JP3400803B2 - Aqueous dispersion 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

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aqueous dispersions of hydrophobic materials as well as more particularly dispersions having a dispersant system comprising two oppositely charged compounds, their preparation and use.

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

A dispersion of hydrophobic material generally comprises an aqueous layer and finely divided particles or droplets of the hydrophobic material dispersed therein.
Dispersions are usually prepared by homogenizing a hydrophobic, water-insoluble material to an aqueous layer in the presence of a dispersant using high shear and fairly high temperatures. Conventionally used dispersants include anionic, amphoteric and cationic high molecular weight polymers such as lignosulfonates, starches, polyamines, polyamidoamines and vinyl addition polymers. The polymers can be used alone, together or in combination with other compounds to form a dispersant system. Due to the overall charge of the dispersant system components,
The size dispersion can be anionic or cationic.

Dispersions of hydrophobic materials usually exhibit rather poor stability and high viscosities, even at relatively low solids contents, which makes the dispersions difficult to handle, eg in storage and in use. A further disadvantage is that the product has to be supplied as a low-concentration dispersion, which further increases the transportation costs of the active hydrophobic material.

Therefore, it is an object of the present invention to provide a hydrophobic material with improved stability and viscosity properties. Another object of the invention is to provide an improved aqueous dispersion of sizing agents, especially cellulose-reactive sizing agents. Further purposes will emerge after this.

According to the invention, it has been found that improved stability and viscosity properties are obtained with aqueous dispersions of hydrophobic materials, wherein the hydrophobic material comprises two oppositely charged compounds having a relatively low molecular weight. It is dispersed in the aqueous layer by the dispersant.
More specifically, the present invention provides a dispersion layer comprising a dispersant having a hydrophobic material and a molecular weight of less than 50,000 and containing an anionic compound selected from organic compounds and silicon-containing compounds, as well as a molecular weight of less than 50,000. The present invention relates to an aqueous dispersion containing a cationic organic compound having. The invention therefore further relates to the aqueous dispersions defined in the claims, their preparation and use.

The present invention provides improved storage stability, high solids content and / or
Alternatively, it enables the provision of a low viscosity hydrophobic material dispersion.
In addition, the dispersion layer was found to be more stable when initially using the dispersion in applications involving very high dilutions of concentrated dispersions, i.e. the dispersions show improved dilution stability. It was Examples of very high dilution applications include wet end conditions for papermaking and raw or internal sizing involving the addition of a dispersion of hydrophobic material to an aqueous suspension containing cellulosic fibers and optional fillers. In this regard, improved dilution stability means less agglomeration of particles or droplets of the hydrophobic sizing agent, which reduces the level of formation of large aggregates with low sizing efficiency, as well as hydrophobicity to the paper machine. Less sizing agent buildup and less wire mesh contamination, thereby reducing the need for paper machine maintenance. Further benefits seen with the present dispersants are improved stability in the presence of interfering substances such as anionic debris derived from impure pulp and / or recycled fibers, as well as in the white water recycled in the papermaking process. Includes low build-up of hydrophobic material. Accordingly, the dispersions of the present invention are particularly useful in processes where white water is recycled on a large scale and the cellulosic suspension contains a substantial amount of debris. Furthermore, the inventive dispersions also obtain improved sizing over conventional size dispersions at corresponding application rates,
And allows the use of low dosages of sizing agent to achieve the corresponding level of sizing. The ability to use small amounts of sizing agent to achieve sizing to specifications reduces the risk of accumulation of unadsorbed hydrophobic sizing agent in the white water recirculating during the process, which further reduces Reduce the risk of agglomeration and adhesion of hydrophobic materials. The present invention thus offers substantial economic and technical benefits.

The hydrophobic material present in the dispersion is preferably substantially insoluble in water. Examples of suitable hydrophobic materials include compounds useful as sizing agents in papermaking, which are derived from both natural and synthetic sources, such as cellulose-reactive and non-cellulose-reactive hydrophobic materials. To be In a preferred embodiment, the hydrophobic material has a melting point of less than about 100 ° C and especially less than 75 ° C.

