GB1600052A - Pigment composition which is easily dispersible in organic media in solid form - Google Patents

Description

(54) A PIGMENT COMPOSITION WHICH IS EASILY DISPERSIBLE IN ORGANIC MEDIA, IN SOLID FORM (71) We, ROHNER AG PRATTELN, a Swiss Corporation of Gempenstrasse 6, CH-4133 Pratteln, Switzerland, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: The present invention relates to pigment compositions, easily dispersible in organic media, in solid form, which are suitable for mass coloration of certain plastics, to a method of producing these compositions and to their use for mass coloration of plastics selected from the group consisting of acrylonitrile polymers, copolymers of acrylonitrile and vinyl chloride and/or vinylidene chloride. polyurethanes and cellulose esters as well as for production of printing inks or varnishes which can be used for the printing resp. dyeing of plastic films or sheets or metal foils or of paper.

The production of easily dispersible pigment compositions using acetone-soluble, alcohol-insoluble cellulose acetate as carrier resin as well as the use of such compositions for mass coloration or spin-dyeing of cellulose acetate of the same type as the cellulose acetate serving as carrier resin has been known for a long time. The acetone-soluble, alcohol-insoluble cellulose acetate is produced by partial saponification of completely acetylated cellulose, so-called cellulose triacetate, and is a 2.5-acetate, i.e. it contains on average 2.5 acetoxy groups per unit of glucose. The acetone-soluble, alcoholinsoluble cellulose acetate can be spun or formed into films or sheets from a solution in acetone, whereby the acetone evaporates.

Since the carrier resin of the pigment composition and the spun-dyed or masscolored material are identical. there are no compatability problems and pigment compositions of this sort, which are available on the market under the names Mikracet(8)(Ci- ba-Geigy), LuracetB (BASF), AcetofilB (Sandoz) or DA-preparations, are characterized by their easy and complete dispersibility in a spin solution and their optimum color yield. The compositions are especially adapted to use for spin-dyeing of acetonesoluble, alcohol-in-soluble cellulose acetate and are specifically suited to this purpose.

They can also be used for the spin-dyeing of cellulose triacetate, which can, for example, be spun from solution in methylene chloride, but their possibilities of use are then practically exhausted.

Pigment compositions which contain ethyl cellulose as carrier resin are said to be especially suitable, according to German "Offenlegungsschrift" No. 1,943,131, for the spin-dyeing of cellulose triacetate but are less well suited to the spin-dyeing of normal acetate rayon of 2.5-acetate.

For the spin-dyeing of polyacrylonitrile which is spun from solution in dimethyl formamide or dimethyl acetamide, the pigment compositions of the two types described above cannot be used. Therefore, for this important field of use, special pigment compositions were developed, using polyacrylonitrile as carrier resin.

However, simple mixing of the components does not produce any good pigment compositions, as can be seen from British Patent Specification No. 1,314,030. Pigment compositions of this type are on the market, for example, under the designation Mikro lithBN (Ciba-Geigy) and are specifically suitable for the spin-dyeing of polyacrylonitrile, but cannot be used for the spin-dyeing of acetate rayon in some cases, are not even suitable for the spin-dyeing of copolymers of acrylonitrile which are referred to as modacrylic fibres and which have become increasingly important during the last few years. One example of a modacrylic fibre is Teklan) (Courtaulds), a copolymer of acry lonitrile and vinylidene chloride which is spun from acetone solution.

The above mentioned pigment compositions which contain polyacrylonitrile powder as carrier resin are so specifically suited to the spin-dyeing of polyacrylonitrile that they cannot be used for example, for spin-dyeing Taklan '. Specific pigment compositions for the spin-dyeing of Teklan have not been proposed as yet. For this purpose, pigment compositions have been used according to a suggestion in British Patent Specification No. 1,284,891 - for want of a better approach - using acetonesoluble, alcohol-insoluble cellulose acetate (2.5-acetate), i.e. comDositions of the above mentioned MikracetS type. This approach is however not completely satisfactory since the carrier resin and the Teklan) are not completely miscible and compatible.The carrier resin (2.5-acetate) of the pigment composition is not dispersed completely and evenly in the fibres so that the pigment is likewise not dispersed completely and evenly in the fibres and the fibre characteristics are affected; e.g. the gloss diminishes.

