CA1339849C

CA1339849C - Hydrophobing agent for cellulosic fibres, method of preparing the agent,and use of the agent for stock hydrophobation

Info

Publication number: CA1339849C
Application number: CA000493477A
Authority: CA
Inventors: Kjell Rune Andersson; Nils Ebbe Lyrmalm
Original assignee: Eka AB
Current assignee: Nouryon Pulp and Performance Chemicals AB
Priority date: 1984-10-22
Filing date: 1985-10-21
Publication date: 1998-05-05
Anticipated expiration: 2015-05-05
Also published as: NO862484D0; FI862646L; JPH0713358B2; EP0200755B1; SE8405260D0; WO1986002677A1; FI80312C; DE3570471D1; EP0200755A1; FI80312B; NO166805B; JPS63501224A; NO862484L; BR8507006A; FI862646A0; SE8405260L; NO166805C

Abstract

A hydrophobing agent consists according to the invention 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 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 relates to the use of the hydrophobing agent for stock hydrophobation of cellulosic fibres in papermaking.

Description

13~8~9 The present invention generally relates to a chemical product for use in sizing organic cellulosic fibres, especially in papermaking and in particular in stock hydrophobation (sizing) during the papermaking process. Sizing or hydrophobation of paper is an old technique which derives from China. When the paper-making technique came to Europe, it was found that absorbent paper was less suitable for the pens and ink used at the time. As early as the fourteenth cen-tury, gelatin was therefore added to the paper to obtain a hard, tight, non-absorbent paper. The sizing technique using gelatin and starch has thereafter been gradually improved.
At the beginning of the nineteenth century, the sizing technique was dramatically improved by the discovery of rosin size. In rosin sizing, the rosin is precipitated by means of alum in the fibre suspension prior to sheet formation. The resulting precipitate is cationic and associated to the negatively charged fibres. The aluminium resinate formed in the reaction is very water-repellent (hydrophobic) and yields a low-wetting paper product. The stock sizing technique using rosin size/alum remained relatively unaltered over the first 150 years. Later, the resin acid has been modified by reacting it with e.g. maleic anhydride and fumaric acid (so-called fortified rosin size).
In order that the size should be water-soluble, the resin acid was saponified with soda lye and diluted before addition.

1~3~4;3 An improvement of the last-mentioned technique was made in the 1960's and 1970's by the use of so-called dispersion size. This technique means that the resin acid is dispersed to small anionic particles (0.2-0.5 ~m) in an aqueous solution. The resulting dispersion is stable and is added to the stock and precipitated by means of alum.
Despite a certain further development during different periods, the rosin sizing technique has however remained basically the same as it was in the nineteenth century, i.e. two components are required for providing sizing, namely the rosin size and a chemical precipitant based on an aluminium salt, such as alum.
GB-Al-2,010,352 discloses another stock sizing method in which a rosin size consisting of a saponi-fied resin acid is added to the stock and thereafter precipited on the fibres by admixing a practically sulphate-free aluminium polyhydroxy chloride with the stock containing the rosin size. According to this British publication, the major advantage of using this particular precipitant instead of alum is the alleviation of corrosion problems. However, this known sizing process makes use OL a two-component system in which the conventional precipitant alum has been replaced by another precipitant in the form of a spe-cial aluminium salt.
German patent specification 363,668 also discloses a two-component system, in which a rosin sizing agent ~ 33~8~9 is precipitated with a neutral or basic aluminium chloride.
In addition to the rosin sizing technique, use has been made of a similar sizing technique based on saponified fatty acids of tall oil (see e.g. SE
Patent 7507128-2, Publ. No. 416,831) which are also precipitated by means of an external precipitant, such as alum.
A major drawback of the prior art sizing methods is that the hydrophobing effect drops dramatically in the case of neutral or alkaline paper systems.
This is an especially great problem when calcium car-bonate should be used instead of clay as filler, since calcium carbonate is dissolved at low pH. This defi-ciency of conventional sizing is due to the fact that cations of aluminium are required for precipitating the negatively charged resin acid/fatty acid. In neutral or alkaline systems, aluminium ions precipitate in the form of aluminium hydroxide which is a poor precipi-tant for rosin size, which in this case results in a low sizing degree. This limitation is a particular-ly serious problem in connection with sizing in neutral or alkaline stock systems, since it is preferred, in respect of both quality and economy, to use calcium carbonate instead of clay as filler for e.g. fine paper.
In addition to the conventional rosin sizing systems, new synthetic sizes have also been developed ~3~843 which have gained ground in papermaking at neutral or alkaline pH. Examples of sizing agents of this type are alkyl succinic anhydride and alkyl ketene dimer. These sizes are however considerably more ex-pensive than natural sizing agents, such as resin acids and fatty acids. Another drawback of these known synthetic sizes is that they require an extended time for producing the desired sizing effect as compared with the setting time for resin acid-based or fatty acid-based sizes. The prolonged time for the synthe-tic size means that the paper immediately after form-ing will not have completely water-repellent proper-ties after the drying section of the papermaking machine.
An extended setting time implies drawbacks in connection with surface sizing and/or surface coating of the paper directly after predrying. A low sizing degree (when using alkyl ketene dimer sizing) therefore often entails excessive rewetting of the paper, which may cause web rupture and reduced productivity. Moreover, sizing with such neutral sizing systems may entail low paper friction and problems with deposits on dif-ferent parts of the papermaking machine system. These production problems have therefore been one of the reasons why rosin sizing in acid stock systems contain-ing clay as filler still is the predominant hydrophobing technique. Another reason is the substantially higher price of synthetic sizes as compared with the price of resin acid- or fatty acid-based sizes.

