EP0237893A1 - Method for wet-treating a textile material - Google Patents

Abstract

For the treatment of textile material, in particular with capillary-active properties, for example in the form of yarn spools (16), these are inserted into a treatment vessel (1) in which there is a heated liquid in which chemicals are dissolved. With the help of a vacuum pump (11), which is connected via an intermediate vessel (9), a liquid separator (3), pipes (2, 6) and valves (2 ', 6', 4, 5), the treatment vessel (1) such a negative pressure creates that the liquid boils strongly. At the same time, gas, for example nitrogen, air or oxygen, is introduced into the liquid via a valve (13), whereupon the entire liquid volume changes into a fine-pored foam. An intermediate treatment section adjoins such a vacuum treatment section. The gas valve (13) is closed and the liquid is pumped around with the aid of a circulation pump (12), as is known. The liquid is heated up again and the vacuum is built up again.

Description

The invention relates to a method for liquid treatment, in particular for cleaning, bleaching, pickling, dyeing, fixing and the like of textile material, in particular with capillary properties in the form of flakes, yarns or piece goods, by means of chemicals dissolved in the liquid, the chemicals being in a container filled liquid temporarily or alternately only by partial evaporation, which is controlled by a controlled pressure reduction in the container, is moved and thereby brought to act on the material, and the liquid during its action on the material by introducing a gaseous medium also a pulsating movement is given.

Bleaching is the decolorization of materials, especially through oxidation or reduction. The chemicals used and the process engineering must be carefully coordinated with the respective materials. Since many chemicals such. B. decompose quickly when heated, stabilizers are needed to slow the decay. However, these stabilizers make bleaching more expensive and complicated.

Dyeing is generally used to denote the process by which an undyed or achromatic fabric is given a color or a colored fabric is given another color. The dye goes through adsorption on the surface, through diffusion, through formation on or in the fiber or through chemical bonding to the material. The treatment takes place predominantly in aqueous solutions or in suspensions of dyes with the addition of dyeing aids, such as wetting agents, salts, alkalis, acids, etc. The goods are either moved in the resting liquor or the liquor flows through the goods.

Special dyeing processes are the jet, high temperature, pad roll, pad steam, stand fast and thermosol processes.

Foam dyeing is well known, although not very common. Here, bubbles are created in the liquor by adding foaming agents, with the aid of which special dyes, the molecules of which have both hydrophilic and hydrophobic ends, are transferred to the material to be dyed.

Dyeing processes are also known which use other solvents instead of water, mostly volatile hydrocarbons. However, these methods were not used in practice because of the harmful, often even toxic or explosive properties of the solvents.

The aim of all dyeing processes is to produce a connection between the dyes and the material to be dyed with as little effort as possible, the strength and resistance of which are decisive for the degree of authenticity of the dyeing. The processes involved are partly chemical and partly physical. Especially in the case of capillary-active fibers, the best known of which are wool and cotton, although synthetic fibers are not excluded, the physical processes based on the capillary and osmotic forces clearly outweigh them. These work in the same way for both cold and cook dyeing, decolorization and bleaching.

The bleaching and dyeing processes are largely time and energy intensive. The fleet and / or the material must be moved evenly. In particular, the temperature must be brought to the correct values, and a temperature increase to or above 100 degrees C is often prescribed during the process.

DE-A-27 14 802 discloses a dyeing process for textile goods consisting of natural fibers or plastic fibers or their mixtures, in which the dyeing is carried out under reduced pressure. The temperature of the liquid is kept at the boiling point for about 10 minutes, taking into account the prevailing negative pressure. The pressure and temperature are then quickly increased and the textile material is finally dyed in the conventional process. This known method is said to result in more intensive coloring with a shorter treatment time and reduced energy expenditure. This is essentially attributed to the fact that a large part of the air, which usually hinders the wetting of the textile material with liquid, is sucked off by the vacuum. The treatment is gentle because of the reduced temperatures and the shortened time. Better use of the dyes was also observed. By reducing the proportion of air in the treatment vessel, dyes that are sensitive to certain gas components in the air can also be processed more easily.

Another process for treating textile materials under vacuum is known from EP-B-22 572. In this case, the liquid is moved essentially exclusively by local partial evaporation as a result of a controlled reduction in pressure in the treatment tank, and is thereby brought into effect on the material. The entire dyeing process is carried out under vacuum; dyeing under normal pressure while pumping around the liquid is not intended. As the liquid cools down during the constant partial evaporation, it is continuously reheated. This reheating should preferably be carried out by introducing steam directly. As a result of the negative pressure in the treatment vessel, the vapor bubbles entering the liquid relax explosively. On the one hand, this causes the liquid to pulsate; on the other hand, these explosions are so strong that sensitive materials such as spooled yarn can be destroyed. The liquid is heated by the supplied steam, which increases the evaporation and the vacuum breaks down, unless a very powerful and therefore expensive vacuum pump is used.

