A METHOD AND APPARATUS FOR THE HEAT TREATMENT OF TEXTILES

Abstract: In order to avoid considerable recondensation and energy losses when heat-treating textiles in a heated, evacuated steamer (6), the liquid (9) is removed (12) from the steamer (6) and pumped (14) into a container (19) for subsequent reuse after the material has been treated with saturated steam.

Description: A method and apparatus for the heat treatment of textiles The present invention relates to a method of heat-treating textiles, in particular spun cops or bobbins, in a heated steamer connected to a water and/or chemical supply and a vacuum pump via valves, and also relates to apparatus for carrying out this method. "Textiles" means any structure made of raw textile materials and includes materials in both fibrous and sheet form. It is known that heat treatment has a favourable effect on yarns, etc. for further processing. Textiles can also be conditioned or finished by treatment in a steam phase, if necessary with the addition of chemicals . Suitable steamers have been known for many years and substantially comprise a cylindrical boiler closable by a pivotable cover. Inside the steamer is a water bath which generates steam by means of a heating device and effects the appropriate heat treatment of the material introduced. To enable the steam to penetrate better the interior of the textiles, a vacuum is generated before the heating device for the water bath is switched on. These known steamers have the disadvantage that large amounts of energy are needed to form and maintain the va- cuum and, furthermore, the steam is removed by the vacuum pump and has to be recondensed. This results in only limited steam penetration of the material to be treated and/or long treatment times . An object of the invention is to provide a method and apparatus which use less energy, permit better penetration of the material to be treated and, in addition, reduce the cycle times and the overall heat treatment. The invention provides a method of heat-treating textiles in a heated steamer connected to a water and/or chemical supply and a vacuum pump via valves, wherein: in a first step, the steamer is charged with the material to be treated, - in a second step, the vacuum pump is then switched on until a vacuum of at least 100 mbar has been generated in the steamer, in a third step, a feed valve of the water and/or chemical supply is opened and a predetermined volume of liquid is admitted into the steamer to form a liquid bath, in a fourth step, the liquid bath and the steam phase to be formed are heated to a predetermined temperature, after the material to be treated has been held for a preselected time in the saturated steam phase, the liquid is pumped out of the steamer into a container, in a fifth step, the vacuum pump is re-activated, in a sixth step, after a preselected evacuation, cooling and drying time, the vacuum pump is switched off and ambient air is admitted into the steamer, and in a final step, the material is removed from the steamer. Preferably, in the second step a vacuum of at least 50 mbar is generated. For a liquid bath with a volume of 300 litres, the method according to the invention produces an energy saving in the order of 12 k h per cycle or 35 to 40 k h per treatment. Furthermore, the water vapour pumped off during the formation of the vacuum does not have to be recondensed. The non-recondensed volume saved is approximately 20 litres per treatment cycle. This provides the further advantage that the amount of fresh water needed is also reduced by an order of magnitude on account of the recirculation of the liquid in accordance with the invention. A further advantage consists in the simple and economic supply of chemicals and/or finishing additives which load the vacuum pump only slightly or not at all. The heat treatment or the results achieved may be improved in a simple manner by repeating the second to sixth steps at least once. The heat treatment can be optimised by successively increasing the temperatures of the steam phase from the first to at least one subsequent heat treatment. Preferably, during the heat treatment, a steam phase temperature of at least 350 'K is established in a first cycle and at least 380 °K in a further cycle. By increasing the holding time at a constant temperature during subsequent heat treatments the results may be improved without an increase in energy consumption. Energy may additionally be saved by aeration and the overall treatment time further reduced as a result, ie before the end of the first heat treatment, in an intermediate step, the vacuum is interrupted and then built up again. Preferably, the water and/or chemicals are supplied from containers dimensioned in accordance with the volume of the liquid bath in the steamer and which, together with the steamer, form a closed system into which only lost liquid is fed back from outside, the lost liquid due to the residual moisture in the steamed material and the evacuation. This