Dyeing of Microfiber Made Fabric

MICRO FIBER FABRIC DYEING

Maruf Mahfuz
Email: maruf.txt@gmail.com
Cell: 01738676060
Department of Textile Engineering
World University of Bangladesh





History of Microfibers :
Japanese fibre manufacturing companies introduced the first ‘micro-denier’ products during the 1970s. Then followed the developments in Europe during the 1980s, and since the 1990s American fibre manufacturers have been following suit. At present, polyester and nylon are generally used for manufacturing microfibres. However, ‘micro-denier’ versions of rayon and acrylic products are on the horizon.

For as long as microfibre technology has been around, ultra-microfibre technology has existed as well. These are fibres that are less than 0.3dtex, and especially within the range of 0.1dtex. Several different processes can be used to make these fibres, all involving the splitting of a larger fibre into many smaller ones.

A synthetic fiber that is extremely soft, lightweight, breathable, durable and ultrafine. In fact, microfibers are two times finer than silk and one hundred times finer than a human hair. Microfiber is currently manufactured from acrylic, nylon, polyester and rayon. Ultra-microfibers on the market are even finer – some having thickness of just 1/200th the thickness of human hair!

General Properties of Microfibers :
  • Ultra-fine linear density (less than 0.1 dtex/f), finer than the most delicate silk.
  • Extremely drapeable.
  • Very soft, luxurious hand with a silken or suede touch.
  • Washable and dry-cleanable.
  • Shrink resistance.
  • High strength.
  • Insulates well against wind, rain and cold.
  • Anti-microbial agents help to protect both family members and work staff from the dangers of the bacteria that cause odour and mildew.
  • Microfibre is hypoallergenic, and so does not create problems for those suffering from allergies.
  • Microfibre is non-electrostatic.
  • Microfibres are super-absorbent, absorbing over 7 times their weight in water.
  • Microfibre dries in one-third of the time of ordinary fibres.
Microfibres refer to staple fibres, or individual filaments within yarns, which have fineness less than 1 decitex ( 1 grams per 10,000 meters) and For any fiber to be classified as microfibre yarn, the weight per 10,000 metres of yarn (dtex) is divided by the number of filaments (f), the result must be below 1.

Micro fibers supervised as :
  1. Lightweight and flexible
  2. Good stability and shape retention
  3. Anti-wrinkle property
  4. Have a wicking ability that permits perspiration
  5. Comfortable to wear as they are more spongy
  6. Doesn't water stain - superior water repellency is available
  7. Woven or knitted into a very high quality fabric construction
  8. Formerly commenced as a polyester microfiber, today you can find nylon, rayon and acrylic microfibers too.
  9. Strong and durable, water repellent and wind resistant -so tightly woven, that the fabric can't be penetrated by wind, rain or cold
  10. Lightweight, resilient or resist wrinkling, have a comfortable array, preserve shape and resist pilling.
  11. The positively charged microfibers draw dust; the tiny fibers are capable to enter the microscopic surface voids most materials.
  12. Washable, dries quickly and also washable in at the water temperatures up to 200 degrees and their characteristics will remain intact.
  13. Electrostatic effect - Hair, lint and other dust particles are attracted and grabbed by the microfibers without lifting dust.
  14. The density of the material allowable it to grip six to eight times its weight in water hence high absorbing power capacity.
  15. The attraction capability of the microfibers is so sound, even absorbs bacteria and germs - hence can be use as germ or bacteria free purpose.
  16. The fabric consists of millions of small tiny conduits that carry oil and grease too.
Benefits of Microfibers :
  • Comfortable - very soft, texture like silk, lightweight
  • Due to its fineness and superior fiber surface area making deep, rich and bright colors achievable.
  • Less "sweaty" in warm weather than usual synthetics
  • Quickly cleanable - clean just with water
  • Highly intense and shrink-resistant
  • Presents insulation and breathability
  • Change without help - to establish lovely drape
  • Very fine - finer than the most precise silk
  • More reusable for cleaning alternative - compared to other mops more efficient and long life .
Dyeing Properties of a Polyester Microfiber :
Sorption isotherms and dyeing rates of purified disperse dyes on polyester microfibers (fineness of 0.25-1.0 denier) from water have been measured at 95°C. The isotherms are curved and well described in terms of the dual-mode sorption model: Nemst-type partitioning and Langmuir sorption are concurrently operative. The effect of a diffusional boundary layer on the dyeing rate is small under the conditions; the microfibers were dyed in the form of a bulky two-ply yarn in a well stirred bath. Dyeing rates of a commercial dye are also measured at 110 and 130°C. For dyeing of a 0.32d fiber at 130°C, the amount of dye sorbed by the fibers attains a maximum value at an early stage and then decreases gradually. This phenomenon is explained in terms of the aqueous solubility of very fine dye particles. The relation between dye sorption behavior and the fine structure of the microfibers is discussed.

