EP0017618B1 - Process for optically brightening polyester fibres by the exhaust process - Google Patents

Description

The present invention relates to a new, improved process for the optical brightening of polyester fibers in the exhaust process with the aid of conventional polyester brighteners with the use of shading dyes.

In bleaching and optical brightening, it is an often practiced method to use violet or blue dyes to improve the bleaching or lightening effect. If such a dye is applied together with an optical brightener, this can serve two different purposes: on the one hand, an increase in the degree of whiteness can be sought by compensating for the yellow portion of the fiber, the color tone produced by the brightener on the fiber being largely retained. On the other hand, a change in the shade of the color tone produced by the brightener on the fiber can be aimed for with said dye, and here too an attempt is made to additionally increase the degree of whiteness. You can use it to set the desired shade of white.

Particularly interesting white effects can be achieved in this way on fiber materials with a high basic white, in which the achievement of a small increase in brightness (degree of whiteness) means a considerable additional effort in the bleaching or lightening process. Small amounts of dye, generally about 0.0025-2.5%, preferably 0.025-1.25%, based on the amount of brightener used, are added for shading. In terms of process engineering, the nuance of continuously producible optical brightenings (for example in the padding thermal process) generally presents no difficulties. The shading, e.g. B. with disperse dyes, of optical brightening after the exhaust process, however, is often associated with significant equal problems. Up to now, the shading of optical brightenings with the aid of the pull-out process on polyester fibers has proven to be almost impossible if disperse dyes adapted to the authenticity standard of the brightener were used as shading dyes. The usual lightening, but also the dyeing of polyester fibers after the exhaust process is usually carried out from weakly acidic to neutral baths. In this way, if a shading dye is used in addition to the brightener, very uneven lightenings are obtained, since the dye quickly deposits on the fiber and so the fabric stains too strongly at certain points. Attempts have already been made to counter this disadvantage by adding leveling agents. On the one hand, this did not, however, completely solve the problem, and on the other hand, the process became more uneconomical due to the need to use expensive leveling agents.

A new, improved method has now been found which completely eliminates the disadvantages of the known methods just described.

The process according to the invention for the optical brightening of polyester fibers in the drawing-out process by treating the fibers in an aqueous polyester brightener which is stable under the application conditions and which absorbs onto the substrate and a small amount of a blue to violet disperse dye or mixtures of such dyes as shading dye is thereby characterized in that the treatment in said dispersion is carried out at a pH of more than 9.

In principle, there is no need to limit the pH upwards. Even amounts of alkali that lead to a pH of over 14 in the dispersion do not affect the levelness of the brightening. An upper limit is at best given for economic reasons. An upper limit of the alkalinity would be given, for example, by the process conditions of the »peeling process« of the polyester material (for example at a concentration of 10-20 g / l NaOH).

Preferably the dispersion has a pH between 11 and 14, e.g. B. between 11 and 13.5, in particular between 11 and 12.5.

The pH is adjusted using a suitable alkaline substance, preferably using alkali metal hydroxides, in particular using KOH, but especially NaOH.

The treatment is carried out in the customary manner at a temperature between room temperature and 140 ° C., in particular between 50 ° and 130 ° C. The fiber material is advantageously used at a lower temperature (for example 50 ° C.), whereupon the temperature is increased (e.g. to 120 ° C).

In order to ensure that the brightener is optimally drawn onto the fiber, work is preferably carried out in practice under high temperature (HT) conditions, that is to say the fibers are treated in a conventional HT dyeing machine above 100 ° C., for example between 100 and 130 ° C, e.g. B. at 120 ° C.

Another way to make it easier to attach the brightener to the fiber is to add a carrier to the treatment bath that is common in dyeing practice. With carrier addition, it is also possible to achieve very good results at lower temperatures, for example below 100 ° C. However, carrier addition can also be used under HT conditions. Suitable carriers are those customary in dyeing practice, e.g. B. aromatic hydrocarbons, aromatic halogenated hydrocarbons and esters and ethers of aromatic carboxylic acids. Preferred carriers are dichlorobenzenes and trichlorobenzenes, optionally also diphenyl and mixtures of the substances mentioned.

