Water dispersion for sizing cellulose fibre

SWEDEN

PUBLISHING LETTER No. 361 908 mtci D 21 H 3/02

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PATENTS AND REGISTRATION OFFICE

<td>Patent Application. No. 9282/72</td><td>Received it</td><td>14 VII</td>

<td>Validity Day on</td><td> 14</td><td>VII 1972</td>

<td>Ans. widely available on</td><td> 19</td><td>XI 1973</td>

<td>Ans. laid out and laid out script published on</td><td> 19</td><td>XI 1973</td>

<td>Priority not requested</td><td></td><td></td>

KEMANORD AB, STOCKHOLM

Inventor: COA Lundin, Boräs

Agent: Z Schöld

Dispersion of ket end in hydrophobic layers of cellulose fibers

The present invention relates to a dispersion of ketene dimers for hydrophobizing cellulose fibers. In particular, it relates to a dispersion containing a ketene dimer as a hydrophobic component and a cationic dispersant system having such properties that the amount of ketene dimer can be kept very high with retained cationic properties without reducing the viscosity of the dispersion or reducing its storage resistance.

It is known to use ketene dimers for hydrophobizing cellulose fibers. In this case, the ketene dimer group reacts with the hydroxy groups of the cellulose, resulting in an irreversible bond between the cellulose molecule and the organic hydrophobic hydrocarbon groups in the ketene dimer molecule. When adding the ketene dimers to a water slurry of cellulose fibers, so-called stock additives, the ketene dimers are dispersed in water with the aid of a dispersant.

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It is also known that in the reaction between ketene dimers and cellulose fibers, the yield increases if the aqueous dispersions of ketene dimers contain a cationic dispersant. Using these cationic dispersions, the ketene dimer particles will have a better affinity for the slightly negatively charged cellulose fibers, thereby improving the yield of the reaction.

A serious disadvantage of previously described cationic ketene dimer dispersions is that the content of ketene dimer in the dispersion must be kept relatively low, usually about 3-8% by weight, partly to obtain optimum cationic activity in relation to the amount of ketene dimer, and partly that the viscosity of the dispersions and thus not handleability and stability. should be jeopardized. This means that transport costs from the manufacturer of the dispersions to the consumer are high, while storage tanks and the like get large dimensions.

While attempting to increase the ketene dimer content by introducing additional ketene dimer into a cationic dispersion, while providing higher dry content of ketene dimer, it thereby disrupts the cation activity of the system so that the hydrophobic effect of the dispersion upon application to cellulose fibers is significantly lowered. By increasing the dry content by simultaneously increasing the amount of ketene dimer and cationic emulsifier, the viscosity of the dispersion is increased to such an extent that its manageability is reduced. In addition, most cationic dispersants exhibit a tendency to gel the dispersions upon storage at high concentrations.

According to the present invention, it has been found that stable dispersions of ketene dimers having a dry content up to 25% by weight can be obtained, which, when diluted and applied to cellulose fibers, provide improved yield in the hydrophobic reaction in comparison with most previously known low dry ketene dimer dispersions. The dispersions of the invention, in combination with a cationic dispersant, also contain alkyl hydroxyalkyl cellulose as a dispersant.

The dispersion system according to the invention enables ketene dimer dispersions with high solids content to be produced without the viscosity of the dispersion being so high as to reduce its manageability. Furthermore, despite their high dry content, these dispersions are very stable,

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Y and storage for 6 months at room temperature does not affect the viscosity. Another advantage of the dispersions is that the amount of dispersant based on the ketene dimer can be kept very low, usually down to about 4-5% by weight, based on the ketene dimer. For example, when using only cationic starch as a dispersant, it should be present in an amount of at least 30% by weight, based on the ketene dimer, to obtain satisfactory dispersions with good hydrophobic effect. Also, due to the particular dispersant system, the compositions of the invention do not appear to be sensitive to oxidizing residual chlorine, for example chlorate ions in the cellulose, which is usually present when the cellulose pulp is bleached with chlorine compounds prior to papermaking.

