pulp, where the pulp has high cationic requirements and / or contains substantial amounts of lipophile substances, such as pulp prepared from certain stages of wood-containing pulp and recycled, e.g. white water recirculation extensive. Examples of lipophilic substances commonly found in paper pulp include anionic and non-ionic lipophilic substances, such as resin acids, fatty acids, fatty esters, triacylglycerols, and the like. The amount of lipophilic substances may be at least 10 ppm and up to about 100 ppm, usually at least 20 ppm, preferably at least 30 ppm and preferably at least 50 ppm, measured as ppm by DCM extraction using DCM (dichloromethane) by a known method. The cationic requirement may be at least 50, preferably at least 100, and preferably at least 150 bev / liter of paper pulp filtrate. The cationic collection can be measured by a conventional procedure, for example by means of a "Miitek Particle Chargé Detector" using a pulp filtrate obtained from a raw pulp filtered through a 1.6 µm filter and with poly (dialyldimethylammonium chloride) as the titration agent.

Furthermore, the present dispersions are particularly suitable in paper making processes where extensive white water recirculates, for example with a high degree of white water shutoff, for example where 0 to 30 tonnes of fresh water per tonne of dry paper produced, usually less than 20, preferably less than 15 and preferably less than 10, and in particular less than 5 tons of fresh water per tonne of paper. The recirculation of the white water in the process preferably takes place by mixing the white water with the cellulosic fibers, preferably in the form of a pulp or suspension, before or after adding the sizing dispersion, thus forming a pulp to be dewatered. Fresh water can be fed to the process at any stage; for example, it may be blended with cellulosic fibers to form a pulp and may be blended with pulp containing cellulosic fibers to dilute it so as to form a pulp to be dewatered before or after mixing the pulp with white water and before or after the addition of the sizing dispersion.

Chemicals that are commonly added to paper pulp, such as retention aids, aluminum compounds, dyes, wet strength resins, optically brighteners, etc. they can of course be used together with the dispersions present. Examples of aluminum compounds include alum, aluminates, and polyaluminium compounds such as polyaluminium chlorides, and sulfates. Examples of suitable retention aids include cationic polymers, anionic inorganic materials in combination with organic polymers such as bentonite in combination with cationic polymers, silica-based soles in combination with cationic polymers or cationic and anionic polymers. A particularly good paper size glue can be obtained when the dispersions of the invention are used in combination with retention aids containing cationic polymers. Suitable cationic polymers include cationic starch, guar gum, acrylate-based polymers and acrylamide-based polymers, polyethyleneimine, dicyandiamide-formaldehyde resins, polyamines, polyamidoamines and poly (dialyldimethylammonium chloride) and combinations thereof. Cationic starch and cationic acrylamide-based polymers are preferably used, either alone or in combination with each other or with other materials. In a preferred embodiment of the invention, dispersions are used in combination with a retention system comprising at least one cationic polymer and an anionic silica particle. Said dispersions may be added before, between, after or simultaneously with the addition of the cationic polymer or polymers. It is also possible to pre-mix the size dispersion with a retention aid, i.e., a cationic polymer such as a cationic starch or a cationic polymer based on acrylamide or anionic silica-based material, before introducing the thus obtained mixture into the paper by introducing a size dispersion containing the cationic compound. , in contact with the silica-based ionic material, for example as defined above.

The invention will be further illustrated by the following non-limiting examples. Parts and% refer to parts and percentages by weight unless otherwise stated.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

The anionic alkyl ketene dimer (AKD) dispersions of the invention were prepared by mixing di (hydrogenated tallow dimethyl ammonium chloride, a cationic surfactant commercially available under the tradename Querton 442, Akzo Nobel, with molten AKD at 70 ° C) by passing the mixture through a homogenizer in the presence of an aqueous solution. The pH of the dispersion was adjusted to about 5 by the addition of acid The anionic stabilizer used in this example was an fatty amide modified anionic carboxymethylcellulose (FACMC) containing a hydrophobic substituent derived from N-hydrogenated tallow-1,3-diaminopropane prepared according to FACMC had a degree of hydrophobic substitution of 0.1 The dispersion contained AKDs with an average particle size of about 1 µm that were anionically charged, as evidenced by the negative zeta potential determined by the Zeta-Master S version of PCS. The dispersion No. 1 contained 3% cationic surfactant based on the weight of AKD and 1% anionic stabilizer based on the weight of AKD. Dispersion no. 2 contained 7% cationic surfactant by weight of AKD and 1% anionic stabilizer by weight of AKD.