8 ~ ~

British patent specification 1,107,717 also dis-closes sizing systems comprising an emulsion of paraf-fin wax as dispersed phase and an aqueous solution of a basic aluminium chloride as continuous phase, the emulsion being stabilized with non-ionic emulsi-fying agents and/or non-ionic thickening agents. As examples of other hydrophobic materials than paraffin, mention is made, but no specific examples given, of microcrystalline waxes, polyethylene and related waxes, high molecular weight fatty alcohols and high molecular weight fatty amides. It has however been found that such sizing systems do not produce the aimed-at effect.
The same applies to the sizing system disclosed in British patent specification 1,274,654, which is also based on a combination of the same substances. Common to the sizing systems according to these two patent specifications is that the papers sized by means of these systems are spotty, which is indicative of uneven distribution of the sizing agent.
Another drawback of known sizing systems is that they are adapted for use either in acid stock systems or in neutral or basic stock systems. This means dif-ficulties for paper mills desiring to switch from e.g. acid stock systems to neutral or basic ones.
Such switch-over in fact means changing several cor-related factors, where the change-over from one sizing system to another entails considerable initial pro-duction problems. Thus, there is a need for a sizing ~t 339~43 system which can be used in both acid and neutral or basic stock systems, since the switch-over problems would then be substantially reduced.
A primary object of the present invention therefore is to provide a stock hydrophobing agent which overcomes the limitations from which conventional techniques suffer. Another object of the invention is to provide a hydrophobing agent which can be used as a single-component agent without the need of separately adding chemical precipitants. Yet another object of the inven-tion is to provide a method of preparing such a novel hydrophobing agent. A further object of the invention is to provide a sizing system which can be used in both acid, neutral and basic sizing systems.
The invention is based on the unexpected discovery that it is possible to obtain a stable single-component agent which is usable as sizing agent and which does not require an external precipitant (as opposed to conventional resin-based or fatty acid-based sizes), by combining certain polyaluminium salts, one or more resin acids and/or fatty acids, optionally in admixture with a melting point lowering additive, such as paraf-fin, or other hydrophobic melting point lowering agent, and preferably also a cationic organic substance at low pH (below 4). This sizing agent consists of small emulsified (dispersed), strongly cationized particles which will be directly adsorbed on the negatively charged fibres when supplied to the paper system or when applied to other organic fibres.

~ ~3~8~

The hydrophobing agent according to the invention thus consists of resin acid and/or fatty acid which 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 relates to the use of this hydrophobing agent for stock hydrophobation of cellulosic fibres in paper-making.
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), a direct acti-vation occurring when the hydrophobing agent is charged to the stock and a precipitate of a compound of alumi-nium and resin acid and/or fatty acid is formed when the emulsion droplet enters into 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, despite high pH in the papermaking process, will not have time to precipitate before the formation of the active resin acid/fatty acid resinate. Another advantage of the hydrophobing agent according to the invention is that the small emulsified/dispersed particles, by their small size, will optimally cover the surface to be hydrophobated.