In a preferred embodiment of the invention, the hydrophobic material is a cellulose-reactive sizing agent, which can be selected from any of the cellulose-reactive sizing agents known in the art. Suitably the sizing agent is selected from the group consisting of hydrophobic ketene dimers, ketene multimers, acid anhydrides, organic isocyanates, carbamoyl chloride and mixtures thereof, preferably ketene dimers and acid anhydrides, most preferably ketene dimers. Is. Suitable ketene dimers have the general formula (I) below, wherein R ¹ and R ² represent saturated or unsaturated hydrocarbon radicals, usually saturated hydrocarbons, which hydrocarbon radicals are suitably 8 to 36
A straight or branched chain alkyl group having 12 carbon atoms, usually 12 to 20 carbon atoms, such as hexadecyl and octadecyl groups. Suitable acid anhydrides are characterized by the general formula (II) below, wherein R ³
And R ⁴ represent the same or different as well as saturated or unsaturated hydrocarbon radicals, which suitably contain from 8 to 30 carbon atoms, or together with the —C—O—C— component, R ³ and R ⁴
Can form a 5- to 6-membered ring, optionally substituted with a hydrocarbon group containing up to 30 carbon atoms. Examples of commercially available acid anhydrides include alkyl and alkenyl succinic anhydrides and especially isooctadecenyl succinic anhydride.

Suitable ketene dimers, anhydrides and organic isocyanates are described in US Pat. No. 4,52, which is hereby incorporated by reference.
Including compounds disclosed in 2,686. Examples of suitable carbamoyl chlorides are described in US Pat. No. 3,8, which is incorporated herein by reference.
Including those disclosed in 87,427.

In another preferred embodiment of the invention said hydrophobic material is a non-cellulose reactive hydrophobic material, which can be selected from any of the non-cellulose reactive sizing agents known in the art. Suitably the non-cellulose reactive sizing agent is a rosin-based hydrophobic material such as rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, formaldehyde treated rosin, esterified rosin, toughened rosin and such treatments. And rosins treated in this way, fatty acids and their derivatives, such as fatty acid esters and amides such as bisstearamide, resins and their derivatives, such as hydrocarbon resins, resin acids,
It is selected from the group consisting of resin acid esters and amides, waxes such as crude and refined paraffin waxes, synthetic waxes, naturally occurring waxes and the like.

The dispersion according to the invention contains a dispersant, or dispersant system, which comprises at least one anionic compound and at least one cationic compound, both of which have a low molecular weight (hereinafter LMW). The LMW compound is preferably bound by electrostatic attraction, thereby representing a coacervate dispersion. When used in combination, this LMW compound is effective as a dispersant for hydrophobic materials, whereas anionic and cationic compounds do not necessarily have to be effective, and are usually not effective as dispersants when used alone. . In a preferred embodiment, at least one of the anionic and cationic compounds is a polyelectrolyte. As used herein, the term "polyelectrolyte" refers to two or more charged (anionic / cationic) groups and charged (anionic / cationic) compounds, such as chemical nonionic interactions. Or, it acts as a polyelectrolyte through attractive force.

The anionic compound of the dispersant contains one or more anionic groups of the same or different types, and contains an anionic compound having one anionic group and an anionic compound having two or more anionic groups, Here, it is called an anionic polymer electrolyte. The anionic polyelectrolyte may contain one or more cationic groups, as long as the whole is anionic. Examples of suitable anionic groups include sulphate and carboxylic acid groups, sulphonic acid groups, phosphoric acid groups and phosphonic acid groups, which are free acids or water-soluble ammonium or alkali metal (generally sodium) salts such as eg It will be present as sodium carboxylate and sodium sulfonate. The anionic polyelectrolytes can have a wide range of substitution degrees; the anion substitution degree (DS _A ) can be 0.01 to 1.4, suitably 0.1 to 1.2 and preferably 0.2 to 1.0.

