EP0160767A1 - Process for printing natural silk substrates by transfer printing - Google Patents

Abstract

When silk is printed using the sublimation transfer printing technique, yellowing occurs. This is prevented by pretreating the silk with a liquid or solid impregnating agent, drying it and applying an optical brightener before, during or after the pretreatment, which is not intended for silk but for polyester fibers. Instead of or in addition to this measure, it is possible to use dyes which pass at lower temperatures than those which would lead to yellowing but migrate to sic and which prevent migration by pretreatment with migration-preventing, solid impregnating agents. You get strong, brilliant, real prints.

Description

The invention relates to a method for printing textile materials which consist entirely or partially of natural silk fibers, according to the principle of transfer printing from a transfer printing medium at elevated temperature. The principle of such pressure transmission methods is e.g. in FR-PS 1 233 330 and 1 585 119.

Since natural silk and textile materials containing natural silk are very much fashion items, transfer printing would offer great advantages in the color scheme of these textile structures, in particular flexibility in the storage of designs, the possibility of rationally producing high-quality designs, simplicity of the process, absence of water pollution, generation of halftones, etc. In addition, the silk fabrics are very often light goods down to 20 g / m ² , which can be dyed very easily in transfer printing machines, but only with great difficulty, if at all, using the classic fleet processes.

However, natural silk has practically no affinity for disperse dyes that are used in transfer printing, so that it is not possible to produce real prints. To overcome this difficulty, it has already been proposed to pretreat the textile substrate in order to generate such an affinity.

Basically, two paths have been considered. JP-A B-106 883 describes that natural silk fibers are chemically modified by grafting on styrene or other vinyl monomers. This process gives the silk fibers a certain affinity for disperse dyes, but is cumbersome and expensive and, of course, does not always have an advantageous effect on other properties of the natural fiber. It has therefore not been introduced.

As a second possibility to increase the affinity of the silk fiber for disperse dyes, it is proposed in JP-A 53-78386 and FR-A 2 296 537 to bring about a temporary affinity of the type discussed by making the natural silk textile material before the transfer printing treated with an aqueous impregnating agent and the fabric is then dried. The effect of this pretreatment appears to be that the water in the treatment liquor swells the silk fiber and that the swelling state thus created is retained after the water has been removed. When transferring The remaining impregnating agents then serve as a solvent phase for the disperse dyes, which - probably only to a small extent - can be embedded in fiber cavities. This mechanism is supported by the fact that acceptable fastness properties can only be achieved if the impregnating agent is washed out after printing; the stored dye should then be fixed due to the absence of the solvent impregnating agent.

However, this method, which is elegant per se, has not been able to prevail in practice either, since the silk at the temperatures customary for transfer printing of 200 to 210 ° strongly yellow during the transfer time in the presence of such impregnating agents - usually polyalcohols; if you want to avoid this by lowering the transfer temperature, for example to 190 to 200 ^o C, the brilliant shades required for silk printing are not achieved with the disperse dyes usual for transfer printing of polyester and the yellowing is only reduced and not completely eliminated.

The method described in JP-A 53-78386 belongs to this group of silk transfer printing. Variant that is supposed to provide good rub-fast prints and consists of treating a silk fabric with a polyhydric alcohol, the boiling point of which is above 140 ^o C, and printing the pretreated fabric with basic dyes in a thermally dry manner. The fastness to washing is not specified, but should be inadequate since the color cannot be more fast to washing than the polyol introduced. Since the transfer printing with basic dyes continues cumbersome and the number of color tones that can be achieved with such dyes is limited, the silk substances are poorly penetrated by these dyes and, moreover, yellowing of the substrate is also observed, this proposal cannot achieve the goal either.

Finally, dyes have become known, for example CI Solvent Blue 36, which are transferred from the transfer medium to silk at relatively low temperatures, for example 170 to 180 ° C., in 30 to 40 seconds and with good yield. However, these dyes are so flexible at room temperatures that they migrate and recrystallize so quickly and strongly in the swelling agents used in the silk that after a storage time of just a few hours - i.e. a storage time that is usually worth buying before washing must be taken and can hardly be shortened, significant level differences and discolouration occur in the original print image. Both of the two processes known at the beginning, which work with impregnating agents, are also to be washed very soon; according to FR-A 2296537 cold gespült'und 15 minutes, soaped at 50 ⁰ immediately after the transfer printing.

