CA1057905A - Dyestuff preparations for transfer printing - Google Patents

Abstract

Abstract of the Disclosure DYESTUFF PREPARATIONS FOR TRANSFER PRINTING

Dyestuff preparations for the transfer printing are described which consist preferably only of at least one dyestuff suitable for the transfer printing process, es-pecially a dispersing dyestuff the particle size of which dyestuff is less than 15µ, preferably less than 5µ, or smaller, and which preparations are free from carrier and binder.

Description

~057905 The invention relates to a method of preparing printing inks or pastes which are suitable for transfer printing and to the print-ing inks or pastes so prepared.
It is known that dyestuff preparations for transfer print-ing, by which is meant the thermal transfer of sublimable dyestuffs from a carrier material to textile sheet materials, can be produced by a process in which a dyestuff suitable for the transfer printing process, together with about 25 to 50% of a suitable carrier, e.g. a cellulose derivative, and of a dispersing agent, is ground down by wet grinding or kneading, e.g. dispersion kneading, to obtain a particle size of about 0.01 to 2,u, with, however, the particle size mentioned rendering necessary the presence of fairly large proportions of protective colloids in order to avoid an agglomeration of the fine dyestuff particles in the printing ink.
It has now been found that, surprisingly, it is also possi-ble to employ dyestuff preparations consisting of pure dyestuff (the term "dyestuff" is to be understood, here and in the following, as denoting also the optical brighteners.

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since from the point of view of application and of the objective - modification of the coloristic appearance of a substrate - there exists no fundamental dif-ference), optionally together with small amounts of diluting agents and/or wet-ting agents, for the preparation of printing pastes for transfer printing, pro-vided that the particle size of the dyestuff has been reduced by a suitable grinding operation to < 15 ~. The invention relates therefore to dyestuff pre-parations, usable in the transfer printing process, which are free from carriers and binders.
According to one aspect of the invention, therefore, there is pro-vided a method of preparing a printing ink or paste which is suitable for trans-fer printing, which method comprises dispersing in water or an organic liquid suitable for use in a printing ink or paste a dyestuff or a dyestuff prepara-tion containing at least 95% by weight of dyestuff and up to 5% by weight of a diluting or wetting agent, based on the weight of the preparation, the dye-stuff having a particle size less than 15 ~ and the volatility of the dyestuff being such that at atmospheric pressure and at a temperature of from 160 to 220C. at least 60% by weight of the dyestuff is vapourised in less than 60 seconds.
According to another aspect of the invention there is provided a printing ink or paste which is suitable for transfer printing which comprises a dyestuff or a dyestuff preparation containing at least 95% by weight of dyestuff and up to 5% of a diluting or wetting agent, based on the weight of the prepara-tion, the dyestuff having a particle size less than 15 ~ and the volatility of the dyestuff being such that at atmospheric pressure and at a temperature of from 160 to 220C at least 60% by weight of the dyestuff is vapourised in less than 60 seconds.
Suitable dyestuffs and optical brighteners for the process of the invention are all those which are suitable for the transfer printing process i.e. those which at atmospheric pressure are converted at between 150 and 220C

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~OS7905 into the vapour state, which are stable on heating, and which can be trans-ferred undecomposed.

The products concerned are, for example, salts of cationic dye-stuffs with acids having a pKs-value of > 3, which advantageously are trans-ferable undecomposed up to 190C.
In the case of these cationic dyestuffs, they are quite generally chromophoric systems of which the cationic character is due to a carbonium, ammonium, oxonium or sulphonium grouping. Examples of such chromophoric systems - 3a -, ~ .

