Patent Grant
11702794
The present invention relates to textiles and, more specifically, to materials and fabrics and their manufacture, in which the materials and fabrics will have enhanced response characteristics for laser finishing, especially for denim and denim apparel including jeans, shirts, shorts, jackets, vests, and skirts, to obtain a faded, distressed, washed, or worn finish or appearance.
1853, during the California Gold Rush, Levi Strauss, a 24-year-old German immigrant, left New York for San Francisco with a small supply of dry goods with the intention of opening a branch of his brother's New York dry goods business. Shortly after arriving in San Francisco, Mr. Strauss realized that the miners and prospectors (called the “forty niners”) needed pants strong enough to last through the hard work conditions they endured. So, Mr. Strauss developed the now familiar jeans which he sold to the miners. The company he founded, Levi Strauss & Co., still sells jeans and is the most widely known jeans brand in the world. Levi's is a trademark of Levi Strauss & Co.
Though jeans at the time of the Gold Rush were used as work clothes, jeans have evolved to be fashionably worn everyday by men and women, showing up on billboards, television commercials, and fashion runways. Fashion is one of the largest consumer industries in the U.S. and around the world. Jeans and related apparel are a significant segment of the industry.
As fashion, people are concerned with the appearance of their jeans. Many people desire a faded or worn blue jeans look. In the past, jeans became faded or distressed through normal wash and wear. The apparel industry recognized people's desire for the worn blue jeans look and began producing jeans and apparel with different wear patterns. The wear patterns have become part of the jeans style and fashion. Some examples of wear patterns include combs or honeycombs, whiskers, stacks, and train tracks.
Despite the widespread success jeans have enjoyed, the process to produce modern jeans with wear patterns takes processing time, has relatively high processing cost, and is resource intensive. A typical process to produce jeans uses significant amounts of water, chemicals (e.g., bleaching or oxidizing agents), ozone, enzymes, and pumice stone. For example, it may take from about 20 to 60 liters of water to finish each pair of jeans.
Therefore, there is a need for an improved materials and fabrics for laser finishing of jeans and other apparel that reduces environmental impact, processing time, and processing costs, while maintaining the look and style of traditional finishing techniques.
A fabric has enhanced response characteristics for laser finishing. The fabric can be denim for denim apparel such as jeans. Software and lasers are used to finish apparel made of the fabric to produce a desired wear or distressing pattern or other design. The fabric allows for relatively fast color change in response to the laser, color changes in hue from indigo blue to white, many grayscale levels, and maintains strength and stretch properties. A method used to make the fabric includes spinning, dyeing, and weaving yarns in such a way to obtain the desired enhanced response characteristics for laser finishing.
In an implementation, a method includes: processing a cotton yarn using an indigo dye to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, 10 percent (e.g., from about 7.5 percent to about 12.5 percent) of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye; and weaving the dyed cotton yarn into a denim fabric, where the warp yarns include dyed cotton and the weft yarns include undyed cotton, and the denim fabric is to be finished by exposing the dyed cotton yarn to a laser.
When exposed to the laser, the laser creates a finishing pattern on a surface of the garment based on a laser input file provided to the laser. The laser input file includes a laser exposure values for different laser pixel location. For each laser exposure value, the laser removes a depth or thickness of material from the surface of the denim material that corresponds to the laser exposure value.
For lighter pixel locations of the finishing pattern, a greater depth of the indigo ring-dyed cotton yarn is removed, revealing a greater width of an inner core of the dyed yarn, as compared to darker pixel locations of the finishing pattern, where a lesser depth of the indigo ring-dyed cotton yarn is removed, revealing a lesser width of an inner core of the dyed yarn.
In another implementation, a method includes: A garment made from fabric panels of a denim material is provided. The fabric panels are sewn together using thread. The denim material will be finished by using a laser to remove selected amounts of material from a surface of the denim material at selected locations of the garment.
The denim material includes an indigo ring-dyed cotton yarn having cross section having an outer ring and an inner core. A cross-sectional profile of the outer ring relative to the inner core is compatible with the laser to obtain at least 32 different grayscale levels or at least 64 different grayscale levels. For the cross-sectional profile, a thickness of the outer ring that is, for example, about 10 percent (e.g., from about 7.5 percent to about 12.5 percent) of a total thickness of the yarn.
The outer ring is indigo colored due to being penetrated through by an indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye. The indigo ring-dyed cotton yarn with laser-compatible cross-sectional profile is obtained by a dyeing process.
The process can include: mercerizing an undyed yarn in an alkaline solution to obtain an mercerized undyed yarn; immersing the mercerized undyed yarn into at least one indigo dye solution having a pH in a range, for example, from about 10.7 to about 12.0; and exposing the garment to a laser to create a finishing pattern on a surface of the garment based on a laser input file provided to the laser. The laser input file has laser exposure values, each for a different laser pixel location.
For each laser exposure value, the laser will remove a depth of material from the surface of the garment that corresponds to the laser exposure value. Tor lighter pixel locations of the finishing pattern, a greater depth of the indigo ring-dyed cotton yarn is removed as compared to darker pixel locations of the finishing pattern, where a lesser depth of the indigo ring-dyed cotton yarn is removed.
Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures.
Some examples of natural fibers include cotton, flax, hemp, sisal, jute, kenaf, and coconut; fibers from animal sources include silk, wool, cashmere, and mohair. Some examples of synthetic fibers include polyester, nylon, spandex or elastane, and other polymers. Some examples of semisynthetic fibers include rayon, viscose, modal, and lyocell, which are made from a regenerated cellulose fiber. A fabric can be a natural fiber alone (e.g., cotton), a synthetic fiber alone (e.g., polyester alone), a blend of natural and synthetic fibers (e.g., cotton and polyester blend, or cotton and spandax), or a blend of natural and semisynthetic fibers, or any combination of these or other fibers.
For jeans, the fabric is typically a denim, which is a sturdy cotton warp-faced textile in which a weft passes under two or more warp threads. This twill weaving produces a diagonal ribbing. The yarns (e.g., warp yarns) are dyed using an indigo or blue dye, which is characteristic of blue jeans.
Although this patent describes the apparel processing and finishing with respect to jeans, the invention is not limited jeans or denim products, such as shirts, shorts, jackets, vests, and skirts. The techniques and approaches described are applicable to other apparel and products, including nondenim products and products made from knit materials. Some examples include T-shirts, sweaters, coats, sweatshirts (e.g., hoodies), casual wear, athletic wear, outerwear, dresses, evening wear, sleepwear, loungewear, underwear, socks, bags, backpacks, uniforms, umbrellas, swimwear, bed sheets, scarves, and many others.
A manufacturer creates a design 115 (design I) of its product. The design can be for a particular type of clothing or garment (e.g., men's or women's jean, or jacket), sizing of the garment (e.g., small, medium, or large, or waist size and inseam length), or other design feature. The design can be specified by a pattern or cut used to form pieces of the pattern. A fabric is selected and patterned and cut 118 based on the design. The pattern pieces are assembled together 121 into the garment, typically by sewing, but can be joined together using other techniques (e.g., rivets, buttons, zipper, hoop and loop, adhesives, or other techniques and structures to join fabrics and materials together).
Some garments can be complete after assembly and ready for sale. However, other garments are unfinished 122 and have additional laser finishing 124. The finishing may include tinting, washing, softening, and fixing. For distressed denim products, the finishing can include using a laser to produce a wear pattern according to a design 127 (design II). Some additional details of laser finishing are described in U.S. patent application 62/377,447, filed Aug. 19, 2016, which is incorporated by reference. U.S. patent application Ser. Nos. 15/841,267, 15/841,268, 15/841,271, and 15/841,272, filed Dec. 13, 2017; Ser. No. 15/682,507, filed Aug. 21, 2017; and 62/433,746, filed Dec. 13, 2016, are also incorporated by reference.
Design 127 is for postassembly aspects of a garment while design 115 is for preassembly aspects of a garment. After finishing, a finished product 130 is complete and ready for sale. The finished product is inventoried and distributed 133, delivered to stores 136, and sold to consumers or customers 139. The consumer can buy and wear worn blue jeans without having to wear out the jeans themselves, which usually takes significant time and effort.
Traditionally, to produce distressed denim products, finishing techniques include dry abrasion, wet processing, oxidation, or other techniques, or combinations of these, to accelerate wear of the material in order to produce a desired wear pattern. Dry abrasion can include sandblasting or using sandpaper. For example, some portions or localized areas of the fabric are sanded to abrade the fabric surface. Wet processing can include washing in water, washing with oxidizers (e.g., bleach, peroxide, ozone, or potassium permanganate), spraying with oxidizers, washing with abrasives (e.g., pumice, stone, or grit).
These traditional finishing approaches take time, incur expense, and impact the environment by utilizing resources and producing waste. It is desirable to reduce water and chemical usage, which can include eliminating the use agents such as potassium permanganate and pumice. An alternative to these traditional finishing approaches is laser finishing.