It is the aim and the object of the present invention to provide a method for the transfer printing of pure silk and mixed fiber textiles which does not have the disadvantages discussed, while the advantages inherent in the transfer printing are retained. The devices previously used to carry out the method should also be able to continue to be used.

The yellowing of natural silk during transfer printing could in principle be compensated by this, i.e. be made invisible by treating the silk with an optical brightener specially developed for this material (e.g. "Uvitex WG", Ciba-Geigy AG). However, such optical brighteners are not suitable for combined use and must be separated, i.e. in a separate dyeing process. Such a second pretreatment or aftertreatment would be too complicated and expensive for the transfer printing process under consideration and therefore not portable.

Surprisingly, it was found that yellowing of the silk can be reliably avoided in the above-mentioned second method of the prior art if, before, during or after the described pretreatment of the textile material, one is provided for the optical brightening of polyester materials, that is, not for natural silk Brightener applies, ie before the transfer printing itself. Normally, such brighteners are added to the aqueous pretreatment liquor which contains the impregnating agent.

Die angewendete Menge der optischen Aufheller in der wässrigen Vorbehandlungsflotte soll so gewählt werden, dass die nach der Applikation auf der Seide zurückbleibende Menge zur Vermeidung eines vergilbten Aussehens gerade ausreicht; höhere Mengen bringen keinen Vorteil. Die ausreichende Menge lässt sich durch ganz wenige Versuche sehr rasch bestimmen. Sie liegt in der Grössenordnung von 0,2 bis 5 Gew.-%, bezogen auf trockenes, vorzubehandelndes Seidengewebe. Wenn man die Vorbehandlungsflotte in solchen Mengen auf das Seidengewebe aufbringt, dass eine ca. 100 %ige Auflage resultiert, so enthält die Vorbehandlungsflotte bevorzugt 0,2 bis 5 Gew.-% an Aufheller.Optical brighteners for polyesters which can be used in the process according to the invention are generally those which are nonionic heterocyclic compounds, in particular oxazole and triazine derivatives. According to the current state of the art, the known stilbene derivatives, which have an optically brightening effect, are not suitable for polyester and are therefore not suitable for the purposes of the invention. The following are examples of industrial products which can be used according to the invention and belong to the above class:

The amount of optical brightener used in the aqueous pretreatment liquor should be chosen so that the amount remaining on the silk after application is just sufficient to avoid a yellowed appearance; higher quantities are of no advantage. The sufficient amount can be determined very quickly by very few experiments. It is of the order of magnitude of 0.2 to 5% by weight, based on dry, pretreated silk fabric. If the pretreatment liquor is applied to the silk fabric in such amounts that an approximately 100% coating results, the pretreatment liquor preferably contains 0.2 to 5% by weight of brightener.

The pretreatment itself can be carried out according to the procedures of the publications listed above; the most common is padding on the foulard. The pretreatment liquor contains so much impregnating agent that after application to the silk fabric and drying 15 to 30% by weight, preferably about 20% by weight, of impregnating agent remain in the fabric.

As an impregnating agent, which is applied as a pretreatment agent before the transfer printing in the aqueous phase, ie in solution, suspension or dispersion can be used, generally polyvalent, monomeric or polymeric polyalcohols, which are solid at temperatures below 60 ° C and melt in the temperature range from 60 to 160 ° C, are colorless, do not attack silk and in the liquid, but not in the solid state on the act dispersing dyes used, this latter condition of course only needs to apply to the combination of the selected dye and impregnating agent used.

• Polyäthylenglycol mit einem durchschnittlichen Molekulargewicht von 200 bis 1000, insbesondere 300 bis 600; Polypropylenglycol mit einem durchschnittlichen Molekulargewicht von 400 bis 1100, insbesondere 400 bis 900; Polyäthylen-polypropylen-glycol; 1,1,1-Tris-(hydroxymethyl)-propan; 1,1,1-Tris-(hydroxymethyl)-äthan; f -Caprolactam; Nicotinsäureamid; Isonicotinsäureamid; Isopropylenharnstoff; Aethylenharnstoff und Glyoxylmonourein.