For the dyeing of polyurethane -films, pigment compositions containing a mixture of carrier resins, e.g. a mixture of a nonionic substance and a synthetic resin, have been recommended as can be seen from German "Auslegeschrift" No. 2,247,188.

They are also specifically suitable only for polyurethane.

Actually then, one should have a separate assortment of pigment compositions for every plastic to be dyed which would result in high manufacturing and sales expenditure. That is whv there have been no shortage of attempts to develop pigment compositions which are suitable for masscoloration or spin-dyeing of as many different plastics as possible. Pigment compositions of this type are proposed in Swiss Patent No. 407.548 and in British Specification No. 1251157 (corresponding to German "Auslegeschrift" No. 1.904,432). The British Specification proposes a special cellulose butyrate which must be toluene-soluble and extremely organophilic. as carrier resin.

Easily dispersible pigment compositions can be used not only for the mass-coloration of plastics but also to a large extent in varnishes and printing inks. For the production of printing inks for printing on paper and similar sheet materials. for example, there are pigment compositions on the market which contain ethyl cellulose as carrier resin, under the designation Mikro lithe'A (Ciba-Geigy). The range of use of these compositions is also very limited; one cannot use them for spin-dyeing plastics except cellulose triacetate, as mentioned above. Against expectations, they are not suitable even for 2.5-acetate.

As no suitable solid pigment compositions were available, various proposals for the use of dispersions of pigments in organic solvents in which synthetic resins are dissolved or dispersed as stabilizers and thickening agents, were made. For example, US-Patent No. 2,990,291 describes dispersions of pigments in acetone containing cellulose acetate as synthetic resin. In US-Patent No.

3,376,149, dispersions of pigments in organic solvents which contain cellulose acetate butyrate are described as compositions for the mass-coloration of 2.5-acetate. US Patent No. 3,784,394 discloses dispersions of pigments in high-boiling solvents containing cellulose triacetate, and British Patent Specification No. 909,609 discloses dispersions of pigments in dimethyl formamide containing polyacrylonitrile. Such dispersions in solvents are more easily manufactured than solid pigment compositions but have a limited range of use, due already to their solvent content. In addition, they are more difficult to store and transport.

It has now been found that solid pigment compositions which comprise 30 to 70 per cent by weight of at least one inorganic and/or organic pigment in finely dispersed form with a particle size under 2 microns in intimate mixture with 70 to 30% by weight of a carrier resin which is a cellulose acetate propionate or cellulose acetate butyrate which is water-insoluble, but soluble in ethanol, and in which at least 3% of the hydroxyl groups of the cellulose are not esterified and are in free form, the said composition not containing any, or at most 55to by weight, based on the pigment, of a water-insoluble cellulose ether as additional carrier resin, have a quite unexpected range of use and give very good results.

Quite excellent results are achieved with these new compositions in the spin-dyeing of polymers and copolymers of acrylonitrile, especially of copolymers from acrylonitrile and vinyl chloride and/or vinylidene chloride, for which the known pigment compositions containing alcohol-insoluble cellulose acetate (2.5-acetate) or polyacrylonitrile as carrier resin are less or not at all suitable. In the case of Taklan which, as previously mentioned. is a copolymer of acrylonitrile and vinylidene chloride, better results are achieved than with pigment compositions containing Taklant itself as carrier resin.

For the spin-dyeing of acetate rayon (2.5-acetate), the pigment compositions of the present can be used equally as well as the known pigment compositions which contain normal alcohol-insoluble cellulose acetate (2.5-acetate). But they can be used instead of pigment compositions comprising polyacrylonitrile as carrier resin for the spin-dyeing of polyacrylonitrile from solution in dimethyl formamide, the pigment compositions according to the present invention additionally dispersing much more quickly into the viscous spinning mass than the known compositions.