Denim fabric is typically made from cotton, which is a plant-based cellulose fiber. There are many different varieties of cotton including upland cotton and long staple cotton, also know as Pima cotton. Upland cotton has fiber lengths from about 13 to 35 millimeters, while long staple cotton have fiber lengths from about 25 to 65 millimeters. The fiber length for denim is generally about 28 millimeters or greater. Denim is often made from upland cotton, but may be from other varieties or a blend of different varieties of cotton.
A cotton picker machine picks the cotton bolls from the cotton plant. The cotton bolls are the fruit of the cotton plant and include lint and cotton seeds. The cotton fibers twist and spiral together. A cotton gin separates the lint from the cotton seeds and other debris, which are discarded and used for other purposes (e.g., extracting cottonseed oil). Cotton is generally a white or off-white color. The cotton fiber is hollow, allowing the fiber to absorb moisture—making cotton warm in the winter and cool in the summer.
Fiber 106 can be 100 percent cotton fiber. Or fiber 106 can be a blend, including cotton and other noncotton fibers to modify the characteristics of the fabric. For example, spandex, elastane, or other elastic polyurethane fiber can be blended with the cotton fibers to give the denim a stretch characteristic.
By spinning 211 the fiber, an undyed yarn 214 is obtained. During spinning, cotton staple fibers or a blend of cotton and other fibers are twisted together to form a continuous spun yarn. Depending on the specific spinning process, a diameter and number of twists in the yarn can vary. The undyed yarn is the same color as the cotton fiber, white or off white.
Spinning can be by, for example, ring spinning, rotor spinning, or other spinning technique. Another spinning technique is core spinning, where a fiber (e.g., staple fiber) is wound around a core of another material, such as polyester or elastane. Core spinning can be used to be used create stretch denim material.
After spinning and before dyeing, the yarn can be mercerized 218 to obtain a mercerized yarn 223. Mercerization can also be performed after weaving. When performed on the undyed yarn, the mercerization can be referred to as premercerization. When performed on the fabric, the mercerization can be referred to as fabric mercerization. Mercerization is optional and yarns and fabrics are not necessarily mercerized. If used, mercerization is usually done only once in the process, either yarn premercerization or fabric mercerization.
Mercerization strengthens the yarn and gives the yarn a more lustrous appearance. Mercerization alters the chemical structure of the cotton fiber. Mercerizing results in the swelling of the cell wall of the cotton fiber. This causes an increase in the surface area and reflectance, and gives the fiber a softer feel. In an implementation, for premercerization, the yarn is treated in a sodium hydroxide bath (or other chemical, typically highly alkaline solution, that causes the fibers to swell). This is followed with an acid bath that neutralizes the sodium hydroxide.
After spinning and optionally mercerization, a dyeing process 227 in which the yarn is dyed. For blue denim, the undyed yarn is dyed using an indigo dye to obtain a dyed yarn 230, which will be indigo blue. The dyed yarn is woven 243 to obtain a woven fabric 246, which can be further finished by fabric finishing 259. Fabric finishing may include, for example, preshrinking. This results in laser-sensitive finished fabric 112.
For dyeing, a pH of the reduced indigo solution can be a range from about 10.5 to about 13, which is a basic solution. In chemistry, pH is a numeric scale that specifies an acidity or basicity (or alkalinity) of an aqueous solution in which 7 is considered neutral. Water has a pH of 7. A pH value is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity in a solution. Solutions having pH greater than 7 would be consider basic, while solutions with pH less than 7 would be consider acidic. A usual range for pH is from 0 to 14, but the pH value can be below 0 or above 14. The pH is a relative value: The higher the pH indicates the greater the basicity or less the acidity of a solution. The lower the pH indicates the less the basicity or greater the acidity of a solution.
An indigo dyeing process can include, optionally, a sulfur bottoming 306 before dyeing with indigo. For sulfur bottoming, the yarn is first dyed using a sulfur dye or sulfur dyestuff. Often the sulfur dye is black or gray, but can be other colors. Generally sulfur bottoming is used to give yarn a particular color cast. Sulfur bottoming is optional and can be omitted from the dyeing process.
Indigo dyeing occurs by dipping 310 or immersing yarn into a vat with the reduced indigo dye. The color of the reduced indigo dye solution is not indigo or blue, but rather greenish or yellowish-green in color. When a white yarn is dipped into and removed from a vat with reduced indigo dye, the yarn will be yellowish-green in color. However, by exposure to oxygen in the air, the indigo oxidizes 315, and slowly over time, the yellowish-green yarn will turn the familiar blue color associated indigo. The blue color is caused by chromophores trapped in the fabric which reflect light as a blue color. The blue color of indigo has a wavelength between about 420 to 465 nanometers.
The dye dipping and oxidizing steps can be repeated multiple times 319, such as 2, 3, 4, 5, 6, 7, 8, 12, or more times. Multiple dips can be used to obtain deeper shades of blue. With each dip, the dye penetrates (e.g., migrates or diffuses) more toward a center or core of the yarn, rather than staying on the surface or close to the surface of the yarn.
After indigo dyeing is completed, the process can include, optionally, a sulfur topping topping 324. Sulfur topping is similar to sulfur bottoming, but sulfur topping occurs after indigo dyeing instead of before. Sulfur topping is optional and can be omitted from the dyeing process.
In an implementation, the dyeing process includes sulfur bottoming, indigo dyeing, and sulfur topping. In an implementation, the sulfur bottoming and sulfur topping are not used, and the yarn will be dyed using only indigo. Another implementation includes sulfur bottoming and indigo dyeing, and not sulfur topping. Another implementation includes indigo dyeing and sulfur topping, and not sulfur bottoming.
It should be understood that the invention is not limited to the specific flows and steps presented. A flow of the invention may have additional steps (not necessarily described in this patent), different steps which replace some of the steps presented, fewer steps or a subset of the steps presented, or steps in a different order than presented, or any combination of these. Further, the steps in other implementations of the invention may not be exactly the same as the steps presented and may be modified or altered as appropriate for a particular application or based on the data or situation.
The boxes or vats 412 for the dye range are typically housed on one floor (e.g., first floor or basement) a building. The dye range has a skyer mechanism 416 with extends through the ceiling of the floor with boxes into upper floors of the building, such as the second and third floors, or higher floors. For example, for a three floor unit, where each floor is about 12 feet, the skyer unit can extend into the air at least 24 feet.
During operation, undyed yarn 214 is conducted or transported via rollers, pulleys, and other mechanisms and pathways through the various boxes (e.g., vat 1, vat 2, and vat 3) to dip the yarn into the solutions within the boxes. The solutions in the boxes can be for sulfur bottoming (optional), indigo dip in a reduced indigo solution, and sulfur topping (optional). Between dips, the yarn is conducted via the skyer above the boxes or vats (or urns or vessels), which exposes the yarn to oxygen so it can oxidize and the indigo can turn blue. At the end of the process, dyed yarn 220 is obtained.
There are different types of dyeing including rope dyeing, slasher dying, and loop dyeing, and any of these can be used in producing a fabric enhanced for laser finishing. For rope dyeing, threads of yarn are initially twisted into a rope, and then undergo a repetitive sequence of dipping and oxidization. The more frequent the dipping and oxidizing, the stronger the indigo shade.
For slasher dyeing, individual yarns are dyed. Warp yarns are repeatedly passed in warp beam form through several baths of indigo dye before being sized and wound for weaving. Loop dyeing involves pulling ropes of yarn through a vat of indigo dye then out up onto the roof of the factory, allowing the yarn time to oxidize before returning to the dye bath.
For denim, dyed yarn 220 is used for the warp, and undyed or white yarn is typically used for the weft yarn. In some denim fabrics, the weft yarn can be dyed and have a color other than white, such as red. In the denim weave, the weft passes under two or more warp threads.
Because of the weave, one side of the fabric exposes more of the warp yarns (e.g., warp-faced side), while the other side exposes more of the weft yarns (e.g., weft-faced side). When the warp yarns are blue and weft yarns are white, a result of the weave is the warp-faced side will appear mostly blue while the reverse side, weft-faced side, will appear mostly white.
In denim, the warp is typically 100 percent cotton. But some warp yarns can be a blend with, for example, elastane to allow for warp stretch. And some yarns for other fabrics may contain other fibers, such as polyester or elastane as examples. Although denim is described as an example, the techniques in this patent can apply to other materials including twills, materials in other weaves (other than twill), cotton twill, blended twills, blended materials, jersey knits, and many others.
