EP0200755A1

EP0200755A1 - Hydrophobing agent for cellulosic fibers, method of preparing the agent, and use of the agent for stock hydrophobation.

Info

Publication number: EP0200755A1
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: 1986-11-12
Also published as: FI80312B; DE3570471D1; SE8405260L; FI862646A0; EP0200755B1; FI862646A; SE8405260D0; BR8507006A; JPH0713358B2; JPS63501224A; NO862484L; NO166805B; FI80312C; CA1339849C; NO166805C; WO1986002677A1; NO862484D0

Abstract

Un agent à pouvoir hydrophobe est constitué, selon l'invention, d'un acide de résine et/ou d'un acide gras émulsifié/dispersé en phase aqueuse, d'un sel de polyaluminium dissous dans l'eau, et de préférence d'un composé organique cationique. Pour la préparation de cet agent, l'acide de résine et/ou l'acide gras, éventuellement en mélange avec un autre agent hydrophobe réducteur du point de fusion, est finement dispersé en phase aqueuse en présence dudit sel de polyaluminium et de préférence également du composé organique cationique. L'invention comporte également l'emploi de l'agent à pouvoir hydrophobe pour rendre hydrophobe la pâte des fibres cellulosiques dans la technologie papetière.An agent with hydrophobic power consists, according to the invention, of a resin acid and / or of an emulsified / dispersed fatty acid in aqueous phase, of a polyaluminium salt dissolved in water, and preferably of 'a cationic organic compound. For the preparation of this agent, the resin acid and / or the fatty acid, optionally in admixture with another hydrophobic agent reducing the melting point, is finely dispersed in the aqueous phase in the presence of said polyaluminum salt and preferably also of the cationic organic compound. The invention also includes the use of the hydrophobic agent to make the pulp of cellulosic fibers hydrophobic in paper technology.

Description

HYDROPHOBING AGENT FOR CELLULOSIC FIBERS, METHOD OF PREPARING THE AGENT, AND USE OF THE AGENT FOR STOCK

HYDROPHOBATION

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 paper- making. 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 disco- very of resin size revolutionised sizing technique. In resin sizing, resin is precipitated by means of alum in the fiber suspension prior to sheet forma¬ tion. The resulting precipitate is cationic and asso¬ ciated to the negatively charged fibers. The aluminium resinate produced by the reaction is highly water-re¬ pellent (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 _*

2 acid is dispersed to small anionic particles (0.2-0.5 μm) 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 funda¬ mentally 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 alumi¬ nium salt, such as alum.

GB-Al-2,010,352 describes a different stock sizing method in which a resin size which consists of a saponi¬ fied resin acid, is added to the stock and then pre- cipitated on the fibers by adding a practically sul¬ phate-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 preci¬ pitant in the form of a special aluminium salt.

German patent specification 363,668 also indi- cates 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 re- quired to precipitate the negatively charged resin acid/fatty acid. In neutral or alkaline systems, alumi¬ nium ions are precipitated in the form of aluminium hydroxide which is an inferior precipitant for resin size since it gives a lower sizing degree. This re- striction 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 cal¬ cium 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 dirtier. 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 diffe¬ rent 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 specifi- cation 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. 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 con¬ siderably. _*

5 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 preci¬ pitation 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 com¬ bines 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 paper¬ making 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 simplified, 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 conven¬ tional 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 con¬ taining 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 available 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 syn¬ thetic sizes are avoided.

Generally, the present invention implies that a polyaluminium salt, 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 μm, preferably 0.05-25 μm.

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-Al-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 conveni¬ ently 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, such as polyaluminium sul¬ phate or polyaluminium chloride. These salts are cha¬ racterised by a high molar ratio of aluminium to coun¬ ter-ions (>1) and in that they provide, in aqueous solution, high-charged polyaluminium ions, such as Al₁₃O₄(OH)₂₆(H₂O)₁₀ ⁵⁺.

