FI63805C - FOERFARANDE FOER ATT GOERA PAPPER OCH KARTONG VATTENFRAONSTOETANDE GENOM TILLSATS AV VAXDISPERSIONER - Google Patents

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Federal Republic of Germany Förbundsrepubliken Tyskland (DE) P 281888Ο.9 (71) Mobil Oil Corporation, 150 East l2nd Street, New York, New York 10017, USA (72) Wolf Rainer Lehmann, Norderstedt, Peter Josef Reuss, Pinneberg,

Josef Weigl, Miincher, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (YM Berggren Oy Ab, (5l) Method for making paper and board water-repellent by adding wax dispersions

The invention relates to a method for making paper and board water-repellent (gluing) using wax dispersions.

Making the paper water-repellent, i.e. gluing using wax dispersions, is of particular importance in the production of high-quality paper such as writing paper, drawing paper or letterpress paper, but it is also important in the production of paperboard. Water repellency is generally accomplished by adding resins, aqueous dispersions of waxes, or both to the pulp. The mass itself is generally at an acidic pH, for example 4.4. This acidic internal sizing technique has numerous drawbacks, for example, it tends to corrode metal wires and other metal parts due to acidic conditions, and the paper produced has poor aging resistance and relatively poor strength. In addition, the use of certain reactive fillers, such as calcium carbonate, under acidic conditions is not possible.

It would be desirable to glue the paper, i.e., make it water repellent in an alkaline environment (pH 7 or alkaline pH) 63805 to avoid these drawbacks. There is also the advantage of operating at an alkaline pH that less energy is required to grind the fibers. In addition, smaller amounts are required when using optical brighteners. However, the types of adhesives used for neutral or alkaline internal gluing of paper are generally more expensive; they are usually the species theoretically intended to react with paper fibers, i. join them. Therefore, the use of wax dispersions has generally not been possible.

Alkyl ketene dimers have been used as sizing agents for papers and the like when treated at pH values of about 7. However, such paper sizing has a number of disadvantages, including excessive sensitivity to alum, depending on the type of drying, it may not occur until the paper has been stored for several days. In addition, the exact setting of the gluing degree is not possible.

It has also been suggested that dicarboxylic anhydrides could be used as sizing agents in neutral or alkaline internal sizing of paper. However, due to their limited shelf life, dicarboxylic anhydrides must be prepared immediately before being used on a paper machine, and in addition using expensive equipment.

For these reasons, wax dispersions have been used to make the paper water-repellent only when the pH of the pulp mixture has been on the acid side.

We have now developed a method for making paper and board water-repellent, i.e. gluing, by adding wax or paraffin dispersions to a pulp mixture which may contain fillers and other conventional additives and which has a weak pH on the acidic, neutral or alkaline side.

In fact, we have found that the wax particles of the dispersion can be attached to the fibers using a polypiperidine halide. In the presence of a polypiperidine halide, the pulp mixture can be given a pH that is alkaline, neutral or only weakly acidic, yet achieving good retention of the water-repellent agent. Generally, pH values of 6.5 or higher are used, 3 63805 usually between about 6.5-8.5.

In DE-OS 26 28 571 we have explained a method for improving the performance of optical brighteners in the paper industry. In this process, conventional anionic bleaching agents used in the paper industry are contacted with a polypiperidine halide which is adsorbed on a finely divided carrier in a dispersed state. Preferred polypiperidine halides are polypiperidine chloride and polydimethyldiallyl ammonium chloride. As carriers, finely divided inorganic substances such as kaolin or talc, and white pigments such as calcium carbonate, or finely divided organic substances such as starch can be used. However, the present process uses a polypiperidine halide, preferably polypiperidine chloride or bromide, as a wax dispersion in a neutral or alkaline medium.

According to the present invention, there is thus provided a process for making paper and board water-repellent by adding wax dispersions to a pulp mixture which may contain fillers and other additives, which process is characterized by adding an aqueous solution of polypiperidine halide as a fixing agent to the pulp mixture. The pH of the pulp is in the weakly acidic, neutral or alkaline range.

