FI84383C - Concentrate compositions suitable for bonding cellulose fibers - Google Patents

Abstract

An aqueous sizing composition can be made by mixing into water a concentrate that comprises a substantially anhydrous dispersion of a polyelectrolyte in a liquid reactive size.

Description

Concentrate compositions suitable for gluing cellulosic fibers 1 843 ^ 3

The invention relates to the gluing of cellulose fibers and to the compositions used therefor, as well as to their preparation.

During papermaking, it is necessary to render the inherently hydrophilic cellulosic fibers hydrophobic so as to limit the penetration of aqueous liquids into the formed sheets, thus making writing on the sheets possible. This method, known as sizing, can be performed by adding an sizing agent to a pulp slurry (commonly referred to as internal sizing) or the sizing agent can be applied to a formed sheet of paper. This invention relates to an internal gluing process.

There are two types of adhesives in general use. One of them is based on a resin used in connection with aluminum sulphate. The resin is added as a soap solution or emulsion and aluminum sulfate is subsequently added just 20 before sheet formation to precipitate the resin as fine particles remaining on the surface of the sheet.

Another type of adhesive is a reactive adhesive, such as a ketene dimer or anhydride based adhesive, which reacts chemically with cellulosic fibers. Preferably, it is applied together with a polyelectrolyte which helps the adhesive to remain in the sheet.

The reactive adhesive is generally added to the pulp in the form of an aqueous emulsion, usually a cationic emulsion. This emulsion can be prepared in the factory, but this makes emulsification equipment necessary for the factory and so it would be more convenient if a concentrated emulsion could be delivered to the factory ready to be diluted and used. Unfortunately, reactive adhesives tend to react with water so that the aqueous emulsion is prone to considerable instability.

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Anhydride-based adhesives, such as alkenyl succinic anhydride adhesives, are so reactive that their emulsions must be prepared at the factory just before use. These adhesives are usually supplied to the mill with cationic starch, which usually has to be pre-cooked before emulsification, making emulsion formation at the mill even more inconvenient.

Ketene dimers are often supplied to the mill in an emulsion, but these emulsions have only limited shelf life and the maximum concentration of ketene dimers in the emulsion is quite small, usually less than 6%, so that very large emulsion volumes have to be supplied to the paper manufacturer.

Emulsification of liquid ketene dimers can be accomplished using conventional emulsification equipment, but some preferred ketene dimers are solids at ambient temperature. As described in U.S. Patent 3,046,186, emulsification of these necessitates either melting the solid first (so that upon cooling the emulsion becomes a dispersion) or dissolving the solid in a solvent, usually benzene. A typical important ketene dimer is distearyl ketene dimer and its solubility in organic solvents is relatively low with the result that its emulsifiable solution must be quite dilute. For example, it has been found that this dimer precipitates from a 40% by weight benzene solution (weight ratio benzene / dimer, 1: 0.67) and so the benzene solution must be much more dilute than this. This dimer is still even less soluble in other organic solvents than it is in benzene.

As described in U.S. Patent 3,046,186, emulsions are generally prepared by emulsifying a dimer into an aqueous solution of a cationic dispersant, although that publication does not mention that in certain cases the emulsifier may be predispersed in the ketene dimer. It is claimed that emulsions can be prepared at any suitable dry matter content, but are used at a dry matter content of 1-5% by weight.

The starting composition prepared in each of U.S. Patent 3,046,186, Example 5, which contained both an adhesive and a polyelectrolyte, was very dilute. For example, in Example 1, the initial concentration was about 9% by weight of adhesive based on the total composition.

In each case, in the U.S. patent, an emulsifier or dispersant was added as an aqueous solution.

Also in each case, the starting composition contains significant amounts of excess water. In the case of ketene dimer adhesives, as in U.S. Patent 3,046,186, this is tolerable provided that the starting composition 15 is not stored for too long.

As mentioned above, it is preferable to supply the polyelectrolyte with the reactive adhesive, and it would be contemplated that some of the disadvantages associated with measuring reactive adhesive and polyelectrolyte emulsions could be minimized if the reactive adhesive and polyelectrolyte were supplied separately. However, there are other disadvantages to this.

Therefore, it would be advantageous if it were possible to supply a stable, concentrated composition containing both reactive adhesive and polyelectrolyte and easily dilutable with water at the factory.