The anionic compound of the dispersant can be derived from synthetic and natural sources, and preferably it is water soluble or water dispersible. In a preferred embodiment, the anionic compound is an organic compound, ie it contains carbon atoms.
Suitable anionic compounds are alkyl, aryl and alkylaryl sulfates and ether sulfates, alkyl, aryl and alkylaryl carboxylates, alkyl, aryl and alkylaryl sulfonates, alkyl,
Anionic surfactants such as aryl and alkylaryl phosphates and ether phosphates, and dialkyl sulfosuccinates, wherein the alkyl group is from 1 to 18
The aryl group has 6 to 12 carbon atoms, and the alkylaryl group has 7 to 30 carbon atoms. Examples of suitable said anionic surfactants include sodium lauryl sulphate, sodium lauryl sulphonate and sodium dodecylbenzene sulphonate. Further examples of suitable anionic compounds are derived from optionally degraded anionic organic LMW polymers, such as phosphatized, sulfonated and carboxylated polysaccharides such as starch, guar gum and cellulose. As described above, preferably cellulose derivatives and especially carboxymethyl cellulose, and condensation products such as anionic polyurethanes and condensed naphthalene sulfonates, and also vinyl addition polymers formed from monomers having anionic groups, such as Acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, vinyl sulfonic acid, sulfonated styrene and hydroxyalkyl acrylate and methacrylate phosphates, and optionally acrylamide, alkane Le acrylate, styrene and acrylonitrile and derivatives of such monomers, such as those copolymerized with nonionic monomers including vinyl esters, and the like. The anionic compound can also be selected from LMW inorganic compounds containing silicon atoms, which include, for example, silicates and various forms of condensed or polymerized silicic acid, such as oligomers of silicic acid, polysilicic acid, polysilicic acid, polysilicic acid. Such as aluminum silicates, polysilicate microgels, polyaluminum silicate microgels and silica-based materials, eg silica sols, which have negative hydroxyl groups.

The cationic compound of the dispersant contains one or more cationic groups of the same or different type and one cationic group and, here, a cationic polyelectrolyte,
It includes a cationic compound having two or more cationic groups. The cationic polyelectrolyte may contain one or more anionic groups as long as it has a cationic charge as a whole. Examples of suitable cationic groups are sulfonium groups,
Acid addition salts of phosphonium groups, primary, secondary and tertiary amine or amino groups and quaternary ammonium groups are mentioned, for example where the nitrogen is methyl chloride, dimethyl sulfate or benzyl chloride, preferably amines. / Quaternized with acid addition salts of amino and quaternary ammonium groups. The cationic polyelectrolytes can have a degree of substitution that varies over a wide range; the degree of cation substitution (DS _C ) can be 0.01 to 1.0, suitably 0.1 to 0.8 and preferably 0.2 to 0.6.

The cationic compound of the dispersant can be derived from synthetic and natural sources and is preferably water-soluble or water-dispersible. This cationic compound is preferably an organic compound. Examples of suitable cationic compounds include cationic surfactants, for example compounds of the type R ₄ N ⁺ X ⁻ , where the R groups are freely selected from:
(I) hydrogen; (ii) a hydrocarbon group, suitably an aliphatic and preferably an alkyl group, having 1 to about 30 carbon atoms, suitably 1 to 22 carbon atoms; and (iii) carbonization. A hydrogen radical, suitably an aliphatic and preferably an alkyl radical,
Shielding groups having up to about 30 carbon atoms, preferably 4 to 22 carbon atoms, and containing one or more heteroatoms, such as oxygen or nitrogen, and / or heteroatoms, such as carbonyl and acyloxy groups. At least one, suitably at least three and preferably all of said R groups contain carbon atoms; suitably at least one and preferably at least two of said R groups,
Containing at least 7 carbon atoms, preferably 9 carbon atoms and most preferably at least 12 carbon atoms; and wherein X ^- is an anion, typically a halide such as chloride, or the anionic nature of the dispersant The anionic group present in the compound, eg the surfactant here is a protonated amine of the formula R ₃ N, wherein R and N are as defined above. Examples of suitable surfactants are dioctyldimethylammonium chloride, didecyldimethylammonium chloride, dicocodimethylammonium chloride, cocobenzyldimethylammonium chloride, coco (rectification) benzyldimethylammonium chloride, octadecyltrimethylammonium chloride, dioctadecyl chloride. Dimethylammonium, dihexadecyldimethylammonium chloride, di (hydrogenated tallow) dimethylammonium,
Included are di (hydrogenated tallow) benzylmethylammonium chloride, (hydrogenated tallow) benzyldimethylammonium chloride, dioleyldimethylammonium chloride, and di (ethylenehexadecanecarboxylate) dimethylammonium chloride. Particularly preferred cationic surfactants thus comprise at least one hydrocarbon radical having 9 to 30 carbon atoms and especially quaternary ammonium compounds. Further suitable cationic surfactants include quaternary di- and polyammonium compounds, which are at least one hydrocarbon group, suitably aliphatic and preferably alkyl, from 9 to 30 carbon atoms, preferably From 12
It has 22 carbon atoms. Examples of suitable surfactants of this type include N-octadecyl-N-dimethyl-N'-trimethylpropylene-diammonium dichloride. Further examples of suitable cationic compounds include cationic polyelectrolytes, which are optionally degraded cationic organic LMW compounds, such as those derived from polysaccharides such as starch and guar gum, polyurethanes, Cationic condensation products such as polyamidoamine,
For example, polyamidoamine epichlorohydrin, polyamine such as dimethylamine-epichlorohydrin copolymer, dimethylamine-ethylenediamine-epichlorohydrin-copolymer, ammonia-ethylene dichloride copolymer, having a cationic group Vinyl addition polymers formed from monomers, such as homo- and copolymers of diallyldimethylammonium chloride, dialkylaminoalkyl acrylates, methacrylates and acrylamides (such as dimethylaminoethyl acrylate and methacrylate), which are usually acid addition salts or quaternary ammonium salts. Exist as a nonionic, optionally containing acrylamide, alkyl acrylate, styrene and acrylonitrile and derivatives of such monomers, vinyl esters, etc. Including Nomar copolymerized with one or the like.

