CH630936A5 - Process for the preparation of pulverulent coloured pigments - Google Patents

Description

The invention relates to a method for producing powdered colored pigments which have good dispersibility. The pigments obtained can be used for pigmenting plastics, printing inks, lacquers, paints and coatings.

Pigments are understood to be inorganic and organic pigments.

When pigmenting materials such as thermoplastics, thermosets and printing inks, the aim is to distribute the pigment as finely and evenly as possible, but this is made more difficult by the relatively poor wettability and dispersibility of dry powder pigments in these media.

It is therefore common practice to use pigment preparations for coloring plastics and printing inks, which are obtained by dispersing a powder pigment in a suitable medium by means of kneaders, mixing rollers and similar apparatus. In such pigment preparations, which generally contain 15 to 70% pigment, the pigment is in a well-dispersed state. Suitable media are, for example, resins, plastics, solvents, plasticizers, dispersants or combinations of these substances.

However, the usability of these preparations is often limited to the coloring of plastics, printing inks etc. which are identical or at least compatible with the medium present in the preparations. This is especially true for pigment preparations that are used for pigmenting polyolefins, polystyrene and other plastics and that have high proportions of thermoplastic. In addition, the production of pigment preparations is complex and expensive because of the high energy and apparatus costs. A further disadvantage is that the physical properties of the pigmented end product, for example the notched impact strength, can be negatively influenced by the foreign substances which are necessarily carried in with the preparations.

In addition to the usual method for producing pigment preparations, for example by kneading a powder pigment with a thermoplastic composition at elevated temperature, other methods have also become known.

DT-AS 1 156 761 describes a process for the preparation of powdery pigment dispersions by mixing an aqueous pigment composition containing an organic dispersant (surfactant) with a stabilized aqueous polyolefin dispersion, coagulation, separating the aqueous phase, drying and pulverizing. The aqueous pigment mass is z. B. treated in a ball mill.

British patent 954 938 describes a process for the preparation of pigment dispersions by mixing highly disperse aqueous pigment pastes, which are obtained by grinding a pigment in water in the presence of a surface-active compound, with a stable aqueous polyvinyl chloride or vinyl chloride / vinyl acetate copolymer latex and then Coagulation.

From DT-OS 2 204 223 a process for the production of pigment preparations for coloring polyolefins is known, in which an aqueous alkali silicate solution and a polyethylene dispersion are added to a pigment and then coagulated by acidification.

DT-OS 2 019230 describes a process for the preparation of dispersant-free pigment preparations by mixing an aqueous dispersion of an emulsion polymer in, for example, methyl ethyl ketone with an aqueous pigment suspension and then removing the mixture of organic solvent and water and by further kneading above the softening temperature of the polymer used .

The disadvantages of these processes are that they require the addition of dispersants or other substances such as alkali silicates to the pigment dispersions, which makes the general applicability of the preparations impossible or that additional mechanical processing in the presence of organic solvents is necessary if dispersant-free preparations are to be produced.

The invention relates to a process for the production of powdered pigments with improved dispersibility, which avoids additional process steps, such as wet grinding of the pigment with a surfactant, addition of diluent auxiliaries (alkali silicates) and energy-intensive process steps, such as kneading pigment and polymer at high temperatures.

The process according to the invention for producing powdered colored pigments is characterized in that the polymer latex is coagulated with an intimate mixture of a dispersant-free pigment suspension and an aqueous polymer latex by adding an electrolyte with thorough mixing. The pigment obtained can then be separated off in a known manner and dried and optionally ground.

The pigments produced in this way can be used for pigmenting organic plastics, printing inks, lacquers, paints and coatings.

Both inorganic and organic pigments are used in the process according to the invention.

Suitable colored pigments are inorganic colored pigments such as chromium and iron oxides, cadmium pigments based on sulfide or sulfide / selenide, and mixed-phase pigments of the rutile or spinel type.

