EP0311796B1 - Method for wet treatment of sheet-like materials - Google Patents

Description

The invention relates to a method according to the preamble of claim 1.

The starting point of the invention has been problems which have been pending for a long time in continuous dyeing with direct dyes (noun dyes) (see Fischer-Bobsien "International Lexicon textile finishing + border areas" 4th edition 1975, columns 419-422). The dyeing liquor can be applied in a foulard, so that the web is passed through the larger amount of dyeing liquid in the pool of the foulard. This has resulted in unavoidable end processes, both at the beginning and at the end of the web. When passing the first parts of the web through the fleet in the basin, parts of the fleet are towed out of the web, which cause a corresponding depletion of the fleet, which must be readjusted. It takes a certain amount of time before an equilibrium relationship has been established and the concentration of the fleet remains constant. By the time this condition is reached, an end run of 50 to 150 m has occurred. Such lengths of goods with a different and in particular not constant color tone cannot be used together with the rest of the goods are used, but are sold as lower qualities or over-dyed black. In any case, these end processes result in a certain previously unavoidable loss.

Another problem is the fact that the direct dyes do not fully absorb and the non-fixed portions on the web are washed out after steaming. The dye yield, i.e. the ratio of the dye actually fixed on the goods to the dye originally applied is far from complete, but is in the order of 60%. The undrawn 40% "go into the sewer" and are not only a very significant cost factor, but also a difficult environmental problem, especially since many molecules of direct dyes contain complex-bound heavy metal ions, especially copper ions, which are considered to be a dangerous waste water poison and with regard to their strict official regulations.

It is now known that the application of direct dyes to the goods can be improved by adding salts such as table salt or Glauber's salt. This is evident from the scripture underlying the generic term from M. Peter's book "Fundamentals of textile finishing" 12th edition (1985) pp. 154/155. Here, salt and dye are applied in one and the same liquor. In this way, the proportion of the dye that is actually absorbed on the fibers can be increased and thus the loss of dye on the one hand and the environmental impact on the other hand can be reduced.

In the continuous process, however, the addition of salt to the dye bath in the foulard increases the end processes. The salt increases the drawability of the goods so that they eagerly take up dye from the liquor and the amount of liquor at the beginning and towards the end becomes even stronger and shows changes in concentration that are difficult to control. The means of salt addition, which is per se tried and tested to improve the dye yield and the environmental impact, cannot therefore be readily used in continuous dyeing.

On the basis of this special problem, the invention is based on the object of designing a method in such a way that a uniform treatment failure occurs over the length of the web.

This object is achieved in its procedural aspect by the invention reproduced in claim 1.

The method is primarily considered for the treatment of flat fabrics. In such a web, the first treatment liquor, which is either the salt liquor or the color liquor, the other liquor following in the subsequent second step, is applied in some way and then squeezed to 60 to 120%. The moisture values always relate to the amount of treatment liquor in relation to the dry weight of the web to which the treatment liquor has been applied. A value of 120% is the upper limit of what can still be squeezed evenly in a squeezing device with interacting rollers; at higher moisture contents, the squeezing mechanism would have to be driven with line pressures so low that the uniformity of the squeezing would no longer be guaranteed and there would even be a risk of the rollers lifting off from one another in certain areas. On the other hand, such an amount of moisture can hardly be applied to a product web with effort that is justifiable in practice other than by impregnation or wetting of the product web with subsequent squeezing. Spraying is difficult to do evenly. The same applies to pouring, since the amount of liquid is too small to form a uniform film.

The second treatment liquor (color liquor or salt liquor, depending on what has been applied beforehand) is now applied to the web loaded with the specified amount of moisture, in a special way. The material web should not be led through a larger fleet, in which there is a risk of concentration changes due to the amount of treatment agent carried out by the material web. For this reason, when the second treatment fleet is applied, the web should only be in contact with the smallest possible amount of liquor, which is very quickly absorbed and transported away by the web and which is accordingly constantly renewed or supplemented by introducing fresh treatment fleets. Fresh liquor is therefore always applied to the web on both sides, through which no longer lengths of the web have yet passed. In this way, changes in concentration in the amount of treatment liquor in contact with the material web and corresponding differences in treatment failure can be minimized.

