EP0200755B1

EP0200755B1 - Hydrophobing agent for cellulosic fibers, method of preparing the agent, and use of the agent for stock hydrophobation

Info

Publication number: EP0200755B1
Application number: EP19850905341
Authority: EP
Inventors: Kjell Rune Andersson; Nils Ebbe Lyrmalm
Original assignee: Eka Nobel AB
Current assignee: Nouryon Pulp and Performance Chemicals AB
Priority date: 1984-10-22
Filing date: 1985-10-21
Publication date: 1989-05-24
Also published as: NO166805C; BR8507006A; SE8405260D0; FI862646A; JPH0713358B2; SE8405260L; NO862484L; NO166805B; NO862484D0; CA1339849C; FI80312B; FI862646A0; WO1986002677A1; EP0200755A1; FI80312C; DE3570471D1; JPS63501224A

Abstract

A hydrophobing agent consists of resin acid and/or fatty acid emulsified/dispersed in an aqueous phase of water, a polyaluminium salt dissolved in the water, and preferably also a cationic organic compound. According to the invention, the hydrophobing agent is prepared in that the resin acid and/or fatty acid, optionally in mixture with another hydrophobic melting point-reducing agent, is finely dispersed in the aqueous phase in the presence of said polyaluminium salt and preferably also the cationic organic compound. The invention also comprises the use of the hydrophobing agent for stock hydrophobation of cellulosic fibers in papermaking technology.

