Patent Application
20210071358
Denim jean production has been largely outsourced to China, Vietnam, India, Pakistan, Turkey, Mexico, Indonesia, and Bangladesh for years due to the low labor cost in those countries. Further, the denim brands have continually pressured the denim mills to reduce their margins and cost of the base denim fabric as well as the price of the final denim products. Accordingly, there appears to be little room to significantly reduce denim jean manufacturing costs in any measurable way. Compounding this issue is the fact that denim brands desire a higher degree of sustainability. Of course, the improvement needed in the environmental conditions in denim jean manufacturing is often associated with increased costs due to new processes, new chemicals, or equipment, none of which are traditionally associated with reduced costs.
The inventors surmised that the opportunity to reduce denim mill and garment manufacturing costs and perhaps improve sustainability lies in the denim garment laundry process. A substantial amount of the costs associated with the garment production is incurred at this stage as it takes several hours to complete the dry process and garment wash cycles which employ abrasive media, chemicals and from 7-15 gallons of water per jean. Before determining what factors to change to achieve significant wash savings along with improved sustainability, the inventors first had to understand the processes in the manufacture of denim fabric, which is later sewn into garments, often dry abraded, and later washed.
Denim fabric involves many weaving pattern practices, but the most common weaving practice for denim is where the warp yarns are dyed, and the weft yarns are their original natural color, or white. The iconic trait traditional denim possesses is where white warp yarns are immersed in indigo and/or sulfur dye, where the dye does not fully penetrate the yarn diameter. It is named “ring dye” because it is intended to leave a ring of indigo or sulfur dyestuff around a white core. The core can be understood to mean the area centrally located relative to the perimeter of the yarn. The iconic denim jeans look is then created by exposure to chemicals with stone or some form of abrasive washing or garment washing where the indigo or sulfur dye is removed to create a wide array of looks, often resulting in the common “salt and pepper” look of contrasting highs and lows.
As denim involves a spun (open ended or ring spun) basically white warp yarn being dyed in order to achieve the deep rich colors desired by the industry, denim mills have been developing techniques to better apply increasing amounts of indigo and sulfur dyes to the warp yarns. This development occurs at the early stages of the dying process. Spun cotton warp begin as simply uncleaned of natural impurities and undyed cotton fibers that are natural and essentially near white. The spun warp yarns are processed through a series of stages on what is commonly known as a “dye range.” The warp yarns are either treated singularly on a slasher type dye range, or the warp yarns are bundled together in groups or ropes on what is referred to as a rope range. On a rope range, individual warp yarns are bunched into groups of approximately 350-400 parallel yarns without twist in a grouping. Cotton is a naturally grown fiber that is exposed to contaminants and debris both organic and inorganic. In addition to the contaminants from the growing fields, there are plant-based contaminants such as cell wall waxes, oils and or fats that coat the cotton fibers. Collectively, these contaminants act as barriers resisting chemical and dye penetration of the spun yarn. Consequently standard practice in the denim mills is to thoroughly clean the yarns in the early steps on the dye range to remove these impurities. Denim mills have employed this standard practice for years and continue to do so today since it represents the state of the art.
This pre-dye process is generally referred to as scouring or preparation. The warp yarns are exposed to what is commonly known as a wash, detergent, or scour bath in order to remove the natural field and plant contaminants, impurities, dirt, fats and/or waxes. Prior art teaches that in order to achieve the desirable denim jean colors, the scour must penetrate the yarn completely or with deep penetration into the core in order to remove the waxes and impurities, which then allows the dye to accumulate in deep bands on the yarn and somewhat into the core. This deep yarn penetration of the dyes is thought to be the only way to achieve the dark dyed denim garment colors desired. Penetration of the scouring agents is assisted through the use of high temperatures of about 60-80° C. and higher and with the heavy use of alkaline chemicals employed in the scour bath or vat. These chemicals are traditionally comprised of a wetting agent with a concentration of approximately 8 g/L and caustic mixture of about 50% NaOH at a concentration of approximately 180 g/L. The high temperature alkaline bath with the wetting agent swells the yarns for better removal of the contaminants, debris, and waxes in the yarn and increases acceptance of the dyestuffs. After exposure to the scour bath, the yarns may be processed through a series of heated or steam filled rollers to provide a high temperature dwell time for the chemicals to be allowed sufficient time to react and clean the yarns before rinsing and immersion in the dye tank. Alternately the yarns may be processed through a series of rollers without any heat or steam just to provide increased dwell time. Traditional rinsing involves the yarns passing through one or more traditional clean water rinsing vats, and then ultimately processed through a set of nip rollers to squeeze excess water and chemicals before proceeding to the dyeing vats. The prior art teachings do not disclose in any way the impact of changing the scouring objectives as above or associating the yarn diameter or cotton quality with the scouring process parameters.
Upon completion of the scouring or preparation stage, the yarns then continue on to the dyeing stages, and beyond. All of these efforts produce a ring dyed yarn that once woven into denim fabric and then fabricated into denim garments will require significant amounts of water, chemicals, time, and energy to wash down the dyed denim garment to the color and characteristics standards specified by denim brands. Further the denim garments require additional dry processing through hand sanding, or laser abrading to achieve the worn look, along with the employment of the toxic chemicals potassium permanganate or sodium hydrochlorite, to brighten the abrasion area.
One subset of denim garments is FR, or flame resistant garments. Flame resistant garments are often worn in mining, public utility, gas, oil and other at-risk industries and environments. The process of applying chemicals such as halogenated hydrocarbons, organohalogen organophosphate, antimony oxides, and phosphate-based compounds and chemicals result in a garment with properties associated with increased dye fastness and or increased core penetration of dye. Those skilled in the art recognize that there are other chemicals and compounds used in the textile industry to achieve FR qualities. As a result, FR treated garments are increasingly resistant to color reduction methods in both dry and wet processing mentioned above. This increased resistance to color removal often leads to FR garments devoid of contemporary washes and finishes as they are either impossible or cost prohibitive to produce.