The yarn has a diameter 622, the ring dyed portion has a thickness 626, and the core has a diameter 629. An area of the yarn, A(yarn), is Pi*(D622/2){circumflex over ( )}2, where Pi a mathematical constant, the ratio of a circle's circumference to its diameter, approximated as 3.14159, D622 is diameter 622, and {circumflex over ( )}2 indicates the quantity in parenthesis to the power 2 or squared. An area of the core, A(core), is Pi*(D612/2){circumflex over ( )}2, where D612 is diameter 612. The area of the ring dyed portion is A(yarn) minus A(core).
To simplify the diagram,
Ring dyeing is often considered undesirable since the dye is not evenly been distributed through the yarn. However, for laser finishing, ring-dyed yarn can improve a fabric's response characteristics to the laser. Fabric with ring-dyed yarn has an improved grayscale resolution, allowing the laser to obtain a greater number of gray levels that are visually distinguishable from each other.
The computer can control a positioning mechanism 726 to position the laser to print, for example, a distressing pattern or any other pattern onto the garment. For example, the laser can print the pattern row by row (or column by column). Also, the laser can make multiple passes across one or more rows (or columns). Multiple passes can be used to further increase or enhance grayscale resolution. Also laser passes may be made between rows (e.g., half or quarter rows), which can increase pixel resolution.
Laser finishing is a technique that includes the use of a laser. A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. Lasers are used for bar code scanning, medical procedures such as corrective eye surgery, and industrial applications such as welding. A particular type of laser for finishing apparel is a carbon dioxide laser, which emits a beam of infrared radiation.
The laser can be controlled by an input file and control software to emit a laser beam onto fabric at a particular position or location at a specific power level for a specific amount of time. Further, the power of the laser beam can be varied according to a waveform such as a pulse wave with a particular frequency, period, pulse width, or other characteristic. Some aspects of the laser that can be controlled include the duty cycle, frequency, marking or burning speed, and other parameters.
The duty cycle is a percentage of laser emission time. Some examples of duty cycle percentages include 40, 45, 50, 55, 60, 80, and 100 percent. The frequency is the laser pulse frequency. A low frequency might be, for example, 5 kilohertz, while a high frequency might be, for example, 25 kilohertz. Generally, lower frequencies will have higher surface penetration than high frequencies, which has less surface penetration.
The laser acts like a printer and “prints,” “marks,” or “burns” a wear pattern (specified by, for example, an input file) onto the garment. The fabric that is exposed to the infrared beam changes color, lightening the fabric at a specified position by a certain amount based on the laser power, time of exposure, and waveform used. The laser continues from position to position until the wear pattern is completely printed on the garment.
In a specific implementation, the laser has a resolution of about 34 dots per inch (dpi), which on the garment is about 0.7 millimeters per pixel. The technique described in this patent is not dependent on the laser's resolution, and will work with lasers that have more or less resolution than 34 dots per inch. For example, the laser can have a resolution of 10, 15, 20, 25, 30, 40, 50, 60, 72, 80, 96, 100, 120, 150, 200, 300, or 600 dots per inch, or more or less than any of these or other values. Typically, the greater the resolution, the finer the features that can be printed on the garment in a single pass. By using multiple passes (e.g., 2, 3, 4, 5, or more passes) with the laser, the effective resolution can be increased. In an implementation, multiple laser passes are used.
A system of laser finishing can include a computer to control or monitor operation, or both.
Further, a system for manufacturing a fabric with enhanced response characteristics for laser finishing can also include a computer to control or monitor operation, or both.
Mass storage devices 817 may include mass disk drives, floppy disks, magnetic disks, optical disks, magneto-optical disks, fixed disks, hard disks, CD-ROMs, recordable CDs, DVDs, recordable DVDs (e.g., DVD-R, DVD+R, DVD-RW, DVD+RW, HD-DVD, or Blu-ray Disc), flash and other nonvolatile solid-state storage (e.g., USB flash drive or solid state drive (SSD)), battery-backed-up volatile memory, tape storage, reader, and other similar media, and combinations of these.
A computer-implemented or computer-executable version or computer program product of the invention may be embodied using, stored on, or associated with computer-readable medium. A computer-readable medium may include any medium that participates in providing instructions to one or more processors for execution. Such a medium may take many forms including, but not limited to, nonvolatile, volatile, and transmission media. Nonvolatile media includes, for example, flash memory, or optical or magnetic disks. Volatile media includes static or dynamic memory, such as cache memory or RAM. Transmission media includes coaxial cables, copper wire, fiber optic lines, and wires arranged in a bus. Transmission media can also take the form of electromagnetic, radio frequency, acoustic, or light waves, such as those generated during radio wave and infrared data communications.
For example, a binary, machine-executable version, of the software of the present invention may be stored or reside in RAM or cache memory, or on mass storage device 817. The source code of the software of the present invention may also be stored or reside on mass storage device 817 (e.g., hard disk, magnetic disk, tape, or CD-ROM). As a further example, code of the invention may be transmitted via wires, radio waves, or through a network such as the Internet.
The processor may be a dual core or multicore processor, where there are multiple processor cores on a single integrated circuit. The system may also be part of a distributed computing environment. In a distributed computing environment, individual computing systems are connected to a network and are available to lend computing resources to another system in the network as needed. The network may be an internal Ethernet network, Internet, or other network.
Arrows such as 922 represent the system bus architecture of computer system 801. However, these arrows are illustrative of any interconnection scheme serving to link the subsystems. For example, speaker 920 could be connected to the other subsystems through a port or have an internal connection to central processor 902. Computer system 801 shown in
Computer software products may be written in any of various suitable programming languages, such as C, C++, C#, Pascal, Fortran, Perl, Matlab, SAS, SPSS, JavaScript, AJAX, Java, Python, Erlang, and Ruby on Rails. The computer software product may be an independent application with data input and data display modules. Alternatively, the computer software products may be classes that may be instantiated as distributed objects. The computer software products may also be component software such as Java Beans (from Oracle Corporation) or Enterprise Java Beans (EJB from Oracle Corporation).
An operating system for the system may be one of the Microsoft Windows® family of operating systems (e.g., Windows 95, 98, Me, Windows NT, Windows 2000, Windows XP, Windows XP x64 Edition, Windows Vista, Windows 7, Windows 8, Windows 10, Windows CE, Windows Mobile, Windows RT), Symbian OS, Tizen, Linux, HP-UX, UNIX, Sun OS, Solaris, Mac OS X, Apple iOS, Android, Alpha OS, AIX, IRIX32, or IRIX64. Other operating systems may be used. Microsoft Windows is a trademark of Microsoft Corporation. Other operating systems may be used. A computer in a distributed computing environment may use a different operating system from other computers.
Any trademarks or service marks used in this patent are property of their respective owner. Any company, product, or service names in this patent are for identification purposes only. Use of these names, logos, and brands does not imply endorsement.
Furthermore, the computer may be connected to a network and may interface to other computers using this network. For example, each computer in the network may perform part of the task of the many series of steps of the invention in parallel. Furthermore, the network may be an intranet, internet, or the Internet, among others. The network may be a wired network (e.g., using copper), telephone network, packet network, an optical network (e.g., using optical fiber), or a wireless network, or any combination of these. For example, data and other information may be passed between the computer and components (or steps) of a system of the invention using a wireless network using a protocol such as Wi-Fi (IEEE standards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11i, 802.11n, 802.11ac, and 802.11ad, just to name a few examples), near field communication (NFC), radio-frequency identification (RFID), mobile or cellular wireless (e.g., 2G, 3G, 4G, 3GPP LTE, WiMAX, LTE, LTE Advanced, Flash-OFDM, HIPERMAN, iBurst, EDGE Evolution, UMTS, UMTS-TDD, 1×RDD, and EV-DO). For example, signals from a computer may be transferred, at least in part, wirelessly to components or other computers.
Further, the diameter of lasers beam can be adjusted or changed. The focal distance between the lens and the fabric may also be adjusted to keep the laser focused. In a specific laser finishing system, the laser is set to allow it to reach a size of an entire pair of pants from top (e.g., waistband) to bottom (e.g., leg opening ends); at that focal distance, the resolution for the laser is 1 millimeter. The resolution can be increased, but then the laser will need to be moved closer to the fabric, and the laser would not reach a typical pair of pants, top to bottom.
The laser system has a scan speed, which is also known as a pixel time or exposure time setting. This is the amount of time the laser spends at each pixel. As an example, a black pixel (which prints as “white” on the denim) of “0” is 100 percent of the pixel time, and each fading grey is a percentage of that pixel time. So a very light file (e.g., less highlighting) will move more quickly across a garment than a more intense one. When using an enhanced laser-sensitive fabric, less time and energy is needed to create the pattern. In an implementation, when the laser power level or intensity is fixed, the exposure time is used to determine the energy a pixel of the apparel is exposed to.
In another implementation, the exposure time is fixed, and the laser power level or intensity is adjustable or variable to determine the energy at a pixel of the apparel is exposed to. In another implementation, the laser power level and exposure time are both variable to determine the energy at a pixel of the apparel is exposed to.