The duration of the treatment of the textiles in the brightener dispersion can vary within wide limits, but an application period of at least 20 to 30 ° minutes is advantageous.

The amount of brightener (pure substance) in the dispersion can, depending on the brightener used, vary between 0.002 and 0.5%, based on the material to be lightened.

The amount of shading dye (pure dye) is, depending on the dye and the desired shade, about 0.0025-2.5%, preferably 0.025-1.25%, based on the amount of brightener (pure substance) used.

The usual polyester brighteners are used as brighteners, which in practice are applied together with shading dyes. These are mostly benzoxazole, stilbene and naphthalimide brighteners.

bzw.

wobei die Ringe A, B und C noch einfache Reste, wie niedere Alkyl- oder Alkoxygruppen oder Chloratome enthalten können, vor allem das 2,5-bis-Benzoxazol-2-yl-thiophen, das 2,5-bis-(5-Methyl- benzoxazol-2-yl)-äthylen und das 1,4-bis-Benzoxazol-2-yl-naphthalin; oder der Formel

worin n 0 oder 1 bedeutet und die Ringe A und B weitersubstituiert sein können, z. B. mit Alkyl, Alkoxy, Phenyl, Chlor, Cyano, Carboxy und dessen Derivaten, z. B. die Verbindungen: 4-Phenyl-4'-(5-t-butyl- benzoxazol-2-yl)stilben, 4-Phenyl-4'-(5,8-dimethylbenzoxazol-2-yl)stilben, 5,6-Dimethyl-2-(4-methoxycarbonyl-styryl)benzoxazol und 5,6-Dimethyl-2-(4-cyanostyryl)benzoxazol.Of the benzoxazole brighteners, e.g. B. bis-benzoxazole, styryl or stilbenyl benzoxyzole types to mention, especially compounds of the formulas

respectively.

rings A, B and C may also contain simple radicals, such as lower alkyl or alkoxy groups or chlorine atoms, especially 2,5-bis-benzoxazol-2-yl-thiophene, 2,5-bis- (5- Methyl-benzoxazol-2-yl) ethylene and 1,4-bis-benzoxazol-2-yl-naphthalene; or the formula

where n is 0 or 1 and rings A and B may be further substituted, e.g. B. with alkyl, alkoxy, phenyl, chlorine, cyano, carboxy and its derivatives, for. B. the compounds: 4-phenyl-4 '- (5-t-butylbenzoxazol-2-yl) stilbene, 4-phenyl-4' - (5,8-dimethylbenzoxazol-2-yl) stilbene, 5,6 -Dimethyl-2- (4-methoxycarbonyl-styryl) benzoxazole and 5,6-dimethyl-2- (4-cyanostyryl) benzoxazole.

bzw.

worin die Ringe A, B und C verschiedene Substituenten tragen können, wie z. B. Alkyl, Alkoxy, Chlor, Cyano, Carboxy und dessen Derivate usw., zu erwähnen, insbesondere die Verbindungen 2-Cyano-4-(naphtho(1,2-d]v-triazol-2-yl)-4'-chlorstilben, 4-(Naphtho[1,2-dlv-triazol-2-yl)-4'-methoxy- carbonylstilben, sowie 1,4-bis-(2-Cyanostyryl)benzol.Of the stilbene brighteners are those of the formulas

respectively.

wherein the rings A, B and C can carry different substituents, such as. As alkyl, alkoxy, chlorine, cyano, carboxy and its derivatives, etc., to mention, in particular the compounds 2-cyano-4- (naphtho (1,2-d) v-triazol-2-yl) -4'- chlorstilbene, 4- (naphtho [1,2-dlv-triazol-2-yl) -4'-methoxycarbonylstilbene, and 1,4-bis- (2-cyanostyryl) benzene.