Through a series of numerous trials and analysis, the inventors discovered a number of absolutely novel denim mill ring dye related scouring process changes that significantly reduce denim jean costs by reducing water, energy, time and chemicals during the denim garment washing process. Not only are the denim garment manufacturing costs markedly reduced by the employment of this invention but uniquely the sustainability is also improved. This is a major breakthrough in denim garment production. Even further cost reductions were confirmed at the denim mill and the dry process where lasers are used to create the worn look, which can be local or global in effect.
The cost reductions at the denim mill involve energy, water and chemical reductions. The cost reductions in the dry process are the decrease in cycle time to laser or manually abrade the denim, and the achievement of the bright worn look in the absence of the toxic chemicals potassium permanganate or sodium hypochlorite. Moreover all these improvements occur without any capital investment for any new denim mill plant equipment or employee training. The beauty of this invention disclosed here for the first time is that simple changes to the scouring process parameters can generate the improved white core results and subsequent denim jean manufacturer cost and sustainability benefits. The invention disclosed in this patent application is called “CleanKore™” and remarkably results in heretofore unheard of combination of cost savings and environmental benefits.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
Inventors realized that associating dye color with depth of yarn penetration of dye in the prior art will not produce the benefits of this invention and specifically any reduction in garment dry process and/or wash process savings. Prior art and conventional denim ring dye mill practices created intends to allow deep penetration of indigo and/or sulfur dyestuffs towards or into the yarn center or core. The inventors realized that these current well accepted practices result in increased dry process, garment wash, and finishing related costs for the deeper indigo penetrates a yarn, the longer and more aggressively the yarn needs to be washed to reveal the white, natural or off-white colored core. These conventional practices of dyeing often dye, or partially dye, the very core of the yarn leaving finishing facilities little choice in their efforts to show the white interior yarn for high/low contrast other than bleaching the yarns with potassium permanganate. These more aggressive garment wash abrasion cycles or bleaching treatments will reduce yarn tensile strength, so fabric is less durable to wear. However, contrary to this well accepted practice, the inventors discovered the importance of thoroughly cleaning only the outside perimeter of the yarn, while leaving the core of the yarn filled with the original waxes and impurities. This novel inventive concept resists dye penetration and dye fixing into the white or natural colored yarn core and consequently preserves a larger portion of the white core than common practices or prior art. Hence the dry finishing or laundry process will be markedly improved since it will take less water, chemicals, time and energy to wash down or otherwise remove the indigo. This reduction in energies and chemicals used also improves overall fabric strength with the reduced damage to the cotton fibers. Inventors realized that attempts at preserving the white or natural colored core through various methods had the added benefit of also retaining the consistent circular shape of the core, or a core shape that follows the perimeter of the yarn, to achieve a more uniform dye and fastness. This finding is another embodiment of the invention. Additional benefits of a circular shaped core, or a core shape that more accurately represents the shape of the perimeter of the yarn will be expanded later, suffice to say this is a breakthrough over prior art.
The inventive breakthrough, CleanKore™, is first and foremost changes in the standard scouring process to achieve the results above. In fact the changes in the scouring process for this invention are strikingly the opposite of the state of the art practices. Where the prior art teaches to thoroughly clean and remove waxes, oils, fats, dirt, impurities and field contaminants from the yarn by scouring at high temperatures, high concentrations of chemicals and long dwell time, our invention teaches the reverse. Inventors first had to recognize that the varying components, described in detail later, combine to create a scour potential. These components can be adjusted to increase or decrease the scouring potential to better meet the goals of reduced cost combined with improved sustainability. CleanKore™ teaches to determine appropriate scour potential to limit dye penetration into the core by controlling the temperature, scour chemistry, the concentration of that chemistry, immersion time in that chemistry, nip pressure, and/or dwell time during the scour stage. Whereas, the current state of the art in denim mills teach to enhance dye penetration into the core of the yarn.
The results from this trial are striking. The control clearly reveals the penetration of the indigo dye all the way through the core in most instances; whereas, the penetration of the indigo dye in the CleanKore™ yarns is limited with more of the white core preserved. These results were repeated in the trials at two different foreign denim mills and are shown in
Simple changes in some of the scouring parameters described below can produce an improved white core post dyeing which in itself generates improved wash benefits and this is one embodiment of the invention. An improved white core is basically one where the indigo penetration and fastness into the white core is somewhat limited, so the core consists of mostly sections of white yarn with limited sections with white yarn that has indigo dye on the surface. Even 10-55% changes in some of the scouring parameters presented below can generate improved white cores. So one embodiment is to change some or all of the scouring parameters described below that are currently being used in production by 10-55% to generate improved white cores. At first glance, many yarns appear to have a white core but in fact the core is just a significantly lighter shade of blue when viewed by the eye in such close proximity to the dark perimeter. Cores that are dyed with sulfur or indigo dyestuffs may appear white until a well focused image is zoomed and the actual colors can be seen more accurately. The inventors actually performed this experiment several times to reveal the true color differences in the core from current practices vs the core produced from CleanKore™ technology. Yarns with dyed cores, even those dyed lighter than the perimeter, will require a potassium permanganate spray, or an equivalent treatment to achieve the desirable white color, contrary to yarns created with the disclosed invention. Another embodiment of the invention is to make some changes in the scouring parameters used for current production to ranges illustrated in the discussions below.
However, scouring parameters that produce an outstanding white core post dyeing generate extraordinary wash benefits. Outstanding white cores would be associated with very limited indigo dye penetration into the core so the core appears basically white. The disclosures in this invention show how to change the scouring parameters to achieve various levels of white cores post dyeing including changes that generate outstanding white cores that produce extraordinary wash benefits and this is another embodiment of the invention. This invention also allows a denim mill to control the depth of dye penetration. For whatever the reason, one brand may want the least amount of dye penetration possible and another brand may want around 25% dye penetration. By adjusting the scour parameters it is now possible for the first time to control the amount of dye penetration and this is another embodiment of the invention.