It is also important that the second treatment liquor is not squeezed off after application. By squeezing, no total moisture content can be set evenly, which is significantly above 120%. If squeezed after the application of the second treatment fleet, it would at best be possible to add a few 10% of the second treatment fleet, which in many cases is too little for the interaction of the two treatment fleets and the failure of the treatment. For this reason, the web is stripped off after the second treatment liquor has been applied, so that the same amount of treatment liquid can be added in the order of magnitude as in the first application and total moisture contents can be achieved which are in the range of what the web can hold in terms of moisture at all without the moisture dripping from the web or runs down on it. Such loads of liquor, which have been pushed to the limits of the drip-free moisture content, are advantageous for many treatments, because this gives great water mobility on the web and the transport of the treatment agents between the two fleets and in particular the drawing up of the treatment agents from the entire fleet onto the fibers in the steaming step that generally follows the order.

A continuous process for dyeing a textile web, in which it is provided with a first treatment liquor, partially dehumidified and then passed through an intermediate application unit with another treatment liquor, is known per se from DE-AS 10 78 527. However, this is not about dyeing with salt and the problems that arise. The known design is also out of the question for reasons of the required order quantities. The gusset applicator comprises two rollers arranged at the same height, between which the web is passed from top to bottom, passing through the treatment liquor in the gusset between the rollers to a certain low height before it passes through the nip. Since the rollers have to seal the gusset downwards, they have to rest against each other with a certain line force, which inevitably means that the web is squeezed vigorously and higher order quantities are in principle not possible.

A preferred application example of the method according to the invention is the subject of claim 2.

Extensive tests have shown that the end processes when dyeing cotton fabric with direct or substantive dyes are reduced from the order of about 50 to 150 m of web length to the order of 3 to 5 m by the process according to the invention and the dye yield can be increased by up to 40%, so that the dye losses and also the environmental impact from heavy metals entering the waste water can be reduced accordingly.

Further possible application examples of the method according to the invention are given in claims 3 and 4.

In the case of reactive dyes in particular, the losses have so far been so high that continuous processes have hardly been carried out.

It is particularly advisable here to keep the temperature of the two applied treatment liquors essentially the same, because this ensures optimal interaction between them and the web.

Gusset application devices with which the application of the dyeing liquid from a small liquor stock and the subsequent stripping can be realized in a gap are known per se from FR-PS 13 81 081. However, the invention does not lie in the gusset application device as such, but in the combination of an impregnation device with squeezing with an impregnation device with very little liquor content, in which subsequently stripped, ie a relatively large amount of liquor is left evenly on the web. An application device with stripping is also apparent from DE-OS 20 36 520. Here, the web passes a container filled with treatment liquor, is deflected upward and passes through the gap between two horizontally opposite, rotatable, fixedly supported inflatable tubes, where the excess liquor is wiped off.

In the drawing, an embodiment of the invention is shown in the form of a device designated 100 as a whole for dyeing a flat fabric made of cotton with direct dyes. The material web 1 is first passed through a padder 10 which forms the first application device and which comprises a plunge pool 2 which, with a width of the material web 1 of 1.80 m, comprises 30 to 60 l of a salt liquor 3, through which the material web in the manner shown is passed through a deflection roller 4, in order then to be directed vertically upwards and to be squeezed into the nip 5 between the nip rollers 6 and 7 to a moisture content of 70 to 90% by weight of the dry fabric web 1.

The material web loaded with this moisture is then deflected vertically downwards on a deflection roller 8 and thus passes into the gusset application device 20 which forms the second application device are essentially flat and slightly inclined to the web, ie approach it in the running direction. At the ends, the walls 11, 12 are connected to one another outside the edges of the material web 1, so that an upright, funnel-like trough 9 is formed, which can be filled with a treatment liquid 13 up to a selectable low fill level.