The pigment compositions according to the present invention can furthermore be made. in the known way. into printing inks on the basis of other cellulose derivatives such as nitrocellulose or ethyl cellulose, and of alcohols. ketones or esters such as etha nol, propanol. methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate or 2-methoxyethyl acetate. For this purpose, they can also he combined with pigment compositions which contain nitrocellulose or ethyl cellulose as carrier resin. Metal foils, plastics and especially paper can be printed with such printing inks. Further, the pigment compositions according to the present invention can be used to produce various sorts of synthetic resin varnishes and coating masses for application of coatings.

The pigment compositions according to the present invention comprise preferably 50 to 7()',c by weight of pigment because the more concentrated the pigment composition is. the less foreign polymer will be introduced into the plastic to be dyed. However, higher pigment contents than 70% by weight are not suitable. especially in view of the redispersibility and the formation of little residues after filtration, e.g. through filter cartridges with pore diameters of for example 5 microns. As a rule it is true that the finer the pigment is, the more carrier resin is necessary to achieve good dispersi hility of the pigment in the material to be dyed.A pigment content of 50 to 60% by weight gives the best results for organic pigments, whilst higher pigment contents are possible for inorganic pigments with high specific weight In order to achieve the widest possible scope of use it is especially important that the compositions do not contain any. or only very minor amounts of. other synthetic resins. It is. for example, to be absolutely avoided that the pigment compositions contain more than 1 to 5^c by weight, based on the pigment, of ethyl cellulose, or other water-insoluble cellulose ether.

The pigment compositions according to the present invention contain preferably organic pigments or inorganic coloured or white pigments, for example carbon black, metal powders. titanium dioxide. iron oxide hvdrates or ultramarine, but especially organic pigments as for example those of the class of azo. anthraquinone, phthalocyanine, nitro, perinone. perylene. imidazole, indolinone. dioxazine, thioindigo. indigo.

pyrrocoline or quinacridone pigments. Mixtures of various pigments can also be used.

Suitable as carrier resins are. for example, partially hydrolyses acetyl propionyl or acetyl butyryl celluloses which are freely soluble in ethanol and wherein more than 3%, preferably more than 4Yc, of the hydroxyl groups of the cellulose are not esterified. Cellulose acetate propionate which is freely soluble in ethanol is particularly preferred.

Various prior art methods are suitable for the production of the pigment compositions of the present invention, in which the pigment or pigments have a particle size of less than 2 microns, preferably between 0.1 and 1 micron and are mixed as intimately as possible with the carrier resin and dispersed evenly therein. These processes, however, do not give in every case, pigment compositions of the same good quality; they require more or less expenditure and give varyingly well reproducible results. Besides various methods such as reprecipitation or air jet milling which can hardly be used on a large scale, three processes come firstly into consideration.

One of these processes is treatment with solvent and salt in a kneader according to the prior art which is used for the production of the pigment compositions on the market which contain cellulose acetate as carrier resin and which is described in detail in, for example, German "Auslegeschrift" No. 1,904,432, in fact exclusively for pigment compositions containing cellulose acetate butyrate as carrier resin. However, very expensive apparatus is necessary for this process as well as much energy, and the solution of the ecological problems connected therewith is very expensive.

The second process, which is also only suitable within certain limits, is the so-called substrate milling process, in which the pigment and carrier resin are ground together with balls or rollers in a liquid, e.g. water, until the pigment has the required fineness.

Especially with pigments which have to be ground for a long time, the carrier resin is not only mechanically crushed but also partly chemically broken down, whereby its solubility characteristics and viscosity are influenced unfavourably.

By far the most suitable for the production of the pigment compositions according to the present invention is the two-phase preparation process which has also already been proposed and used on a large technical scale. This process is first described in Swiss Patents No. 560,234. 565,210 and 557,413 (British Specification No. 1429801). Since the Pigment particles are deposited on or joined with the carrier resin particles from the organic phase of a two-phase system, one can speak of a two-phase coating or two-phase embedding process. This is much more efficient and simpler than the kneading process and gives, excluding exceptions, equally good or sometimes even better pigment compositions; probably because the carrier resin is not subjected to anv mechanical stress and is therefore "spared" to a large extent.It is remarkable. nevertheless, that normal. alcohol-insoluble cellulose acetate (2.5-acetate) and cellulose triacetate. i.e. cellulose esters, which are named in Swiss Patent No. 557.413 as examples of carrier resins, have given less good pigment compositions bv the two-phase preparation process than by the kneading process. This is even more surprising since the cellulose ethers, as e.g. ethyl cellulose, described in detail in Swiss Patent No. 557.413. when used as carrier resins for various dyestuffs and pigments give better results in the two-phase preparation and process than in the kneading process.