If
In a specific implementation of ring dyed yarn, the ring dye thickness or depth penetrates no more than about 10 percent of the yarn thickness, from all surfaces (or sides). So, about 20 percent of the total diameter is dyed, and the core is 80 percent of the diameter.
Further, due to process variations, the total ring dye thickness (including both sides) can vary, such as 20 percent plus or minus 10, 15, 20, 25, or even up to 50 percent in some instances. So, the ranges can be from about 18 to 22 percent, about 17 to 23 percent, about 16 to 24 percent, about 15 to 25 percent, or up to about 10 to 30 percent. The ring dye thickness for a single side would about half of these values. More specifically, the range for a single-side ring dye thickness would be about 9 to 11 percent, about 8.5 to 11.5 percent, about 8 to 12 percent, about 7.5 to 12.5 percent, or up to about 5 to 15 percent.
As an example, in an implementation, for greater highlights from laser finishing, the total ring-depth depth (which includes thicknesses of both sides of the outer ring) should be from about 15 percent to about 25 percent of the yarn thickness or diameter. When less than 15 percent, the ring dye can wash down too fast, and there not enough colored material for the laser to work with. With more than 25 percent ring-dye is not responsive to provide as large a number of grayscale levels (e.g., not able to provide 64 or more different levels, 128 or more different levels, or 256 or more different levels). Therefore, for a single side, the outer ring thickness can be from about 7.5 percent (e.g., 15 percent divided by 2) to about 12.5 percent (e.g., 25 percent divided by 2).
As a result of the process of making a fabric, a fabric has response characteristics for laser finishing. It is desirable that the fabric have the following good or strong performance characteristics including: (i) fast or relatively fast color change with minimal laser irradiation, (ii) color changes to a hue close to white (e.g., 64 or more grayscale levels, 128 grayscale levels, or 256 or more grayscale levels), and (iii) minimal degradation to strength or stretch properties, or any combination of these. It is undesirable that the fabric have the following poor performance characteristics such as: (i) slow color change, (ii) color changes to a color with noticeable hue, such as grey, blue, or green, instead of white or (iii) unacceptable degradation to strength or stretch properties, or any combination of these.
A fabric with good characteristics for laser finishing has yarns with undyed core fibers (white fibers) closer to their surfaces. A process is to manufacture yarns and this fabric can include one or more of the following techniques, in any combination:
1. Lower pH. Lowering the pH reduces indigo dye affinity to the yarn fiber, reducing penetration. In a specific implementation, the pH of the indigo dye solutions used in the dyeing process are about 11.6 or less, 11.5 or less, 11.4 or less, 11.3 or less, 11.2 or less, or 11.1 or less. In an implementation, the pH will be in a range from about 10.7 to 11.2. By maintaining pH at these levels, the dye yarn will exhibit the ring dye effect.
2. Premercerization. Swelling of fibers makes indigo dye penetration more difficult, reducing ring-dye depth. When the yarns have been premercerization, the pH can be increased slightly and the yarn will still have a desired ring dye. For example, with premercerization, the pH of the indigo dye solution can be increased to 11.2, rather than using 10.7 or 10.8.
3. Lower dye concentration, faster dyeing speed, number of dips, lower temperatures, or any combination of these. If shade matching is not important, a technique reduces opportunity for dye penetration. For example, the dye concentration can be in a range from, for example, about 1.0 to 1.05 grams per liter. In other implementations, the range can extend up to 3 grams per liter.
For dips, there can be, for example, about 8 dye dips. In other implementations, there can be 8 or fewer dye dips, such as 2, 3, 4, 5, 6, or 7. There can be 6 or fewer dye dips. In other implementations, there can be more than 8 dye dips, such as 9, 10, 11, 12, or more than 12 dye dips. With more dips, a lower dye concentration (or adjustment in other parameter) can be used to obtain the same shading and core diameter. With fewer dips, a higher dye concentration (or adjustment in other parameter) can be used to obtain the same shading and core diameter.
All the dips can be in indigo dye baths, such as 8 indigo dye dips. However, not all the dips are necessarily indigo dips. There may be a single dip in black or brown to obtain a particular desired shade of indigo. For example, there can be 10 indigo dye dips and 1 black or brown dye dip (or other color). There can be 9 indigo dye dips and 1 black or brown dye dip (or other color). There can be 8 indigo dye dips and 1 black or brown dye dip (or other color). There can be 6 indigo dye dips and 1 black or brown dye dip (or other color). There can be 5 indigo dye dips and 1 black or brown dye dip (or other color). There can be 4 indigo dye dips and 1 black or brown dye dip (or other color).
Alternatively, or in combination with lower dye concentration, there can be faster speed indigo dips in the indigo, or reduce time of yarn in indigo dips. The machine speed of the dye range can be, for example, about 25 meters per minute. The machine speed of the dye range can exceed 25 meters per minute, which will decrease the dye dip time. In other implementations, the machine speed can be less than 25 meters per minute, and other parameters such as the dye concentration can be used to obtain the same shading and core diameter. In other implementations, the machine speed can be greater than 28 meters per minute. In other implementations, the machine speed can be greater than 30 meters per minute.
Lower temperatures reduce diffusion rate, and thus the ring dye effect will be enhanced and more controllable at lower temperatures. The vats or dye boxes typically have a temperature controller to control heating of the indigo solution. A temperature of the indigo solution is typically room temperature (e.g., 20 degrees Celsius) or above. In an implementation, the temperature range of the indigo solution is from about 20 degrees Celsius to about 30 degrees Celsius. For example, the temperature can be 30 degrees Celsius or below. In an implementation, the temperature range of the indigo solution is from about 30 degrees Celsius to about 40 degrees Celsius. For example, the temperature can be 40 degrees Celsius or below. In an implementation, the temperature range of the indigo solution is from about 40 degrees Celsius to about 50 degrees Celsius. For example, the temperature can be 50 degrees Celsius or below. In an implementation, the temperature range of the indigo solution is from about 50 degrees Celsius to about 60 degrees Celsius. For example, the temperature can be 60 degrees Celsius or below. In an implementation, the temperature range of the indigo solution is from about 60 degrees Celsius to about 70 degrees Celsius. For example, the temperature can be 70 degrees Celsius or below. For example, the temperature can be 80 degrees Celsius or below. For example, the temperature can be 90 degrees Celsius or below. Various other parameters, such as dye concentration or number of dips, can be adjusted to compensate for higher or lower temperatures.
4. Higher yarn twist. High yarn twist makes dye penetration more difficult, reducing ring-dye depth. For example, yarns for denim are twisted in a range between 4.2 and 4.8 twists per inch or TPI. TPI refers to the number of twist spirals in an inch of yarn. Generally, anything 4.6 or above would be considered a higher twist yarn. For some shrink-to-fit products, yarn twist can be about 4.8 twists per inch.
5. Coarse yarn count. Ring-dye depth is a lower percentage of the total yarn diameter, leaving a large undyed yarn core. More fibers remain for improved tear or tensile properties. For equivalent bath concentrations and warp ends, ratio of dye to fiber mass in bath is lower. Fine yarns are at risk of becoming dyed to the center, leaving no undyed fibers to provide color change and highlight.
For fine yarns, dye penetration makes up a larger percentage of total yarn diameter, leaving only a small white core, meaning the ratio of blue to white fibers is higher. This causes the highlight to appear bluish rather than white. Fine yarns are also more at risk for physical failure before highlight is achieved due to removal of a larger percentage of total fiber.
6. Reduce, minimize, or eliminate sulfur bottoming. Due to the affinity of sulfur dyestuff to cotton, sulfur dyes penetrate to the yarn core, dyeing the once-white core fibers. The fabric will now highlight to the color of the sulfur bottom. A small amount of sulfur may be acceptable if the core fibers are dyed to a negligible color change. If sulfur bottoming is desired, a dark indigo dye can create the illusion of bright highlights via contrast against base shade.
7. Sulfur topping. Sulfur topping is less risky than bottoming because many dye-sites are already occupied by indigo, and loose indigo slows penetration of sulfur into yarn. However, sulfur topping still contributes to the total dye quantity; high concentrations can still lead to poor performance, particularly with fine yarns.
8. Reduce or minimize elastane fibers in warp. Some warp-stretch fabrics may show poor performance because the elastane core is clear rather than white. This would mean the “target” for a white highlight is doughnut shaped yarn core, which is a more difficult target to hit, particularly in finer yarn counts. Stronger performing warp-stretch fabrics should have both a shallow ring-dye and a large yarn diameter.
Some warp-stretch failures may pertain to the translucent nature of the elastane core. Since the elastane core is translucent rather than opaque white, indigo dyed fibers are visible through the yarn core.
In an implementation, a fabric with excellent performance characteristic has (i) no overdyes, no coatings, (ii) pure indigo dyed at the lowest possible pH (indigo solution has pH of 11.2 or less), and (iii) premercerized warp yarns.