Example 2

The general procedure of Example 1 was repeated except that condensed sodium naphthalenesulfonate, commercially available under the tradename Orotan (TM) SN, Rohm & Haas Company, and using different proportions of compounds in dispersions were used as the anionic stabilizer. Dispersion no. 3 obtained in this example had an AKD content of 30% and contained 6% anionic stabilizer based on the weight of AKD and 4% cationic surfactant based on the weight of AKD. The dispersion contained AKD particles with an average particle size of about 1 μπι, which were anionically charged, as above.

Example 3

The stability of the anionic dispersions of Examples 1 and 2 was tested as follows:

The dispersion was diluted with water to give a dispersion containing 40 ppm AKD. In some tests, 10 ppm of stearic acid was added to increase the content of liophilic substances and cationic requirements. The diluted dispersion was poured into a vessel equipped with a turbidity meter, loop, circulation means and heating and cooling means. The loaded volume of the diluted dispersion was circulated in the loop while turbidity was automatically recorded and the dispersion was subjected to a heating and cooling cycle for a period of 45 minutes. The dispersion temperature was raised from 20 ° C to 62 ° C and then lowered again to 20 ° C. Turbidity is influenced by particle size and the difference in turbidity of the dispersion before and after the temperature cycle is a measurement of the ability of the dispersed particles to resist agglomeration growth and thus measurement of the stability of the dispersion. The turbidity difference (..T) is calculated as follows:

SK 285211 Β6

ΔΤ = (final haze / initial haze) x 100

The higher the ΔΤ, the better the stability.

Two standard dispersions were also tested for comparative purposes:

Ref. 1 is an anionic dispersion AKD comprising a dispersion system comprising sodium lignosulfonate and a cationic starch, wherein the lignosulfonate is present in an ionic excess.

Ref. 2 is an AKD cationic dispersion also containing sodium lignosulfonate and cationic starch, but wherein the cationic starch is present in an ionic excess.

Table 1 shows the results obtained.

Table 1

Dispersion no. Stearic acid (ppm) ΔΤ 1 - 53 1 10 40 2 - 79 2 10 66 3 - 72 3 10 55 Ref. 1 - 45 Ref. 1 10 32 Ref. 2 - 35 Ref. 2 10 6

As shown in Table 1, the hodnoty values of the dispersions of the present invention were significantly higher than those of the standard dispersions and accordingly indicate an improved dilution stability.

Example 4

The efficiency of the size dispersion according to Example 3 was evaluated in this example. Paper sheets were prepared according to the standard SCAN-C23X method for laboratory scale. The pulp used contained 80% bleached birch / pine sulfate (60:40) and 20% chalk, to which 0.3 g / l Na ₂ SO ₄ .10H ₂ O was added. The consistency of the pulp was 0.5% and pH 8, 0th The dispersions were used in conjunction with the commercial retention and drainage system, Compozil ™, containing cationic starch and anionic aluminum modified silica sol, which were added to the pulp separately; cationic starch was added in an amount of 8 kg / tonne relative to the dry stock, and the silica sol was added in an amount of 0.8 kg / tonne, calculated as SiO ₂ based on the dry stock.

The Cobb values, measured according to TAPPI standard T 441 OS-63, obtained during testing are shown in Table 2. The dosage of AKD refers to dry stock.

Table 2

Dispersion no. Dose AKD (kg / t) "Cobb 60" (g / m ² ) 1 0.45 54 1 0, 60 27 Ref. 1 0.45 80 Ref. 1 0, 60 30 Ref. 2 0.45 68 Ref. 2 0, 60 31

Table 2 demonstrates the improved sizing of the paper obtained with the sizing dispersion of the invention.

Example 5

The sizing efficiency was evaluated according to the procedure of Example 4 except that the pulp contained precipitated calcium carbonate as a filler instead of chalk, and the cationic starch dose was 12 kg / ton relative to the dry stock. In some tests, stearic acid (10 ppm) was added to the pulp to increase the cation requirement and the lipophilic substance content of the pulp. The results are shown in Table 3.

Table 3

Disp. no. Dose AKD Stearic acid Cobb 60 (Kg / t) (Ppm) (g / m ² ) 1 0.45 32 1 0, 60 - 28 1 0.75 - 26 1 0.45 10 62 1 0, 60 10 36 1 0.75 10 27 Ref. 1 0.45 - 50 Ref. 1 0, 60 - 32 Ref. 1 0.75 - 30 Ref. 1 0.45 10 103 Ref. 1 0.60 10 76 Ref. 1 0.75 10 35

As can be seen from Table 3, dispersion no. 1 according to the invention generally provided much better sizing than the dispersion Ref. 1 used for comparison and a significantly better sizing effect was obtained when the pulp had a substantial amount of lipophilic substances.