At the lower end of the trough 9, oblong recesses 15, 16 extending across the width of the material web are formed, in which inflatable pressure hoses 17, 18 are arranged. The hoses 17, 18, when inflated, lie on both sides with a gentle pressure that is very even across the width of the web and seal the trough 9 at the bottom. Outside the edges of the web 1, the hoses 17, 18 lie directly against one another and also seal in these areas. The fabric web is slid through the gap 19 between the tubes 17, 18. The treatment liquor 13, which in the exemplary embodiment is a dyeing liquor with direct dyes, received in the trough 9 is stripped down to a total moisture content determined by the pressure in the tubes 17, 18. This total moisture content is in the range of about 100 to 200%, i.e. the same amount of treatment liquor as that which has already been applied in the foulard 10 is added again in the gusset application device 20.

The level in the trough 9 is kept very low. With a web width of 1.80 m and the corresponding width of the trough 9 there are, for example, 4 to 8 l of the treatment liquor 13 in the trough 9. This amount would only suffice for a few meters of web 1 and would be used up very quickly. For this reason, the treatment liquor 13 is constantly supplied fresh by a feed device 14 and is kept in the trough 9 at a constant, albeit low, level. A significant change in the concentration of the treatment liquor 13 by treatment agents carried along by the material web 1 cannot therefore occur. Except for very small processes of the order of magnitude from 3 to 5 m, the entire length of the web 1 is colored evenly.

The material web 1 treated in this way now immediately moves into a damper 30 and then into a washing device 40 provided with several compartments.

TEST EXAMPLES 1. Dyeing with direct dyes

a) A flat fabric made of cotton with a weight per unit area of 200 g / m 2 was provided in accordance with the prior art in a foulard without the addition of salt with the following dyeing liquor and then steamed in the steamer for 2 minutes: 3.0 ml / l Wetting agent 2.0 ml / l Blocking aids 1.0 g / l Oxidizing agent 0.5 ml / l ventilator 7.7 g / l Direct blue I 2.3 g / l Direct blue II The fleet order was 85%, the working speed 30 m / min, the web width 1.8 m.
The result was a blue-colored web with end drains of the order of 100 m, which had to be used for other purposes.
b) An identical web was now dyed with the addition of salt on the device according to the invention in the same shade of blue.
First, an order was placed in the foulard 10 following salt liquor: 3.0 ml / l Wetting agent 3.0 ml / l Blocking aids 1.0 g / l Oxidizing agent 0.5 ml / l ventilator 30.0 g / l Table salt which was squeezed to a moisture content of 85%.
The material web 1 was then immediately fed into the gusset dyeing device 20 and provided there with a dyeing liquor which was composed as follows: 2.0 ml / l Wetting agent 4.2 g / l Direct blue I 1.2 g / l Direct blue II. The hoses 17, 18 were inflated with a pressure P = 0.5 bar, which resulted in an additional liquor application of 100%, so that the total moisture content of the web 1 after the gusset dyeing device was 185%. The web 1 loaded with it was steamed for 2 minutes and then washed in the washing device 40 in six compartments cold with overflow. The result was the same shade of blue as in case a), but the flow was only 5 m and, instead of as in case a), with 7.7 plus 2.3 = 10 g / l of dye with 4.2 plus 1.2 = 5.4 g / l dye could be worked. The addition of salt promoted the absorption of the dye in such a way that a much larger proportion of the dye actually applied to the fibers or, conversely, to achieve the same shade depth, a 37% lower use of dye could be used. The dye losses and the pollutants, in particular heavy metal ions, which are introduced into the wastewater by the otherwise washed-out losses are correspondingly reduced. So it will be both in this Area as well as by shortening the processes.