worin R_i und R₂ Wasserstoff oder Alkoxy bedeuten, zu erwähnen, insbesondere solche, worin R₁ Wasserstoff und R₂ Methoxy bedeuten oder worin Ri und R₂ jeweils für Äthoxy stehen.Of the naphthalimide brighteners are those of the formula

in which R _i and R _{2 are} hydrogen or alkoxy, especially those in which R _{1 is} hydrogen and R _{2 is} methoxy or in which R ₁ and R _{2 are} each ethoxy.

worin die Benzolringe A gegebenenfalls substituiert sein können, z. B. durch Alkyl, Alkoxy, Halogen _usw. Besonders gut eignen sich dabei solche Farbstoffe, deren Benzolringe A unsubstituiert sind oder in para-Stellung mit Chlor oder Methoxy substituiert sind.Blue to violet disperse dyes are used as shading dyes, which of course have to be suitable for treatment in an alkaline liquor. Acylaminoanthraquinone dyes are preferably used, in particular those of the formula

wherein the benzene rings A may be optionally substituted, e.g. B. by alkyl, alkoxy, halogen, _etc. Dyes whose benzene rings A are unsubstituted or substituted in the para position with chlorine or methoxy are particularly suitable.

In addition to the optical brightener (s) and the shading dye (s), the aqueous dispersion advantageously also contains one or more dispersants and, if appropriate, wetting agents, stabilizers and / or other customary dyeing auxiliaries.

Suitable dispersants include: alkali metal salts, especially sodium salts of alkyl or alkylarylsulfonic acids and carboxylic acids, alkali metal salts, especially sodium salts of condensation products of arylsulfonic acids with formaldehyde, macromolecular substances which are suitable for liquefaction and dispersion, carboxylates of the polymerized maleic acid type polymerized acrylic acid and copolymers of maleic acid with allyl acetate. Examples of such dispersants are: lauryl sulfate sodium salt, oleyl sulfate sodium salt, oleyl sulfate diethanolamine salt, benzylnaphthalenesulfonic acid Na, di- (2-sulfo-1-naphthyl) methane di-Na salt, m-xylenesulfonic acid Na, dodecylbenzenesulfonic acid Na Na salt, dodecylbenzenesulfonic acid, diethanolamine, diisopropylnaphthalenesulfonic acid Na, di-n-butylnaphthalenesulfonic acid Na, n-propyl-n-hexylnaphthalenesulfonic acid Na, N-oleylmethyl taurine Na salt, Na salt of the condensation product of naphthalenesulfonic acid and formaldehyde acid formaldehyde , Benzenesulfonic acid sodium salt, cumene sulfonic acid sodium salt, toluenesulfonic acid sodium salt, oxyethylated resin bodies, N-polyvinylpyrrolidone, sulfite cellulose waste liquor (CaO-free), starch ether and polysaccharides. However, particularly preferred dispersants are nonionic, water-soluble ethoxylated or propoxylated fatty alcohols and alkylphenols and fatty alcohol polyglycol ethers, for example alkanols, alkenols (C ₈ -C ₂₂ ) with different amounts of ethyleneoxy or propyleneoxy groups, alkyl or arylpolyglycol ethers with up to 50 ethyleneoxy or propyleneoxy groups, such as octyl, nonyl or dodecylphenol polyglycol ether.

The individual components can be introduced separately into the treatment bath, which is already alkaline or is only then adjusted to the desired pH.

However, there is preferably a concentrated, storage-stable stock dispersion of the optical brightener (s) and the shading dye (s). Such dispersions contain brightener and dye in the desired ratio. They are made by adding brightener and dye, preferably made together with a dispersant in a small amount of water. It is advantageous if this dispersion is subjected to grinding (for example in a ball mill) in order to obtain particle sizes of less than 10 μm, preferably less than 2 μm.

A part of this stock dispersion can then be introduced (calculated on the desired amount of brightener in the bath) into the treatment bath, which may also contain a dispersant and / or other auxiliaries. After the desired pH has been set, polyester fibers in the form of yarn, woven fabric, etc. can be treated with the dispersion thus obtained in the corresponding dyeing apparatus.

