FR2626297A1 - DYE REGULATION METHOD AND DEVICE - Google Patents

Abstract

The regulation of the dye bath is obtained by monitoring the exhaustion of the dye bath by photocolorimetry, by varying, in two successive steps, first a first parameter then a second parameter different from the first, so that the exhaustion of the dye bath as a function of time substantially follows a predetermined curve. For the dyeing of cellulosic materials with reactive dyes, the electrolyte content will be increased in the first step and then in the second step the alkaline agent content. For the dyeing of wool and polyamide, in soluble dyes from a used recycling bath at approximately 70 degree (s) C, the pH of neutrality will be brought to approximately 5 then the temperature will be raised to 100 degree (s) C if necessary.

Description

DYE REGULATION METHOD AND DEVICE

  The present invention relates to the regulation of a discontinuous dyeing operation of a material, in particular of a textile material, during which the dye or dyes present in the dye bath migrate on the material and attach themselves thereto. sustainable. It relates to the regulation according to which the transfer of the dyes, that is to say the depletion of the lorant bath, is followed by photocolorimetry at determined intervals of time and action is taken to ensure

  that the exhaustion in question follows a curve fixed in advance.

  Regulation of this type is known and practiced, in which the temperature of the bath is affected. The aim is to obtain a regular transfer of the dyes contained in

  the bath, essential for a homogeneous dye of good quality.

  Thus, a bath exhaustion rate is determined in advance during the entire duration of the dyeing operation, or possibly different rates of bath exhaustion during certain portions of the dyeing operation. And we vary the temperature of the bath, according to the values obtained, periodically, as to the actual exhaustion of the bath in dyes, so that the real curve of the exhaustion is the nearest

  possible of the pre-established curve.

  This known method of regulation is implemented in a device sold under the trademark TEINTOPROG. This device comprises three elements, namely the measuring chamber in which the bath circulates continuously, the optical block consisting of a white light source associated with a set of four filters, photodiodes and converters and a processing system which analyzes the signals from the optical block, processes them and controls the regulation by acting on the automation of the

heating.

  However, the known method is only operational for a limited number of dyeing types, using soluble dyes, that is to say cationic or anionic dyes for wool, polyamide or acrylic. Its use is in

  particular not conceivable in the case of reactive dyes.

  Now it is found and this is the subject of the invention a method of controlling a discontinuous dyeing operation, of the type known as above, which provides a significant diversification to possible applications. The method is of the known type according to which the exhaustion of the bath by dyes is carried out by photocolorimetry at determined time intervals. In an original way, two successive stages are varied, first a first and then a second parameter different from the first, so that the exhaustion of the dye bath according to

  time follows substantially a predetermined curve.

  Thus one no longer acts solely and throughout the duration of the dyeing on the sole temperature of the bath, but acts in a first step on a first parameter and in a second step on a second parameter, different from the first, one

  either of these parameters may be the temperature of the bath.

  It has indeed been noted that it was possible in a large number of applications, other than dyeing in soluble dyes for wool, acrylics or polyamides, to regulate the exhaustion of the bath throughout the dyeing operation. by successively varying two different parameters, said parameters being selected according to

the chosen application.

  In a first version of the invention, a dyeing bath of cellulosic materials containing at least one reactive dye is regulated, increasing in a first step the content of the bath in electrolytes and increasing in a second stage.

  the bath content of alkaline agents.

  As regards cotton, the electrolyte added to the bath during the first stage consists, for example, of sodium sulphate, the alkaline agent added to the bath during the second stage consists, for example, of sodium hydroxide solution and The transition from the first step to the second occurs, for example, when an additional supply of electrolyte no longer varies the depletion. In a second version of the invention, a dyeing bath of materials such as wool, polyamide, containing at least one soluble dye, is regulated, said bath resulting from a dyeing operation completed in the same batch and having a dyeing temperature. approximately 70% C and a pH close to neutrality. In this second version, in a first step, the pH is adjusted to the known pH, which is appropriate for the material and the class of dyes used, for example 5, by the progressive addition of an acidic agent, and then is varied in a

  second step the bath temperature up to about 100% C.