The inventors challenged the prior art and traditional methods of scouring. The result was that changes in the scouring parameters can produce surprising benefits. Scouring with prior art practices involves several methods intent on thorough removal of waxes, oils, debris, and impurities across the entire cross-section of the yarn. This method has been thought to be necessary to achieve darker colors, and results in dye penetration of about 30% or more into the core, and importantly, successfully fixing indigo or sulfur (converting soluble dyes to insoluble with reasonable fastness) to the center or core area of the cross-section. The inventive approach here is for thorough, yet minimally invasive scouring for the outer yarn surface only. This unique concept results, for the first time, in an outer yarn perimeter that is scoured while retaining a dye resistant core with waxes, impurities and contaminants. This invention discloses for the first time the six methods described below taken in part or in total to some degree to achieve this unique characteristic. This contaminated core retains the hydrophobic properties, resisting indigo or sulfur dye penetration and/or reducing or eliminating the amount of dye that can be successfully fixed in the core area of the warp yarn cross-section. Thus indigo or sulfur dyes can be removed from the outer yarn perimeter more easily (when compared to being removed from the areas of the yarn closer to or in the core or center of the yarn) during the initial garment desize, stonewash and/or enzyme abrasion step, and bleach washing process, but still maintain the excellent wash fastness (retention of dye on yarns after washing) for home washings. The improved fastness characteristics with improved white cores is a significant benefit of the invention and thus an embodiment of the invention. The improved white core can result in significant savings in overhead costs, water, energy, and chemicals in the laundry process for denim garments. Importantly, this invention will allow denim garments to be washed in much less time and in fewer wash cycles so that an increased number of garments can be processed with the same equipment and labor clearly generating substantial cost savings and efficiency. This benefit is an important embodiment of the invention.
These benefits will offer significant improvement within the FR treated garment industry as well. Retaining a larger, more significant portion of the white or natural color yarn core lessens the impact of the FR treatment, providing the industry for the first time with fabric that can be made with contemporary washing as well as dry processing and still be cost effective and this is an embodiment of the invention. Inventors project the availability of such garments will broaden acceptance of garments that protect the wearers, growing the FR garment industry and increasing safety. With the use of fewer chemicals, enzymes, stones, bleach, water and toxic substances such as potassium permanganate and sodium hypochlorite, sustainability benefits become appreciable.
The specific means to achieve these unusual and highly desirable results involve one or more of the following six embodiments or techniques taken individually or together to some degree and first disclosed in this invention and introduced below.
The first embodiment is the reducing or controlling the scouring temperature. Conventional scouring techniques involve temperatures achieved with the application of heat, or steam such as 50-80° C. and sometimes higher, where the raised temperature “opens” the yarns to better receive the caustic as well as weakens the bonds associated with the oils, fats and/or waxes. The heat is used to encourage total yarn scouring and which in turn increases the likelihood of increased yarn penetration of dye. CleanKore™ technology typically involves the reduction or control of the temperature of the scour box to scour only the outside of the yarns so as to permit dye penetration to only the outer portion of the yarn cross-section. Typical CleanKore™ procedure would involve the reduction of this temperature to room temperature or lower temperatures such as 30-45° C. implementing temperatures lower than those currently used in production temperature is an embodiment of the invention. The control and reduction of the temperature of the scour is an embodiment of the technology where the temperature could be used to better control the scour potential. Room temperature, for the sake of consistency is not always the current room temperature, but rather the highest room temperature experienced year round so that conditions can be predictable without regard to the weather. Alternatively, this control could extend to cooling scour boxes to the application of heat given the circumstances with other variables. Room temperature will vary in different parts of the world, but it is typically best to have the least amount of heat as possible which is an embodiment of the invention. Other techniques disclosed would have to be further adjusted or controlled to possibly account for parts of the world where room temperature would be much higher. A critical aspect of the invention is that, scouring temperature could be higher than room temperature if some or all of the other techniques disclosed are used to achieve scour potential that results in improved white cores.
A second embodiment of the invention is reducing or controlling the concentration of the chemicals used within the scouring stage. Concentration of wetting agents, which act as a lubricant in the scour vat, is reduced from the traditionally used 8 g/L to about 2 g/L. The range of wetter of the wetter could fluctuate from 1 g/L to as high as 4 g/L which would be a significant reduction in wetter when compared to traditional scour chemistry. However, wetting agent concentration in the scour vat can be reduced to any amount, but the preferred amount is about 2 g/L caustic. Caustic, which is the active ingredient in the scouring process is typically used has 100% flake, or a pre-diluted 50% concentration of sodium hydroxide. 100% flake should, in theory, be equivalent to double the volume of 50% pre-diluted. However, in practice 100% flake appears to have an increased scour potential over the equivalent 50% and scour concentrations are adjusted accordingly. One skilled in the art would understand that ordering or altering the concentrations to percentages other than 100% or 50% would follow the same principles of 50% and 100% concentrations while having different numbers being the only change. Caustic concentrations in CleanKore™ are significantly reduced from a traditional vat concentration of 180 g/L of 50% concentration to 60 g/L or less. However, an embodiment of the invention is to reduce caustic concentrations from current production by at least 10%. Some trials showed best results with the use of caustic concentration in the scour tank as low as 4 g/L of 100% caustic flake. Depending if other techniques are also used and the percentage of white core needed, the amount of caustic could substantially change. As was the case with scouring temperature, the concentration of caustic could be higher than 4 g/L if some or all of the other techniques disclosed are used to achieve scour potential that results in improved white cores. It will also depend upon the caustic concentration used.
A third embodiment is reducing or controlling immersion time in the scour vat or tank. The immersion time could be reduced by: 1). skipping rollers, 2). changing the path of rollers, 3). lowering or increasing the diameter of the rollers, 4). removing rollers, 5). reducing the collective volume of chemicals relative to the size of the vat or 6). any other practice that results in reduced immersion time in the scour vats. Reduction in immersion time of at least 10% from current production practices is an embodiment of the invention. Some trials conducted had immersion times of 21 seconds, 19.5 seconds and 18 seconds, which all produced great results. Immersion time can remain the same if some or all of the techniques disclosed are used. However, it is preferred to reduce the immersion time by 10-60% to get the optimal percentage of white core, and this is an embodiment of the invention.