Another disadvantage is that technical steam is regularly contaminated, especially with iron. Many dyes, especially the indant dyes, are adversely affected or even destroyed by steam. The known method is therefore only really useful for a relatively small number of dyes.

Finally, it should be pointed out that the steam supplied condenses at least partially into water, so that the treatment liquid is diluted. However, this extends treatment times and worsens the results. Foaming, as is desirable in some cases, also does not occur.

The present invention has for its object to provide a method of the type mentioned, which is fast, energy-saving and inexpensive, but in which the goods are treated even more gently and which allows a particularly simple and effective control of the process conditions.

This object is achieved in that such a gaseous medium is used which has an oxidizing, neutral or reducing effect with the liquid and / or the material, but does not change the quantitative ratio of chemicals to the liquid, that at the beginning of the vacuum treatment section the temperature of the liquid a value is brought that is substantially above the boiling point of the liquid at the current tank pressure lies, and that after such a vacuum treatment section, an intermediate treatment section is inserted, in the course of which the liquid is reheated and the vacuum is re-established if necessary.

This has the advantages that, in addition to the known effects of vacuum treatment - energy savings due to lower temperatures of the liquid, rapid and complete reaction of the chemicals, protection of the material, the liquid is additionally moved in a particularly gentle manner, since when gas is supplied, which is not steam, the entire liquid volume turns into an extremely fine-pored foam. Since the gas, unlike steam, does not condense, the concentration of chemicals in the liquid is not reduced; on the contrary, the constant evaporation of the liquid due to the reduced pressure increases it continuously. On the other hand, the progressive cooling of the liquid does not evaporate too much, so that it is also possible to work with relatively weak vacuum pumps.

This vacuum treatment section is then followed by an intermediate treatment section, in the course of which the liquid is reheated and, if appropriate, the vacuum is built up again. The method according to the invention essentially consists of these two treatment sections, which are repeated alternately until the desired result is achieved.

During the intermediate treatment section, the liquid is preferably pumped around in a manner known per se, specifically by means of a heater and / or in a manner known per se through the material. The treatment process is not completely interrupted.

It is basically possible to take the liquid even during of the vacuum treatment section. However, many pumps tend to cavitate due to the vacuum.

According to a preferred embodiment of the invention, the connection to the vacuum pump is shut off at the beginning of the vacuum treatment section. The vacuum is continuously reduced by supplying gas and evaporating the liquid, so that the vacuum treatment section stops by itself. This has the advantage that the vacuum pump does not have to be in constant use. The main advantage of this measure, however, can be seen in the fact that the supplied gas collects above the liquid, so that it does not get into the vacuum pump, but rather forms a gas cushion.

According to a preferred development of the invention, the gas supply is shut off at the end of the vacuum treatment section and the gas is sucked off above the liquid before the intermediate treatment section begins. The gases can be returned to the process or removed safely.

According to a preferred development of the invention, the temperature of the liquid is always below 100 degrees C, when treating cotton preferably between approximately 70 and 60 degrees C. In this special area, cotton can be dyed particularly quickly. Moreover, the treatment of the material is gentle at low temperatures, the liquid only needs to be heated slightly, which saves energy, and the vacuum required for the process according to the invention is still in areas which can be produced using inexpensive vacuum pumps.

According to a further embodiment of the invention, chlorine, for example, is used as the reducing gas, oxygen or air, for example, as the oxidizing gas, and nitrogen, for example, as the neutral gas. For example, for dyeing with oxidative dyes, first using Nitrogen the required neutral atmosphere, then the required oxidizing atmosphere can be adjusted by using air, possibly also oxygen.

According to a development of the invention, the negative pressure can be generated abruptly, for example by quickly opening a connecting line with a large cross section between the treatment vessel and an evacuated intermediate vessel. In this way, an intensive movement of the liquid and the material inside is achieved.

The material can also be continuously dipped out of the liquid and then immersed in it again. When immersed, the liquid hanging on the material evaporates due to the prevailing negative pressure; at the same time, however, the material remains in the gas cushion built up above the liquid, which, depending on the gas used, has neutral or reactive properties.

A foaming agent can be added if necessary in order to intensify the intensive foam formation occurring in the entire liquid volume in the process according to the invention.

In order to achieve a special degassing of the material to be treated, the negative pressure can be generated in the treatment vessel before the liquid is brought into contact with the material. The effects that can be achieved in this way are generally known. It should be emphasized here that the method according to the invention brings excellent results even without this pre-evacuation.

If certain materials, for example polyester, have to be fixed at elevated temperatures, the pressure and temperature in the container can be increased, for example to usual values of approx. 130 degrees C at pressures of just under 3 bar.