~ ~3~49 A very substantial advantage of the invention is that no external precipitant is needed. This means a considerable simplification for anyone who wishes to perform hydrophobation, especially in papermaking, not only because only one substance need be charged but also because more reliable and uniform sizing is obtained, since it is easier to optimize the amount to be supplied when using a single-component size according to the invention as compared with conventional two-component sizes.
At present, the greatest advantage, as compared with conventional rosin sizes, is considered to be that the hydrophobing agent according to the invention is very effective also at high pH values in such types of paper as contain large amounts of calcium carbonate as filler.
Another advantage of the invention is that the hydrophobing agent consists of considerably less costly raw materials than the commercially available synthetic sizing agents. Resin acids and fatty acids are available in practically unlimited quantities. From the technical point of view, the novel hydrophobing agent is also superior to synthetic sizing agents (e.g. alkyl ketene dimers) for neutral or alkaline paper systems since the hydrophobing agent according to the invention is quick-setting and, hence, gives a low-wetting paper already on the papermaking machine. Thus, the distur-bances in production entailed by the use of other synthetic sizing agents will not occur.

~ 33~8~3 Generally speaking, the invention resides in that a polyaluminium salt, a non-saponified resin acid and/or fatty acid, optionally in admixture with a melting point lowering additive, such as paraffin, and preferably also a cationic organic substance are mixed in water under vigorous agitation, thus yielding an emulsion/dispersion which consists of small cationic droplets in the order of size of 0.05-50 ~m, most preferably 0.05-25 ~m.
Optimum effect and stability of the size is ob-tained if the cationic organic substance is included in the size itself. In certain applications, it is however possible to add the single-component size (i.e. resin acid/fatty acid and the particular poly-aluminium salt) to the cationic organic substance only in connection with the application to the organic fibres. In papermaking, the cationic substance may thus be separately added to the paper stock either for the purpose of sizing or for any other purpose.
Thus, the sizing method according to the invention can be combined with known papermaking processes where a cationic organic substance is added to the stock, for instance the processes according to European pa-tent specification EP-Bl-41,056 and European published patent application EP-Al-80,986.
The thus prepared dispersion/emulsion, especially if it contains the cationic organic substance, is so stable and highly concentrated that it can most advantageously be delivered to the user in conventional means of transportation.

~ ~s~9~ i~

The polyaluminium salts which have been found the most useful for achieving the object of the inven-tion are basic polyaluminium salts such as polyaluminium sulphate or polyaluminium chloride. These salts are distinguished by a high molar ratio of aluminium to gegenion (>1) and by yielding in aqueous solution polyaluminium ions having high charge, such as e.g.

A11304(0H)26(H20)10 The raw material for the hydrophobing agent accord-ing to the invention may be pure resin acids, pure fatty acids or combinations of resin acids or fatty acids, but it is also possible to admix melting point lowering addi-tives, such as paraffins.
When resin acid is used, a typical resin acid composition is as follows:
abietic acid 40%
neoabietic acid 4%
pimaric acid 3%
isopimaric acid 6%
palustric acid 7%
balance 40%
When fatty acid is used and derives from tall oil, the following composition is customary:
oleic acid 30%
linolenic acid 65%
other acids 5%.
In the invention it is possible to use a modified resin acid which has been fortified by reactions with 3~ 13 substances commonly used in this context, such as maleic anhydride, fumaric acid etc.
In the invention, it is important that the resin acids and/or fatty acids used are in uncharged form (non-saponified form), i.e. that pH should be kept low, preferably below 5. At higher pH values, negatively charged carboxylate groups are obtained, reducing the cationic character of the emulsion/dispersion droplets (the emulsion/dispersion being broken).
Suitable amounts of the different components are 0.5-90% resin acid/fatty acid and 10-99.5% water.
A suitable weight ratio of resin acids/fatty acids to aliminium in the dispersion is between 100:1 and 1:4, preferably 10:1 and 10:2.
The cationic organic compound included in the aqueous phase may be a tenside, starch, guar gum, carboxymethylcellulose, polyacrylamide, 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 hereinbelow in a number of Examples.