The fourth embodiment is reducing or controlling the dwell time between the scouring tank and rinse tank. This can be accomplished by reducing or eliminating the heated or steam rollers between the scour tank and rinse tank or by threading the yarns to travel directly to the rinse tank from the scour tank, and by selecting a scour and rinse tank with the desired proximity between one another. Reduction in dwell time of at least 10% from current production practices is an embodiment of the invention. Reduction in roller temperatures by 50% and more could also be an embodiment. Dwell time can remain the same if some or all of the techniques disclosed were used. However, it is preferred to reduce the dwell time to get the optimal percentage of white core. Before conducting one of our trials we encountered a facility that was devoid of a rinse tank after scour. This involved yarns being scoured with a lengthened dwell time between unnecessary rollers, and then immediately proceeding to the first dye tank. This results in increased scour potential, with increased scour dwell time and with scour continuing to occur in the first dye vat. Furthering the scour and consequently dye penetration into the yarn resulted in a dyed or partially dyed core. With the first dye tank being polluted with excess caustic, we can expect less efficient dyeing, as well as the increased potential for a red cast being seen. By adding a rinse tank we can significantly reduce the amount of scouring caustic polluting the dye tanks, as well as more accurately control the scour potential by limiting the dwell time and eliminating the scour effect in the first dye vat. This is an embodiment of the invention.
The fifth embodiment is the optimization of rinsing of the scour chemistry from the yarns, so as to remove the excess chemicals on the yarns in as few rinse vats as possible so as not to unnecessarily expose the yarns to water. The rinse vats are the baths that the yarns go through prior to immersion in the dye tank. This could include adding a rinse vat if there was a lack of one between scour and dye. This can be accomplished by reducing the number of rinsing vats from 3 to 2, or even to 1. Any means to reduce the amount of rinsing by reducing water or vat size or immersion time are other embodiments. Reduction in the rinse vats from current production practices is an embodiment of the invention. Number of rinse vats can remain the same if some or all of the techniques disclosed were used. However, it is preferred to reduce the rinse vats to get the optimal percentage of white core. This reduction of rinse vats or excess yarn exposure to water should not come at the expense of thoroughly rinsing the yarns of scouring chemistry, which can be monitored by measuring the pH and concentration of caustic in the rinse vat, as well as an elevation of pH in the first dye tank when compared to successive dye tanks.
The sixth embodiment is to increase nip pressure. Throughout the scouring and dyeing process, the warp yarns are exposed to a series of chemicals. Whether scouring, rinsing, dyeing, or sizing, the chemicals are applied through exposure in tanks, or vats, which, to varying degrees, soak the yarns. To remove the excess chemicals, the production involves several nip or squeeze rollers. The yarns are pinched between the nip rollers and it creates a wringing and squeezing action, reducing the volume of water, chemicals, or dye on or penetrated into the yarns. Traditionally the goal was to maximize scour to maximize the dye penetration. Consequently, the nip pressures were kept relatively low, about 4 bar, allowing relatively high volumes of chemical or dye to dwell on the yarns. However this invention again goes against the prior art practices such that another embodiment of this invention is to increase nip pressures to a range of about 5.0 to 7.0 bar and higher throughout the scour, dye, and rinse stages. This increased nip pressure serves the novel effect of reduced penetration of scour, and thus dye through the reduction of volume of each chemical or dye that is allowed to dwell and migrate into and/or become fasted to the warp yarns between stages which is an embodiment of this invention. Ideally these pressures are maintained across the whole range. When there's a lack of pressure or concerns of range fragility, an embodiment is the increased nip pressures specifically after the scour vat or tank. When possible, the first dye vat would be the second highest priority for increased nip pressure, with each successive dye tank being the next highest priority for increased nip pressure. Nip pressure can remain unchanged if some or all of the other techniques disclosed were used and still see significant improvement. However, it is preferred to increase the nip pressure to get the optimal percentage of white core.
One embodiment of the invention is the interrelationship between the previous embodiments. The different embodiments can be manipulated such that if so desired, as few as one of the embodiments can be used to achieve an ideal scour potential. For example, when untreated dry yarn passes to pre-treatment/scouring bath the dry to wet pick up can depend on the immersion time and the squeezing pressure. The caustic-cellulose reaction is very fast and when the concentration of caustic and wetting agent remains very high, it completely saturates the cotton yarn and the moisture pick up goes up. With reduction of immersion time, the dry to wet pick up can remain up to 60%. Also, with increase nip pressure maximum scouring liquor is extracted from the yarn. Due to less wet pick up and low concentration of caustic and wetting agent; the caustic reacts more with the fiber on the outer circumference of the cotton yarn and penetrates less. This also helps development of indigo &/or sulphur in the subsequent dyeing process. The fiber cross section development remains different from outer surface to inner surface of cotton yarn. Also, the amount of natural impurities of the cotton fiber increases from the outer surface to the inner core of yarn. Lumen remains unopen in core.
Higher nip pressure can extract more than 40% of liquor from the yarn and immediately after scouring the yarn passes through a wash box which further eliminates the caustic. This helps soda-cellulose formation more on the outer layer then inner core. Also, when cotton yarn with much less amount of caustic passes through the first indigo box, the strike rate of indigo solution on the yarn remains less compared to full mercerized or causticized cotton yarn. These two phenomena put together helps achieve a white core.
The inventors appreciated that although the optimum scour potential may involve utilization of all these techniques, excellent results were obtained with some adjustments to the scour parameters. For example, the concentration of caustic could be 60 g/L of 50% concentration or even higher so long as the immersion time, temperature, dwell time, rinse time and nip pressure were controlled to still deliver a core that was not scoured. This would also apply to a similar ratio of 100% caustic flake. Washdown savings will still be significant even if not maximized. The same is true for skipping some of the techniques so long as employment of the other techniques generate a core which is largely not scoured. Other techniques can be applied in tandem with some or all of the techniques disclosed as long as the outcome is an outer yarn perimeter that is scoured while retaining a dye resistant core with waxes, impurities and contaminants.
