KR20000070621A - Aqueous dispersions of hydrophobic material - Google Patents

Abstract

The invention relates to an aqueous dispersion containing a dispersant and a disperse phase containing a hydrophobic material, the dispersant comprising an anionic compound having a molecular weight less than 50,000 and being selected from carbon-containing compounds and silicon-containing compounds, and a cationic organic compound having a molecular weight less than 50,000. The invention further relates to the preparation and use of the dispersion in the production of paper. The invention also relates to a substantially water-free composition containing a hydrophobic material, an anionic compound having a molecular weight less than 50,000 and being selected from carbon-containing compounds and silicon-containing compounds, and a cationic organic compound having a molecular weight less than 50,000, as well as its use in the preparation of an aqueous dispersion.

Description

Hydrophobic Aqueous Dispersion {AQUEOUS DISPERSIONS OF HYDROPHOBIC MATERIAL}

Aqueous dispersions of hydrophobic materials are well known and used in numerous applications. For example, in papermaking, aqueous dispersions of hydrophobic materials are used as sizing agents to impart some resistance to penetration and wetting by aqueous liquids on paper and cardboard. Examples of hydrophobic materials widely used for sizing include cellulose reactive sizing agents such as alkyl ketene dimers and substituted succinic anhydrides and non-cellulose reactive sizing agents such as rosin-based and resin-based sizing agents.

Dispersions of hydrophobic materials include droplets or finely divided particles in which the aqueous phase and the hydrophobic material are dispersed. This dispersion is prepared by homogenizing the hydrophobic insoluble material in the aqueous phase using high shear forces and high temperatures. Traditionally used dispersants include anionic, amphoteric and cationic high molecular weight polymers such as lignosulfates, starches, polyamines, polyamideamines and vinyl addition polymers. These polymers may be used alone or in combination with other compounds to form a dispersant system. Depending on the total charge of the dispersant system components, the sizing dispersion will be anionic or cationic.

Dispersions of hydrophobic materials show fairly poor stability and high viscosity even at relatively low solids content, making it difficult to handle the dispersion during storage and use. Another drawback is that the product must be supplied as a low concentration dispersion, which further increases the delivery cost of the active hydrophobic material.

It is therefore an object of the present invention to provide hydrophobic aqueous products with improved stability and viscosity. It is another object of the present invention to provide an improved aqueous dispersion of sizing agents, in particular cellulose reactive sizing agents.

The present invention relates to dispersions having a dispersant system containing a hydrophobic material, an aqueous dispersion, in particular two oppositely charged compounds, and methods of making and using the same.

It has been found that, according to the invention, improved stability and viscosity can be obtained by using a hydrophobic aqueous product in which the hydrophobic material is dispersed in the aqueous phase by means of a dispersant comprising two oppositely charged compounds having a relatively low molecular weight. . In particular the invention relates to an aqueous dispersion comprising a dispersed phase comprising a hydrophobic material and a dispersant comprising an anionic compound selected from organic compounds and silicone containing compounds and a cationic organic compound having a molecular weight of less than 50,000. The present invention therefore relates to aqueous dispersions, methods for their preparation and uses.

The present invention makes it possible to provide improved storage stability, higher solids content or lower viscosity to the hydrophobic dispersion. In addition, it has been found that the dispersion phase is more stable when using this dispersion in applications where high dilution of the initial high concentration dispersion is involved, resulting in improved dilution stability. Examples of applications where high dilution is required are paper wet end-conditions and paper stock solutions or internal sizing in which hydrophobic material dispersions are added to an aqueous suspension containing cellulose fibers and fillers. Improved dilution stability results in less agglomeration of hydrophobic sizing agent particles or droplets, resulting in smaller amounts of large aggregates with lower sizing efficiency, less precipitation of hydrophobic sizing agents on the paper machine, and less wire contamination, thus reducing the need for paper machine maintenance. It means Additional advantages observed with the use of this dispersion include improved stability in the presence of disturbing materials such as impurities of debris derived from impure pulp or recycled fibers. The dispersions of the invention are therefore particularly useful in processes in which the white water is recycled excessively and the cellulose suspension contains a significant amount of residue. In addition, the dispersions of the present invention allow for improved sizing efficiency compared to conventional sizing agent dispersions when similar sizing agents are administered, and to achieve similar sizing effects with smaller amounts of sizing agents. The use of a smaller amount of sizing agent for the sizing effect in the baseline further reduces the risk of accumulation of non-adsorbed hydrophobic sizing agent during recycle of white water in the process, thereby reducing the risk of precipitation and aggregation of hydrophobic material on the paper machine. Thus, the present invention provides significant advantages in economic and technical aspects.