Dyeing properties of a polyester taffeta made from ultrafine fibers (0.07 denier) with disperse dyes are clarified through an analysis of sorption isotherms and rate of dye sorption data in comparison with those for microfibers (0.25, 0.32, and 0.44 denier). Ultrafine fibers are made using sea-island-type conjugate spinning techniques, while the microfibers are made by the conventional melt spinning method. Physical properties of the ultrafine fibers relating to the dyeing properties are also measured. The sorption-diffusion behavior of purified disperse dyes in the 0.07 denier (0.07d) fibers at 95°C and the physical properties of these fibers are almost the same as those of the microfibers, except for the 0.25 denier (0.25d) fiber, which contains 0.5% additives to facilitate spinning. Therefore, ultrafine fibers can be dyed by considering only the difference in the fiber radius. Two polyester taffetas are used to measure dyeing kinetics, i.e., 0.07d fibers and 0.25d fibers. Delay of dye sorption at the initial stage is appreciable for the 0.07d taffeta with purified dyes at 95°C and the 0.07d and 0.25d taffetas with commercial dyes at 120°C. This phenomenon is explained in terms of the presence of diffusional boundary layers around the individual filaments caused by the very slow movement of dye liquor through the taffetas. Color yields of the commercial dyes on the two taffetas are discussed.

Dyeing of Polyester Microfibers :

Due to their fineness, the total surface area of microfibre yarn or fabric is far greater than ordinary fibres. Therefore,
  1. Due to its special structure ,micro fibers has much larger quantity of size ,oil agents and wax on warp yarns.
  2. Since microfibres have very small interstitces, with consequent difficulties of size accessibility and duffusibility, desizing becomes quite difficult and costly.
  3. Microfibres have greater absorption area resulting in a dyeing rate four times higher than that of normal, which can cause unlevelness in dyeing.
  4. They also require more dyestuff than standard fibres to obtain the same depth of shade.
  5. Larger external surface means an increase in number of threads exposed to light which, on destruction of dye, is expressed as lower light fastness rating.
  6. Wash fastness and color fastness to rubbing is also poor.
  7. Staple microfibres offer difficulty in carding.
The problems in wet processing of micro fibers can be overcome by :

1. Better knowledge about the size applied and optimum parameters during desizing operation.

To achieve satisfactory dyeing effects, desizing and refining process must be done before dyeing and after desizing and refining , there should be no impurities left such as electrolyte, antistatic finishing agent, spin finishes and blot.

2. Pre-setting
Suitable pre setting conditions ( time ,temperature and tension) helps not only in stable dimensional stability , softness but also better dyeing results.

3. Alkali weight reduction
Alkali weight reduction s to treat the fabric with concentrated alkali at high temperature.fber molecule hydrolyse under this condition and lose some weight with change in properties, thus space occurs between crossing points and rubbing resistance relative to slippage among yarns becomes small.Alkali weight reduction makes fabric soft, liveliness, limber and improved absorption.

4. Careful selection of the dyes.

Proper dye selection for microfiber dyeing :
  1. Compatible
  2. Having same exhaustion rates
  3. Having high wash fastness properties.
  4. Good migration and levelling properties
  5. Eliminates problems regarding build-up and fastness properties.
  6. Disperse dyes for polyester microfibers
Optimizing the dyebath conditions and dyeing cycle :
Optimized dyeing cycles can be worked out by controlling the temperature to account for the high rate of dyeing and to eliminate the risk of uneven dyeing. Chemicals and dyes to be added at, at least 10-20°.C lower temperature than normal polyester fiber dyeing. The additions of dyes must be progressive or divided at least into 4 parts. The heating rate must be slow from 40 deg C to 100° C. 10-20 min more holding time required at 130° C as compared to normal PES.

Proper Selection of Dyeing machinery :
The dyeing machine must have the required automation to fulfill the requirements of microfiber dyeing such as microprocessor controlled dosing , proper and accurate heating rate control etc.

Proper selection of dye bath additives such as :

Leveling agents: - A strong leveling agent which shall start working at lower temperatures.

Dispersing agents: - Higher quantities of dispersing agents are needed because amount of dyes required are more to produce the desired depth.

Chelating agents:- Ant creasing agents,Dyebath softeners/Lubricants :- Because microfiber textiles are prone to creasing , therefore use off dye bath lubricants is must.

Soaping: - In order to obtain satisfactory color effect, fabric should be soaped after dyeing .Soaping is the key process to achieve satisfactory dyeing results especially on polyester / nylon micro denier fabric.