In EP-A-0 141 641 A2 (same applicant; not published as a priority date of this invention), the applicant describes concentrated compositions comprising a substantially anhydrous polyelectrolyte dispersion in an organic liquid formed by a solution of a reactive adhesive in a hydrophobic solvent. The concentration of reactive adhesive in such compositions is generally greater than 20%, and although it may be as high as, for example, 85%, it is generally lower.

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The present invention relates to a substantially anhydrous storage-resistant concentrate composition suitable for gluing cellulosic fibers after dilution with water, characterized in that the composition is an anhydrous dispersion of a cationic or anionic polyelectrolyte in a liquid reactive adhesive and the composition is the content is at least JO% by weight.

Preferably, the composition of the invention is free of any solvent, but if present, the amount is insufficient to significantly affect the physical properties of the composition, e.g., less than 5% and usually less than 1% solvent by weight of the composition.

While in EP 0 141 641 A2 the adhesive may be solid or liquid and was present in the composition as a solution in a hydrophobic solvent, in the present invention the adhesive must be liquid at the temperature at which the composition is used and stored, typically at ambient temperatures such as 20-25 ° C. The adhesive is liquid at 0 ° C.

Preferably, the liquid adhesives for use in the invention are reactive anhydride adhesives, including in particular alkenyl succinic anhydride adhesives. Suitable materials are described in U.S. Patent 3,102,064.

Numerous other reactive adhesives are liquid, such as certain ketene dimer adhesives, and can be used in the invention.

The concentrate composition must be substantially anhydrous so that the reactive adhesive does not react in the composition during storage. The amount of water is generally no more than the equilibrium moisture content of the polyelectrolyte (i.e., the water content of the polyelectrolyte if exposed to the ambient atmosphere in the form of a dry powder) and is preferably less than 1% or at most 2% by weight of the composition.

The polyelectrolyte is generally water soluble and the advantage of the invention is that it can have any desired molecular weight and in particular its molecular weight can be higher than is suitably possible with existing compositions. For example, the intrinsic viscosity may typically be greater than 1 and generally greater than 3, for example greater than 6. Although it is generally less than 9, it may be greater, e.g., 10 up to 20 or greater.

The polyelectrolyte may be formed from a water-soluble ethylenically unsaturated monomer (or a water-soluble mixture of ethylenically unsaturated monomers) and may be cationic or anionic, with cationic polyelectrolytes generally being preferred.

Preferred cationic electrolytes include diallyldialkyl (usually dimethyl) ammonium chloride. n homopolymers or copolymers and homopolymers and copolymers of dialkylaminoalkyl acrylates and methacrylates (preferably dimethyl-aminoethyl acrylates and methacrylates) present with acid addition salts or quaternary ammonium salts of acid addition salts or quaternary ammonium salts Copolymers of such monomers can be formed with acrylamide or methacrylamide and typically contain at least 10% by weight and usually at least 30% by weight of cationic monomers. Other cationic acrylamides and methacrylamides can be used. Other cationic polymers that can be used include polyamines and polyimines such as polyamine-epi-halohydrin polymers and dicyandiamide condensates and polyethyleneimines.

Suitable anionic polymers include polymers formed from monomers containing carboxylic or sulfonic acid groups. These groups may be present as the free acid or, more usually, as a water-soluble ammonium or alkali metal (usually sodium) salt. Suitable acids include acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid. Sodium al-5 yl sulfonate can be used. The anionic polymers may be homopolymers or copolymers of such acids or mixtures thereof with, for example, arylamide. A suitable polymer is polyacrylamide containing up to 25% more acrylic acid groups.

The particle size of the polyelectrolyte is generally less than 500 and preferably less than 200.

The new compositions can be obtained by mixing the powdered polyelectrolyte with a liquid reactive adhesive. In these compositions, the polyelectrolyte particle size 15 is generally greater than 5 and usually greater than 10, and often the maximum particle size is in the range of 20 to 100.

The composition should necessarily be used with the polyelectrolyte substantially uniformly dispersed throughout the liquid reactive adhesive. If the composition tends to settle, it should therefore be used before undispersed sediment formation occurs. Precipitation can be minimized or prevented by the inclusion of an effective amount (e.g., 0.1-10%) of a dispersant. For example, dispersion stabilizers that are insoluble in the reactive adhesive may be used, such as clay and silicic acid-based dispersion stabilizers known to stabilize dispersions in oil. Preferred stabilizers for this purpose are organophilic clays, such as those sold under the tradename BEN-TONE. Glue-soluble stabilizers can also be used.

