Method of Chemical Treatment for Fibers

Abstract

Repeatable and reliable chemical treatment for loose fibers is achieved by spraying or immersing loose fibers in a chemical treatment bath, and continuously moving the soaked fibers through a continuous centrifuge. The continuous centrifuge controls the wet pickup of the chemical formulation on the fibers and assures a substantially even chemical distribution on the centrifuged fibers. The centrifuged fibers may be dried to fix the chemicals in the chemical formulation to the fibers and/or to remove water from the chemical formulation. Recycling of the chemical formulation from the continuous centrifuge allows for the process to be performed more economically and in a more environmentally friendly fashion.

Claims

1-16. (canceled)

17. A method for continuous chemical treatment of loose fibers, comprising the steps of: applying a chemical formulation to loose fibers as the loose fibers continuously move through a chemical treatment bath, wherein said step of applying is performed by one or more of spraying the chemical formulation on the loose fibers and soaking the loose fibers with the chemical formulation; continuously conveying said fibers through said chemical treatment bath; and then centrifuging with a continuous centrifuge said loose fibers with applied chemical formulation received from the chemical treatment bath to produce centrifuged loose fibers.

18. The method of claim 17 further comprising the step of squeezing the loose fibers prior to said step of centrifuging.

19. The method of claim 17 further comprising the step of drying the centrifuged fibers.

20. The method of claim 17 wherein the step of applying is performed by spraying the loose fibers with the chemical formulation.

21. The method of claim 17 wherein the step of applying is performed by immersing the loose fibers in the chemical formulation.

22. The method of claim 17 wherein said the step of using said continuous centrifuge produces loose fibers coated and/or impregnated with said chemical formulation.

23. The method of claim 17 further comprising the step of recycling chemical formulation from said continuous centrifuge to said chemical treatment bath.

24. The method of claim 17 further comprising the step of supplying a portion of said chemical formulation to said chemical treatment bath from a chemical formulation preparation tank.

25. The method of claim 17 wherein said step of holding is performed by holding said loose fibers to one or more conveyors.

Description

DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic flow diagram that shows a continuous chemical treatment system for loose fibers.

DETAILED DESCRIPTION

[0014] The process of the present invention is intended to produce chemical-treated fibers in the most efficient and economical way as well as to produce the fibers with uniform quality in terms of chemical distribution on the fibers. An exemplary process which exploits the present invention is illustrated schematically in FIG. 1.

[0015] Fibers are provided at the beginning of the process, for example as a bale form. The fibers can be natural fibers, man-made fibers, or combination of those. Natural fibers include, but are not limited to, cotton, ramie, coir, hemp, abaca, sisal, kapok, jute, flax, linen, kenaf, coconut fiber, pineapple fiber, wool, cashmere, and silk. Man-made fibers include, but are not limited to, polyester, nylon, acrylics, acetate, polyolefins, melamin fibers, elastomeric fibers, polybenzimidazole, aramid fibers, polyimide fibers, modacrylics, polyphenylene sulfide fibers, oxidized PAN fiber, carbon fibers, novoloid fibers, manufactured cellulosic fibers (e.g., rayon, lyocell, bamboo fiber, tencel, and modal), and manufactured FR cellulosic fibers (e.g., Visil, Anti-fcell, Daiwabo's FR Corona fibers, Anti-frayon, Sniace's FR rayon, and Lenzing Fir).

[0016] A conventional fiber opener 10 can be used to open a chunk of compact fibers from a bale into a loose fiber form and spread the opened loose fibers 12 on a conveyer belt or other apparatus which carries the fibers to the next step of the process. A fine opener may be used for better opening of the fibers. A continuous layer of the opened loose fibers is moved into and through a treatment bath 14 containing a chemical formulation (one or more chemicals; both aqueous and non-aqueous formulations being a chemical formulation according to the invention; however, water alone (i.e., without one or more chemicals) not constituting a chemical formulation according to the invention) and the fibers are completely soaked by the chemical formulation to produce treated loose fibers. For the fibers that need a longer time to be wet, the chemical formulation may be sprayed on the fibers before immersing them into the chemical formulation in the treatment bath 14. Spraying may also occur after exit of the fibers from the immersion at the bath 14. For the fibers that are relatively easy to be wet, exposure to the chemical spray in the system may be enough, and immersion may not be required. In some embodiments, a spraying system may be installed at the treatment bath 14 and the chemical formulation is supplied either from the bath 14 or a chemical formulation preparation tank 20. When the spraying system is a part of the treatment bath 14, excess amounts of chemical formulation sprayed on the fibers can be automatically collected in the treatment bath 14.