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are: methine~ azomethine, hydrazone, azine, oxazine~ thiazine diazine, acridine, xanthene, polyarylmethane, such as diphenylmethane or triphenylmethane, and coumarin dyestuffs;
also arylazo~ phthalocyanine and anthraquinone dyestuffs having an external ammonium group, for example, a cyclo-ammonium or alkylammonium group. The cationic optical brighteners concerned are, in particular, those from the methine, azomethine, benzimidazole, coumarin, naphthalimide or pyrazoline series.
The cationic dyestuffs mentioned are used in the form of their salts with acids of which the p~ -value is greater than 3. Suitable acids of which the pK -value is greater than 3 are both inorganic and organic acids.
Suitable also are, for example: metal complex dyestuffs such as are described in the British Patent No. 1,320,819, reactive dyestuffs as described in the British Patent No. 1,254,021 and vat dyestuffs as described in German Offenlegungsschrift 1,635,382.
Preferably used, however, are disperse dyestuffs and optical brighteners without water-solubilising groups. These can belong to the most varied classes, for example, to the azo or anthraquinone series; likewise suitable however are quinophthalone dyestuffs, nitro dyestuffs, azomethine dyestuffs styryl dyestuffs and so forth. It is advantageous to use such dyestuffs which are converted under atmospheric pressure at a temperature of between 160 and 220C, by sublimation or evaporation, to the extent of at least 60% in less than 60 seconds into the vapour phase. Such dyestuffs which may be mentioned are, for example, the monoazo dyestuffs of the formula OH
N ~

CO-Y X
wherein X and Y each represent an alkyl radical having 1 to 4 carbon atoms - OH

\C - N
H3 C~13 .

and NO
1 2 ~CO - CH
~ N = N - CH 3 H3C \CO - NH

. . ..

1~)57905 and above all the quinophthalone dyestuff of the formula C
. OH
and the anthraquinone dyestuffs of the formulae O ~H-X

O ~H-X
(X = alkyl having 1 to 4 carbon atoms~, ~o~3 O - OR

(R = alkyl having 3 to 4 carbon atoms) .. . . . , .......... , .. . . ., . : .
.. . ..

,-, ;,, ' O NilCII

O NH

O NH
)J~

. o ~1 - z (Z = cyclohexyl or phenyl), and also the brominated or chlor-nated 1,5-diamino-4,8-dihydroxyanthraquinones.

Among the optical brighteners without water-solubilising groups, there may be mentioned, for example, those from the series of benzazoles (derivatives of mono-/bis-benzoxazole or benzimidazole), v-triazoles (derivatives of triazolyl, benztriazolyl or naphthtriazolyl), co~arins (e.g., derivatives of 3-phenylcoumarin), distyrylbenzenes, distyrylbiphenyls, 1,3-diphenylpyrazolines, 4-alkoxy- and 4,5-dialkoxynaphthalimides, derivatives of styryl and stilbenyl, as well as pyrene derivatives.

10~'7~(~5 A further impor~ant factor is the choice of dyestuffs in dyestuff combinations, for only dyestuffs which are alike, or close together, wlth respect to their sublimation temperature should be combined, such as, e.g., specific disperse dyestuffs with specific cationic dyestuffs.
All these dyestuffs are known and can be produced by kno~m methods.
According to the present invention, these dyestuffs are-ground until they have a particle size within the range of <15,u, especially ~ 5,u. This can be achieved, for example, by dry grinding, advantageously in an air-jet mill.
A short wet grinding is however preferred in order, in particular, to obtain a fineness of at least S ~ or less, but not the very high degree of fineness of the known preparations.
lS This wet grinding operation may be performed in any suitable mill, such as in a wet ball mill or in a "Dynomuhle". Wet grinding can be carried out with an aqueous, aqueous/organic or organic liquid medium. The presence of about 1 to 5%~
relative to the amount of dyestuff, of a customary dispersing

2~ agent, which has the function of a deflocculating agent and which is intended to prevent agglomerating, is in general advantageous. This dispersing agent should dissolve both in water and in organic solvents. Whether a nonionic, anionactive or cation-active dispersing agent is used, depends on the .
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1~57~5type of dyestuff. For example, an anion-active dispersing agent is used for disperse dyestuffs, and a cation-active dispersing agent for cationic dyestuffs. The dyestuffs are separated from the resulting dispersion, for example, by means of a two-phase granulation, such as is described in DT-OS 2,412,369. The employed dispersing agent remains behind in the liquid phase, and is not present in the finished granulate or present only to the extent of traces.