It has been found that the problems encountered in weakly acidic, neutral or alkaline internal sizing of paper and board can be solved by using wax dispersions in this way and, above all, that the disadvantages associated with sizing agent durability, alum sensitivity and delayed sizing effect are eliminated.

In particular, the method according to the invention has the following advantages: (a) Controlled water repellency (gluing) and precise setting of the degree of gluing in the pH range 6.5 and above, in particular between 6.5 and 8.5.

(b) Immediate water repellency effect in the paper machine area prior to surface treatment and thus control of possible coating retention.

(c) Easy supply and dosing of water repellent and fixing agent.

63805 (d) No sensitivity of alum to water repellent and fixing agents at all.

(e) No deterioration in paper strength even with higher amounts of water repellent agents.

(f) Improvement in flexural strength (reduction in slack) in heavily filled papers.

(g) Low tendency to dust and pluck in twig papers.

(h) Improved paper printability.

In addition, it has been found that the addition of a polypiperidine halide as a fixing agent not only fixes the water-repellent agent but also improves the retention of fillers in the paper.

If desired, excipient retention aids may be used, for example cationic retention aids in a concentration range of 0.02-0.3%. Polyacrylamides in the concentration range of 0.02-0.4% can be used as a suitable retention aid. Other cationic paper excipients such as epichlorohydrin resin based wet strength agents may also be used.

The pH can be adjusted with sodium hydroxide solution if the pH is too low. If the pH is already in the desired range due to the presence of other basic additives, a special pH adjustment is unnecessary.

Suitable wax dispersions for rendering paper and board water-repellent have long been known in the paper industry. Many are commercially available. Preferred water repellent agents are anionic wax dispersions sold for this purpose. Since the pH of the pulp can be weakly acidic, acid-stable anionic dispersions can be used, for example, the anionic, acid-stable wax dispersion called MOBILCER RV (trademark). Other types of dispersion can also be used if desired, for example cationic wax dispersions.

Preferred halides for the process of the invention are poly-piperidine chloride and polydimethylalkylammonium chloride, although other halides may be used if desired.

The wax dispersion and fixing agent can be added to the pulp in either order, for example the wax dispersion first and the fixing agent then, or vice versa. Other modifications will occur to those skilled in the art.

The invention is explained in more detail in the following examples.

All percentages mentioned in this specification are percentages by weight unless otherwise indicated.

The following pulp mixture was used in the examples:

Pulp mixture: 50% semi-bleached softwood sulphite pulp 50% bleached hardwood sulphate pulp Leaching resistance: 35 ° Schopper-Riegler

Paper basis weight: 80 g / m 2 pH: about 7.5.

To the pulp mixture (pulp consistency about 5%) was added polypiperidine chloride (polymer) as a fixing agent in a commercially available 40% aqueous solution in an amount of 0.05 to 2.0% abs. calculated on the dry matter. Prior to that, said 40% aqueous solution of poly-piperidine chloride was diluted with water to better distribute it into the pulp mixture.

A commercially available anionic aqueous wax dispersion (50% solids) was then added as a water-repellent sizing agent in an amount ranging from 1.0 to 4% abs. calculated on the dry matter.

In a few examples (Examples 15-17), the addition of calcium carbonate was performed in the form of a 25% aqueous slurry (filler slurry) to a 5% pulp mixture.

Prior to sheet formation, the resulting pulp mixture was diluted with water to about 0.5%.

The pulp mixtures were processed on a "Rapid-Koethen" type sheet machine (manufactured by K. Frank, Weinheim, Germany).

After the formed paper sheets were dried (in a photographic material dryer) and air-conditioned (in standard ratios according to DIN 50 014), the surface adsorption strength values of the papers against water were determined according to Cobb (Cobb ^ Q values DIN 53 132), the breaking length values (According to DIN 53 112) and ash contents (according to FAK-Merkbaltt IV / 40/67).

The results are shown in the following Tables I-III.