Reduction clear :- Good reduction clear process is needed to achieve satisfactory washing , rubbing and light fastness properties.

Washing :-Is required for neutralizing and removing alkali after reduction clear treatment.

Softening, anti soil and antistatic treatment. Because micro denier fiber easily stains and produces static charges, a hydrophilic, antistatic and antisoil treatment besides softening is highly recommended to ensure fabric softness and comfort ability.

Recommended Dyeing Cycle for polyester Microfibers :
Dianix PLUS( Dystar) or Longsheng is a new range of five compatible, level-dyeing dyes for reliable dyeing of medium and heavy shades, especially on microfiber and weight-reduced polyester, whether applied under mild alkaline conditions to control trimer, or under conventional acid conditions. Dianix E-PLUS" for Pale Shades on Polyester Fabrics. Fashion application of polyester.

Application of Microfibers dyed good :

Microfibers are most commonly found in polyester and nylon. Some rayon and acrylic micros are in production and available to consumers. Micros can be used alone or blended with conventional denier man-made fibers as well as with natural fibers such as cotton, wool, and silk.

In textiles,
Microfibers are used in a variety of fabrics, but most commonly in dress and blouse weight garments. Suit jackets and bottom weights are becoming available. Look for micros in lingerie, rainwear, outdoor fleece and wind-resistant sportswear, as well as tents, sleeping bags, track and jogging suits. The strength of microfibers make them particularly adaptable to sueded or sandwashed finishes because of their extensive fiber surface area and the use of strong fibers like polyester and nylon. As a result, many microfibers simulate the appearance of sandwashed silk.

Other Main products for which microfiber are ideally suited:
  • Microfiber Glass Cloth
  • Duster/Multi-purpose Microfiber Cleaning Cloth
  • Microfiber Scrubber
  • Microfiber Kitchen Cloth
  • Microfiber Optical & CD Cloth
  • Microfiber Mops
  • Microfiber Cleaning Sponge
  • Microfiber Cleaning Cloths – Terry Cloths, Suede Cloths, Waffle-Weave Cloths .
Disperse dyestuff for polyester fiber also adsorbs well to nylon fiber, however, the wet and light fastnesses of the dyestuff adsorbed on nylon tend to be poor. In order to attain good fastness in the dyeing of polyester/nylon, it is therefore preferable that the polyester component is dyed with disperse dyestuff with care taken in minimizing its adsorption to (staining on) the nylon component, which can then be dyed with dyestuff that is usually used for nylon with good fastness.

Dyeing at 110°C using a carrier will be effective as a disperse dyeing method for polyester/nylon, in which a deeper shade on the polyester component is produced and dyestuff adsorption to the nylon component is inhibited to a degree that is only regarded as staining. This method allows the dyeing of polyester using disperse dyestuff and nylon with the usual dyestuff for nylon, and makes possible solid dyeing or multiple color dyeing.

Procedure :
  1. The substrate (polyester/nylon) is treated in a bath containing a carrier and pH-adjusting agent at 50°C for about 10 minutes.
  2. Dispersing agent and disperse dye solution are then added and the temperature is raised to 110°C to carry out dyeing under the high-temperature conditions for dyeing with the use of a carrier.
  3. Reduction cleaning is carried out after dyeing so that disperse dye staining on nylon can be stripped as much as possible.
  4. The dyeing of the nylon component is carried out under the usual dyeing conditions for 100% nylon.
  5. Fixing is carried out for improved wet fastness, if necessary.
Dyestuff Used

Disperse dyestuff
Selected are disperse dyestuffs which can dye well with the use of a carrier and produce minimum staining on nylon or display good fastness on nylon. SE-type dyestuffs are mainly selected for good adsorption to polyester and production of little staining on nylon.