Description

The present invention relates generally to a chemical product for use in the sizing of organic cellulosic fibers, especially in papermaking, and above all in stock hydrophobation (sizing) in papermaking. The sizing or hydrophobation of paper is ancient technology which originated in China. When papermaking technology was introduced in Europe, it was found that absorbent paper was less suitable for the pens and inks of that time. As early as in the 14th century, gelatin was therefore added to the paper so as to obtain a hard and dense, non-absorbent paper. After that, the sizing technique using gelatin and starch has gradually been improved.
At the beginning of the 19th century, the discovery of resin size revolutionised sizing technique. In resin sizing, resin is precipitated by means of alum in the fiber suspension prior to sheet formation. The resulting precipitate is cationic and associated to the negatively charged fibers. The aluminium resinate produced by the reaction is highly water-repellent (hydrophobic) and provides a paper product having low-wetting characteristics. Stock sizing using resin size/alum did not change appreciably during the first 150 years. Since then, the resin acid has been modified by causing it to react with, for example, maleic anhydride and fumaric acid (so-called fortified resin size). To make the size water-soluble, the resin acid was saponified with caustic soda and diluted prior to dosage.
The last-mentioned technique was improved during the 1960's and 1970's with the introduction of so-called dispersion size. This technique implies that the resin acid is dispersed to small anionic particles (0.2-0.5 um) in an aqueous solution. The resulting dispersion is stable and is added to the stock and precipitated by means of alum.
Although some progress was made at different times, the resin sizing technique has remained fundamentally the same as the technique used in the 19th century, i.e. two components are required to provide sizing, on the one hand the resin,size and, on the other hand, a precipitation chemical based on an aluminium salt, such as alum.
GB-A1-2,010,352 describes a different stock sizing method in which a resin size which consists of a saponified resin acid, is added to the stock and then precipitated on the fibers by adding a practically sulphate-free aluminium polyhydroxy chloride to the stock mixed with the resin size. The advantage obtained by using this particular precipitant is said to reside in lesser corrosion difficulties as compared with alum as the precipitant. However, the sizing method uses a two-component system in which the conventional precipitant alum has been replaced by another precipitant in the form of a special aluminium salt.
German patent specification 363,668 also indicates a two-component system in which a resin size is precipitated with a neutral or basic aluminium chloride.
In addition to the resin sizing technique, use has been made of a similar sizing technique by means of saponified fatty acids of tall oil (see e.g. Swedish patent 7507128-2, publication No. 416,831). Also in this case, an external precipitant, such as alum, is used.
A great disadvantage of prior art sizing methods is that the hydrophobing effect is drastically reduced when the paper systems are neutral or alkaline. This problem is especially pronounced when one wishes to use calcium carbonate instead of clay as a filler because the calcium carbonate is dissolved at low pH. This shortcoming of conventional sizing technique is due to the fact that cations of aluminium are required to precipitate the negatively charged resin acid/fatty acid. In neutral or alkaline systems, aluminium ions are precipitated in the form of aluminium hydroxide which is in inferior precipitant for resin size since it gives a lower sizing degree. This restriction is especially serious when sizing is carried out in neutral or alkaline stock systems because it is preferred, on grounds of quality and cost, to use calcium carbonate instead of clay as a filler for e.g. fine paper.
In addition to the conventional resin sizing systems, there have also been developed new synthetic sizes which have been gaining ground in papermaking at neutral or alkaline pH. Examples of sizes of this type are alkyl succinic anhydride and alkyl ketene dimer. However, these sizes cost far more than natural sizes, such as resin acids and fatty acids. A further disadvantage of these known synthetic sizes is that it takes more time to achieve the desired sizing effect, as compared with the hardening time for sizes based on resin acid or fatty acid. The longer time required for the synthetic size implies that the paper directly after its manufacture does not possess wholly water-repellent characteristics after the drying section of the papermaking machine.
A longer hardening time is disadvantageous to the surface sizing and/or surface coating of the paper directly after predrying. A low sizing degree (when an alkyl ketene dimer is used) therefore frequently results in excessive rewetting of the paper, which may cause web rupture and production loss. Furthermore, sizing with such neutral sizing systems may lead to a low paper friction and coating difficulties in different parts of the paper machine system. These production problems therefore have been one of the reasons why resin sizing in acid stock systems in which the filler is clay, has remained the dominating hydrophobation technique. Another reason is the far higher price of synthetic sizes as compared with the price of sizes based on resin acid or fatty acid.
British patent specification 1,107,717 proposes a sizing system which comprises an emulsion of paraffin wax as the disperse phase and an aqueous solution of a basic aluminium chloride as the continuous phase, the emulsion being stabilised with nonionic emulsifiers and/or nonionic thickeners. As examples of hydrophobic materials other than paraffin, mention is made of microcrystalline waxes, polyethylene and like waxes, high-molecular fatty alcohols and high-molecular fatty amides, although these have not been specified. However, it has been found that such sizing systems did not give the desired effect, and this applies also to the sizing system indicated by British patent specification 1,274,654 which also is based on a combination of the same substances. A common feature of the sizing system according to these two patent specifications is that the papers sized therewith have shown spots which are a sign of nonuniform size distribution.
US―A―4,333,795 discloses a specific type of one-shot sizing agent, i.e. dispersions containing both colophony material and aluminium. These sizing agent dispersions have been formed on the one hand of what is termed a resin dispersion component and; on the other hand, of conventional aluminium sulphate, i.e. alum. The preparation requires two dispersion sequences, and furthermore the colophony itself must be protected by stabilising agents. In practical use, the technique is used directly in the mills where a dispersion of colophony material is redispersed with alum immediately before addition to the stock.
A further disadvantage of prior art sizing systems is that they have been adapted to be used either in acid stock systems or in neutral and basic stock systems, and this causes difficulties in paper mills wishing to shift from, for example, acid stock systems to neutral or basic systems, because the shift implies a change of several cohering factors, and the shift from one size system to another causes considerable running-in-difficulties. One therefore has need of a sizing system that may be used in both acid and neutral or basic stock systems, whereby the problems associated with the change-over would be reduced considerably.