Therefore, it was not all to be expected that the pigment compositions according to the present invention which contain cellulose acetate propionate or cellulose acetate butyrate, which is soluble in ethanol could be produced by the two-phase preparation process with the same quality and pigment concentration as corresponding compositions which contain ethyl cellulose, and that the compositions according to the invention, when produced bv the two-phase preparation process are at least as good as those produced by the kneading process.

This is especially important technically since polyacrylonitrile. the use of which as carrier resin is described in Swiss Patents No. 536,341 and 560,234, cannot be made into perfect pigment compositions with all pigments by the two-phase preparation process. It is. however known that such compositions are difficult to produce, even by treatment with solvent and salt in a kneader and that good compositions are only obtained in small batches, using dimethyl formamide as solvent. The substrate milling process also does not give any useable compositions when using polyacrylonitrile as carrier resin, presumably because the carrier resin is damaged too much.

The two-phase preparation process for the production of pigment compositions according to the present invention comprises dispersing the pigment in the organic phase of a two-phase system comprising an aqueous phase, i.e. water optionally containing other substances. and an organic solvent having a limited solubility in the aqueous phase of at least 1% by weight, but preferably more than 1(1% by weight, treating the two-phase system which contains the dispersed pigment (or pigments) by turbulent mixing, e.g. by stirring or shaking, with the carrier resin (or resins) until a homogeneous mixture is obtained, reducing the volume of the organic phase which contains the pigment and the carrier resin by the addition of more water until the particles of the composition formed are no longer sticky and can be easily separated from the aqueous phase containing solvent, and freeing the separated particles from solvent residues and impurities by rinsing with water and then drying them. The required fine dispersion of the pigment or pigments can be achieved by "chemical" comminution (mainly reprecipitation) and/ or preferably by mechanical comminution.

Normally. one grinds the pigment or pigments in water or in the organic solvent with sand, balls or rollers and adds the second component of the two-phase system after separation of the grinding bodies, whereupon one stirs, in the carrier resin. Alterna timely the carrier resin can be added completely or partly beforehand. The carrier resin can be added in solid form, as an aqueous dispersion or dissolved and/or dispersed in the organic solvent. For operation on a commercial scale, the use of an aqueous dispersion of the carrier resin is preferred for safety reasons.

The two-phase system should contain sufficient solvent that the organic phase which contains the pigment and carrier resin, before the addition of more water, has a fluid to dough-like consistency so that completely homogeneous mixing of the pigment and carrier resin can be achieved. If one grinds the pigment in the solvent, one generally uses enough solvent to give a dispersion which has such viscosity that it can be ground. If one grinds the pigment in water and does not add the solvent until afterwards, sufficient solvent should nevertheless be used. As a rule, one uses 1 to 2 parts by volume of solvent per part by volume of pigment. In certain cases the requirement of solvent can be higher, for example if a pigment cannot be ground in a higher concentration than 10 to 20% by volume.If one grinds the pigment in the solvent, it is recommendable to saturate the solvent with water or to use recovered solvent which is generally saturated with water. Thereby, not only is a larger volume achieved but also a more stable dispersion because the solvent phase cannot take up any more water, if it is added, which could cause the pigment to flocculate. Instead, by further addition of water, solvent only passes over into the aqueous phase until the latter is saturated with solvent whereby the volume of the solvent phase is reduced.

