SUSTAINABLE DYEING OF CELLULOSIC FABRICS IN TEXTILE MILLS

Abstract

A textile mill (100) includes a testing and recipe finalization station (104), pretreatment application machinery (106), dye application machinery (114), and a post-dye processing station (124). An associated process involves applying a pretreatment to the cellulosic fabric for cationizing the cellulosic fabric and applying a dye treatment to the cellulosic fabric. A recipe for the dyeing process includes a predetermined concentration of a cationizing agent of the pretreatment based at least in part on a desired concentration of the dyeing component. A two-stage drying and curing process for the pretreatment and other processing equipment and parameters are also described that ensure a high-quality dyeing process with reduced environmental impacts.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional patent application which claims priority to and the benefit of U.S. Provisional Application No. 63/536,283, filed Sep. 1, 2023, titled “Sustainable Dyeing of Cellulosic Fabrics in Textile Mills,” and U.S. Provisional Application No. 63/550,461, filed Feb. 6, 2024, titled “Sustainable Dyeing of Cellulosic Fabrics in Textile Mills,” which are hereby incorporated by reference (the Parent applications).

FIELD OF THE INVENTION

The present invention relates generally to sustainable processes for dyeing cellulosic fabrics and, in particular, to processes for adapting promising sustainable dye processes and associated chemistries for textile mill environments, thereby realizing potential benefits of those processes and chemistries.

BACKGROUND OF THE INVENTION

The environmental impacts of dyeing cellulosic fabrics in textile mills are well-known. Cellulosic fabrics—especially fabrics including cotton fibers such as cotton knits, woven cotton, and cotton blends—are highly desired owing to their excellent physical and chemical characteristics such as natural comfort, feel, appearance, ease of production, hydrophilicity, good dyeability, color retention, biodegradability, and low cost. However, the discharge from textile mills where such fabrics are dyed and finished is often a cocktail of carcinogenic chemicals, dyes, salts, and heavy metals. In many cases, this discharge is dumped directly into rivers or streams.

Manufacturers have long sought improved processes for dyeing cellulosic fabrics that reduce environmental impacts. In this regard, various processes have been proposed that involve pretreating cellulosic fabrics to facilitate dyeing processes and/or reduce the environmental impacts of resulting effluents. Some of these processes involve pretreating the cellulosic fabric to improve dye uptake or exhaustion or reduce the need for certain additives during dyeing. One particularly promising process involves graft polymerization of a cationic vinyl monomer such as diallyldimethyl ammonioum chloride (DADMAC) into cotton using a thermal initiator. That process and the associated chemistry is described in detail in the Parent Applications which are incorporated herein by reference, and, for convenience, the process is referred to herein as the DADMAC process.

The DADMAC process has many potential advantages over convention processes for dyeing cellulosic fabrics. DADMAC is safe for human and environmental organisms. Indeed, poly-DADMAC is a USFDA approved polymer used for potable water treatment. In addition, dyed fabrics prepared using the DADMAC process exhibit excellent color yield and color fastness even when dyed without alkali or salt. In some cases, the dyed fabrics produced via this method also have antibacterial properties. Moreover, dyed fabrics produced via the DADMAC process allow for more complete exhaustion of dyes and enable recycling of the dye bath for improved environmental impact and safety. The DADMAC process also avoids certain carcinogens present in effluents of alternative processes, avoids producing bad odors, and allows the pretreated fabric to be washed only a single time to remove un-grafted monomer from the cotton in contrast to certain alternative processes that require multiple washings and neutralization processes. Accordingly, the DADMAC process has many potential advantages for fabric dyeing processes.

SUMMARY OF THE INVENTION

Despite the promise of proposed sustainable processes and chemistries for dyeing cellulosic fabrics, the potential of these processes can only be achieved if they are adapted for mill environments to yield high-quality textile products while maintaining the desired environmental and safety advantages. Adapting a proposed chemistry to the mill environment presents many challenges. For example, in connection with the DADMAC process, it has been found that, even though the pretreatment process and the dyeing process are implemented in successive fabric treatment processes, the relative concentrations of the DADMAC component and the dye component can be carefully controlled to improve the quality of the resulting dyed fabric, to optimize dye exhaustion, and to enhance dye solution recycling, thereby achieving various environmental and safety advantages. Moreover, different cellulosic fabrics, such as cotton knits, woven cotton, and cotton blends, in practice have different liquid absorbencies (that can be measured as water pick-up or WPU values) that affect the noted relative concentrations of the DADMAC and dye components. In addition, it has been found that conventional drying and curing processes can result in uneven dyeing, e.g., fabric steaking. Various other processes and parameters also need to be carefully controlled to achieve the desired advantages while yielding high-quality products.

The present invention is directed to processes that adapt certain proposed chemistries for sustainable dyeing of cellulosic fabrics to the mill environment as well as to the resulting dyed fabrics and other textile products such as cloths, clothing, towels, and bedding. The invention provides processes for controlling the relative concentrations of a cationizing agent and a dye component, for controlling such relative concentrations for different dyes and fabrics, and for controlling other processes and parameters to produce high-quality products while realizing the potential benefits of sustainable dyeing processes. The present invention also provides a two-stage drying and curing process that yields more evenly dyed textile products using the sustainable processes and chemistries. The invention thereby reduces environmental impacts and enhances safety.

In accordance with one aspect of the present invention, a process for dyeing cellulosic fabrics is provided. The process involves establishing a dyeing process for the cellulosic fabric including applying a pretreatment to the cellulosic fabric for cationizing the cellulosic fabric and applying a dye treatment to the cellulosic fabric. The pretreatment includes a cationizing agent and the dye treatment includes a dye component. The process further involves determining a recipe for the dyeing process including a predetermined concentration of the cationizing agent based at least in part on a desired concentration of the dyeing component. This recipe may be developed to ensure a high-quality product while achieving certain environmental and safety advantages. The pretreatment is provided in accordance with the recipe and applied to the cellulosic fabric. The dye treatment is then applied to the pretreated fabric.

The process for determining the recipe may involve determining a baseline value for the concentration of the cationizing agent based on the desired concentration of the dye component in the dye treatment. This may be based on a mathematical relationship, a table, or the like. The baseline value may further take into account or be adjusted based on a percentage of cellulosic material, such as cotton, in the fabric. The baseline value may be used in combination with a wet pick-up value for the fabric to determine a nominal value for the concentration of the cationizing agent. For example, the wet pick-up value may be determined by testing. The nominal value may be further adjusted, e.g., based on experience, experiments, or empirical evidence, to arrive at a final recipe.

The pretreatment may further include a cross-linking agent, a thermal initiator, and other components. In one implementation, the cross-linking agent may be tetra(ethylene glycol) diacrylate (TEGDA) and the thermal initiator may be sodium persulfate. Once the final concentration for the cationizing agent is determined, the concentrations of the cross-linking agent and thermal initiator may be determined as a function of the cationizing agent concentration.

The pretreatment can be applied by any of various processes including pad and spray application as well as wet-on-wet or wet-on-dry application. In the wet-on-wet application, the pretreatment can be applied while the fabric is in a wet state, thereby eliminating the need to dry the fabric (e.g., after pre-washing). A pad application process may generally include passing the fabric through a trough including the pretreatment solution and then passing the pretreatment fabric through rollers to remove excess pretreatment solution and ensure even distribution of the pretreatment solution. The fabric may be passed through two or more sets of rollers, e.g., with different characteristics and/or operating parameters (roller hardness, roller pressure, etc.). In a spray application process, the fabric may be washed and otherwise prepared for the dyeing process, dried, and then the wet or dry fabric may be sprayed with the pretreatment. The pretreated fabric can then be dried and cured, and then dyed as described above. Both the pad application and spray application processes have advantages depending on the specific dyeing application and other manufacturing considerations. The present invention further includes fabrics and other textile products produced using the noted methodology.

