US3500553A - Heat setting method and apparatus for polymeric fibers - Google Patents

Description

'. March 17, 1970 T. o. PATTON ETAL 3,500,553

HEAT SETTING METHOD AND APPARATUS FOR POLYMERIC FIBERS Filed April 1, 1968 4 Sheets-Sheet 1 DRAFTE R ROLLS 30; IO DP-(AFTER ROLLS HEAT-SET UNIT WATE R BATH Thomas O. Patton Sherwood M. Caldwell Samuel W. Bartholomew INVENTORS ATTORNEYS &

DRAFTER ROLLS &

$TEAM TUBE March 17, 1970 1', PATTQN ErAL 3,500,553

HEAT SETTING METHOD AND APPARATUS FOR POLYMERIC FIBERS Filed April 1, 1968 4 Sheets-Sheet 2 1 km m WIWN mwmw fi mmmm PM.B O SOI. G08 WU m m T% 552:6 op A /d-A-MJ ATTORNEYS March 17, 1970 T. O. PATTON ETA!- HEAT SETTING METHOD AND APPARATUS FOR POLYMERIC FIBERS Filed April 1, 1968 4 Sheets-Sheet 3 Thomas O. Pahon Sherwood M. Caldwell Samuel W. Bartholomew INVENTORS Ink/4%. JM 777% WQW ATTORNEYS March 17, 1970 1'. PATTON ETAL 3,500,553

HEAT SETTING METHOD AND APPARATUS FOR POLYMERIC FIBERS Filed April 1, 1968 4 Sheets-Sheet 4.

F 5 Thomas O. Potion Sherwood M. Caldwell Samuel W. Bartholomew ZNVENTORS ATTORNEYS United States Patent Int. Cl. F26b 3/00 US. C]. 3423 14 Claims ABSTRACT OF THE DISCLOSURE Method and apparatus for heat setting by high velocity heated air impingement upon and through the surfaces of a synthetic fiber band of at least 900,000 denier while holding the fiber band at a constant length until the fiber band cools to a dimensionally stable condition.

The present invention relates to a method and apparatus for heat setting synthetic fibers, and more particularly concerns a method and apparatus for heat setting a continuous length synthetic fiber band such as a fiber band of polymeric material while maintaining the fiber band at a constant length.

It is recognized that many fibers that are comprised of synthetic materials, such as might be produced by melt spinning or other methods, do not possess certain desirable properties such as strength, elongation, shrinkage or the like. It is conventional practice in the industry, therefore, to subject such synthetic fibers to various treatments including heating, stretching, setting and other steps for orienting the fibers and otherwise imparting to these fibers the desired properties.

It is also recognized practice to heat set synthetic materials, such as those including polyester fibers of polyethylene terephthalate, at a constant length in order to produce a high tenacity fiber. The Hebeler US. Patent No. 3,044,250, July 17, 1962, in column 8, beginning on line 60, discusses spun filaments of polyethylene terephthalate polymer that are combined into a tow of about 50,000 denier, 12,000 filaments, which may be held at a constant length while it passes through an oven. One production method for high tenacity fiber, when it is to be used as staple fiber in blends with cotton or other material, includes spinning a molten polymer into continuous length fibers, drawing the fibers, heat setting the fibers while maintaining the fiber at constant length, then crimping, lubricating and cutting the continuous length fibers into the desired staple lengths. One method in general use for heat setting while maintaining the fiber at constant length involves passing the continuous length fibers in the form of a band over a series of heated rolls; another method involves passing the continuous length fibers over a series of perforated drums through which hot air is blown. An example of the use of perforated drums for heat setting filamentary tow is best disclosed and described in the Clapp et al. US. Patent No. 3,177,555, Apr. 13, 1965.

The use of the above-mentioned heated rolls increases operating and equipment fabrication costs because rotary joints or slip rings must be provided for use with such rolls. These costs are in addition to the higher fabrication costs for the heated rolls themselves.