If a chlorite-resistant shading dye was used, the bleaching bath can then be bleached directly. Sodium chloride is preferably added to the liquor, the alkaline bath is acidified and then heated to about boiling temperature.

In the present application, "polyester fibers" naturally also include polyester fibers in blended fabrics, eg. B. in mixed fabrics polyester / cotton. The nuanced lightening of such blended fabrics by the process according to the invention can also be advantageous with the lightening of the cotton content, with the bleaching (e.g. with peroxide) and / or the various conventional finishing and finishing processes (e.g. crease-resistant, wash and wear, soft grip and other equipment) can be combined.

The following examples serve to explain the process according to the invention in more detail, but without restricting it to them.

example 1 a) Preparation of a brightener stock dispersion

werden mit 20 mg des violetten Pigmentfarbstoffes der Formel

versetzt, zusammen mit 20 g eines Anlagerungsproduktes von 35 Äthylenoxidgruppen an 4-Nonylphenol in 40 ml Wasser gegeben, gemischt und mit 50 g Quarzkugeln von 1 mm Durchmesser in einer Kugelmühle während ca. 24 Stunden gemahlen. In der resultierenden Dispersion haben die Teilchen einen Durchmesser von ≦ 211m. Die Dispersion wird von den Quarzkugeln durch Filtration durch ein engmaschiges Sieb abgetrennt und mit einer Lösung von 1 g Carboxymethylcellulose in 19 ml Wasser versetzt. Man erhält eine lagerstabile Dispersion.20 g of the optical brightener of the formula

with 20 mg of the purple pigment of formula

added, added together with 20 g of an adduct of 35 ethylene oxide groups to 4-nonylphenol in 40 ml of water, mixed and ground with 50 g of quartz balls of 1 mm in diameter in a ball mill for about 24 hours. In the resulting dispersion, the particles have a diameter of ≦ 211m. The dispersion is separated from the quartz spheres by filtration through a close-meshed sieve and a solution of 1 g of carboxymethyl cellulose in 19 ml of water is added. A storage-stable dispersion is obtained.

b) brightening

0.4 g of the stock dispersion described under a) and 0.2 g of a dispersant (adduct of 35 ethylene oxide groups with stearyl alcohol) are processed into a dispersion with 400 ml of water and the latter is made alkaline with 0.8 ml of NaOH 30%.

40 g of polyester staple fabric (washed and heat-set at 1800 C for 20 seconds) are wound evenly onto bobbin tubes as a fabric tape of approx. 250 x 12 cm and treated with the dispersion just described in an HT dyeing machine. The fleet had an initial pH of 11.5. At the beginning of the treatment the temperature is 50 ° C, after that heated to 130 ° C within 30 minutes and then left at this temperature for 30 minutes. The mixture is then cooled to 70 ° C., the liquor is drained off, the fabric is rinsed twice warm and dried in a drying cabinet at 80 ° C. for 5 minutes.

The lightened fabric has a high degree of whiteness with perfect levelness.

comparison

For comparison purposes, the experiment is repeated, but not 0.8 ml of NaOH 30%, but 0.2 ml of acetic acid 80% are added to the dispersion (pH of the liquor: 5.5). In this way, the brightening is carried out according to the conventional method. After drying, a fabric is obtained which is very uneven and therefore unusable. The shading dye is largely deposited in the inner part of the ribbon.

Example 2

und 20 mg des Pigmentfarbstoffes der Formel

eine stabile Dispersion bereitet.Analogously to Example 1 a), 20 g of the brightener of the formula

and 20 mg of the pigment dye of the formula

prepares a stable dispersion.

As described in Example 1b), 0.4 g of this stock dispersion is processed into a liquor (pH approx. 11.5) and thus 40 g of polyester staple fabric is lightened in the manner given there. The treated fabric also has a high degree of whiteness with perfect levelness.