Examples of solvents showing a limited solubility in water of at least 1% by weight which can be used in the process according to the present invention are: alcohols, ketones, esters, ethers, nitriles, aldehydes etc., such as n-butanol, isobutanol, sec.butanol, cyclohexanol, ethyl-hexanediol, phenyl methyl carbinol, methyl ethyl ketone, cyclohexanone, methoxyhexanone, diethyl ketone, methyl propyl ketone, acetylacetone, mesityl oxide, methyl acetate, ethyl acetate, propyl acetate, 2ethoxyethyl acetate, methyl acetoacetate, ethyl acetoacetate. glycol diacetate, propylene carbonate, nitromethane, nitroethane, acetaldehyde diethyl acetal, isovaleric acid. acrylonitrile, acroleine dimer, diethyl ether, furfurole, 2-hexoxyethanol and 2-phenoxyethanol.It is, however, also possible to use solvents which are completely miscible with pure water but which are not completely miscible with water which contains other substances as for example electrolytes. Examples of such solvents are ethylene carbonate. tert.-butanol, acetony lactone hydroxyacetone, diacetone alcohol and dihvdroxyacetone.

The aqueous phase of the two-phase system can not only contain salts, but also acids or bases; but it should be free of any not absolutely necessary substances or substances which could be harmful, in that they, for example. impede or even prevent the passage of the pigment and carrier resin into the organic phase of unfavourably influence a clear formation of the two-phase system, for example by emulsification. This especially concerns water-soluble dispersing agents or emulsifiers which can have this type of undesirable and harmful effect especially in high concentrations.

The state in which the dispersion of the pigment in the organic phase is present during treatment with the carrier resin, is important for the success of the treatment and a good redispersibility of the pigment composition. Many pigments have the ten dency to agglomerate or even to flocculate during the treatment with the carrier resin so that stabilizers have to be added. Besides ethyl cellulose, small, dissolved amounts of the cellulose esters which can be used according to the present invention as carrier resin. also have a stabilizing effect.An especially advantageous embodiment of the process according to the present invention comprises therefore first grinding the pigment in the organic solvent saturated with water in the presence of a small, dissolved amount of the carrier resin and adding the remainder of the carrier resin in solid form or as a concentrated. aqueous dispersion.

After the formation of a homogeneous mixture. one adds more water in portions until the particles of the composition are no longer sticks and have the desired particle size. The size of the particles can, if desired.

be hrought to the required value. by wet grinding. Then the composition is filtered off. rinsed with water and dried. If desired.

it can be ground in a centrifugal mill. sieved and optionally separated from the fines. A particle size ~ of from about 100 to 200 microns is the most advantageous. Pigment compositions containing particles of this size are non-dusting and are easy to handle and to disperse.

By simply stirring the pigment compositions according to the present invention into solutions of the plastics to be dyed, stable, deflocculated pigment dispersions are obtained, in which the pigment has the original particle size obtained by the grinding operation and which can be easily processed without trouble. The plastic solutions obtained thus can, for example, be pressed through nozzles are slits or formed into films, sheets or fibres. Alternatively, they can be processed to prints or coatings by printing or spreading on sheet materials.

In the following examples, parts are parts by weight, percentages are percentages by weight and the temperatures are given in degrees centigrade.

Example I 100 parts of chlorinated copper phthalocyanine, which has been chlorinated until the end of the chlorine-uptake, are pasted in 400 parts of sec.-butanol saturated with water, and after the addition of 1000 parts glass balls, are ground until the particle size of the pigment is below 1 micron. After removal of the glass balls, the dispersion obtained is filtered.

Experiment 1 (comparison): 3.8 parts of toluene-soluble but alcoholinsoluble cellulose acetate butyrate (CAB 551-0.2, Eastman-Kodak) are stirred into 20 parts of the dispersion and homogenized with a toothed disc mill. Then, water is slowly added, with continued stirring, until the initially dough-like mass begins to break up into granules. After further stirring, and after the addition of more water, the granules are suction filtered, thoroughly washed on the suction filter with water and dried. A fine-grained, free-flowing, nondusting pigment composition is obtained.

Experiment 2 (comparison): The procedure of Experiment 1 is repeated, using the same amount of a polymer of acrylonitrile and vinylidene chloride (Tak lan Courtaulds) as carrier resin instead of CAB 551-0.2.