[0017] During the chemical formulation treatment, the fibers preferably are stationary (i.e., fibers do not move freely in the chemical bath 14). One exemplary method to make fibers generally not to be floated or not to be tumbled in the treatment bath 14 is to utilize two perforated conveyer belts to hold fibers during the chemical treatment. In this case, the fibers are held between, for example, two perforated endless conveyer belts. Such a system prevents the fibers from floating in the bath 14. This is advantageous since lost fibers left in the bath 14 will cause process issues, such as clogging draining system and sticking inside parts of the treatment bath system. The treatment bath 14 preferably includes a temperature control system to provide a specified temperature when exposing the fibers to the chemical formulation. The specified temperature may be varied depending on the requirements of different chemical formulations.

[0018] The soaked, treated loose fibers obtained after immersion or spraying or both in the chemical treatment bath 14 are squeezed by passing through a pair of squeeze rolls to remove excess amounts of chemical formulation to prevent dripping of the chemical formulation from the fibers while the fibers move to next step of the process. Preferred wet pickup after the squeeze rolls is around 200300%. But it will vary depending on type of fibers. In an environmental friendly embodiment and cost saving, the squeezed chemical formulation is collected into the treatment bath 14 to be reused for the continuous treatment. For this purpose, the squeeze rolls may preferably be a part of the treatment bath 14 and may be located at the end of the treatment bath 14, so the squeezed chemical formulation is automatically collected into the bath 14.

[0019] Then the squeezed fibers are moved to a continuous centrifuge 16 to remove additional chemical formulation from the fibers, and to control chemical formulation wet pickup on the fibers and to achieve a substantially even chemical distribution within or on the surface of the fibers. At this step, a conventional fiber opener and fiber distributer may be used to supply better opened fibers and controlled amount of fibers to the continuous centrifuge. The centrifugation step controls the final wet pickup of the chemical formulation on the fibers. Preferred wet pickup after the centrifugation is below 100% and more preferably at 5080%, but the final target wet pickup can be varied depending on different type of fibers and their liquid absorption characteristics. For continuous centrifugation, the controlled amount of squeezed fibers is fed into an inlet of the centrifuge continuously and centrifuged fibers are released through an outlet of the centrifuge continuously. The centrifuged fibers released from the outlet of the centrifuge will have substantially even chemical distribution (e.g., a variance of the wet pickup of the chemical formulation of less than 10% from fiber to fiber) such that the fibers produced will have substantially uniform properties. The continuous centrifuge system may include a cyclone and a feeder whereby fibers released from the continuous centrifuge are transferred to a cyclone to remove air flow from the fibers such that at the feeder supply a uniform layer of chemical-treated loose fibers is provided to a dryer continuously.

[0020] During the continuous centrifugation, extracted chemical formulation from the fibers may be collected and continuously sent to the treatment bath 14 (or a chemical formulation preparation tank 20) for reuse. At the same time a fresh chemical formulation from one or more chemical formulation preparation tanks 20 can be continuously supplied to the treatment bath 14 to replenish the depleted amount of the chemical formulation by fiber treatment and to keep a same level of the chemical formulation in the bath 14.

[0021] The fibers released from the outlet of the continuous centrifuge 16 may be transferred to a conventional fiber dryer 18 continuously. This may be accomplished by first passing the released fibers from the centrifuge 16 through a cyclone and a feeder. A drying step advantageously removes residual water from the fibers and may assist in fixing chemicals on the fibers. The dried chemical-treated fibers may then be baled to be sent to further processes, such as yarn spinning or nonwoven production.

[0022] Exemplary chemicals which may be used for the treatment include but are not limited to softeners, hydrophilic agents, hydrophobic agents, water/oil repellents, anti-static agents, soil-release agents, spin finishes, flame retardants, antimicrobials, insect-repellents, UV absorbers, odor absorbers, fragrances, etc. In addition, a plurality of different chemicals (e.g., flame retardants and hydrophobic agents) or different types of chemicals within one category (e.g., two or more antimicrobials) could be used in the treatment.

[0023] A particular advantage of the present invention from prior art is that it permits continuous fiber treatment to be performed uniformly. That is, by utilizing a continuous centrifuge, the wet pickup of chemical formulation on the fibers is reliably and reproducibly controlled, This system and process provides for more precise control of wet pickup compared to squeezing system employed by the prior art. Also, the present invention does not require converting the fibers into a web or batt form as required in the prior art. That is, simply opened loose fibers can be treated with the system of the present invention.

[0024] While the present invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with considerable modification within the spirit and scope of the appended claims.