The hydrophobic material present in the dispersion is insoluble in water. Examples of hydrophobic materials include compounds that are useful as sizing agents in papermaking processes and can be derived from natural and synthetic sources, such as cellulose-reactive hydrophobic materials and non-cellulose-reactive hydrophobic materials. In a preferred embodiment the hydrophobic material has a melting point below 100 ° C., in particular below 75 ° C.

In a preferred embodiment of the present invention the hydrophobic material is a cellulose-reactive sizing agent selectable from cellulose-reactive sizing agents known in the art. In particular, the sizing agent is selected from hydrophobic ketene dimers, ketene polypolymers, acid anhydrides, organic isocyanates, carbamoyl chlorides or mixtures thereof, with ketene dimers and acid anhydrides, even more ketene dimers, preferred. Suitable ketene dimers are compounds of formula 1 wherein R ¹ and R ² are saturated or unsaturated, especially saturated hydrocarbons and hydrocarbons have 8 to 36 carbon atoms, in particular straight chains having 12 to 20 carbon atoms such as hexadecyl and octadecyl groups Or a branched alkyl group. Suitable acid anhydrides have the formula (2) and R ³ and R ⁴ are the same or different and are saturated or unsaturated hydrocarbons containing 8 to 30 carbon atoms or R ³ and R ⁴ together with the -COC- moiety form a pentagonal or hexagonal ring. And hydrocarbons containing up to 30 carbon atoms. Examples of acid anhydrides used commercially are alkyl and alkenyl succinic anhydrides, in particular isooctadecenyl succinic anhydride.

Suitable ketene dimers, acid anhydrides and organic isocyanates include compounds disclosed in US Pat. No. 4,522,686. Examples of suitable carbamoyl chlorides are disclosed in US Pat. No. 3,887,427.

In another embodiment of the present invention the hydrophobic material is a non-cellulose-reactive hydrophobic material selectable from non-cellulose-reactive sizing agents known in the art. Non-cellulose-reactive sizing agents are rosin such as rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, formaldehyde treated rosin, esterified rosin, reinforced rosin or rosin compound so treated Basic hydrophobic material; Fatty acids and their derivatives, including amides such as fatty acid esters and bis-steaamides; Resins and derivatives thereof such as hydrocarbon resins, resin acids, resin acid esters and amides; And waxes such as crude and purified paraffin waxes, synthetic waxes, natural waxes.

Dispersions according to the invention include dispersants or systems of dispersants comprising anionic compounds and cationic compounds having low molecular weight (LMW). LMW compounds are bound by electrostatic attraction to represent coacervate dispersions. LMW compounds are effective dispersants for hydrophobic materials, although when used in combination are not as effective dispersants as when anionic and cationic compounds are used alone. In a preferred embodiment at least one of the anionic and cationic compounds is a polyvalent electrolyte. A "polyelectrolyte" is a compound having two or more charged (anionic / cationic) groups that act as polyvalent electrolytes through chemical nonionic attraction.

The anionic compounds of the dispersant include one or more anionic groups which are the same or different and have an anionic compound having one anionic group and an anionic compound (polyelectrolyte) having two or more anionic groups. Anionic polyvalent electrolytes may include one or more cationic groups having a total anionic charge. Examples of suitable anionic groups include sulfonic acid, phosphoric and phosphonic acid groups, sulfates and carboxyl groups which may be present as free acids or water soluble ammonium salts or alkali metal salts (generally sodium) such as carboxylic acids and sodium sulfonic acid. The anionic polyvalent electrolyte may have an anion substitution degree (DS _A ) of 0.01 to 1.4, in particular 0.1 to 1.2, even 0.2 to 1.0.

