Method Of Bulking And Heat-setting Yarn

Abstract

A method of and an apparatus for the bulking (texturizing) and heat-setting of synthetic-resin yarn which utilizes the unique properties of a special fused-quartz radiant heater whose surface is generated by a line parallel to the movement of the filament past the heater. The filament may simply be passed between two or more spacedly juxtaposed heaters of this type, can be conveyed on a moving surface past the heater or may pass through an annular heater whose surface generatrices are parallel to the yarn.

Description

FIELD OF THE INVENTION

Our present invention relates to a method of an an apparatus for the bulking (texturizing) of synthetic-resin yarns and to a method of and an apparatus for the neat-setting of such yarns.

BACKGROUND OF THE INVENTION

In the production of synthetic-resin yarns, especially cellulosic yarns such as rayons, acetate yarns, polyamide yarns such as nylon and polyester yarns such as dacron or orlon, it is frequently desirable to increase the bulk of the yarn or to "texture" the yarn. The yarn, constituted of a multiplicity of filaments twisted together, can be bulked and texturized by subjecting it to heat at a temperature above ambient but generally below the flow temperature so that the plastic memory of the yarn becomes effective. The individual, previously smooth filaments are thereupon looped and the overall thickness of the yarn increases without an increase in weight. This bulking or texturizing improves the hand of the yarn and frequently its appearance, while providing a greater volume and hence improved insulating qualities when the yarn is used in blankets, garments and the like.

Furthermore, it is known to heat-set yarn to prevent raveling of the twisted strand and separation of the individual filaments, in conjunction with or apart from bulking, such heat-setting being frequently reqired in conjunction with a bulking or texturizing operation.

Numerous techniques have been provided heretofore, for the bulking, texturizing and heat-setting of multi-filament yarn composed of synthetic resins of the type mentioned above. In one hitherto-popular system, a hank or coil of the yarn is subjected to steam at the bulking temperature. This treatment has the disadvantage that the time required for thorough penetration of the hank or coil of yarn by steam at an elevated temperature is relatively long, that the coil of yarn resulting from the treatment is wet and must be dried for a relatively long period before further processing can take place, and that nonuniform treatment occurs. While attempts have been made to bulk or texturize and heat-set synthetic-resin yarn in a continuous manner, using radiant heat, these attempts have been uniformly unsuccessful in that either it was not possible to obtain satisfactory bulking or heat-setting, or whatever bulking or heat-setting did occur was nonuniform.

OBJECTS OF THE INVENTION

It is the principal object of the present invention to provide an improved method of bulking, texturizing and/or heat-setting yarn whereby the disadvantages enumerated above are obviated.

Yet another object of the invention is to provide an improved apparatus for bulking, texturizing and/or heat-setting yarns of the character described.

Still another object of the invention is to provide an improved method of and apparatus for treating yarns with heat in a continuous manner which provides high-quality bulking, texturizing and heat-setting without the drying problems and difficulties relating to nonuniformity that have characterized earlier systems.

SUMMARY OF THE INVENTION

Notwithstanding the failure of earlier attempts to bulk synthetic resin yarn by the use of dry heat, we have found, most surprisingly, that it is possible to effect a bulking of substantially any synthetic-resin yarn hitherto bulked, texturized or heat-set, by steam heat in a substantially continuous manner without the nonuniformities characteristic of earlier attempts at the use of dry heat for bulking purposes. More particularly, we have discovered that s specific type of radiant heater, namely one which emits heat substantially uniformly over the entire surface juxtaposed with the yarn from a layer of fused quartz having its surface defined by a generatrix parallel to the yarn. For reasons which are believed to be attributable to the wavelengths of the radiant energy emitted by fused-quartz, flat-surface, back-heated units, the yarn is heated through its entire cross-section to the bulking temperature uniformly and without wetting, and simultaneously is heat-set so that no further treatment is necessary. Infrared heaters, using other types of resistor heat in metal, quartz or glass, for example, have been tested for similar purposes and have been found to be unsatisfactory also regarding time of exposure. Consequently, it is believed that there is some phenomenon which permits the radiant block of fused quartz to heat the yarn uniformly and controlledly, without overheating and underheating, which effects penetrating heating even to the innermost filaments of the yarn and hence greater bulking than has been possible heretofore except perhaps with long-duration exposure to wet heat. Another advantage of the present system is the fact that dry heat is used and hence no separate drying step need be provided.