Example 6

An anhydrous sizing composition of the invention was prepared by dry blending 93 parts of AKD pellets with 3 parts of the cationic surfactant of Example 1 and 4 parts of the anionic stabilizer of Example 2. This dry mixture was later added to hot water and the thus obtained aqueous mixture was heated to 80 ° C, pumped with a high shear pump and then cooled to room temperature. The anionic dispersion obtained, dispersion no. 4, had an AKD content of 20% and an average particle size of about 1 µm. The sizing efficiency was evaluated as in Example 4 except that the addition of cationic starch was 12 kg / tonne relative to the dry stock. The results are shown in Table 4.

Table 4

Dispersion no. Dose AKD (kg / t) "Cobb 60" (g / m ² ) 4 0, 30 58 4 0.40 30 Ref. 1 0.30 84 Ref. 1 0.40 65 Ref. 2 0.30 66 Ref. 2 0.40 40

Table 4 illustrates the improvement in the sizing of the paper obtained with the sizing dispersion of the invention.

Example 7

The AKD dispersion of the invention with a dispersion system comprising a cationic surfactant and an anionic stabilizer in the form of an inorganic microparticle material was evaluated in this test series.

The dispersion was prepared by premixing at 75 ° C 0.2 g of a cocoamine commercially available under the trade name Armeen C ™, which is a mixture of amines of formula RNH ₂ , where R is a C 12 -C 18 hydrocarbon, and 1.0 g, calculated as SiO ₂ , an aqueous aluminum modified silica sol of the type described in US Patent No. 5,368,833, and then adding 25 g of AKD and acid to adjust the pH to 4.0. The aqueous mixture was homogenized using Ultra Turax and then cooled. Dispersion obtained, dispersion no. 5, had an AKD content of 25% by weight and contained a dispersant system which was anionic in nature.

The sizing efficiency of the dispersion was evaluated by the procedure of Example 4 using a similar pulp at pH 8.1 and using a standard AKD Ref 2 dispersion for comparison. The results are shown in Table 5, where the dose of AKD is based on dry stock.

Table 5

Dispersion no. Dose AKD (kg / t) "Cobb 60" (g / m ² ) 5 0.3 58 5 0.5 30 5 0.6 28 Ref. 2 0.3 73 Ref. 2 0.5 33 Ref. 2 0.6 30

Example 8

The AKD dispersion of the invention was prepared and evaluated in a similar manner to Example 7 except that the anionic stabilizer used in this example was the melamine sulfonic acid sol prepared as described in the international patent application WO 96/34027. Dispersion no. 6 was prepared from 0.4 g of cocoamine, 2 g of melamine-suifonic acid, 30 g of AKD and water to 100 g. The results of the sizing tests are shown in Table 6, where the dose of AKD is based on the dry stock.

Table 6

Dispersion no. Dose AKD (kg / t) "Cobb 60" (g / m ² )

6 0.4 39 6 0.5 28 6 0.6 22 Ref. 2 0.4 1 50 Ref. 2 0.5 35 Ref. 2 0.6 25

Example 9

The ease of manufacture of the dispersions according to the invention was evaluated by preparing anionic AKD dispersions having different AKD contents. The dispersions according to the invention were prepared by homogenizing a 0.8 wt. di (hydrogenated tallow dimethyl ammonium chloride, 1.6 wt.% condensed sodium naphthalenesulfonate, 77.6 wt.% water and 20 wt.% AKD for a set time using an Ultra Turrax mixer at 1500 rpm and then cooling the dispersion thus obtained for 2 hours. Similar dispersions were prepared in the same manner with different values of AKD content and dispersions with AKD contents of 10, 20, 30 and 40 wt% were obtained.

Standard AKD dispersions were prepared for comparison purposes in the same manner and under the same conditions by homogenizing the 1.0 wt. % cationic starch, 0.25 wt. % sodium lignosulfate, 89 wt. % water and 10 wt. AKD. Similar dispersions were prepared with different AKD contents to obtain standard dispersions with AKD contents of 10, 20, 30 and 40 wt. Dispersions are labeled Ref. 3, followed by the AKD content in wt.

Particle size and viscosity were determined by conventional procedures.

Table 7 shows the results obtained.

Table 7

AKD dispersion no. Particle size (gm) Viscosity (cps) Inv. -10% 2.98 10 Inv. -20% 3.12 20 Inv. -30% 3.50 20 Inv. -40% 3.50 25 Ref.3-10% 4.31 15 Ref.3 -20% 4.52 20 Ref.3 -30% 5.20 25 Ref.3 -40% 5.57 40

Table 7 shows that the dispersions of the invention were easier to process for production; a lower viscosity was obtained at the appropriate AKD content and a smaller particle size was obtained using the same amount of energy to treat the free surfaces. Thus, compared to standard dispersions, less energy and lower shear forces are required according to the invention to produce dispersions of the same particle size. Further, increasing the stirrer speed to 25,000 rpm suitably reduces the particle size of the dispersion of the invention, which is in the range of 1 to 2 µm.

