CA1116813A - Process for conditioning a pigment or disperse dye - Google Patents

Abstract

Abstract of the Disclosure A process for conditioning a pigment or disperse dye which comprises treating the colourant with liquid ammonia and results in an improvement of the dyeing properties and may be accompanied by a conversion into another modification.

Description

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The invention relates to a process for conditioning a pigment or disperse dye by treating the colourant with liquid ammonia.
The term "conditioning" is to be understood in this context as meaning, in addltion to an improvement of the tinctorial properties, also a possible conversion into another m~dification.

Various processes for conditioning a pigment or disperse dye in order to improve the tinctorial properties are already known. One known method is to dissolve the colourant in an organic or inorganic solvent and to precipitate it again from the solution by cyrstallisation or precipitation. In the same way, organic solvents are used which do not dissolve the pigment, but produce the conditioning effects or modifications -under the influence of time and temperature. Further known methods of conditioning are those in which the pigment is ground or kneaded Japanese published patent application 25526/76 for example describes a process for improving the tinctorial properties of an isoindolinone pigment, especially the colour strength, gloss and transparency, by dissolving the pigment in a mono-or dialkylamine, precipitating it in the form of the amine salt by the addition of water, cleaving the amine salt by heating, and separating the amine from the pigment again. In this process, the pigment is recovered in the starting .~

- 2 -i~6813 modificatkn A changein ~e mod~i~tion,for example of the linear quinacridone into the y-modification, occurs ho~ever by treating the corresponding ~-form in accordance with the process of Japanese published patent application 50699/65 with an aliphatic polyamine of the formula NH2(R-NH)nH, wherein R represents a linear saturated aliphatic radical and n is an integer from 1 to 3, at elevated temperature.

Compared with the process of Japanese published patent application 25526/76, the process of the present invention has the advantage that, without dissolving and precipitating the pigment beforehand with water after the treatment with liquid ammonia, another modification and improved application properties of the colourant are obtained only by evaporating the reagent; and the advantage compared with the process of Japanese published patent applicat~on 50699/65 consists in the fact that, for the treatment, liquid ammonia is used instead of a polyamine and elevated temperatures are not necessary in order to effect a conversion into another modification or to obtain improved application properties. It is surprising that, during the treatment with liquid ammonia, such conversions occur even at low temperatures up to -77.7C.

Preferably, the pigments or disperse dyes to be conditioned by the process of the present invention are those of the isoindolinone, azo, metal complex, quinophthalone and 1 116 8 1 ~

quinacridone series, and, in the case of the conversion into a modification, this latter can be either an already known or also a hitherto unknown modification.

In the treatment with liquid ammonia, which can be carried out optionally under elevated pressure and/or at elevated temperature, the colourant is suspended in the reagent and stirred therein This procedure can take both hours and sometimes only minutes or seconds. In the conversion into a modification, the completion of the treatment is oten detectable by the change in colour. The conditioned colourant is isolated by filtration and subsequent r~moval of the ammonia by evaporation or by direct evaporation thereof.
Optionally, the colourant is partially or also completely dissolved in the reagent. In this case, the reagent is remo-ved by direct evaporation, whereupon the dissolved colourant precipitates and is isolated If the colourant is only partially dissolved, then filtration can first be carried out and the two colourant fractions isolated separately fr~m the filter residue or the filtrate Provided the presence of small amounts of water and/or organic solvents does not exert a negative influence on the conversion into the new modification, these substances can also be tolerated. However, the treatment is preferably carried out in the absence of water and/or an organic solvent. The treated pigments are often obt ined in such microcrystalline form that they are ~168i3 amorphous in X-ray analysis By increasing the size of the microcrystals,~ ~mpleby ~t~treatment with organic liquids, they can be converted into a dimension in which the new modification can be detected by X-ray diffraction analysis.