The alkyl hydroxyalkyl cellulose contained in the dispersant system is preferably a water-soluble or water-dispersible cellulose having a Brookfield viscosity in 2% solution at 20 ° C in the range 20-12000 cp. Examples of suitable types may be mentioned where the alkyl group is a lower alkyl group, preferably methyl or ethyl, and wherein the alkyl hydroxy group is a hydroxy lower alkyl group such as an ethyl hydroxy or a propyl hydroxy group. The carbon chain in the hydroxyalkyl group may also be interrupted by one or more oxygen atoms. It may also be convenient to use mixtures of these cellulose ethers.

Such cationic dispersants can be used in any of the previously known water-soluble or water-dispersible cationic polymers. These are previously described as retention, wet strength or dry strength agents in papermaking, and examples of preferred cationic, water-soluble or water-dispersible polymers include: cationic starch, polyethyleneimine, polyacrylamide, polyvinylpyridine, polyalkylene amine polyamide_isn_yourepichlorohydrin modified such. Particularly good results have been obtained with cationic polyvinylpyridine.

The ketene dimers used according to the invention are known in the art and have the following general formula

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where R₁ and K₂ independently of one another denotes an organic hydrophobic hydrocarbon group containing from 8 to 40 carbon atoms.

The organic hydrophobic hydrocarbon groups R R and R R₂ found to be useful for hydrophobizing cellulose fiber materials are those in which the hydrophobic group is a higher alkyl having at least about 8 carbon atoms, for example, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, tetracosyl and pentacosyl up to about 40 carbon atoms, if desired, although those with about 12-30 carbon atoms are preferred, the corresponding alkenyl groups having between about 8 and about 40 carbon atoms, among which may be mentioned as some examples decenyl, tridecenyl, heptadecenyl, octadecenyl, eicosenyl, tricosenyl, etc. aralkyl, alkaryl and alkyl substituted cycloalkyl having at least about 8 carbon atoms, for example 4-tert.butylphenyl, octylphenyl, nonylphenyl, dodecylphenyl, dodecylphenyl, dodecylphenyl heneicosylphenyl, nonylcyclopropyl, dodecylcyclobutyl, tridecylcyclopentyl, tetradecylcyclohexyl, pentadecylcycloheptyl, octadecylcyclohexyl etc. and any of these alkyl, alkenyl, alkaryl, and alkylcycloalkyl groups containing non-interfering, inert substituents.

Among inert substituents may be mentioned carboalkoxy, alkyloxy, aryloxy, arylalkyloxy, keto (carbonyl), tert-amide groups etc. Among examples of radicals which should not be found to any great extent in the hydrophobic group can be mentioned, for example , primary and secondary amino groups, labile halogens, amide groups containing amide hydrogen and carboxyl groups or other acidic groups. It will be apparent to those skilled in the art which groups can be used in these compounds if undesirable side reactions are to be avoided.

Preferably, R och and R. Are₂ independently of one another an alkyl group containing 12-30 carbon atoms. The ketene dimers included in the composition may also be a mixture of the above compounds.

The ketene dimers are prepared in known manner, for example, by reaction between thionyl chloride and carboxylic acids containing the above-mentioned hydrophobic hydrocarbon group to obtain the corresponding acid chlorides, which are then dimerized into ketene dimers during hydrochloric acid purification.

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The amount of alkyl hydroxyalkyl cellulose in dispersions according to the invention should be in the range of 0.5 to 10 weight percent, preferably 0.8 to 8 weight percent, based on the ketene dimer. The amount of cation-active polymer should also be within the range of about 0.5 - 10% by weight, preferably 1-10% by weight, based on the ketene dimer. Thus, the total amount of dispersant in the present dispersions is in the range of 1-20% by weight, preferably 1.8-18% by weight, based on the amount of ketene dimer. The relative ratio of the cellulose ether to the cationic polymer may vary within the range of 1:20 - 20: 1, preferably 1: 7 - 5: 1.