The following have particularly proven themselves as impregnants in the process according to the invention:

• Polyethylene glycol with an average molecular weight of 200 to 1000, in particular 300 to 600; Polypropylene glycol with an average molecular weight of 400 to 1100, in particular 400 to 900; Polyethylene polypropylene glycol; 1,1,1-tris (hydroxymethyl) propane; 1,1,1-tris (hydroxymethyl) ethane; f -caprolactam; Nicotinamide; Isonicotinamide; Isopropylene urea; Ethylene urea and glyoxylmonourein.

Suitable dyes are the dyes normally used for transfer printing on polyester substrates, generally dispersion dyes, such as, for example, CI Disperse Red 60, CI Disperse Yellow 54, CI Disperse Blue 331, CI Disperse Blue 72, CI Disperse Blue 19, CI Disperse Violet 1. The more water-insoluble the dyes, the better the wash fastness that can usually be achieved.

enthalten zum Bedrucken von Seide ist neu und soll - besonders hervorgehoben werden.The use of the trichromes which are 1,4-diisopropylaminoanthraquinone as the blue dye, l-amino-2-chloro-4-hydroxyanthraquinone as the red dye (l-amino-2-bromo-4-hydroxyanthraquinone can also be used) and the yellow dye Product with the formula

included for printing on silk is new and should be emphasized.

However, these are migrating dyes, and in order to avoid migration, the specified trichromes should only be used in conjunction with silk substrates which have been pretreated with one of the impregnating agents described above and are solid to at least 60 ° C.

In practice, the transfer printing can be carried out as usual; reference is made to the above-mentioned publications relating to the prior art. However, it was found that especially adapted process conditions should also be set for special substrates and effects. The brilliant shades of color required for natural silk and sufficient general fastness properties of the print are achieved with transfer printing conditions of 30 seconds / 205 ° C reached. The penetration of the printed image, which is required for many silk products such as scarves, etc. - the front and back should not be visibly different from one another, is excellent for lighter silk fabrics with a weight per unit area of at most 50 g / m ² . Higher-weight substances obtained by this print image when the contact pressure of the Umdruckträgers is increased to the textile material, for example to 10 to 10 _P a, for example, and preferably 5 x 10 Pa and above.

Another possibility, heavier silk qualities, i.e. Over 50 g / m2, to print with perfect penetration, consists in the use of dyes, which at temperatures of 190 ° C and below pass from the transfer medium to the pretreated silk in practically 100% yield in 30 seconds. Attempts have been made to solve the known problem of deterioration of the printed image. It has been possible to find impregnating agents which are mixed with these rapidly subliming dyes, e.g. C.I. Solvent Blue 36, do not form migrating systems; this appears to be due to the intolerance of the dye and the impregnating agent, which is required at temperatures below about 60 ° C., as already stated above. Such impregnating agents are those in the list above with the exception of the liquid polyglycols. The transfer prints produced are resistant to changes in the printed image for up to 8 weeks when stored below 40 ° C .; then, however, you should no longer wait to rinse or wash. It is sufficient to rinse the goods with warm water at 40 ° C for some time.

The dyes used are usually slightly water-soluble. This must be taken into account when washing the printed substrate. If liquid, easily and quickly soluble glycols have been used in the pretreatment of the silk fabric, a cold rinse is sufficient. When using (or using) waxy glycols that take a little longer to dissolve, it is best to use warm water. If surfactants are added for faster wetting, careful attention should be paid to the solubility of the dyes. If desired, surfactants can be added to the washing liquor. Then it is dried.

With this process variant, it is not necessary to use an optical brightener for polyester. The invention is therefore based on a twofold basis: either one applies transfer conditions in which material yellowing would occur, but prevents them by adding optical brighteners; or one applies conditions in which a rapid dye migration would then have to occur, but this is prevented by using migration-preventing impregnating agents. Both basic measures can be combined.