In accordance with another aspect of the present invention, a method is provided for processing a textile product to yield more even dyeing. The method involves providing a base fabric and applying a pretreatment and a dye to the base fabric. The pretreatment may be effective to reduce environmental impact associated with dyeing the base fabric as described above. The base fabric may then be processed to ensure even distribution of the dye across the fabric. For example, such processing may involve passing the base fabric between one or more sets of opposing rollers. The base fabric is then transported to a fabric drying machine. The fabric drying machine implements a two-stage drying process including a first stage where a first drying airflow is provided to the base fabric via one or more first ports and a second stage where a second drying airflow is provided to the base fabric via one or more second ports. Each of the first ports extends continuously across a majority of a width of a fabric drying interface of the drying machine and each of the second ports extends across only a minority of the width of the fabric drying interface. For example, the first ports may be slots extending across substantially the full width of the fabric and the second ports may be conventional circular ports.

In accordance with a still further aspect of the present invention, a drying machine is provided for drying textile products produced by applying a pretreatment to a base fabric for reducing an environmental impact of dyeing the base fabric and applying a dye to the base fabric. The drying machine includes a first stage where a first drying airflow is provided via one or more first ports and a second stage where a second drying airflow is provided via one or more second ports. Each of the first ports extends across a majority of a width of a fabric drying interface of the machine and each of the second ports extends across only a minority of a width of the fabric drying interface. The machine further includes a fabric drive for moving the base fabric in a first direction through the drying machine between the first stage and the second stage. For example, the first ports may be longitudinal vents and the second ports may be circular vents.

The invention also encompasses various additional refinements that enable the advantages of sustainable dye processes to be realized in textile mill environments. These include fabric feed and de-curling systems that avoid streaking or uneven dyeing of fabrics. The invention thereby achieves high-quality dyeing of textile products, in a sustainable process, leveraging existing equipment in some cases, without unduly complicating the dyeing process.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and further advantages thereof, reference is now made to the following detailed description, taken in conjunction with the drawings, in which:

FIG. 1 is a schematic diagram of a textile mill in accordance with the present invention;

FIG. 2 is a flowchart providing a high-level overview of a production operation in accordance with the present invention;

FIG. 3 is a schematic diagram illustrating certain preprocessing of the production operation of FIG. 2;

FIG. 4 is a flowchart illustrating a pretreatment process of the operation of FIG. 2;

FIG. 5 is a flowchart illustrating alternative hot wash and dyeing processes of the operation of FIG. 2;

FIGS. 6A-6C illustrate a nip testing and evaluation process of the operation of FIG. 2;

FIG. 7 is a side view illustrating a pretreatment station where, of the operation of FIG. 2, fabric is passed through troughs including a bath of pretreatment;

FIG. 8 shows side and perspective views illustrating rollers of the pretreatment station of FIG. 7;

FIG. 9 is a perspective view illustrating belts for transporting the pretreated fabric into a stenter frame in the operation of FIG. 2;

FIG. 10 is a perspective view illustrating application and drying equipment in accordance with the present invention;

FIGS. 11 and 12 are top and perspective views, respectively, showing the air vents of a first stage of a drying and curing machine in accordance with the present invention;

FIGS. 13 and 14 are top and perspective views, respectively, showing the air vents of a second stage of a drying and curing machine in accordance with the present invention;

FIGS. 15A and 15B are perspective views showing first and second stages, respectively, of a de-curling system in accordance with the present invention;

FIG. 16 is a perspective view showing a spray applicator that may be used in a pretreatment process in accordance with the present invention; and

FIG. 17 illustrates a bulk dyeing (batch exhaust) process in accordance with the present invention.

DETAILED DESCRIPTION

The present invention relates to a mill operation for processing cellulosic fabrics that involves a cationizing pretreatment followed by application of a dye and related processing. In particular, the invention involves controlling the relative concentrations of the cationizing agent and dyestuff as well as other components to produce a high-quality product while achieving environmental and safety advantages as described above. Additional inventive processes and systems are described for improved processing of the fabrics including a novel drying machine and process. In the following description, the invention is set forth in relation to specific DADMAC pretreatment chemistries, specific cotton-containing fabrics, and specific dyeing processes and systems. It will be appreciated that the invention is not limited to such chemistries, fabrics, processes, and equipment. Accordingly, the following description should be understood as exemplary and not by way of limitation.

By way of overview, the various processes described below generally involve a pretreatment process followed by a dye application process. The pretreatment solution formulation or recipe is carefully determined based on the fabric, fabric characteristics, and desired dyeing application, to optimize dye exhaustion and dye solution recycling. The overall process steps can generally include fabric preparation (e.g., testing, analysis, washing, and, optionally, drying), application of the pretreatment, drying and curing, application of the dye, and post dyeing processing (e.g., finishing and textile product production).

There are two main types of application processes for the pretreatment: pad and spray. The pad application process generally involves passing the fabric through a trough of the pretreatment solution and then passing the pretreated fabric through a pneumatic padding mangle. The pretreated fabric is then placed onto pins, stretched, and cured in a stenter frame (long length gas or electric oven for drying/curing textiles). The fabric is then taken up on a roll and is ready to be sent for dyeing. The pad application process is well-suited for open width knits and wovens. It also takes advantage of equipment that textile mills typically use for processing textiles.

As discussed in detail below, there are a number of key variables that may be controlled in the pad application process to ensure a high-quality products while realizing the benefits of a sustainable dyeing process. These include the number of troughs or baths and padding rollers used for the pretreatment application process. As described below, two or more sets of rollers with different characteristics may be used in a padding mangle. The amount of pressure applied to each roller (how hard it squeezes the fabric) may also be controlled to optimize removal of excess pretreatment solution and even spreading of the solution. In this regard, the uniformity of pressure by the rollers on the fabric, e.g., across the width of the roller, may also be monitored and corrected as necessary.

The quantity of pretreatment solution picked up by the fabric may also be considered. Different fabrics (e.g., different compositions and weaves) may have different propensities to take up the pretreatment solution for a given fabric submersion process. This can have an impact on the optimal recipe and dyeing process. A measure of this property, such as a standardized wet pick-up (WPU) value, may be measured and used in recipe determination. Contact or drag points between the wet, pretreated fabric and the processing machinery may also be minimized to avoid uneven application of the pretreatment and resulting uneven dyeing.

The other main application process is spray application. In this application, the pretreatment is sprayed onto wet or dry fabric. For example, a spray system such as the TexCoat G4 (scc FIG. 16) from Baldwin may be used to spray the fabric with the pretreatment. The pretreated fabric is then dried and cured in a stenter frame (e.g., in-line with the sprayer) and the fabric is dyed as in the roller process. The spray process has certain potential advantages. It may involve less water and chemical usage. In addition, the curing process is generally more efficient due to a lower water pick-up by the fabric. The wet-on-wet application is also dramatically simplified and greater processing speeds may be achieved.

Again, certain processing variables may be controlled for optimal performance. Generally, a WPU of 50-100%, relative to the fabric weight, is optimal for spray application. If the WPU is too low, the fabric may have non-uniform areas of the pretreatment thus giving a striped/speckled effect to the dyed fabric. As with roller application, it is also important to minimize contact points and control airflow during the drying/curing process.