Suitable organic pigments can belong to all known pigment classes, for example copper ferrophthalocyanine pigments, quinacridone pigments, diaryl yellow pigments, dioxazine pigments, anthanthrone pigments,

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Thioindigo pigments, naphthalene tetracarboxylic acid pigments and azo pigments of the mono- and disazo series, in particular those of the acetoacetic acid arylamide, the ß-oxynaphthoic acid rearylamide or the varnished ß-oxynaphthoic acid series. For the purposes of the invention, preference is given to cadmium pigments, such as cadmium sulfide or cadmium sulfides with different contents of cadmium selenide or zinc sulfide, mixed-phase pigments of the rutile or spinel type, such as Nik-keltitan yellow, (Ti, Ni, Sb) O2, chromium titanium yellow, (Ti, Cr , Sb) O2, cobalt green (Co, Ni, Zn) 2 (Ti, Al) 04, cobalt blue, Co (Al, Cr) 2Û4, cobalt blue, C0AI2O4, phthalocyanine pigments, quinacridone and azo pigments. A particularly preferred place in the sense of the invention is occupied by all blue and green phthalocyanine pigments and all cadmium pigments.

Suitable polymer dispersions are those which e.g. be prepared from radically polymerizable vinyl monomers, for example aqueous latices made of ethylene, from dienes such as butadiene-1,3,2-methylbutadiene-l, 3,2-chlorobutadiene-1,3; from styrene, a-methylstyrene; from acrylic acid, methacrylic acid, acrylates and methacrylates, such as methyl, ethyl and butyl acrylate or methacrylate from acrylamide, methacrylamide, acrylonitrile and methacrylonitrile; from vinyl esters such as vinyl acetate and vinyl propionate; from vinyl ethers such as methyl, ethyl and isobutyl vinyl ether; from vinyl ketones such as methyl vinyl ketone and methyl isopropenyl ketone; from allyl compounds such as allyl alcohol, allyl chloride and allyl acetate; from vinyl chloride and vinylidene chloride. Copolymer latices of two or more of these monomers are also suitable.

Polyethylene, polystyrene, polyvinyl acetate and polyacrylate dispersions are particularly preferred.

Suitable polymer dispersions can be obtained by the generally known processes for the preparation of latices by emulsion polymerization (H. Logemann et al. In Houben-Weyl, Methods of Organic Chemistry, Vol. 14, Part 1, p. 133 ff., G. Thieme Verlag, Stuttgart, 1961). They can be prepared by batch or continuous processes and with or without the use of emulsifiers. The solids content of the latices can vary within wide limits, generally it is between about 10 and 70%. The latex particle size is generally nonuniform and is between about 0.1 and 0.35 (in. However, dispersions with particle sizes below 0.1 .mu.m can also be used. The average molecular weights of suitable latices can likewise vary and lie within wide limits generally in the range between 10,000 and several million, the range from about 10,000 up to 500,000 being preferred.

The intensive mixing usually takes place by means of conventional agitators or preferably with more intensive mixing units. Examples include: types based on the rotor-stator principle (e.g. Ultra-Turrax), high-speed stirrers (dissolvers, dispersers), sand or pearl mills etc.

Dry powder pigments can be used to prepare the aqueous pigment suspensions. However, it is generally more advantageous to use water-containing pigment pastes or pigment press cakes. The suitable pigment concentrations of these aqueous suspensions can vary within wide limits. Concentrations between about 35 and 5% by weight of pigment have proven to be practical. When using dissolvers, it is advantageous to initially select higher pigment concentrations of about 60 to 35% by weight to set pasty consistencies in order to achieve a better mixing effect.

When mixing aqueous pigment suspension and aqueous polymer dispersion, the order is not critical

table; however, it has proven advantageous to present the pigment suspension and let the latex run in.

Inorganic salts and acids can be used as electrolytes for coagulation.

The inorganic salts used are preferably salts of polyvalent cations, in magnesium chloride, magnesium sulfate, calcium chloride, barium chloride, aluminum chloride, aluminum sulfate, iron (II) chloride, cobalt chloride, nickel chloride, copper chloride or zinc chloride. Magnesium sulfate, calcium chloride and aluminum sulfate are particularly preferred. Hydrochloric acid, nitric acid and sulfuric acid are preferred as inorganic acids. Coagulation by adding electrolyte can be carried out in the cold or at elevated temperature. The range between about 20 and 80 ° C has proven particularly useful. An aqueous solution of the inorganic salt or the solid salt can be used.

Based on the total weight of pigment and latex solid used, 0.5 to 10% by weight of inorganic salt are generally required. If acid is used exclusively or additionally for coagulation, it has proven to be advantageous to set a pH between 6 and 1.

The powdered colored pigments produced according to the invention each consist of about 60 to 90% by weight of pigment and about 40 to 10% by weight of polymer.

It is also possible in the process according to the invention to use more than one pigment or to mix more than one polymer dispersion with it to prepare the aqueous pigment suspension.

