FI62957B - FOERFARANDE FOER FRAMSTAELLNING AV VISKOSITETSSTABILA VATTENDISPERSIONER FOER PAPPERSBESTRYKNINGSMASSOR - Google Patents

Description

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National Board of Patents and Registration .... OÖ.07.70 „, ^ ', (44) NlhUviksIpaneo * months | -

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Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2700iUi.O

(71) Veba-Chemie Aktiengesellschaft, Gelsenkirchen-Scholven,

Federal Republic of Germany-Förbundsrepubliken l’yskland (DE) (72) Felix Schiilde, Wulfen-Barkenberg, Volker Kulisch, Gladbeck,

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (7 * 0 Oy Kolster Ab (5 * 0 Method for the preparation of aqueous dispersions of stable viscosity for paper pulp)

The invention relates to a process for the preparation of aqueous pigment dispersions of stable viscosity for use as paper spreads.

Pulps consist mainly of water-dispersed fillers or pigments, in addition to which they contain a binder and a dispersant. The pigments used include, for example, calcium carbonate, kaolin, calcium sulfoaluminate and the like. Aqueous dispersions of these pigments, which in practice can have a solids content of 30-70% by weight, settle relatively quickly and, in the case of kaolin, become solid due to the so-called card house effect caused by different electrical charges on the surfaces and edges of the plate-like pigment particles. The addition of dispersants to the pigment slurry is therefore necessary to keep the desired treatment viscosity constant. In addition, in practice, it is often difficult to increase the viscosity of the coating inks for a slightly mechanized treatment, so that a viscosity-increasing effect of the dispersant is desirable. In this case, however, it is important that the viscosity once adjusted remains constant for as long as possible.

The dispersant affects the required Theological stability of the dispersion. The dispersing effect depends on the increase in the zeta potential of the pigment particles; it also depends on the fact that the pigment particles have surface charges that repel each other and thus maintain a stable dispersion state.

It is known, for example, to add complex phosphates, salts of polyphosphoric acid or salts of polycarboxylic acids as dispersants to paper lubricant pulps.

The use of these conventional materials in the prior art has shown that the viscosity of the pigment slurry can be reduced - resulting in low viscosity values in low cutting areas; continuous thickening during prolonged storage. In addition, the effectiveness depends relatively narrowly on the pH of the dispersion.

Thus, the present invention is directed to materials suitable for dispersing pigments which retain their potency over a wide range of viscosities regardless of pH without the dispersing power decreasing during prolonged storage of the coating compositions.

It has now surprisingly been found that pigment dispersions are obtained without the disadvantages shown if certain maleic acid hydride copolymers, hereinafter referred to as MHA copolymers, are used as dispersant.

This finding is particularly surprising because the use of the ΓΙΗΛ-copolymers of the invention in papermaking has been thoroughly studied, however, only with respect to their use as a paper adhesive or binder.

The invention therefore relates to a process for the preparation of aqueous pigment dispersions having a stable viscosity for paper-coating compositions using conventional fillers or pigments and special MHA copolymers and, if desired, conventional additives, which process is characterized in that L | | | Compounds according to CO 2 R 2, II M1 M 2 in amounts of 0.05 to 5.0% by weight, preferably 0.2 to 0.5% by weight, based on the proportion of pigment, wherein and are the same or different and represent the group -H or -CH 2 and and M 2 are the same and represent -O-alkali metal or -ONH 4, preferably O- / Na or and and M 2 are different and are -NH 2 or a lower amine and M 2 is -OH or -O-alkali metal, or - ONH4 and n are an integer from 2 to 500, preferably from 40 to 50.

Suitable MHA copolymer solvates for the purposes of the present invention which correspond to the general formula above are, for example, maleic acid-propylene-sodium salt, maleic acid -propyl-4-ene-ammonium salt, maleic acid-ethylene-sodium salt, maleic acid-ethylene-half-amide, maleic acid. Mixtures of maleic acid anhydride copolymers as well as mixtures with conventional dispersants can also be used for the purposes of the invention.

The copolymers used according to the invention can be prepared by methods known per se.

The pigment dispersion according to the invention is prepared in a simple manner: first the MHA copolymers according to the invention are dissolved in water, this solution is adjusted to the desired pH with alkalis, for example sodium hydroxide solution or ammonia, the pigments are added with stirring for 10 minutes and stirring is continued for 10 minutes.

4 62957

The pigment dispersions thus obtained can be added with the necessary additives, such as binder, colorants, antifoams, etc.

Pigment dispersions prepared by the process of the invention can be used to brush and coat fibrous materials such as paper and cardboard.

The advantages of the present pigment dispersions are based on the fact that when the MHA copolymers according to the invention are added, the viscosity of the dispersion remains constant at the desired value for long periods of time.

It was further found that the pH of the dispersion had no significant effect on the efficiency of the MHA copolymers.

Example 1

Dispersion I

Calcium carbonate bearing the symbol "Millicarb" was stirred for 10 minutes of the formula: -r CH - CH - CH - CH - 1-Ll I I 2J 40 CO CO CH.,

I I

ONa to an aqueous solution of maleic anhydride of the invention adjusted to pH 9 with NaOH, the propylene-MHA ratio being 1: 1, and the mixture was further homogenized for 10 minutes. The dispersion thus obtained had a solids content of 55% by weight and contained 0.3% by weight of the dispersant according to the invention.