In the nominal case, the pretreatment application process begins with a dry fabric. However, to eliminate a drying step (e.g., after prewashing), the pretreatment can be applied while the fabric is in a wet state. This is called wet-on-wet application. However, a number of modifications may be required. First, as the wet fabric is submersed in the pretreatment bath, some moisture may be transferred from the wet fabric to the pretreatment bath. This slightly dilutes the pretreatment solution. To compensate for this, it may be necessary to introduce a high-concentration of the pretreatment into the bath at a rate that counteracts the dilution. The rate of introduction will depend on the concentration of the introduced pretreatment, the wet pick-up differential, the bath interchange factor, and other considerations. It will be appreciated that dilution would not occur in spray applications. The wet pick-up value in the wet context will also need to be considered in altering the recipe.

There are also several variables that may be controlled in connection with the pretreatment curing process. The cure process dries and polymerizes the pretreatment to the fabric. Any defects in this process can result in quality issues even if the dyeing is free from defects. Some of the variables that may be carefully monitored and controlled include heat exposure (dwell) time, cure temperature, and airflow velocity/uniformity. In the last regard, the drying process may be optimized to avoid displacement of the still wet pretreatment by gas jets.

The cure time and temperature required depends on a combination of factors. These include fabric construction, pretreatment/dye recipe, fabric sensitivity to loss in strength, fabric tendency to retain moisture, and stenter frame efficiency. The general cure temperature range is 155-205° C., and the cure temperature would rarely be out of this range. The average is about 165-175° C. The general cure/dwell time required is about 90-150 seconds. A time of about 120 seconds is typical for normal fabric constructions and recipes.

Certain exemplary implementations will now be described with a particular emphasis on dyeing processes involving a wet-on-dry, roller application. While this is an advantageous application for reasons described above, the invention is not limited to this application.

FIG. 1 is a schematic diagram illustrating a textile mill 100 in accordance with the present invention. The mill 100 generally includes a testing and recipe finalization station 104, pretreatment application machinery 106, dye application machinery 114, and a post-dye processing station 124. It will be appreciated that this schematic diagram is simplified and additional stations, operations, and equipment may be involved in a textile mill. In addition, while the mill 100 is illustrated as a linear series of equipment and stations, the functionality of the present invention may be executed in different mill architectures, stations or equipment may be omitted or combined, equipment may be re-used, or the mill 100 may be otherwise modified.

Base fabric 102 to be processed is first delivered to the testing and recipe finalization station 104. At station 104, the fabric may be analyzed to determine certain material characteristics and properties of the fabric. For example, the fabric may be observed to determine the material of the fabric and a wet pick-up (WPU) test or other tests may be performed on the fabric. Based on the fabric and the WPU value of the fabric as well as the desired dye concentration, a recipe for the pretreatment may be determined as described below.

In the pretreatment machinery 106, one or more baths 108 of the pretreatment may be mixed and poured into one or more padding troughs. The fabric is then passed through the trough and through the treatment application equipment 110. The equipment 110 may include an oven or curing frame for curing the pretreatment. Once the pretreatment is applied to the fabric, the fabric may be passed through certain drying and finishing equipment 112.

In the illustrated mill 100, a dyeing process may then be executed on dry fabric by the dyeing machinery 114. As shown, the machinery 114 may include one or more baths 116 of dye solution including a predetermined concentration of dyestuff. The fabric is passed through the baths 116 into dye application equipment 118. As will be described below, an important advantage of the present invention is that the dye is exhausted or nearly exhausted from the dye solution as a result of the dye application process. Accordingly, the resulting dye solution is clear or nearly clear and can be recycled for use in multiple fabric dyeing processes, e.g., four or more successive processes. The illustrated equipment 114 includes a dye solution recovery repository 122 for recovering the dye solution for recycling. Finally, the illustrated equipment 114 may include certain drying and finishing equipment 120.

The mill 100 may further include a post-dye processing station 124. The nature of the station 124 may vary depending on the specific process desired by the customer. For example, the post-dye processing may involve washing, cutting, or other processes to produce a finished fabric 126.

Referring to FIG. 2, a high-level overview is shown of a production procedure 200 that may be implemented in a textile mill. The illustrated procedure 200 begins by obtaining (202) processing parameters for the procedure. As will be understood from the description below, various processing steps depend on these parameters. Accordingly, it is useful for the mill operator to obtain information regarding the characteristics of the fabric to be processed, the size of a production run, the dye or dyes to be applied, and the specific dyeing technique to be employed. Some of this information may be obtained from questionnaires filled out by the mill customer. Additionally or alternatively, certain parameters such as characteristics of the fabric material (e.g., whether the material is a cotton knit, woven cotton, or a cotton blend) may be determined by inspection or testing. The operator may also obtain information regarding the type of dyestuff to be used, the number of dyes used, and the quantity of each dye used. In addition, the operator may obtain information about processing techniques such as the dyeing method, e.g., whether the dyed product will be a blend/double dyed. This may include the current dyeing procedures and liquor ratio as well as the dyeing equipment to be employed. Additional parameters such as the WPU properties of the fabric can be determined by testing processes implemented using the equipment to be employed during production runs.

The mill operator may also verify fabric preparation. In the case of cotton knits, the fabrics should be split into open width and should be in prepared for dyeing (PFD)/ready for dyeing (RFD) state (scoured and bleached in jet vessel). In the case of woven cotton, fabrics need to be in PFD/RFD state, e.g., scoured and bleached on continuous frame or jet vessel. The mill operator will generally also obtain details of the application method such as whether the dye application will be wet-on-wet or wet-on-dry process and whether the mill equipment will be run in a one or two pads/troughs configuration. The mill operator may also need chemistry samples for the DADMAC pretreatment and dyes.

In general, to achieve the best results, the customer will be required to provide fabric samples for analysis (204) in the specific environment of the mill. The mill operator may inspect or test the fabric to determine the fiber composition of the fabric as well as other fabric characteristics such as the fabric's grams per square meter (GSM), yarn weight, whether the fabric is a knit or woven, and the WPU value of the fabric as will be discussed in more detail below. The operator may verify that the absorbency of the fabric is sufficient and uniform. For the DADMAC pretreatment process described below, it is generally desired that the WPU is at least 75%, for example, between about 75-85% for a cotton knit fabric, at least 60%, for example, between about 60-70% for cotton/poly knit blends, at least 50%, for example, between about 55-65% for cotton woven fabrics that are 100% cotton, and between about 50-60% for 50% cotton/50% poly woven fabrics.

Using this information about the fabrics, dyes, and processes, the operator can create (206) a recipe for the dyeing process. As will be understood from the description below, this generally involves starting with a baseline ratio of the concentration of the cationizing agent (e.g., DADMAC) used in the pretreatment process to the concentration of the dyestuff used in the dyeing process. This baseline ratio can be used in combination with the fabric's cotton content, WPU, and/or other factors to determine a nominal ratio for use in mixing the pretreatment. Further experimentation may be performed using slight variations from the nominal ratio to arrive at a final recipe for the mill procedure.

The illustrated procedure 200 further includes a lab verification process (208). The purpose of the lab verification process is to verify the percentage of pretreatment to be paired with the percentage of dyestuff. This verification process may be performed by a provider of the pretreatment or by a mill operator. As noted above, a WPU for the fabric may be provided by the mill customer. This WPU value may be verified by performing a test on the fabric as will be discussed in more detail below. In addition, a tester may verify that the lab pad apparatus has the ability to adjust bar pressure so that the bar pressure can be correlated to the resulting WPU. In this manner, the mill operator can ensure that the production equipment will provide a good product during production runs. The verification process may also involve validating (210) an optimal cure time for the fabric as will be described in more detail below. The tester may also do a small-scale dyeing process to confirm all process parameters prior to a production run.