Finally, in the method according to the invention, the liquid can also be indirectly, for example during the vacuum treatment section. B. heated by heat exchangers.

• Fig. 1 eine Vorrichtung zum Färben von aufgespulten Garnen und
• Fig. 2 eine Vorrichtung zum Färben von Textilbahnen.

The invention will be explained in more detail with reference to the drawing and the two apparatuses shown therein. Show it:

• Fig. 1 shows a device for dyeing wound yarn and
• Fig. 2 shows a device for dyeing textile webs.

1 shows a closed, vacuum-tight treatment vessel 1, in particular for dyeing bobbins of thread, which are symbolized by a single bobbin of yarn 16. The treatment vessel is partially filled with liquid in which color chemicals are dissolved.

A pipe 2 leads from the cover of the treatment vessel 1 to a liquid separator 3. A valve 15 establishes a connection between the treatment vessel 1 and the surrounding atmosphere. A valve 2 establishes a connection between the pipeline 2 and the liquid separator 3.

From the bottom of the liquid separator 3, a line 8 with a valve 8ʹ inserted leads to a circulating pump 12 or into the treatment vessel 1. Via line 8, liquid that collects in the liquid separator 3 is returned to the treatment vessel 1.

A pipe 6 leads from the liquid separator 3 to an intermediate vessel 9 to which a vacuum pump 11 connected. Liquid that collects in the intermediate vessel 9 can be discharged via a drain valve 10.

A drain valve 14 serves to empty the treatment vessel 1.

Gas is supplied via a valve 13.

In this device, the yarns 16 are treated as follows. After inserting the yarns 16 and closing the treatment vessel 1, the liquid is filled in until the yarns 16 are covered. The valves 4, 8ʹ, 10, 13, 14 and 15 are closed. The intermediate vessel 9, the liquid separator 3 and the treatment vessel 1 are evacuated with the aid of the vacuum pump 11. One of the valves 2ʹ, 6ʹ or 5 can also be closed. The liquid in the treatment vessel 1 is at a temperature of, for example, 70 degrees C. The pressure in the intermediate vessel 9 is reduced to, for example, 0.1 bar absolute. This corresponds to a water boiling temperature of approx. 45 degrees C.

As soon as this negative pressure reaches the treatment vessel 1 by opening the previously closed valves 2ʹ, 6ʹ or 5, the liquid begins to boil violently. At the same time, the valve 13 is opened and gas is introduced, which preferably bubbles through the yarn bobbins 16 from the inside to the outside. As soon as the gas, for example air, comes into contact with the liquid, the entire volume of liquid changes into a fine-pored foam which influences the chemicals dissolved in the liquid in such a way that they preferentially settle on the fibers of the yarns 16. The dyes are absorbed very quickly.

As part of the water evaporates when the liquid is boiled, the concentration of chemicals increases, which is desirable.

The supplied gas is sucked off via the vacuum pump 11. The aspirated liquid vapor is separated in the liquid separator 3 and actuates the level switch 7. This liquid can later be returned to the treatment vessel via the line 8 with the valve 8ʹ open.

As a result of the liquid evaporation and the gas supply, the temperature of the liquid drops, the evaporation process therefore comes to a standstill if the liquid is not heated using a heat exchanger to be installed in the treatment vessel.

At the latest now, the connection to the vacuum pump 11 is blocked, for example by closing the valve 2ʹ. The gas valve 13 is closed and the circulation pump 12 is switched on. Since the pressure in the treatment vessel 1 and the temperature of the liquid are now in equilibrium, there is no danger that 12 cavitations will occur in the circulation pump.

During this intermediate treatment section, the temperature of the liquid is increased again and at the same time the liquid is pressed through the yarn packages 16, as in the conventional dyeing processes. If the pressure in the intermediate vessel 9 has risen because the vacuum pump 11 has only a small capacity, the vacuum is also built up again.

Vacuum treatment section and intermediate treatment section are repeated alternately until the desired treatment result is achieved.

It should be emphasized here again that the gases supplied through the valve 13 are those which do indeed of the liquid or the chemicals dissolved in it, but do not dilute the chemical concentration as is the case when using steam. Finally, it should be emphasized here that a fine-pored foam is formed when gas is introduced into the liquid. Such a foam does not appear when steam is introduced; the introduced steam bubbles explode explosively due to the negative pressure in the treatment vessel 1, so that there is a risk of damage to the materials to be treated.

A device for treating longer textile webs can be seen in FIG. In a treatment vessel 22 which is partially filled with liquid there is a basket 23 which receives a part of the material web 40. This is continuously guided in a circle by means of a driven deflecting roller 24 and a reel 30 with an elliptical cross section. As a result, it is partly below, partly above the liquid. The opening for inserting and removing the web 40 can be closed with a lid 25 in a vacuum-tight manner.