The products can be dried at 10 to 300 ° C., preferably at 50 to 200 ° C. It is also possible to spray-dry the aqueous coagulate, if necessary, without prior separation.

The colored pigments produced according to the invention show an improved dispersibility in organic plastics, in printing inks, lacquers, paints and coating agents compared to the corresponding powder pigments of the starting material. They are also characterized by the fact that their application properties are closer to powdered pigment preparations and their color properties are closer to pure, unblended pigments. In addition, the pigments of the invention are less dusty and more free-flowing.

For pigmentation, the products produced according to the invention can be added individually or as a mixture to the plastics, printing inks etc. in the amounts customary for the respective plastics, the respective printing ink, etc.

It is also possible to combine several of the colored pigments produced according to the invention or to combine one or more of the colored pigments produced according to the invention with at least one organic or inorganic pigment present as a conventional powder pigment or as a pigment preparation.

The incorporation of the products can take place on screw injection molding machines, which have good plasticizing performance and good kneading action, directly during the shaping of the thermoplastic mass. In other cases, incorporation can be carried out on the machines customary for the respective plastic, for example extruders, kneading or mixing rolling mills, under the conditions customary in each case.

The usual additives such as blowing agents, antistatic agents, stabilizers, lubricants or other auxiliaries can be added to the plastics pigmented with the pigments produced according to the invention. They can be processed into molded parts, foils, threads or fibers on the usual machines using the known methods.

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630936

example 1

A 70.5% aqueous pigment suspension was prepared from 70 g of β-copper phthalocyanine (C.I. Pigment Blue 15, No. 74160) and 330 g of water using an Ultra-Turrax, which was heated to approx. 40 ° C. 5 Then, with the mixing unit running, 75 g of a 40% aqueous polyethylene dispersion (Hordamer PE 02, average particle size 0.1-0.2 p, m, average molecular weight of the solid 16,000-20,000, information from the manufacturer Hoechst AG) are run in . Without switching off the Ultra-Turrax, 30 g of a 10% aluminum sulfate solution were then added. The coagulate was suctioned off, washed thoroughly with warm water and dried in vacuo at approx. About 100 g of a product were obtained, which consisted of 70% by weight of copper phthalocyanine and 30% by weight of polyethylene.

Example 2

70 g of β-copper phthalocyanine (C.I. Pigment Blue 15, No. 74160) and 70 g of water were mixed to a 50% paste on 20 in a laboratory dissolver within 10 minutes and then diluted with 104 g of water to give a 25% pigment suspension. Subsequently, 75 g of the polyethylene dispersion from Example 1, then 30 g of a 10% aluminum sulfate solution were run in. Only then was the dissolver switched off, the coagulum isolated, washed and dried. About 98 g of a product were obtained which consisted of 70% by weight of copper phthalocyanine and 30% by weight of polyethylene.

Example 3 30

An approximately 15% aqueous pigment suspension was prepared from 70 g of β-copper phthalocyanine (C.I. Pigment Blue 15, No. 74160) and 400 g of water using a laboratory Perl mill within a few minutes. The suspension was transferred to an open vessel equipped with a blade stirrer. 75 g of the polyethylene dispersion from Example 1 and then 30 g of a 10% strength aluminum sulfate solution were run in with stirring. After the stirrer had been switched off, the coagulum was isolated, washed and dried. About 97 g of a product were obtained, which consisted of 70% by weight of copper phthalocyanine and 30% by weight of polyethylene.

Example 4

Production of a poly vinyl acetate latex:

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N2 was passed through 250 ml of water for about V2 hour. Then 100 g of vinyl acetate and 4 g of a sodium-Cn-Cis-alkyl sulfonate as an emulsifier were added with vigorous stirring and N2 conduction. A solution of 0.5 g K2S2O8 and 0.25 g NaHS03 in 50 ml 50 water was slowly added dropwise at 50 ° C. and the mixture was subsequently stirred at this temperature for 4 hours. A storable, about 25% polyvinyl acetate latex was obtained.

A 80% aqueous pigment suspension was prepared from 80 g of β-copper phthalocyanine (C.I. Pigment Blue 15, No. 74160) and 320 g of water using an Ultra Tursx. Subsequently, 80 g of the polyvinyl acetate latex prepared as described, then 30 g of a 10% aluminum sulfate solution were run in. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product were obtained, which consisted of 80% by weight of copper phthalocyanine and 20% by weight of polyvinyl acetate.

