Dye Methods
What are Dyes?
There is evidence of dyes being used dating back as far as 2500 B.C. Dyes capable of producing a full range of hues on linen, existed by 1400 B.C. Mixing red, yellow and blue dyes of produce secondary and tertiary shades on fabrics was practiced before 150 A.D., and the art of oriental rug making with splendid variety of colors and patterns was approaching its peak by 1500 A.D.
From the beginning to mid 1800 the dyes used were mostly of the vegetable origin. Sources of supply were limited. Standaridization was nonexistent and fastness qualities were in most cases very poor.
In the mid 1800's chemical pioneers discovered ways in which synthetic dyes could be produced in the laboratory. What started in home laboratories, has now become a world wide industry producing over 7000 different dyes. Today, pigment and dye manufacturers produce well over $1 billon annually.
Properties of Dyes:
All dyes must have a number of properties in order to be useful. They must be highly colored and yield colored goods with good fastness qualities. Fastness refers to a fibers resistance to color loss due to fading (exposure to light) and crocking, (resistance to washing). Dyes must be soluble in the medium in which they are applied. They must possess an affinity or chemcial attraction to the fiber that is applied to and from a chemical bond to that fiber.
Acid Dyes:
Acid dyes are derived from the dyeing process itself. Acid dyes are applied to wool, silk and polyamides in the presence of an organic or nonorganic acid and, hence, are called acid dyes. Acid dyes are anionic (negative charge) with a relatively low molecular weight. Most nylon carpets produced today are dyed with an acid dye system.
Basic Dyes:
Basic dyes produce a positive charge and are used in dyeing acrylic, modacrylic, modified nylon, and polester fibers.
Direct Dyes:
Direct dyesa re used in the coloring of cotton and other cellulosic fibers (i.e., rayon, linen, jute, etc.).
Vat Dyes:
Vat dyes are particularly suited for use on cotton and rayon fibers. They are also used to dye nylon and to stain polester in blends with cellulosic fibers.
Sulfur Dye:
Sulfur dyes area applied primarily to cotton and rayon. However, they do find some use in dyeing nylon blends with cellulosics.
Azoic Dyes:
Azoic dyes and pigments form the largest single chemical group of all synthetic colorants. They are used on most cellulosic fibers, as well as polyester. They offer good lightfastness qualities, however fair to poor fastness to west and dry crocking.
Disperse Dyes:
Disperse dyes are nonionic (no electrical charge). They offer very low solubility in water. Therefore, must be dispersed or suspended in water containing large amounts of dispersing or wetting agents. Disperse dyes are commonly used in dyeing polyester fibers and occasionally nylon.
Reactive Dyes:
Reactive dyes are extremely colorfast due to a covalent chemical bond with the fiber. They are used when extreme colorfast properties are desired in cellulosic fibers.
Dye Methods used in Manufacturing New Carpet:
Many of these different effects are produced by using fibers that are manufactured to accept different types of dyes, in various amounts, in conjunction with one or multiple dye systems. Dye methods that are commony used in the manufacturing of wall to wall carpets today, are:
PRE-DYED POST-DYED (PIECE DYED)
Package Dyeing Beck/Piece Dyeing
Space Dyeing Differential Dyeing
Solution Dyeing Print Dyeing
Stock Dyeing Continuous Dyeing
Skein Dyeing
Pre-Dyeing:
Package Dyeing - Similar to skein except the fiber is dyed after it has been made into multiple yarns. The yarn is wound on perforated forms called packages and again under heat and pressure, the dyes are forced into the yarn. After drying and rewinding, the yarn is ready to be tufted or woven into carpeting.
Space Dyeing:
This method of dyeing is used to produce a large percentage of continuous filament nylon commercial carpeting, generally levevl loop texture. Using a special dyeing machine, two or three different colors or shades are placed side by side on the same piece of yarn creating a random colored or mottled effect.
Solution Dyeing:
This produces one of the most steadfast and permanent colors in carpet. Solutionh dyeing is completely differnet from the previous methods and is only used with man-made fibers. The dye actually becomes part of the yarn fibers by adding the prigment to the fiber material when in a liquid state, prior to being force throught the spinneret, during extrusion.
All polypropylene fibers are solution dyed, while only a small portion of current nylon production is dyed in this manner. However the percentage of nylon is increasing rapidly in a quest for stain resis- tance, particularly in the commercial segment of the market.
