WO2002029153A2

WO2002029153A2 - Process for infrared fixation of aqueous dyes and product thereof

Info

Publication number: WO2002029153A2
Application number: PCT/US2001/023939
Authority: WO
Inventors: Morton W. Reed
Original assignee: Milliken & Company
Priority date: 2000-09-29
Filing date: 2001-07-31
Publication date: 2002-04-11
Also published as: WO2002029153A3; AU2001279093A1

Abstract

A process for using infrared energy to fix acid dyes to textile substrates comprised of polyamide fibers is disclosed. This process is well suited for use on broadloom carpets, carpet tiles, and certain fabrics comprised of nylon, wool, or nylon-wool blends. Specifically, the inventive process utilizes infrared energy having a wavelength of about 1 to about 3 microns and energy density of at least 100 watts/square inch to fix the dyestuffs. Eliminating the requirement for steam by incorporating the use of infrared energy results in decreased processing costs, processing times, and deleterious environmental impact.

Description

PROCESS FOR INFRARED FIXATION OF AQUEOUS DYES AND PRODUCT THEREOF

TECHNICAL FIELD

This invention relates to a process for fixing aqueous acid dyes to polyamide fibers, wool fibers, and polyamide-wool fiber blends without the use of steam heat. Specifically, the present process utilizes infrared energy having a specific wavelength and energy density to fix the dyestuffs. By eliminating the requirement for steam and incorporating the use of infrared energy, processing costs, processing times, and environmental impact are reduced.

BACKGROUND

Traditionally, dye fixation has been accomplished by subjecting the freshly dyed textile to steam. Steam has long been held as a necessary component for dye fixation for aqueous dyes onto polyamide fibers. Steam heaters are also used for curing materials and for preventing condensate from forming on the interior ceilings of steam chambers. The present process suggests otherwise: in the present process, fixation of aqueous dyes onto polyamide (nylon) fibers is achieved by using infrared (IR) energy without the presence of steam.

The present IR process is more cost efficient and produces greater energy density than conventional steam techniques. A typical steam heater operates at a temperature of about 860 Rankine absolute (400° F), while the filament temperature of the short-wave, electric, infrared element used in the present process reaches a temperature of about 4460 Rankine. Thus, the energy density is hundreds of times greater with electric-generated IR energy.

Other dye fixation methods include subjecting the textile to radio frequency, microwave, or ultraviolet radiation. An undesired consequence of using radio frequency or microwave heating is that the entire wetted mass will be heated rather than the dyed surface. Also, the backing may heat faster than the wet fibers, thereby causing non-uniform setting of the dyes. Another method of dye fixation that has been explored uses infrared (IR) energy to fix the dyes. One method, as described in US Patent 3,972,127 to Hoshi, uses IR energy having a wavelength of 3.5 to 7 microns, accomplishing dye fixation by subjecting the substrate to IR and steam. Other methods using IR fixation involve the use of other dyes, that is, dyes in powder or non-aqueous form (such as is described, for example, in U.S. Patent 3,787,180 to Wegmuller). SUMMARY

A process for the continuous fixation of aqueous acid dyes onto a textile substrate made of nylon, wool, or blends of nylon and wool is disclosed, in which the textile substrate is exposed to infrared (IR) radiation of a wavelength ranging from about 1 to about 3 microns with an energy density of at least 100 watts per square inch. Energy density is defined here as the amount of radiation energy applied to a unit area of substrate and being either transmitted, absorbed, or reflected. One of the primary advantages of the present process, as described herein, is that it eliminates altogether the requirement for steam in the fixation process. Feed-forward and feed-back control algorithms based on the temperature and heat load of the dyed substrate are used to adjust the power level of the IR emitters. The economic and environmental benefits of eliminating the use of steam are significant, and the present process has applications on textile floor coverings (such as broadloom carpet, carpet tiles, area rugs, decorative rugs, and the like), as well as automotive and industrial

- fabrics.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a schematic representation of the present dye fixation process, described herein in accordance with one embodiment for use on carpet tiles.

DETAILED DESCRIPTION

The conventional dye fixation process typically includes the steps of dye application and steam heating. The present process, as described herein, replaces steam heating with infrared energy application, thereby creating a process consisting of dye application and infrared energy application. The present IR process is achieved by subjecting the freshly dyed textile substrate to energy from an infrared source, without including the application of steam in the process.