2. Staining with sulfur dyes

• 1. 50° C Überlauf
• 2. 70° C Überlauf
• 3. 95° C oxidieren 15 ml/l Textilhilfsmittel
• 4. 95° C oxidieren 1 g/l Soda
• 5. 50° C Überlauf
• 6. kalt Überlauf

Es ergab sich eine graue Färbung mit einem Ablauf von etwa 5 m. Aus der verbrauchten Menge an Schwefelschwarz von 25,4 g/l einerseits und 19,3 g/l andererseits ergibt sich bei gleichem Färbeergebnis eine Einsparung an Farbstoff von 13 %.
a) According to the prior art, a flat fabric made of cotton with a basis weight of 250 g / m² in a width of 1.8 m was provided at a speed of 45 m / min on a foulard with the following dyeing liquor: 3.0 ml / l Wetting agent 2.0 g / l Complexing agent 14.6 g / l Sulfur black 9.0 g / l Sulfur brown 1.8 g / l Sulfur red 20.0 g / l glucose 35.0 ml / l NaOH 29% 3.0 ml / l Sodium borate 3.0 ml / l Wetting agent 0.5 ml / l ventilator and squeezed to a moisture content of 85%. After steaming and washing there was a gray color with an end run of 100 m.
b) An identical material web 1 was provided in the foulard 10 with the following salt liquor: 3.0 ml / l Wetting agent 30.0 g / l Table salt 0.5 ml / l ventilator and squeezed to a moisture content of 85%. The web 1 was then placed in a gusset applicator 20 initiated and there provided with the following dyeing liquor: 2.0 g / l Complexing agent 11.1 g / l Sulfur black 6.8 g / l Sulfur brown 1.4 g / l Sulfur red 20.0 g / l glucose 35.0 ml / l NaOH 29% 3.0 ml / l Sodium borate 3.0 ml / l Wetting agent 0.4 ml / l ventilator The fleet order was 100%, so that there was again a total moisture content of the web 1 of 185%, with which the web 1 entered the damper 30. It was then washed in washer 40 in six compartments as follows:

• 1. 50 ° C overflow
• 2. 70 ° C overflow
• 3. 95 ° C oxidize 15 ml / l textile auxiliaries
• 4. 95 ° C oxidize 1 g / l soda
• 5. 50 ° C overflow
• 6. cold overflow

The result was a gray color with a run of about 5 m. The amount of sulfur black consumed of 25.4 g / l on the one hand and 19.3 g / l on the other hand results in a dye saving of 13% with the same dyeing result.

Claims (5)

1. A method of continuous dyeing of a textile web, in which a dye liquor and salt are applied to a web of material and the web is then partly dehumidified to a predetermined value, characterised in that the salt is applied in a treatment liquor separate from the dye liquor, the web is squeezed to a moisture content of 60 to 120% after application of the first treatment liquor (dye liquor or salt liquor), the second treatment liquor is applied while the web is still wet and in such a manner that the web is always in contact with only a small supply of liquor, which is continuously used and re-supplied to make up the amount used up, and immediately afterwards the web is partly dehumidified by being conveyed through a gap comprising at least one boundary resiliently abutting the web, and is wiped until the total moisture content is 100 to 200%.
2. A method according to claim 1, characterised in that a salt liquor and a dye liquor comprising direct dyes are applied, one of the liquors is first applied and squeezed out to a moisture content of 70 to 90%, after which the second liquor is applied, and the web is then wiped until the total moisture content is 130 to 160%.
3. A method according to claim 1, characterised in that a salt liquor and a dye liquor containing sulphide dyes are applied, one liquor is first applied and squeezed out to a moisture content of 70 to 90%, after which the second liquor is applied and the web is then wiped until the total moisture content is 160 to 200%.
4. A method according to claim 1, characterised in that an alkali liquor, optionally comprising salt, and a dye liquor comprising reactive dyes are applied, one liquor is first applied and squeezed out to a moisture content of 70 to 100%, after which the second liquor is applied and the web is then wiped until the total moisture content is 160 to 200%.
5. A method according to any of claims 1 to 4, characterised in that the two treatment liquors are applied at the same temperature.

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