TABLE I

Pre- Wax dispersions (50% Polymer solution Cobbfi0 mark solids)% count- (40% solids) _ fox abs. dry% abs. calculated on the dry matter g / in _ of the material _ 12 130 2 2 0,5 85 3 2 1,2 40 43 - 135 5 3 0,2 60 6 3 0,4 22 74 - 130 8 4 0,3 22 8a +) 4 0.3 24 +) pH = 6.5

The following can be seen from Table I: (1) Depending on the amounts of wax dispersion and polymer added, full water repellency (full gluing) (Cobbg0 sec = 22 g / m 2, Examples 6 and 8) or partial water repellency (pre-gluing) 2 (CobbgQ sec = 40-60 g / m, Examples 3 and 5).

(2) There was no water repellency at all in the absence of polymer as the fixing agent (Cobb6Q sec = 130 g / mesh marks 1, 4 and 7).

(3) In Example 8a, the pH was 6.5. This knows that water repellency also works in this slightly acidic pH range. The pH value has set itself, i.e. the components in the system have set it up.

Examples 9-14 below illustrate the effect on paper break length.

7 63805

TABLE II

Pre-wax dispersions (50% Polymer!. Solution Break mark solids),% count (40% solids) length in fake abs-dry% calculated in abs. if- m _ of the material_ corresponding to the material_ _ 9 3 0,1 5200 10 3 0,4 5600 11 3 - 4800 12 4 0,1 - 0,2 4800 13 4 0,3 5200 14 4 - 4700

Table II shows that: (1) Even when a 3-4% wax dispersion is used, there is no reduction in the break length in the presence of the polymer that would otherwise occur when a 3-4% wax dispersion is present.

(2) An increase in the addition of polymer causes an increase in the breaking length (cf. Examples 10 and 13). Examples 15-17 illustrate the effect of a polymer on filler (calcium carbonate) retention and water repellency properties of paper.

TABLE III

Pre-Wax Dispersion (50% Polymer Ash Cobb- ..

mark solids),% las- (40% solids-CaCO,, fox abs. dry matter),% las. g / it of dry matter _ _ _ 15 3 0.1 2.5 100 16 3 0.3 2.5 80 17 3 0.4 8.5 60

Table III shows the effects of the polymer (40 in the form of an aqueous solution itself) as a fixing and retaining agent as follows: (1) As a fixing agent of the wax dispersion, when more polymer is added, the Cobbgg sec value decreases, i. water repellency improves.

(2) As a filler retention agent, the polymer increases the ash content of the paper.

In Examples 15-17, a filler retention agent, for example a cationic polyacrylamide (Percol 292), may be added. In this case, the Cobbg ^ sec values remain unchanged, while the ash values increase uniformly.

The process of the invention can be carried out using both anionic and cationic wax dispersions.

In the following Example 18, a cationic wax dispersion was used as a water-repellent agent.

Pre-Wax Dispersion (60% Polymer Solution Cobb ,,, solids),% abs. (40% solids), 60% dry matter abs. calculated on the dry matter Jc _____ calculated from g / m ^ 10 3.5 0.3 20

Claims (9)

9 63805 A process for making paper and board water-repellent using wax dispersions in a pulp mixture which may contain fillers and other additives, characterized in that an aqueous solution of a polypiperidine halide is added to the pulp mixture having a pH in the slightly acidic, neutral or alkaline range. Process according to Claim 1, characterized in that poly-piperidine chloride is used as the polypiperidine halide. Process according to Claim 1 or 2, characterized in that an aqueous solution of polypiperidine halide is added in an amount of 0.05 to 2.0%, based on the abs. Dry pulp mixture. Process according to one of Claims 1 to 3, characterized in that the addition of the polypiperidine halide solution to the pulp mixture is carried out at a pulp consistency of 0.05 to 6.5%. Process according to one of Claims 1 to 4, characterized in that an anionic wax dispersion is added in an amount of 0.1 to 4.0%, abs. calculated on the dry mass mixture. Process according to one of Claims 1 to 5, characterized in that a retention aid for fillers is additionally added. Process according to Claim 6, characterized in that the filler retention aid is an aqueous solution of a cationic polyacrylamide which is added in an amount of 0.02 to 0.04%, based on the dry mixture of pulp and filler. 10 63805 Process according to one of Claims 1 to 7, characterized in that the pH of the pulp mixture is 6.5 or more. Process according to one of Claims 1 to 8, characterized in that the pH of the pulp mixture is 6.5 to 8.5.