However, the preferred particle size of the polyelectrolyte of the preferred compositions of the invention is less than 10, preferably less than 3. Although a dispersant may be added to the composition, the amount required is usually 7,838,33. For example, the deliberate addition of clays is usually unnecessary. The particles are preferably prepared by reverse phase polymerization, preferably in the presence of a known type of dispersant stabilizer for use in reverse phase polymerization. The presence of residues of this in the polymer particles is generally sufficient to stabilize the compositions of the invention.

Particularly preferred compositions are prepared by mixing a substantially anhydrous dispersion of polyelectrolyte in a volatile organic liquid with a liquid adhesive and then evaporating this organic liquid. The volatility of the liquid should be such that it can be evaporated from the dispersion in a liquid reactive adhesive below the temperature at which an adverse chemical reaction can occur.

The particle size of this dispersion in the organic liquid should be less than 10 and often less than 3. Preferably it is less than 2, often mainly in the range of 0.05 to 1. It can be prepared by reverse phase polymerization of a water-soluble monomer or monomer mixture dispersed in a water-immiscible organic liquid. Reverse phase polymerization can be carried out in the presence of an oil-soluble polymer, generally an amphipathic polymer, as a dispersion stabilizer, and this stabilizer can also contribute to the stability of the final dispersion in the liquid adhesive. Reverse phase polymerization can also be performed in water-in-oil in the presence of an emulsifier. Reverse phase polymerization materials and methods are well known and are described, for example, in EP Patent Application 30 0 126 528. Suitable organic liquids that can be used in the dispersion include volatile aliphatic hydrocarbons.

After the polyelectrolyte dispersion has been prepared in an organic liquid by reverse phase polymerization, the dispersion is dehydrated to a substantially anhydrous state of 84,8383 in a conventional manner, generally by azeotropic distillation.

If desired, the concentration of the continuous organic phase can be changed in a known manner after polymerization in order to optimize the volatility of the organic liquid (which must be evaporated from the dispersion of the polyelectrolyte and the organic liquid in the liquid adhesive).

The compositions of the invention lack essential. i solvent or other diluents and at least 10 80%, preferably at least 85% or at least 90% consists of polyelectrolyte and liquid adhesive. Preferred compositions contain 45 to 90% by weight, preferably 60 to 80% by weight of reactive adhesive, 10 to 50% by weight, preferably 20 to 40% by weight of polyelectrolyte and 0 to 15%, preferably 5 to 10% by weight of additives such as described insoluble or soluble stabilizers or water-in-oil emulsifiers.

Preferably, the additives include an oil-in-water emulsifier which acts to facilitate emulsification of the concentrate into the water at the time of use. Instead of adding an oil-in-water emulsifier to the concentrate, it may be present in the water into which the concentrate is emulsified. If suitable mixing equipment is available, adequate emulsification can be achieved without the use of an oil-in-water emulsifier, but this is usually less preferred.

The concentrate is converted to an emulsion in water before use.

The water in which the emulsion is formed may be water of the cellulosic pulp suspension to be treated, but preferably the concentrate is first converted to an aqueous emulsion to give a reactive adhesive concentration of 0.01 to 5%, preferably 0.05 to 1% by weight of the aqueous solution.

This emulsion can then be added to the aqueous cellulosic pulp and made into paper in the usual manner. The amount of reactive adhesive in the aqueous pulp is generally in the range of about 0.01 to about 1% by weight based on the dry weight of the pulp. After addition to the pulp slurry, the polymer retains the active adhesive / oil droplets on the fibers and the adhesive reacts with the fibers. The adhesive removed from the emulsion in this way produces at least as good results as those obtained from conventional ketene dimer emulsions.

Thus, the invention provides at least as good adhesive results as those obtained using known compositions, and yet for the first time it is possible to produce storage-stable concentrated compositions which can be easily converted by the user into aqueous solutions and which contain both polyelectrolyte and adhesive and substantially free of ingredients other than adhesive and 15 polyelectrolyte.

Example 1

A sizing concentrate containing alkenyl succinic anhydride as an active sizing ingredient was prepared by dispersing the ground polyelectrolyte in a liquid sizing ingredient to which an oil-in-water emulsifying surfactant had been added.

The alkenyl succinic anhydride selected was liquid at ambient temperature and did not need to be melted to effect dispersion.

A polyelectrolyte, a copolymer of methyl chloride quaternized dimethylaminoethyl methacrylate and acrylamide (25.75 wt.%), Was prepared by bulk solution polymerization. The resulting polymer gel was cut into particles less than 5 mm in size, dried in a liquid bed dryer, and then ground to the required length of less than 53 microns.