In this Example, a size emulsion was prepared by mixing 500 g tall oil fatty acid (BEVACID 2 from Bergvik Kemi, Soderhamn, Sweden) fortified with 5%
fumaric acid, with 2.49 g cationic tenside (hexadecyl-trimethylammonium chloride from Riedel-de Haén AG, * a Trade Mark 12 ~3 ~3~s~3 Seelze-Hannover, West Germany) and 69.9 g ethanol.
This mixture was thereafter added under vigorous agi-tation (agitator ULTRA-TURRAX from IKA-Werk, Stuten) to a mixture consisting 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 polyalumi-niu~ chl~ride ~A12(OH)5Cl.2H20 from Albright & Wilson, Ltd., London, Al-content 25% by weight] in 4454 g water. In the mixing process, the temperature was 25~C for both the fatty acid phase and the aqueous phase.
The mixture was thereafter homogenized in a valve homogenizer (Gualin Lab. 60, APV Schroder, Lubeck, West Germany) at 350 bar gauge pressure. The pH of the resulting emulsion was measured at room tempera-ture and was 3.7. In microscope, it was found that the prepared sizing agent had an emulsion droplet size of about 1-2 ~m.
The resulting emulsion was stable to phase sepa-ration for more than two months.

25 q of a mixture of 55% tall oil fatty acid and 45% tall oil resin acid (special fraction from distilling plant at Bergvik Kemi AB - the fraction was fortified with I0% fumaric acid) was added in the same way as in Example 1 to a mixture of 24 g polyaluminium chloride (same as in Example 1) and 0.063 g cationic polyacrylamide ("PERCOL" 181 from COM, Vastra Frolunda, Gothenburg) and 250 ml water.

* a Trade Mark 13 ~ -- 3 33~9 ~ , .

Otherwise, the preparation was performed in the same manner as in Example 1, and the result was a stable dispersion of small particle size and a pH of about 2.5.

In this Example, a stable dispersion was prepared by adding 1.7 g unfortified tall oil resin acid ("BEVIROS
SG" from Bergvik Kemi AB, Soderhamn) to 16.7 g water containing 0.02 g cationic tenside (hexadecyltrimethyl-ammonium bromide from Riedel-de Haén AG, Seelze-Hannover, West Germany) and 1.6 g polyaluminium chloride (same as in Example 1).
The mixture was transferred to a 100 ml pressure vessel and heated to 148~C on a heating plate under magnetic agitation. After 30 minutes, heating was interrupted and the dispersion was allowed to cool slowly to room temperature. The pH of the resulting product was 2.8.

To 50 g of a mixture of fatty acid/resin acid (same fraction as used in Example 2) was added 0.13 g cationic tenside (dissolved in 3.5 g ethanol). The cationic tenside 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 previous Examples) and 0.25 g cationic starch having a nitrogen content of 0.4%. Otherwise, the method of preparation was the same as in Examples 1 and 2.

~ * a Trade Mark ~ ~ "~ 14 . j~ 5.
.~ ~

-- ~ 3 ~33~ll3 This experiment yielded a stable dispersion having a pH of 2.5 and a slightly higher viscosity than the dispersion in the previous Examples.

In this Example, 25 g fatty acid/resin acid (same fraction as in Example 2) was 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 obtained from Boliden Kemi AB, Helsingborg, Sweden, and contained 15.5% aluminium and 65% sulphate, i.e. the molar ratio of Al to SO4 was 0.9).
In other respects, the method of preparation was the same as in the previous Examples. The pH of the dispersion was 2.5. This experiment showed that the fatty acid/resin acid could be combined with the other components, i.e. so as to obtain a dispersion.
The stability of the dispersion to phase separation was however lower (24 hours) than in the previous Examples.

1.25 g cationic starch having a nitrogen content of 0.40% and 4.86 g polyaluminium chloride (see pre-vious Examples) was dissolved in 250 g water at 95~C.
25 g tall oil fatty acid (same as in Example 1) was heated to 95~C and continuously added to the hot aqueous solution, using the above-mentioned technique.
The resulting emulsion had a pH of 2.5 and con-tained emulsion droplets of the order of 3-4 ~m.

* a Trade Mark 15 ~33~843 The emulsion was found stable to 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 prevailed as in Example 1. The pH of the resulting emulsion was 2.8.