Some other important factors, having secondary impact, include: (i) coarse warp yarns (e.g., 7s-8s Ne rather than 13s-14s Ne), (ii) high twist warp yarns (above 4.6 twists), (iii) dyed at highest speed allowable to achieve desired shade (can vary between suppliers based on machinery), (iv) no sulfur bottoming or topping, and (v) 100 percent cotton warp.
Typically for denim, yarn counts range from a 7s Ne to a 16s Ne, though it is not uncommon to see counts as coarse as a 5s or as fine as a 20s. “Ne” represents an English cotton yarn count system (used by the textile industry for cotton spun yarns). It is an indirect way of indicating the coarseness of the yarn, where the lower the number, the coarser the yarn. A lower number is a coarser yarn. A higher number is a less coarse or finer yarn. Generally, dye will penetrate into a finer yarn faster than for a coarser yarn.
The English cotton yarn count system is calculated as follows: “Ne” refers to the number of hanks in pounds. One hank is equal to 840 yards of yarn. For example, 7s Ne (or a 7s count) is equal to 7 times 840 yards of yarn in 1 pound. And, 16s Ne (or a 16s count) is equal to 16 times 840 yards of yarn in 1 pound.
Some denim yarns have slub, which means a yarn has been engineered with thick and thin places to create a particular aesthetic. The diameter of the yarn is not uniform and can vary across its length. Slub patterns average about 0.25 mile in length of repeat and vary from mill to mill. Thus, the Ne calculation gives the average fineness or thickness of a yarn. Generally, a yarn is described by its yarn count, spinning method, and twist multiple. As an example, men's denim fabric generally use coarser counts like 7s and 8s, and women's denim fabrics generally use finer counts of 10s, 12s, and 14s. For stretch products, some finer counts are used.
Although this patent specifically describes laser finishing of woven fabrics, the techniques would also apply to knit fabrics used for knit apparel. A knit fabric is made by a series of interlocking loops of yarn. For laser finishing of knits, the techniques described to produce or obtain a ring-dyed yarn apply. Ring-dyed yarn is used to produce the knit. The knit which is made from ring-dyed can be laser finished.
In an implementation, a method includes processing a cotton yarn using an indigo dye to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye; and weaving the dyed cotton yarn into a denim fabric, where the warp yarns include dyed cotton and the weft yarns include undyed cotton, and the denim fabric is to be finished by exposing the dyed cotton yarn to a laser.
When exposed to the laser, the laser creates a finishing pattern on a surface of the garment based on a laser input file provided to the laser. The laser input file includes a laser exposure values for different laser pixel location. For each laser exposure value, the laser removes a depth or thickness of material from the surface of the denim material that corresponds to the laser exposure value.
For lighter pixel locations of the finishing pattern, a greater depth of the indigo ring-dyed cotton yarn is removed, revealing a greater width of an inner core of the dyed yarn, as compared to darker pixel locations of the finishing pattern, where a lesser depth of the indigo ring-dyed cotton yarn is removed, revealing a lesser width of an inner core of the dyed yarn.
The laser file includes grayscale values for each pixel location to be lasered. For example, a value can be from 0 to 255 (e.g., an 8-bit binary value) for up to 256 levels of gray. In an implementation, the lower the value, the greater the thickness of the material that will be removed. For a value 255, no material may be removed, while for 0, a maximum amount of material is removed to achieve a very white color, which would represent a well worn point (or pixel) in the finishing pattern. The 0 value may represent a removal of, for example, 50 percent (or more or less) of the thickness of the yarn.
In other implementations, reverse or negative logic may be use, where the greater the value, the less the thickness of the material that will be removed. For example, the greater the value, the greater the thickness of the material that will be removed. For a value 0, no material may be removed, while for 255, a maximum amount of material is removed to achieve a very white color, which would represent a well worn point (or pixel) in the finishing pattern. The 255 value may represent a removal of 50 percent (or more or less) of the thickness of the yarn.
In various implementations, the processing a cotton yarn can include immersing the cotton yarn into at least one indigo dye solution having a pH in a range from about 10.7 to about 11.6. The processing a cotton yarn can include immersing the cotton yarn into at least one indigo dye solution having a pH of about 11.6 or less.
The processing a cotton yarn can include immersing the cotton yarn into at least one indigo dye solution having a pH in a range from about 10.7 to about 11.2, and maintaining a temperature of the indigo dye solution at about 50 degrees Celsius or less (e.g., or 60 degrees Celsius or less or 70 degrees Celsius) while the cotton yarn is being immersed.
The processing a cotton yarn can include mercerizing an undyed cotton yarn in an alkaline solution before an initial immersion of the undyed yarn into an indigo dye solution. This may be referred to as premercerizing the yarn.
The processing a cotton yarn can include not immersing the cotton yarn into a solution including sulfur dyestuff before an initial immersion of the cotton yarn into an indigo dye solution. This may be referred to as not using sulfur bottoming during the processing.
The laser finishing can produce at least 64 different grayscale levels (e.g., at least 128 or at least 256) on the denim fabric. These would be optically distinguishable (e.g., optically distinguishable by a camera, photospectrometer, or the like) grayscale levels on the denim fabric. This allows the finish pattern to show better highlights or a greater distinction between the highs and lows in the pattern. This facilitates garment laser patterning with better aesthetics instead of a duller, less attractive finish. In other implementations, the laser finishing can produce at least 32 different grayscale levels, at least 128 different grayscale levels, or at least 256 different grayscale levels. Generally, the greater numbers of grayscale levels achievable with a particular fabric, the better the fabric's responsiveness to laser finishing will be.
Further, based on a value stored in laser input file, the laser removes a selected depth of material starting from the outer surface of the yarn. And as a result, a vertical segment of the inner core is revealed by the laser between outer core segments (e.g., left and right outer ring thickness) that is in a range from 0 to about 85 percent of the total thickness of the yarn. This produces at least 64 different grayscale levels (e.g., at least 128 or at least 256) on the denim material.
The cotton yarn can have from about 4.2 to about 4.8 twists per inch. The processing a cotton yarn can include: mercerizing an undyed cotton yarn in an alkaline solution before an initial immersion of the undyed yarn into an indigo dye solution, and immersing the mercerized cotton yarn into five or fewer separate dips of indigo dye solution having a pH of about 11.6 or less.
This patent describes some implementation-specific details specifying specific dimensions, measurements, percentages, temperatures, characteristics, times, pressure, pH, millivolts, specific gravities, and other values. These are not intended to be exhaustive or to limit the invention to the precise form described. The values are approximate values. These values can vary due to, for example, measurement or manufacturing variations or tolerances or other factors. For example, depending on the tightness of the manufacturing tolerances, the values can vary plus or minus 5 percent, plus or minus 10 percent, plus or minus 15 percent, or plus or minus 20 percent.
Further, the values are for some specific implementations of a process, and other implementations can have different values, such as certain values increased for a larger-scale implementation, or smaller for a smaller-sized implementation. The process may be made proportionally larger or smaller by adjusting relative constituents proportionally (e.g., maintaining the same or about the same ratio between different constituents). In various implementations, the values can be the same as the value given, about the same of the value given, at least or greater than the value given, or can be at most or less than the value given, or any combination of these.
Tables A-G give some examples of processes for manufacturing a laser-sensitive or light-sensitive fabric for use in manufacturing laser-finished apparel. In particular, the process is for dyeing of yarn or rope, which will be woven into a fabric (e.g., denim or twill). These processes can be used to obtain a ring-dye profile for yarn which will work especially well in laser finishing, as discussed above.
Each table has a column describing a process before being optimized to create a laser-sensitive fabric and another column describing that process after it has been optimized to produce fabric for laser finishing. In the optimized process, parameters have been changed or adjusted so that the fabric produced has improved characteristics for laser finishing. Some parameters have not been changed, and these are listed as common parameters. The parameters described below and elsewhere in this patent can be used individually or in any combination with other parameters to obtain a ring-dye cross-sectional profile that provides enhanced laser finishing results.
In the tables, a laser sensitivity score gives, based on a subjective evaluation, an indication of how well the material resulting from the process responds to laser finishing. The lower the number, the better the material responds to laser finishing. A laser sensitivity score of one is the lowest and best score. As can been seen in the tables, the after-optimization laser sensitivity scores are lower than the before-optimization scores.
The laser sensitivity scores or laser performance can be graded based on visual evaluation in response to a set of test finishes (e.g., benchmark finishes). For example, a grade 1 can represent that 95 percent of the finishes are achievable within the range of colors visible on the sample. A grade 2 can represent that 75 percent of finishes achievable. A grade 3 can represent that 50 of finishes are achievable. A grade 4 can represent that less 50 percent achievable. And a grade 5 can represent that little or no change visible.