The composition contained 65 g of alkenyl succinic anhydride, 10 g of an oil-in-water emulsifying surfactant and 12.5% of a polyelectrolyte to give 74.3% of an active sizing composition. The mixture was anhydrous visually.

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Example 2 2.7 g of the concentrate composition prepared in Example 1 was added to 197.3 g of water with stirring to give a 1% active alkenyl succinic anhydride emulsion which was used for 1 minute Cobb experiments. This emulsion was labeled A: 11a.

For this experiment, 100 g / m2 hand sheets were prepared from bleached sulfate / bleached birch pulp containing a 10% dose of calcium carbonate on a Standard 10 Laboratory actin machine. Prior to sheet formation, the required amount of the 1% alkenyl succinic anhydride emulsion prepared above was added to 600 ml of a 1% thick pulp. After mixing, the hand sheets were made on a standard sheet making machine. The sheets were transferred from a sheeting machine to be pressed onto polishing plates in the normal manner and pressed at 345 kPa for 5 minutes before drying on cylinders at 110 ° C for 1 hour. The degree of adhesion achieved after returning to room temperature was measured by a standard 1 minute 20 Cobb test. The results are shown in the following table.

Alkenyl succinic anhydride 1 minute Emulsion dose level calculated on the dry Cobb value 25 fibers and filler g / m2 A 0.24% 18.1 A 0.34% 15.9 A 0.57% 13.4 30 _

Example 3

A concentrate similar to Example 1 is prepared using instead of a comminuted gel polymer a hel-35 ml polymer prepared by reverse phase bead polymerization followed by azeotropic distillation and separation of the beads from the oil in which they formed.

Example 4

To prolong the shelf life of the concentrate of Example 1, an appropriate amount of Bentone 38 can be added.

Example 5

Preparation of an alkenyl succinic anhydride version of a cationic copolyacrylamide A copolymer containing 75 parts by weight of acrylamide and 25 parts by weight of trimethyl-β-acryloxyethylammonium chloride was prepared as follows: : 287.4 g of a 52.5% aqueous solution of acrylamide, 0.05 g of azobisisobutyronitrile and 160.2 g of water were mixed to form a solution whose pH was adjusted to 4.6 with sodium hydroxide solution (46% w / w), then 71.0 g of a 70.4% aqueous solution of trimethyl-β-acrylic-20-oxytriethylammonium chloride was mixed to form an aqueous solution of the monomer. An oil phase was prepared consisting of 363.3 g of SBP11, 14.2 g of a 2-1 molar copolymer of stearyl methacrylate and methacrylic acid as a suspension polymerization stabilizer (as described in GB Patent 1,482,515) and 7.8 g of Span 80.

The aqueous phase was homogenized with the oil phase and the oxygen was removed using nitrogen gas, then polymerized by stirring with 1.5 ml of 5% aqueous sodium metabisulphite solution and then a 1% solution of tertiary butyl-30-hydroperoxide in SBP11 added at 0.25 ml per minute until the polymerization was complete.

The resulting aqueous dispersion of polymer gel was dehydrated azeotropically under reduced pressure by circulating SBP11. A portion of the SBP11 was then distilled off to give a 35 anhydrous polymer dispersion with a concentration of 40% by weight of polymer in SBP11.

i2 84383 250 g of this 40% copolymer dispersion was mixed with 500 g of alkenyl succinic anhydride and distilled under reduced pressure to remove SBP11. The final distillation conditions were 95 ° C at 5,333 Pa. The product obtained was a stable dispersion of 100 g of polymer in 500 g of liquid reactive adhesive. It could be made self-emulsifiable by adding sun from its HBL. Iria surfactants.

K. Erkki 6 The concentrate described in Example 5 was used to prepare a corresponding aqueous emulsion having an active adhesive content of 1% by weight by mixing an appropriate amount of the dispersion with water. This emulsion was further diluted to a concentration of 0.1% by weight of active glue, and this was labeled with B.

For comparison, a conventional alkenyl succinic anhydride emulsion was prepared as follows:

A 12% aqueous dispersion of cationic starch was boiled at 95 ° C for 20 minutes with constant stirring. The cooked starch was cooled and diluted to 9% activity. 2 parts by weight of alkenyl succinic anhydride were added with stirring to 3 parts by weight of cationic starch. Stirring with high shear using a Silverson mixer was continued to achieve a fine particle size emulsion. This emulsion was diluted with water to a concentration of 0.1% by weight of active adhesive, and this was denoted by C.