25 g of a special fraction of fatty acid/resin acid (same product as in Example 2) was 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. The method of preparation was otherwise carried out in accordance with Example 1, yielding a stable emulsion/dispersion having a pH
of 2.8.

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

~ ~98~13 A paper stock of the following composition was prepared:
70% fully bleached chemical pulp (60/40 birch sulphate/pine sulphate) 30~ calcium carbonate ("Sjohasten" from Malmokrita, Malmo, Sweden).
The birch and pine sulphates were milled together in a laboratory hollander to beating degree 200 ml CSF (Canadian Standard Freeness). The calcium car-bonate (slurried in water) was added and the stock was diluted to 0.5% dry solids content. The pH of the stock was 8Ø
In the experiment, different amounts were added, both of sizing agent according to Example 1 and of a conventional rosin size ("T-size 7635" from Hercules AB, Gothenburg") to different batches of the paper stock.
In the experiments with the conventional rosin size, 2% alum (calculated on dry pulp) was added in a conventional manner before the addition of size.
The sizing agents were supplied in the form of 1% solutions and added to the 0.5% stock under agitation (45 seconds). The stock was thereafter transferred to a laboratory wire mould (Finnish hand mould) with a 100 mesh wire. Sheet formation was performed according to SCAN C 26:67 (grammage was 73 g/m ). The sheets were dried overnight at 23~C and 50% relative humidity, * a Trade Mark ., ~
'~ i 8 ~ 9 whereupon they were placed in a heating cabinet (30 mi-nutes) at 120~C.
After conditioning (23~C, 50% relative humidity), water absorbency was determined according to SCAN
P 12:64 (Cobb60).
Table I gives the results of the tests. The added amounts of sizing agents (% by weight) relate to the added amount (active content) calculated on dry stock.
It appears from Table I that the sizing agent accord-ing to the invention gives fully satisfactory sizing (Cobb60<25) despite high pH and large amounts of cal-cium carbonate.

Sizing agentAmount added (%) Cobb60 (g/m2) Example 1 0.3 46 " 0.5 17 " 0.7 14 " 1.3 13 " 2.0 12 T-size 7635 0.3 95 " 0.7 74 " 1.3 44 2.0 35 l~3S~4~

A paper stock was prepared in the same manner as in Example 10. The resulting stock had a pH of 7.3. Different sizing agents according to the inven-tion were added to the stock.
Sheet forming and drying of the paper sheets were carried out in the manner stated in Example 8.
Water absorption according to Cobb60 (SCAN P 12:64) was determined. The results are given in Table 2.

Water absorption according to Cobb60 (g/m2) \ Addition %

Sizing \ 0 1.0 1.5 2.0 agent accord- \
ing to Example In this experiment, use was made of a paper stock from a magazine paper mill. The pulp consistency of the stock was 3% and the pulp was milled to beating degree 125 CSF. The composition of the pulp used was:
22% fully bleached chemical pulp 15% TMP (thermomechanical pulp) 35% groundwood pulp 28~ broke ~ 3 ~ 4 ~

To the stock was added 30% kaolin (C-clay from ECC) calculated on dry fiber. The stock was diluted to 0.5% concentation and pH was adjusted to 5Ø
Sizing agent prepared according to Example 3 was added in different amounts to the suspension of fibers and filler. Sheets were formed according to SCAN C 26:67 (grammage 73 g/m ).
In this experiment, the sheets were dried on a drying cylinder at 85~C. The sheets were thereafter placed in a drying oven (120~C) where they remained for 30 minutes.
After conditioning (23~C, 50% relative humidity), water absorbency was measured according to Cobb60.
The results of these measurements are given in Table 3.

% sizing agent Cobb60 according to 2 Example 4 (g/m ) 0.5 193 1.0 93 2.0 19 In this experiment, use was made of a paper pulp having a dry solids content of 1.37% and a beating degree of 200 ml CSF and consisting of 60% birch sul-phate pulp and 40% pine sulphate pulp.

~ 3 3~84~

To the paper pulp was added 30% calcium carbonate ("Sjohasten" from Malmokrita) calculated on dry fiber.
pH was thereafter adjusted to 8.5. A sizing agent prepared according to Example 1 was added to the stock in different amounts. Sheets were thereafter formed according to SCAN C 26:67 and had a grammage of 73 g/m2.
The sheets were dried and examined as described in Example 10. Sizing was very satisfactory. The sizing results are given in Table 4.