Table A describes process parameters for processes A1 and A2. A1 is a process before optimization and A2 is for the process after optimization. Before optimization, A1 has a laser sensitivity score of 3, and after optimization, for A2, the score improved to 2.
The wetting agent used for these processed is known in the industry Cotto KD, which is an anionic and nonionic surfactant.
In anionic surfactants, the hydrophilic group is negatively charged. Anionic surfactants contain anionic functional groups at their head, such as sulfate, sulfonate, phosphate, and carboxylates. Prominent alkyl sulfates include ammonium lauryl sulfate, sodium lauryl sulfate (sodium dodecyl sulfate, SLS, or SDS), and the related alkyl-ether sulfates sodium laureth sulfate (sodium lauryl ether sulfate or SLES), and sodium myreth sulfate.
These surfactants do not bear an electrical charge and are often used together with anionic surfactants. Nonionic surfactants have covalently bonded oxygen-containing hydrophilic groups, which are bonded to hydrophobic parent structures. The water-solubility of the oxygen groups is the result of hydrogen bonding. Hydrogen bonding decreases with increasing temperature, and the water solubility of nonionic surfactants therefore decreases with increasing temperature.
When dyeing fabric, the room or ambient temperature can vary. For example, in a manufacturing facility in Pakistan, the average room temperature in the summer season is about 35 degrees Celsius, while in winter it is about 25 degrees Celsius. For manufacturing Turkey, the average room temperature while dyeing is about 28-30 degrees Celsius.
Rope dyeing consists of twisting the yarns into a rope that is then quickly dipped into indigo baths. Rope dyeing can achieve improved dyeing uniformity as compared to other indigo dyeing technologies, such as slasher dyeing.
As an example of rope dyeing, 32 ropes are simultaneously fed to the rope dyeing machine through various guides and tensioning arrangement to introduce the rope into a scouring box, which contains caustic liquid. After scouring, there are two wash boxes, a hot wash box followed by the cold one. After washing, the ropes are ready to enter the dye boxes. As previously described, there are typically a number of dye boxes or dye baths (e.g., eight dye boxes) and the number can vary depending on the type of dyeing desired. Dyestuff (e.g., liquid or powdered indigo dye) can added into the dye boxes through different metering pumps or mechanisms.
After exiting each dye box, the rope yarns are padded, squeezed, or pressed to remove excess dye. For example, the pressure can be uneven, such as highest at the first and last dye box (e.g., 55 pounds per square inch (psi) and after the intermediate boxes about 40-50 pounds per square inch). Or the pressure can be even across all dye boxes.
After padding, the ropes pass a number of sky rollers to provide adequate time of oxidation, which turns the rope and yarn an indigo color. After the dye boxes, the ropes can pass through wash boxes, where hot wash, cold wash, and neutralization can be performed. Sometimes a softener treatment is also applied in a wash box. The temperature of the boxes (e.g., dye box or wash box, or any combination) can be controlled through the control panel by means of thermostat.
Comparing A1 and A2, the pH of the dye baths is remains the same, in a range from about 11.8 to 12.0. The machinery is operating faster, increasing from about 25 meters per minute to about 28 meters per minute, which is about a 12 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 20 to 18 seconds, which is about a 10 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has increased from about 1.9 grams per liter to about 2.35-2.5 grams per liter. In combination with the reduced dwell time, this increase in indigo dye concentration can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
Pyradine extraction or indigo stripping. Regarding indigo extraction percentage, in general, the percent of indigo on weight of yarn of the optimized process should be no greater than a 15 percent deviation from that of their original as deducted from the indigo stripping method. In fabrics where sulfur is present the deviation is lower. In pure indigo, the deviation is higher.
Also, the sulfur bottom concentration has increased, which means the core has a greater concentration of sulfur dyestuff, which can help prevent the indigo dye from penetrating as deeply into the yarn core. And the yarn twist has increased from about 4.3 to 4.8 twists per inch (e.g., about an 11.6 percent increase). The yarn twist increase increases a tension of the yarn, which helps prevent the dyestuff from penetrating as deeply into the core.
A result of the changes from A1 to A2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, A2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table B describes process parameters for processes B1 and B2. B1 is a process before optimization and B2 is for the process after optimization. Before optimization, B1 has a laser sensitivity score of 4, and after optimization, for B2, the score improved to 2.
For the given yarn size, the yarn twist has increased from about 4.3 to 4.8 twists per inch (e.g., about an 11.6 percent increase). The yarn twist increase increases a tension of the yarn, which helps prevent the dyestuff from penetrating as deeply into the core.
A result of the changes from B1 to B2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, B2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table C describes process parameters for processes C1 and C2. C1 is a process before optimization and C2 is for the process after optimization. Before optimization, C1 has a laser sensitivity score of 4, and after optimization, for C2, the score improved to 3.
Comparing C1 and C2, the pH of the dye baths has decreased from about 11.8 to about 11.5 to 11.6. This pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 25 meters per minute to about 28 meters per minute, which is about a 12 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 21 to 19 seconds, which is about a 10 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has increased from about 2.2 grams per liter to about 2.6 grams per liter. The number of dips has decreased from 1+8 to 6. The salt content has increased from 30 to 40, which is about a 33 percent increase. The squeezing pressure at dyeing has decreased from 75 pounds per square inch to about 60 pounds per square inch. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
Salt in the dye boxes or specific gravity in dye box. Salt in the dye bath increases the affinity ionization in the dye bath. This is measured with a conductivity meter or specific gravity meter, and a good range is about 30-45 millisiemens per centimeter. If less than 30, the shade is too deeply fixed making it difficult to wash. If more than 45, the shade washes too quickly and is difficult to control. Once a saturation point of salt in the dye bath is reached, a mill should prepare a fresh dye bath so dye penetration is not impacted. Testing can be done manually with a hydrometer meter or electrically by measuring conductivity.
And the yarn twist has increased from about 4.6 to 4.7 twists per inch (e.g., about a 2 percent increase). The yarn twist increase increases a tension of the yarn, which helps prevent the dyestuff from penetrating as deeply into the core.
A result of the changes from C1 to C2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, C2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table D describes process parameters for processes D1 and D2. D1 is a process before optimization and D2 is for the process after optimization. Before optimization, D1 has a laser sensitivity score of 4, and after optimization, for D2, the score improved to 3.
Comparing D1 and D2, the pH of the dye baths has decreased from about 11.9 to about 11.5. This pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 28 meters per minute to about 30 meters per minute, which is about a 7 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 19 to 16.4 seconds, which is about a 14 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has decreased from about 1.3 grams per liter to about 1.1 grams per liter. The number of dips has decreased from 1+5 to 1+4. The salt content has increased from 25 to 35 millisiemens per centimeter, which is about a 40 percent increase. The squeezing pressure at dyeing has decreased from 70 pounds per square inch to about 55 pounds per square inch. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
And the yarn twist has increased from about 4.6 to 4.7 twists per inch (e.g., about a 2 percent increase). The yarn twist increase increases a tension of the yarn, which helps prevent the dyestuff from penetrating as deeply into the core.
The sulfur bottom concentration has decreased from about 30 grams per liter to about 15 grams per liter. And the sulfur bottom speed has increased from 28 meters per minute to 32 meters per minute; this results in less dip time in the sulfur bottom box. Since there is less sulfur bottom dyestuff in the yarn, this can result in a whiter yarn in the core, rather than a yellowish color when greater amounts of sulfur bottom dyestuff are deposited and allowed to penetrate.
A result of the changes from D1 to D2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, D2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table E describes process parameters for processes E1 and E2. E1 is a process before optimization and E2 is for the process after optimization. Before optimization, E1 has a laser sensitivity score of 3, and after optimization, for E2, the score improved to 2.
Comparing E1 and E2, the pH of the dye baths has decreased from about 12.1 to about 11.72-11.75. This pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 26 meters per minute to about 30 meters per minute, which is about a 14 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 20 to 18 seconds, which is about a 10 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has decreased from about 2 grams per liter to about 1.97 grams per liter. The number of dips has decreased from 10+1 to 6+1. The salt content has increased from 18-19 millisiemens per centimeter to 25 millisiemens per centimeter, which is about an 18 percent increase. The squeezing pressure at dyeing has decreased from 70 pounds per square inch to about 60 pounds per square inch. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
And the yarn twist has increased from about 4.2 to 4.4 twists per inch (e.g., about a 5 percent increase). The yarn twist increase increases a tension of the yarn, which helps prevent the dyestuff from penetrating as deeply into the core.
The sulfur bottom speed has increased from 28 meters per minute to 30 meters per minute; this results in less dip time in the sulfur bottom box. Since there is less sulfur bottom dyestuff in the yarn, this can result in a whiter yarn in the core, rather than a yellowish color when greater amounts of sulfur bottom dyestuff are deposited and allowed to penetrate.