A second way of obtaining high-color, high-penetration prints is to use transfer paper with an extremely high range of dyes. This measure is not obvious, because there was a fear that poor rub fastness would occur with large depths of color (see, for example, BASF publication CTE-072 d, page 10). Surprisingly, this was not observed. Instead, it was found that with the known Dyes for transfer printing on polyester, for example CI Disperse Red 60, CI Disperse Yellow 54 and CI Disperse Blue 331 for transfer printing on silk, the guideline depth 2/1 could be achieved while maintaining the textile fastness, if transfer papers with a dye range of 1 to 2, 5 g / m ² , preferably about 1.5 g / m can be used. If one produces these subcarriers in gravure printing with the usual engraving, this value is obtained with a printing ink which has a dye content of 15% by weight. When transfer printing polyester, a dye supply of 0.75 g / m ² is generally not exceeded.

The specified amounts of dye refer to the square meter of printed area, ie areas that do not contain any dye are not included in the calculation. It is particularly surprising that the increase in color strength is observed even with extremely light silk qualities with a basis weight of less than 50 g / m ² , in which the color strength is already visible with a conventional dye range of 0.75 g / m ^2. and the back of the fabric is practically identical.

The person skilled in the art could not have foreseen that a range of dyes, which is about twice the usual, leads to these surprising results, because even with the normal amount of dye on the transfer paper, after the transfer printing, a dye residue remains / remains on the auxiliary carrier. Reference is also made to Example 4 below.

The exact selection of the parameters of the process, especially the color on the transfer medium range of fabrics depends on the weight and construction of the silk substrate and the desired effects. In general, the results are perfectly when the _F ARB material offered 50 to 100% larger than in conventional transfer printing on polyester.

Particularly brilliant shades and generally high fastness properties are achieved with the C.I. Solvent Yellow 160, C.I. Disperse Red 55, C.I. Disperse Blue 56 and C.I. Disperse Blue 60 achieved.

However, one should assume that these dyes cannot be used for transfer printing on silk, since they sublimate relatively slowly and have to be printed on polyester at 210 ° C / 60 seconds (see, for example, for CI Disperse Blue 60: "Transfer Printing of Polyester ", Technical Instructions _B R 1107, Yorkshire Chemicals Limited, Leeds, UK).

Under these transfer printing conditions, an unacceptable yellowing of the silk occurs even without pretreatment with swelling stabilizers, and the penetration of the textile with dye is very poor.

Surprisingly, however, it has been found that by mixing these dyes with the dyes CI Disperse Yellow 54, CI Disperse Red 60 and CI Disperse Blue 33, which are used commercially for transfer printing on polyester on a large scale, a dye system was obtained which, under transfer printing conditions, was 200-205 ° C / 40 sec prints with excellent penetration, good brilliance and excellent fastness properties.

The observation that the dye C.I. Solvent Yellow 160, which produces prints of high brilliance but very poor light fastness (grade 2) on natural silk, produces prints with good brilliance and good light fastness (grade 4.5), if in the printing ink about 30-70% of this dye, in particular about 50% with 70-30%, especially about 50% of the dye CI Disperse Yellow 54 can be mixed.

The transfer printing medium, which generally consists of paper, is obtained in the usual known manner. With regard to this process feature, reference should also be made to the literature already cited.

The method according to the invention has the additional advantage that the extensive sample and design collections that are usually already available in transfer printers can be used without additional work and changes.

example 1

A desized and bleached silk fabric of the quality "chiffon" with a basis weight of 25 g / m ² is mixed with an aqueous liquor containing 200 g / 1 polyethylene glycol 300 and 20 g / 1 of the optical brightener "Uvitex ET" (Ciba-Geigy) , padded to 100% weight gain and dried in a stenter at 120 ° C for 1 minute.

A transfer paper with a basis weight of 40 g / m ^{2 is} placed thereon, which was rotogravure printed with ink containing the dyes CI Disperse Red 60, CI Disperse Yellow 54 and CI Disperse Blue 331.

It is reprinted at 205 ° C for 30 seconds. The result is a brilliant print with good fastness properties and a resolving power that cannot be achieved with conventional printing processes for goods with this low basis weight. The penetration of the tissue with dye is so good that the front and back have practically the same intensity.