Anionic compounds of the dispersant are derived from natural or synthetic sources and are water soluble or water dispersible. In a preferred embodiment, the anionic compound is a carbon atom containing organic compound. Suitable anionic compounds include alkyl, aryl and alkylaryl sulfates and ether sulfates; Alkyl, aryl and alkylaryl carboxylates; Alkyl, aryl and alkylaryl sulfonates; Alkyl, aryl and alkylaryl phosphates and etherphosphates; And anionic surfactants such as dialkyl sulfosuccinate, wherein the alkyl group has 1 to 18 carbon atoms, the aryl group has 6 to 12 carbon atoms and the alkylaryl group has 7 to 30 carbon atoms. Examples of suitable anionic surfactants include sodium lauryl sulfate, sodium lauryl sulfonate and sodium dodecylbenzenesulfonate. Another example of a suitable anionic compound is an anionic polyelectrolyte such as an anionic organic LMW polymer (decomposed) such as phosphorylated, sulfonated and carboxylated polysaccharides (starch, guar gum, cellulose), in particular cellulose derivatives, even more carboxymethyl cellulose Derived from and condensation products such as naphthalene sulfonates condensed with anionic polyurethane, acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, vinylsulfonic acid, sulfonated styrene and hydroxyalkyl acrylates (methacrylates) Vinyl addition polymers formed from monomers having anionic groups, such as phosphates, and copolymerizable with non-ionic monomers such as acrylamide, alkyl acrylates, styrene and acrylonitrile and derivatives such as vinyl esters. Anionic compounds are also silica based in silicasol form with silicates and various forms of condensed or polymerized silicic acids such as oligomeric silicic acid, polysilicates, polysilicates, polyaluminum silicates, polysilicate microgels, polyaluminum silicate microgels and negative hydroxyl groups. It may also be selected from LMW inorganic compounds containing silicon atoms as materials.

Cationic compounds of the dispersant include one or more cationic groups which are the same or different and have one cationic group and a cationic compound (cationic polyelectrolyte) having two or more cationic groups. The cationic polyelectrolyte may comprise one or more anionic groups having a total positive charge. Examples of suitable cationic groups include acid addition salts and quaternary ammonium groups of sulfonium groups, phosphonium groups, primary, secondary and tertiary amines or amino groups, with nitrogen being quaternized with methyl chloride, dimethyl sulfate or benzyl chloride, in particular amines Acid addition salts and quaternary ammonium groups of the / amino group are preferred. Cationic polyelectrolytes have a cation substitution degree (DS _C ) of 0.01 to 1.0, in particular 0.1 to 0.8, even 0.2 to 0.6.