With reference to GB-A-2 159 183 the applicant has voluntarily submitted separate claims for GB.
It therefore is the main object of this invention to provide a stock hydrophobing agent which eliminates the limitations imposed by conventional technique. A further object of the invention is to provide a hydrophobing agent that may be used as a one-component agent without necessitating separate addition of precipitation chemicals. A still further object of the invention is to provide a method of preparing such a new hydrophobing agent, and still another object of the invention is to provide a sizing system that may be used in both acid and neutral or basic stock systems.
The invention is based on the surprising discovery that it is possible to produce a stable one-component agent that can be used as a sizing agent and requires no external precipitant (in contrast to conventional sizes based on resin acid or fatty acid), if one combines certain polyaluminium salts, one or more resin acids and/or fatty acids, optionally in mixture with a melting point-reducing additive, such as paraffin or other hydrophobic, melting point-reducing agent, and preferably also a cationic organic substance at low pH (below 4). This sizing agent consists of small emulsified (dispersed) and strongly cationised particles that will be directly adsorbed to the negatively charged fibers when dosed to the paper system or applied to other organic fibers.
The hydrophobing agent according to the present invention thus consists of resin acid and/or fatty acid that has been emulsified/dispersed in an aqueous phase of water, a polyaluminium salt dissolved in the water, and preferably also a cationic organic compound. The hydrophobing agent is prepared by finely dispersing the resin acid and/or fatty acid in the aqueous phase in the presence of the polyaluminium salt and preferably also the cationic organic compound. The invention also comprises using this hydrophobing agent for stock hydrophobation of cellulosic fibers in papermaking technology.
One of the advantages of the invention is that the polyaluminium salt and the resin acid and/or fatty acid are combined at low pH (below 4), resulting in a direct activation when the hydrophobing agent is batched to the stock and a precipitate of a compound of aluminium and resin and/or fatty acid is formed when the emulsion droplet enters the pH range 4-6. The invention provides for intimate contact between the resin acid and/or fatty acid and the polyaluminium salt, such that the aluminium hydroxide, in spite of a high pH, has no time to precipitate during papermaking before the active resin acid/fatty acid resinate is formed. A further advantage of the hydrophobing agent according to the invention is that the small emulsified/dispersed particles because of their insignificant size will optimally cover the surface to be hydrophobed.
A major advantage of the invention is that its execution requires no external precipitant, whereby hydrophobation, especially in papermaking technology, is very much simplifed, not only because but one substance need be batched, but also because sizing will be more efficient and uniform since it is easier to optimise the dosing amount using a one-component size according to the invention than using a conventional two-component size.
At present, the greatest advantage, as compared with conventional resin sizes, is deemed to be the high efficiency of the hydrophobing agent according to the invention also at high pH in paper types containing large amounts of calcium carbonate as filler.
Still another advantage of the invention is that the hydrophobing agent is made up of raw materials which are far less expensive than the synthetic sizes now available on the market. Resin and fatty acids are pvailabl.e in practically unlimited quantities. From the technical point of view, the new hydrophobing agent furthermore is superior to synthetic sizes (such as alkyl ketene dimers) for neutral or alkaline paper systems because the hydrophobing agent according to the invention is quick-hardening and thus provides a low-wetting paper already on the paper machine. As a result, the production jams caused by other synthetic sizes are avoided.
Generally, the present invention implies that a polyaluminium slat, a nonsaponified resin acid and/or fatty acid, optionally in mixture with a melting point-reducing additive, such as paraffin, and preferably also a cationic organic substance are mixed in water under intense agitation, whereby an emulsion/dispersion is obtained which consists of small cationic droplets of the order 0.05-50 pm, preferably 0.05-25 pm.
The best effect and the highest stability of the size is obtained if the cationic organic substance is included in the size proper. For some uses, however, it is possible to combine the one-component size (i.e. resin acid/fatty acid and the special polyaluminium salt) with the cationic organic substance only in connection with the application to the organic fibers. In papermaking, the cationic substance may thus be added separately to the stock, either for sizing or for some other purpose, and the sizing method according to the invention may be combined with known papermaking methods in which a cationic organic substance is added to the stock, for instance the methods as disclosed by European patent specification EP-B1-41,056 and European published patent application EP-A1-80,986.
The dispersion/emulsion thus prepared is so stable and highly concentrated, especially if it contains the cationic organic substance, that it can be conveniently distributed to consumers by conventional transport means.
The polyaluminium salts that have proved to be best suited for the purpose of the invention are the basic polyaluminium salts, namely polyaluminium sulphate or polyaluminium chloride. These salts are characterised by a high molar ratio of aluminium to counter-ions (>1) and in that they provide, in aqueous solution, high-charged polyaluminium ions, such as Al₁₃O₄(OH)₂₆(H₂O)₁₀5⁺.
The raw material for the hydrophobing agent according to the invention may comprise pure resin acids, pure fatty acids, or combinations of resin acids and fatty acids, although it is also possible to admix melting point-reducing additives, such as paraffins.
When resin acid is used, a typical resin acid composition is
When fatty acid from tall oil is used, a typical composition is
The invention makes it possible to use a modified resin acid/fatty acid fortified by reactions with substances that are conventional in the context, such as maleic anhydride, fumaric acid etc.
An important feature of the invention is that the resin acids and/or fatty acids are present in the uncharged form (non-saponified form), i.e. a low pH must be maintained, preferably below pH 5. With higher pH, negatively charged carboxylate groups are obtained which detract from the cationic character of the emulsion/dispersion droplets (meaning that the emulsion/dispersion is disrupted).
Suitable amounts of the various components are 0.5-90% resin acid/fatty acid and 10-99.5% water.
A suitable weight ratio of resin acids/fatty acids to aluminium in the dispersion is between 100:1 and 1:4, preferably 10:1 and 1:2.
The cationic organic compound comprised by the aqueous phase may be a surface active agent, starch, guar gum, carboxy methyl cellulose, polyacrylic amide, polyimine, polyamine, polyamide amine, polyethylene imine, or polyacrylate. A suitable weight ratio of resin acids/fatty acids to the cationic organic compound is between 100:0.01 and 100:30.
The invention will be illustrated in more detail below, reference being had to the following Examples.