Water absorption according to Cobb60 (g/m2) \ ddition Sizing \
agent \ 0% 0.3% 0.5% 1.0% 2.0%

According to Example 1 103 58 27 15 12 In this experiment, use was made of the same paper stock and the same procedure as in Example 10.
The hydrophobing agent was however a sizing agent according to Example 8. It was added in different amounts, 0.6% cationic starch (calculated on dry stock) being added 15 seconds after the addition of size to serve as external retention agent. The results of the experiments appear from Table 5. It appears from the ex-periments that the sizing agent 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 was added.

Water absorption according to Cobb60 Sizing agent Addition Addition of cat-Cobb of slze ionic starch (%) (%) (g/m According to Example 8 0.3 0 83 " 0.5 0 65 " 1.0 0 50 " 2.0 0 46 According to Example 8 0.3 0.6 76 . " 0.5 0.6 67 " 1.0 0.6 37 " 2.0 0.6 18 Zero test 0 0 99 In the experiments according to this Example, use was made of a paper stock which had been prepared in the manner described in Example 10. In sizing, the same procedure was adopted as in Example lO, but in this present Example use was instead made of a sizing agent prepared in accordance with Example 9.
Fully satisfactory sizing was obtained also in this experiment, the result of which appears from Table 6.

l~3~4~

Water absorption according to Cobb60 Sizing agent Addition of size Cobb60 (g/m ) According to Example 9 0.3 71 " 0.5 66 " 1.0 46 " 2.0 17 Zero test 0 99 As hydrophobic substance in this Example, use was made of 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 hydro-phobic substance was added under very vigorous agitation (ULTRA TURRAX from IKA-Werk, Staufen) to a mixture con-sisting of 3 g cationic starch having a nitrogen content of 0.4%, 144.7 g polyaluminium chloride solution (KLOR-HYDROL from Reheis Chemical Ltd., Dublin, Al-content 12.5% by weight) and 92.3 g water. At emulsification, the temperature was 95~C for all chemicals included.

The emulsion was then homogenized for another 3 minutes at 10,000 rpm and thereafter cooled in a water bath to room temperature.
The pH of the thus prepared product was 3.7 and the particle size was about 1-2 ~m. The stability was satisfactory for more than two months.
* a Trade Mark 23 For testing the sizing agent thus prepared, a paper stock of the following composition was prepared:
80% fully bleached chemical pulp (60/40 birch sul-phate/pine sulphate) 20% calcium carbonate ("Sjohasten" from Malmokrita).
The birch and pine sulphates were milled together in a laboratory hollander to beating degree 200 ml CSF (Cana-dian Standard Freeness). The calcium carbonate (slurried in water) was added, and the stock was diluted to 0.5%
dry solids content. The pH of the stock was 8Ø
The sizing agents were added in the form of a 1% solution and added to the 0.5% stock under agitation (45 seconds). The stock was thereafter transferred to a laboratory wire mould (Finnish hand mould) with a 100 mesh wire. Sheet formation was carried out ac-cording to SCAN C 26:67 (grammage was 73 g/m ). The sheets were dried overnight at 23~C and 50% relative humidity, whereupon they were placed in a heating cabinet (30 minutes) at 120~C.
After conditioning (23~C, 50% relative humidity), water absorbency was determined according to SCAN
P 12:64 (Cobb60).
In Table 7, the results of the tests are given.
The added amounts of sizing agents (% by weight) relate to the added amount (active content) calculated on dry stock. It appears from Table 1 that the sizing agent according to the invention yields fully satis-factory sizing (Cobb60<25) despite high pH and large amounts of calcium carbonate.

3 .3 3 8 ~ ~

Sizing agentAmount added 1%)Cobb60 (g/m ) Example 16 0.3 71 " 0.5 64 " 0.8 22 " 1.0 18 " 2.0 15 Example 16 was repeated with the same constituents but with the following amounts of the different consti-tuents in the sizing agent emulsion:
48 g tall oil rosin 12 g paraffin wax 144.7 g polyaluminium chloride solution 3 g cationic starch 92.3 g water The resulting emulsion had a pH of 3.7, a particle size of about 1-2 ~m, and satisfactory stability for more than two months.
The emulsion was thereafter used for sizing the same paper stock as in Example 16, and the results of this test are given in Table 8.

