GB1561988A

GB1561988A - Process and apparatus for dyeing hydrophobic fibres

Info

Publication number: GB1561988A
Application number: GB32102/76A
Authority: GB
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1975-08-02
Filing date: 1976-08-02
Publication date: 1980-03-05
Also published as: DE2534618A1; DE2534618C3; CH612057GA3; IT1064723B; SE7608547L; BE844806A; DE2534618B2

Abstract

Textile materials consisting of hydrophobic fibres are dyed in a closed dyeing system with water-insoluble disperse dyes by the exhaust method. In the process, the dye is introduced into the already circulating aqueous dye-free liquor which has been heated to the dyeing temperature together with the textile material to be dyed. This is done by mixing, in a bypass of the liquor main circulation, the dye which has not been predispersed and is present as a powder or paste with a relatively small portion of the hot, dye-free liquor, to which turbulent flow has been imparted, under overpressure, returning it in this state via a nozzle system to the liquor main circulation and there dispersing it at the same time. The process has the advantage that the dyes used need only be slurried prior to introduction into the liquor main circulation, but no longer have to be predispersed or processed in any other way. Reproducibility of dyeings obtained when employing this process is better than that which can be achieved when employing so-called depot techniques.

Description

(54) PROCESS AND APPARATUS FOR DYEING HYDROPHOBIC FIBRES (71) We, HOECHST AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany. of 6230 Frankfurt/Main 80, Postfach 80 03 20, Federal Republic of Germany, 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 a process and an apparatus for the isothermal dyeing of hydrophobic fibers.

From German Auslegeschrift No. 2,235,110 a process for the hightemperature dyeing of hydrophobic fibers using water-insoluble disperse dyes is known, according to which a dyebath merely consisting of water acidifed to pH 4 to 6 is heated together with the material to an intended dyeing temperature of from 115 to 140"C. In the meantime, a dyestuff is dispersed in water of from 40 to 60"C in the usual manner in a separate container, and this dispersion is fed in a single portion into the hot dyebath via a kind of supplement "pocket" or an injector. This "pocket" consists of a bypass that is sealable from the dyeing system under pressure and which has a large container for the dyestuff dispersion. This dyestuff dispersion is distributed in the whole of the dye liquor by joining the bypass to the total circulatory system.The injector consists generally of an additional pump which conveys the dyestuff dispersion from a preparation container under atmospheric pressure to the pressurized dyeing system.

German Offenlegungsschfrift No. 2,256,116 discloses the isothermal dyeing of textile material made of polyester fibers using disperse dyes that are not added to the dyebath until the dyeing temperature has been reached. This known process, too, requires first dispersing the dyestuff in the dyeing medium used. Likewise, the dyestuff is added so as to avoid reduction in pressure as a result of certain apparatus being used.

Another process for the isothermal dyeing of hydrophobic organic polyester material using a liquor that is circulated through the material is known from German Offenlegungsschrift No. 2,330,622. According to this process, the dyestuffs which contain little or no dispersing agent are suspended in water of 90 to 950C.

Separately from the dyeing system, the suspension is heated to dyeing temperature, whereupon part of the dyestuff is dissolved and fed into the dyeing system of liquor and material that has also been heated. According to that disclosure, too, the dyestuff needs a preparatory treatment that is equivalent to a preliminary dispersing operation. Although containing little or no dispersing agent, the dyes used for that process are in a prepared state: they are standardized by extenders and ground. There is no disclosure in that specification concerning special requirements of a mechanical nature for the feed-in of the dyestuff.

All the above-said prior art methods have the common drawback that, prior to being fed into the dyeing circulation system, the dyestuff has to be dispersed or otherwise treated, thus generally necessitating major amounts of water (from 10 to 50 times the weight of the dyestuff). These amounts have to be heated to dyeing temperature either separately in suitable pressure-tight containers or, when added to the circulated liquor without being heated, they reduce the temperature thereof and therefore require special measures to compensate for the drop in temperature.