  Thus, thanks to the process of the invention when the same lot is fractionated, it is possible to recycle the used and hot dyeing baths, while being assured of having

  all the successive passes a homogeneous dye of quality.

  This possibility of recycling represents an important saving of energy, because until now the baths used were rejected or at best sent in heat exchangers, to recover a part of the available energy. This last solution was also not always suitable, because this recovery carries risks of fouling of the heat exchanger and therefore of reducing its performance. On the other hand, thanks to the invention, it is now possible to envisage recycling the

  dye baths, after use, up to five times in succession.

  It is another object of the invention to provide a device specially designed for the implementation of the aforementioned method. The device comprises: a. a photocolorimetric sensor comprising a measuring chamber in which the dyebath circulates, an optical block consisting of at least one white light source placed on one side of the chamber and processing means capable of measuring at intervals of time determined, from the luminous flux transmitted by the bath, the concentration of the bath in each of the dyes, b. means for comparing, for each dye, the rate of exhaustion observed between two successive measurements with respect to a preselected speed, c. first means of action, acting during the first phase of the dyeing cycle, and controlled by the comparison means so that the observed depletion rate is close to the preselected exhaustion rate (s) for this first phase, d. and second means of action, acting during the second phase of the dyeing cycle, and controlled by the comparison means so that the depletion rate observed is close to the exhaustion rate (s).

  preselected, for this second phase.

  The first and / or second means of action may consist of containers provided with a supply valve whose opening and closing are controlled by the comparison means, said containers containing given dyeing auxiliary agents. For example, the container corresponding to the first means of action contains an electrolyte and the container corresponding to the second means of action contains an alkaline solution. For example, the container corresponding to the first means of action contains an acidic solution. The first or second means of action may consist in the heating means of the dyeing bath provided with a

  switch actuated by the comparison means.

  The invention will be better understood on reading the

  description that will now be made of two examples of

  embodiment, illustrated by the accompanying drawing in which the single figure is a schematic sectional view of a control device, based on two parameters, equipping an autoclave with

dyeing.

  The material to be dyed, not shown, is placed in the dyeing autoclave 1, on which a line 2 is connected bypassing. The dyeing bath 3, circulating in the autoclave 1 during the dyeing operation, also circulates Continuously inside the pipe 2. The pipe 2 'in the measuring chamber 4, which is connected by a double set 5 and 6 of optical fibers to an optical block 7. The optical unit 7 comprises two parts 8 and 9. In the first part 8, a source 10 of white light and its associated optics 11 illuminate the input 12 of the first set of optical fibers. In the second part 9, the output 13 of the second set 6 of optical fibers is directed towards four filters, associated with photodiodes and with

26.6297

  converters, transforming the light flux transmitted through the filters into electrical signals. The four filters are chosen so that their transmission spectra have peak peaks that together cover the range of wavelengths between 400 and 700 nanometers. In the measuring chamber 4, the pipe 2 comprises the outlet 14 of the first set 5 of fibers and the input 15 of the second set 6 of optical fibers. Exit 14 and Entry 15 are

  positioned opposite each other in line 2.

  The converters are connected to a set 16 for processing the electrical signals, the operation of which will be explained later, which controls the implementation, on the one hand, of the solenoid valve 17 fitted to the container 18 and, on the other hand, of the automation of the heating 19 of the dye bath 3. The container 18, containing at least one dyeing agent opens

in the autoclave 1.

  The implementation of the method of the invention and the operation of the aforementioned device will be described in a first example of bathing dye stuffing, using

a recycling bath.