A result of the changes from E1 to E2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, E2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table F describes process parameters for processes F1, F2, and F3. F1 is a process before optimization, and F2 and F3 is for the process after optimization. Before optimization, F1 has a laser sensitivity score of 4, and after optimization, for F2, the score improved to 3 and for F3, the score improved to 3.
Comparing F1 and F2, the pH of the dye baths has decreased from about 12.50-12.55 to about 12.55-12.59. This pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 20 meters per minute to about 25 meters per minute, which is about a 25 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 25.2 to 20.2 seconds, which is about a 25 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has decreased from about 2.68 grams per liter to about 1.66-1.71 grams per liter. The salt content has decreased from 55 millisiemens per centimeter to 41-42 millisiemens per centimeter, which is about a 25 percent decrease. The squeezing pressure at dyeing has increased from 70-80 pounds per square inch to about 70-90 pounds per square inch. The sulfur top speed has increased from 20 meters per minute to 25 meters per minute. This results in less dip time in the sulfur bottom box. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
A result of the changes from F1 to F2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, F2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Comparing F1 and F3, the pH of the dye baths has decreased from about 12.50-12.55 to about 12.43-12.45, which is less than for F2. This further pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 20 meters per minute to about 25 meters per minute, which is about a 25 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 25.2 to 20.2 seconds, which is about a 25 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has decreased from about 2.68 grams per liter to about 1.66-1.71 grams per liter. The salt content has decreased from 55 millisiemens per centimeter to 33-35 millisiemens per centimeter (which is less than for F2), which is about a 40 percent decrease. The squeezing pressure at dyeing has increased from 70-80 pounds per square inch to about 70-90 pounds per square inch. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
The parameters that are different between F2 and F3 include: F3 has a lower dye box pH. F2 has a mercerized sulfur top, while F3 has mercerized pure indigo. F3 has less salt content in the dye baths compared to F2. F2 has an additional dip in black dye box, while F3 omits this.
A result of the changes from F1 to F3 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, F3 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Table G describes process parameters for processes G1 and G2. G1 is a process before optimization and G2 is for the process after optimization. Before optimization, G1 has a laser sensitivity score of 4, and after optimization, for G2, the score improved to 2.
Comparing G1 and G2, the pH of the dye baths has decreased from about 12.5-12.55 to about 11.55-11.65. This pH decrease helps prevent absorption of the indigo dye into the core of the yarn, which enhances the ring-dye effect. The machinery is operating faster, increasing from about 20 meters per minute to about 25 meters per minute, which is about a 20 percent increase in speed. This means less time is spent in each box. A dwell time in boxes has decreased from about 25.2 to 20 seconds, which is about a 29 percent decrease. This means less dye is absorbed into the yarn.
The indigo concentration has increased from about 2.3 grams per liter to about 2.73-2.86 grams per liter. The number of dips has decreased from 9+1 to 5+1. The salt content has decreased from 55 millisiemens per centimeter to 32.5-33.7 millisiemens per centimeter, which is about a 40 percent increase. The squeezing pressure at dyeing has decreased from 80-100 pounds per square inch to about 70-90 pounds per square inch. These factors in combination can result in more of the indigo dye being deposited on the surface of the yarn, rather than penetrating into the core.
A result of the changes from G1 to G2 is to obtain an optimized ring-dye profile for yarn that will perform better and obtain better results for laser finishing. For example, G2 can obtain a yarn to have a cross section having an outer ring and an inner core, where a thickness of the outer ring is about, for example, from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
Cotton selection and consistent cotton source. A process can change depending on the cotton used. Changes in cotton source or quality can impact final cast of fabric due to shade of cotton directly impacting final dye shade, or from changes in length and micronaire impacting dye uptake. Micronaire or MIC is a measure of the air permeability of compressed cotton fibers. It can be used as an indication of fiber fineness and maturity.
Improved or optimal micronaire (e.g., about 4.2 to 4.6) gives better ring dyeing. Coarser micronaire (e.g., about 4.6 to 5.2) tends to give fixed indigo and bluer shades. Higher the micronaire, immaturity in cotton increases. Very fine micronaire also creates problem as cotton is immature (e.g., less than about 3.8). High level of maturity in cotton have good amount of crystalline regions which avoid deep penetration of indigo molecules.
Using high crystalline cotton or high maturity cotton mostly gives good ring dyeing. On the other hand, mercerization of raw material can be used to reduce the raw material variation. Mercerization's helps to deliver consistent shade against different cotton having different maturity and micronaires. When a factory or mill does mercerization, amorous regions increases and more OH bonding areas for dye linkages. Also mercerization increases the area of cotton fiber and due to this yarn is compacted and avoided the deep penetration by indigo into core. But due to this, color quantity on surface increases, and it may be necessary to retard the fixation by increasing the millivolts of the dye bath. Also higher millivolts for the dye bath increases salinity and helps to create some affinity primarily at the surface of the yarn.
For cotton yarn, a cross-sectional diameter of the yarn before mercerization can be assigned a value 1. When mercerized, the yarn is soaked in, for example an 18 percent solution of sodium hydroxide (NaOH), which causes swell. The swelling process can cause the cross-sectional diameter of the yarn to increase to a value 1.3, relative to the premercerized yarn. This means the yarn swells to have a diameter about 30 percent larger than the premercerized yarn. Then, after the sodium hydroxide soak, the yarn is rinsed and its diameter shrinks slightly relative (e.g., a diameter value of 1.15) to the time in the sodium hydroxide soak. In a final state, the mercerized yarn further shrinks further to have a diameter value of 0.8, relative to the premercerized yarn. This means the yarn has shrunken to have a diameter about 20 percent less than the premercerized yarn.
In various process implementations, the pH of the dye baths is from about 11.8 to about 12.0, about 12.0 or below, about 11.8 or below, about 11.5 or below (reduced from about 11.9 or above), about 11.75-11.72 or below (reduced from about 12.1 or above), about 11.74 or below, about 11.73 or below, about 12.59-12.55 or below (reduced from about 12.55-12.50 or above), about 12.43-12.45 or below (reduced from about 12.55-12.50 or above), about 11.65-11.55 or below (reduced from about 12.55-12.50 or above), about 11.64 or below, about 11.63 or below, about 11.62 or below, about 11.61 or below, about 11.60 or below, about 11.59 or below, about 11.58 or below, about 11.57 or below, or about 11.56 or below.
In various process implementations, the machine speed for the rope or yarn in meters per minute is about 28 or greater (increased from about 25 or less), about 30 or greater (increased from about 28 or less), about 30 or greater (increased from about 26 or less), or about 25 or greater (increased from about 20 or less).
In various process implementations, the yarn twist in twists per inch is about 4.8 or greater (increased from about 4.3 or less), about 4.7 or greater (increased from about 4.6 or less), about 4.4 or greater (increased from about 4.2 or less), about 4.6 or greater, about 4.5 or greater, or about 4.2 or greater.
In various process implementations, the indigo concentration in grams per liter is about 2.35-2.5 or more (increased from about 1.9 or less), about 2.35 or more, about 2.36 or more, about 2.37 or more, about 2.38 or more, about 2.39 or more, about 2.4 or more, about 2.41 or more, about 2.42 or more, about 2.43 or more, 2.44 or more, 2.45 or more, 2.46 or more, 2.47 or more, 2.48 or more, 2.49 or more, about 2.6 or more (increased from about 2.2 or less), about 1.1 or less (decreased from about 1.3 or more), about 1.71-1.66 or less (decreased from about 2.68 or more), about 2.73-2.86 or more (increased from about 2.3 or less), about 2.74 or more, 2.75 or more, 2.76 or more, 2.77 or more, 2.78 or more, 2.79 or more, 2.80 or more, 2.81 or more, 2.82 or more, 2.83 or more, 2.84 or more, or 2.85 or more.
In various process implementations, the squeezing pressure at dyeing in pounds per square inch is about 66 or less, about 55 or less (decreased from about 70 or more), about 60 or less (decreased from about 70 or more), about 70-90 or less (decreased from about 80-100 or more), about 89 or less, about 88 or less, about 87 or less, about 86 or less, about 85 or less, about 84 or less, about 83 or less, about 82 or less, about 81 or less, about 80 or less, about 79 or less, about 78 or less, about 77 or less, about 76 or less, about 75 or less, about 74 or less, about 73 or less, about 72 or less, or about 71 or less.
In various process implementations, the salt content in a dye bath in millisiemens per centimeter is about 40 or more (increased from about 30 or less), about 35 or more (increased from about 25 or less), about 25 or more (increased from about 18-19 or less), about 42-41 or less (decreased from 55 or more), about 35-33 or less (decreased from 55 or more), about 33.7-32.5 or less (decreased from 55 or more), or in a range between about 30 to about 45.
An existing process to manufacture yarn for fabric can be modified to improve the performance of the resulting fabric's responsiveness to laser finishing. Some parameters can be modified include: reduced percentage of dyestuffs; reduced prewetting agents; faster dip speeds, lower temperatures; premercerization; lower pH, or lower squeezing pressure, or any combination of these. With these manufacturing modifications, a fabric's performance for laser finishing is improved.