The above-mentioned perforated drums or rolls are also expensive, although not as expensive as heated rolls; but the expense difference fades away in time because perforated rolls are subject to frequent replacement due to eventual collapse of the inherently weaker thin outer shell of the perforated roll. The reason for the collapse is due to the tremendous pressure exerted by a continuous 3,500,553 Patented Mar. 17, 1970 length filament band that may be on the order of several hundred thousand denier or more.

The purpose of either of the roll systems mentioned above is to evaporate from the fiber band the moisture that is received during the preceding operating stages, such as the water bath, and then bring the fiber band up to the desired temperature for heat setting; the desired temperature is usually such that cannot be readily obtained unless the moisture has been evaporated so that the fiber band is bone-dry. In other words, synthetic fiber such as polyethylene terephthalate cannot be properly heat treated until the fiber is brought up to temperature of about 200 C. and held at that temperature for about five seconds.

What is critically important, however, is that the fiber band be heated uniformly. Uniform heating is required to assure uniform-dye acceptance by the fiber. In the heated roll method, certain factors are deterrents to ideal uniform heating of the fiber band. One factor is that the surface portion of the band on the side opposite from the surface portion that is in contact with the heated roll may be exposed to prevailing room temperatures, and the surface portion of the band that is in contact with the roll will become more heated than the outer surface portion; another factor is the interval, although seemingly slight, between the time the band leaves one heated roll until it reaches the next heated roll.

It is also desirable from the economic standpoint to process as much fiber as possible in order to derive optimum use of the capital equipment and the time the equipment is in operation. The size of the fiber band that can be heat set at one time depends on the capability of the equipment to evaporate the moisture present on the fibers of the band and to bring the fibers up to temperature as rapidly as possible while striving at the same time for uniform heating. It is not economically practical to bring only part of the fibers of the band up to temperature while other fibers in the band remain below the desired temperature range because these fibers are later processed in staple length form by the yarn manufacturer and if the staple fibers do not have a uniform dye acceptance, the resulting product is not a desirable quality product that has useful sale value.

It will thus be appreciated that the more uniform heat set staple fibers that can be produced in the same given time the lower the costs of such production. Uniform heat treatment further avoids carbonized deposits of yarn finish on the heated contact surfaces, and provides a dimensionally stable fiber.

One of the objects of the invention, therefore, is to provide an improved method and apparatus for more economically and efficiently, uniformly heat setting a fiber band of 900,000 denier and higher at speeds of about meters per minute and higher.

Another object is to provide an improved method of heat setting a fiber band of synthetic material, such as polyester material of polyethylene terephthalate, by directing high velocity heated air to impinge upon and through, and along substantially the width and length of the fiber band while maintaining the fiber band at a constant length.

Still another object is to provide an improved heat setting appartaus for a synthetic fiber band, such as a fiber band of polyethylene terephthalate, in which apparatus and fiber band makes multiple passes in an oven over and around driven rolls and in a path between perforated ducts from which high velocity heated air impinges upon and through and substantially along the width and length of the fiber band and with the high velocity heated air being also directed into the nip between each of the driven rolls and the fiber band, and then the fiber band is drivingly pulled by rolls through a cooling water bath with the driving rolls in the oven and at the water bath co- FIG. 2a is a cross-sectionaltview taken along line l a2a of FIG. 3 showing theoven and to illustrate the nultiple passes of the fiber bandbetween tapered ducts, he driving 'rollsgand the fans for propelling high velocty heated air through the ducts; FIG. 2b is a continuation .of, thepath followed by the iberiband after it' leaves the oven shown'in FIG. 2a and llustrates the water bath and the pull-roll apparatus hrough which the fiber band passes;

FIG. 3 is a cross-sectional view taken along line 33 )f FIG. 2a and illustrates the position of the fans relative o the heating coils and the ductsand the flow of the ieated air from the fans to the ducts; and

FIG. 4 is a perspective enlarged view of a portion of he ducts without the surrounding oven structure and ilustrates the relation of the multiple perforations and the lucts to the fiber band passing between adjacent ducts.

FIG. 5 is an enlarged perspective view taken along line i5 in FIG. 2a illustrating the air jet arrangement that eads from one of the tapered ducts for directing a heated )last of air into the nip formed between the fiber band 1nd the driven roll.