Relative to threading techniques, one embodiment of this invention is to achieve some of the results above by changing the warp yarn or rope threading path. The manufacturers of the dye range machinery create tanks, or vats within which the warp yarns are to pass to be exposed to chemicals as depicted in
One embodiment of this invention is to employ one or more of these techniques in the denim mill to varying degrees. So some of these techniques could be employed but with some variations to the specific process parameters described above. A further embodiment of this invention is to employ all of these techniques. The examples below show the scouring parameters at a U.S. denim mill, one foreign denim mill and another foreign denim mill that generated varying degrees of scour in or inwards toward the core (the area of the yarn cross section more centrally located relative to the outside perimeter) and thus varying degrees of white core post dyeing. All these scour techniques employed in the trials were against the prior art practices but disclosed in this CleanKore™ invention. However, all the results were so far above the prior art that all resulted in considerable wash savings at the denim jean manufacturer. The examples below illustrate just a few of the trials conducted by the inventors. The trials in EXAMPLE A produced a denim fabric that was washed down in half the time vs the standard control denim fabric as illustrated in
EXAMPLE A. Dye range scour parameters, where the scour tank is processed at room temperature in a U.S. denim mill trial that produced good results.
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/min
g/L
1
indicates data missing or illegible when filed
In this example, the main adjustments were a reduction in caustic concentration, a reduction in scour wetter, reduction in scouring temperature and higher nip pressure. Similar results were obtained from the foreign denim mill trial, the scouring parameter of which are shown in EXAMPLE B.
EXAMPLE B. Dye range scour parameters where the scour tank is processed at room temperature in a foreign denim mill that produced good results
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4
8
indicates data missing or illegible when filed
In this example, the main adjustments were a reduction in scour wetter and reducing scouring temperature.
EXAMPLE C. Dye range scour parameters where the scour tank is processed at room temperature in a foreign denim mill that produced extraordinary Results
Ring
1
1 -
.67,
d/min
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EXAMPLE C used three different embodiments of the invention, the scour potential for the trial fabric were adjusted to provide the optimal perimeter scour. The caustic was reduced to 4 g/L of 100% flake of the same and the wetter was reduced to 2 g/L, the scour immersion was reduced to 18 seconds and the scour temperature was reduced to room temperature. With the reduction in both caustic scour and wetter concentrations, a reduction in immersion time and reduced scouring temperature, the outcome with the relatively small cotton count yarns was revolutionary. The perimeter of the yarn was successfully scoured, readily receiving dye with successful fixing, and warp yarn cores that were previously slightly hydrophilic were now nearly completely hydrophobic with very little dye penetration and even less dye that was successfully fixed. Achievement of the white core properties post-dyeing along with satisfactory fastness along the yarn perimeter is a key embodiment because poor fastness would cause the indigo to be removed at an unacceptable rate during normal washing in home laundries.
Yet another embodiment of this invention is to employ all of these techniques simultaneously at or near their optimum settings.
Inventors recognized that the efficacy and duration of scour or scour potential is measured as effect over time over area of the yarn cross-section. A yarn count of 6.0/1 has a diameter of 0.0146″ where a yarn count of 8.0/1 has a diameter of 0.01263″ which is a 13.5% reduction in diameter and a 25% reduction in area of a cross section. The yarns used in the second foreign trial were 10.0/1 singles with a diameter of 0.011294″ which is a 23% reduction in diameter when compared to 6.0/1 yarns. This equates to a 40% reduction in cross-section area. As the invention is relevant to limiting the scour to reduce the area that the dye can effectively penetrate and more importantly fix to the yarn, it only stands to reason that the smaller diameter yarns should be exposed to a reduced scour potential. This novel approach of pairing scouring potential with the yarn diameter is revolutionary, and furthers the benefits of the CleanKore™ technology.
With the use of higher yarn count and the smaller diameters (with twist constant) and traditional scouring techniques, those skilled in the art would anticipate a completely or more thoroughly scoured yarn, and consequently completely dyed warp yarn cross section. With our inventive concept, scouring must be reduced in typical yarns to achieve the white core and limited indigo or sulfur penetration. With our invention the scouring, or scour potential, must be even further reduced with the use of small diameter yarns of identical twists and this is an embodiment of the invention. In fact, this was the case in the trials at the second foreign mill as shown in EXAMPLE C.
Yarn twist, for purposes of this document, can be understood to mean the number of twist rotations in a yarn within an inch. A yarn with a twist or Twist Multiple of 3 is a yarn that experiences 3 yarn rotations within an inch. As twist values increase, the corresponding yarn diameter of an otherwise identical yarn, decreases, and the yarn density increases. As the yarn density increases, the yarn resistance to scouring increases as well. This is advantageous with the goal being core pollution preservation, but yarn twist is an additional factor when calculating a desirable scour potential. A smaller yarn, such as a 10/1 yarn, may require significantly less scour potential to achieve the desired core preservation when compared to a larger, 6/1 yarn. However, a 10/1 yarn with a twist ratio of 5.3 twists per inch may require a similar scour potential when compared to a 6/1 yarn with a twist multiple of 3.3 twists per inch.
Comparison of EXAMPLES A and B where the yarn diameter was larger than the yarns in EXAMPLE C will further demonstrate this concept. Still the results from EXAMPLE A and EXAMPLE B are nevertheless much improved versus results from conventional dye range scouring practices as shown in
Inventors anticipate that in the processing of scouring two yarns of differing diameters, the smaller diameter yarn would experience scour penetration at a faster rate with a difference being at least equal to the differences between the areas of the two cross sections. In the previous example of the 6.0/1 and 10.0/1 warp yarns, the 10.0/1 yarns have an area 40% less than the 6.0/1 and it is anticipated that the scour penetration to the core would be at least 40% faster as a result. Inventors recognize that yarn diameter is affected by twist which may trade yarn diameters for yarn densities, but hold that the argument is consistent that a cross section with more fibers require a scour that can be understood to be unique when compared to a yarn with fewer fibers when the goal is to achieve proportional levels of scour and dye penetration and/or fastness.