permits recirculation of the liquids and/or chemicals and is therefore particularly economical and environ- mentally friendly. The invention further provides apparatus for carrying out the above method and comprising a heated steamer connected to a water and/or chemical supply and a vacuum pump via valves, wherein at least one container, a pump and at least two valves are provided for the liquid and/or chemical supply, the valves controlling the admission of liquid into and discharge of liquid from the steamer. Preferably an electric heating device is provided at least within the space of a liquid bath within the steamer. Such an electric heating device is particularly advantageous because it can be controlled very flexibly and thereby has a favourable effect. Other heating systems, for example steam heating systems, may also be used economically depending on the energy available. Preferably, the vacuum pump is a water-ring pump or a rotary vane pump. A water-ring pump is very cost-effective and suitable for vacuums up to 30 mbar. For vacuums up to 5 mbar, a rotary vane pump is necessary. An embodiment of the invention will now be described, by way of example only, with reference to accompanying drawings, wherein: Fig.l is a simplified, schematic representation of steam apparatus for treating cops in accordance with the invention, Fig.2 is a characteristic temperature graph for the steam phase in the steamer of the installation according to Fig. 1, and Fig.3 is the pressure graph associated with Fig. 2, in relation to the ambient atmosphere. In accordance with Fig. 1, an exhaust line is designated by the reference numeral 1. A vacuum pump 2 with an electric motor M is connected to the exhaust line 1. A vacuum line 3 is connected to the input side of the vacuum pump 2 (a ro- tary vane pump) and communicates with the interior of a steamer 6 via a valve VI and a suction line 4. A further valve V2 is also arranged in the suction line 4 and is connected to an air line 5. A liquid bath 8, the aqueous liquid 9 of which can reach a level Nl , and an electric heating device 10 are arranged inside the steamer 6 known per se. At one end, the steamer 6 is provided with a pivotable cover 7 having a vertical pivoting axis 7a. The material G to be treated is introduced into the steamer 6, where it is steam-treated, by opening the cover 7. Feed lines 11 lead from the electric heating device 10 to a control unit, the regulating function of which is represented by +/- . A liquid line 12 leads from the steamer 6 and is connected to pump lines 13 and supply lines 22. The pump line 13 leads to valves V7 , V8 , and V9 via a valve V3 , a liquid pump 14 with an electric motor M and pressure lines 15. The valves V7 - V9 are for their part connected to the lower parts of liquid containers 19 - 21 via in- let/outlet lines 16 - 18. Each of these liquid containers (tanks) has an aeration line 19' - 21', respectively. Valves V4 - V6 are also arranged on the inlet/outlet lines 16 - 18 and are connected to the supply lines 22. The operation of the arrangement according to Fig. 1 is relatively simple: the interior of the steamer 6 is evacuated to the desired low pressure via the vacuum lines 3 and 1 by closing the valve V2 , opening the valve VI, and switching on the vacuum pump 2. As a result, the material G to be treated also becomes substantially free of entrapped air. The valve V4 on the water tank 19 is now opened; the valve V9 remains closed so that water is sucked via the supply line 22 and the liquid line 12 into the steamer, where it fills the liquid bath 8 to the level Nl . The valve V4 is then closed and the electric heating device 10 is simultaneously activated by switching on the mains voltage, with the result that a steam phase forms inside the steamer 6 and penetrates the material G as saturated steam. After a predetermined holding time, the control unit swit- ches the heating device 10 off, the valves V3 and V9 are opened, the valve V4 remains closed and the liquid pump 14 is switched on; the water is pumped back into the water tank 19 and returns to approximately the level N2. The resultant displaced air can escape via the aeration line 19 ' . Similarly, the acids or bases are fed from the chemical tank 20 into the steamer 6 and then pumped back again. A further advantage of this arrangement is the connection to the liquid-wax tank 21 after the last steaming process in order to facilitate processing of the material G, namely spun yarn in the form of cops. Figs. 2 and 3 show the characteristics of a heat treatment for cops carried out in practice, starting from an ambient pressure of 1000 mbar. For graphical reasons, low pressures have been shown in abbreviated form in Fig. 3. As shown in Fig. 3, the steamer 6 is evacuated to a pressure of 5 mbar, after which water from the water tank 19 is admitted and heated, producing a steam phase having a temperature of approximately 350 °K held constant for 2.0 minutes; cf. Fig. 2. During this process, the pressure in the