Stock Dyeing:
One of the first methods used to dye wool and staple synthetic fibers before they are spun into yarn. The process involves circulating heated dye under pressure through large batches of uncolored fibers. After the fiber has cooked for several hours in large pressure tanks, it is usually removed, set with steam and then cut into staple lengths (about 6 inches). The staple lengths are then blended several times to insure uniform color throughtout; this is followed by a final washing and drying and the fiber is now ready for spinning into yarns.
Skein Dyeing:
A process similar to stock dyeing, except that the fibers are spun into single strands before plying into yarns. These single strands are known as skeins; This is where the term skein dyeing originates.
Dyeing yarn in skein form is used for small lots. It is usually less expensive than package dyeing. Yarn is unwound from cones to skeins and then mounted and immersed into a large hot dye vat. After dyeing and drying, the dyed singles are ready for plying into finished yarn.
Post-Dyeing (Piece Dyeing):
Post dye (or piece dye) indicates that the yarn was undyed when tufted and then the unfinished carpet was dyed. This undyed carpet with no secondary back is called \"griege goods.\" The two most popular/common methods of dyeing are the Beck and Continuous processes. With the advent of air entanglement and emphasis on stain cleanability, solution dyeing will undoubtedly become more popular.
Beck/Piece Dyeing:
Also called beck dyeing or vat dyeing, this method, up to 200 yards of tufted carpet (minus latex and secondary backings) are run through a large stainless steel tanki called a Dye Beck. The ends of the carpet are sewn together and tufted primary backing (greige goods) is rotated throught the heated dye until the desired color is achieved. Recent developments in dyeing technology have brought about several improvements in piece dyeing. Today, by tufting the carpet of specially treated yearns, it is possible to obtain up to four different colors or shades by running the carpet through a single vat of dye.
Differential Dyeing:
Tufted carpet with a yarn treated chemically so that when placed in a dye bath each yarn type will react differently to the dye, resulting in different shades of the same color.
Print Dyheing:
The direct application of dye to the carpet surface in the form of a pattern. After the carpet is tufted, the pattern, in up to six colors, is sprayed on or silk screened in place. Many of the colored kitchen or bathroom carpets are dyed using this process.
Cross Dyeing:
Multi-color effect created in a fabric using fibers of different affinities.
Continuous Dyeing Range:
This system is much like an automated beck dyeing system. Greige-unbacked carpet is fed into an immersion bath filled with hot dye liquor. Then the wet dyed carpet is steamed to set the dye. This is followed by wash boxes that take out all loose dye or strong chemicals. The dyed carpet is then dried and rolled for secondry backing.
This process is the most economical dye method used. It became very popul;ar for dyeing in t he 1970\'s due to the energy crisis. It is very conducive for dyeing large volumes of carpet. After tufting, greige goods are sew end to end and fed continuously through large dye machines. Dyestuff is sprayed directly onto the carpet and proceeds directly into large steam chambers that aid in setting the dyes.
Dye Problems:
Bleeding:
The migration of dye in the presence of liquids is called bleeding. If the carpet dye is not set properly or a chemical reaction such as high PH loosens it from the fibers, it may become mobile when wet from cleaning. This means that the dye may run into areas where it is not supposed to be. Example: A red dye may run into a white area of the carpet. If this starts to occur while cleaning, most often appl;ying a solution of 7% acetic acid will halt the color run.
Crocking:
The physical removal of dye or pigment due to wet or dry agitation. If the carpet contains too much dye, it will allow the excess to walk off. Example: If a red carpet is installed next to a white carpet at a seam, often the white carpet will turn pink near the seam from the excess dye being walked off onto the white carpet.
Fume Fading:
Also referred to as gas fading, this is a loss or shift in the dye color of the carpet due to attack by gasses or atmospheric contaminants. Ozone, generated during thunderstorms or near bodies of water, oxides of nitrogen from gas furnaes, and aldehydes from particle board are the most common fading agents. This may occur throughtout the carpet or in an isolated area such as under skirted upholstery made of particle board.
Light Colored Stains:
If a stain is lighter than the color of the carpet, there is some dye loss to the fibers. This type of stain is not possible to solve with cleaning. The only answer is to replace the color loss.
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