Both the anionic and cationic LMW compounds used in the present invention are less than 50,000, suitably 30,00.
It has a molecular weight of less than 0 and preferably less than 20,000 (hereinafter referred to as MW). Further advantages are found at lower MW of the anionic and / or cationic compounds of the dispersant, eg below 15,000 and especially below 10,000. Usually anionic and cationic surfactants
Having a MW of greater than 200 and suitably greater than 500. Usually anionic and cationic surfactants have a lower MW than anionic and cationic polyelectrolytes; preferred surfactants have a MW of 200 to 800. When one of the dispersant compounds is a surfactant, the other dispersant compound is preferably a polyelectrolyte, which may have a MW as defined above.

A preferred dispersion of the present invention is a dispersant (i) comprising a cationic surfactant and an anionic polyelectrolyte, wherein the dispersant has an overall anionic charge; cationic polyelectrolyte and anion. A dispersant (ii) comprising a cationic polyelectrolyte, wherein the dispersant has an overall anionic charge; a dispersant (iii) comprising an anionic surfactant and a cationic polyelectrolyte, wherein The dispersant has an overall cationic charge; a dispersant (iv) comprising an anionic polyelectrolyte and a cationic polyelectrolyte, wherein the dispersion has an overall cationic charge. Including a dispersant selected from the group; said anionic and cationic surfactants, said anionic and cationic polyelectrolytes and their molecular weights as defined above. .

The anionic and cationic compounds of the dispersant may be dispersed in a wide range depending on, among other things, the molecular weight of the compound, the degree of ionic substitution of the compound, ie the charge density, the desired overall charge of the dispersion and the hydrophobic material used. Can exist inside. Both anionic and cationic compounds can be present up to 100% by weight, suitably 0.1 to 20% by weight and preferably 1 to 10% by weight, based on the hydrophobic material.

The dispersion according to the invention can be prepared with a high solids content,
Nevertheless, it has been found to exhibit very good stability on storage and low viscosity. The present invention provides dispersions of hydrophobic materials with improved storage stability and / or high solids content. Particularly preferred dispersions in this regard include cellulose-reactive sizing agents, especially those having a dispersant of anionic charge throughout. Dispersions of cellulose-reactive sizing agents according to the present invention generally have about
It can have a sizing agent content of 0.1 to about 50% by weight, suitably more than 20% by weight. The dispersion containing the ketene dimer sizing agent according to the present invention can have a ketene dimer content in the range of 5 to 50% by weight and preferably about 10 to about 35% by weight. Dispersions, or emulsions, containing an anhydride sizing agent according to the present invention, can have an anhydride content in the range of about 0.1 to about 30% by weight and usually about 1 to 20% by weight. Non-cellulose reactive dispersions are generally 5 to 50
It is possible to have a sizing agent content of up to and, preferably, from 10 to 35% by weight.

The dispersion according to the present invention mixes the aqueous layer with the dispersant system and the hydrophobic material, preferably at a temperature at which the hydrophobic material is a liquid, and homogenizes the resulting mixture, suitably under pressure. It can be produced by The resulting aqueous emulsion contains hydrophobic droplets, which typically have a diameter of 0.1 to 3.5 μm, and are then cooled. In addition to the ingredients mentioned above, other ingredients can also be added to the size dispersion,
These are, for example, additional dispersants and stabilisers, such as nonionic dispersants, extenders, such as urea and urea derivatives, and preservatives. The negative and positive charges of the dispersant compounds are in-situ, for example by contacting the compounds with one another and / or by mixing these compounds with an aqueous layer and / or by lowering the pH of the aqueous layer. It is evaluated that it can be formed. For example, losing hydrogen from an acid group forms an anionic charge, and a basic amine or amino group becomes cationic by protonation or abstraction of hydrogen. Therefore,
It is possible to start with the uncharged compound to prepare the dispersion. For example, organic compounds having a basic amino group of formula R ₃ N or a basic amine can be used, in which the corresponding ammonium component R ₄ N ⁺ X ⁻ is formed in the preparative step, where R, N and X can be as defined above.