100 g / m2 hand sheets were prepared from a bleached sulphate / bleached birch wood mixture containing 10 30% portions of calcium carbonate on a standard laboratory sheet machine. Prior to sheet formation, the required amount of 0.1% emulsion, marked B, was added to 600 ml of 0.1% pulp. After mixing, hand sheets were prepared and pressed at 345 kPa for 5 ml to 35 minutes before drying at 110 ° C for 1 hour.

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After returning to room temperature, the degree of adhesion was determined by a standard 1-minute Cobb test.

Reference sheets were prepared in the same manner as described above, but Emulsion B was replaced with Emulsion 5 C. The results are shown below:

Alkenyl succinic anhydride 1 minute Emulsion dose level based on dry Cobb value of fiber and filler g / m2 10__ B 0.25% 22.1 B 0.35% 16.4 B 0.5% 13.7 C 0.25% 27.2 15 C 0.35% 20.1 C 0.5% 15.6

Claims (14)

A substantially anhydrous, storage-resistant concentrate composition suitable for gluing cellulosic fibers after dilution with water, characterized in that the composition is a substantially anhydrous dispersion of a cationic or anionic polyelectrolyte in a liquid reactive adhesive, that the composition is substantially solvent-free and the total content of polyelectrolyte is at least 80% by weight. Composition according to Claim 1, characterized in that it contains 45 to 90% by weight of reactive adhesive and 10 to 50% by weight of polyelectrolyte and that the total amount of polyelectrolyte and adhesive 15 is at least 85% by weight. Composition according to Claim 1, characterized in that it contains 60 to 80% by weight of reactive adhesive and 20 to 40% by weight of polyelectrolyte and 5 to 10% by weight of additives selected from emulsifiers and dispersion stabilizers. Composition according to any one of the preceding claims, characterized in that the polyelectrolyte has a particle size of 5 to 500 μm and that the composition is prepared by mixing the polyelectrolyte with a liquid reactive adhesive and an added dispersion stabilizer. Composition according to one of Claims 1 to 3, characterized in that the particle size of the polyelectrolyte is less than 10 μm. Composition according to Claim 5, characterized in that the polyelectrolyte is prepared by reversed-phase polymerization in the presence of a dispersion stabilizer which acts as the sole dispersion stabilizer in the composition. Composition according to one of the preceding claims, characterized in that it is prepared by mixing with a liquid adhesive a substantially anhydrous dispersion of polyelectrolyte 84383 in a volatile organic liquid and then evaporating off the organic liquid. Composition according to Claim 7, characterized in that the substantially anhydrous dispersion of polyelectrolyte in a volatile organic liquid is a dispersion prepared by reverse-phase polymerization of a water-soluble ethylenically unsaturated monomer or a water-soluble mixture of ethylenically unsaturated monomers and a water-insoluble mixture of ethylenically unsaturated monomers. 2 pm. Composition according to one of the preceding claims, characterized in that the adhesive is an alkenyl succinic anhydride adhesive which is liquid at 20 ° C. Composition according to any one of the preceding claims, characterized in that the polyelectrolyte is selected from polymers formed from at least one monomer selected from dialkylaminoalkyl acrylates and methacrylates and their acid addition salts and their quaternary ammonium salts; diallyldialkylammonium chloride; acrylamide; acrylic acid, methacrylic acid and 2-acrylamido-2-methylpropanesulfonic acid and water-soluble salts; 25 and sodium allyl sulfonate and polyamine and polyimine polymers. Composition according to any one of the preceding claims, characterized in that it further contains an oil-in-water emulsifier. A process for preparing an aqueous adhesive composition, characterized in that a concentrate according to any one of the preceding claims is dispersed in water in an amount sufficient to provide a reactive adhesive concentration in water of 0.01 to 5% by weight. 84383 BC A method of gluing cellulosic fibers, characterized in that an aqueous cellulosic pulp or cellulose paper made from such a pulp is treated with an aqueous adhesive composition prepared by dispersing a concentrate according to any one of claims 1 to 11 in water in an amount sufficient to provide a reactive adhesive concentration of 5% by weight. A process for preparing a composition according to claim 1, characterized in that a substantially anhydrous dispersion of polyelectrolyte in a volatile organic liquid is mixed with the liquid reactive adhesive and then the organic liquid is evaporated off. i7 84383