The present invention provides a process for the isothermal high-temperature dyeing of hydrophobic fibers which may be in the form of a textile material, in a closed dyeing system using water-insoluble disperse dyestuff according to the exhaust method, wherein the fibres are dyed from a circulating aqueous bath and the dyestuff is added to the already circulating, dyestuff-free liquor, which has been heated together with the fibres to a dyeing temperature in the range from 1150 to 140"C, preferably from 1200 to 1300C, and has a pH in the range of from 4 to 6, by withdrawing by suction a portion of the hot dyestuff-free liquor from the bath, passing the portion under excess pressure through a bypass system which is linked to the bath circulation system and includes a baffle arrangement to impart turbulence to the liquor portion, incorporating the non-dispersed dyestuff in the form of a powder or paste, into the turbulent liquor to form a concentrated dyestuff dispersion in the by-pass system, and discharging the resulting dispersion into the circulating liquor via a nozzle, postioned upstream of, preferably immediately before the inlet of, the circulation pump, to disperse the dyestuff therein.

Hence. this process may be carried out advantageously using commerical-type disperse dyes in the form of powders or pastes. These need not be dispersed previously. Thus, there is no need for a dyestuff dispersion to be heated to dyeing temperature, which would generally require an adequate autoclave of a certain capacity. The particular importance of the present invention, however, is primarily the fact that difficulties arising when pre-dispersed dyes are fed into hightemperature systems, from large liquor volumes and from a resulting temperature drop of the liquor, are avoided.The measures adopted according to the invention rather lead to the result that the heated dye-liquor is not noticeably increased in its volume by the addition of the (not separately heated) dyestuff dispersion, and thus the temperature is not reduced appreciably either, since hot liquor has been taken from the liquor circulation system to prepare it.

According to the process of the invention, the dyestuff as weighed is generally placed in a chamber which itself can be sealed in both directions by means of valves and which is included in a bypass system. With the aid of an efficient pump, which is also included in the bypass system and precedes the chamber, a portion of liquor is sucked in-with the valves of the bypass opened--directly from the circulated liquor and, after being mixed with the dyestuff in the chamber, forced back into the circulation system by means of a nozzle functioning as a mixing element, for example a cone-shaped nozzle. The effect of the nozzle allowsithe dyestuff to be dispersed directly in the circulating liquor.The portion of liquor has already been brought to dyeing temperature and does not cool down appreciably during its short passage through the chamber and the nozzle. To accelerate distribution of the dispersed dyestuff in the dye-liquor, the nozzle is advantageously arranged upstream immediately before the circulation pump in the liquor circulation system.

The process of the invention may therefore be applied preferably to dyeing in installations using circulated liquor, i.e. in dyeing installations for cross-wound bobbins and in beam-dyeing and jet dyeing installations, but also high-temperature winch becks which are provided with liquor circulation systems.

The present invention also provides an apparatus for carrying out the process of the invention, for the isothermal high-temperature dyeing of hydrophobic fibers in a closed dyeing system using a water-insoluble disperse dyestuff according to the exhaust method, the apparatus consisting of a pressure-tight dyeing container which houses a support for the fibre material to be dyed, in connection with a pipeline for the formation of the liquor circulatory system, a circulating pump for the liquor to be circulated, and an element for reversing the circulating direction of the liquor flow from the inside to the outside through the material or vice verso and the apparatus being characterized in that the liquor circulation system is provided with a bypass which comprises the following constructional elements arranged in the order set forth below: : (a) a pump for the liquor feed, (b) a valve which is capable of opening under the pressure of the liquor taken in by suction and pressurized by the pump, (c) baffle elements placed in the feed pipe and for causing turbulence in the liquor, (d) a pressure-tight chamber for the dyestuff, which is accessible from outside through a sealable aperture, (e) a valve which opens only under pressure in the direction from the chamber, generally a non-return valve, and (f) a nozzle which seals the bypass merging into the liquor circulation system upstream of, preferably immediately before the inlet of, the circulating pump, for discharging the liquor in the by-pass into the circulating liquor, The apparatus of the invention is illustrated diagrammatically, by way of example only, in the accompanying drawing.This drawing is a partly exploded side view of this apparatus, in which 1 is a dyeing container, la is the material to be dyed, 2 is a circulation pump for circulating the liquor, 3 is a take-in pipe for the bypass, 4 is a pump, 5 is an automatic valve, 6 is a chamber for the dyestuff, 7 is a sealable aperture of the chamber for introducing the dyestuff.

8 is a draining valve (cock) for the chamber, 9 are baffle elements for causing turbulence in the liquor, 10 is a non-return valve, I I is a mixing nozzle, 12 is a circulation pipe for the dyeing liquor, 13 is a device for reversing the circulation direction of the liquor in the dyeing container, and 14 is a venting valve for the chamber 6.