Strong performance for a fabric to laser finishing can be described as (i) fast color change with minimal laser irradiation; (ii) color changes to a hue close to white; and (iii) minimal degradation to strength or stretch properties, or both. Poor performance can be described as (i) slow color change; (ii) color changes to a color with noticeable hue, such as grey, blue, or green; or (iii) unacceptable degradation to strength or stretch properties, or both, or any combination of (i), (ii), and (iii).
For laser finishing, the fabric (e.g., denim) is lightened by fiber removal. The speed of color change via laser is dependent on the depth of the indigo ring-dye. And, the maximum whiteness of a highlight is dependent on the hue of the yarn core.
Laser finishing works different from previous techniques of lightening fabric, which rely on the use of oxidizers (e.g., potassium permanganate or KMnO4). Instead of fiber removal, oxidizers remove dyestuff from the fibers themselves, thus lightening the material. The fiber itself it not removed, but remains. In connection with oxidizers, abrasives (e.g., sandpaper) can be used to select regions to lighten differently relative to other regions. Abraded areas will be lighter than unabraded areas. This is because the abrasives break up the cotton fibers, revealing more of the fiber—creating a greater surface area of the dyed fiber for the oxidizer to attack. Then the oxidizer can work more effectively to remove more dyestuff in the abraded regions, as compared to the packed cotton fiber in the unabraded areas. The abrasion itself is not to lighten the material. The oxidation process is unlike laser finishing.
Laser finishing creates highlights by digging into the warp until the white core is revealed. Warp yarns with a thicker ring-dye require more fibers to be removed before the white core is exposed. This means more laser, more time, more energy, more damage, which is undesirable because the fabric is weakened. Therefore, enhanced fabrics for laser finishing will contain warp yarns with a shallow depth ring-dye.
Some techniques can be used manufacture a yarn with ring-dye characteristics for laser finishing. It is desirable to more easily uncover undyed core fibers by keeping these fibers close to the surface of the yarn. This can be achieved through chemistry or yarn structure, or both.
With chemistry, a shallower ring-dye for laser finishing can be achieved by: (1) Low or lower pH. A lower pH reduces indigo dye affinity to fiber, reducing penetration. (2) Premercerization. Swelling of fibers makes indigo dye penetration more difficult, reducing ring-dye depth. (3) Lower dye concentration and faster dyeing speed. If shade matching is not important, reduce opportunity for dye penetration.
With yarn structure, a shallower ring-dye for laser finishing can be achieved by: (1) Higher yarn twist. High yarn twist makes dye penetration more difficult, reducing ring-dye depth. (2) Coarse yarn count. Ring-dye depth is a lower percentage of the total yarn diameter, leaving a large un-dyed yarn core. More fibers remain for improved tear or tensile. For equivalent bath concentrations and warp ends, ratio of dye to fiber mass in bath is lower. Fine yarns are at risk of becoming dyed to the center, leaving no undyed fibers to provide color change and highlight.
It is desirable to lighten the color of the yarn core. An undyed core leads to a whiter highlight. This can be achieved through chemistry or yarn structure, or both.
With chemistry, a whiter core for laser finishing can be achieved by: (1) Minimize or eliminate sulfur bottoming. Due to the affinity of sulfur dyestuff to cotton, sulfur dyes penetrate to the yarn core, dyeing the once-white core fibers. The fabric will now highlight to the color of the sulfur bottom. A small amount of sulfur may be acceptable if the core fibers are dyed to a negligible color change. If sulfur bottoming is important, a dark indigo dye can create the illusion of bright highlights via contrast against base shade.
(2) Sulfur topping. Sulfur topping is less difficult than bottoming because many dye-sites are already occupied by indigo, and loose indigo slows penetration of sulfur into yarn. However, sulfur topping still contributes to the total dye quantity; high concentrations can still lead to poor performance, particularly with fine yarns. (3) Faster speed indigo dips. If shade matching is not important reduce the amount of dye, and opportunity for dye penetration. (4) Lower dye concentration. If shade matching is not important reduce the amount of dye, and opportunity for dye penetration.
With yarn structure, a whiter core for laser finishing can be achieved by: (1) Coarse yarn count. For fine yarns, dye penetration makes up a larger percentage of total yarn diameter, leaving only a small white core, meaning the ratio of blue to white fibers is higher. This causes the highlight to appear blueish rather than white. Fine yarns are also more at risk for physical failure before highlight is achieved due to removal of a larger percentage of total fiber.
(2) Minimize elastane fibers in warp. Some warp-stretch fabrics may show poor performance because the elastane core is clear rather than white. This would mean the “target” for a white highlight is doughnut shaped yarn core, which is a more difficult target to hit, particularly in finer yarn counts. Stronger performing warp-stretch fabrics are likely to have both a shallow ring-dye, and a large yarn diameter. Further, some warp-stretch failures may pertain to the translucent nature of the elastane core. Since it is translucent rather than opaque white, indigo dyed fibers are visible through the yarn core.
As described, there are various techniques to achieve a fabric (e.g., denim or twill) with enhanced performance for laser finishing. Some important factors to achieve excellent performance in a fabric include: no overdyes, no coatings; pure indigo dyed at the lowest possible pH; or premercerized warp yarns, or any combination of these. Other important factors, but of secondary impact, include: coarse warp yarns (e.g., 7-8 Ne, which is lower than 13-14 Ne); high twist warp yarns (e.g., above 4.6); dyed at highest speed allowable to achieve a desired shade, which will vary based on machinery used; no sulfur bottoming or topping; or 100 percent cotton warp, or any combination of these.
In an implementation, a method includes: twisting cotton fibers to obtain a cotton yarn having from about 4.5 to about 4.8 twists per inch; providing a number of dye boxes, each dye box containing an indigo dye solution having a pH in a range from about 10.7 to about 12.0; maintaining the indigo dye solution for each of the dye boxes at a temperature of at least one of about 88 degrees Celsius or less, or 75 degrees Celsius or less; immersing the cotton yarn through the indigo dye solution of a first dye box of the dye boxes; removing the cotton yarn from the first dye box and exposing the cotton yarn to air (including oxygen), where a temperature of the air (e.g., at about 25 to 40 degrees Celsius) is less the temperature of the indigo dye solution; after exposing the cotton yarn to air, immersing the cotton yarn through the indigo dye solution of a second dye box of the dye boxes; removing the cotton yarn from the second dye box and exposing the cotton yarn to the air; and drying the yarn and obtaining a dyed cotton yarn having a cross section with an outer ring and an inner core, where a thickness of the outer ring is from about 7.5 percent to about 12.5 percent of a total thickness of the yarn, and the outer ring is indigo colored due to being penetrated through by the indigo dye while the inner core is white or off-white colored due to not being penetrated to by the indigo dye.
In various implementations, the method can include mercerizing an undyed cotton yarn in an alkaline solution before immersing the cotton yarn into the first dye box of indigo dye solution. The number of dye boxes can be at least 2 dye boxes and less than 6 dye boxes (e.g., 5 dye boxes). The method can include not immersing the cotton yarn into a solution comprising sulfur dyestuff before immersing the cotton yarn into the first dye box of indigo dye solution.
The method can include weaving the dyed cotton yarn as warp yarns in a twill pattern and obtaining a denim fabric, cutting the denim fabric to obtain fabric panels; and assembling and coupling the fabric panels to obtain a garment. The method can include exposing the garment to a laser to create a finishing pattern on a surface of the garment based on a laser input file provided to the laser. The laser input file includes a number of laser exposure values, each for a different laser pixel location. For each laser exposure value, the laser will remove a depth of material from the surface of the garment that corresponds to the laser exposure value. For lighter pixel locations of the finishing pattern, a greater depth of the dyed cotton yarn is removed as compared to darker pixel locations of the finishing pattern, where a lesser depth of the indigo dyed cotton yarn is removed.
After dyeing, the dyed cotton yarn will have a ring-dyed cross-sectional profile. The indigo dye solution for each of the dye boxes can have a salt content of from about 25 to 40 millisiemens per centimeter. The indigo dye solution for each of the dye boxes can have a millivolt reading from about 700 to 750 millivolts. The cotton yarn can be immersed in the first dye box (or each of the dye boxes) for about 15 to 20 seconds. The method can include after removing the cotton yarn from the second dye box, squeezing the yarn at pressure from about 55 to 90 pounds per square inch.
This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.
This patent application claims the benefit of U.S. patent application 62/685,260, filed Jun. 14, 2018, which is incorporated by reference along with all other references cited in this application. U.S. patent application Ser. No. 15/841,263, filed Dec. 13, 2017, and 62/433,739, filed Dec. 13, 2016, are also incorporated by reference.
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