The mill operator can then mix (212) the pretreatment. As described below, the various components of the pretreatment can be added in a specific order for optimal performance. The pretreatment can then be applied (214) to the fabric and cured. Once the pretreatment has been applied to the fabric, the mill operator may conduct (216) wet processing/dyeing of the fabric. This may involve scouring and dyeing using any of a variety of processes (e.g., batch jet exhaust, cold-pad batch, and continuous), some of which are described in detail below. The dyed fabric may then be evaluated and tested (218). Such evaluation and testing may involve evaluating color levelness, color fastness, and break strength (bursting strength testing). Finally, the illustrated procedure (200) involves processing to produce (220) a desired textile product. This may involve cutting, stitching, and other textile processes. The desired textile product may be clothing, bedding, towels, or other textile products.

FIG. 3 is a schematic diagram illustrating certain preprocessing functions 300 including a nip test 302, wet pick-up testing 304, and mixing the pretreatment 306. The nip test 302 is conducted to ensure that substantially even pressure is applied to the fabric by the rollers of the mill processing equipment. Over time, pneumatic rollers can degrade unevenly leading to nonuniform pressure from the rollers on the fabric. Generally, a test is performed using impression paper. The results are analyzed to identify any uneven pressure applied by the rollers that may affect the quality and evenness of dyeing. If necessary, the equipment can then be adjusted to ensure even pressure. This may be understood by reference to FIGS. 6A-6C. As shown, impression paper 602 is loaded between two nipping rollers 600. This paper, which is ink-impregnated and sensitive to pressure, then generates clear and visible markings to indicate the exact areas along the nip system where the nip pressure is too high or too low. After the paper 602 is placed between the rollers as shown in FIG. 6A, the nip rollers 600 are moved together in the regular nip position as shown in FIG. 6B and paper is passed through the rollers 600. The paper 602 is then removed and analyzed to identify any unevenness in roller pressure. FIG. 6C shows possible results including a proper result and improper results together with typical causes. Based on these results, rollers can be adjusted or replaced, loads can be balanced, or adjustments can otherwise be made to ensure even pressure across the rollers.

Referring again to FIG. 3, the preprocessing may further involve WPU testing 304. The purpose of the WPU testing is to verify the absorbency of the fabric. The WPU value of a given fabric is specific to the fabric and the equipment used in applications. To ensure the most consistent results, the WPU value should be verified using a sample of the specific fabric and on the equipment that will be used to apply the pretreatment in production. In one implementation, the operator can first cut a square from the fabric sample, for example, a 9″×9″ square. The sample piece can then be weighed on a scale to obtain and record the dry weight. Typically, the mill equipment will allow the operator to set the pad pressure on the pads used to apply the pretreatment. The operator can therefore adjust the pad pressure to a desired pressure, for example, two bar pressure to start.

The sample piece can then be soaked in a beaker filled with the pretreatment solution. The soaked fabric can then be run through the equipment pads set to the desired pressure. The wet fabric weight can then be measured and recorded. Once the dry and wet weights for the sample piece are thereby determined, the WPU can be determined by the following formula:

Wet Pick Up(WPU) %=((WetWeight/DryWeight)−1)*100

This process can then be repeated for different bar pressures, e.g., three bar pressure and four bar pressure. Based on these tests, the operator can choose the bar pressure that is closest to achieving the target WPU for the fabric. For example, the target WPU may be at least 50%, or more preferably, about 60% for woven fabric (100% cotton and CVC), at least 75% or, more preferably, about 85% for knit fabric (100% cotton), and 60-70% for a knit cotton/poly blend.

The preprocessing may further involve mixing the pretreatment 306. The pretreatment generally includes: a cationizing agent, referred to below by the trademark CLEAR 105 (solution of 64% DADMAC in water); a cross-linking agent, referred to below by the trademark CLEAR 104t (approximately 100% TEGDA-tetra(ethylene glycol) diacrylate), a thermal initiator, for example, sodium persulfate; a wetting agent; and any other auxiliary components. While various mixing processes are possible, the sequence and process described below have been found to provide excellent results. In addition, details concerning the various components and alternatives are described in detail in the Parent Applications.

In one implementation, the materials used for the mixing process may include: a large mixing tank for the pretreatment bath; a 5-gallon bucket for mixing the CLEAR 105, CLEAR 104, persulfate powders, and other pretreatment ingredients as noted above; a source of warm, but not hot (uncomfortable to touch) water; a mixing apparatus capable of vigorously mixing the solution; and a scale capable of weighing the pretreatment ingredients and water required for the bath.

A preferred order of mixing the ingredients involves first adding the CLEAR 105 and then the CLEAR 104. Alternatively, the CLEAR 104 and CLEAR 105 can be premixed and provided as a unit to be added first in the mixing process. Next, the sodium persulfate is added. The wetting agent is added after the sodium persulfate. Finally, any other auxiliary components are added. PPE equipment should be worn, preferably including leakproof glasses, full arm and body coverage, and waterproof boots/shoes.

The associated mixing procedure begins by calculating and weighing the amount of water required to make a bath of the pretreatment to the required trough size. The water is then added to the mixing vessel for further addition of chemicals. Next, the operator can calculate and weigh the amount of CLEAR 105 required for the treatment as described below. The liquid CLEAR 105 can be added to the bath in the vessel that already contains the water. The solution is then mixed with a motorized mixer vigorously for about two minutes or until uniform. The water should be about room temperature (about 25° C.). If the water is too hot, it may result in bath instability. Next, the required amount of DT-CLEAR 104t may be added to the mixing vessel and mixed with a motorized mixer vigorously for about two minutes or until fully mixed. As will be understood from the description below, the CLEAR 104 and 105 are generally provided in a constant ratio for the various pretreatment recipes. Accordingly, the CLEAR 104 and 105 can be premixed and provided to the mill operator as a single ingredient to simplify the process described above.

Next, the operator can calculate and weigh the amount of sodium persulfate required for the pretreatment. The required amount of sodium persulfate can be added to the mixing vessel and mixed with a motorized mixer for about two minutes or until fully mixed. The operator can then calculate and weigh the amount of wetting agent required for the treatment. The wetting agent is added to the solution and mixed with a motorized mixer vigorously for about two minutes or until fully mixed. Finally, any other auxiliary components are added to the pretreatment mixture. It is important to test these components for compatibility with the other pretreatment components prior to mixing.

The mixed pretreatment should preferably be stored at a temperature under 40° C. It should be kept out of direct sunlight and away from moisture. Under these conditions, all components of the pretreatment should be stable for approximately six months after delivery.

The preprocessing may further include validating the cure time 308 for the pretreatment. The curing step is an important part of the application of the pretreatment. The heat of the curing process induces the chemical reaction required for proper treatment. It is therefore essential to give the pretreatment sufficient time to cure, but it is also important to minimize heat exposure as too much time exposure at high temperature can cause yellowing of the fabric, reduction of the strength of the fabric, and wasted time of treatment. The cure time validation process helps to optimize the exposure time and run speed for a given pretreatment recipe and fabric treatment. The materials and equipment for the cure time validation process may include a laboratory pad for the pretreatment application, a laboratory oven for pretreatment curing, a dyeing machine for small-scale dyeing and the desired fabric and dyestuff.