When incorporated in lacquers, the products obtained according to the invention have an increased colour strength and gloss c~mpared with the starting products. Furthermore~
in the course of the treatment pigments can be obtained in a finer and more coarsely crystalline new, but unstable, modification, compared with the starting form On account of this instability, the starting modification is obtained again on application, in fine or coarse crystalline form, depending on the mode af application. This can result in an increase in colour strength and gloss or in the hiding power.

The application properties of the pigments treated with ammonia, for example in respect of the wetting power on incorporation or the rheological properties, can often generally be improved. The pigments can be inorganic and organic pigments, for example of the class of azo, azomethine, anthraquinone, phthalocyanine, nitro, perinone, perylene, dioxazine, thioindigo, metal complex, quinophthalone, isoindolinone or quinacridone pigments.

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To improve the texture of the colourants treated according to the invention, especially or incorporation in plastics, it is possible to use assistants. Instead of using pure liquid ammonia, it is possible for example to use a solution of a suitable assistant in the liquid ammonia. When the liquid ammonia is evaporated, this assistant precipitates and coats the pigment, thereby improving the dispersibility on application. Soluble resins or plasticisers,especially sulphonamides, can be used as suitable assistants in the liquid ammonia.

An improvement in the texture can also often be attained by carrying out the process such that, after the conversion, the liquid ammonia is only partially evaporated and the residual ammonia-pigment suspension is diluted by addition of an organic solvent or water and filtered and the pigment dried. I water is used as diluent, resinic acids can additionally be dissolved in the aqueous æmmoniacal pigment suspension and the resin can be precipitated onto the pigment by spray drying or by acidification, which in turn results in an improvement in the texture.

The pigments are particularly suitable for pigmenting material of high molecular weight, for example cellulose et~ers, such as ethyl cellulose, nitrocellulose~ cellulose acetate, cellulose butyrate, natural resins or synthetic 1 ~16 8 1 ~

resins, such as polymerisation resins, polyaddition resins or condensation resins, for example aminoplasts, especially ure~/formaldehyde and melamine/formaldehyde resins, alkyd resins, phenolic plastics, polycarbonates, polyolefins, such as polystyrene, polyvinyl chloride, polyethylene, poly-propylene, polyacrylonitrile, polyacrylates, polyamides, polyurethanes or polyesters, rubber, casein, silicone and silicone resins, singly or in mixtures. It is immaterial whether the above compounds of high molecular weight are in the form of plastic masses, melts or of spinning solutions, lacquers, paints or printing inks. Depending on the end-use, it is advantageous to use the pigments as toners or in the form o preparations.

Throughout the following Examples the parts are by weight, unless otherwise stated. The relationship between parts by weight and parts by volume is the same as that between the gram and the cubic centimetre. The starting pigments of the Examples are known compounds. Wherever it is not quite clear whether the modifications are hitherto unknown or known ones, they are designated A and B and C to distinguish the difference in the modifications.

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~ ~16 8 Examples 1-19 stirring vessel cooled with dry ice is charged with 10 parts of the colourant to be treated (see $ubsequent table) and about 120 parts by volume of liquid ammonia (from a pressure flask). The mixture is stirred until the conversion to the modification is complete, which takes about 4 to 60 ~inutes The ammonia is then evaporated by heating and any traces still remaining are removed in vacuo at 100C. The ammonia-free conditioned pigment is pulverised. In addition to the improvement in the tinctorial properties obtained by the conditioning, the treated pigments also show another, in many cases new, modification. This is evident from the changed X-ray diffraction spectra. The test of the application characteristics of the resulting modifications, which often exhibit a change in shade compared with the starting colourant, reveals in many cases colouristically interesting results and often a positive change in the application properties. This also applies in particular to those cases in which the modifications obtained by the treatment with ammonia are unstable, as illustrated in Examples 22 and 23.