  The spent bath, after a first wool dyeing operation, is substantially free of dyes and is at the end-of-cycle temperature of the order of 90 ° C. to 10 ° C. The amount of spent bath is less than that required. for a new pass, given the amount of bath that was carried by the material output from the autoclave in the previous operation. When it is completed with cold water, the temperature of the spent bath is of the order of 75 C. Its pH is raised to 7.4 by possibly adding the necessary reagents. The photocolorimetric sensor performs a first measurement of the bath

  used then a second after the dyes have been added.

  The wool flock to be dyed is placed in the autoclave and the dyeing operation can begin. In the autoclave, the dye bath 3 passes through the material to be dyed and circulates in

driving 2.

  The light source 10 associated with its optics 11 sends on the input 12 of the first set 5 of optical fibers a luminous flux which is directed into the measurement chamber 4. In the chamber 4, this stream coming from the output 14 of the first set The incident light flux undergoes an absorption which is a function of the dye concentration of the bath 3, for a given wavelength of the light. The flow, after passing through the bath 3, is taken up by the second set 6 of optical fibers and is separated into four separate channels where it passes through each of the four filters. The purpose of passing over the filters is to show the specific luminous flux of each dye contained in the bath as a function of its wavelength. The photodiodes, the converters and the processing unit 16 convert the light intensities into normalized currents

(from 4 to 20 mA).

  Prior to the dyeing operation, one (or more) setpoint value corresponding to the desired rate (s) of exhaustion, for example 1.5% per minute, was introduced into the treatment unit. This value is the deviation of the measured concentrations between two measurements made by the sensor referred to the time interval between said two measurements. During a first step, the treatment unit 16 acts on the solenoid valve 17 controlling the introduction into the autoclave 1 of the acetic acid solution contained in the container 18. This introduction is controlled so that the speed of exhaustion actually observed is close to the

  (or the) set speed chosen for this first step.

  Thus the processing unit 16 will control the opening of the solenoid valve 17 at each measurement where a negative difference will be found between the measured value and the setpoint value (measured exhaustion rate less than the depletion value selected as the setpoint Inversely, in the event of a positive deviation exceeding a given maximum, all

  treatment 16 will not command the opening of the solenoid valve 17.

  This first step, in the case of dyeing loose wool with soluble dyes, lasts until the dye bath 3 has reached the predetermined pH threshold, depending on the material and the class of dye. for example 5. This predetermined pH is that recommended by suppliers of

  dyestuffs and known to all dyers.

  In the second step, the processing unit 16 acts on the heating system 19 for heating the dye bath 3, increasing or stopping the heating so that the rate of exhaustion actually c -stated is close to the (or the )

  setpoint speed (s) chosen for this second step.

  This second step lasts until the temperature reaches 100 C or when the dye bath 3 is 90% depleted

for example.

  Then the temperature is maintained during the

end of dyeing.

  In another example of cotton dyeing using reactive dyes, the treatment unit 16 is connected not to the heating automation 19 but to a second solenoid valve / container assembly similar to the solenoid valve 17 and the container 18. In this case the first container 17 contains an electrolyte, namely sodium sulphate and the second container a

  alkaline solution namely washing soda.

  The operation of the device is identical to that described in the first example. The dyebath remains at a constant temperature, for example about 40 ° C., if the reactive dyes used are "cold" reagents, 80 ° C., if the reactive dyes used are "hot" reagents. In the first step, the electrolyte is added so that the measured rate of exhaustion is close to the set speed chosen for this first step, which lasts until an additional supply of electrolyte is no longer sufficient. vary the exhaustion. This transition from the first to the second step is controlled when, for example during four or five successive measurements, the colorimetric sensor no longer observes an evolution of the exhaustion of the dye bath. It is also possible to set, for a given dye, a predetermined quantity of electrolyte and to go from the first to the second step when this predetermined quantity has been added to the bath. To choose the predetermined quantity we will use the tables provided by suppliers of dyestuffs and made available to all dyers, who indicate the

  desirable concentration of dye bath electrolyte.