Dispersion II (Comparative) This dispersion was prepared in the same manner as Dispersion I except that MHA-styrene-based dispersant was added instead of the maleic anhydride-propylene sodium salt of the present invention.

Dispersion III

Kaolin labeled "SPS" was dispersed according to Dispersion I. As a substance according to the invention, the formula: M I | Copolymer of CO 4 CH 3 I 3 NH 2 ONa 5 62957 with a propylene-MHA ratio of 1: 1 in aqueous NaOH adjusted to pH 9. The dispersion thus prepared had a solids content of 55% by weight and contained 0.3% by weight of dispersant.

Dispersion IV (Comparative) This dispersion was prepared using kaolin "SPS", but other than Dispersion II.

Dispersions I-IV were measured for viscosities at 20 ° C. Measurements were performed immediately after preparation, after 1 hour 2 hours and 24 hours. The results are shown in Table 1 below.

Viscosity Dispersion

At 20 C (cP) Σ n m IV

After preparation 6 15 48 380 After 1 hour 7 16 50 557 After 2 hours 7 16 50 4000 After 24 hours 7 Solid 50 Solid

It is obvious that the viscosities of the dispersions prepared according to the present invention were maintained during storage, in contrast, the viscosities of the reference dispersions II and IV increased sharply.

Example 2

Dispersions were prepared according to III and IV, where n was 45 in the maleic anhydride copolymer used. The solids contents were 50, 55 and 60% by weight. Table 2 shows the viscosities measured from these dispersions.

Table 2 _Dispersion____III___IV_______

Solids content (%) 50 55 60 50 55 60 viscosity at 20 ° C (cP) 26 48 82 250 380 not measurable

Example 3

Table 3 shows the relatively high pH independence of the dispersions according to the invention. Dispersions were prepared according to sections III and IV and their pH was adjusted to 8, 9 and 10 with NaOH.

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Table 3

Dispersion III IV

pH 8 9 10 8 9 10 Viscosity at 20 ° C (cP) 18 18 18 107 380 739

Example 4

Dispersion III containing 55% by weight of kaolin and 0.3% by weight of the dispersant according to the invention, propylene-maleic acid half-amide, was adjusted to pH 9 with NaOH and stored for 520 hours at room temperature. Figure 1 shows the smooth flow of this dispersion throughout the storage period and clearly shows the effect of MHA copolymers in the sense of the present invention.

Example 5

Dispersion V

The calcium carbonate was stirred for 10 minutes in the form of a maleic anhydride copolymer of the invention according to the formula: CH 2 CH 3 - CH 2 - CH 2 -F L (| 2 2 J 35 CO CO II ONa ONa adjusted to pH 9 with NH , with an ethylene-MHA ratio of 1: 1, to an aqueous solution and the mixture was further homogenized for 10 minutes, the dispersion thus obtained having a solids content of 55% by weight and containing 0.2% by weight of a dispersant according to the invention.

Dispersion VI

This dispersion was prepared in the same way as dispersion V, it contained 0.3% by weight of dispersant.

Dispersion VII

This dispersion was prepared using 0.4% by weight of dispersant, but otherwise in the same way as dispersion V.

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Viscosities at 20 ° C were measured from dispersions V-VII. The measurement was performed immediately after preparation at 1, 2 and 24 hours. The results are shown in Table 4.

Table 4 years VI VII

Dispersant content (% by weight) 0.2 0.3 0.4

Viscosity at 20 ° C (cP) after preparation 666 After 1 hour 76 6 After 2 hours 76 6 After 24 hours 86 6

Example 6

Dispersion VIII

This dispersion was prepared in the same way as dispersion I except that instead of 0.3% by weight of maleic acid-propylene-sodium salt was added a mixture containing 0.2% by weight of maleic acid-ethylene-sodium salt and 0.2% by weight of maleic acid-propylene-sodium salt (total 0.4% by weight of dispersant).

Viscosity measurements were performed as in Example 1 and the results are shown in Table 5.

Table 5

Dispersion VIII

Viscosity at 20 ° C (cP) after preparation 6 After 1 hour 7 After 2 hours 7 After 24 hours 8

Claims (4)

8 62957 A process for the preparation of aqueous pigment dispersions of stable viscosity for pulp using conventional fillers or pigments and special maleic anhydride copolymers and optionally customary additives, characterized in that the maleic anhydride copolymer is used II 2 J CO CO R_ II 2 Μχ M2 in amounts of 0.05 to 5.0% by weight, preferably 0.2 to 0.5% by weight, based on the proportion of pigment, wherein and R 1 are the same or different and represent the group -H or “ CH 2 and and M 2 are the same and represent a group -O-alkali metal or -ONH 2 or and M 2 are different and is a group -NH 2 or a lower amine and M 2 is a group -OH, -O-alkali metal or -ONH 2 and n is an integer from 2 to 500, preferably from 40 to 50 Process according to Claim 1, characterized in that propylene-maleic acid half-amide is preferably added. Process according to Claim 1, characterized in that mixtures of different MHA copolymers are used as dispersants. Process according to Claim 1, characterized in that mixtures of MHA copolymers with other dispersants are used as dispersants.