. Example 1

In this Example, a size emulsion was prepared by mixing 500 g of tall fatty acid (BEVACID 2 from Bergvik Kemi, Soderhamn, Sweden) that had been fortified with 5% fumaric acid, with 2.49 g cationic surface active agent (hexadecyl trimethyl ammonium chloride from Riedel-de Haen AG, Seelze-Hannover, Federal Republic of Germany) and 69.9 g ethanol. The mixture was then intensely stirred (stirrer ULTRA-TURRAX from IKA-Werk, Staufen) and added to a mixture of 5.61 g cationic starch having a nitrogen content of 0.4% (starch S―195 from Raisio-SLR AB, Gothenburg, Sweden), 967.5 g polyaluminium chloride (AI₂(OH)₅Cl.2H₂O from Albright & Wilson, Ltd, London, AI content 25% by weight) in 4454 g water. Upon admixture, both the fatty acid phase and the aqueous phase had a temperature of 25°C.
The mixture was then homogenised in a valve homogeniser (Gualin Lab 60, APV Schroder, Lubeck, Federal Republic of Germany) at an excess pressure of 350 bar. The pH of the resulting emulsion was measured at room temperature and was 3.7. Microscopic examination showed that the size thus prepared had an emulsion droplet size of about 1-2 um.
The resulting emulsion was stable against phase separation for more than two months.

Example 2

25 g of a mixture of 55% tall fatty acid and 45% tall resin acid (special fraction from the distillation plant at Bergvik Kemi AB; the fraction had been fortified with 10% fumaric acid) were added in the same manner as in Example 1 to a mixture of 24 g polyaluminium chloride (same as in Example 1) and 0.063 g cationic polyacrylic amide ("PERCOL" 181 from COM, Vastra Frolunda, Gothenburg) and 250 ml water. Otherwise the same procedure as in Example 1 was followed, and the result was a stable dispersion having a small particle size and a pH of about 2.5.

Example 3

In this Example, a stable dispersion was prepared by adding 1.7 g of unfortified tall resin acid ("BEVIROS SG" from Bergvik Kemi AB, Soderhamn) in 16.7 g of water which contained 0.02 g cationic surface active agent (hexadecyl trimethyl ammonium bromide from Riedelde Haen AG, Seeize-Hannover, Federal Republic of Germany) and 1.6 g polyaluminium chloride (same as in Example 1).
The mixture was transferred to a 100 ml pressure container and heated to 148°C on a hot plate under magnetic agitation. After 30 min, heating was discontinued, and the dispersion was allowed slowly to cool to room temperature. The pH of the resulting product was 2.8.