To these finely ground dyestuffs, there can be optionally added dilutlng agents in an amount of from about 0.1 to 5%, relative to tlle amount of dyestuff. These diluting agents are used principally for the adjustment of the tinctorial strength and to obtain constancy of shade. There can however also be added wetting agents, which improve the wetting of the dyestuffs.

There are obtained in all cases dyestuff preparations having a content of dyestuff exceeding 95%; however, those preparations consisting of pure dyestuff, i.e. 100% dyestuff, are preferred.

These carrier-free dyestuffs, optionally containing diluting agents and/or wetting agents and ground down to a particle size of ~15,u, are subsequently used, either in the form of powders or in the form of granules produced _ g _ 1~5~
therefrcm in the known manner, together with a thickener, with water alone or in a mixture of water and organic solvents, such as ethyl alcohol, ethylene glycol, toluene or white spirit, or free from water in pure organic solvents, for the preparation of printing pastes or printing inks;
these are then used for the printing of carrier materials which, in their turn, are employed in the transfer printing process.
The thickener required for the preparation of printing pastes and printing inks should be stable up to 230C, and should act as thickening agent for the printing mixture, and, at least temporarily, as a binder of the dyestuff on the carrier to be printed. Suitable thickeners are synthetic, semi-synthetic and natural resins, these being polymerisation products and also polycondensation and polyaddition products.
There can be used in principle all the resins and thickeners commonly employed in the industries producing paints and varnishes and printing inks and pastes. The thickeners should not melt at the transfer temperature, should not react chemically in air or with themselves (e.g., cross-linking), should have little or no affinity for the dyestuffs used, merely retaining these on the printed area of the inert carrier without modifying them, and should remain behind completely on the carrier after the thermal transfer process. The .
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thickenrs preferred are those which are soluble in organic solvents, and which rapidly dry, for example in a warm stream of air, and form a fine film on the carrier. Suitable water-soluble thickeners which may be mentioned are: alginate, tragacanth, carubin ~from locust bean flour) dextrin, mucilage etherified or esterified to a greater or lesser degree, hydroxyethylcellulose or carboxymethylcellulose, water-soluble polyacrylamides and polyacrylates and, in particular, polyvinyl alcohol; and suitable thickeners soluble in organic solvents are: cellulose esters, such as nitrocellulose, cellulose acetate or cellulose butyrate, and especially cellulose ethers, such as methyl, ethyl, propyl~ isopropyl, benzy], hydroxypropyl or cyanoethyl cellulose, as well as mixtures thereof.

For the improvement of the ready-for-use property of these printing pastes, optional constituents may be added, such as softening agents, swelling agents, high-boiling 1~ ~etr~ JecQ//n solvents, such as Tetrali~ or Dcltali~, ionic or nonionic, surface-active compounds, such as, for example, the condensation product of 1 mole of octylphenol with 8 to 10 moles of ethylene oxide. These printing pastes (solutions, dispersions, emulsions) are produced by processes known per se, wherein the dyestuffs as defined are, e.g. dissolved or dispersed in water andJor solvent or solvent mixture, or are produced in situ, 579(~5 advantageously in the presence of a thickener which is stable up to 230GC.

The carrier materials printed with such printing pastes are ~nown, and consist advantageously of a flexible sheet S material that is preferably dimensionally stable, such as a strip, band or sheet, preferably having a smooth surface.
These carrier materials must be s~able to heat, and they are made of the most varied types of materials, particularly non-textile materials, such as, for example, metal, such as an aluminium or steel sheet; or they consist of a con~inuous strip of stainless steel, plastics or paper, preferably of a clean, non-lacquered cellulose parchment paper, which is optionally coated with a film of vinyl resin, ethylcellulose, polyurethane resill or Teflon.