The arrangement of the different apparatus illustrated n FIG. 1 may be modified in whatever manner that is :uitable for the particular type of synthetic material being :rocessed. This arrangement is only illustrated to show hat the fiber band is being drafted and passes through tome units, such as the first illustrated water bath and he steam tube, wherein the band picks up the moisture hat subsequently must be evaporated before the fiber )and can be brought to the desired heat setting tempera- The heat setting stage of the apparatus arrangement :onsists of an insulated cabinet or substantially enclosed )ven 10, the general interior of which is illustrated in nore detail in FIGS. 2a and 3; and preferably includes .he stage disclosed M12 in FIG. 2b and which includes 1 water bath 14 and the pull-rolls 16. One advantage of he enclosed oven is that it provides for more uniform heating of the fiber band since the fiber band is con- ;tantly in a single environment of heated air at the same :emperature ratherthan passing through zones of differant temperature.

Oven serves to evaporate the moisture present on the fiber band 18 and to bring the temperature of the fiber band to the desired heat treating temperature, which is approximately..200 C. for polyethylene terephthalate. The water bath v14 that follows the oven serves to cool the, heat set fiber band to a stabilized condition while the pull-rolls 16 cooperate with the driven rolls 20 that are in the. oven to, hold the fiber band 18 at a constant length until the fiber band becomes dimensionally stable at its heat set condition.

In reference to FIG. 1, the fiber band 18 is received from the melt spinning stage of the operation (not shown) and passes through a first set of drafter rolls22, through a. water bath 24, and then into a second set of drafter rolls 26. Following these stages thefiber band passes through a steam tube 28 in, which it is brought to a predetermined temperature in preparation for passing through still another set of drafterrolls 30 prior to the oven 10 and to the water bath 14 and pull-rolls 16 that follow the oven. The band upon being heat set to a stabilized condition passes on to a crimper (not shown) and to other operations which serve to process the hand. These other operations are not described herein because they are not considered to be part of this invention. The individual structures of the apparatus mentioned prior to entry of the fiber band into theoven are conventional and well-known in the industry, thus it is not deemed necessary to dwell upon the details of these structures which are only diagrammatically illustrated.

OVEN

In reference now to FIGS. 2a, 3 and 4 the cabinet or oven 10 is defined by insulated walls 32 that substantially enclose the space in and through which the fiber band 18 is brought up to the desired heat setting temperature. The oven is provided with two parallel pairs of driven rolls 20 that serve to support and guide the fiber band 18 as it passes into and out of the cabinet. One pair of the driven rolls. is closely adjacent the entrance 34' (FIG. 2a) of the oven, and the other pair is closely adjacent the exit 36 (FIG. 2a) of the oven. The entrance and exit are preferably adjustable so as to reduce the size of the openings as close as possible to the fiber band. Y

The driven rolls 20 are preferably fabricated of stainless steel that has been chrome plated and has thereafter been given a matte finish. The matte finish reduces surface contact between the rolls and the fiber band when the band is partly wrapped therearound as the band makes its multiple passage through the oven, and in combination with the air jets to be described cooperates to reduce the risk of roll 'wraps in a manner that will also be described. The driven rolls are strongly constructed and supported so as to withstand the high tensional forces that will be exerted by fiber bands of 900,000 denier and higher, and must be capable of 'withstanding the added tensional forces that will result when the fiber band attempts to shrink as it is being brought up to the desired heat setting temperature.

A series of tapered ducts 38 are positioned within the oven so as to lie between the two pairs of driven rolls 20. The ducts in coomration with the driven rolls define paths for the fiber band as it makes multiple passes within the oven. The ducts are perforated with holes 40 in the manner illustrated in FIG. 4. It should be recognized, of course, that the number of ducts in an oven is a matter of choice dictated by factors such as length of space to be allotted to this particular stage of the overall fiber band processing operation, speed of the fiber band through the oven and the type of fiber material being processed. The particular duct arrangement illustrated is only one example of an arrangement that has proved to be economically efficient. The ducts are tapered so as to use the space in the particular oven illustrated more economically.