The cure time validation process begins by padding the pretreatment solution on the fabric at a bar pad pressure of 2-5 (preferably, whatever bar pressure is used in production). The pretreated fabric is then placed in the laboratory oven at 160° C. for 240 seconds. This time and temperature will result in a full cure. The fabric that has been treated with the desired dye recipe is then dyed as desired. The operator can inspect the resulting dyed fabric to ensure that the dyeing results in level dyeing on the fabric and a clear or nearly clear dye bath.

This process is then repeated for another fabric piece. However, for the new fabric piece, the fabric is placed in a laboratory oven at 160° C. again, but this time for 120 seconds. The pretreated fabric is dyed and the results are inspected to confirm level dyeing on the fabric and a clear or nearly clear dye bath. If the fabric is dyed level and the dye bath is clear or nearly clear, the process may be repeated one or more times, in each case with 30 seconds less cure time. This process is repeated until the dyeing starts to lose quality as indicated by either unlevel dyeing on the fabric or a final dye bath that is not clear or nearly clear. Once this happens, the previous treatment with good results is selected as providing the optimized cure time. Additional tests using shorter and/or longer cure times as between successive tests may be used to more accurately determine an optimal cure time.

It has been found that one of the most important processes in the inventive procedure is determining the optimal concentration of the DADMAC (provided in the CLEAR 105) for a given dyeing and finishing process. Determining the optimal CLEAR 105 concentration provides a high-quality product while achieving the desired environmental and safety advantages. In particular, though the pretreatment process and the dyeing and finishing processes are performed in series, it has been found that the optimal concentration of the CLEAR 105 is dependent on the concentration of dyestuff in the dyeing and finishing process. Moreover, the concentrations of the other components of the pretreatment can be determined once the optimal concentration of CLEAR 105 is known.

Generally, as shown in FIG. 4, the resulting process 400 to determine an optimal recipe for the pretreatment begins by determining (402) the concentration of dyestuff in the desired dyeing and finishing process. Once the desired concentration of dyestuff is known, a baseline concentration value for the CLEAR 105 can be determined, for example, by looking up the CLEAR 105 concentration in a table 406. As will be understood from the description below, the relationship of the concentration of the dyestuff to the optimal concentration of CLEAR 105 is not linear. That is, the ratio varies depending on the concentration of the dyestuff.

Moreover, the optimal concentration of the CLEAR 105 is also a function of the fabric to be used. In particular, different fabrics will have different values of values of WPU. Optimal results are obtained by determining (404) the WPU value and using this value in calculating (408) a baseline concentration of CLEAR 105 as described below.

For a given dyeing and finishing application, the baseline concentration of CLEAR 105 is given by the following table:

TABLE 1
Highest Recommended % Concentration of
% dye OWF           DT-CLEAR 105
1.5% and below      4-8%
3%                  8-12%
4%                  12-17%
5%                  15-20%

where the dye concentration and CLEAR 105 concentration are given as a percentage on weight of fiber (OWF) values. Thus, for example, if the desired dyeing and finishing process involves a 5% concentration of dyestuff, the baseline value for the concentration of CLEAR 105 would be 15%. This baseline value for the concentration of CLEAR 105 is then divided by the WPU of the fabric expressed as a decimal number to obtain a nominal value for the concentration of CLEAR 105. Slight variations of this nominal value, e.g., ±10% or less, may then be tested (410) and the results analyzed (412) to determine an optimal concentration of CLEAR 105 and final recipe (414). In the case of blends, the percentage of dyestuff is divided by the percentage of cotton in the fabric to obtain an equivalent dye concentration. For example, for a 2% reactive dye applied to a 50/50 cotton/poly blend, the equivalent dye concentration is calculated as: 2%/50%=4% equivalent dye concentration. This equivalent dye concentration is then used in Table 1 above to obtain the baseline value for concentration of CLEAR 105.

Once the optimal concentration of CLEAR 105 is determined, the concentration of other ingredients of the pretreatment may be determined as a function of the concentration of CLEAR 105. In one implementation, the concentration of CLEAR 105 is divided by 10 to get the concentration of CLEAR 104t and the concentration of CLEAR 105 is divided by 40 to get the concentration of sodium persulfate. In addition, 4 g/L of non-ionic wetting agent (e.g., Rudolf Rucowet FN) is added to the bath (not adjusted for WPU). Any other auxiliary components of the pretreatment are added as desired for a particular application.

The most effective dye concentration range to take advantage of the pretreatment's benefits is 3.5-6% on weight of fiber (OWF) dyestuff in order to maximize time savings/depth of shade/effluent reduction. A typical recipe for 3.5-6% OWF dyestuff recipe on knits is:

• • 10.0-22.0% by weight DT-CLEAR 105;
  • 1.0-2.2% by weight DT-CLEAR 104t;
  • 0.3-0.5% by weight sodium persulfate;
  • 0.2-2.0% by weight non-ionic wetting agent; and
  • 88.5-73.3% by weight water.

The solution is padded at 85% WPU on the fabric and cured according to the conditions set forth herein.

A typical recipe for 3.5-6.0% OWF dyestuff recipe for wovens is:

• • 13.0-26.0% by weight DT-CLEAR 105;
  • 1.3-2.6% by weight DT-CLEAR 104t;
  • 0.45-0.7% by weight sodium persulfate;
  • 0.2-2.0% by weight non-ionic wetting agent; and
  • 85.0-68.7% by weight water.

The solution is padded and approximately 60% WPU on the fabric and cured as described herein.

The following examples illustrate this process for developing a pretreatment recipe.

Example 1

A customer wishes to develop a pretreatment recipe for a production procedure involving a 100% cotton knit that has an 80% WPU involving a 5% black dye. Table 1 indicates that, for a 5% concentration of black dye, the baseline value for the concentration of CLEAR 105 is 15%. The WPU value can then be used to determine the nominal value of CLEAR 105 concentration as follows:

• • 15% CLEAR 105 OWF/80% WPU=18.75% Bath Solution (187.5 g/l). (Formula: 15%/0.80=18.75%)

As noted above, the operator may then conduct experiments with this nominal value varied slightly to determine an optimal value for the concentration of CLEAR 105. Once the optimal value for the concentration of CLEAR 105 is known, the concentrations of the other components can be determined as follows:

• • Divide concentration of CLEAR 105 by 10 to get CLEAR 104t: 187.5/10=18.75 g/l CLEAR 104t;
  • Divide concentration of CLEAR 105 by 40 to get Sodium Persulfate concentration=187.5/40=4.68 g/l of Sodium Persulfate (never less than 0.375% OWF);
  • Add 4 g/l non-ionic wetting agent to bath (Not adjusted for WPU).

Example 2

Another customer wishes to develop a pretreatment recipe for a production procedure involving a 100% woven cotton fabric that has a 60% WPU and the customer intends to apply a 3% concentration of dyestuff in a dyeing and finishing process. From Table 1 above, it is determined that the 3% concentration of dyestuff corresponds to a 10% baseline concentration of CLEAR 105. Ignoring any changes to this baseline value resulting from experimenting with slight variations, the concentrations of the additional components can be determined as follows:

• • 10% CLEAR 105 (OWF)/60% WPU=166.6 g/l CLEAR 105;
  • Divide concentration of 105 by 10 to get g/l of CLEAR 104t bath concentration=16.6 g/l;
  • Divide concentration of 105 by 40 to get g/l of Sodium Persulfate bath concentration=4.2 g/l.