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1 1~6 Example 20 10 parts of the greenish-yellow pigment of the formula ~ C=u\Cll~

are treated in about 120 parts by volume of liquid ammonia by the process described in Example 1. X-ray diffraction analysis reveals that the resulting pulverised pigment has a different crystal modification compared with the starting fonm When incorporated into plasticised PVC rolled sheets, the new modification gives colourations of better hiding power than the starting form In addition to the change in crystal modification, the treatment in liquid ammonia produces a conditioning effect. Electron microscopic analysis confirms the enlarging of the crystals by the treatment with ammonia.

Example 21 10 parts of the yellow pigment of the formula Cl CH3 Cl Cl ~ N=N-~N-COHN ~ C0 ~ Cl Cl CH3 CH3 bH3 Cl 1~16813 are stirred in an autoclave with 60 parts of liquid ammonia at 50C for 1 hour. The ammonia is evaporated off a~
temperatures above 30C (valve opening on the autoclave).
Traces of ammonia still remaining are removed at about 100C
in vacuo. X-ray analysis reveals that the resulting pulver-ised pigment has a crystal modification indentical to that of the starting form. However, when incorporated into plasticised PVC rolled sheets, the pigment treated with liquid ammonia gives a colouration of substantially greater hiding power and of excellent fsstness properties. This property is attributable to the enlarging of the pigment crystals effected by the treatment with ammonia.

Example 22 10 parts of the yellow isoindolinone pigment of the formula O CH20 ~

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are treated in about 120 parts by volume of liquid ammonia by the process described in Example 1. X-ray analysis reveals that, compared with the starting form (~-modification), the resulting pigment has a different crystal modification, which shall be designated as ~-modification. Further examinations then showed that the ~-modification is unstable and, on application, is converted again into the more stable a-startirg modifi-cation, which has excellent fastness properties. However, in comparison to the untreated pigment, lacquers coloured with the ~-modification have a substantially higher colour strength while retaining the excellent fastness propertles (reconversion into the a-modification). This effect is attributable to the fact that, in the conversion into the modification effected by the treatment with liquid ammonia, a comminution of the particle si~e has occurred. D~s can be cone~m~ ~y electron microscope photographs. The conditioning effect caused by the conversion of the modification in liquid ammonia is observed to be particularly marked when the pigment is incorporated in lacquers, especially when it is incorporated in metallic pigmented paints. Up to now it has not been possible to obtain analogous colourations of such high colour strength and with these fastness properties by conditioning the a-modification by the conventional known methods, for example grinding operations.

_ 17 -_. _ 1 ~16 8 Example 23 10 parts of the a-modification of the pigment used in Example 22 are well stirred in 120 parts by volume of liquid ammonia for 20 minutes, whereupon, as described in E~ample 22, it is converted into the fine-crystalline ~-modification The ammonia is then evaporated to a volume of about 30 parts by gently warming the stirring vessel. Then 100 parts by volume of methanol are cautiously added dropwise The ammoniacal methanolic pigment suspension is well stirred for 30 minutes and thè pigment is then filtered off and the filter cake washed with methanol and dried, affording the pigment in what X-ray analysis reveals to be the more stable -modification The unstable, fine-crystalline ~-modification was converted again into the stable a-modification by stirring it in methànol. The addition of solvent also effects a reduction in the reagglomeration of the pigment particles as occurs in the process variant described in Example 22 Not only is a high colour strength on incorporation in lacquers thereby attained, but also a good dispersibility when the conditioned pigment is incorporated in plastics.

1~16~13 Example 24 7 parts o~ the yellow pigment o~ the ~ormula ~ ~ 14 and 1.8 parts of S~aybelite ~esin are stirred together for about 20 minutes in about 100 parts by volume of liquid ammonia. By cautiously warming the stirring vessel, the ammonia is evaporated to a volume o about 30 parts. The pigment suspension is then dilu~ed with 100 parts of water, stirred or 20 minutes, acidified with conc. hydrochloric acid at temperatures of 20C, stirred for 10 minutes and fi~ ered The ~ er cake is washed neutral with water and dried. The pulverised pigment, which is coated with Staybelite)Resin and reduced by the treatment with ammonia, gives very strong, brigh~ yellow colourations when incorpo-rated in lacquers and readily dispersible yellow colourations when incorporated in plastics.

