Bleaching and dyeing; fluid treatment and chemical modification – Fluid treatment – Special forms and forming
Reexamination Certificate
1999-05-25
2001-03-06
Coe, Philip R. (Department: 1746)
Bleaching and dyeing; fluid treatment and chemical modification
Fluid treatment
Special forms and forming
C068S012070, C068S02200R
Reexamination Certificate
active
06195824
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to processes and apparatus for treating a textile web with a treatment liquid containing a treatment medium, such as a dye bath, in which the textile web is continuously guided through a trough containing the treatment liquid, and subsequently passed through a pair of squeezing rollers.
One such process and corresponding apparatus are known from the reference “Melliand Textilberichte” 1/1989, pages 46 to 52, particularly page 52, FIG. 23. The trough and the pair of squeezing rollers together form a conventional foulard. In the known embodiment, a system for “concentration regulation,” shown schematically, can be seen in the trough of the foulard, which is supposed to be able to take place “locally (edge/center) and/or laterally (run-off/tailing).” However, there is no information in the reference to indicate what is to be done with the concentration values that are determined. The pair of squeezing rollers of the foulard is entirely neutral, i.e. it is shown without any reference to a control mechanism.
The present invention begins from consideration of problems in the continuous dyeing of textile webs on a foulard. In this connection, particularly in the case of substantive and reactive dyes, the effect occurs that water, as the solution and transport medium, is absorbed more slowly or more rapidly by the web as it passes through the trough of the foulard, relative to the dye components in the dye bath. If the web absorbs water more rapidly, the dye bath loses water and the concentration of dye becomes higher. This means that the depth of shade increases, i.e. that the beginning of the web is clearly dyed a lighter color than the end of the dye lot in question.
A typical example for this case is dyeing viscose with reactive dyes. Initially, viscose swells very much and entrains a lot of water from the dye bath.
However, the reverse case also occurs, that a certain textile web absorbs more dye from the dye bath. This means that the beginning of the dye lot is dyed with a greater depth of shade.
When dyeing with reactive dyes, another cause for a nonuniform dye result over the length of the web is the tendency of reactive dyes to hydrolyze. Hydrolyzed reactive dye is no longer available for the actual dyeing process, and can therefore lead to concentration changes of reactive reactive dyes.
Color changes over the length of the web are also referred to as “tailing.” As a rule, they proceed according to a positive or negative e function and end in a state of equilibrium; after this equilibrium is reached, no further changes take place. Changes over the length of the web can be influenced not only by the properties of the fiber material, but also by physical properties such as strong water absorption of the web and swelling processes.
Although the causes of tailing are essentially known today, the problem continues to exist in practice and the initial lengths of some dye lots still have to be sold as seconds or have to be rejected entirely. The solution approaches tried until now have not been very successful. These solution approaches were, for example, to use dyes with a low affinity and/or hydrolysis constant, to reduce the temperature in the dye trough, or also to minimize the bath content in the dye trough.
In many cases, all these solution approaches reach clear limits, particularly in the important case of dyeing viscose with reactive dyes, which was mentioned, where starting lengths on the order of several tens of meters show color deviations which result in spoilage. Since shorter and shorter lengths of dye lots are being demanded today (down to as little as a hundred meters), there clearly is an urgent need to address this problem. The several tens of meters of starting length which cannot be used represent too high a proportion of damaged goods.
SUMMARY OF THE INVENTION
The present invention is directed to the task of providing a process and apparatus for treating a textile web with a treatment liquid containing a treatment medium such that the problem of tailings is avoided, or at least reduced.
A central idea in this invention is to balance out the change in concentration of the dye bath which takes place in the foulard trough at the beginning of the pass of a dye lot, by controlling the application amount of the dye bath. If the concentration in the foulard basin increases, the squeezing rollers are set to impinge more strongly upon the web, thereby reducing the amount of treatment liquid which remains on the textile web. This counteracts an overly great depth of shade. Vice versa, if the concentration of treatment medium in the foulard trough drops, the application amount is increased by a corresponding adjustment of the pair of squeezing rollers, in order to keep the depth of shade at the desired value.
The invention works in two steps. First, a test textile web length is allowed to pass through at a line force of the pair of squeezing rollers that is kept constant, in order to determine the concentration progression in the trough over the length of the textile web. The relationship between a concentration change and the line force change required to balance it out is determined in advance, either by calculations or by experiments, and is stored in memory in the regulation device. If the concentration of treatment medium in the trough drops after the first segment of the textile web has passed through, the line force is reduced by a certain amount, so that more treatment liquid and therefore also more treatment medium remains on the textile web, in order to balance out the concentration drop in the treatment liquid. The same holds true analogously if the concentration of the bath in the trough initially increases. This concentration progression and the resulting reference progression in the line force over the textile web length which is required to balance it out, in order to apply a uniform amount of treatment medium to the textile web, are stored in memory. When the subsequent production textile web length(s) now pass(es) through, the line force progression over the length of the textile web is regulated to the reference progression stored in memory. The determination of the concentration progression only has to be made once for a specific fabric, a specific treatment liquid, and specific other treatment parameters such as temperature and working speed. All other lots can be treated using the results stored in memory.
The result, in other words the reference progression, can remain stored in memory in the device, if the test run and the subsequent production runs all take place on the same device.
An arrangement for amount-controlled application of sizing to a textile web is known from U.S. Pat. No. 3,207,125 (the contents of which are incorporated herein by reference), which also works with a foulard-type application device, and contains a trough for saturating the textile web with the sizing and a pair of squeezing rollers provided directly afterwards, to adjust the amount of liquid applied. The electrical resistance at the textile web is continuously measured on a length segment between the pair of squeezing rollers and a measurement roll. The electrical resistance in the web depends on the specific conductivity of the bath and the amount of bath applied. If the influence of a changing conductivity can be eliminated, the measured resistance value is a measure for the amount applied, and therefore of the amount of sizing applied per surface unit. In order to eliminate the influence of changes in the conductivity of the bath, the conductivity is measured in the trough, on a random sample basis, and if deviations occur, the resistance signal between the pair of squeezing rollers and the measurement roll is adjusted. The conductivity measurements in the trough therefore serve only to check the bath properties, not to control the line force of the pair of squeezing rollers. This control takes place rather via the resistance of the length segment of the web in the measurement section, where a change means a
Coe Philip R.
Eduard Kusters Maschinenfabrik GmbH & Co. KG
Kenyon & Kenyon
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