Further the inventors realized that the degree of use of the scouring steps is related to the origin and related properties of the cotton being dyed. Due to environmental impacts such as weather, soil conditions and mineral content, cotton grown in different regions have different properties. Cotton is a cellulose fiber and is formed within a pod. These fibers and seeds are formed with a coating of natural oils, waxes, and other contaminants. Cotton grown in the southern United States of America have an oil, sugar, and wax content that is different than cotton grown in other parts of the world such as India. The cotton grown in China will also have unique oil and wax contents relative to both India and the USA. The same can be said for cotton grown in Pakistan, Brazil, as well as other regions. The oils and waxes coating the fibers make the fibers hydrophobic and consequently resistant to have water soluble dyes absorbed. The varying average qualities of cotton grown in the different regions therefore call for adjustments to more accurately minimize the scour of the particular yarn to provide the white core post dyeing even if those adjustments must be obtained from trial and error and this is another embodiment of our invention.
Scouring of the yarn removes waxes, oils, and other field contaminants which converts the yarn from hydrophobic to hydrophilic. The ability of the scour chemistry treatment and scour process to remove debris, waxes, fats, oils etc from the surface and or inner areas of the yarn (i.e. the circular depth or centrally located area of a yarns cross-section) is the scour potential and can be influenced by a great many variables such as the temperature of the chemistry, the concentration of the caustic chemistry, the immersion time in the caustic chemistry, the dwell time between the immersion in caustic chemistry and the rinse that should follow the scour process, nip pressure and rinse vats. Additional variables can be introduced, but are uncommon practices. An example of such additional variables may be multiple scour boxes, air circulation by fans, or steamed rollers located before, between, or after scour boxes. These additional variables are attempts to further open the yarn, forcing the caustic chemicals to scour the core of the yarn so that each yarn component is removed through effective scour. Each of these methods employed follow the same failed industry wide concept that only completely scoured yarns can be dyed to a dark color which is contradictory to the CleanKore™ technology used to retain a core that is white rather than blue.
Each of these CleanKore™ techniques or practices are contrary to the well-accepted practices found globally in the conventional slasher and rope dye mills used for denim fabric production. However, any one of these inventive concepts change the scouring depth and degree and can result in much improved denim garment washing processes by limiting dye penetration into the white core. Employment of some or all of these contrary practices have a dramatic effect on the denim garment washing process in terms of sustainability, cost savings, water usage, energy, chemical usage, and washing time.
Another embodiment of this invention is the control and typically the reduction in temperatures and distance, and consequently time, between the scouring vat and the rinsing stages. As disclosed above, traditionally yarns are exposed to the scour vat and then are often passed through a series of rollers that are commonly heated. Whereas one inventive goal is only to scour the outer perimeter of the yarn while retaining the dye resistant waxy core with higher density, this embodiment involves the significant reduction in dwell time and/or roller temperatures to varying degrees. The roller temperature may be reduced from about 70° C. to about 30° C. or even lower, such as room temperature. A further embodiment is to reduce dwell time. Dwell time can be understood to be the time spent between two intentional processes. Typically the dwell times between different tanks or vats is determined merely by the distance between the processes, or the rollers that are added in between the processes. With the mindset of challenging conventional methods practiced in the mill, CleanKore™ technology uses dwell time as a variable in one case by rethreading the yarn so as to skip some or all of the rollers between scour and rinse tanks. Reducing the diameter of the rollers, eliminating rollers, reducing heated rollers, or shortening the spans between the rollers involved with dwell time between scour and scour rinsing stages are further embodiments. In one trial, a reduction in dwell time occurred when the number of rollers used for dwell time at this stage was reduced from 6 to 3 which resulted in the dwell time to be reduced from about 60 seconds to about 30 seconds. Reduction in dwell time causes less time for the scour chemicals to work through the yarn before they are rinsed off in the rinse vat and as a result reduce the overall scour potential.
After denim is woven at the denim mill, most of it is sent to garment manufacturing. Garment manufacturing involves cutting, sewing and then both dry processing and garment wash procedures. Dry processing is a generic term for a series of processes that involve no or very little water. Dry processing may involve hand sanding with sandpaper, laser abrasion or other laser pattern treatment, destruction caused by lasers, knives, rotary brushing tools, the application of resin, and bleach rubs as examples. Wet processing typically involves the use of environmentally challenging amounts of water, as well as many chemicals and abrasive substrates. The inventive concepts introduced for the first time in this invention can dramatically reduce wet process costs from about $0.25 to about $1.00 per garment. Reduction in the amount of water, stones, auxiliary chemicals, enzymes, and color reduction agents to wash the jeans to a previously determined standard will be significant and produce new environmental and sustainability benefits the marketplace has never seen before. Reduction in the dry process costs will further decrease overall costs.
Additionally the laser and ozone process would be faster to remove indigo and sulfur color from denim produced from this invention because the laser or ozone would not have to penetrate as far into the core. Early results indicate that the time to laser abrade a pair of denim jeans could roughly be cut in half with these inventive concepts and/or the aesthetics of the laser pattern created could generate a much more convincing replication of authentic manual wear associated with several more expensive manual and chemical processes, such as potassium permanganate spraying and the necessary neutralization of the same. Less manual abrasion by hand sanding, or chemical sprays/rubs also preserves base cotton strength, so the denim garments last longer. Further, inventors realized through confirmation in denim mill plant trials that the disclosed technology can actually eliminate the need for potassium permanganate. Potassium permanganate (PP) is often used as a localized or global bleaching agent and considered necessary within the fashion industry to counter the excessive dye penetration that the denim industry produced. When methods to physically remove indigo to reveal the white core fail, PP is commonly used. PP is not only dangerous to the laborers that apply it, but it involves additional neutralization and wastewater treatment steps that result in millions of gallons of water being used annually around the world for this purpose. In addition, the reaction of PP and indigo produces isatin which rapidly form anthranilic acid which in turn yellows along with the article treated. The inventive embodiments disclosed involve a much shallower ring of dye (indigo or sulfur), which is more consistently and successfully removed via conventional garment abrasion methods. A major benefit of this invention is that when using the laser technology, it can replace potassium permanganate spray (PP spray), which is a very hazardous and industry regulated chemical. PP spray is used to add brightness or whiteness to the abraded area. Laser etching or hand sanding alone cannot achieve the brightness necessary on normal denim fabric. PP spray also requires additional water and strong neutralization chemicals for its removal. However, by using methods disclosed in this invention, it is now possible to replicate the look of PP spray by laser alone. By laser etching on the rigid fabric, it can achieve a similar brightness or whiteness compared to PP spray. For optimal results, laser etching should occur on the washed garment to properly replace PP spray. However, both methods can be used. These results are possible because once the laser penetrates into the dyed warp core, a brightness or whiteness automatically appears, which has a similar look of PP spray. An embodiment therefore is the improvement of the yarn dye characteristics such as retaining a white or whiter core with lessened dye penetration so the laser penetrate the core with the CleanKore™ technology compared to conventional denim fabric. Therefore a key benefit and an embodiment of this invention is the elimination or major reduction in the use of PP spray.