The optionally filtered printing pastes or printing inks are applied to the carrier material, in places or over the whole surface, by, for example, spraying, coating or, advantageously, printing. There can also be applied to the carrier material a multi-coloured pattern, or the carrier material can be printed with a ground shade and thereafter successively with identical or different designs. After application of the printing paste to the carrier material, this is dried, e.g., with the aid of a warm flow of air or by infra-red irradiation.

~5'~ ~5 The carrier materials can be printed also on both sides, whereby it is possible to select different colours and/or designs for the two sides. In order to avoid the use of a printing machine, the printing pastes can be sprayed onto the carrier materials by means, for example, of a spray gun. Particularly interesting effects are obtained when simultaneously more than one shade is printed or sprayed on the carrier material. Specific designs can be obtained, e.g., by the use of stencils, or artis~ic designs can be applied by brush. If the carrier material is printed, then the most diverse printing processes may be employed, such as high-pressure processes (letter~press prirlting, flexographic printing), gravure printing (e.g., roller printing), screen printing (e.g., rotary printing or film printing) or electrostatic printing processes.
The carrier-free dyestuff preparations of the invention are weak with regard to the tinctorial strength on the carrier material, but they develop after the performance of the transfer operation to produce a good tinctorial strength and yield.
The transfer is effected in the usual malmer by the action of heat. For this purpose, the treated carrier materials are brought into contact with the materials to be printed, especially textile materials, and are held at about 120 to Y

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210C until the defined dyestuffs applied to the c~rrier material have been transferred to ~he textile material.
As a rule, 5 to 60 seconds are sufficient to achieve this.

The action of heat can be applied by various known methods, for example, by passage over a hot hea~ing cylinder, by passage through a tunnel-shaped heating zone, or by means of a heated roller, a~vantageously together with a pressure-exerting, heated or unheated counter roller, or by means of a hot calender, or with the aid of a heated plate, optionally under vacuum, which devices are preheated to the required temperature by steam, oil, infra-red irradiation ~r microwaves, or which are located in a preheated heating chamber.

After completion of the heat treatment, the printed material is separated from .he carrier. This material requires no aftertreatment, neither a steam treatment to fix the dyestuff, nor a washing to improve the fastness properties.

For printing with the transfer process, all s~nthetic fibres are basically suitable, provided ~hat their thermo-stability with respect to the process is sufficient. Suitablematerials in practice are polyester, polyacrylonitrile and polyamide fibres, cellulose-2 1/2- and -triacetate fibres, and mixtures of these with each other, or mixtures of cellulose fibres-or albumen fibres.

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' , ' ' " ~ ' ' ~ ~, ' ' ' ' ~0579(~5 The use according to the invention of the solid dyestuff preparations preferably consisting of 100% dyestuff compared with that of known carrier-containing dyestuff preparations having a dyestuff con-tent of about 50 to 75%, which are already in use commercially, has the following outstanding advantages:
a) An appreciably greater universal possibility of application in the various printing processes. The carrier-free preparations can be dis-persed in the respective applied medium by means of ordinary commercial intensive stirrers. The dyestuff preparations at present known for trans-fer printing are, on the other hand, not universally applicable, but are designed only for the production of a specific printing-paste composition.
b~ They render possible an increase in concentration or a correction of printing pastes already prepared, without noticeably raising their viscosity. This property of the preparations produced according to the invention can in practice be of great advantage, in that unused stocks of printing pastes can be incorporated.
c) Lower dyestuff losses in the transfer process. In the case of print-ing on more highly absorbent carrier materials, for example, on porous paper, the dyestuff that is more coarsely - , ~ . : ' : ' , : : , -.. , . . : ,, - '"