It has been found that the components of this dispersion can be easily homogenized in the presence of an aqueous layer, especially the LMW compound of the dispersant at about 100 ° C.
Can be easily homogenized when used in combination with a hydrophobic material having a melting point of less than, and especially less than about 75 ° C. Generally, this step requires less energy and shearing force than conventional methods of preparing dispersions, and this allows the use of simple equipment. Therefore, a further method of preparing the dispersion is (i) mixing the hydrophobic material with the anionic and cationic compounds of the dispersant,
Obtaining an intermediate composition, and (ii) homogenizing the intermediate composition in the presence of an aqueous layer, as described above. It is preferred to mix the components homogeneously in step (i). Stage (i)
Although the hydrophobic material used in step 1 may be solid, it is preferably liquid to simplify homogeneous mixing. If desired, the intermediate composition can be removed after the mixing step (i) and optionally cooled to solidify to form a substantially anhydrous intermediate composition comprising a dispersant and a hydrophobic material. , Which allows easy shipping in an economically attractive way. Where or where it is intended for use, the intermediate hydrophobic composition can be homogenized in the presence of water in a conventional or simple manner, optionally at elevated temperature to render the intermediate composition a liquid. This method is particularly attractive when preparing dispersions of ketene dimers and acid anhydrides, which are usually prepared in the paper mill directly related to their use as sizing agents in the production of paper. The provision of storage-stable substantially anhydrous compositions thus offers considerable economic and technical benefits. The invention therefore also provides a substantially anhydrous concentrated composition comprising a hydrophobic material, an anionic LMW compound selected from carbon-containing compounds and silicon-containing compounds, and a cationic LMW organic compound, as further defined in the claims, It also relates to its preparation and use. Here, the anionic and cationic compounds, when used in combination, are effective as a dispersant system for the hydrophobic material of the aqueous layer.

The components present in the concentrated composition according to the invention, namely the hydrophobic material and the anionic and cationic compounds, are preferably as defined above. This composition is substantially anhydrous and means that a small amount of water can be present; the water content is from 0 to 10% by weight, suitably less than 5% by weight and preferably less than 2% by weight. possible. Most preferably the composition is water free. The composition preferably comprises a major amount, on a weight basis, of a hydrophobic material, i.e. at least 50% by weight, and suitably the composition is in the range 80 to 99.9% and preferably 90 to 99.7% by weight. It has a hydrophobic content of. The anionic and cationic compounds can be present in the composition in the amounts defined above for the dispersant, the percentages being based on the hydrophobic material. Therefore, both the anionic and cationic compounds are present in the composition.
It can be present in an amount of up to 0% by weight, suitably 0.1 to 20% by weight and preferably 1 to 10% by weight, based on the hydrophobic material.

The dispersions of the present invention can be used as sizing agents in the conventional manner in the production of paper with any type of cellulosic fiber, and they can be used both as surface sizing and as internal or raw sizing. it can. As used herein, the term "paper" is meant to include not only paper, but also all types of sheet and web-shaped cellulosic-based products, including, for example, cardboard and paperboard. The raw material comprises cellulosic fibers, optionally in combination with mineral fillers, and usually the content of cellulose fibers is at least 50% by weight, based on the dry raw material.
Is. Kaolin is an example of a conventional type of mineral filler,
White clay, titanium dioxide, gypsum, talc and chalk,
Included are natural and synthetic calcium carbonates such as ground marble and precipitated calcium carbonate. The amount of hydrophobic sizing agent added to the raw material is 0.01 to 5% by weight, based on the dry weight of cellulosic fibers and optional fillers,
Suitably it can be from 0.05 to 1.0% by weight, where the amount applied depends mainly on the quality of the pulp or paper being sized, the sizing agent used and the level of sizing desired.

