Method and apparatus for dyeing cellulosic textile substrates with a leuco-state dye

Abstract

An apparatus for dyeing a cellulosic textile substrate with reduced indigo dye in a leuco-state in an inert atmosphere substantially isolated from oxidizing substances. A plurality of applicator faces that each apply a portion of the total dye application. The first foam applicator is spaced from the entrance of the chamber to allow air entrapped in the interstices of the substrate to escape. The applicators are spaced from each other to allow collapse of the foam and dispersion of the dye applied in the previous applicator before the substrate reaches the next applicator. Similarly, the exit is spaced from the last applicator to allow the foam to collapse and the dye to disperse prior to exiting the apparatus and entering the atmosphere in which oxidization of the dye occurs.

Description

This application is a continuation-in-part of pending U.S. patent application Ser. No. 10/833,450, filed Apr. 28, 2004.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for dyeing cellulosic textile substrates with an inert leuco-state dye. More particularly, the present invention relates to an apparatus for dyeing cellulosic textile substrates with a reduced leuco-state dye foamed with an inert gas and applied in the leuco foamed state in an inert atmosphere to the textile substrate and subsequently oxidized thereon to affix the indigo dye to the cellulosic textile substrate.

Dyeing cellulosic textile material, such as cotton yarn or fabric, with a leuco-state dye, such as indigo dye, has a large market, particularly for cotton denim clothing items, such as blue jeans. The fastness of the indigo dye on cotton and the deep color or shade that can be obtained make indigo dyed fabric a very popular product. However, dyeing cellulosic textile material with indigo dye is a complicated, complex and expensive procedure, because indigo in its natural state will not affix to cellulosic fibers. To render the indigo dye capable of affixing to cellulosic fibers, it is necessary to reduce the indigo by removing oxygen as by mixing with hydro (hydrogen sulfide) or other reducing agents to render the indigo a colorless leuco-state material. It then must be handled to remain in a substantially leuco-state until it is applied to the cellulosic textile material. To be capable of being applied, the leuco-state indigo dye must be sufficiently dilute to penetrate into the interstices of the cellulosic material. Typically, indigo dye is obtained from a supplier in a paste form that is, for example, in a 40% solution. It then must be further diluted to, for example, a 2% solution with a non-oxidizing liquid, such as hydro, to be capable of penetration into a traveling textile substrate that is immersed through a vat of the diluted indigo dye. Because of this dilution, it is necessary to pass the textile substrate through a series of sequential indigo dye vats with intermediate exposure to the atmosphere or other oxidizing agents to set the indigo applied during the preceding immersion. To obtain a desired deep color or shade, it is common to utilize a dyeing range having anywhere from four to eight, dye vats in series with arrangements of guide rolls between vats to assure proper oxidation of the indigo between vats. In addition, the dye in the vats must be continuously and rapidly recirculated in a tank or tanks into which reduced water or other similar material is added and regulated to remove oxygen taken up in the dye vats and to return any oxidized indigo dye to the reduced leuco-state.

A significant problem with prior art indigo dyeing ranges is that of waste dye and water disposal. Because of the numerous vats and the amount of dye liquor that must be provided, there is a significant quantity of dye liquor that must be disposed of at the end of every dyeing operation. This creates an undesirable substantial expense and environmental problem.

Another prior art dyeing system is disclosed in U.S. Pat. No. 4,613,335, issued Sep. 23, 1986, to Hans-Ulrich Berendt, et al. This patent discloses a process for dyeing or printing cellulosic-containing textile material with a reduced leuco-state dye in a foam carrier. While mentioning dyeing, the disclosure is primarily directed to printing, and there is no disclosure of the substrate being in a sealed, inert atmosphere. Rather, the substrate is exposed to the atmosphere as it approaches the applicator, as it passes across the applicator, and as it leaves the applicator. Therefore, there is no control of the condition of the substrate as it approaches and passes under the applicator and no control of the oxidation of the dye after it is applied to the substrate.