Within two months of transfer printing, the polyethylene glycol is rinsed out of the fabric with water and dried on a tenter frame.

Example 2

A desized and bleached silk fabric with a basis weight of 70 g / m ² is padded to 100% weight gain with an aqueous liquor which contains 20% by weight ε-caprolactam and dried at 100 ° C. for two minutes. A transfer paper with a basis weight of 60 g / m ^{2 is} placed thereon, which has been gravure printed with inks which contain 1,4-diisopropylaminoanthraquinone as blue dye and l-amino-2-chloro-4-hydroxyanthraquinone as red dye (it can also be l -Amino-2-bromo-4-hydroxyanthraquinone can be used), and contain the product with the formula as a yellow dye.

The transfer printing takes place in 30 seconds at 170 ° C.

The result is a brilliant print with good fastness properties and very good penetration of the dyes into the silk fabric. A yellowing of a possible Weissfonds does not appear.

Within two months of transfer printing, the swelling agent is rinsed out of the fabric with water at 40 ° C and dried on a tenter.

Example 3

A desized and bleached silk fabric with a basis weight of 120 g / m ² is padded to 100% weight gain with an aqueous liquor which contains 20% by weight ε-caprolactam and dried in a tenter at 120 ° C. for two minutes.

A transfer paper with a basis weight of 40 g / m ^{2 is} placed on top, which was printed with gravure printing ink, which is characterized by the fact that firstly the total concentration of dye is about twice as large as usual in conventional transfer printing for polyester and secondly the basic dyes consist of mixtures of the dyes of Example 1 with those of Example 2. For a highly brilliant red tone, for example, an ink is used which contains 9% by weight of the dye CI Disperse Red 60 and 10% by weight of the dye 1-amino-2-chloro-4-hydroxyanthraquinone.

The transfer printing takes place in 40 seconds at 200 ° C. The result is a brilliant print with good fastness properties and excellent penetration of the dyes into the silk fabric.

Within two months of transfer printing, the swelling agent is rinsed out of the fabric with water at 40 ° C and dried on a tenter.

Example 4

A silk fabric pretreated according to Example 1 with a weight per unit area of 25 g / m ² is printed on 40 _S e-customers at 205 ° C. with a transfer paper in which 0.75 g of CI Disperse Red 60 dye are distributed uniformly per square meter.

The dye remaining on the paper after transfer printing was dissolved in dimethylformamide and determined spectrometrically. 24% of the original amount of dye was left on the paper.

In a second experiment, a transfer paper containing 1.5 g of the same dye per m ^{2 was transferred} under the same conditions as in the experiment above. After the transfer printing, it was determined colorimetrically that the color depth on the silk fabric was 1.8 times greater than in the first attempt, that a standard type depth of 2/1 had now been achieved on both the front and the back of the fabric, and that 25.4% of the dye remained on the base paper (subcarrier).

Example 5

A desized and bleached silk fabric with a basis weight of 70 g / m ² is padded to 100% weight gain with an aqueous liquor containing 20% polyethylene glycol 300 (and 2% Uvitel EBF (Ciba-Geigy)) and two minutes at 100 ° C dried. A transfer paper with a basis weight of 40 g / m ^{2 is} placed thereon, which has been rotogravure printed with inks which are 10% CI Disperse Red 60 and 10% CI Disperse Red 55 as red dye and 10% CI Disperse Yellow 54 and 10 as yellow dye % CI Solvent Yellow 160 and 10% CI Disperse Blue 331 and 10% CI Disperse Blue 60 as blue dye.

The transfer takes place at 205 ° C in 40 m.

The result is a very brilliant print with very good fastness properties and good penetration of the dyes into the silk fabric.