In Figure 1 , depicting one embodiment of the present invention, carpet tiles 2, having been dyed in dye station 10, are conveyed on moving belt 18 into infrared chamber 20. Within IR chamber 20 are several banks 22 of infrared emitters, which direct infrared energy onto carpet tiles 2. Cooling air is introduced into chamber 20 through air intake 24. This air absorbs excess heat from emitter banks 22, the heated air being vented through exhaust 26. It is believed that the heated air from exhaust 26 could be redirected for reuse later in the drying process, further contributing to the energy savings from the present process. Various aspects of the present process will be described in greater detail herein. The process is suitable for use with any textile comprised of nylon or wool yarns and fibers, or blends of nylon and wool, to which aqueous acid dyes are to be applied. Specific examples of suitable substrates include textile floor coverings (such as carpet tiles, broadloom carpeting, area rugs, decorative rugs, and the like), as may be created by tufting, weaving, bonding, needlepunch, and the like. The present IR process may also be used to achieve dye fixation on automotive and industrial fabrics, which may be created by tufting, weaving, knitting, or flocking.

Substrates that have backings attached thereto, such as carpet tiles 2, present a problem when subjected to radio frequency (RF) or microwave energy. This problem is due to the negative interaction between the energy source and the energy-absorbing properties of many commonly used backing materials, such as PVC. RF or microwave energy each tend to cause the backing to heat faster than the wet fibers, resulting in non-uniform dye fixation. Because IR energy tends to heat only the surface of the tile, dye fixation is accomplished in a more uniform and efficient manner.

In accordance with another embodiment, the present process for dye fixation is also suitable for broadloom carpets and automotive and industrial fabrics.

Dye station 10 is comprised of any dyeing apparatus known in the industry, including a dye apparatus having a plurality of individual gun bars. A particularly well-suited dye apparatus for this purpose is described in U.S. Patent Number 3,942,342, the disclosure of which is herein incorporated by reference. The preferred dyes are acid dyes or premetallized acid dyes, in an aqueous or water-gum solution. The water-gum solution, when used, serves to stabilize the dye molecules near the fibers, rather than near the backing, thereby making the dye/fiber system compatible with IR heating of the surface area.

Instead of entering a steamer, the substrate is conveyed on moving belt 18 through IR chamber 20. The dyed substrate must reach a temperature in the range of about 180° F to about 210° F to achieve fixation and prevent the fixed dyes from being affected by any additional steaming processes that may be used after fixation. The deleterious effects of steam are those associated with condensation from steam that subsequently drips onto the dyed substrate. A well-suited range of temperatures is from about 190° F to about 200° F.

The length of chamber 20 is such to produce a sufficient "dwell time" beneath IR heating banks 22 to adequately fix the dyes. An average of four banks 22 of emitters is needed for a chamber having a length of about 8 feet. This IR chamber length, typically about 8 to 10 feet, is considerably shorter than the conventional steamer length of about 140 feet. As a result, unlike conventional dye fixation techniques that may require as long as seven minutes, the desired results of the present process can be achieved with a dwell time of only about twenty seconds.

IR chamber 20 contains several spaced banks 22, each bank comprising a plurality of infrared emitters. Each bank 22 comprises 2 to 3 emitters, each emitter having a length of about 6 feet. The width of bank 22 is about 8 to about 10 inches. In one embodiment, these banks 22 are positioned across the path in perpendicular relation to tiles 2 moving through IR chamber 20. The IR emitters of bank 22 have sufficient power to raise the temperature of the wet substrate to between about 180° F to about 210° F.

The quartz-tube emitters used in infrared chamber 20 produce energy having a wavelength of about 1 to about 3 micrdns, with a wavelength of about 2 microns being particularly preferred. Thin films of water absorb IR radiation better at medium wavelengths (3 microns) but the optimal wavelength may be shorter (about 2 microns), especially since the objective is to penetrate the dye layer and heat the fiber surrounded by the liquid phase. Short wavelength IR sources allow for a high energy density, greater speed, and greater penetration through the dye film to the fiber surface so that small areas can be heated efficiently. The energy density produced by these emitters is at least about 100 watts/in².