In contrast, the present invention provides for the applicator face and substrate to be in a controlled inert atmosphere so that the foam can be applied without oxidation or controlled oxidation of the leuco-state dye and the foam can at least partially collapse in the inert atmosphere allowing the dye in its leuco-state to disperse on the substrate without oxidation or with controlled limited oxidation before it is fully oxidized as the substrate leaves the inert atmosphere, assuring that desirable affixing of the dye on the substrate occurs when the substrate is exposed to the atmosphere.

SUMMARY OF THE INVENTION

Briefly described, the present invention provides an apparatus for dyeing cellulosic textile substrates with a foamed reduced leuco-state dye. The apparatus includes a housing having an interior chamber sealed from atmospheric air and through which the substrate travels from an entrance having a seal through which the substrate enters the chamber to an exit having a seal through which the substrate exits the chamber. A supply of inert gas communicates with the chamber to provide an inert environment therein. At least one foam applicator has an applicator face in said chamber and extending across the width of the substrate for applying foam containing the dye in leuco-state to the substrate in the chamber. A foam generator generates foam containing the leuco-state dye in the absence of oxygen with the generator communicating with the applicator for supplying the foamed leuco-state dye to the applicator. Thus, oxidation occurs primarily only after the substrate exits the chamber. However, there may be a minimal amount of oxygen in the otherwise inert gas and some small controlled amount of oxygen may purposely be included in the inert gas for desired controlled partial oxidization of the dye before it exits the chamber. Preferably, the supply of inert gas is under pressure to provide a pressurized inert environment in the chamber and minimize the entry of any atmospheric air through the entrance and exit. Also, preferably, the at least one applicator is spaced from the entrance to provide a free reach of the substrate in which air trapped in the interstices of the substrate is allowed to escape, and the at least one applicator is spaced from the exit to allow foam on the substrate to collapse and deposit and distribute the leuco-state dye on the substrate before the substrate exits the chamber and the dye is oxidized.

In a preferred embodiment there is a plurality of applicators with application faces in the chamber and disposed with spaces therebetween to allow foam to at least partially collapse and the leuco-state dye to at least partially deposit on the substrate before having foam applied by the following applicator. Hold-down elements, in the form of rollers, may be disposed between the applicators for engaging the substrate to displace the substrate between the applicators to maintain the substrate in foam receiving engagement with the applicator faces. The applicators are preferably parabolically shaped for uniform distribution of foam across the width of the substrate.

In the preferred embodiment, the inert gas is nitrogen and the foam generator generates a foam of nitrogen containing the leuco-state dye. One advantage of nitrogen being in the foam is that when the foam collapses in the chamber, the nitrogen increases the amount of inert nitrogen in the chamber environment.

The present invention has special application to dyeing woven denim fabric with indigo dye, which may be applied at a weight of approximately 10% to 15% of the weight of the fabric.

To allow access into the chamber, the housing may have an openable cover sealingly mounted thereon and the hold-down elements may be mounted on a frame that is moveable to move the hold-down elements away from the spaces between applicators when the cover is open.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a dyeing range in which the apparatus of the preferred embodiment of the present invention is incorporated;

FIG. 2 is a plane view of the dyeing range of FIG. 1;

FIG. 3 is an end elevation of the entrance end of the dyeing apparatus included in the dyeing range of FIGS. 1 and 2;

FIG. 4 is a plane view of the apparatus of FIG. 3 with a portion of the cover removed;

FIG. 5 is a side elevation of the apparatus of FIG. 3;

FIG. 6 is a side elevation of the apparatus of FIG. 3 with the side panel removed;