Example 3

A further customer wishes to develop a pretreatment recipe for a production procedure involving a 55% cotton/45% polyester knit fabric with a 65% WPU and desires to dye the fabric using a 2% reactive red dye solution. In this case, the 2% dye concentration is first adjusted by the percentage cotton in the fabric as follows: 2%/55%=3.63 equivalent dye concentration. This value can then be used to refer to Table 1 to obtain a baseline value for the concentration of CLEAR 105. It is noted that the dye concentration of 3.63 is not present in Table 1 as shown above. It will be appreciated that, in practice, Table 1 may be expanded to include more concentration values corresponding to a higher resolution of available concentrations. In other cases, concentration values may be linearly or nonlinearly interpolated to obtain a baseline value for the concentration of CLEAR 105. As always, the resulting baseline value may be varied slightly in experiments to determine an optimal concentration. As a further alternative, a closest value of the concentration of dyestuff may be used to obtain a nominal concentration of CLEAR 105. In this case, the last of these alternatives is employed to obtain a nominal concentration value for CLEAR 105 of 12%. The concentrations of the additional components may then be determined as follows:

• • Divide the 12% CLEAR by WPU to get bath concentration of 105=12%/65%=185 g/l CLEAR 105;
  • Divide the 185 g/l of CLEAR 105 by 10 to get CLEAR 104t: 185.0/10=18.5 g/l 104t.
  • Divide CLEAR 105 by 40 to get amount of Sodium Persulfate needed=4.6 g/l.

Example 4

A still further customer wishes to develop a pretreatment recipe for a production procedure involving 5% Remazol Black dye on 100% cotton, 175 GSM knit for batch exhaust with an 80% WPU. The following table shows the resulting recipe where the concentration of each component is given:

Chemical          g/l
DT-CLEAR 105      187.5
DT-CLEAR 104t     18.75
Sodium Persulfate 4.70
Wetting Agent     4.00
Water             785.05
Total             1000

Once the pretreatment recipe has been finalized and the pretreatment has been mixed, several steps need to be taken to ensure proper application of the pretreatment. To ensure that the fabric will be treated in a uniform manner, a nip impression test may be conducted as described above. In addition, the mill equipment may need to be modified to ensure that drag points on the fabric are minimized. If there are any long, sustained points of contact between the application machinery and the fabric, this may result in markings along the vertical direction of the fabric. If these vertical marks are observed, slight application equipment modification may be necessary. Application equipment often includes frame rails where the fabric moves into the drying and curing ovens. These rails may be removed from the equipment. The horizontal tension on the fabric may then need to be increased so that the fabric does not sag.

To apply the pretreatment to the fabric in a wet-on-dry process, a bath of the pretreatment is first prepared as described above. The pretreatment can then be poured from the mixing tank to fill up the padding trough with the required amount of pretreatment. The curing frame is then set to the appropriate run speed for a given cure time. For a conventional eight chamber frame, a run speed of approximately 12 m/min may generally be employed. However, in general, once the cure time has been determined, the run speed can be determined by measuring the length of the chamber frame and dividing this length by the desired cure time. It will be appreciated that each chamber of the curing frame should be set to the desired temperature for the given treatment. The fabric to be treated is then connected to a leader on the padding mangle for transport through the machine. As the treatment begins, an operator may monitor the process to ensure that the fabric gets sufficient absorption of the bath liquor and that it is being evenly applied. The fabric can then be run through the machinery as normal while monitoring the application process and ensuring that the curing frame is at the proper curing temperature. These steps may be modified somewhat for a wet-on-wet process.

Referring to FIG. 5, once the pretreatment has been applied and cured, wet processing procedures 500 may be implemented for dyeing and finishing the fabric. A variety of procedures may be implemented in this regard. These procedures generally involve hot wash and dyeing (502). FIG. 5 illustrates three examples of such processing: batch exhaust (504), cold pad batch (520), and continuous process (530). The batch exhaust process (504) begins with a pre-dye hot wash (506). This process may be executed in a jet or similar dye machine. The fabric is placed in the machine and the machine is filled with warm water. The temperature of the water is then raised to 65° C. and held at that temperature for 15 minutes. The water is then drained, and the machine is filled with cold water (508). The cold water is circulated for 10 minutes and then drained. If needed, the cold-water process can be repeated until the bath is clear. The machine is then drained, and the fabric is removed.

The dyeing procedure may then be executed with the fabric in a jet or similar dye machine. This process is initiated by filling (510) the machine with cold water and circulating for five minutes. The bath is then dosed with a non-ionic lubricant. Next, the bath is gradually heated (512) to 45° C. at a rate of 2° C. per minute. The dyestuff is then slowly added (514) over 30 minutes (30-minute linear dose) and the bath is then held at 45° C. for 15 minutes. Thereafter, the bath is heated to 60° C. at a rate of 1° C. per minute. The bath is then held 516 at 60° C. for 5 minutes. Finally, the bath is heated to 80° C. at 1° C. per minute and held for 15 minutes. The bath should be clear or nearly clear at the end of this step. The bath is then drained (517).

After the dyeing is complete, a cleanup process (518) is optionally executed. The cleanup may be skipped depending on end user requirements. Where cleanup is required, it may be executed by filling the machine with cold water and adding 1.0 g/L of scouring agent (if needed). For example, Apollo scour may be used as scouring agent. The water temperature is then raised to 95° C., held for 15 minutes, and then drained. Next, the machine is filled with cold water which is circulated for 10 minutes and then drained. This cold-water rinse is then repeated. If needed, the cold-water rinse process may be repeated until the water is clear with no cloudiness or suds. Normally, this is not required as the bath is completely clear at this point. The process may then continue with post dyeing finishing (540).

In the case of the cold pad batch process (520), a three-box washing process (522) is implemented after the pretreatment process. No soap is required in this process. This process involves three boxes. The first box will contain water at 80° C. The second box contains water at room temperature. The third box also contains water at room temperature. The fabric is passed through the three boxes in succession to execute the washing process. The fabric will then need to be re-dried before dyeing.

The cold pad batch dyeing procedure with continuous process cleanup is then executed. This process is initiated by padding (524) the dyestuff onto the fabric. No salt or alkali is required for this process. The fabric is then placed (526) onto a batching A-frame and continuously rotated for 3.0 hours. This time may vary depending on the concentration of the CLEAR 105 and dyestuff. The dyeing is now complete and the fabric is ready for rinsing. A two-box rinsing process (528) may be implemented for rinsing. This process involves a first box filled with water at 70-80° C. and a second box filled with cold water. The fabric is passed through the boxes in succession to implement the rinsing process. The fabric may then continue to finishing (540).

The continuous process (530) begins with three-box washing (532). As described above, this involves a first box containing water at 80° C. and second and third boxes each with water at room temperature. The fabric is passed in succession through the three boxes. The fabric will then need to be re-dried before continuous dyeing.

The continuous dyeing process is then initiated by padding (534) dyestuff onto the fabric at the desired concentration. Again, no salt or alkali is required. The fabric is then passed through steam heated to 160° C. for two minutes of exposure time 536. A two-box rinsing process (538) is then executed as described above involving a first box with a water temperature of 70-80° C. and a second box with cold water. The fabric is passed in succession through the two boxes. The process then continues to finishing (540).

In some cases, a small-scale lab dyeing procedure may be implemented prior to executing the mill process to validate the recipe. Before lab testing can be done, the fabrics should be hot wash. For example, for lab scale scouring, the fabric may be placed in boiling water for 10 minutes, rinsed with cold water in the sink for five minutes, and then dried. This may be initiated by weighing a sample piece of fabric, e.g., 12″×12″ square, that has been treated with the pretreatment. The sample piece may then be placed into a dyeing cylinder of laboratory dyeing equipment. The weight of the sample piece may be used to determine the amount of water to use. It is recommended that a 6:1-12:1 ratio is utilized. For example, if the sample weighs 10 g, 60-120 g of water may be used depending on the dyeing equipment. The water is then added to the cylinder with the fabric sample and the container is shaken vigorously to ensure that the fabric is completely wet.