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dispersed compared with the known preparations is deposited preferably only on the surface. It cannot therefore be carried by the solvent of the printing paste into the pores of the carrier layer to the extent that the hitherto customary, very finely dispersed preparations are carried into the pores. By virtue of this fact, there can be obtained in the case of thermal transferring higher colour yields on the fabric.

d) Possibility of the production of printing pastes having an extremely high content of dyestuff, in consequence of the absence in the preparation of polymer carriers which raise the viscosity.

e) As a result of the absence of additives increasing viscosity, such as are constituted, e.g., by the carrier materials or binders normally contained in transfer preparations, it is possible, since no increase in viscosity occurs, to allow the operating speed to increase to double the hither~o usual operating speed, a factor which results in an increase of the production of printed carriers with the same machine.

With the dyestuff preparations usable according to the invention, there are obtained in the transfer printing process very finely detailed designs and patterns having fine indentations, which can be reproduced sharply outlined in practically any shade of colour. An overlapping of the colours .. ..
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at the edges of the designs does not occur. Besides patterned printings, also plain printings are possible, and thes2 are particularly suitable for the covering of materials which dye streakily.
S These carrier-free dyestuff preparations have a preferred use for, in particular, the production of dark shades, such as nigger brown, dark blue and black, and also for the treatment of carpet materials, since they ensure a high deposition of colour.
The following examples illustrate the invention, without its scope being limited by them. Where not otherwise stated, the term 'parts' denotes parts by weight.

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~sy~os A. Production of the dyestuff preparations Example 1 1000 parts of the dyestuff of the formula ' ~

are ground in an air-jet mill under normal pressure conditions (5-6 atmospheres) until an upper limit of the particle-size distribution of 10 to 15 ,u maxim~. is attained.
There is obtained a dyestuff preparation (powder) which consists of 100% dyestuff.

Example 2 1000 parts of the dyestuff according to Example 1 are ground together with 20 parts of cellulose ethyl ether (Ethocel E 7) in an air-jet mill under normal pressure conditions until an upper limit of the particle-size distribution of about 10 to 15 ~ is attained:

There is obtained a dyestuff preparation (powder) which contains 98% of dyestuff.

Example 3 1000 parts of the dyestuff according to Example 1 are ~Je ~r~

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~ 0~79 0 5 ground together with 10 parts of sodium-isopropylnaphthalene-sulphonate (Aerosol OS) in an air-jet mill, under normal pressure conditions, until an upper limit of the particle-size distribution of about 10 to 15,u is attained.
There is obtained a dyestuff preparation (powder) which contains 99% of dyestuff.

- Example 4 1000 parts of the dyestuff according to Example 1 is ground together with a m xture of 20 parts of cellulose ethyl ether (Ethocel E 7) and 10 parts of sodium-isopropyl- t naphthalenesulphonate (Aerosol OS) in an air-jet mill, under normal pressure conditions, until an upper limit of the particle-size distribution of about 10 to 15 ~u is attained.

There is obtained a dyestuff preparation (powder) which contains 97% of dyestuff.

Example 5 If, instead of the dyestuff according to Examples 1 to 4, identical amounts of the dyestuff of the formula OH
are used under otherwise the same grinding conditions, then

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there are obtained a dyestuff having an upper limit of the particle-size distribution of about 10 to 15,u, and preparations (powders) having a content of dyestuff of between 97 and 100%.

Example 6 If, instead of the dyestuff according to Examples 1 to 4, identical amounts of the dyestuff of t:he formula are used under otherwise the same grinding conditions, then there are obtained a dyestuff having an upper limit of the particle-size distribution of about 10 to 15~u, and preparations (powders) having a dyestuff content of between 97 and 100%.

Example 7 If, instead of the dyestuff according to Example 1, identical amounts of the optical brightener of the formula ~ ~ CH = CH-; ,~
', ' ' ~ ' ' 1~7S~0S

are used, under otherwise tlle same grinding conditions, then there is obtained an optical brightener having an upper limit of the particle-size distribution of about lO,u.