Cationic compounds of the dispersant may be derived from synthetic or natural sources and are water soluble or water dispersible. Organic compounds are preferred as cationic compounds. Examples of suitable cationic compounds include cationic surfactants, e.g., R ₄ N ⁺ X ^- comprises a compound, each R is (ⅰ) hydrogen; (Ii) hydrocarbons, in particular containing 1 to 30 carbon atoms, even more preferably containing 1 to 22 carbon atoms; (Iii) an aliphatic alkyl group having up to 30 carbon atoms, in particular 4 to 22 carbon atoms and containing one or more heteroatoms such as oxygen or nitrogen or heteroatomic containing groups such as carbonyl and acyloxy groups; At least one of said R, in particular at least three, even more all have at least seven, in particular at least nine, even more than twelve carbon atoms; X ⁻ is an anionic group present in an anionic compound of a halide or dispersant such as chlorine ion, for example the surfactant is a protonated amine of the general formula R ₃ N and R and N are as defined above. Examples of suitable surfactants are dioctyldimethylammonium, didecyldimethylammonium chloride, dicodimethylammonium chloride, cocobenzyldimethylammonium, coco (separated) benzyldimethylammonium chloride, octadecyltrimethylammonium chloride, dioctadecyldimethylchloride Ammonium, dihexadecyldimethylammonium chloride, di (hydrogenated resin) dimethylammonium chloride, di (hydrogenated resin) benzylmethylammonium chloride, (hydrogenated resin) benzyldimethylammonium chloride, dioleyldimethylammonium chloride and di (ethylene hexa Decancarboxylate) dimethyl ammonium chloride. Particularly preferred cationic surfactants include alkyl groups having 9 to 30 carbon atoms and even more preferred quaternary ammonium compounds. Still other cationic surfactants include quaternary di- and poly-ammonium compounds containing at least one aliphatic alkyl group having 9 to 30, in particular 12 to 22, carbon atoms. Surfactants of this kind include N-octadecyl-N-dimethyl-N'-trimethyl-propylene-ammonium chloride. Another example of a cationic compound is a cationic organic LMW polymer derived from polysaccharides such as starch and guar gum, a cationic condensation product such as polyurethane, a polyamideamine such as polyamideamine epichlorohydrin, dimethylamine-epichlorohi Present as polyamines, acid addition salts or quaternary ammonium salts, such as phthalic copolymers, dimethylamine-ethylenediamine-epichlorohydrin copolymers, ammonia-ethylene dichloride copolymers, acrylamide, alkyl acrylates, styrene and acrylonitrile Homo of diallyldimethylammonium chloride, dialkylaminoalkyl acrylates, methacrylates and acrylamides (such as dimethylaminoethyl acrylate and methacrylate) copolymerized with non-ionic monomers and derivative vinyl esters of such monomers Cationic groups such as polymers and copolymers Cationic polyelectrolytes such as vinyl addition polymers formed from monomers having.

The anionic LMW compounds and cationic LMW compounds used in the present invention have a molecular weight (MW) of less than 50,000, in particular less than 30,000 and even less than 20,000. There is an additional advantage when the molecular weight of the anionic or cationic compounds of the dispersant is lower, in particular less than 10,000. Usually anionic and cationic compounds have a MW of at least 200, in particular at least 500. Usually anionic and cationic surfactants have less MW than anionic and cationic polyelectrolytes and preferred surfactants have a MW of 200 to 800. If one of the dispersants is a surfactant, the other compound must be a polyelectrolyte having the MW defined above.

Preferred dispersions of the invention include (i) dispersants comprising a cationic surfactant and an anionic polyvalent electrolyte and having a total anionic charge; (Ii) a dispersant comprising a cationic polyelectrolyte and an anionic polyelectrolyte and having a total anionic charge; (Iii) a dispersant comprising an anionic surfactant and a cationic polyvalent electrolyte and having a total cationic charge; (Iii) a dispersant selected from dispersants comprising anionic polyelectrolytes and cationic polyelectrolytes and having a total cationic charge; Anionic and cationic surfactants, anionic and cationic polyelectrolytes and molecular weights are as defined above.

Anionic and cationic compounds of the dispersant may be present in the dispersion in varying amounts depending on the molecular weight of the compound, the degree of ion substitution of the compound, ie the charge density, the total charge of the dispersion, and the hydrophobic materials used. Both the anionic compound and the cationic compound may be present in amounts of up to 100% by weight, in particular 0.1 to 20% by weight and even 1 to 10% by weight relative to the hydrophobic material.

The dispersions according to the invention can be prepared with high solids content and show very good storage stability and low viscosity. The present invention provides improved storage stability or high solids content in hydrophobic dispersions. Particularly preferred dispersions in this respect include cellulose-reactive sizing agent dispersions, dispersant containing dispersions having a total negative charge. The cellulose-reactive sizing agent dispersion according to the invention may have a sizing agent content of 0.1 to 50% by weight, in particular 20% by weight or more. The ketene dimer sizing agent-containing dispersion according to the invention may have a ketene dimer content of 5 to 50% by weight, in particular 10 to 35% by weight. The acid anhydride containing dispersions or emulsions according to the invention may have an acid anhydride content of 0.1 to 30% by weight, in particular 1 to 20% by weight. The non-cellulose reactive sizing agent dispersion may have a sizing agent content of 5 to 50% by weight, in particular 10 to 35% by weight.