FIG. 7 is similar to FIG. 6 with the cover and roller frame open; and

FIG. 8 is a view similar to FIG. 6 and illustrating alternative exit seals and drains.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The dyeing apparatus 10 of the preferred embodiment of the present invention is illustrated in FIGS. 1 and 2 incorporated in a dyeing range 12. A sheet of textile substrate S is fed to the range 12 from a supply roll 14 or a supply of plaited material in a supply box 16. The substrate S is then relaxed in a J-box 18 from which it is withdrawn by a feed roll assembly 20 from which the substrate travels under a crosswalk grid 48 on which an observer O stands to monitor the dyeing operation in the dyeing apparatus 10. The substrate is drawn through the dyeing apparatus 10 by a driven pull roll assembly 22. The drive of the feed roll assembly 20 and pull roll assembly 22 are controlled so that a desired tension is being maintained in the substrate S as it travels through the apparatus 10. From the pull roll assembly 22 the substrate may be subjected to a supplemental treatment at a supplemental dye application station 24, at which a foam applicator 26 applies a surface treatment, such as the same or different dye as applied in the dyeing apparatus 10, or any other desired surface treatment material, which surface treatment can be applied to either surface of the substrate. The treated substrate then passes through an infrared dryer 28 to reduce the moisture content to a desired level. Any other type of dryer could be substituted. From the dryer 28, the substrate S passes under a crosswalk grid 50 over a series of guide rolls 30, and is wound on a driven takeup roll 32 to form a roll 34 of the dyed substrate S.

As illustrated schematically in FIG. 2, an inert gas is fed to the dyeing apparatus 10 from a source 36, which can be a supply tank containing the inert gas or a generator of the inert gas, such as a nitrogen generator. The gas is fed through a supply line 40 to the interior of the apparatus 10 to provide an inert environment.

The inert gas is also fed, from the source through a second supply line 38 to a foam generator 42, which also receives a reduced, leuco-state dye from a dye supply tank 44. The dye supply tank 44 is maintained under seal that prevents air from entering the supply tank 44 as dye is fed therefrom to the foam generator 42 so as to prevent oxidation of the leuco-state dye. The foam generator is of any conventional type that can create a foam using the nitrogen and having the dye dispersed therein, which foam is then fed through a feed line 46 into the dyeing apparatus 10.

The dyeing apparatus 10 is illustrated in detail in FIGS. 3-8. A front guide roll 52, under which the substrate travels, directs the substrate S from a horizontal direction to a vertical direction. The front guide roll 52 is mounted on the housing 54 of the dyeing apparatus 10.

As the substrate S travels vertically from the front guide roll 52, its edges E pass through a pair of opposed sensing forks 56, illustrated in FIGS. 3 and 4, that sense the location of the edges E. In response to sensing of the position of the edges E of the substrate S, servo motors 58 adjust end seals 60 to limit foam application to the lateral extent of the substrate without significant escape of foam from the applicators beyond the position of the lateral edges E of the substrate S.

The housing 54 is formed with opposite side panels 64 and corner support legs 66. The upper portion of the housing 54 is formed as a chamber 68 formed by front and rear walls 70, 71, the side panels 64 of the housing, a bottom wall 72, L-shaped walls 73 extending from the bottom wall 72 to entrance and exit seals 92 and 126, and a pivotable cover 74 that sealingly seats on the upper edges of the walls 70 and panels 64 with sealing material, such as resiliently compressible foam material, disposed therebetween, or the seal could be provided by a trough containing water formed at the top of the walls 70 and panels 64 with the bottom edges 76 of the cover seated within the water in the trough (not illustrated). The cover 74 is opened and closed by a pair of laterally spaced piston cylinder mechanisms 78 that have ends 80 attached centrally to the cover 74 and other ends 78 attach to upstanding support posts 84 that extend upwardly from the top of the housing 54. To accommodate this pivoting of the cover 74, it is mounted on a pivot shaft 86, on which are also mounted support bars 88 adjacent the piston cylinder mechanisms 78 and centrally of the cover 74. These support bars 88 stabilize the cover 74 during pivoting.

The cover 74 is formed with observation windows 90 through which the observer O can monitor the operation of the dyeing apparatus 10 as the substrate S travels there-through. At the front of the chamber 68 the entrance seal 92 is located through which the substrate S passes into the chamber 68. This entrance seal 92 is formed by two pairs of spaced inflatable bladders 93 that prevent the entry of air into the inert environment within the chamber 68. Above the entrance seal 92 an entrance guide roll 94 directs the substrate S to a plurality of longitudinally spaced foam applicators 96, 98, 100, 102 and 104. The guide roll 94 is located below the level of the face 106 of the first foam applicator 96 to ensure positive engagement of the substrate S with the applicator face 106.

The applicators 96, 98, 100, 102 and 104 are mounted on the bottom wall 72 by flanges 103 on the applicators secured on the bottom wall 72.