The following are examples of recommended items.:
  • Sumikaron Yellow SE-4G
  • Sumikaron Orange SE-RPD
  • Sumikaron Rubine SE-RPD
  • Sumikaron Blue SE-RPD(N) Sumikaron Yellow E-RPD(E)
  • Sumikaron Red E-RPD(E)
  • Sumikaron Bordeaux SE-BL(A)
  • Sumikaron Blue S-BG200% Sumikaron Yellow SE-RPD
  • Suymikaron Red SE-RPD
  • Sumikaron Blue E-RPD(E)
  • Sumikaron Turq.Blue S-GL200%
  • 2-2. Dyestuff for nylon
  • Selected are acid or metal-complex acid dyestuffs which can dye nylon well and display superior fastness levels. The following are examples of items recommended.
  • Aminyl Yellow E-3GL
  • Aminyl Blue E-2GL
  • Aminyl Yellow FD-5GL
  • Aminyl Rubine FD-BL
  • Aminyl Cyanine 5R(N)
  • Lanyl Yellow G ex.cc.
  • Lanyl Brown R Aminyl Yellow E-RL
  • Suminol Fast Blue PR
  • Aminyl Yellow FD-3RL(N)
  • Aminyl Blue FD-GL
  • Aminyl Green F-3GL
  • Lanyl Orange R 200%
  • Lanyl Brown GR(N) Aminyl Red E-3BL
  • Aminyl Red FD-3BL(N)
  • Aminyl Navy FD-RL
  • Aminyl Black F-GL
  • Lanyl Red B
  • Lanyl Grey B
Dyeing auxiliary used Carrier
  • Carriers for polyester are used, mainly those which are methylnaphthalene-based.
  • Dispersing agents that produce superior effects at high temperatures are used rather than dispersing/leveling agents.
  • Reduction clearing agent
  • Nonionic/amphoteric-type surfactants for reduction clearing of 100% polyester are used.
  • Leveling agent for nylon
  • Leveling agents for 100% nylon are used.
  • Fixing agent for nylon.
  • Selection should be made mainly focusing on acid dye fixing properties.
The basic ideas of the technology above were made public by Sumitomo Chemical in the form of technical information, ‘Technology of multiple color dyeing for polyester/nylon union weaves’.

Some examples of general and spectacular applications of microfibres :
  1. Automotive application to improve air oil filtration, allowing improved engine performance and extended life;
  2. Perfect for asthma and allergy sufferers, removing dust mites without chemicals;
  3. Used extensively for hair transplantation, which works to conceal thinning hair.
  4. Microfibres are also used in sports applications such as sports wear, sports materials, etc.
  5. Microfibres are extensively used as a luxurious apparel wear.
  6. Microfibres as swing threads.
  7. Microfibres for production of synthetic leather.
  8. Use in the technical textile sector, as well as outside the clothing industry.
  9. Computer mouse pads, along which the mouse can slide easily, keeping the mouse ball clean at the same time.
  10. Polishing cloths for wafers and hard disks, acoustic insulation, high performance sound absorption panels and concert hall seat covers, among other products.
Economics aspects of microfibre processing and future prospects for microfibres :
The microfibre processing results in:
  1. 5-10% higher price than conventional fibres,
  2. pushing up yarn prices by 4%,
  3. reduction in twist by 5-10%, and
  4. 2% net increase in yarn cost.
The microfibres command high prices. The cost of producing microfibre is high in relation in common fibres, and microfibres cannot substitute conventional products without significant changes and adjustments to processing methods. This is likely to inhibit the development of microfibres in many textile and industrial applications. In the use of microfibre, the target concept has so far been ‘luxury’ rather than ‘utility’, and so the question of costs is perhaps of lesser importance. However, the size of the luxury market is not very large, and with so many companies rushing into the field of microfibre manufacturing, an inevitable price war may bring down the prices of new fibres, obliterating those that are unable to compete effectively. There is also an emphasis on blends, which may have advantages.

The question is what ratio of microfibres is required in blends to qualify the product for the microfibre level, and how the proportion of microfibres will cause to pay a premium on price. The industry will have to do the policy in this case.

Conclusion :
Microfibres are a completely new generation of ultra-fine synthetic yarns, which have not yet reached their peak of development. There are still a wide range of possibilities to be explored in the design, production, processing and use of this type of fibre. In addition to the common raw materials, PES, PA, and PAC, this specialty range will in future include other raw materials such as cellulose. ‘Micro denier’ yarns have a wider horizon of applications in India due to the traditional dress material designed and made by using natural fibres like cotton and silk. ‘Micro denier’ yarns have varied simulations of natural fibres, especially silk. We can foresee a brighter future in the Indian market due to the aesthetic properties of the fabrics made out of the yarns.

References :
  1. Polyester microfibre fabri,c by Prof. (Dr.) M.D. Teli.J.T.A. Mar-April 1999, 295-299.
  2. Microfibre – Production, Properties & Application, by S .K. Pal. Textile ASIA, Vol. 24, Jan. 1993, 53-58.
  3. Production of Microfibres, by Dr. (Ms.) S. Thiel J.T.A. Jan-Feb 1997, 213-216.
  4. Microfibres, by Prof. D.B. Ajgaonkar. M.M.T.T., Sept. 1992, 327-337.
  5. Micro Denier Yarns, by K. L. Vidur. NCM, March 1997, 9-16.
  6. Microfibres, The New Man-Made Fibre Image, by Jurg Rupp & Akira Yonenaga. I.T.B.Vol.46, (4th Issue) April 2000, 12-24.
 

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