Example 5

178 g of a 45% water-containing a-copper phthalocyanine press cake (C.I. Pigment Blue 15, No. 74 160) and 200 g of water were turned into a 21% using an Ultra-Turrax

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aqueous pigment suspension. Subsequently, 80 g of a polymethyl methacrylate latex prepared as in Example 4 and then 30 g of a 10% aluminum sulfate solution were run in. After the Ultra-Turrax had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product were obtained which consisted of 80% by weight of copper phthalocyanine and 20% by weight of polymethyl methacrylate.

Example 6

An 18% aqueous pigment suspension was prepared from 200 g of the blue press cake from Example 5 and 300 g of water using an Ultra-Turrax. Then 40 g of a polybutyl acrylate latex prepared as in Example 4 were allowed to run in, then 30 g of a 10% aluminum sulfate solution. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product was obtained which consisted of 90% by weight of copper phthalocyanine and 10% by weight of polybutyl acrylate.

Example 7

A 15.5% aqueous pigment suspension was prepared from 114 g of an approximately 70% water-containing press cake of a perchlorinated copper phthalocyanine (C.I. Pigment Green 7, No. 74 260) and 400 g of water using an Ultra-Turrax. Subsequently, 80 g of a polystyrene latex produced analogously to Example 4 and then 30 g of a 10% strength aluminum sulfate solution were run in. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 99 g of a product was obtained which consisted of 80% by weight of copper phthalocyanine and 20% by weight of polystyrene.

Example 8

A 16 % aqueous pigment suspension prepared. Then 80 g of the polystyrene latex from Example 7, then 30 g of a 10% aluminum sulfate solution were run in. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product was obtained which consisted of 80% by weight of copper phthalocyanine and 20% by weight of polystyrene.

Example 9

A 21% aqueous pigment suspension was produced from 80 g of a red cadmium pigment (C.I. Pigment Red 108, No. 77 196) and 300 g of water using an Ultra-Turrax. Then 80 g of the polystyrene latex from Example 1, then 30 g of a 10% aluminum sulfate solution were run in. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product was obtained which consisted of 80% by weight of cadmium pigment and 20% by weight of polystyrene.

Example 10

A 19.5% aqueous pigment suspension was prepared from 114 g of an approximately 70% water-containing cadmium red pigment paste (C.I. Pigment Red 108, No. 77 196) and 300 g of water using an Ultra-Turrax. Then 80 g of the polystyrene latex from Example 7, then 30 g of a 10% aluminum sulfate solution were run in. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 98 g of a product were obtained which consisted of 80% by weight of cadmium pigment and 20% by weight of polystyrene.

630936

Example 11

An 18.5% aqueous pigment suspension was produced from 133 g of an approximately 60% water-containing cadmium yellow pigment paste (C.I. Pigment Yellow 37.77 199) and 300 g of water using an Ultra-Turrax. 50 g of the polyethylene dispersion from Example 1 were then allowed to run in, then 30 g of a 10% strength aluminum sulfate solution. After the mixing unit had been switched off, the coagulum was isolated, washed and dried. About 100 g of a product were obtained, which consisted of 80% by weight of cadmium pigment and 20% by weight of io polyethylene.

Example 12

6 g of the pigment prepared according to Example 4 were placed in a printing ink binder consisting of 7.5 g vinyl chloride-vinyl-15 acetate copolymer (manufacturer Hoechst AG), 5 g cyclohexanone and 31.5 g methyl ethyl ketone. This batch was placed in a 250 cm3 glass bottle containing 200 g of glass balls (3 mm 0). The dispersion was carried out on an intensive shaker according to DIN 53238 (draft). The corresponding raw material, ie the untreated pigment, was tested in all cases. After 6 and 60 minutes of dispersing time, samples were taken and applied to various substrates. Furthermore, the samples taken were mixed with a T DruckO2-containing white printing ink with a similar composition and the whitening whites thus obtained were likewise applied to the printing materials. The pigment produced according to this example reached 97% of the final color strength after 60 minutes of dispersion compared to the starting material (60 30

Minutes); Starting goods: 80%. Furthermore, prints based on the treated pigment showed advantages in gloss; Transparent, speck-free print films were obtained on cellophane films after a dispersion time of 6 minutes, which was not achieved with the untreated pigment even after the longer dispersion time.