In order to be able to generate negative pressure in the treatment vessel 22, a vacuum pump (not shown) is connected to the vacuum valve 29 of the liquid separator 28. A vacuum intermediate vessel is not absolutely necessary here because the free space in the treatment vessel 22 is very large. The other valves are closed. The liquid is again heated to a temperature of, for example, 70 degrees C. The pressure in the vessel 22 is again reduced so much that the liquid boils strongly.

By opening the valve 38, gas is introduced into the liquid at several points, whereupon a fine-pored foam is formed.

After opening the valve 38, the valve 29 can go to the vacuum pump getting closed. The introduced gas then collects in the treatment vessel 22 above the liquid. The vacuum treatment section consequently comes to a standstill when the negative pressure has risen to such an extent that the boiling point of the liquid has been reached. Now this gas can be extracted via one of the valves 26, 27 and either reused or safely removed. It does not get into the vacuum pump.

The part of the web 40 which is outside the liquid is slightly dried due to the negative pressure prevailing there, as a result of which the chemicals are deposited particularly quickly in the fabric. Nevertheless, this part of the web is also under a gas cushion. If it is a reactive gas, such as oxygen or air, the chemical reactions continue. If it is a neutral gas, such as nitrogen, undesirable chemical reactions are prevented.

A vacuum treatment section is followed by an intermediate treatment section, in the course of which the liquid is circulated via an open valve 37 and an open valve 33 with the aid of a circulation pump (not shown). At the same time, the liquid is heated, either via a heating coil 21 installed in the treatment vessel 22 or via an external heat exchanger. The heating of the liquid by directly introduced steam should be avoided because of the disadvantages already described.

Liquid that collects in the liquid separator 28 is returned to the treatment vessel 22 via a valve 31 as soon as the level switch 39 is actuated.

Via a valve 36 further liquid, for example with fresh chemicals, can be added to the Treatment vessel 22 are initiated.

A valve 34 serves as an overflow valve.

Claims (15)

1. Process for liquid treatment, in particular for cleaning, bleaching, pickling, dyeing, fixing and the like of textile material, in particular with capillary-active properties in the form of flakes, yarns or piece goods, by means of chemicals dissolved in the liquid, the liquid being filled into a container at times or alternately essentially only by partial evaporation, which is controlled by a controlled pressure reduction in the container, is moved and thereby brought to act on the material, and wherein the liquid during its action on the material by introducing a gaseous medium also a pulsating Movement is given, characterized in that such a gaseous medium is used which has an oxidizing, neutral or reducing effect with the liquid and / or the material, but does not change the quantitative ratio of chemicals to the liquid, that at the beginning of the vacuum treatment section the temper Ature of the liquid is brought to a value which is substantially above the boiling point of the liquid at the current container pressure, and that after such a vacuum treatment section, an intermediate treatment section is inserted, in the course of which the liquid is reheated and the vacuum is possibly built up again. 2. The method according to claim 1, characterized in that in the intermediate treatment section and / or in the vacuum treatment section, the liquid is pumped over as is known. 3. The method according to claim 1 or 2, characterized in that at the beginning of the vacuum treatment section, the connection to the vacuum pump is shut off. 4. The method according to claim 1, 2 or 3, characterized in that at the end of the vacuum treatment section the gas supply is blocked and the gas is sucked off above the liquid. 5. The method according to at least one of claims 1 to 4, characterized in that the temperature of the liquid is always below 100 degrees C. 6. The method according to at least one of claims 1 to 5, characterized in that the temperature of the liquid is adjusted to about 70 to 60 degrees C for the treatment of cotton. 7. The method according to at least one of claims 1 to 6, characterized in that the gas is introduced into the liquid at several points. 8. The method according to at least one of claims 1 to 7, characterized in that as a reducing gas z. B. chlorine, as an oxidizing gas such. B. oxygen or air, as a neutral gas z. B. nitrogen is used. 9. The method according to at least one of claims 1 to 8, characterized in that the material is continuously immersed during the treatment from the liquid and immersed in this again. 10. The method according to at least one of claims 1 to 9, characterized in that for dyeing with oxidative dyes first with neutral gas, for. B. nitrogen, then with oxidizing gas, e.g. B. air or oxygen. 11. The method according to at least one of claims 1 to 10, characterized in that the negative pressure is suddenly generated. 12. The method according to at least one of claims 1 to 11, characterized in that a foaming agent is added to the liquid. 13. The method according to at least one of claims 1 to 12, characterized in that the negative pressure is generated before the liquid is brought into contact with the material. 14. The method according to at least one of claims 1 to 13, characterized in that for fixing or intermediate fixing pressure and temperature in the container, optionally to values above 100 degrees C, are increased. 15. The method according to at least one of claims 1 to 14, characterized in that the heating of the liquid also takes place during the vacuum treatment section by heat exchangers.

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