There is thus obtained a preparation (powder) consisting of 100% of opcical brightener.

t Example 8 10 parts of a dyestuff preparation obtained according to Examples 1 to 6 are added to 20 parts of water, whereupon 6 parts by volume of ethyl ace~ate are added with vigorous shaking. After 10 minutes' shaking, there are obtained spherical granules of 0.2 to 1 mm diameter, which are separated from the two-phase system by means of a sieve and then dried.

There are obtained free flowing, non-dusty dyestuff preparations readily dispersible in a printing paste, which preparations have a dyes~uff content of between 97 and 100%
and which are in the form of mechanically stable granules.

Example 9 30 parts of the dyestuff of the formula ,o~

O OH

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~ (~579(~5 are ground, in a continuous stirrer ball mill, with 70 parts of water and 1 part of hydroxypropylcellulose until the particle size is smaller than 15 microns, essentially about 1 to 5 microns.
There are added, with stirring, 21 parts of isobutyl alcohol to the grinding suspension, and the dyestuff is caused to agglomerate. After a short time, there are obtained spherical granules of 0.2 to 1 mm diameter, which are separated from the suspension by a sieve, and subsequently dried. The resulting dyestuff preparation is a granulate consisting of practically 100% of dyestuff with slight traces of hydroxypropylcellulose. The granulate obtained is non-dusty and mechanically stable. When introduced into a printing ink, it wets very readily, and can be dispersed with a dispersing device into the separate particles which have a particle size of below S microns.

Example 10 30 parts of the dyestuff of the formula O ~H
~¢~

are ground, ir~ a continuous stirrer ball mill, with 80 parts , ' of watcr and 1 part of hydroxypropylcellulose until the particle size is below 15 microns~ essentially about 1 to 5 microns. There are then added, with stirring, 23 parts of ethyl acetate to the grinding suspension, and the dyestuff S is brought into the agglomerated state. After a short time, there are obtained spherical granules of 0.2 to 1 mm diameter, which are separated from the suspension by means of a sieve, and subsequently dried. The dyestuff preparation thus obtained is a granulate consisting of practically 100% of dyestuff with slight traces of hydroxypropylcellulose. It wets very rapidly in a printing ink, and can be readily dispersed by a normal dispersing stirrer into its separate particles.

Example 11 An aqueous dyestuff press cake containing 30 parts of the dyestuff of the formula ~/C~

, OH

is ground in a 'Permill' with 100 parts of water until the particle size is smaller than 15 microns, essentially about 1 to 10 microns. There are added, with stirring, 20 parts of ethyl acetate to ~he grinding suspensi~n (after separation "~ f~ e t~

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.

~79~15 of the glass beads used for grinding), and the dyestuff is caused to agglomerate. There are obtained after a short time spherical granules of 0.2 to 1 mm diameter, which are separated from the suspension by means of a sieve, and then dried. The dyestuff preparation thus obtained consists of granules of pure (lOOa/o) dyestuff.

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B App] ication o, the dyestuEf preparations accordin~ to A
for the preparation of printin~ pastes for the transfer-pr;ntin~; process.
Example 12 20 parts of a dyestuff preparation obtained according to Examples 1 to 8 are dispersed by means of a stirrer, within 5 minutes, in a solution of 8 parts of ethylcellulose in 72 parts of a mixture of methyl ethyl ketone and ethanol (1:1). The aggregated dyestuff particles wet very rapidly and disperse spontaneously into the primary particles. The result is a printing paste, for gravure printing, having a viscosity of 22 seconds (Ford cup 4), which printing paste is suitable for the printing of paper for the transfer printing process.

Example 13 10 parts of a dyestuff preparation obtained according to i5 Examples 1 to 8 are dispersed within 5 minutes, by means of a stirrer, in a solution of 22 parts of Versamid 930 (Schering), 1 part of AC Polyethylene 6A (Allied Chemical), 1 part of Stabiliser XE-35 (Schering) and 0.1 part of silicone oil SISS 200-350 (Soc. Ind. des Silicones) in 69.9 parts of a solvent mixture isopropanol/benzine (1:1). The result is an agglomerate free printing paste having a viscosity of , , ' .
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.