Claims (12)

1.- Process for printing of textile materials which consist wholly or partially of natural silk fibers, one of an _I mprägniermittels pretreated and the pretreated textile material dries on the principle of transfer printing from a transfer sheet at elevated temperature, in which the textile materials with an aqueous preparation, characterized in that that dyes are used which, at temperatures of 190 ° C. and below, pass from the transfer medium to the pretreated textile material in essentially 100% yield in 30 seconds and, in order to achieve a stable and real pressure, the pretreatment with the aqueous solution, suspension or Dispersion of an impregnating agent which is solid below 60 ⁰ C and melts in the temperature range from 60 to 160 ° C, is essentially colorless, does not attack silk and, in the liquid but not in the solid state, has a solvent effect on the dyes used in such a way that at temperatures of the highest s 210 ° C, and that the printed textile material is rinsed or washed. 2. - Process according to claim 1, characterized in that compounds of the formula are used as the impregnating agent

or

used, in which mean: n zero or 1, m is a natural number, R is hydrogen, C ₁ to C ₈ alkyl, C ₇ to C ₁₅ aralkyl or alkaryl,

R ² SO ₂ - or

R ¹ - _OH , -OR ² , -SR ² , -NHR ² ,

R ² C ₁ to C ₈ alkyl, C ₅ to C ₁₀ cycloalkyl, C ₇ to C ₁₅ aralkyl or alkaryl, C ₆ or C ₁₀ aryl or furfuryl, A

-CH ₂ C (CH ₂ OR) ₃ ,

(-CH ₂ ) ₃ CCH ₂ OR, (- ^CH ₂ ) ₄ ^C,

and z = ^{0, 1, 2,} 3 or ⁴ , where z is not greater than y, and x the number of unsaturated valences of A. 3. - The method according to claim 1, characterized in that as the impregnating agent, which corresponds to the stated properties, a polyethylene glycol, a polypropylene glycol, a polyethylene-polypropylene glycol, 1,1,1-tris (hydroxymethyl) propane, 1 , 1,1-tris (hydroxymethyl) ethane, ε-caprolactam, nicotinamide, isonicotinamide, isopropyl urea, ethylene urea or glyoxal monourein are used. 4. - Modification of the method according to claim 1, characterized in that suitable dyes are used for polyester dyeing, a liquid or solid impregnating agent is used, and that one is provided before, during or after the pretreatment with the aqueous impregnating agent for the optical brightening of polyester materials applies optical brighteners. 5. - Process according to claim 4, characterized in that a polyhydric alcohol, in particular a polyethylene glycol with an average molecular weight of 200 to 1000, preferably from 300 to 600, or a polypropylene glycol with an average molecular weight of 400 to 1100, is preferred as the impregnating agent 400 to 900 used and transferred at temperatures of 190 to 230 ° C. 6. - The method according to claim 4, characterized in that the liquor containing the optical brightener is applied in such amounts that there is an amount of brightener in the silk of 0.2 to 5 wt .-%. 7. - The method according to claim 4, characterized in that one works at increased contact pressure of the transfer carrier on the textile material, in particular at a contact pressure of 10 ³ to 10 ⁶ Pa, preferably more than 5.10 ³ Pa. 8. - Method according to one of the preceding claims, characterized in that the aqueous pretreatment preparation is applied in such amounts that the pretreated, dried silk fabric contains 15 to 30 wt .-%, preferably about 20 wt .-% of impregnating agent. 9. - Method according to one of the preceding claims, for producing brilliant prints, characterized in that transfer printing media are used which have 1 to 2.5 g of dye per m ^{2 of} printed area, preferably about 1.5 g / m ² . 10. - Transfer printing medium for carrying out the method according to claim 9, which contains 1 to 2.5 g of sublimable dye per m ^{2 of} printed area on a flat substrate. 11. - Use of trichromes 1,4-diisopropylamino-anthraquinone (blue) 2) 1-Amino-2-chloro-or-bromo-4-hydroxy-anthraquinone (red) and

(yellow) for printing silk fabrics in transfer printing, which are pretreated with a solid impregnating agent according to claim 1. 12. - Use of mixtures of a) CI Solvent Yellow 160 and CI Disperse Yellow 54, b) CI Disperse Red 66 and CI Disperse Red 60, c) CI Disperse Blue 56 or CI Disperse Blue 60 and CI Disperse Blue 331 for printing silk fabrics in transfer printing according to the procedures described here with particularly high brilliance and high fastness properties.