A hold-down roller mounting frame 108 is mounted above the foam applicators 96. This frame 108 has mounted on its underside four hold-down rollers 110, 112, 114 and 116. These hold-down rollers 110, 112, 114 and 116 are disposed between the foam applicators and project downwardly below the level of the faces of the applicators to force the substrate S to be deflected downwardly between applicators to assure positive engagement of the substrate S with the applicator faces 106.

The frame 108 carrying the hold-down rollers 110, 112, 114 and 116 is pivoted on a pivot shaft 178 spaced rearwardly and upwardly from the last foam applicator 104. The frame is retained in operating position by wingnuts 180 attachable to upstanding brackets 122 forwardly of the first foam applicator 96. A coil spring 121 secured to the rear wall 71 of the chamber 68 and a rearward extension 140 of the frame 108 biases the frame 108 to an open position so that when the wingnuts 120 are released, the frame 108 will pivot upwardly into an open position.

Beyond the last foam applicator 104, an exit guide roll 124 is mounted below the level of the foam applicators for guiding the substrate S away from the foam applicators and downwardly through the exit seal 126 having pairs of spaced inflated sealing bladders, with the exit seal 126 and bladders 128 being identical to the entrance seal 92 and bladders 93, to prevent entrance of atmospheric air into the chamber 68.

Spaced below the exit seal 126 is a guide roll 130 that guides the substrate vertically downward and then horizontally outward to the pull roll assembly 22.

The entrance seal 92 and the entrance guide roll 94 are spaced from the first foam applicator 96 to provide a free reach of the traveling substrate during which air that may have been entrapped in the interstices of the substrate S and thereby entered the chamber 68 will have an opportunity to escape from the substrate interstices, thereby substantially avoiding any undesirable oxidation of the reduced, leuco-state dye when it is applied to the substrate.

The foam applicators 96, 98, 100, 102 and 104 are spaced from each other so that, as the substrate travels from one to the next, it is deflected by the intermediate guide rolls 110, 112, 114 and 116 to provide a free time between applicators for the foam to collapse and the dye disperse before dye is applied by the next applicator. Similarly, the exit guide roll 124 and exit seal 126 are spaced from the last foam applicator 104 to allow collapse of the foam and dispersion of the dye before the substrate leaves the inert atmosphere within the chamber 68 and the dye exposed to oxygen in the atmosphere beyond the exit seal 126.

Each of the foam applicators 96, 98, 100, 102 and 104 are, in the preferred embodiment, parabolically shaped applicators of the type disclosed in U.S. Pat. No. 4,655,056, issued Apr. 7, 1987, to Dieter F. Zeiffer. This type of applicator is particularly useful in that the parabolic shape distributes foam equally and over equal distances from the input to the full extent of the applicator face. Other types of applicators can also be used with varying results.

The applicator in the supplemental dye applying station 24 may also be of the parabolic shape, particularly if it is applying a foam, but any other type of dye or other surface treatment may be applied as well in other types of applicators.

As seen in FIGS. 6 and 7, gutters 131 at each side of the chamber 68 outwardly of the applicators decline centrally toward drain pipes 132 that collect any excess dye or other liquid and have closures 134 that are openable at the end of a dye run to allow flushing of the chamber 68. The closures 134 also are open at the startup when nitrogen or other inert gas is fed from the inert gas source 36 under pressure into the chamber 68. As atmospheric air is heavier than nitrogen, the introduction of nitrogen under pressure will cause atmospheric air to exit the closure 134. When all or substantially all of the atmospheric air has exited the chamber 68, the closures 134 are sealed and the substrate S is threaded by a lead sheet or other means to begin operation. Alternatively, the substrate may be threaded before air is evacuated from the chamber 68, which will result in a short length of substrate being imperfectly dyed.

The purging of oxygen bearing air from the interstices of the fiber structure provided by the spacing of the entrance seal 92 and entrance guide roll 94 from the first applicator 96 prevents the dye liquor from oxidizing prematurely and rather allows subsurface liquor migration that would be restricted were the dye to oxidize, making it immobile resulting in a loss of control over distribution of the dye molecules.