Example 13

In each case 0.57 g of the pigments produced according to Examples 1 to 3 were mixed with 200 g of white pigmented low-pressure polyethylene (density 0.96 g / cm 3, manufacturer: Chem. Werke Hüls). The colored granulate was sprayed directly onto the molded part on a screw injection molding machine at 220 ° C. This gave molded parts which showed a homogeneous distribution of the pigment. A molded part produced with the starting pigment used in Examples 1 to 3 and with the same pigment concentration was not homogeneously colored. Clear pigment spots and streaks were visible. The color strength of the colorations obtained with the pigments prepared according to Examples 1 to 3 was assessed at 161.150 and 165% (coloration with starting pigment = 100%) in accordance with DIN 53 234.

Example 14

In each case 2.86 g of the pigments prepared according to Examples 1 to 3 were mixed with 1 kg of white-pigmented polystyrene (K value 64, density 1.05 g / cm 3, manufacturer: Chem. Werk Hüls). The colored granules were sprayed directly to the molded part on a screw injection molding machine at 240 ° C. Moldings were obtained which showed a homogeneous distribution of the pigment. A molded part produced with the starting pigment used in Examples 1 to 3 and with the same pigment concentration was not homogeneously colored. Clear pigment spots and streaks were visible. The color strength of the colorations obtained with the pigments prepared according to Examples 1 to 3 was rated at 177.160 and 180% (coloration with starting pigment = 100%) in accordance with DIN 53 234.

Example 15

2.5 g of the pigment prepared according to Example 8 were processed as described in Example 14. This gave molded parts which showed a homogeneous distribution of the pigment. A molded part produced with the starting pigment used in Example 8 and with the same pigment concentration was not homogeneously colored. Clear pigment specks and streaks were visible. The color strength of the coloring with the pigment according to Example 8 was rated 170% (coloring with starting pigment = 100%) according to DIN 53 234.

Example 16

2.5 g of the pigment prepared according to Example 9 were processed as described in Example 14. This gave molded parts which showed a homogeneous distribution of the pigment and great clarity in the clay. A molded part produced with the starting pigment used in Example 9 and with the same pigment concentration was not homogeneously colored. Color veils and pigment specks were visible.

Example 17

2.5 g of the pigment prepared according to Example 10 were processed as described in Example 14. This gave molded parts which showed a homogeneous distribution of the pigment. A molded part produced with the starting pigment used in Example 10 and with the same pigment concentration was not homogeneously colored. Clear pigment specks were visible. The color strength of the coloring with the pigment according to Example 10 was rated at 117% (coloring with starting pigment = 100%) according to DIN 53 234.

Example 18

2.5 g of the pigment produced according to Example 11 were mixed with 1 kg of the polyethylene from Example 13 and sprayed as molded parts there. This gave molded parts which showed a homogeneous distribution of the pigment. A molded part produced with the starting pigment used in Example 11 and with the same pigment concentration was not homogeneously colored. Clear pigment specks were visible. The color strength of the coloring with the pigment according to Example 11 was rated 197% (coloring with starting pigment = 100%) according to DIN 53 234.

Example 19

An aqueous pigment dispersion was prepared in accordance with Example 1 and the polyethylene dispersion was added. Without switching off the Ultra-Turrax, the pH was adjusted to about 2 with 10% sulfuric acid. The coagulate was suctioned off, washed thoroughly with warm water and dried at about 50 ° C. in vacuo. About 100 g of a product were obtained which consisted of 70% by weight of copper phthalocyanine and 30% by weight of polyethylene.

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Claims (7)

630 936 PATENT CLAIMS 1. A process for the preparation of powdered colored pigments, characterized in that the polymer latex is coagulated with an intimate mixture of a dispersant-free pigment suspension and an aqueous polymer latex by adding an electrolyte with thorough mixing. 2. The method according to claim 1, characterized in that the coagulated pigment obtained is separated and / or dried. 3. The method according to claim 2, characterized in that the dried pigment obtained is ground. 4. The method according to claim 1, characterized in that a polyethylene, polystyrene, polyvinyl acetate or polyacrylate dispersion is used as the polymer latex. 5. The method according to claim 1, characterized in that the pigments used are phthalocyanine pigments or cadmium pigments. 6. The method according to claim 1, characterized in that powdered colored pigments are produced which consist of 60-90 wt .-% of pigment to 40-10 wt .-% of polymer. 7. Use of the pulverulent colored pigments obtained by the process according to claim 1 for pigmenting organic plastics, printing inks, lacquers, paints and coatings.