PATENT CLAIMS

Claims (21)

An aqueous sizing agent dispersion comprising a cellulose-reactive sizing agent and a dispersing system comprising a low molecular weight cationic organic compound having a molecular weight of less than 10,000 and an anionic stabilizer which is an anionic polyelectrolyte. Aqueous dispersion according to claim 1, characterized in that the cationic organic compound is present in an amount of from 0.1 to 20% by weight with respect to the sizing agent and the anionic stabilizer is present in an amount of from 0.1 to 20% by weight with respect to the sizing means. Aqueous dispersion according to claim 1 or 2, characterized in that the cationic organic compound is a cationic surfactant. The aqueous dispersion according to claim 3, wherein the cationic surfactant has a molecular weight of from 200 to 800. 5. The aqueous dispersion according to claim 3, wherein the cationic surfactant is selected from primary, secondary, tertiary and quaternary ammonium compounds containing at least one hydrocarbon group having from 9 to 30 carbon atoms. 6. The aqueous dispersion according to claim 3, 4 or 5, characterized in CA uj in that the cationic surfactant is selected from dioctyldimethylammonium chloride, didecyldimethylammonium chloride, dicocodimethylammonium chloride, cocobenzyldimethylammonium, coco (fractionated) benzyldimetylamóniuinchlorid, oktadecyltrimetylamóniumchlorid, dieicosyl, dihexadecyl dimethylammonium chloride, di (hydrogenated tallow) dimethylammonium chloride, di (hydrogenated tallow) benzylammonium chloride, (hydrogenated tallowbenzyldimethylammonium chloride, dioleyldimethylammonium chloride and di (ethylenehexadecanecarboxylate) dimethylammonium chloride and N-octadecyl chloride-N-octadecyl chloride-N-octadecyl chloride-N-octadecyl chloride). Aqueous dispersion according to claim 1 or 2, characterized in that the cationic surfactant compound is a cationic polyelectrolyte. Aqueous dispersion according to any one of the preceding claims, characterized in that the anionic stabilizer is an organic compound. The aqueous dispersion according to any one of claims 1 to 7, characterized in that the anionic stabilizer is an inorganic silica-based material. Aqueous dispersion according to claim 1, 2 or 8, characterized in that the anionic stabilizer is selected from the group consisting of anionic polyurethanes, condensed naphthalenesulfonates, polymeric anionic compounds based on polysaccharides, vinyl addition polymers formed from monomers having anionic groups, optionally copolymerized with non-ionic monomers, and anionic organic microparticulate materials. Aqueous dispersion according to any one of the preceding claims, characterized in that the dispersion is anionic. Aqueous dispersion according to any one of the preceding claims, characterized in that the sizing agent is a ketene dimer or an acid anhydride. 13. A method of preparing an aqueous dispersion of a cellulose-reactive gelling agent, comprising homogenizing the cellulose-reactive glue agent in the presence of an aqueous phase and a dispersion system comprising a low molecular weight cationic organic compound having a molecular weight of less than 10,000 and an anionic stabilizer. is an anionic polyelectrolyte. 14. The process of claim 13, wherein the cationic organic compound is derived from an electroneutral organic polymer with basic amino groups or a basic amine, wherein the corresponding cationic ammonium moiety is formed in the process. 15. The method of claim 13, comprising providing an anhydrous composition comprising a cellulose-reactive sizing agent, a cationic organic compound and an anionic stabilizer, and homogenizing the composition in the presence of an aqueous phase. Use of the aqueous dispersion according to any one of claims 1 to 12 as a paper size glue or surface size glue in the manufacture of paper. A method of making paper by adding an aqueous dispersion of the sizing agent to a pulp containing cellulosic fibers and optionally fillers by dewatering the spool to obtain paper and white water, characterized in that the dispersion is an aqueous dispersion according to any one of claims 1 to 12. 18. The method of claim 17, wherein the white water is recirculated in the process or fresh water is fed to produce pulp containing cellulosic fibers to be dewatered, and the amount of fresh water delivered is less than 30 tonnes per water. ton of paper produced. A composition comprising a cellulose-reactive sizing agent, a low molecular weight cationic organic compound having a molecular weight of less than 10,000, and an anionic stabilizer which is an anionic polyelectrolyte, wherein the water content of the composition is 0 to 10% by weight. The composition of claim 19, wherein the cationic organic compound is present in an amount of from 0.1 to 20% by weight relative to the cellulose-reactive sizing agent and the anionic stabilizer is present in an amount of from 0.1 to 20%. by weight relative to the cellulose-reactive sizing agent, the total charge of the cationic compound and the anionic stabilizer is negative. Use of a composition according to claim 19 or 20 for preparing an aqueous dispersion of a cellulose-reactive sizing agent according to any one of claims 1 to 12.