However, as commercially supplied inert gas, such as nitrogen, contains some small amount of oxygen and as commercial inert gas generators do not produce totally pure inert gas, there may be a minimal amount of oxygen in the inert atmosphere, resulting in some unintentional slight oxidization of the dye on the substrate before the substrate leaves the chamber. An advantage of the present invention is that, if desired, some small controlled amount of oxygen may purposely be included, in any conventional manner, to provide partial oxidization of the dye on the substrate between and/or after dye application before the substrate leaves the chamber and the dye is substantially oxidized in the ambient atmosphere.

If acceptable, only one foam applicator can be incorporated in the apparatus with all of the foam being supplied through that one applicator, but preferably a plurality of foam applicators are used with each applicator applying a fraction, either equally distributed or selectively distributed, depending on preferences, and a much deeper shade can be obtained with the same amount of dye by applying multiple foam applications. With a plurality of foam applicators, with each applicator supplying a relatively small limited amount of dye-containing foam, the migration of the dye into the fiber surface can be a controlled process. Subsequent relatively small amounts of foam put onto the same fiber surface area, in a superimposed fashion, will allow for a dye enrichment to be achieved. Sequential dye applications are accomplished without any dye ever being allowed to oxidize until the final application is made. The substrate fibers are unable to satisfactorily absorb large foam volumes that are applied at one, rather than a plurality of, applicators.

With the spaces of the dye liquor delivery system filled with reduced dye, the liquor itself, which can be formulated at a low viscosity, incrementally applied to the fiber surface will provide a controlled specific infusion rate. The lowest viscosity of the foam can be maintained during the foam application, with the foam being in only a temporary delivery state. The foam collapses almost immediately upon fiber contact and does not hinder the dye infusion process. The super-imposition of incrementally small amounts of liquor with time intervals, or infusion stages, between each subsequent foam application takes place with the dye being in a non-oxidized state, in striking contrast to the prior art.

In the preferred embodiment, indigo dye in its reduced, leuco-state can be run at normal finishing range speeds, such as about sixty meters per minute. A typical fabric weight would be 400 grams per square meter, and a typical amount of indigo dye to be applied to one side of the fabric may be, for example, about 10% or 15% of the weight of the fabric, which can be divided in any fashion between the five applicators. For example, each applicator could apply 2% of the dye liquor for a 10% total or 3% for a total of 15% total or unequal amounts can be distributed by the different applicators.

FIG. 8 illustrates a modification of the location of the exit seal and drain pipe. In this arrangement, the exit seal 136 is located in a horizontal disposition for exit of the substrate horizontally and an exit guide roll 138 similarly located in the manner of the guide rolls 110, 112, 114 and 116 mounted similarly on the frame 108, deflects the substrate downwardly following the last applicator 104, for guiding to the exit seal 136.

In this variation the drain pipes 142 are located at the rear of the housing 54, and the gutters 141 slant downwardly rearwardly to drain liquid from the chamber 146 into the gutters 141 and drain pipes 142 to exit from the drain pipes 142 when the drain pipe closures 148 are open.

Variables, such as liquor flows, substrates speed, chemical formulations, purity of the nitrogen, degree of fabric preparation and fiber origin can have distinct effects upon the resulting shades. Shade variations can easily be achieved by varying the number of applicators engaged in the liquor application, even though the total flow would be the same. For example, it is possible to find that the liquor has penetrated to the back of the fabric substrate at a 15% wet pickup level through one applicator, while there will not be any evidence of liquor on the back of the fabric substrate if the same total wet pickup of 15% is applied in fractionated succession through five applicators.

An interesting advantage to the present invention is that when the foam collapses, the nitrogen used to create the foam is released into the environment within the chamber 68, thereby enhancing the nitrogen content in the chamber 68 in replenishing any nitrogen that has escaped from the chamber. This reduces the amount of nitrogen that must be supplied to the chamber 68.

The number of applicators used in an apparatus according to the present invention may be varied from one to as many as six or more, depending on the application flexibility desired. Further, the application of the liquor can be done at ambient temperature, but, if desired, elevated temperatures could be utilized to provide some advantage on certain fabrics and procedures.