The raw material for the hydrophobing agent accord¬ ing 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 abietic acid: 40% neoabietic acid: 4% pimaric acid: 3% isopimaric acid: 6% palustric acid: 7% other acids: 40% When fatty acid from tall oil is used, a typical composition is σleic acid: 30% linoleic acid: 65% other acids: 5% 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 (nonsaponified 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, Sδderhamn, Sweden) that had been forti¬ fied with 5% fumaric acid, with 2.49 g cationic sur- • face active agent (hexadecyl trimethyl ammonium chlo¬ ride 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 (Al₂(0H)₅C1.2H-0 from Albright & Wilson, Ltd, London, Al content 25% by weight) in 4454 g water. Upon admixture, both the fatty acid phase and the aqueous phase had a tempera¬ ture of 25°C. The mixture was then homogenised in a valve homo- geniser (Gualin Lab 60, APV Schroder, Lϋbeck, 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 examina- tion showed that the size thus prepared had an emulsion droplet size of about 1-2 μm.

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 di- stillation 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 Frδlunda, Gothenburg) and 250 ml water. Otherwise the same procedure as in Example 1 was followed, and the result was a stable disper¬ sion 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 ( "BE- VIROS SG" from Bergvik Kemi AB, Sδderhamn) to 16.7 g of water which contained 0.02 g cationic surface active agent (hexadecyl trimethyl ammonium bromide from Riedel- de Haen AG, Seelze-Hannover, Federal Republic of Ger¬ many) 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 dis¬ continued, 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 sul¬ phate had been purchased from Boliden Kemi AB, Helsing- borg, and contained 15.5% aluminium and 65% sulphate, i.e. a molar ratio of Al:SO, = 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 stabi¬ lity 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 μm. 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 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 con- sisting of 58.3 g polyaluminium chloride (same as in Example 1) and 216.7 ml water. Otherwise, the pro¬ cedure 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/re¬ sin 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 ( "Sjδhasten" from Malmδkrita) 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 dilu¬ ted to 0.5% dry content. The pH of the stock was 8.0. ^1Ώ- this experiment, different amounts of on the one hand the size according to Example 1 and, on the other hand, of a conventional resin size ("T-lim 7635" from Hercules AB, Gothenburg) were dosed to different batches of the stock.

In the experiments with the conventional resin size, 2% alum (based on dry pulp) were added in con¬ ventional manner prior to size dosing. 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/m ) . 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 humi¬ dity) the water absorbency was determined according to SCAN P 12:64 (Cobb_6Q).

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.

TABLE 1

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 Cobbg₀ (SCAN P 12:64) was determined. The results are shown in Table 2.

TABLE 2

2 Water absorbency according to Cobbg_Q (g/m )

EXAMPLE 12

In this experiment, use was made of a paper stock from a_pmagazine 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 concen¬ tration of 0.5%. pH was adjusted to 5.0.

Size prepared in accordance with Example 3 was dosed in different amounts to the suspension of fibers and fillers. Sheets were manufactured according to SCAN 26:67 (basis 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 hu¬ midity) the water absorbency according to Cobb_gQ was measured. The results of these measurements are indi¬ cated in Table 3. 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 (Malmδkrita "SJOHASTEN" ) , 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

2 C 26:67 and with basis weights of 73 g/m . The sheets were dried and evaluated in accordance with Example

10. The sizing effect was excellent. The sizing results are indicated in Table 4.

TABLE 4

2 Water absorbency according to Cobb_g0 (g/m )

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 reten¬ tion agent. The results of these experiments are shown in Table 5, and it appears that the size according to Example 1 gave an improvement also in the absence of cationic substance, but that the improvement was more pronounced when the cationic substance had been added.

TABLE 5 Water absorbency according to Cobb_fiQ

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. TABLE 6

Water absorbency according to Cobb_fi.

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, Al 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 ("Sjδhasten" from Malmδ- krita) .

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

2 C 26:67 (basis weight 73 g(m ). The sheets were dried at 23°C and 50% relative air humidity overnight, where¬ upon they were placed in a heating cabinet (30 in) at 120°C.