The dispersion according to the invention can be prepared by mixing the hydrophobic material and the dispersant system and the aqueous phase at a temperature at which the hydrophobic material becomes a liquid and homogenizing the resulting mixture under pressure. The aqueous emulsion obtained contains droplets of hydrophobic material having a diameter size of 0.1 to 3.5 μm, after which it is cooled. In addition to the components mentioned above, other substances such as nonionic dispersants, stabilizers, extenders such as urea and urea derivatives and preservatives may be included. The positive and negative charges of the compounds of the dispersant may be formed in situ by contacting the compounds with each other, mixing the compounds with the aqueous phase, or lowering the pH of the aqueous phase. For example, the loss of hydrogen from an acid forms an anionic charge and the addition of a proton with a basic amine or amino group can be cationic by withdrawing hydrogen. It is therefore possible to start with an electroless compound in preparing dispersions. For example, organic compounds having a basic amino or amine of the general formula R ₃ N can be used and R ₄ N ⁺ X ⁻ is formed in the preparation process and R, N and X are as defined above.

The components of the present dispersions can be easily homogenized in the presence of an aqueous phase, in particular the LMW compound of the dispersant is used in combination with hydrophobic materials having melting points below 100 ° C., in particular below 75 ° C. Simplified equipment can be used because less energy and shear force are required compared to conventional dispersion manufacturing processes. The process for preparing dispersions therefore comprises (i) mixing the hydrophobic material with the cationic and anionic compounds of the dispersant to form an intermediate composition, and (ii) homogenizing the intermediate product in the presence of the aqueous phase. The hydrophobic material used in step (iii) may be a solid but a liquid is preferred to simplify homogeneous mixing. If necessary, after the mixing step (iii), the intermediate composition is removed and cooled to form an anhydrous intermediate composition containing a dispersant and a hydrophobic material which allows for solidification and simplified shipment in an economical manner. The hydrophobic intermediate composition, such as in place of use, may be homogenized in the presence of water at elevated temperatures to render the intermediate composition liquid. This method is beneficial in the preparation of ketene dimer and acid anhydride dispersions, the latter being produced in paper mills for use as sizing agents in paper manufacture. Providing a storage stable anhydrous composition provides significant economic and technical advantages. The present invention therefore relates to anhydrous concentrate compositions comprising anionic LMW compounds selected from hydrophobic materials, carbon containing compounds and silicon containing compounds, and cationic organic LMW compounds. Anionic and cationic compounds here are effective as dispersant systems for dispersing hydrophobic materials in the aqueous phase when used in combination.

The components present in the concentrate composition according to the invention, ie the hydrophobic materials and the cation and anionic compounds, are as defined above. The composition is anhydrous with water content of 0 to 10% by weight, in particular less than 5% by weight, even less than 2% by weight and most preferably free of water. The composition has a hydrophobic content of at least 50% by weight, in particular 80 to 99.9% by weight and even 90 to 99.7% by weight. Anionic and cationic compounds may be present in the composition in amounts defined above for the dispersion and the ratio is based on the hydrophobic material. The anionic compound and the cationic compound may therefore be present in the composition in an amount of up to 100% by weight, in particular 0.1 to 20% by weight and even 1 to 10% by weight relative to the hydrophobic material.