Example 4

0.13 g cationic surface active agent (dissolved in 3.5 g ethanol) was added to 50 g of a mixture of fatty acid/resin acid (same fraction as in Example 2). The cationic surface active agent was the same as in Example 3.
The fatty acid/resin acid mixture was added to 148 g water containing 48.4 g polyaluminium chloride (same as in the earlier Examples) and 0.25 g cationic starch having a nitrogen content of 0.4%. Otherwise, the procedure was the same as in Examples 1 and 2.
This experiment gave a stable dispersion of pH 2.5 and a viscosity slightly higher than that of the dispersion in the earlier Examples.

Example 5

In this Example, 25 g fatty acid/resin acid (same fraction as in Example 2) were added to 250 ml water containing 0.6 g cationic guar gum (nitrogen content 1.5%, "GENDRIVE 162" from Henkel Company, USA) and 150 g polyaluminium sulphate (the polyaluminium sulphate had been purchased from Boliden Kemi AB, Helsingborg, and contained 15.5% aluminium and 65% sulphate, i.e. a molar ratio of AI:SO₄ = 0.9).
Otherwise, the procedure was the same as in the earlier Examples. The pH of the dispersion was 2.5. The experiment showed that the fatty acid/resin acid could be combined with the other components, such that a dispersion was obtained. However, the stability of the dispersion against phase separation was lower (1 day) than in the earlier Examples.

Example 6

1.25 g cationic starch having a nitrogen content of 0.40% and 4.86 g polyaluminium chloride (see the earlier Examples) were dissolved in 250 g water at 95°C.
25 g tall fatty acid (same as in Example 1) were heated to 95°C and added continuously to the hot aqueous solution while using the procedure-previously described.
The pH of the resulting emulsion was 2.5, and the emulsion contained emulsion droplets of the order 3―4 um. The emulsion proved to be stable against phase separation for 8 days.

Example 7

In this experiment, a stable size emulsion was prepared by adding 25 g of tall oil fatty acid ("BEVACID 2") to 250 g water containing 5.6 g cationic starch having a nitrogen content of 0.40%, and 29.2 g polyaluminium chloride. Otherwise, the same conditions were utilised as in Example 1. The pH of resulting emulsion was 2.8.

Example 8

25 g of a special fraction of fatty acid/resin acid (same product as in Example 2) were added in the manner described in Example 1 to a solution consisting of 58.3 g polyaluminium chloride (same as in Example 1) and 216.7 ml water. Otherwise, the procedure of Example 1 was followed, and a stable emulsion/dispersion of pH 2.8 was obtained.

Example 9

In this Example, 25 g of a mixture of fatty acid/resin acid (same fraction as in Example 2) were added to a solution of 58.3 g polyaluminium chloride (same as in Example 1) and 91.7 g water, used being made of the same procedure as in Example 1. After cooling in a water bath, 125 g of a 1 % solution of cationic starch (nitrogen content 0.40%) were admixed to the product formed as described above. The result was a stable emulsion/dispersion of pH 2.8.

Example 10

A paper stock having the following composition was prepared:

70% fully bleached chemical pulp (60/40 birch sulphate/pine sulphate)
30% calcium carbonate ("Sjöhasten" from Malm6krita)

The birch and pine sulphates were beaten together in a laboratory beater to a beating degree of 200 ml CSF (Canadian Standard Freeness). The calcium carbonate (slurried in water) was added, and the stock was diluted to 0.5% dry content. The pH of the stock was 8.0.
In this experiment, different amounts of the size according to Example 1 were dosed to different batches of the stock.
The sizes were dosed in the form of 1 % solutions added to the 0.5% stock under agitation (45 s). The stock was then transferred to a laboratory sheet mould (Finnish mould) with a 100 mesh wire. Sheet formation was carried out according to SCAN C 26:27 (basis weight 73 g/m²). The sheets were dried at 23°C and 50% relative air humidity overnight, whereupon the sheets were placed in a heating cabinet (30 min) at 120°C.
After conditioning (23°C, 50% relative air humidity) the water absorbency was determined according to SCAN P 12:64 (Cobb_so).
Table 1 shows the results of the evaluation. The dosed amounts of the sizes (% by weight) refer to the amount added, (active content), based on dry stock. Table 1 shows that the size according to the invention, in spite of a high pH and high amounts of calcium carbonate, has adequate sizing capacity.