In a preferred embodiment, the dispersion is used in the raw material sizing of cellulosic pulp, where the raw material has a high cationic demand and / or contains a substantial amount of lipophilic substances, for example certain grades of wood-containing and recycled pulp. The recycling of raw materials prepared from, for example white water, is a large scale. A particularly preferred dispersion for such applications is a dispersion having a cellulose-reactive sizing agent and a dispersant of anionic charge overall. Usually the cation demand is at least 50, suitably at least 100 and preferably at least 150 μeq / liter feed filtrate. For cation demand, a conventional method, for example, a 1.6 μm filter and a raw material filtrate obtained from a raw material filtered through poly (diallyldimethylammonium chloride) as a titration liquid are used to measure a Mtek Particle Charge
It can be measured by Detector. The amount of lipophilic extract is determined by extraction with DCM (dichloromethane) in a known manner.
measured as pmDCM, at least 10 ppm, usually at least 20 ppm, suitably at least 30 ppm and preferably 50
can be ppm. Furthermore, the dispersion is preferably used in papermaking processes in which white water is recycled on a large scale, ie due to the high degree of white water entrapment, for example here 0 to 30 tons of fresh water is used per ton of dry paper produced. , Usually less than 20 tons, suitably less than 15 tons, preferably
Paper produced by less than 10 tons and especially 5 tons of fresh water 1
Used per ton. The recycling of white water in this step is preferably mixing white water with cellulose fibers, preferably in the form of a raw material or suspension, before and after the addition of the sizing dispersion, for example to form a raw material for dehydration. Caused by. Fresh water can be introduced into the process at any stage; for example, fresh water can be mixed with cellulosic fibers to form a raw material, and before and after mixing the raw material with white water and before and after adding the sizing dispersion, the fresh water contains cellulosic fibers. The cellulose fibers are diluted so as to form a raw material that can be mixed with and dehydrated.

Chemicals such as retention improvers, aluminum compounds, dyes, wet strength improving resins, optical brighteners, etc., which are conventionally added to raw materials in papermaking, can of course be used with the present sizing dispersion. The non-cellulose reactive sizing agent is
Usually used with aluminum compounds to fix sizing agents to cellulosic fibers. Examples of aluminum compounds include alum, aluminates and polyaluminum compounds, such as polyaluminum chlorides and sulfates. Examples of suitable retention aids are cationic polymers, anionic inorganic materials in combination with organic polymers, for example bentonite in combination with cationic polymers, cationic polymers or silica-based sols in combination with cationic and anionic polymers. Is mentioned. Particularly good raw material sizing is obtained when using the dispersions of the invention in combination with a retention enhancer containing a cationic polymer. Suitable cationic polymers include cationic starch, guar gum, acrylate and acrylamide based polymers, polyethyleneimine, ginandiamido-formaldehyde, polyamines, polyamidoamines and poly (diallyldimethylammonium chloride) and mixtures thereof. Cationic starch and cationic acrylamide-based polymers are preferably used alone or in combination with each other or with other materials. In a preferred embodiment of the present invention the dispersion is used in combination with a retention enhancer system comprising at least one cationic polymer and anionic silica based particles. The dispersion can be added before, during, after or simultaneously with the addition of the cationic polymer or polymers. Prior to adding the size dispersion to a retention aid, for example a cationic polymer such as a cationic starch or a cationic acrylamide-based polymer, or an anionic silica-based material, the mixture thus obtained is added to the raw material. Mixing is also possible. Thus, the dispersion is dispersed in the raw material by contacting a size dispersion containing a cationic compound, preferably a cationic surfactant, with an anionic silica-based material, such as defined above. Can be prepared immediately before the introduction.

The invention is further described in the following examples, which, however, are not intended to be limiting. Unless stated otherwise, parts and% refer to parts by weight and% by weight, respectively.

Example 1 A dispersion of an alkylketene dimer (AKD) according to the present invention was prepared by using Akzo N as a cationic surfactant having a MW of 340.
Melted at 70 ° C with di (hydrogenated beef tallow) dimethylammonium chloride sold under the trade name Querton 442 by obel AKD
And mix this mixture from Rohm & Haas Company O
Prepared by passing the homogenizer through an homogenizer in the presence of an aqueous solution of condensed sodium naphthalene sulphonate of about 6,000 commercially available under the trade name rotan ^™ , then cooling the dispersion thus obtained. The pH of this dispersion was adjusted to about 5 by adding acid. The dispersion, designated Dispersion No. 1, had an AKD content of 30% and both contained 6% anionic compound and 4% cationic compound, based on the weight of AKD. This dispersion contains cellulose-reactive hydrophobic particles with an average particle size of about 1 μm, which is based on ZetaMast.
It was anionically charged as indicated by the negative zeta potential measured by er SVersion PCS.