As stated above, the dispersant system of the invention allows stable dispersions with high dry content of ketene dimer to be produced without reducing the effect of the ketene dimer as a hydrophobic agent when the dispersions are diluted and added to a slurry of cellulose fibers in water. According to the invention, it is possible to produce dispersions with dry content of ketene dimer of up to about 30% by weight, without the viscosity properties or storage stability of the dispersion jeopardizing its use as a hydrophobing agent. The best results mentioned above are obtained with dispersions having a dry content in the range of 10-25% by weight of ketene dimer, preferably 15-20% by weight.

In preparing dispersions according to the invention, the constituent components are mixed with water, after which the mixture is subjected to severe shear. To facilitate mixing, the aqueous phase containing cellulose ether and cation-active polymer is heated to about 50-80 ° C, after which a melt of the ketene dimer is added.

It is essential that the temperature is not kept too high, as this can cause the ketene dimer to be hydrolyzed. The upper limit of the heating is determined by the type of ketene dimer used. The emulsion obtained after mixing and shearing is then rapidly cooled to form a stable dispersion.

The dispersions thus obtained can then be added either immediately or after storage either to a slurry of cellulose fibers in water or used for coating paper, cardboard or other materials containing cellulose fibers. When added to one

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slurry of fibers in water first dilutes the dispersion to a dry content of about 3% by weight or less before adding it to the stock.

After adding the dispersion to the stock can. the pulp is formed into sheets and dried in a known manner. After forming, the paper can be cured by heating for a short time at a temperature of about 100 ° C or the paper can be cured at room temperature. The invention is described in more detail in the following embodiments, however, which are not intended to limit the same. In the examples, parts and percentages indicate by weight and by weight, respectively. weight percent unless otherwise stated.

EXAMPLE 1 AE

In the following examples, dispersions containing as a dispersant ethyl hydroxyethyl cellulose (Modocol E 200, Mo and Domsjö, Sweden) and various water-soluble cation-active polymers were prepared, as shown in Table I.

The cellulose ether and the resp. cation-active polymers were dissolved in water. The aqueous solution was adjusted to pH 4.0 and heated to 60 ° C.

To each 82 parts of these aqueous solutions, 18 parts of molten ketene dimer, made up of mainly palmitic and stearic acid, were added with vigorous stirring in a Turrax stirrer for 3 minutes. The hot emulsion was then homogenized in a slit homogenizer p

at a pressure of 190 kg / cm and cooled to room temperature when passing through a plate cooler. The dispersions thus obtained were stored for 1 week in a heater at 40 ° C to check their storage resistance. The results are presented in Table I. As can be seen from the table, the dispersions show very good storage stability despite the unfavorable storage conditions.

EXAMPLE 2 AB g of bleached magnetite mass ground to about 30 ° SR and diluted to a dry content of 0.2 percent containing 20 percent chalk based on dry fibers was added with 1 'ml of the dispersions of the previous example diluted to 1% ketene dimer content and 2 ml of a 0.1% aqueous solution of a cationic polyacrylamide polymer (such as chalk zero fibers). Sheeting was done in a laboratory sheet former, the sheets pressed, dried for 1 hour at 100 ° C and conditioned. As a reference sample (ref. 1 in the table), a commercially available ketene dimer dispersion having a dry content of 6% ketene dimer and containing 50 # of cationic starch, calculated on the ketene dimer, was used as a dispersant.

As shown in Table I, the dispersions of the invention exhibit substantially the same hydrophobic effect as the low dry ketene dimer dispersion, which shows that good cation activity is obtained despite the high ketene dimer amount. By comparison, non-hydrophobic paper has a Cobb number greater than 130 g / m 2.