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l~ample 25 10 part~s of the yellow pigment of the formula Cl~ N'N-CH-COHN~NN~=
~-o ~CH3 H

are treated in about 120 parts by volume o liquid ammonia by the process described in Example 1. X-ray and electron microscopic analyse8 of the resulting pigment reveal no change in modification, but a pronounced reduction in particle ~lze.
When incorporated for example in lacquers, it has in c~mpari-son ~o the starting pigment a substantially higher colour strength with equally good astness propertie9.

Ex~mple 26 10 par~s of the C.~, pigment Orange 59 are treated with O.S parts of benzenesulphonic acid-N-methylamide (Dellatal *
MMA, available from Bayer), in about 120 par~s by volume of liq~id ammonia by the process described in Example 1. The benzenesulphonic acid N-methylamide dissolves in the liq~id ammonia and precipitates on evaporation of the ammonia, coating the pigmen~ particles.

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1~16813 When the resulting pigment is incorporated in lacquers it gives strong, yellowish orange colourations of excellent fastness properties as a consequence of the reduction in particle size during the treatment with ammonia.

Example 27 a) 10 parts of the orange pigment (~-modification) of the fonmula H
- 02N ~ N=N-3H-COHN ~ ~ O

are treated in about 120 parts by volume of liquid ammonia by the process described in Example 1, yielding a pigment of extremely microcyrstalline structure, so that most samples appear amorphous in X-ray analysis. In indiv~dual cases, lines present in the X-ray diagram indicate a different crystal modification (modification C) as compared with the starting pigment. Incorporation in an alkyd/melamine stoving enamel yields stronger colourations compared with the starting pigment.
b) 5 parts of the pigment obtained in a~ are stirred in 60 parts by volume of o-dichlorobenzene for 18 hours at 160-165C, then filtered off and dried, yielding the pigment in a third crystal modification B. Incorporation of this _ .. , ., ~

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modification in lacquers or plastics yields strong yellow colourations of good fastness properties.
c) Repetition of the procedure described in b), but using methanol instead of o-dichlorobenzene and stirring at reflux temperature, yields the pigment again in the A modification.

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Claims (11)

What is claimed is:

1. A process for conditioning a pigment or disperse dye which comprises treating the colourant with liquid ammonia.

2. A process as claimed in claim 1, wherein the ammonia is evaporated after the treatment.

3. A process as claimed in claim 1, wherein the treatment is carried out under elevated pressure and/or at elevated temperature.

4. A process as claimed in claim l, wherein the liquid ammonia contains a dissolved assistant which precipitates on evaporation of the ammonia.

5. A process as claimed in claim 1, wherein the colourant is stirred into ammonia, filtered off, and the ammoniacal filter cake is dried.

6. A process as claimed in claim 1, wherein the treatment is carried out in the absence of water and/or an organic solvent.

7. A process as claimed in claim 1, wherein the liquid ammonia is only partially evaporated after the treatment and the colourant suspension is diluted with an organic solvent or water, filtered, and the filter cake is dried.

8. A process as claimed in claim 1, wherein the treatment is carried out in the presence of an acid resin as assistant, the liquid ammonia is only partially evaporated, the colourant/
resin suspension is diluted with water and spray dried or acidified, filtered, and the filter cake is dried.

9. A process as claimed in claim 1, wherein the treatment is carried out in the presence of a sulphonamide.

10. A process as claimed in claim 1, wherein an organic pigment is treated.

11. A process as claimed in claim 10, wherein a pigment of the isoindolinone, azo, metal complex, quinacridone and quinophthalone series is treated.