Example 11

A paper stock was prepared in the same manner as in Example 10. The resulting stock had a pH of 7.3. Different sizes according to the present invention were added to the stock.
The paper sheets were formed and dried in the manner stated in Example 8. Water absorbency according to Cobb₆₀ (SCAN P 12:64) was determined. The results are shown in Table 2.

Example 12

In this experiment, use was made of a paper stock from a magazine paper mill. The pulp concentration of the stock was 3%, and the pulp had been beaten to a beating degree of 125 CSF. The composition of the pulp employed was

22% fully-bleached chemical pulp
15% TMP (thermomechanical pulp)
35% groundwood pulp
28% broke
30% kaolin (C clay from ECC), calculated on dry fiber, was added to the stock which was diluted to a concentration of 0.5%. pH was adjusted to 5.0.

Size prepared in accordance with Exmaple 3 was dosed in different amounts to the suspension of fibers and fillers. Sheets were manufactured according to SCAN 26:67 (basic weight 73 g/m²).
In this experiment, the sheets were dried on a drying cylinder at 85°C and then placed in an oven (120°C)for 30 min.
After conditioning (23°C, 50% relative air humidity) the water absorbency according to Cobb₆₀ was measured. The results of these measurements are indicated in Table 3.

Example 13

In this experiment, use was made of a paper pulp having a dry content of 1.37% and a beating degree of 200 ml CSF. The pulp consisted of 60% birch sulphate pulp and 40% pine sulphate pulp.
30% calcium carbonate (Malmökrita "SJ6HASTEN"), based on dry fiber, were added to the pulp, whereupon pH was adjusted to 8.5. A size prepared in accordance with Example 1 was added in different quantities to the stock. Sheets were then formed according to SCAN C 26:67 and with basis weights of 73 g/ m². The sheets were dried and evaluated in accordance with Example 10. The sizing effect was excellent. The sizing results are indicated in Table 4.

Example 14

In this experiment, use was made of the same paper stock and the same procedure as in Example 10. However, the hydrophobing agent was a size according to Example 8, which was dosed in different quantities, 0.6% cationic starch (based on dry stock) being added 15 s after size dosing to serve as an external retention agent. The results of these experiments are shown in Table 5, and it appears that the size according to ExampJe 8 gave an improvement also in the absence of cationic substance, but that the improvement was more pronounced when the cationic substance had been added.

^. Example 15

In the experiments according to this Example, use was made of a paper stock prepared in accordance with the procedure stated in Example 10. Sizing was carried out by the same procedure as in Example 10, but in the present Example use was made instead of a size prepared in accordance with Example 9. Adequate sizing was obtained also in this experiment, the result of which is shown in Table 6.

Example 16

The hydrophobing substance used in this Example was a mixture of 42 g tall oil rosin (BEVIROS SG from Bergvik Kemi) and 18 g paraffin wax (melting point 58°C, from Malmsten & Bergvall, Gothenburg). This hydrophobing substance was added under very intense agitation (ULTRA TURRAX from IKA-Werk, Staufen) to a mixture consisting of 3 g cationic starch having a nitrogen content of 0.4%, 144.7 g polyaluminium chloride solution (KLORHYDROL from Reheis Chemical Ltd, Dublin, AI content 12.5% by weight) and 92.3 g water. The emulsification temperature was 95°C for all of the chemicals included.
The emulsion was homogenised for a further 3 min at 10,000 rpm, whereupon it was cooled in a water bath to room temperature.
The pH of the product thus prepared was 3.7, and the particle size was about 1-2 µm, The stability was excellent for more than two months.
To test the size thus prepared, a paper stock of the following compositions was prepared:

80% fully bleached chemical pulp (60/40 birch sulphate-pine sulphate)
20% calcium carbonate ("Sjohasten" from Malmökrita).