Example 2 The stability of the dispersion of Example 1 was tested as follows: this dispersion was diluted with water to give a dispersion containing 40 ppm AKD. In some tests, 10 ppm stearic acid was added and stability was evaluated in the presence of lipophilic, anionic garbage substances. This diluted dispersion was placed in a jar equipped with a turbidity measuring device, a loop, circulation means and heating and cooling means. An aliquot of this diluted dispersion was circulated in a loop, during which turbidity was automatically recorded and the dispersion was subjected to heating and cooling cycles at intervals set at 45 minutes. The temperature of this dispersion was raised from 20 ° C to 62 ° C and then lowered to 20 ° C again. Turbidity is affected by particle size, and the difference in turbidity of the dispersion before and after temperature cycling is a measure of the ability of the dispersed particles to withstand growth by agglomeration, and thus the stability of the dispersion. This turbidity difference (ΔT) is calculated as follows: ΔT = (last turbidity / first turbidity) × 100. The higher ΔT, the better the stability.

Two standard dispersions were also tested for comparison purposes; Reference Example 1 shows sodium lignosulfonate and high molecular weight (HM
W) Anionic A containing a dispersant system consisting of cationic starch
KD dispersion, in which the anionic lignosulfonate is present in ionic excess; Reference Example 2 is also a cationic AKD dispersion containing sodium lignosulfonate and HMW cationic starch, but here The cationic starch is present in ionic excess. Table 1 shows the results obtained.

As shown in Table 1, the ΔT values of the inventive dispersions are considerably higher than those of the standard dispersions (Reference Examples 1 and 2), which thus show good dilution stability.

Example 3 An anhydrous concentrated composition according to the invention, 93 parts AKD pellets, 3 parts cationic surfactant and 4 parts Example 1
It was prepared by dry mixing the anionic compound used in 1. The dry mixture was subsequently added hot water and the aqueous mixture thus obtained was heated to 80 ° C., pumped with a high shear pump and then cooled to room temperature. The resulting anionic dispersion, Dispersion No. 2, had an AKD content of 20% and an average particle size of about 1 μm.

Sizing efficiency was achieved by preparing a paper sheet by the laboratory-scale standard method SCAN-C23X and adding 80% 60:40 bleached birch / pine sulphate and 0.3 g / l Na ₂ SO ₄ · 10H ₂ O. The evaluation was performed using the papermaking raw material containing 20% of added chalk. The raw material had a consistency of 0.5% and a pH of 8.0. This dispersion was used with a commercial retention and dehydration system, Compozil ^™ , which contained cationic starch and anionic aluminum modified silica sols, which were added separately to the raw materials;
Cationic starch was added in an amount of 12 kg / ton based on dry raw material, and silica sol was calculated as SiO ₂ and added in an amount of 0.8 kg / ton based on dry raw material.

Table 2 shows the Cobb values obtained in this test, which were measured by TAPPI standard T 441 OS-63. The amount of AKD applied is based on dry ingredients.

Table 2 shows the improvement in paper sizing obtained with the dispersion according to the invention.

Example 4 The ease of producing the dispersions according to the invention is
The D content was evaluated by preparing an anionic AKD dispersion. The dispersion of the invention comprises 0.8% by weight of di (hydrogenated tallow) dimethylammonium chloride, 1.6% by weight of concentrated sodium naphthalenesulfonate, 77.5% by weight of water and
Ultra Turrax m with a mixture of 20 wt% AKD at 15,000 rpm
It was prepared by homogenizing for a period of time using an ixer, then the dispersion thus obtained was cooled for 2 hours. Similar dispersions were prepared in the same way with different AKD contents to prepare dispersions with AKD contents of 10, 20, 30 and 40% by weight. These dispersions are designated Inv. Followed by an AKD content of% by weight.

Homogenize a mixture of 1.0 wt% cationic starch, 0.25 wt% sodium lignosulphonate, 89 wt% water and 10 wt% AKD in the same manner and under the same conditions as a standard AKD dispersion. It was manufactured by Similar dispersions were prepared with different AKD contents, AKD contents 10, 2
Standard dispersions of 0, 30 and 40% by weight were prepared. These dispersions are shown in Reference Example 3 followed by a wt% AKD content.

