The object of the invention is the pretreatment method of poliester for reducing elimination of oligomers at high-temperature acid colouring with dispersion dyes and the composition of the pretreatment bath for poliester, which is to be coloured according to the conventional acid procedure in the high-temperature devices. The technical problem at conventional high- temperature acid colouring of poliester are the low molecular ethileneglycoltereftalat fractions or oligomers, which at high-temperature colouring diffuse from the inside to the surface of poliester fibres and precipitate on the coloured material or partly disperse in the colouring bath. This is a balanced process, as at the colouring temperature these low molecular fractions because of the differences in solubility in polimer melting and in colouring bath are eliminated from the fibres.

In the complex of oligomers the linear and the cyclic fractions are eliminated, whereby the least preferred fraction is the cyclic trimer. The latter precipitates as the cristal powder with the melting point 316-325 °C on the vital parts of the colouring devices, as well. It belongs to those

oligomers, which are water-insoluble. The oligomers remain on the textile as white deposited particles, as they can not be coloured by the dispersion dyes.

Depending on the way of poliester manufacture, different amount of oligomers is eliminated at treatment by different poliester manufacturers.

Because of this phenomenon many finishing plants have big problems of economical nature. Such coloured material has to be cleaned, whereby frequent textile cleaning is time-consuming and incomplete, but it is necessary to clean the colouring devices, as well, what causes a big loss of operation time. At the treatment of poliester sometimes so many oligomers are eliminated, that the powder can become a health problem, as well.

The manufacturers of dispersion dyes are trying to solve the problem with oligomers by introducing basic colouring. Hereby there are not enough basicproof dispersion dyes available for simple dye factory substitution of the conventional colour tones on poliester, acquired by the use of dispersion dyes by the acid procedure, with such incomplete palette of the selected basicproof dyes.

The pretreatment method of poliester for reducing elimination of oligomers at high-temperature acid colouring with dispersion dyes according to the invention, enables colouring by the conventional acid high-temperature colouring procedure of also such poliester materials, from which large amount of oligomers is eliminated. The method is based

on the pretreatment of poliester textile in basic bath with pH 11.5-12. 2 at 130°C and the subsequent triple washing in soft hot water. The basic bath is prepared with the appropriate amount of the basics and the corresponding puffer mixtures. Such pretreated poliester is then ready for colouring with dispersion dyes in acid medium, and no problems, connected with the oligomers, were noticed by the colouring.

In the basic bath with pH 11.5-12. 2 at 130°C large amount of oligomers melts, the surface of poliester is slightly etched, it becomes smoother and gets a nicer gloss.

Physical mechanical characteristics are not made worse thereby. In comparison to the characteristics by the blind basic colouring, as the base tear-extension of the poliester textile is increased, by this pretreatment of poliester textile no substantial changes of the tear-strength and the tear- extension were noticed.

With the aim to clearly present the effect of the method, described in the corresponding application, the following case is presented.

CASE: 100% poliester textile is used, washed with Teopon K (Teol) at 60°C and at 40°C, twice washed with water of room temperature. After washing the textile was thermofixated for 45 seconds at 190°C.

Such prepared textile was basic pretreated in laboratory colouring device Mathis JFL at bath-ratio 1: 10. For preparation of pretreatment bath

soft water was used. Pretreatment in the bath with 1 g/l of NaOH (pH 12) lasted 30 minutes at 130°C. Then triple washing in boiling soft water followed. Basic pretreated textile was then coloured at 135°C in blind acid bath, which contained 1 ml/I Eganal PS (Hoechst), 2 ml/l Lubit RL (Sybron /Tanatex) and CH3COOH 99-100% (J. T. Baker) up to the bath pH value of 4.5-5. The process of colouring was carried out according to the colouring diagram, which is recommended by DyStar company for colouring with Dianix AD dyes. After colouring the textile was four times washed in 40 °C warm soft water. On such treated textile then the content of oligomers was gravimetrically determined by means of extraction of poliester textile samples with petroleum and with dichlormethane (the method was arranged according to DIN 54278-1).

It was proven, that with 30 minutes basic pretreatment of poliester textile before acid colouring at 135°C, the content of oligomers was reduced by 44% with respect to the textile, coloured by acid colouring procedure at 135°C. The presence of oligomers in the extract was confirmed by means of gel permeable cromatography (GPC) and tetrahydrofurane as eluent. With this method it was found out, that in all extracts the cyclic trimer was mostly present, but the portion of the latter changes according to the way of treatment. In basically treated poliester textile the portion of the cyclic trimer in the extract of oligomers is almost 7 % smaller than in acidly coloured textile at 135°C, as well, what at 44% smaller content of total oligomers means 51.79% less cyclic trimer.

As the proof, that the basic pretreatment before the acid colouring does not influence the change of the colour tone, the colourimetrical values are given, measured on the sample, which was coloured by the acid colouring procedure with 0.4% Dianix Rot AD-2B and on the sample, which before the acid colouring with 0.4% Dianix Rot AD-2B was pretreated in the bath of 1 g/l NaOH 100% for 30 minutes at 130 °C. The values are given in CIE L*a*b* colour system: Front side of the poliester textile: DL* Da* Db* DC* DH* DE* 0.22 0.11-0. 24 0.11-0. 24 0.35 Back side of the poliester textile : DL* Da* Db* DC* DH* DE* 0. 29 0. 18-0.14 0. 18-0. 14 0.38 The colourimetrical values are the average values of three measurements on light-red coloured poliester textiles. The result DE*<1 means, that our eye does not recognize the change in colour. The values DE* 0.35 and DE* 0.38 are very low, what confirms the same colour.

Elimination of oligomers by this method does not influence the change of the colour tone of the poliester textile by acid high-temperature colouring.

By means of pretreatment in basic bath the elimination of oligomers by acid colouring at 135°C is reduced by 44%. The reduction as such ensures undisturbed colouring procedure of poliester in acid medium. By

basic colouring the content of oligomers is reduced by 62%, but today there are not enough basically stable dispersion dyes available for its realization. With the described pretreatment and the later acid colouring, poliester gets a nice gloss and a silky touch. The rigidness of such pretreated poliester is in comparison to the conventionally acidly coloured poliester rather reduced, and consequently it gets a softer touch.

Physical mechanical characteristics of the poliester textile do not deteriorate. The method according to the invention is especially recommended for colouring poliester curtains in satin and other types of binding, linings for coats and clothes, poliester textiles for clothes and poliester threads.