Experiment 3 (according to the invention): The procedure of Experiment 1 is repeated, using the same amount of cellulose acetate butyrate (CAB 553-0.4, Eastman Kodak) which is soluble in ethanol as carrier resin instead of CAB 551-0.2.

Experiment 4 (according to the invention): The procedure of Experiment 1 is repeated, using the same amount of cellulose acetate propionate (CAP 504-0.2, Eastman Kodak) which is soluble in ethanol as carrier resin instead of CAB 551-0.2.

A 10% solution of TeklanB in acetone is prepared and 4Xc of one of the pigment compositions produced in Experiments 1 to 4. based on the TeklanB, is stirred into each of 4 portions of this spinning solution and is stirred for 15 minutes with a toothed disc mill. In this way, spinning solutions 1 to 4 are obtained. In a similar way, a spinning solution 5 is produced for comparison. This spinning solution 5 containing 4% of the commercially available pigment composition Mikracetgrün()G (carrier resin 2.5acetate, acetone-soluble, alcohol-insoluble) based on the TeklanB.

Films are formed from the spinning solutions. The films produced from spinning solutions 1 and 2 (comparison) cannot be used since they have a weak colour and the pigment is badly dispersed. The films produced from spinning solutions 3 and 4 (according to the invention) are clearly better than the films produced from spinning solution 5 (commercially available pigment composition, comparison). The film produced from spinning solution 4 (pigment composition of Experiment 4) has the highest colour-strength and the best dispersion of the pigment in the film.

Example 2 20 parts of flavanthrone (Indanthrene t) Yellow G) are ground in 80 parts water containing 0.2 parts of a condensation product of naphthalenesulphonic acid and formaldehyde (Tamol (' NNOK, BASF, Rohm & Haas) together with 200 parts glass beads of I mm diameter until the particle size of the pigment is substantially smaller than 1 micron. After removal of the glass balls and filtering, the dispersion is mixed with 80 parts of a dispersion of 13.3 parts ethanolsoluble cellulose acetate propionate (CAP 504-0.2, Eastman-Kodak) in 80 parts sec.butanol saturated with water until the aqueous phase is clear and colourless. Then the two-phase mixture is mixed by vigorous stirring with 200 parts water and is further stirred until fine-grain granules are formed.

The mixture is allowed to settle, the supernatant is decanted and the liquid removed is replaced by the same volume of water; the mixture is allowed to stand for an hour with gentle stirring and then suction filtered. The granules so obtained are washed with water and dried at 60 in vacuo.

The pigment composition can be completely and evenly dispersed by stirring for 10 minutes with a toothed disc mill in a 10% solution of cellulose acetate in acetone, a 100(', solution of Teklant) in acetone, a 10% solution of cellulose triacetate in methylene chloride or a 10% solution of polyacrylonitrile in dimethylformamide. The spinning solutions obtained thus can be formed into yellow-coloured films, sheets or fibres.

If one uses, instead of flavanthrone, the same amounts of Permanentyellow HR (Hoechst), Irgalith Yellow F4G (Ciba Geigy) or Irgalith 8 Yellow BKW Ciba- Geigy), pigment compositions with similarly good characteristics are obtained.

If one stirs one of the pigment compositions obtained above into an alcoholic solution which contains a combination of nitrocellulose and ethyl cellulose as filmformer, a yellow printing ink is obtained with which one can produce good, yellow prints on paper.

Example 3 20 parts of chlorinated copper phthalocyanine which has been chlorinated until the end of the chlorine-uptake, and 1 part ethyl cellulose are ground in 80 parts 2ethoxyethyl acetate with 200 parts of sand until the particle size of the pigment is smaller than 1 micron. Then the grains of sand are removed, the dispersion is filtered and 19 parts ethanol-soluble cellulose acetate propionate (CAP 504-0.2, Eastman Kodak) are stirred in. Then 200 parts water are added while the mixture is well stirred, and after addition of a further 200 parts water the mixture is granulated in a Turmix 8-household mixer (having a rotating ring of knives). The supernatant is decanted, the residue is allowed to stand for some time with a further 200 parts water, and the granules are filtered off on a suction filter, washed with water and dried.