The particle size and viscosity were evaluated by conventional methods. Table 3 shows the results obtained.

Table 3 shows that it is easy to prepare the dispersions according to the invention; low viscosities are obtained with corresponding AKD contents, and small particles give the same amount of energy to free the surface. Was obtained using. Less energy and lower shear are required by the present invention to produce dispersions of equal particle size as compared to standard dispersions. In addition, increasing the stirrer speed to 25,000 rpm considerably reduces the particle size of the dispersions according to the invention to be in the range 1 to 2 μm.

─────────────────────────────────────────────────── --Continued front page (31) Priority claim number 9704932-4 (32) Priority date December 30, 1997 (December 30, 1997) (33) Country of priority claim Sweden (SE) (72) Inventor Lindgren Erik Sweden, S-445 34 Bows, Osbacken 28 (72) Inventor Sicker Lane Sweden, S-448 34 Floda, Bethlestigen 2 (56) References European Patent Application Publication 220941 (EP, A) 1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 1/00-101/16 D21H 21/16 WPI / L (QUESTEL)

Claims (20)

(57) [Claims] 1. An aqueous dispersion containing a dispersion layer comprising a dispersant and a hydrophobic sizing agent, wherein the dispersant has the following component (a) a molecular weight of less than 50,000 and a carbon-containing compound and a silicon-containing compound. An anionic compound selected from compounds, and (b) a cationic organic compound having a molecular weight of less than 50,000, wherein at least one of the anionic compound and the cationic organic compound is a polyelectrolyte, and the hydrophobic sizing agent Is selected from the group consisting of cellulose-reactive sizing agents and non-cellulose-reactive sizing agents. 2. The dispersion according to claim 1, wherein the anionic compound and the cationic compound have a molecular weight of less than 20,000. 3. The dispersion according to claim 1, wherein the anionic compound is an organic compound. 4. The dispersion according to claim 1, 2 or 3, wherein the dispersant is anionic and contains a cationic surfactant and an anionic polyelectrolyte. 5. The dispersion according to claim 1, 2 or 3, wherein the dispersant is anionic and contains a cationic polyelectrolyte and an anionic polyelectrolyte. 6. The dispersion according to claim 1, 2 or 3, wherein the dispersion is cationic and contains an anionic surfactant and a cationic polyelectrolyte. 7. The dispersion according to claim 1, 2 or 3, wherein the dispersant is cationic and contains an anionic polyelectrolyte and a cationic polyelectrolyte. 8. Dispersion according to any one of claims 1 to 7, characterized in that it has a hydrophobic sizing content of at least 20% by weight. 9. The dispersion according to claim 1, wherein the hydrophobic sizing is a cellulose-reactive sizing agent. 10. The dispersion according to claim 9, wherein the sizing agent is a ketene dimer or an acid anhydride. 11. The dispersion according to claim 9, wherein the hydrophobic sizing is a non-cellulose reactive sizing agent. 12. Dispersion according to claim 8, 9, 10 or 11, characterized in that the hydrophobic sizing has a melting point below 75 ° C. 13. A dispersant comprising an aqueous layer and an anionic compound having a molecular weight of less than 50,000 and selected from carbon-containing compounds and silicon-containing compounds, and
Method for preparing an aqueous dispersion by homogenizing a hydrophobic sizing, wherein at least one of said anionic compound and cationic organic compound is a polyelectrolyte in the presence of a cationic organic compound having a molecular weight of less than 50,000. . 14. The method according to claim 13, wherein the anionic compound and the cationic compound have a molecular weight of less than 20,000. 15. The method according to claim 13, wherein the anionic compound is an organic compound. 16. Use of the aqueous dispersion according to claim 1 as raw material size or surface size in the production of paper. 17. A hydrophobic sizing, an anionic compound having a molecular weight of less than 50,000 and selected from carbon-containing compounds and silicon-containing compounds, and a cationic organic compound having a molecular weight of less than 50,000, wherein said anion. A substantially anhydrous sizing composition, wherein at least one of the organic compound and the cationic organic compound is a polyelectrolyte. 18. The composition according to claim 17, wherein the anionic compound is an organic compound. 19. The method according to claim 17, wherein the hydrophobic sizing is ketene dimer or acid anhydride.
18. The composition according to 18. 20. Use of the composition according to claim 17, 18 or 19 for the preparation of an aqueous dispersion according to any one of claims 1 to 12.