Examples of denim jeans processed with the CleanKore™ technology vs conventional technology (labeled Control) are shown in
The denim mills in the attempt to attain the desirable dark colors on their yarns expend vast amounts of energy and chemicals to maximize the penetration and fastness of dyes. Quite often the primary purpose of both wet and dry processing is to remove, lighten, or otherwise alter these indigo and sulfur dyes applied at the denim mill. The disclosed invention involves a reduction in chemicals and water usage at the mill, as well as a savings in energy costs as the various immersion tanks are heated much less or not at all. Hence, these CleanKore™ inventive concepts surprisingly reduce costs at both the mill and the garment processing laundry.
Traditional methods of scouring and dyeing are focused on opening and penetrating the yarn with dye, but increased yarn penetration results in increased unpredictability. This has resulted in yet another problem with which the industry struggles. Garments made from traditionally dyed cotton denims often undergo extensive wet processing to selectively lighten the shades. The increasingly unpredictable nature of exaggerated yarn penetration of dye results in yarns being dyed with equally exaggerated nonuniformity with regards to shape of the dyed areas in comparison to the shape of the yarns.
One issue with excessive dye penetration is the yarn integrity after dry processing. When indigo penetrates and fixes to the core of the yarn, attempts to remove that indigo involving bleach, hand sanding, and laser require increased exposure of energies and volume of chemicals. These extra forces required to remove the excess indigo result in textile goods with dramatically reduced tear and tensile strength. Lasers are required to run at higher powers and/or slower speeds which increases the surface temperature to a destructive level. CleanKore™ technology with only an outer perimeter of dye requires substantially less laser energy, hand sand energy, and harsh bleaching techniques which result in the retention of a significant amount of the textiles original tear and tensile properties. Less dry process and wash abrasion preserves the base denim strength. This retention of yarn integrity results in a more durable, higher quality product at the consumer level. Also, dry processing can not be used on some fabrics because it reduces tear and tensile strength to the point of being unacceptable. CleanKore technology now allows those fabrics to be treated with dry processing.
One issue with the exaggerated non-uniformity in dye penetration is in dry processing. With a series of yarns that, in close proximity, have vastly different levels of dye penetration, attempts at abrasion with sprayed bleach medium, hand sanding, rotary brushing, laser processing, ozone, or even water jet sprays commonly produce unfavorable results. Some yarns may be abraded in areas that experience 10% dye penetration, and other yarns (or areas of the same yarn) may have dye penetrations as high as 60%. The abrasion process cannot account for changes in dye penetration, so some yarns in particular that are supposed to have 50% color reduction may instead experience 80% color reduction, and other yarns may experience no color change at all. This uneven nature of the indigo or sulfur dye penetration and the need to partially expose the white core of deeply dyed warp yarns results in damage to the tensile and tear strength of the exposed warp yarns, which decreases overall strength and longevity of the denim garments. This limits the amount of fabrics that can be laser etched.
Another embodiment of the disclosed invention is a dye penetration and fastness that is significantly more uniform. This uniformity can be understood to mean that the dye experiences both similar penetration and oxidized fixation in a shape that follows the outer surface outline of a given warp yarn.
This invention is described throughout the document to involve indigo dye, but the embodiments pertain to other dyes as well, including dyes such as sulfurs, other vat dyes, and other dyes. Sulfur dyes may be introduced within the dye range before the indigo. This is commonly referred to as sulfur bottom and when paired with the disclosed invention will provide a largely (>60%) white core. Sulfur dye vats using the disclosed invention are an embodiment and as they use the same sodium hydrosulfide as a reducing agent the conditions are consistent with those disclosed within the invention. Sulfur dyes may be used before the application of indigo dyes. This is known as sulfur bottom, as the sulfur is applied “under” the succeeding indigo dyes. Sulfur dyes may also be used after the application of indigo dyes. This is commonly known as sulfur topping, as the sulfur is “on top” of the indigo. Alternatively, sulfur dyes can be applied between other sulfur dyes, or between indigo dyes, or between indigo and sulfur dyes. The conditions associated with sulfur top applications pertaining to the invention are consistent with those of sulfur bottom, mixed colors, or pure indigo dyeing.
Inventors believe CleanKore™ embodiments to be revolutionary to the textile industry for a host of reasons. Reduced concentrations of chemicals, paired with overall reduced volume of water involved with dyeing provide much needed relief to industrially taxed water systems. Clean water rights will be a growing concern in the world. Immense water requirements are needed to enzyme and stone wash garments. The process of obtaining water has become a huge concern in the textile industry, not only because labor costs rise in garment wash times, but the water needs to be properly cleaned before being returned to the source to avoid serious environmental consequences. The reduction in chemicals, in addition to fewer and more safe chemicals on many Restricted Substance Lists (RSL), involves savings from the logistics of shipping and storing those chemicals. With lessening chemical harshness of the scour comes the added benefit of lower turnover of the water that is involved because of lowered contamination rates, so easier wastewater treatment for effluent OR re-use in other mill processes.