The functioning of the apparatus of the invention is illustrated by way of example of a yarn-dyeing apparatus which is equipped with a bypass system as described above. Via a pipe (3), an efficient pump (4) takes by suction a certain amount of hot liquor into a bypass from a dyeing container (1). The liquor is passed through an automatic valve (5) and through baffle elements (9), arranged in staggered position against one another, into a closed chamber (6), into which the non-dispersed commercial-type dyestuff has been placed in the form of a dry powder or a paste. The baffle elements (9) cause a strong turbulence in the liquor fed into the chamber, thus bringing about thorough and rapid mixing of the dyestuff powder or paste with the liquor.At the same time, the pump (4) generates in the chamber (6) a liquor pressure which, when reaching the level of the static pressure in the whole dyeing system, is sufficiently high for the opening of valve (10). This valve is therefore advantageously a non-return valve. A nozzle (11) extends into a pipe (12) feeding the circulation pump (2). Through valve (10), the liquor mixed with the dyestuff is then discharged toward the nozzle, where it is finely divided and injected into the circulating dyeing liquor. The nozzle brings about not only fine division of the liquor but also dispersion of the dyestuff contained therein in the circulated dyeing liquor, which is now ready for use. The size and efficiency of the separate elements of the apparatus are correlated to the layout of the dyeing apparatus.For example, in a dyeing apparatus holding 100 kg of material to be dyed, the chamber (6) has to contain from 10 to 15 kg of dyestuff powder, for instance in the case of black dyeings. It will therefore be designed for a capacity of from 10 to 50 1, preferably of 30 1, in order to have enough room available for mixing with the liquor taken in. The pump (4) is sized so as to generate a pressure of from about 3 to 4 bars at its delivery side at a throughput of at most 50 I/minute. This pump efficiency is also correlated to the nozzle (throughput: 30 to 50 I/minute). The nozzles used may be of various types, for example cone type or fan type nozzles. They are installed in the liquor circulation system so as to allow a fast and homogeneous atomizing of the liquor containing the dyestuff in the circulated dyeing liquor.

To fill the chamber (6) with the dyestuff, operation of the liquor bypass system (3 to 11) is interrupted by switching off pump (4) which results in the shutting of valves (5) and (10). The chamber is drained by opening the draining valve (8), which may be a simple cock or tap, and the filling aperture (7). The valve (8) is then closed, and the dyestuff is placed into the chamber in the form of a powder or a paste. The chamber is then closed again by means of the sealing plate (7). It is important for the valve (5) to open up instantly and to seal rapidly in order to permit a high flow rate. As the whole dyeing system, at a temperature of from 115 to 1400C, is under static pressure, the valve (10) may be a non-return valve which closes in the direction of the liquor circulation system toward the chamber, as soon as the pump (4) is switched off, i.e. the valve (5) is shut.The valve (5) is advantaeously connected with the pump so as to open only with the pump in operation. After the chamber is filled with dyestuff, and the pump (4) is switched on, the liquor is sucked in from the dyeing container (1) and pumped into the chamber through the valve (5) and the baffle elements (9) which cause a strong turbulence (rotational movement). There, it is mixed with the dyestuff and, after the valve (10) operates, it is fed back into the dyeing liquor circulation system through the nozzle. Thus the dyestuff is dispersed directly in the dyeing liquor.

Compared with the prior art methods cited above, the process of the invention has the advantage that the dispersing of the dyestuff is not left to any hazards in the manual preparation of the liquor. Large pressure-tight vessels which permit the heating of the dispersion to dyeing temperature are no longer required. Dyestuff may be added at any time and at any temperature. The dyeing temperature is not subiect to variations due to the addition of dyestuff.

The feed-in of even major amounts of dyestuff is complete within at most one minute. The process is suitable not only for aqueous liquor of water-insoluble dyes.

In addition water-soluble dyes, as well as chemical agents and adjuvants may be added to the dyebath by means of this apparatus, as well as liquors that consist partly of organic solvents; the dyeing apparatus remains universally useful in spite of the lack of the usual large preparation vessels.

The following Examples illustrate the invention.