A green pigment composition with similarly good characteristics as the compositions obtained in Experiments 3 and 4 of Example 1 is obtained. Instead of chlorinated copper phthalocyanine, unchlorinated copper phthaloeyanine can also be used.

Good pigment compositions are also obtained with carbon black (Printex8300, Degussa), with titanium dioxide and with iron oxide hydrate according to this procedure.

Example 4 30 parts copper phthalocyanine are ground in 70 parts water containing 1 part Tamol NNOK (BASF, Rohm & Haas) and, as described in Example 1, are treated with a dispersion of 15 parts ethanol-soluble cellulose acetate propionate (CAP 504-0.2 Eastman-Kodak), in 80 parts Pentoxone (4-methoxy-4-methyl-2-pentanone, Shell) saturated with water. One obtains blue, fine granules with good dispersibility in organic media.

If, in the above Example, one uses ethyl acetoacetate, acetylacetone or isobutanol instead of Pentoxone(g), one obtains similarly good pigment compositions.

Example 5 20 parts N,N'-diethyl- perylenetetracarboxylic acid diimide and 2 parts ethanol-soluble cellulose acetate propionate (CAP 504-0.2, Eastman-Kodak) are ground in 80 parts tert.-butanol with 200 parts sand until the particle size of the pigment is 1 micron. The sand is removed and the dispersion filtered. Further 11.3 parts CAP 504-0.2 are stirred into the dispersion. Then 200 parts of an aqueous 5% sodium chloride solution are slowly added while the dispersion is well stirred.

The supernatant is poured off, fresh water is added, the granules are filtered off with a suction filter. the solvent and salt residues are removed by washing with water and the granules are dried. The fine-grained, red powder so obtained is well dispersible.

If one uses instead of the above pigment, Cromophtal$)Red BR (Ciba-Geigy) or quinacridone. one obtains a more yellowish resp. more bluish red pigment composition.

If one replaces the carrier resin CAP 504-0.2 in the above example by the same amount of ethanol-soluble cellulose acetate butyrate (CAB 553-0.4. Eastman-Kodak), equally good pigment compositions are obtained.

WHAT WE CLAIM IS: l. A pigment composition which is easily dispersible in organic media, in solid form. comprising 30 to 70 percent by weight of at least one inorganic and/or organic pigment in finely dispersed form with an average particle size under 2 microns in intimate mixture with 70 to 30 percent by weight of a carrier resin which is a cellulose acetate propionate or cellulose acetate butyrate which is water-insoluble, but soluble in ethanol, and in which at least 3% of the hydroxyl groups of the cellulose are not esterified and are in free form, the said composition not containing any, or at most 5% by weight, based on the pigment, of a water-insoluble cellulose ether as additional carrier resin.

2 A composition according to claim 1 in which the pigment has an average particle size of 0.1 to 1 micron.

3. A composition according to claim 1 or 2 which comprises 40 to 60 percent by weight of the pigment and 60 to 40 percent by weight of the cellulose ester.

4. A pigment composition as claimed in claim 1 substantially as hereinbefore descnbed in any one of Examples 1 (experiment 3 or 4), 2 3, 4, or 5.

5. A process for the preparation of a composition according to any one of claims 1 to 4, which comprises dispersing the pigment in the organic phase of a two-phase system comprising an aqueous phase, and an organic solvent having a limited solubility in the aqueous phase of at least 1 percent by weight, treating the two-phase system which contains the dispersed pigment by turbulent mixing with the carrier resin until a homogeneous mixture is obtained, reducing the volume of the organic phase which contains the pigment and the carrier resin by the addition of more water until the particles of the composition formed are no longer sticky and can be easily separated, rinsing the separated particles with water, and drying them.

6. A process according to claim 5 substantially as herein before described,.

7. A composition according to claim 1 when prepared by the process of claims 5 or 6.

8. A process for the mass-coloration of plastics selected from acrylonitrile polymers, copolymers of acrylonitrile and vinyl chloride and/or vinylidene chloride, polyurethanes and cellulose esters, which comprises incorporating therein a composition according to any one of claims 1 to 4 or 7.