1 3 3 ~

Sizing agentAmount added (%)Cobb60 (g/m ) Example 17 0.3 90 " 0.5 82 " 0.8 71 " 1.0 65 " 2.0 18

Claims

1. A hydrophobing agent comprising an emulsion/dispersion of a finely dispersed material in an aqueous phase, wherein the finely dispersed material contains a resin acid and/or fatty acid, and in that the aqueous phase contains an aluminum salt which is a polyaluminum chloride and/or a polyaluminum sulphate.

2. An agent as claimed in claim 1, wherein the finely dispersed material is a nonsaponified resin acid.

3. An agent as claimed in claim 2, wherein the resin acid is a fortified resin acid.

4. An agent as claimed in claim 1, wherein the aluminum salt is a polyaluminum chloride.

5. An agent as claimed in claim 1 or 4, wherein the molar ratio of aluminum to gegenion in the polyaluminum compound is above 1:1.

6. An agent as claimed in claim 1, wherein it also contains a cationic organic compound.

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

8. An agent as claimed in claim 1, 2 or 4, wherein it contains from 30-700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

9. An agent as claimed in claim 1 or 4, wherein the molar ratio of aluminum to gegenion in the polyaluminum compound is above 1:1, wherein it contains from 30-700 g/l resin acid and/or fatty acid from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

10. An agent as claimed in claim 1 or 4, wherein the molar ratio of aluminum to gegenion in the polyaluminum compound is above 1:1, wherein it contains from 30-700 g/l resin acid and/or fatty acid from 1 to 200 g/l polyaluminum compound, calculated as aluminum, and also from 0.05 to 200 g/l cationic organic compound.

11. An agent as claimed in claim 6 or 7, wherein it contains from 30-700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

12. An agent as claimed in claim 6 or 7, wherein it contains from 30-700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum, and also from 0.05 to 200 g/l cationic organic compound.

13. A method of preparing a hydrophobing agent, wherein an aqueous solution of an aluminum salt which is a polyaluminum chloride or a polyaluminum sulphate is formed and that resin acid and/or fatty acid are then emulsified/dispersed as a finely dispersed phase in said aqueous solution.

14. A method as claimed in claim 13, wherein the aqueous solution is also caused to contain a cationic compound.

15. A method as claimed in claim 13, wherein the material dispersed as a finely dispersed phase, is nonsaponified resin acid.

16. A method as claimed in claim 14, wherein the resin acid is a fortified resin acid.

17. A method as claimed in claim 13, wherein the aluminum salt is a polyaluminum chloride.

18. A method as claimed in claim 13 or 17, wherein the molar ratio of aluminum to gegenion in the aluminum salt is above 1:1.

19. A method as claimed in claim 13, wherein the cationic organic compound is cationic starch, cationic guar gum, cationic polyacrylic amide, polyamine, polyamide amine, or polyethylene imine.

20. A method as claimed in claim 13, 14 or 17, wherein the dispersion/emulsion is caused to contain from 30 to 700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

21. A method as claimed in claim 13 or 17, wherein the molar ratio of aluminum to gegenion in the aluminum salt is above 1:1, wherein the dispersion/emulsion is caused to contain from 30 to 700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

22. A method as claimed in claim 13 or 17, wherein the molar ratio of aluminum to gegenion in the aluminum salt is above 1 :I, wherein the dispersion/emulsion is caused to contain from 30 to 700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum and also from 0.05 to 200 g/l cationic organic compound.

23. A method as claimed in claim 19, wherein the dispersion/emulsion is caused to contain from 30 to 700 g/l resin acid and/or fatty acid, from 1 to 200 g/l polyaluminum compound, calculated as aluminum.

24. A method as claimed in claim 22, wherein the dispersion/emulsion is caused to also contain from 0.05 to 200 g/l cationic organic compound.

25. Use of a hydrophobing agent as claimed in claim 1, 2 or 4 for stock hydrophobation in papermaking technology.

26. Use of a hydrophobing agent as claimed in claim 1 or 4, wherein the molar ratio of aluminum to gegenion in the polyaluminum compound is above 1:1, for stock hydrophobation in papermaking technology.

27. Use of a hydrophobing agent as claimed in claim 6, for stock hydrophobation in papermaking technology.