steamer 6 is raised to approximately 420 mbar. The vacuum is then interrupted and a residual quantity of steam is released via the suction line 4 and the valve V2 into the air (aeration); cf. Fig. 1. As shown in Fig. 3, a vacuum of 5 mbar is subsequently re- generated and a second treatment cycle begins. In this case, the temperature of the steam phase is increased to 380 °K, the pressure being raised to a positive pressure of 1300 mbar during the heating of the liquid supplied from the chemical tank 20. The same thing happens in the third cycle, in which an aqueous wax solution from the liquid-wax tank 21 is used to form the liquid bath 8. Increasing the heating times and the holding times in the subsequent cycles in relation to the first cycle has proved highly advantageous with respect to optimising the heat treatment . The first cycle l.C begins after the first evacuation process l.V and lasts 3.0 minutes; the second and third cycles 2.C and 3.C each have a durationd of 4.0 minutes. The whole heat treatment is finished after the fourth evacuation process 4.V, during which the residual moisture is removed from the material. The material in question is a spun cotton yarn; the cops have a net weight of 120 g. As can be seen from Figs. 2 and 3, the complete heat treatment, including the application of wax to the yarn, lasts a total of only 18,5 minutes, despite the very large cops. Depending on the material to be treated and the processing required, for economic reasons it can be advantageous if a steam condenser is additionally connected upstream of the vacuum pump 2. The process may also be carried out under vacuum with a pressure above 50 mbar. However, the process time is increased and the quality of treatment is reduced, especially when the material is heavy and/or compressed.

Claims: C l a i m s 1. A method of heat-treating textiles in a heated steamer connected to a water and/or chemical supply and a va- cuum pump via valves, wherein: - in a first step, the steamer is charged with the material to be treated, - in a second step, the vacuum pump is then switched on until a vacuum of at least 100 mbar absolute pressure has been generated in the steamer, - in a third step, a feed valve of the water and/or chemical supply is opened and predetermined volume of liquid is admitted into the steamer to form a liquid bath, - in a fourth step, the liquid bath and the steam phase to be formed are heated to a predetermined temperature, - after the material to be treated has been held for a preselected time in the saturated steam phase, the liquid is pumped out of the steamer into a container, - in a fifth step, the vacuum pump is re-activated, - in a sixth step, after a preselected evacuation, cooling and drying time, the vacuum pump is switched off and ambient air is admitted into the steamer, and - in a final step, the material is removed from the steamer . 2. A method according to claim 1, wherein the vacuum ge- nerated in the second step is at least 50 mbar. 3. A method according to claim 1 or 2 , wherein the second to sixth steps are repeated at least once. 4. A method according to claim 2 or 3 , wherein the temperatures of steam phase are increased from the first to at least one subsequent heat treatment. 5. A method according to claim 4, wherein, during the heat treatment, a steam phase temperature of at least 350 °K is established in a first cycle and at least 380 ' in a further cycle. 6. A method according to claim 4 or 5 , wherein the period of constant temperature during the first heat treat- ment is shorter than during subsequent heat treatments . 7. A method according to any one of claims 4 to 6 , wherein, before the end of the first heat treatment, in an intermediate step, the vacuum is interrupted and then built up again. 8. A method according to any one of the preceding claims, wherein the water and/or chemicals are supplied from containers dimensioned in accordance with the volume of the liquid bath in the steamer and which, together with the steamer, form a closed system into which only lost liquid is fed back from outside, the lost liquid being due to the residual moisture in the steamed material and the evacuation. 9. Apparatus for carrying out the method according to any one of the preceding claims comprising a heated steamer connected to a water and/or chemical supply and a vacuum pump via valves, wherein at least one container, a pump and at least two valves are provided for the liquid and/or chemical supply, the valves con- trolling the admission of liquid into and discharge of liquid from the steamer. 10. Apparatus according to claim 9, wherein an electric heating device is provided at least within the space of a liquid bath within the steamer. 11. Apparatus according to claim 9 or 10, wherein the va- cuum pump is a water-ring pump or a rotary vane pump.

Inventors: WANGER FREDDY, WANGER, FREDDY
Applicants: WANGER FREDDY, XORELLA AG, WANGER, FREDDY
Application year: 1997
Main classification: D06B5
IPC codes: D06B5, D06B17