The birch and pine sulphates were beaten together in a laboratory beater to a beating degree of 200 ml CSF (Canadian Standard Freeness). The calcium carbonate slurried in water) added, and the stock was diluted to 0.5% dry content. The pH of the stock was 8.0.
The sizes were dosed in the form of a 1 % solution and added to the 0.5% stock under agitation (45 s), whereupon the stock was transferred to a laboratory sheet mould (Finnish mould) having a 100 mesh wire. Sheet formation was carried out according to SCAN C 26:67 (basis weight 73 g(m²). The sheets were dried at 23°C and 50% relative air humidity overnight, whereupon they were placed in a heating cabinet (30 min) at 120°C.
After conditioning (23°C, 50% relative air humidity) the water absorbency according to SCAN P 12:64 (Cobb_so) was measured.
Table 7 indicates the results of the evaluation. The dosed amounts of size (% by weight) refer to the amount added (active content), based on dry stock. Table 1 indicates that the size according to the invention, in spite of a high pH and high amounts of calcium carbonate, has adequate sizing capacity (Cobb_so<25).

Example 17

Example 16 was repeated with the same constituents, but with the following amounts of the different constituents in the size emulsion:

48 g tall oil rosin
12 g paraffin wax
144.7 g polyaluminium chloride solution
3 g cationic starch
92.2 g water

The resulting emulsion had a pH of 3.7, a particle size of about 1-2 µm, and excellent stability for more than two months.
The emulsion was then used for sizing the same paper stock as in Example 16, and the results of this experiment are shown in Table 8.

Claims

1. A hydrophobing agent consisting of an emulsion/dispersion of a finely dispersed material in an aqueous phase, characterised in that the finely dispersed material consists of a resin acid and/or fatty acid, and in that the aqueous phase contains an aluminium salt which is a polyaluminium chloride or a polyaluminium sulphate.

2. An agent as claimed in claim 1, characterised in that the finely dispersed material is a nonsaponified, preferably fortified resin acid.

3. An agent as claimed in claim 1, characterised in that the aluminium salt is a polyaluminium chloride.

4. An agent as claimed in claim 1 or 3, characterised in that the molar ratio of aluminium to counter ion in the polyaluminium compound is above 1:1.

5. An agent as claimed in claim 1, characterised in that it also contains a cationic organic compound.

6. An agent as claimed in claim 5, characterised in that the cationic organic compound is a cationic starch, cationic guar gum, cationic polyacrylic amide, polyamine, polyamide amine, or polyethylene imine.

7. An agent as claimed in any one of the preceding claims, characterised in that it contains from 30-700 g/l resin acid and/or fatty acid, from 1 to 200 g/I polyaluminium compound, calculated as aluminium, and preferably also from 0.05 to 200 g/I cationic organic compound.

8. A method of preparing a hydrophobing agent, characterised in that an aqueous solution of an aluminium salt which is a polyaluminium chloride or a polyaluminium sulphate is formed and preferably is also caused to contain a cationic organic compound, and that resin acid and/or fatty acid are then emulsified/dispersed as a finely dispersed phase in said aqueous solution.

9. A method as claimed in claim 8, characterised in that the material dispersed as a finely dispersed phase, is nonsaponified, preferably fortified resin acid.

10. A method as claimed in claim 8, characterised in that the aluminium salt is a polyaluminium chloride.

11. A method as claimed in claim 8 or 10, characterised in that the molar ratio of aluminium to counter ion in the aluminium salt is above 1:1.

12. A method as claimed in claim 8, characterised in that the cationic organic compound is cationic starch, cationic guar gum, cationic polyacrylic amide, polyamine, polyamide amine, or polyethylene imine.

13. A method as claimed in any one of claims 8-12, characterised in that the dispersion/emulsion is caused to contain from 30 to 700 g/I resin acid and/or fatty acid, from 1 to 200 g/I polyaluminium compound, calculated as aluminium, and preferably also from 0.05 to 200 g/I cationic organic compound.

14. Use of a hydrophobing agent as-claimed in any one of claims 1-7, for stock hydrophobation in papermaking technology.