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~s~ s 34 seconds (Ford cup 4), which can be printed perfectly satisfactorily by flexographic printing on paper; this paper can then be used in the transfer printing process by placing the paper with a piece of tufted carpet made from polyester fibres for 30 seconds in a press heated to 210C, and subsequently removing the paper. There is obtained on the carpet an extremely clear and strong printing.

Example 14 A completely disaggregated dispersion having a viscosity of 32 seconds (Ford cup 4), which is very suitable or flexographic printing on paper, is obtained after 5 minutes by the stirring in each case of 15 parts of the air-jet-ground dyestuff preparations produced according to Examples 1 to 8 A into a solution of 3 parts of Cibamin M 86 (Ciba-Geigy) and 9 parts of Mowital B30M (Hoechst) in 73 parts of 96% denatured alcohol by means of an Ultra-Turrax stirrer. The printing paste can, by an increasing of its concentration with the sa~e finely dispersed dyestuff preparations, be adjusted to have a content of 30% and more, without any appreciable change in viscosity.

Example 15 8 parts of a dyestuff preparation obtained according to Examples 9 to 11 are dispersed by means of a Homorex stirrer, within 10 minutes, in a solution of 8 parts of ethylcellulose ~ra~ ~4~`k - .
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~57~(~5 in 84 parts of ethanol. The result is a printing paste having a viscosity of 21 seconds (Ford cup 4), which is suitable for the printing of paper for the transfer printing process.

Example 16 23 parts of a dyestuff preparation obtained according to Examples 9 to 11 are dispersed by means of an Ultra Turax stirrer, within 4 minutes, in a solution of 2 parts of ethylcellulose in 75 parts of ethanol. The dyestuff preparations wet very well, and rapidly disperse into the primary particles. There results a printing paste having a viscosity of 21 seconds (Ford cup 4), which is suitable for the printing of paper for the transfer printing process.

Example 17 S parts of the crystalline dyestuff of the formula O NH-CH

and 5 parts of the crystalline dyestuff of the formula O ~

H

. . . . -- : ' . ~ '' -'"' . . . ' . ' ' ' .

1~)575~05 are ground, jointly in a glass-bead mill or sand mlll, in denatured ethanol in the presence of 4 parts of ethyl-cellulose until the particle size is reduced to about 2~u and smaller. After removal of the grinding elements, there is obtained a violet printing paste which i5 excellently suitable for printing on transfer papers (viscosity Ford 4:
21 seconds).

This violet printing paste can, by the mere stirring-in, by means of a turbine impeller, of 2 parts of an air-jet-ground dyestuff of the formula ~ C~c~ '. , and 2.3 parts of the air-jet-ground dyestuff of the formula b ~IH ~

be processed into a black printing paste, the viscosity of which still remains very good in the optimum range of a gravure-printing paste (viscosity difference only 1.5 seconds, i.e. Ford 4: 22.5 seconds).

If, on the other hand, the same pure-pigment amounts of the same two dyestuffs in the form of 50V/o ethylcellulose--~V~7~ 5 dyestuff preparations are stirred into the viole~ printing paste, then the viscosity of the resulting black printing in~
increases to above 50 seconds. A printing paste of such a high viscosity is however unusable in rotary gravure (intaglio) printing on paper.

Example 18 150 parts of a cationic dyestuff (ground by means of an air-jet mill) of the formula - Cl13 -~----C - C113 \UCH

are stirred, with a planetary mixer, with 130 parts of Printing Ink Solvent 2325 (Shell) containing 20 parts of cobalt-linoleate in the dissolved state, for 30 minutes at room temperature. There results a completely disaggregated dyestuff dispersion in paste form, which can be mixed together with 650 parts of a linseed oil varnish (350 P) containing 1S Pentalyn 833 (Hercules resin)~and 50 parts of polyethylene wax to form a lithographic printing paste.