9. A process according to claim 8, in which acrylonitrile polymers or copolymers of acrylonitrile and vinyl chloride and/or vinylidene chloride are dyed.

10. A coloured article of manufacture, produced by the process of claims 8 or 9.

11. Printing ink or varnish based on an alcohol, ketone, ester or a mixture of such solvents, produced from a composition according to any one of claims 1 to 4 or 7.

12. An article of manufacture, coloured or printed with a printing ink or varnish according to claim 11.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   Example 5

   20 parts N,N'-diethyl- perylenetetracarboxylic acid diimide and 2 parts ethanol-soluble cellulose acetate propionate (CAP 504-0.2, Eastman-Kodak) are ground in 80 parts tert.-butanol with 200 parts sand until the particle size of the pigment is 1 micron. The sand is removed and the dispersion filtered. Further 11.3 parts CAP 504-0.2 are stirred into the dispersion. Then 200 parts of an aqueous 5% sodium chloride solution are slowly added while the dispersion is well stirred.

   The supernatant is poured off, fresh water is added, the granules are filtered off with a suction filter. the solvent and salt residues are removed by washing with water and the granules are dried. The fine-grained, red powder so obtained is well dispersible.

   If one uses instead of the above pigment, Cromophtal$)Red BR (Ciba-Geigy) or quinacridone. one obtains a more yellowish resp. more bluish red pigment composition.

   If one replaces the carrier resin CAP 504-0.2 in the above example by the same amount of ethanol-soluble cellulose acetate butyrate (CAB 553-0.4. Eastman-Kodak), equally good pigment compositions are obtained.

   WHAT WE CLAIM IS: l. A pigment composition which is easily dispersible in organic media, in solid form. comprising 30 to 70 percent by weight of at least one inorganic and/or organic pigment in finely dispersed form with an average particle size under 2 microns in intimate mixture with 70 to 30 percent by weight of a carrier resin which is a cellulose acetate propionate or cellulose acetate butyrate which is water-insoluble, but soluble in ethanol, and in which at least 3% of the hydroxyl groups of the cellulose are not esterified and are in free form, the said composition not containing any, or at most 5% by weight, based on the pigment, of a water-insoluble cellulose ether as additional carrier resin.
2. 2 A composition according to claim 1 in which the pigment has an average particle size of 0.1 to 1 micron.
3. 3. A composition according to claim 1 or 2 which comprises 40 to 60 percent by weight of the pigment and 60 to 40 percent by weight of the cellulose ester.
4. 4. A pigment composition as claimed in claim 1 substantially as hereinbefore descnbed in any one of Examples 1 (experiment 3 or 4), 2 3, 4, or 5.
5. 5. A process for the preparation of a composition according to any one of claims 1 to 4, which comprises dispersing the pigment in the organic phase of a two-phase system comprising an aqueous phase, and an organic solvent having a limited solubility in the aqueous phase of at least 1 percent by weight, treating the two-phase system which contains the dispersed pigment by turbulent mixing with the carrier resin until a homogeneous mixture is obtained, reducing the volume of the organic phase which contains the pigment and the carrier resin by the addition of more water until the particles of the composition formed are no longer sticky and can be easily separated, rinsing the separated particles with water, and drying them.
6. 6. A process according to claim 5 substantially as herein before described,.
7. 7. A composition according to claim 1 when prepared by the process of claims 5 or 6.
8. 8. A process for the mass-coloration of plastics selected from acrylonitrile polymers, copolymers of acrylonitrile and vinyl chloride and/or vinylidene chloride, polyurethanes and cellulose esters, which comprises incorporating therein a composition according to any one of claims 1 to 4 or 7.
9. 9. A process according to claim 8, in which acrylonitrile polymers or copolymers of acrylonitrile and vinyl chloride and/or vinylidene chloride are dyed.
10. 10. A coloured article of manufacture, produced by the process of claims 8 or 9.
11. 11. Printing ink or varnish based on an alcohol, ketone, ester or a mixture of such solvents, produced from a composition according to any one of claims 1 to 4 or 7.
12. 12. An article of manufacture, coloured or printed with a printing ink or varnish according to claim 11.