The dispersion of the present invention can be used as a sizing agent in a conventional manner in the manufacture of paper using cellulose fibers and can be used for surface sizing and for internal or stock solution sizing. "Paper" includes paper and web-like cellulose based products, including boards and cardboard. The stock solution contains cellulose fibers and mineral fillers and the content of cellulose is 50% by weight or more based on the dry stock solution. Examples of mineral fillers include natural and synthetic calcium carbonates such as kaolin, china clay, titanium dioxide, gypsum, talc and chalk, ground marble and precipitated calcium carbonate. The amount of hydrophobic sizing agent added to the stock solution is from 0.01 to 5% by weight, in particular from 0.05 to 1.0% by weight, relative to the dry weight of cellulose fibers and fillers, and the dosage depends on the quality of the pulp or paper to be sized, the sizing agent used and the degree of sizing required. Depends

In a preferred embodiment, the dispersion is a stock solution of cellulose pulp when the stock solution has a high cation demand or comprises a significant amount of lipophilic material, such as when the stock is prepared from wood-containing and recycled pulp with excessive recycle of white water. Used for sizing Particularly preferred dispersions for such applications include cellulose-reactive sizing agent dispersions and dispersant containing dispersions having a total anionic charge. Cation demand is above 50, especially above 100, even above 150 Liter of filtrate. The cation demand can be measured by means of a Mutek Particle Charge Detector using poly (diallyldimethylammonium chloride) as a titrant and a stock filtrate obtained from the stock solution filtered through a 1.6 μm filter. The amount of lipophilic extract as measured in DCM ppm by means of extraction with DCM (dichloromethane) in a known manner is at least 10 ppm, in particular at least 20 ppm, even more at least 30 ppm, even more at least 50 ppm. In addition, the dispersion of the present invention is a papermaking process in which white water is recycled excessively, i. Used in the process used. The recycling of white water in the process is carried out by mixing the white water with cellulose fibers in the form of a stock solution or suspension before or after the addition of the sizing agent to form the stock solution to be dehydrated. Fresh water may be introduced into the process at any stage. For example, water may be mixed with the cellulose fibers to form a stock solution and mixed with the cellulose fiber-containing stock solution to dilute it before or after mixing the stock solution with white water and before or after sizing agent addition.

Chemicals added to the stock solution in papermaking processes such as retention agents, aluminum compounds, dyes, wet strength resins, polishes and the like can be used with the sizing dispersion of the present invention. Non-cellulose-reactive sizing agents are used with aluminum compounds to secure the sizing agents to cellulose fibers. Examples of aluminum compounds include alum, aluminate and polyaluminum compounds (polyaluminum chloride, aluminum polysulfate). Suitable retention agents include silica based sol in combination with cationic polymers, organic polymers, such as bentonite, cationic polymers or cationic and anionic polymers in combination with cationic polymers. Particularly good stock sizing can be achieved when the dispersion of the invention is used in combination with a retention agent comprising a cationic polymer. Suitable cationic polymers include cationic starch, guar gum, acrylate and acrylamide based polymers, polyethyleneamines, dicyandiamide-formaldehydes, polyamines, polyamidoamines, poly (diallyldimethyl ammonium chloride) or combinations thereof. Cationic starch and cationic acrylamide based polymers are preferred, alone or in combination with other materials. In one embodiment of the invention the dispersion is used in combination with a retention system comprising at least one cationic polymer and anionic silica based particles. The dispersion may be added before, after, in the middle, or simultaneously with the addition of the cationic polymer. It is also possible to premix the sizing dispersion with a retainer such as a cationic polymer (cationic starch) or a cationic acrylamide based polymer or an anionic silica based material before introducing the obtained mixture into the stock solution. Thus, a dispersion can be prepared immediately before introduction into the stock solution by contacting a sizing composition containing a cationic compound (particularly a cationic surfactant) with an anionic silica based material.

Example 1

The hydrophobic alkyl ketene dimer (AKD) dispersion according to the present invention is commercially available from Akzo Nobel under the trademark Querton 442, and a cationic surfactant di (hydrogenated resin) dimethylammonium chloride having a MW of 340 is mixed with the melted AKD at 70 ° C. It is prepared by passing through a homogenizer in the presence of an aqueous solution of condensed sodium naphthalene sulfonate with a MW of 6000, commercially available from Rohm & Haas under the trademark Orotan SN, and cooling the dispersion obtained. The pH of the dispersion is adjusted to 5 by addition of acid. Dispersion 1 has an AKD content of 30% and comprises 6% anionic compound and 4% cationic compound by weight of AKD. This dispersion contains cellulose-reactive hydrophobic particles having a mean particle size of about 1 μm negatively charged, as can be seen by the negative zeta potential determined by means of ZetaMaster S Version PCS.