Furthermore, better retention of a white core through embodiments that reduce yarn penetration of the dye greatly reduces dependence on chemical and physical methods to remove color to reveal the white core. Uniformity in the shape of the dyed areas of the yarns greatly improves the aesthetics of the denim resulting in far fewer seconds of fabric and garments. Reduction in dye penetration has significant, up to 50%, beneficial impact on the speed and/or efficiency of the laser systems or hand sanding to create the often intricate wear patterns.
CleanKore™ technology lends many benefits to the textile mill through cost savings in the reduction of chemical consumption, energy savings with lower temperatures in scouring and oxidation stages, and does so while improving the aesthetics and quality of the product in the same production time.
The manufacturers of garments and articles produced save significant overhead and chemical consumption during the wet processing stage with the CleanKore™ technology through massively decreased wash-down times. This frees up large costly washing machines and space and making great strides in reducing environmental impact. Of course the reduced use of water is a key benefit realized with CleanKore™ technology. The time savings alone is substantial as shown in
Still, another significant impact this CleanKore™ technology offers the textile industry may come at the dry processing stage. Dry processing traditionally involves heavy implementation of hand sanding operations. Operators labor to abrade garments manually while loosely following often simplified versions of a designers original pattern. Operator fatigue, repetitive injuries, high employee turnover, inconsistencies between operators, personal protective equipment, health and safety monitoring and the necessity of potassium permanganate spray make hand sanding an expensive necessity.
This CleanKore™ technology, paired with RevoLaze's patented laser technology, will change the manufacturing landscape for the better. For decades, lasers, just as laborers, have struggled with traditional dyeing techniques of textile goods. Excessive dye penetration at the mill requires either excessive labor or laser energy to remove the necessary indigo or sulfur dye to reveal the white core. Often times, garments would receive laser treatment but still require PP spray to lessen the effect of the irregularly shaped core and the color retention involved with it. PP spray has been known for decades to be a health hazard to the long term lung health of the operators required to spray and handle it.
With CleanKore™ technology, lasers can much more effectively, consistently, and precisely remove dye from indigo and sulfur-dyed textiles. This increase in efficacy has the potential to eliminate the dependence on PP spray for selective bleaching and also greatly improves the aesthetics of the achievable patterns. A greater reliance on laser will result in designers realizing their designs, patterns, logos, and textures and improve the overall marketability of denim on the whole. Not since the original introduction of laser to the denim manufacturing world has there been such an exciting and revolutionary opportunity like CleanKore™ for laborer safety, cost savings, flexibility in dry process design, and an improved product desirability to increase sales.
By preserving a larger percentage of the white core and generating a more circular shape of the white core, it allows improved laser quality, consistency and throughput. There is less sizing and that also allows improved laser quality because it can more easily penetrate into the dyed warp yarns. The larger percentage of the white warp core allows the laser to penetrate the core faster and therefore less laser intensity is needed. By having a more circular shape of the white core, when the laser penetrates the core, it will have a much more consistent result throughout the core compared to the standard white core which is more jagged in shape.
Another potential factor that can affect the quality of the white core during scouring is the type of dye range that was used. Typically, denim mills will use two types of dye ranges, a rope range or a slasher range. In the case of a slasher range, the individual yarn remains parallel and passes through the machine in sheet form. Each yarn remains in tension and total tension is uniformly shared by all yarns on the dyeing machine. The tense condition of cotton yarn can restrict liquid penetration towards the core more so compared to a rope range. The tension condition of the yarn results in elongation.
While in the case of a rope range, the yarn passes through the machine in bunch form. There is no individual yarn tension. Also, in one rope each yarn has a different tension and it does not remain consistent as the yarn passes through the machine. The slack condition of yarn results in yarn contraction.
The caustic treatment in such state of yarn creates a different level of swelling of the cellulose fiber. The tense condition allows fiber to swell not to the full extent while slack fiber swells to fullest extent. The amorphous region in the fiber opens up more and the sodium molecule acquires maximum space. The cross section development of each fiber of one yarn is different in slasher treated yarn while the cross section remains same for all fiber of one yarn in rope treatment.
In both cases the chemical starts penetration to the yarn from the outer layer. In case of a rope range, all the yarns of one rope and all ropes on the machine behaves similar in terms of penetration of dyes and chemicals. The penetration levels can be higher in a rope range compared to a slasher range. The dye penetrates in diffused form and concentration gradually reduces from the top layer to the core of the yarn. While in case of a slasher range, the dye penetration may not be as severe. Therefore, the optimal parameters may differ depending on a slasher range or rope range. Nevertheless, the inventors found excellent results on both Slasher and Rope ranges.
The adjustments to the scour parameters, especially utilizing some or all six of the techniques disclosed above are necessary to achieve the appropriate results. If the scour parameters are not adjusted implementing one or more of the disclosed embodiments above, it will be very difficult to achieve a large percentage of the white core post dyeing. The scour step is one of the first steps in the dye range, and if lack of scouring is not present, the impacts of over-scouring cannot be reversed to achieve the appropriate amount of white core post dyeing. If the scour parameters are properly adjusted with some or all of the embodiments disclosed above, then a large percentage of the white core will be possible. If the percentage of white core is too large or not large enough, then changes to some or all of the six techniques can be made. That's why it is so important to be able to employ some or all of the embodiments disclosed. Depending upon the yarn diameter and other factors, some companies may want the maximum white core that still achieves the necessary fastness and other companies may want slightly more dye penetration but with a white core. Changes can be made to the scour parameters to achieve both results. This invention uniquely and for the very first time discloses the absolute importance of controlling scouring process parameters as the most critical aspect of achieving a white core post dyeing. By adopting some or all of the embodiments disclosed, the thickness of the white core can now be controlled.
CleanKore™ uniquely answers the denim industry's cry for major denim garment cost reduction coupled to significant improvement to sustainability—an achievement not before realized for reasons cited in the opening paragraph of this specification.
This application claims priority from Provisional Application No. 62/897,853, filed Sep. 9, 2019, the entire contents of which are herewith incorporated by reference
| Number | Date | Country | |
|---|---|---|---|
| 62897853 | Sep 2019 | US |
