Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Microwave
Utility Patent
1999-06-21
2001-01-02
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Microwave
C028S219000, C028S220000, C264S491000, C264S492000, C425S174400, C425S445000
Utility Patent
active
06168747
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the production of synthetic polymeric material in filament form for use in fiber manufacture and, more particularly, to apparatus and methods for heatsetting such filamentary material, particularly polyethylene terephthalate (PET) materials commonly referred to as polyester.
In the conventional manufacture of synthetic yarns, a molten polymeric material is extruded in the form of multiple continuous filaments which, after quenching to cool the filaments, are gathered and transported longitudinally in a lengthwise co-extensive bundle commonly referred to as a tow. Particularly with polymeric materials such as PET, the tows are subjected to a subsequent drawing and heating operation to orient and heatset the molecular structure of each constituent filament in each tow.
A typical drawing and heatsetting operation involves transporting multiple tows in side-by-side relation sequentially through two or more drawstands operating at progressively greater driven speeds to exert a lengthwise stretching force on the tows and their individual filaments while traveling between the drawstands thereby performing a drawing to molecularly orient the individual filaments, followed by a calender structure having a series of heated rolls about which the tow travels peripherally in a sinuous path to be sufficiently heated to set the molecular orientation of the filaments. Normally, the tow is transported through a quench stand to be cooled immediately following the calender structure and is finally transported through a crimper, such as a so-called stuffer box, to impart texture and bulk to the individual filaments.
Tow drawing and heatsetting lines of the type above-described have proven to be reasonably effective and reliable for the intended purpose. However, as the fiber industry continually strives to improve efficiency and reduce manufacturing costs, much effort has been devoted to attempts to increase the number of filaments bundled in each tow and to increase the lineal traveling speed at which the filaments are processed through the drawing and heatsetting line, which presents particular difficulties and problems in construction of the apparatus within the line and in effectively accomplishing heatsetting of all of the constituent filaments in a tow.
In particular, it is not uncommon for a tow being processed through a conventional drawing and heatsetting line to have a cumulative denier of all of the constituent filaments in the tow on the order of five million denier. Polymeric materials generally, and PET in particular, exhibit a low thermal conductivity and, in a tow comprising collectively numerous individual fine denier filaments, the interstitial spaces between the individual filaments exacerbate the difficulty of transferring heat throughout the thickness of a tow. With calender rolls having the capability of only heating the tow surface in contact with the rolls, the applied heat penetrates relatively slowly through the thickness of the tow which, in turn, necessitates the provision of a sufficient number of successive calender rolls together with a sufficiently slow traveling speed to ensure that the entire thickness of the tow is uniformly heated.
To better promote more rapid heat transfer through a tow, it has become commonplace to construct calenders with cantilevered rolls to permit the spreading of the individual filaments of the tow in the form of a ribbon or band along the length of the roll.
These various factors not only increase significantly the capital investment necessary for a conventional drawing and heatsetting line, the processing lines of this type in current use nevertheless must operate at lower than desirable processing speeds in order to uniformly heatset all filaments within a tow.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an improved apparatus and method for calendering a traveling multi-filament tow to heat its individual filaments which will substantially improve the rate of heat transfer through the tow thickness and enable processing to be carried out at correspondingly increased traveling speeds of the tow. A more specific object of the present invention is to provide such improvements in calendering apparatus and methods which can be retrofitted to existing drawing and heating lines. A further object of the invention is to enable the construction and fabrication of a new generation of calendering equipment which, reduces the need for many or all of the calender rolls. Further objects, effects and advantages of the present invention will be apparent from the specification hereinafter provided.
Briefly summarized, the present invention achieves these objectives by providing a calendering apparatus and method for heating a traveling multi-filament tow which, in its most fundamental aspect, basically comprises electromagnetic radiation simultaneously applied in the direction of the traveling tow, such as by means of an electromagnetic radiation source arranged in opposed spaced facing relation to the tow.
Optionaly, the calendering apparatus and method utilizes a plurality of such heated rolls arranged relative to one another for travel of the tow in a sinuous path successively about the respective rolls, with an electromagnetic radiation source directed at the portion of each roll which is in peripheral engagement with the tow. The radiation source may produce electromagnetic waves in either of the infrared, radio or microwave spectrums, or possibly a combination thereof, although it is presently believed to be preferable to utilize infrared lamps associated with each roll in an arcuate arrangement generally conforming to the cylindrical periphery of each respective roll.
An embodiment of the present apparatus and method particularly adapted to be retrofitted to conventional calenders of the type described above would simply equip such calenders with suitable arcuate arrangements of infrared lamps adjacent one or more of the heated calender rolls of the apparatus. As an alternate embodiment, it is contemplated to provide a new form of calender apparatus and method utilizing no calendar rolls or a substantially reduced number of heated calender rolls (in comparison to conventional calenders), each of which may have associated therewith an arcuate arrangement of infrared lamps or other appropriate electromagnetic radiation source directed at the periphery of the respective roll, followed by one or more tunnels through which the tow is transported between opposing electromagnetic radiation sources, such as infrared lamps, to be further radiantly heated downstream of the calender rolls, if calender rolls are employed.
Fundamentally, this combination of calender rolls for surface heating of one side of a tow in conjunction with simultaneous electromagnetic radiant heating of the opposite side of the tow or using opposing electromagnetic radiant heating sources, enables the heating of the filaments in a tow at a rate on the order of twice that utilizing conventional surface heating of a tow by calender rolls alone and, in turn, correspondingly enables a given drawing and heating line to be operated at a lineal tow throughput speed on the order of twice that which is possible utilizing a conventional calender.
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Carlson, Jr. Charles David
Kuppe Johannes C.
Ledbetter Marshall
Reese Glen P.
Arteva North America S.a.r.l.
Clements Gregory N.
Tentoni Leo B.
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