A paper printed therewith by the offset process produces by transfer to an Orlon fabric, after 30 seconds contact time in a BASF press at 195 to 200C, an intensely yellow-coloured t~a~/e ~k :. , ,: .: ' , - : , - .
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~ 7~U5 printing.
If, instead of the cationic dyestuff, there are used identical amounts of the cationic optical brightener of the formula 3 C~3 ] C~l30503 Q

the procedure otherwise being the same, then a well optically brightened Orlon fabric is obtained.

Example 19 20 parts of a dyestuff preparation obtained according to Examples 1 to 8 are introduced, by means of a high-speed stirrer, into 980 parts of a 2.5% aqueous solution of sodium alginate, and the whole is stirred for 5 minutes.
There is obtained a printing paste which, by means of screen printing, ca-n be printed on paper (simply sized paper, 65 g/m ), which can then be used in the transfer printing process.

Example 20 20 parts of a dyestuff preparation obtained according to Examples 1 to 8 are introduced into 980 parts of oil-in-water emulsion. There results a printing paste which can ....

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be printed on paper by means of screen printing, which paper can then be employed in the transfer printing process.
The oil-in-water emulsion is prepared as follows:

15 parts of a carob bean flour ether and 5 parts of a suitable emuLsifier are dissolved in 480 parts of water.
By means of a high speed stirrer, 500 parts of a high-boiling benzine-mixture (boiling point 120 ~ 200C) are stirred into this solution to form an emulsion.

Example 21 20 parts of a dyestuff preparation according to Examples 1 to 8 are stirred, by means of a high-speed stirrer, into 980 parts of a water-in-oil emulsion. A printing paste is obtained, which can be printed by screen printing on paper, which can then be used in the transfer printing process.

The water-in-oil emulsion is prepared as follows:

15 parts of a suitable emulsifier is dissolved in 100 parts of a high-boiling benzine mixture. Into this solution there are then stirred, by means of a high-speed stirrer, 885 parts of a 2.5% aqueous solution of sodium alginate.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preparing a printing ink or paste which is suitable for transfer printing, which method comprises dispersing in water or an organic liquid suitable for use in a printing ink or paste a dyestuff or a dyestuff preparation containing at least 95% by weight of dyestuff and up to 5% by weight of a diluting or wetting agent, based on the weight of the preparation, the dyestuff having a particle size less than 15 y and the volatility of the dyestuff being such that at atmospheric pressure and at a temperature of from 160° to 220°C. at least 60% by weight of the dyestuff is vapourised in less than 60 seconds.

2. A method according to claim 1 wherein the dyestuff has a particle size of less than 5 µ.

3. A method according to claim 1 wherein a thickener is also dispersed in the water or organic liquid.

4. A method according to claim 1, 2 or 3 wherein there is used a dyestuff preparation containing from 0.1% but not more than 5% of diluting or wetting agent.

5. A method according to claim 1 which includes the step of wet or dry grinding the dyestuff or dyestuff preparation to a particle size less than 15 µ.

6. A method according to claim 5 wherein the grinding is performed dry.

7. A method according to claim 1, 2 or 3 wherein the dyestuff is a disperse dyestuff.

8. A printing ink or paste which is suitable for transfer printing which comprises a dyestuff or a dyestuff preparation containing at least 95% by weight of dyestuff and up to 5% of a diluting or wetting agent, based on the weight of the preparation, the dyestuff having a particle size less than 15 µ and the volatility of the dyestuff being such that at atmospheric pressure and at a temperature of from 160° to 220°C at least 60% by weight of the dyestuff is vapourised in less than 60 seconds.

9. A printing ink or paste according to claim 8 wherein the dyestuff has a particle size less than 5 µ.

10. A printing ink or paste according to claim 8 or 9 which further comprises a thickener.