There are several types of infrared emitters that may be used, although electrically powered IR emitters are most preferred for reasons that will become clear in the following discussion. Gas-powered IR sources operate at about 3460° R and are slower to heat up and cool down than similar electric sources. Unlike electric sources, the heat-up and cool-down processes can take as long as ten seconds. Steam-operated IR sources can take even longer than gas-powered sources, up to as much as several minutes due to the large thermal mass of steam-powered sources. Neither gas nor steam IR heaters are fast enough to prevent overheating of material that stops suddenly on a range.

Recently developed electric IR elements have low thermal mass and, as a result, can cool down or heat up in 1 to 2 seconds depending on the applied voltage. The emitters must have a response time of about one second, making them capable of quick shut-downs as may be necessary due to machine stops. One such example of IR emitters that may be used are Model EMB-500 emitters available from Heraeus Amersil. The temperature of the substrate is monitored and fed back to a controller that automatically varies the voltage downward from a maximum value of about 480 volts. As the voltage varies, the power varies to control the temperature of the emitters (and thus, the wet substrate being irradiated). If conveyor belt 18, on which the substrate is transported, stops for any reason, the controller shuts down the emitters, causing the emitters to reach a safe temperature of less than about 200° F in 2 seconds or less. This quick shut down is possible only with short-wave heating elements. The fast response time of the infrared emitters allows the temperature to be controlled in response to changes in the thermal loading of the system (as may be caused by variations in the wet pick-up of the substrate). This quick shut-down also eliminates the need for moving the infrared emitters away from the substrate or injecting a blast of air as a coolant, in case of a range stop.

In summary, one embodiment of the present process described herein involves the continuous fixation of acid dyes (in aqueous or water-gum solution) onto carpet tiles of various constructions consisting of nylon, wool, or nylon/wool blends. The dyed fibers are exposed to infrared radiation of a wavelength ranging from about 1 to about 3 microns with an energy density of at least 100 watts per square inch. Subjecting the substrate to such infrared energy raises the substrate temperatures to the range of about 180° F to about 210° F, temperatures that are sufficient to fix the dyes and to eliminate the need for steam in the process as would be conventionally used.

Having been subjected to energy from the infrared source, the substrate is then washed by any method known to those of skill in the art. The washing process serves to remove any gum residue that may remain on the substrate after dye fixation. Moisture is then removed from the substrate, such as by vacuuming, before the optional step of adding any desired finishing chemicals.

After the substrate has been washed, the substrate is dried in a conventional drying oven. The drying oven removes any moisture remaining from the washing process. One suitable drying technique uses a gas-fired impingement drier having a temperature of about 250° F to about 300° F and a dwell time of about 7 minutes. In terms of energy savings, the IR process, as described herein, uses 7 to 8 times less energy than a comparable process using steam. Thus, the present process provides improvements in processing costs, processing times, and capacity utilization. For these reasons, the present process represents a useful advancement over the prior art.

Claims

I claim:

1. A process for fixing liquid acid dyes to a textile substrate, said process comprising:

(a) applying said acid dyes to said textile substrate; and

(b) subjecting said dyed substrate to infrared energy, said infrared energy having a specified wavelength and energy density, said infrared energy causing said dyed substrate to reach a temperature sufficient to set said dyes.

2. The process of Claim 1 wherein said textile substrate is comprised of carpet tiles.

3. The process of Claim 2 wherein said textile substrate is comprised of fibers selected from the group consisting of nylon, wool, and blends of nylon and wool.

4. The process of Claim 1 wherein said textile substrate is a broadloom carpet.

5. The process of Claim 1 wherein said textile substrate is a fabric as may be formed from tufting, weaving, knitting, or flocking.

6. The process of Claim 1 wherein said acid dyes are premetallized acid dyes.

7. The process of Claim 1 wherein said infrared energy has a wavelength in the range of one to three microns and an energy density of greater than 100 watts per square inch.

8. The process of Claim 7 wherein said infrared energy has a wavelength of about two microns.

9. The process of Claim 1 wherein said temperature of said substrate during step (b) is in the range of about 180° F to about 210° F.

10. The process of Claim 9 wherein said temperature of said substrate during step (b) is in the range of about 190° F to about 200° F.

11. The process of Claim 1 wherein said substrate is subjected to said infrared energy for about 20 seconds.

12. A dyed textile product produced by the process of Claim 1.