FIG. 17 illustrates a bulk dyeing process (batch exhaust). The figure plots temperature versus time for the various identified process steps.

The required amount of dyestuff is then calculated and weighed. The dyestuff solution or powder is added to the cylinder and the container is then shaken vigorously. The cylinder can then be placed in the dyeing vessel and the machine is started. The dyeing procedure for the machine involves heating the vessel to 45° C. at a rate of 2° C. per minute, holding that temperature for 15 minutes, heating the vessel to 60° C. at a rate of 1° C. per minute, holding that temperature for 5 minutes, heating the vessel to 80° C. at a rate of 1° C. per minute, holding that temperature for 15 minutes, and finally cooling and removing the container. Once the specimen is dyed, the dye bath is analyzed for any color and the dyed fabric is analyzed for levelness. If the dye bath is not close to clear, the concentration of the pretreatment might have been too low for a given shade. If the fabric has a splotchy/heathered look and the dye bath is clear, the pretreatment concentration may have been too high for the given shade. Appropriate adjustments can then be made.

Alternatively, 3-5 yards of fabric may be scoured for use in the laboratory. The fabric may then be pretreated with the baseline recipe. The fabric can then be cut into pieces and dyed with a range of recipes around the expected dye concentration. For example, if black uses 6% dyestuff, the test pieces may be dyed using the test range of 4.5-7% with 0.5% increments. At some point in this range, the dye bath utilized for testing will begin to turn black (after dyeing). This will determine the optimal dyestuff concentration for the given pretreatment recipe. The optimal range will be 0.25% above or below the optimal concentration as thus identified.

As discussed above, the application of the pretreatment and dye are carefully controlled to ensure high-quality textile products with reduced environmental impact. It is also important to control handling of the fabric during and after application of the pretreatment, as well as drying and curing of the fabric, to avoid uneven dyeing or streaking, and to ensure that the resulting products are otherwise of high quality. These considerations are particularly acute in the context of textile products produced using the pretreatment and dyeing processes as described above due to the desire to carefully control application and uptake of the pretreatment and dyestuff.

Certain exemplary features of the processing and equipment are shown in FIGS. 7-14. As discussed above, the composition of the pretreatment in relation to the dye is critical in achieving the desired environmental advantages while providing high-quality products. In addition, consistent application of the pretreatment and dye is important to realizing these potential benefits. FIGS. 7-8 illustrate certain details of the pretreatment application process. Implementing the desired application of the pretreatment to the fabric involves two steps; submerging the fabric in a bath of the pretreatment and pressing the wetted fabric to force the pretreatment into the fabric, spread the pretreatment, remove excess pretreatment, and provide uniform application. As shown in FIG. 7, a web of the base fabric 700 passes through a bath of pretreatment contained in a trough 702. The path of the fabric 700 is controlled by rollers 704 and the speed of the fabric is set by a fabric drive (not shown). This speed is controlled so that the fabric 700 is submerged for a sufficient time to be saturated consistent with the test WPU as described above. It will be appreciated that the fabric 700 exiting the trough 702 may therefore be wet to the point of having drops or rivulets of the pretreatment on its surfaces.

The fabric then passes between opposing rollers 800 as shown in FIG. 8. The rollers 800 have a width at least equal to the width of the fabric and are closely spaced such that substantially uniform pressure is applied across the fabric. This is effective to press the pretreatment into the fabric, to gently squeeze excess pretreatment from the fabric, and to spread the pretreatment evenly across the fabric. FIG. 8 shows side and front views of the rollers 800 and, in this case, shows impression paper 802 being fed through the rollers to test the proper pressure distribution as described above.

The variables that may affect the roller application process include the number of baths and padding mangles used. To ensure proper penetration of the pretreatment into the fabric, a minimum of two baths are used. The same pretreatment formulation is used in each of the baths. Moreover, as noted above, it may be desired to use more than one set of rollers 704a and 704b. Different roller characteristics and pressures may be used on each of the rollers 704a or 704b. The first roller set 704a serves the main purpose of ensuring deep/comprehensive penetration of the fabric with the pretreatment solution. For the first roller, a harder rubber roll (e.g., Shore A hardness of 80-100) may be used with a higher roller bar pressure (e.g., 4-8 bar pressure). The second roller set 704b serves the main purpose of evenly coating the entirety of the fabric. It is generally a softer rubber roll (e.g., Shore A hardness of 65-85) with a lower roller pressure (e.g., 1-3 bar pressure).

It is important that this even distribution of the pretreatment can be maintained until the pretreatment is fully dried and cured. Otherwise, uneven dyeing may ensue due to varying properties of the pretreated fabric. The most common points of contact take place in two areas of the process and machinery: the fabric feed system and the de-curlers. The fabric feed system holds up the fabric to ensure that it does not get caught in the machinery. Conventionally, static rails are used to feed the fabric directly into the stenter frame. To minimize or substantially avoid pressure points that may displace the pretreatment in connection with the fabric feed system, the fabric is transported from the pretreatment application machine to a drying and curing machine on moving rubber cables 900 as shown in FIG. 9. The cables 900 are thick and soft to reduce pressure points on the fabric. As will be understood from the description below, the fabric moves through an elongate, heated drying machine to dry and cure the pretreated fabric. The cables 900 are driven by pulleys 902 at a speed that matches the fabric speed in the drying machine so that friction between the fabric and the fabric support structure of the drying machine is minimized. In this manner, displacement of the pretreatment due to friction or pressure is minimized between application of the pretreatment and drying/curing of the pretreated fabric.

The other area where pressure points are potentially problematic in the inventive system and process is the stenter frame de-curlers. The de-curlers force the fabric, e.g., a knit fabric, to open to full width and not curl on the edges until it can be fixed to the pins that hold the fabric stable while it passes through the stenter frame. This is necessary as knit fabrics tend to curl resulting in nonuniform heat exposure. However, if the de-curlers pull on the fabric with too much force, a pattern can be imprinted on the fabric at the edges.

To avoid this, a two-part de-curling system is employed. The first part is a spreader roller 1500 as depicted in FIG. 15A. For example, this may include a spreading device LG 067 from Erhhardt-Leimer. The second part may be a pneumatic spreader 1502 as shown in FIG. 15B. For example, this may include a pneumatic selvedge opener LP 03 from the same company. Together, these devices accomplish de-curling in the inventive system and process without causing patterns or artifacts in the dyeing process.

FIG. 10 illustrates the application and drying equipment 1000. The equipment 1000 generally includes an application machine 1002 and a drying machine 1004 or Stenter frame. Operation of the machines 1002 and 1004 is closely coordinated and various process parameters, e.g., start/stop, fabric speed, drying temperature, drying airspeed, and the like, can be controlled by an operator 1006 at a computer-based operating panel 1008. As shown, the drying machine 1004 includes a number of chambers 1010. Each of the chambers 1010 is heated and can provide a drying airflow to dry and cure the fabric. The fabric moves slowly along an elongate path through the series of chambers 1010 so that the fabric is dried, and the pretreated fabric is cured when the fabric exits the drying machine.

In a conventional drying machine used to dry dyed fabric, the chambers function as ovens to heat and dry the fabric. In addition, air is blown at the fabric to assist in drying. Conventionally, air is driven at high velocity through circular holes distributed across the length (measured along the longitudinal axis that the fabric travels through the series of chambers) and width (measured transverse to the longitudinal axis) of the machine. This has been found to provide for efficient drying.