Example 3

und

so kommt man ebenfalls zu einem stark aufgehellten Polyestergewebe von einwandfreier Egalität.The procedure is completely analogous to Example 2, but using a mixture of the two compounds of the formulas as brightener

and

so you also get a highly lightened polyester fabric of perfect levelness.

Example4

ein, so erhält man ebenfalls ein stark aufgehelltes Polyestergewebe von ausgezeichneter Egalität.If example 2 is repeated, however, the polyester brightener used is that of the formula

a, you also get a highly lightened polyester fabric of excellent levelness.

Example 5

0.4 g of the stock dispersion described in Example 1 a) and 0.2 g of a dispersant (adduct of 35 ethylene oxide groups with stearyl alcohol) are processed into a dispersion with 400 ml of water and the latter made alkaline with 0.8 ml of NaOH 30%.

40 g of polyester staple fabric (washed and heat-set at 180 ° C for 30 seconds) are evenly wound onto bobbin tubes as a fabric tape of approx. 250x12 cm and treated with the dispersion just described in an HT dyeing machine. The fleet had an initial pH of 11.5. The fabric is introduced at 50 ° C. and the liquor is heated to 120 ° C. in 30 minutes, treated at this temperature for 15 minutes, cooled to 70 ° C., 0.8 g of sodium chloride 80% is added and the liquor is made up with 1 , 4 ml of formic acid 85% to a pH of 3-4. The mixture is heated to about 100 ° C. in 20 minutes, treated at this temperature for 30 minutes, then the liquor is drained off, rinsed and dried. The piece of fabric is immaculate and has a high degree of whiteness.

Example 6

und verfährt ansonsten genau nach den dort angegebenen Vorschriften, so erhält man ebenfalls jeweils Polyestergewebe von hohem Weißgrad und einwandfreier Egalität.In Examples 1 to 5, the respective dye is replaced by the same amount of the dye of the formula

and otherwise proceeds exactly according to the regulations given there, you also get polyester fabrics of high whiteness and perfect levelness.

Claims (10)

1. A process for whitening polyester fibres by the exhaust method by treating said fibres in an aqueous dispersion containing one or more fluorescent whitening agents for polyester which have affinity for the substrate and are stable under the application conditions, and a small amount of a blue or violet disperse dye, or a mixture thereof, as shading dye, which process comprises carrying out the treatment in said dispersion at a pH value above 9.

2. A process according to claim 1, which comprises the use of a dispersion which has a pH value between 11 and 14, especially between 11 and 12,5.

3. A process according to claim 1, wherein the shading dye is used in an amount of 0,025 to 1,25%, based on the fluorescent whitening agent employed.

4. A process according to claim 1, wherein the fluorescent whitening agent employed is a conventional benzoxazole, e. g. a bis-benzoxazole, styryl- or stilbenylbenzoxazole, a triazolyl- or styrylstilbene or a naphthalimide fluorescent whitening agent for polyester, or a mixture thereof.

5. A process according to claim 1, wherein the shading dye is a blue or violet dye of the class of the acylaminoanthraquinones.

6. A process according to any one of claims 1 to 5, which comprises the use of a dispersion which, in addition to containing the fluorescent whitening agent and the shading dye, also contains one or more conventional dispersing agents and optionally wetting agents, stabilisers and further customary dyeing assistants.

7. A process according to any one of claims 1 to 5, which comprises adding an amount of a concentrated dispersion which contains the fluorescent whitening agent, the shading dye and a dispersant, and which has a particle size smaller than 2 um, to a bath which contains a dispersant and has been adjusted with NaOH to the desired pH value, and treating polyester material with said bath in the conventional manner.

8. A process according to claim 1, wherein the material is subsequently also bleached in the same bath, preferably with sodium chlorite.

9. A process according to claim 1, wherein the treatment of the polyester fibres with the alkaline fluorescent whitening agent dispersion is carried out under high temperature conditions.

10. A process according to claim 1, which comprises the use of an alkaline fluorescent whitening agent dispersion which contains a carrier customarily employed in dyeing.