When the fabric exits the chamber 68 the reduced, leuco-state dye is almost instantly oxidized as it is exposed to ambient air.

While the drawings illustrate and the detailed description describes an apparatus having four applicators, it should be understood that the apparatus can be operated with all or less than all applicators, including with only one applicator, actively applying foamed dye, and that the invention may be practiced with apparatus made with only one applicator therein or any desired number of applicators, all of which may be active or some of which may be inactive.

The pressure of nitrogen within the chamber 68 need be only slightly more than atmospheric pressure. It needs to be sufficiently higher than atmospheric pressure to prevent ambient oxygen-containing atmosphere from entering the chamber 68 and causing oxidation of the applied dye.

In view of the aforesaid written description of the present invention, it will be readily understood by those skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to the preferred embodiment, it is to be understood that this disclosure is only illustrative of an example of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended nor is it to be construed to limit the present invention or otherwise exclude any other embodiment, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.

Claims

1. An apparatus for dyeing a traveling cellulosic textile substrate with a dye in leuco-state applied in a foam condition, comprising:

a housing having an interior chamber sealed from atmospheric air and through which said substrate travels from an entrance having a seal through which said substrate enters said chamber to an exit having a seal through which said substrate exists said chamber;

a supply of inert gas communicating with said chamber to provide an inert environment therein;

at least one foam applicator having an applicator face in said chamber and extending across the width of said substrate for applying foam containing said dye in leuco-state to said substrate in said chamber; and

a source of foam containing said leuco-state dye in the absence of any significant amount of oxygen, said foam generator communicating with said applicator for supplying said foamed leuco-state dye to said applicator.

2. The apparatus of claim 1, characterized further in that said foam contains a small controlled amount of oxygen.

3. The apparatus of claim 1, characterized further in that said supply of inert gas is under pressure to provide a pressurized inert environment in said chamber.

4. The apparatus of claim 1 characterized further in that said at least one applicator is spaced from said entrance to provide a free reach of said substrate in which air trapped in the interstices of said substrate is allowed to escape.

5. The apparatus of claim 1 characterized further in that said at least one applicator is spaced from said exit to allow foam on the substrate to collapse and deposit the leuco-state dye on said substrate before the substrate exits said chamber and is exposed to air.

6. The apparatus of claim 3 characterized further in that said at least one applicator is spaced from said exit to allow foam on the substrate to collapse and deposit the leuco-state dye onto said substrate before the substrate exits said chamber and is exposed to air.

7. The apparatus of claim 1 characterized in that said at least one applicator comprises a plurality of applicators disposed with spaces therebetween to allow foam to at least partially collapse and said leuco-state dye to at least partially deposit on said substrate before having foam applied by the following applicator.

8. The applicator of claim 7 characterized further by hold-down elements between said applicators for engaging said substrate to displace the substrate between applicators to maintain said substrate in foam receiving engagement with said applicator faces.

9. The apparatus of claim 1 characterized further in that said at least one applicator is parabolically shaped for uniform distribution of foam across the width of said substrate.

10. The apparatus of claim 7 characterized further in that said at least one applicator comprises a plurality of said parabolically shaped applicators disposed with spaces therebetween to allow foam to at least partially collapse and said leuco-state dye to at least partially deposit on said substrate before having foam applied by the following applicator.

11. The applicator of claim 10 characterized further by hold-down elements between said applicators for engaging said substrate to displace the substrate between applicators to maintain said substrate in foam receiving engagement with said applicators.

12. The apparatus of claim 1 characterized further in that said inert gas comprises nitrogen and said foam generator generates a foam primarily of nitrogen containing said leuco-state dye with said nitrogen contributing to the nitrogen contained in said chamber when said foam collapses.

13. The apparatus of claim 1 characterized in that said textile substrate is woven denim fabric and said leuco-state dye is indigo dye applied at a weight as little as approximately 10% to 15% of the weight of the fabric.

14. The apparatus of claim 1 characterized in that said housing has an openable cover sealingly mounted thereon, said hold-down elements are mounted on a frame movable for movement away from said spaces when said cover is open.

15. The apparatus of claim 11 characterized in that said hold-down elements are idler rollers under which said substrate travels.