However, it has been found that such high velocity air delivery, focused on areas near the circular openings, can displace the pretreatment in the first chambers before the pretreatment has set adequately. Because subsequent application of the dye is dependent on the pretreatment, this can result in uneven dye application or streaking of the finished fabric or other textile product. This is avoided, in the illustrated machine, by using a two-stage drying and curing process. In the initial stage, corresponding to about the first one or four chambers (depending, e.g., on the fabric speed, temperature, air flow rate, and the specific cloth/pretreatment application), air is blown onto the fabric via elongate vents 1100 as shown in FIGS. 11-12. The vents 1100 extend across at least a majority of the width, w, of the fabric interface (e.g., across the full width) of the drying machine and, therefore, across the width of the fabric. The vents 1100 are connected to a common plenum that receives heated air, pressurized by a fan or turbine such that the velocity and pressure across each of the events is substantially constant. At least the bottom chamber is replaced, but replacement of the bottom and top chambers is preferred. In this manner, any localized high-pressure areas that could displace the pretreatment are reduced or substantially eliminated.

After the fabric has passed through this initial stage of, perhaps, 1-4 chambers, the pretreatment has dried and set sufficiently that higher velocity airflows can be directed at the fabric for more efficient drying without displacing the pretreatment. For example, ports having a smaller cross-section for high-airflow velocity, e.g., extending across a minority of the fabric interface width and over a short length of the fabric travel path, can be utilized. For example, as shown in FIGS. 13-14, circular vents 1300 distributed across the width, w, of the fabric interface of the machine, and across multiple chambers 1302, may be employed. Again, the vents 1300 in each chamber 1302 may be connected to a common plenum that receives heated air that is pressurized by a fan or turbine.

Though two stages are illustrated, more stages may be utilized. The different stages may be defined by different vent configurations (e.g., a less abrupt transition from full width vents to circular vents), different airflow velocities, different temperatures, and the like. These parameters may vary depending on the fabric, the pretreatment composition, the roller pressure, the expected dyeing application, and other factors. In any event, the desired result may be the substantially uniform application of the pretreatment across the dried and cured fabric, where the pretreatment is optimized for the ensuing dyeing process.

The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.

Claims

1. A method for use in dyeing cellulosic fabric, comprising:

establishing a dyeing process for said cellulosic fabric including applying a pretreatment to said cellulosic fabric for cationizing said cellulosic fabric, said pretreatment including a cationizing agent, and applying a dye treatment to said cellulosic fabric, said dye treatment including a dye component;

selecting a nominal recipe for said dyeing process including a predetermined concentration of said cationizing agent based at least in part on a desired concentration of said dye component to be applied to said cellulosic fabric;

first providing said pretreatment in accordance with said nominal recipe;

first applying said pretreatment to said cellulosic fabric;

second providing said dye treatment; and

second applying said dye treatment to said cellulosic fabric.

2. The method of claim 1, wherein said selecting comprises determining said nominal recipe based at least in part on a material of said cellulosic fabric.

3. The method of claim 2, wherein said selecting comprises determining said nominal recipe based at least in part on a cotton content of said material.

4. The method of claim 1, wherein said selecting comprises determining said nominal recipe based at least in part on a wet pick-up of said cellulosic fabric.

5. The method of claim 4, wherein said wet pick-up is determined for the cellulosic fabric and for equipment to be used in applying said pretreatment in production by obtaining a sample piece of said cellulosic fabric, obtaining a preprocessing weight for said sample piece, applying said pretreatment to said sample piece, processing said sample piece in said equipment, obtaining a postprocessing weight of said sample piece, and using said preprocessing and postprocessing weights to obtain a wet pick-up value.

6. The method of claim 1, wherein said selecting comprises determining a concentration of said cationizing agent based on a desired concentration of said dye component and a wet pick-up of said cellulosic fabric.

7. The method of claim 1, wherein said nominal recipe further includes a cross-linking agent and a thermal initiator.

8. The method of claim 7, wherein said cross-linking agent is tetra(ethylene glycol) diacrylate (TEGDA).

9. The method of claim 7, wherein said thermal initiator is sodium persulfate.

10. The method of claim 1, wherein said nominal recipe has a higher ratio of the predetermined concentration of said cationizing agent to said desired concentration of said dye component at a higher desired dye concentration of said dye component than at a lower desired dye concentration of said dye component.

11. The method of claim 10, wherein said ratio is about 2.0 for said higher desired dye concentration and is less than 2.0 for said lower desired dye concentration.

12. The method of claim 11, wherein said higher desired dye concentration is 5%.

13. The method of claim 1, wherein said step of first providing comprises forming a mixture of water, said cationizing agent, a cross-linking agent, a thermal initiator, and at least one additional component.

14. The method of claim 13, where said step of first providing comprises providing a first mixture of said cationizing agent and said cross-linking agent, adding said thermal initiator to said first mixture to provide a second mixture, and adding said at least one additional component after forming said second mixture.

15. A fabric manufactured by the process of any of the preceding claims.

16. A textile product manufactured by the process of any of the preceding claims.

17. A method for use in processing a textile product, comprising:

providing a base fabric;

first applying a pretreatment to said base fabric, said pretreatment effective to reduce an environmental impact associated with dyeing said base fabric;

second applying a dye to said base fabric;

processing said base fabric to ensure even distribution of said dye across said base fabric;

transporting said base fabric to a drying machine; and

drying said base fabric, at said drying machine having a fabric drying interface, using a two-stage drying process including a first stage where a first drying airflow is provided to said base fabric via one or more first ports extending continuously across a majority of a width of said fabric drying interface, and a second stage where a second drying airflow is provided to said base fabric via one or more second ports, each said second port extending across only a minority of a width of said fabric drying interface.

18. The method of claim 17, wherein said base fabric is a cellulosic fabric.

19. The method of claim 17, wherein said base fabric comprises, at least in part, cotton.

20. The method of claim 17, wherein said pretreatment comprises a cationizing agent.

21. The method of claim 20, wherein said pretreatment further comprises a cross-linking agent and a thermal initiator.

22. The method of claim 17, wherein at least one of said first applying and second applying comprises passing said base fabric through a liquid bath.

23. The method of claim 17, wherein said processing comprises passing said base fabric between opposing rollers.

24. The method of claim 17, wherein said transporting comprises delivering said base fabric to said drying machine at a speed that matches a fabric speed of said drying machine.

25. The method of claim 17, wherein said drying machine has a fabric drive for moving said base fabric in a first direction through said drying machine and said width of said fabric drying interface is measured in a second direction transverse to said first direction.

26. The method of claim 25, wherein said one or more first ports comprise a vent having a longitudinal axis extending in said second direction.

27. The method of claim 26, wherein said one or more second ports comprise a circular vent.

28. A textile product produced using the method of any of claims 17-27.

29. A drying machine for drying a dyed textile product produced by applying a pretreatment to a base fabric for reducing an environmental impact of dyeing said base fabric and applying a dye to said base fabric, said drying machine comprising:

a first stage where a first drying airflow is provided via one or more first ports, each said first port extending continuously across a majority of a width of a fabric drying interface of said drying machine;

a second stage where a second drying airflow is provided via one or more second ports, each said second port extending across only a minority of a width of said fabric drying interface; and

a fabric drive for moving said base fabric in a first direction through said drying machine between said first stage and said second stage, wherein said width of said fabric drying interface is measured in a second direction transverse to said first direction.

30. The drying machine of claim 29, wherein said one or more first ports comprise a vent having a longitudinal axis extending in said second direction.

31. The drying machine of claim 30, wherein said one or more second ports comprise acircular vent.