  In the second step, the alkaline solution is added so that the rate of exhaustion measured is close to the set speed chosen for this second step, which lasts until all of the alkaline agent is used, or ideally that an additional contribution does not make any more variation the exhaustion. In a specific case, a bath containing 0.5% / of a reactive dye CI (Color Index) Reactive yellow 27 was used for a cotton which had previously undergone the necessary preparation treatments, this percentage being calculated on the mass of material to dye. The bath, maintained at 40 ° C., circulates through the material for 5 to 10 minutes for good homogenization, then the sodium sulphate is added so that the dye exhaustion follows a slope of 1.5% / min. For the amount of dye and the bath ratio, the amount of sodium sulphate retained is 40 g / l. The end of the first step occurs when the amount of sodium sulfate, corresponding to 40 g / l, was added to the bath. The alkaline agent is a Bé soda liquor at a rate of 2 ml / l. the exhaustion curve for this second step is the same, namely 1.5% / min. The end of the second step occurs when the quantity of sodium hydroxide solution has been added or when no exhaustion is observed after 5 successive additions of sodium hydroxide solution. The complete fixation of the dye and the usual finishing treatments (rinsing, soaping) require additional time

about 30 minutes.

  The invention is not limited to the examples which have just been described. It is up to the person skilled in the art, in the context of the process of the invention, to choose the two parameters which will best enable the rate of exhaustion of the dyebath to be varied as regularly as possible, and this in

  function of the materials to be dyed and dyeing conditions.

Claims (9)

  1. A method for regulating a dyeing bath of the type in which the exhaustion of the dye bath is followed by photocolorimetry, characterized in that a first and then a second parameter are varied in two successive stages. different from the first, so that the exhaustion of the dye bath as a function of time substantially follows a predetermined curve.   2. Method according to claim 1 characterized in that, in the case of a dyeing bath of a cellulosic material containing at least one reactive dye, in the first step the content of the electrolyte bath is increased and in the second   step is increased the content of the bath alkaline agents.   3. Method according to claim 2 characterized in that the electrolyte and the alkaline agent added to the bath are respectively sodium sulphate and sodium hydroxide, and in that the transition from the first to the second step occurs when an additional supply of sodium sulphate no longer vary the exhaustion of the bath.   4. Method according to claim 1 characterized in that, being a dye bath containing at least one soluble dye, having a temperature of about 70 C and a pH close to neutrality, in the first step is made vary the pH to the appropriate pH for the dye class and in the second step   varies the temperature of the bath to about 100 C.   5. Method according to claim 4 characterized in that the pH variation is obtained by adding acid, especially acetic, and in that the transition from the first step to the   second occurs when the pH is 5.   6. Application of the method according to one of claims 4 and 5 to   the regulation of hot recycling baths.   7. Device for implementing the method of claim 1 characterized in that it comprises: a. a photocolorimetric sensor comprising a measuring chamber (4) in which the dyebath (3) flows, an optical block consisting of at least one white light source (10) placed on one side of the chamber and means ( 9) of treatment capable of measuring, at given time intervals, from the luminous flux transmitted by the bath, the variation of concentration of the bath in each of the dyes, b. means for comparing (16), for each dye, the depletion rate observed between two successive measurements with respect to a preselected speed, c. first means of action (17,18), acting during the first phase of the dyeing cycle, and controlled by the comparison means (16) so that the depletion rate observed is close to the speed or speeds ( s) preselected exhaustion for this first phase, d. and second means of action (19), acting during the second phase of the dyeing cycle, and controlled by the comparing means (16) so that the observed depletion rate is close to the speed (s) (s) ) of exhaustion   preselected, for this second phase.   8. Device according to claim 7 characterized in that the first and / or second means of action consist of containers (18) provided with valve (17) supply whose opening and closing are controlled by the means of comparison (16), said containers containing agents dyeing auxiliaries.   9. Device according to claim 7 characterized in that the first or second means of action consist in the means (19) for heating the dye bath equipped with a switch   operated by the comparison means.