After conditioning (23°C, 50% relative air humi¬ dity) the water absorbency according to SCAN P 12:64 (Cobb_fif.) 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 in- vention, in spite of a high pH and high amounts of calcium carbonate, has adequate sizing capacity

(Cobbg₀<25)

TABLE 7

EXAMPLE 17 Example 16 was repeated with the same consti¬ tuents, but with the following amounts of the diffe¬ rent 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.

TABLE 8

Claims

1. A hydrophobing agent consisting of an emul¬ sion/dispersion of a finely dispersed material in an aqueous phase, c h a r a c t e r i s e d in that said aqueous phase comprises an aqueous solution of a polyaluminium salt in which the molar ratio of alu¬ minium to counter-ion in the polyaluminium salt is above 1:1, and preferably contains a cationic organic compound, and that the finely dispersed material con- , sists of resin acid and/or fatty acid, optionally in mixture with another hydrophobic melting point-re¬ ducing agent.

2. An agent as claimed in claim 1, c h a r a c ¬ t e r i s e d in that it contains 5-900 g/1, preferably 30-700 g/1, resin acid and/or fatty acid, 0.05-450 g/1, preferably 1-200 g/1 aluminium from polyaluminium salt, and preferably also 0.05-200 g/1, and even more preferably 0.3-100 g/1'cationic organic compound.

3. An agent as claimed in claim 1 or 2, c h a ¬ r a c t e r i s e d in that the gegenion in the poly- aluminium salt is chloride, bromide, sulphate or ace¬ tate, preferably chloride or sulphate.

4. An agent as claimed in claim 1, 2 or 3, c h a ¬ r a c t e r i s e d in that the cationic organic compound is a surface active agent, starch, guar gum, earboxy methyl cellulose, polyacrylic amide, polyimine, polyamine, polyamide amine, polyethylene imine, or polyacrylate.

5. An agent as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the emulsion/disper- sion has a pH of below 5, preferably below 4.

6. An agent as claimed in any one of claims 1-5, c h a r a c t e r i s e d in that the resin acid and/or fatty acid has been modified by reaction with maleic anhydride or fumaric acid.

7. An agent as claimed in any one of claims 1-6, c h a r a c t e r i s e d in that the resin acid and/or ^'fatty acid is present in nonsaponified form.

8. A method of preparing a hydrophobing agent, c h a r a c t e r i s e d in that an aqueous solu¬ tion of a polyaluminium salt in which the molar ratio of aluminium to counter-ion in the polyaluminium salt is above 1:1, is formed and preferably is also caused to contain a cationic organic compound, and that resin acid and/or fatty acid, optionally in mixture with another hydrophobic melting point-reducing agent, are then emulsified/dispersed as a finely dispersed phase in said aqueous solution.

9. A method as claimed in claim 8, c h a r a c - t e r i s e d in that the dispersion/emulsion is caused to contain 5-900 g/1, preferably 30-700 g/1, resin acid and/or fatty acid, 0.05-450 g/1, prefe¬ rably 1-200 g/1, aluminium from the polyaluminium salt, and^* preferably 0.05-200 g/1, even more preferably 0.3-100 g/1, cationic organic compound.

10. A method as claimed in claim 8 or 9, c h a ¬ r a c t e r i s e d in that the counter-ion in the polyaluminium salt is chloride, bromide, sulphate or acetate, preferably chloride or sulphate.

11. A method as claimed in any one of claims 8-10, c h a r a c t e r i s e d in that the cationic or¬ ganic compound is a surface active agent, starch, guar gum, earboxy methyl cellulose, polyacrylic amide, polyimine, polyamine, polyamide amine, polyethylene imine, or polyacrylate.

12. A method as claimed in any one of claims 8-11, c h a r a c t e r i s e d in that the pH of the emul¬ sion/dispersion is adjusted to below pH 5, preferably to below pH 4.

13. A method as claimed in any one of claims 8-12, c h a r a c t e r i s e d in that the resin acid and/or fatty acid is fortified by reaction with maleic v

22 anhydride or fumaric acid.

14. A method as claimed in any one of claims 8-13, c h a r a c t e r i s e d in that the resin acid and/or fatty acid is added in nonsaponified form.

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