EXAMPLE 3

In the same manner as described in Example 1, various dispersions of ketene dimers were prepared, except that the amount of cationic dispersant (in this case a cationic polyvinylpyridine) was kept constant and with methyl hydroxypropyl and resp. ethyl hydroxyethyl cellulose as additional dispersant. As a comparison to this cellulose ether, a similar compound, hydroxyethyl cellulose (ref. 2 in the table) was used. The various dispersions were stored in the same manner as described in Example 1 and the results are reported in Table I.

As can be seen from the table, it is essential for the storage stability of the dispersiorpma that alkyl hydroxyalkyl cellulose is present.

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EXAMPLE 4

The storage stable dispersions of the previous example were used for gluing bleached magnetite pulp in the same manner as in Example 2.

It can be seen from Table I that the hydrophobic effect obtained is roughly equivalent to that obtained with low dry ketene dimer dispersions.

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In hydrophobic experiments on an experimental paper machine with a capacity of about 50 kg of paper per hour at a gram weight of 65 g / m² two hydrophobic systems were compared, one a composition according to the invention and the other a commercially available hydrophobic system.

Hydrophobic system I (according to the invention) consisted of an 18-g ketene dimer dispersion containing 1,4 # ethyl hydroxytetylcellulose and 4.2 # polyvinylpyridine as a dispersant, 'both counted on the ketene dimer. In addition, a cationic polyacrylamide was added to the stock as a zero fiber and filler retention agent. The l8 dispersion was diluted with water before adding to the stock, and the final concentration of ketene dimer in the stock was 0.08 # based on the dry weight of the fibers. The amount of retention agent was 0.03% based on the dry weight of the fibers.

Hydrophobic system II (a commercially available product) consisted of a 6 percent ketene dimer dispersion containing 50% cationic starch, based on the ketene dimer, as a dispersant.

In this case, an epichlorohydrin modified cation-active polyalkylene polyamide resin was used as the retention agent for zero fibers and fillers. The 6 percent dispersion was diluted with water before adding to the stock and the final concentration of ketene dimer in the stock was 0.1% based on the dry weight of the fibers, while the amount of retention agent was 0.07 # based on the dry weight of the fibers.

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The pulp was bleached birch sulfate. Hydrophobic experiments were carried out partly under normal conditions (A = pH adjusted to 7.5 by the addition of sodium bicarbonate) and partly by disturbances in the form of low pH (B) in the presence of chlorate ions (C = addition of about 0.1? Sodium chlorate). to simulate residual chlorine from bleaching steps of the pulp or by the addition of 0.3? alum (D). In all cases, the experiments were performed both without filler and with filler. The hydrophobic effect was determined after natural aging of the paper for 14 days at 23 ° C and a relative humidity of 50

The results are shown in the following table.

TABLE II

<td rowspan="2">Attempt</td><td rowspan="2">pH</td><td rowspan="2">Additive- average</td><td colspan="2">2 Hyobophobic effect Cobb ^_A g / m</td>

<td>Hydrophobic system I</td><td>Hydrophobic system 11</td>

<td>A</td><td> 7,5</td><td>unfilled</td><td> 27,8</td><td> 46,2</td>

<td>A</td><td> 7,5</td><td>chalk</td><td> 29,5</td><td> 31,6</td>

<td>B</td><td> 6,8</td><td>unfilled</td><td> 27,1</td><td> 32,3</td>

<td>B</td><td> 7,1'</td><td>chalk</td><td> 27,5</td><td> 29,7</td>

<td>C</td><td> 7,5</td><td>unfilled</td><td> 29,6</td><td> 64,0</td>

<td>C</td><td> 7,5</td><td>chalk</td><td> 29,5</td><td> 31,4</td>

<td>D</td><td> 7,5</td><td>unfilled</td><td> 28,0</td><td> 28,5</td>

<td>D</td><td> 7,5</td><td>chalk</td><td> 29,3</td><td> 28,6</td>

As shown in the table, a very uniform hydrophobic effect is obtained with the dispersions of the invention. In addition, the present dispersions exhibit improved hydrophobing compared to the prior art hydrophobic system, despite the fact that smaller ketene dimers are charged through the dispersions of the invention.

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