The radiant heater which is employed for the purpose of the present invention has an emission range (wavelength) of 2.8 microns to 50 microns and consists of a bed or block of fused quartz having a flat surface at least in the direction of movement of the yarn past the heater, the block of course being an emitter as well as a radiant energy filter and being provided, along its side turned away from the emitting surface, with electric resistance heating elements.

The invention can be carried out on substantially any yarn which is now subjected to bulking by other means. Such yarns are staple synthetic-fiber yarns, especially orlon, acrylan and dacron, although blends of these fibers with other synthetic and natural fibers may be used. To further increase the bulking characteristics, part of the yarn may be slacked-twisted, some of the filaments of the yarn may be crimped and at least some of the filaments are stretched substantially so that the radiant energy induces curling and looping as previously described. The high-bulk yarn resulting from the process of the present invention have the soft hand of wool or cashmere, are light-weight, and are warm because the curled fibers form air spaces within the thick yarn to provide insulation. As noted earlier, the passage of the yarn past a heating surface parallel to the yarn over the entire length of its path but extending transversely well beyond the yarn, e.g., as a flat heater or a cylindrical or tubular heated curved around the yarn, will result in heat-setting of the bulked yarn as well.

According to a feature of the present invention, therefore, the yarn to be bulked is passed upon a conveyor surface, preferably after being deposited in a zig-zag formation or a succession of overlapping loops thereon, beneath a planar-surface, fuse-quartz, flat-surface heater having a substantially uniform emission energy over the entire area of the heater. The conveyor surface may be provided downstream of the heater with a cooling station and we have found it to be advantageous to provide a relatively thin, e.g., polytetrafluoroethylene, foil conveyor which can pass over a chilled surface to effect the cooling.

Other configurations of the apparatus are also possible. For example, the heater may be tubular, i.e., may employ a block of fused quartz having a cylindrical internal surface which is equidistant from the yarn extending through this cylindrical block of fused quartz along the axis thereof. In this case, the resistive heating elements may be embedded in the outer or inner surface of the fused-quartz tube. Alternatively, the yarn may be passed between a pair of flat fused-quartz heaters as described.

Since the particular heater construction is vital to the invention, it should be noted that the flat or cylindrical fused-quartz bodies may be made by casting silica sand at an elevated temperature of almost 4,000.degree.F and in any event at a temperature at which the original crystalline structure is transformed into an amorphous body containing trapped air bubbles which render the body translucent. However, we may also compound the mass with a synthetic resin binder and then cast it at a substantially lower temperature. Preferably, the nature of the electric-resistance heaters (chromium-nickel alloys or alloys of aluminum, chromium, cobalt and iron or tungsten) are selected such that the principal emission wavelength corresponds to the principal absorption wavelength of the synthetic-resin yarn.

DESCRIPTION OF THE DRAWING

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description reference being made to the accompanying drawing in which:

FIG. 1 is a side-elevational view of a system for the bulking of yarn according to the present invention, partly in perspective;

FIG. 2 is a perspective diagrammatic view illustrating another embodiment of the invention; and

FIG. 3 is a cross-sectional view showing another aspect of this invention.