EXAMPLE I 50 Kilograms of a knit fabric made of texturized polyester fibers are wound up on a dyeing beam and placed in a HT-dyeing apparatus (1) equipped with a bypass system (3 to 11) as shown in the accompanying drawing. The apparatus is filled with 750 1 of hot water, whose pH is adjusted to 5 by adding acetic acid. After putting the circulation pump (2) into operation, the system is heated rapidly to 1300 C. 1.3 Kilograms of the pulverulent red disperse dyestuff of the formula

(in a commercial quality) are placed into the chamber (6) of the bypass system, that has been emptied of liquor, and this is closed. After putting the pump (4) into operation, the dyestuff is dispersed in the dyebath. The additional pump (4) is switched off again after 1 to 1.5 minutes.The dyeing liquor is circulated for another 20 minutes at 1300C, then cooled to about 90"C and removed from the apparatus.

The after-treatment of the dyeing is performed in the usual manner under reductive/alkaline conditions.

A very level red dyeing of good fastness to rubbing is obtained. During the dyeing period, liquor samples were taken at intervals of 5 minutes beginning 5 minutes after addition of the dyestuff, and the exhaust degree of the liquor was determined by extinction measuring on a DK 2 spectrophotometer (Beckman Instruments) with a supplementary remission device. The following values resulted therefrom: After 5 minutes=97.85 after 10 minutes=98.36% after ij minutes=99.21% after 20 minutes=99.9 %.

EXAMPLE 2 A jet dyeing installation of 1,300 1 capacity, equipped with a bypass system as shown in the accompanying drawing is filled with 75 kg of a markedly structurized knit fabric consisting of texturized polyester fibers and with water whose pH is adjusted to 5 (by means of acetic acid). Circulation is started, and the installation is heated as rapidly as possible to 1250C.

Into the chamber (6) of the bypass, which has been cleared of old liquor, 1,125 g of the pulverulent yellow-brown disperse dyestuff of the formula

338 g of the pulverulent red disperse dyestuff of the formula

and 487 g of the pulverulent blue disperse dyestuff consisting of a mixture of about equal parts of the dyestuffs of the formulae

(all these dyes in commercial quality) are placed, and the chamber is closed. The additional pump (4) is put into operation, and the dyestuff is dispersed in the dyeing liquor by means of the bypass. After 1 to 2 minutes, the additional pump is switched off again. The material is then dyed for 25 minutes at 1250C, the bath is then cooled to 90"C, the dyeing is rinsed with water and cleaned in the usual manner under reductive/alkaline conditions.

A completely level brown dyeing with full color yield was obtained without damage to texturation and structure of the knit fabric.

EXAMPLE 3 50 Kilograms of texturized polyester filaments in the form of a core-less wound package have been dyed according to the method described in Example 1, using 750 g of the pasty yellow disperse dyestuff of the formula

and 300 g of an also pasty blue disperse dyestuff consisting of a mixture of equal parts of the dyestuffs of the formulae

in 750 1 of dye liquor. Color matching showed that another 100 g of the blue dyestuff have to be added to yield the desired green shade. This dyestuff amount is dispersed in the liquor at 1300C by means of the said device. After another dyeing time of 20 minutes, the dyeing is again matched to shade. The dyeing which is now the desired shade is rinsed and cleaned as usual under reductive/alkaline conditions. A green dyeing with a satisfactory levelness is obtained.

WHAT WE CLAIM IS: 1. A process for the isothermal high-temperature dyeing of hydrophobic fibres in a closed dyeing system using a water-insoluble disperse dyestuff according to the exhaust method, wherein the fibres are dyed from a circulating aqueous bath and the dyestuff is added to the already circulating, dyestuff-free liquor, which has been heated together with the fibres to a dyeing temperature in the range of from 1150 to 140"C and has a pH in the range of from 4 to 6, by withdrawing by suction a portion of the hot dyestuff-free liquor from the bath, passing the portion under excess pressure through a by-pass system which is linked to the bath circulation system and includes a baffle arrangement to impart turbulence to the liquor portion, incorporating the non-dispersed dyestuff, in the form of a powder or paste, into the turbulent liquor to form a concentrated dyestuff dispersion in the bypass system, and discharging the resulting dispersion into the circulating liquor via a nozzle, positioned upstream of the circulation pump, to disperse the dyestuff therein.

2. A process as claimed in claim 1, wherein the nozzle is positioned immediately before the inlet of the circulation pump.

3. A process as claimed in claim 1 or claim 2, wherein the aqueous bath has a temperature in the range of from 1200 to 1350C.