Example 2

The stability of the dispersion of Example 1 is tested as follows: This dispersion is diluted with water to give a dispersion containing 40 ppm of AKD. In the test, 10 ppm of stearic acid is added to assess stability in the presence of lipophilic anionic materials. The diluted dispersion is introduced into a jar equipped with a turbidity measuring device, a loop, circulation means, heating and cooling means. A fixed volume of dilute dispersion is circulated in the loop and the turbidity is recorded and the dispersion is subjected to cooling and heating cycles for a set period of 45 minutes. The temperature of the dispersion is raised from 20 ° C. to 62 ° C. and cooled to 20 ° C. again. Turbidity is affected by particle size, and the difference in turbidity of the dispersion before and after the temperature cycle is the ability of the dispersed particles to withstand growth by aggregation and the stability of the dispersion. Turbidity difference (ΔT) is measured as follows: ΔT = (final turbidity / initial turbidity) × 100. The larger ΔT is, the better the stability is.

Two standard dispersions were tested for comparison purposes. Criteria 1 is an anionic AKD dispersion comprising a dispersant system consisting of sodium lignosulfonate and high molecular weight (HMW) cationic starch (with an excess of anionic lignosulfonate present). Criteria 2 is a cationic AKD dispersion comprising sodium lignosulfonate and HMW cationic starch, but with an excess of cationic starch. Table 1 shows the results obtained.

Dispersion number Stearic acid (ppm) △ T One - 72 One 10 55 Standard 1 - 45 Standard 1 10 32 Standard 2 - 35 Standard 2 10 6

As can be seen from Table 1, ΔT of the dispersion of the present invention is much higher than the standard dispersion and thus shows better dilution stability.

Example 3

Anhydrous concentrate compositions according to the invention are prepared by dry mixing 93 parts by weight of AKD pellets with 3 parts by weight of cationic surfactants and 4 parts by weight of anionic compounds used in Example 1. This dry mixture is then added to hot water and the resulting aqueous mixture is heated to 80 ° C., pumped through a high shear pump and cooled to room temperature. The resulting anionic dispersion 2 had an AKD content of 20% and an average particle size of about 1 μm.

Paper sheets were prepared according to laboratory standard method SCAN-C23X, containing 20% choke with 0.3 g / L Na ₂ SO ₄ · 10H ₂ O and 80:40 bleached birch / pine pine sulfate. Sizing efficiency is assessed using the filing fee. The dispersion is used in conjunction with the retention and dehydration system Compozil, which comprises cationic starch and anionic aluminum modified silica sol, which are added separately to the stock solution, the cationic starch is added in an amount of 12 kg / ton to the dry stock solution and silica The sol was added in an amount of 0.8 kg / ton as calculated as SiO ₂ for the dry stock solution.

Cobb values measured according to TAPPI standard T 441 OS-63 are described in Table 2. The AKD input is based on the dry stock solution.

Dispersion number AKD input amount (㎏ / ton) Cobb 60 (g / ㎡) 2 0.30 58 2 0.40 30 Standard 1 0.30 84 Standard 1 0.40 65 Standard 2 0.30 66 Standard 2 0.40 40

Table 2 shows that the use of the dispersion according to the invention improves the paper sizing effect.

Example 4

The ease of preparation of the dispersions according to the invention is evaluated by preparing anionic dispersions at different AKD contents. The dispersions of the present invention were prepared by mixing the Ultra Turrax mixer with a 0.8% by weight of di (hydrogenated resin) dimethylammonium chloride, 1.6% by weight of condensed sodium naphthalene sulfonate, 77.6% by weight of water, and 20% by weight of AKD mixture. It is prepared by homogenizing at 15000 rpm of use and cooling the obtained dispersion for 2 hours. Similar dispersions are prepared in the same manner with different AKD contents to give dispersions having AKD contents of 10, 20, 30 and 40% by weight. This dispersion is expressed in Inv.-AKD weight percent.