SPECIFIC DESCRIPTION

In FIG. 1 we have shown an apparatus for the bulking and heat-setting of a synthetic-resin yarn of the type described above, the apparatus comprising a conveyor band 10 of a heat-resistant synthetic-resin foil, e.g., polytetrafluoroethylene, passing about a pair of rollers 11 and 12, representing the supports for the endless conveyor which is driven by means not shown. At one end of the belt we provide means 13 for depositing the yarn 14 upon the upper surface of the conveyor in a zig-zag pattern adapted to increase the length of the yarn displaced through the bulking stage for a given speed of the conveyor. At the bulking station, the yarn passes beneath a fused-quartz, flat-surface radiant heater, generally represented at 15, whose radiating face is adjustably spaced from the layer of yarn and which may be of the type marketed under the name "SOLAR HEATER" by HUGO CAHNMAN ASSOCIATES, INC. This heater as shown in FIG. 3, basically comprises a body of fused-quartz having a planar surface juxtaposed with the yarn and channeled along its surface facing away from the yarn to receive electric-resistance heating elements. The radiant heat penetrates the yarn and bulks it in an extremely brief interval, generally ranging between 1 and 5 seconds, the yarn emerging from the heating station in a bulked and heat-set state. The conveyor band 10 then passes over a chilled plate upon which the yarn is cooled and a takeup means 17 is then provided for winding the block yarn in spools or forming hanks thereof.

In the embodiment of FIG. 2, the fused-quartz heater has a cylindrical configuration and consists of a cylindrical block of fused quartz as represented at 20 with a smooth surface 21 of cylindrical configuration coaxial with the yarn 22 passing centrally therethrough. In the outer surface of the heater, channels 23 are provided in which electric resistance elements 24 are received. While, in FIG. 2, the resistance heating elements are exposed, it should be understood that they usually are closed within a casing reaching around the edges of the block for safety. The yarn 25 emerging from the tubular heater is in the bulked condition. The treatment time for the yarn is here the same as in the apparatus of FIG. 1.

In FIG. 3 it can be seen that the yarn may also be passed at 30 between a pair of flat heaters 31 and 32, here shown in cross-section. The channels 33 receive the electric resistance heating elements 34 and a casing 35 is provided around the units.

SPECIFIC EXAMPLES

Example I

A polyester yarn was placed on a 12 inch wide conveyor in a serpentine fashion, with major loops being 10 inches long and the yarn spaced together to avoid overlap. Emitter temperature was set at a nominal 1,500.degree.F, with other temperatures possible but not optimum. The rectangular quartz heater as described was mounted 2 inches above the yarn. A four-second exposure was needed to bulk the yarn such that a 10 inch long piece (unbulked) was reduced to a 6.6 inch long piece, a net loss in length of one-third; with an approximate gain in width (bulk) of 3 to 5 fold. 4,320 watts was used.

The conveyor was operated at 15 ft. per minute with a heater having a length of 12 inches. With the serpentine layout, 600 ft./min. of yarn was processed. Exposures of 1 to 20 seconds, with corresponding modification of temperature can be used.

Example II

Acrylic and orlon synthetic yarns were bulked with two flat quartz heaters as described with the heated surfaces facing each other, and the product running between. The emitter temperature was 900.degree.F for the same linear speed and spacing as in Example I, except that each module was rated for 1,400 watts, with a total of 2,880 watts required for processing.

The yarn was bulked to maximum, which resulted in a 15-20 percent decrease in length over unbulked yarn. Diameter increases were noted from 3/16 inch unbulked to 3/8 inch diameter, bulked.

Claims

We claim:

1. A method of bulking and heat-setting a synthetic-resin a thermally bulkable yarn including a multiplicity of synthetic-resin filaments, comprising the steps of relatively displacing said yarn along a transport path by depositing said yarn in a back-and-forth serpentine pattern upon a conveyor and advancing said conveyor along said path, and directing radian heat at the yarn displaced along said transport path through a fused quartz body extending parallel to said path and substantially equidistant from the yarn over the entire length of the path at which said yarn is juxtaposed with said body to bulk and heat-set the yarn, said radiant heat being generated by resistive heaters behind said body, said yarn being juxtaposed with said body for a period of substantially 1 to 5 seconds.

2. The method defined in claim 1, further comprising the step of cooling the bulk yarn downstream from said body.

3. The method defined in claim 2 wherein said yarn is cooled by carrying it on a conveyor over a chilled plate.