4. A process as claimed in any one of claims 1 to 3, wherein a textile material comprising hydrophobic fibres is dyed.

5. A process as claimed in claim 1 conducted substantially as described herein.

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

Claims

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

and 487 g of the pulverulent blue disperse dyestuff consisting of a mixture of about equal parts of the dyestuffs of the formulae

(all these dyes in commercial quality) are placed, and the chamber is closed. The additional pump (4) is put into operation, and the dyestuff is dispersed in the dyeing liquor by means of the bypass. After 1 to 2 minutes, the additional pump is switched off again. The material is then dyed for 25 minutes at 1250C, the bath is then cooled to 90"C, the dyeing is rinsed with water and cleaned in the usual manner under reductive/alkaline conditions.

A completely level brown dyeing with full color yield was obtained without damage to texturation and structure of the knit fabric.

EXAMPLE 3

50 Kilograms of texturized polyester filaments in the form of a core-less wound package have been dyed according to the method described in Example 1, using 750 g of the pasty yellow disperse dyestuff of the formula

and 300 g of an also pasty blue disperse dyestuff consisting of a mixture of equal parts of the dyestuffs of the formulae

in 750 1 of dye liquor. Color matching showed that another 100 g of the blue dyestuff have to be added to yield the desired green shade. This dyestuff amount is dispersed in the liquor at 1300C by means of the said device. After another dyeing time of 20 minutes, the dyeing is again matched to shade. The dyeing which is now the desired shade is rinsed and cleaned as usual under reductive/alkaline conditions. A green dyeing with a satisfactory levelness is obtained.

WHAT WE CLAIM IS: 1. A process for the isothermal high-temperature dyeing of hydrophobic fibres in a closed dyeing system using a water-insoluble disperse dyestuff according to the exhaust method, wherein the fibres are dyed from a circulating aqueous bath and the dyestuff is added to the already circulating, dyestuff-free liquor, which has been heated together with the fibres to a dyeing temperature in the range of from 1150 to 140"C and has a pH in the range of from 4 to 6, by withdrawing by suction a portion of the hot dyestuff-free liquor from the bath, passing the portion under excess pressure through a by-pass system which is linked to the bath circulation system and includes a baffle arrangement to impart turbulence to the liquor portion, incorporating the non-dispersed dyestuff, in the form of a powder or paste, into the turbulent liquor to form a concentrated dyestuff dispersion in the bypass system, and discharging the resulting dispersion into the circulating liquor via a nozzle, positioned upstream of the circulation pump, to disperse the dyestuff therein.
2. A process as claimed in claim 1, wherein the nozzle is positioned immediately before the inlet of the circulation pump.
3. A process as claimed in claim 1 or claim 2, wherein the aqueous bath has a temperature in the range of from 1200 to 1350C.
4. A process as claimed in any one of claims 1 to 3, wherein a textile material comprising hydrophobic fibres is dyed.
5. A process as claimed in claim 1 conducted substantially as described herein.
6. A process as claimed in claim 1, conducted substantially as described in any

one of the Examples.
7. An apparatus for carrying out the process as claimed in claim 1, consisting of a pressure-tight dyeing container which houses a support for the fibre material to be dyed, in connection with a pipeline for the formation of the liquor circulatory system, a circulating pump for the liquor to be circulated, and an element for reversing the circulation direction of the liquor flow from the inside to the outside through the material or vice versa, and the apparatus being characterized in that the liquor circulation system is provided with a bypass which comprises the following constructional elements arranged in the order set forth below:: (a) a pump for the liquor feed, (b) a valve which is capable of opening under the pressure of the liquor taken in by suction and pressurized by the pump (c) baffle elements placed in the feed pipe and for causing turbulence in the liquor, (d) a pressure-tight chamber for the dyestuff, which is accessible from outside through a sealable aperture, (e) a valve which opens only under pressure in the direction from the chamber, and (f) a nozzle which seals the bypass merging into the liquor circulation system upstream of the circulating pump, for discharging the liquor in the bypass into the circulating liquor.
8. An apparatus as claimed in claim 7, wherein the nozzle is positioned immediately before the inlet of the circulation pump.
9. An apparatus as claimed in claim 7 or claim 8, wherein the valve (e) is nonreturn valve.
10. An apparatus as claimed in claim 7, substantially as described herein with reference to, and as illustrated in, the accompanying drawing.