Standard AKD dispersions are prepared by homogenizing 1.0 wt% cationic starch, 0.25 wt% sodium lignosulfate, 89 wt% water and 10 wt% AKD in the same manner and conditions. Similar dispersions are prepared with 10, 20, 30, 40 weight percent AKD content. This dispersion is expressed as reference 3-AKD weight percent.

Particle size and viscosity are evaluated in a conventional manner. Table 3 shows the results.

AKD Dispersion Number Particle size (㎛) Viscosity (cps) Inv. -10% 2.98 10 Inv. -20% 3.12 20 Inv. -30% 3.50 20 Inv. -40% 3.50 25 Criteria 3-10% 4.31 15 Criteria 3-20% 4.52 20 Criteria 3-30% 5.20 25 Criteria 3-40% 5.57 40

Table 3 shows that the dispersion according to the invention is easy to prepare. Lower viscosities are obtained at similar AKD contents and smaller particle sizes are obtained using the same energy to free the surface. Less energy and shear forces are required in the present invention to produce dispersions having the same particle size as standard dispersions. In addition, increasing the stirrer speed to 25000 rpm greatly reduces the particle size so that the dispersion of the present invention can be 1 to 2 μm in size.

Claims (20)

The dispersant comprises a hydrophobic material-containing dispersing phase and a dispersant, characterized in that (a) a molecular weight of less than 50,000 and an anionic compound selected from carbon-containing and silicon-containing compounds and (b) a cationic organic compound having a molecular weight of less than 50,000. Aqueous dispersion made. The dispersion of claim 1 wherein the anionic and cationic compounds have a molecular weight of less than 20,000. The dispersion according to claim 1 or 2, wherein the anionic compound is an organic compound. 4. The dispersion as claimed in claim 1, 2 or 3, wherein the dispersant is anionic and comprises a cationic surfactant and an anionic polyvalent electrolyte. 4. The dispersion as claimed in claim 1, 2 or 3, wherein the dispersant is anionic and comprises a cationic polyelectrolyte and an anionic polyelectrolyte. 4. The dispersion as claimed in claim 1, wherein the dispersant is cationic and comprises anionic surfactant and cationic polyelectrolyte. 4. The dispersion as claimed in claim 1, wherein the dispersant is cationic and comprises an anionic polyelectrolyte and a cationic polyelectrolyte. The dispersion of claim 1, wherein the dispersion has a hydrophobic content of at least 20% by weight. The dispersion of claim 1, wherein the hydrophobic material is a cellulose-reactive sizing agent. 10. The dispersion of claim 9 wherein the sizing agent is a ketene dimer or an acid anhydride. 10. The dispersion of claim 9 wherein the hydrophobic material is a non-cellulose-reactive sizing agent. The dispersion according to claim 8, 9, 10 or 11, characterized in that the hydrophobic material has a melting point of less than 75 ° C. A process for producing an aqueous dispersion by homogenizing a hydrophobic material in the presence of an aqueous phase and a dispersant comprising an anionic compound selected from a carbon-containing compound and a silicon-containing compound and a cationic organic compound having a molecular weight of less than 50,000. The method of claim 13 wherein the anionic compound and the cationic compound have a molecular weight of less than 20,000. The method according to claim 13 or 14, wherein the anionic compound is an organic compound. The aqueous dispersion according to any one of claims 1 to 12, which is used for stock solution or surface sizing in the manufacture of paper. Anhydrous sizing composition comprising a hydrophobic material, an anionic compound selected from carbon-containing and silicon-containing compounds with a molecular weight of less than 50,000, and a cationic organic compound having a molecular weight of less than 50,000. 18. The composition of claim 17, wherein the anionic compound is an organic compound. 19. The composition of claim 17 or 18, wherein the hydrophobic material is a ketene dimer or an acid anhydride. The composition of any one of claims 17, 18 or 19 for use in the preparation of an aqueous dispersion according to any of the preceding claims.