High velocity heated air is provided to the perforated tapered ducts 38 by means of four propeller fans 42; by heatingcoils 44 that may be heated by a medium such as superheated steam at a pressure of about 600 p.s.i.g. so that. the air temperature is about 220 C.; by intermediate ducts 46 that lead from the discharge side of each propeller fan to the tapered ducts 38; and by a partition 48 (FIG. 3) that extends the full .length inside the oven for the purpose of separating the discharge side of the propeller fans from the suction side. The oven may be provided at its ends with dampered air ports (not shown) connected by ducts to an exhaust blower (also not shown).

WATER BATH AND PULL-ROLLS The water bath 14 serves to quench or cool the fiber band after it leaves the oven. Filtered water flows into the bath at a temperature of about 40 C. The temperature of the Water is not critical as it is only considered desirable to reduce the temperature of the fiber band to at least C. so as to take tension off the band prior to the entry of the band to the crimper stage (not shown).

The pull-rolls 16 may be separately driven or driven from the same drive as that which drives the driven rolls 20 in the oven. These pull-rolls must be capable of withstanding the same high tensional forces as the driven rolls OPERATION When the fiber band 18 enters oven 10, the band may be 900,000 denier (about 655,200 filaments), more or less, is approximately 8 inches wide and A inch thick, and is moving ata speed of approximately 100 meters per minute. As a result of the stages preceding the oven, the temperature of the fiber band is about 50 C. and due to the preceding water bath and steam tube stages has a moisture content of approximately 20% I The fiber band 18 passes under guide roll 50 adjacent the entrance 34 of the oven and enters the oven to make a series of passes back and forth along the length of the oven until it leaves the oven through exit 36 and over guide roll 52 adajcent the exit- The fiber band'is ,held under tension in the oven by the friction of thesubstantially 180 wrap around each of the driven rolls 20, and this tension is maintained still further by the pull-rolls 16 adajacent the discharge side of the oven. Since each of the driven rolls 20 is being driven at the same surface speed the tensions encountered are not large enough to cause any slippage between the fiber band andthe driyen rolls. The fiber band is thus held at aconstant length from the time it enters the oven untilthe time it exists the pull-rolls 16, and while the fiber band 'is in the oven there is very little sag between the driven rolls 20 and the pull-rolls 16.

Suction is taken by the propeller fans 42 'so' that the air is drawn past the heating coils 44, past the fans and into the discharge duct 46, each discharge 'duct serving to direct the heated and now high velocity air at different entry points into the tapered ducts 38. The volume flow from the propeller fans, approximately 12,000 cubic feet per minute (c.f.m.), is such as to cause the heated air to be discharged through the perforated holes 40 in the tapered ducts 38 on the order of and in excess of 4200 feet per minute. It takes approximately 2 /2 passes of the fiber band in the oven before the moisture has been evaporated from the band and before the temperature of the band can be brought up to approximately 200 C. Thus after the moisture has been substantially evaporated from the band so that it achieves what for all practical purposes can be called a bone-dry condition the fiber band is then making multiple passes between adjacent ducts from which the high velocity heated air impinges and penetrates the fiber band from both of the large surface areas of the band, both across the width and substantially the length of the fiber band. The perforations 40 and the tapered ducts are substantially in alignment with the Width of the band so as' to bring to bear-a greater velocity of air on the fiber band.

A small amount of air, which may be on the order of about 1000 cubic feet per minute, is being removed continuously from withinthe oven by a blower (not shown) through ducts or openings at the end of the oven so as to maintain a slight negative pressure within, the oven. This negative pressure serves to prevent air from escaping through the entrance and exit of the oven. This air removal also serves to prevent the moisture content of the air within the oven from increasing by admitting outside air. a

As an example of the operation involved in the particular oven illustrated in the drawings, with the fiber band moving at the speed of about 100 meters per minute and at the air velocities and heat previously indicated, it takes approximately 13 seconds until the fiber band reaches what is called a bone-dry condition, which condition brings the fiber band to a temperature of approximately 100 C. Thereafter, it takes approximately 4 to 6 seconds to bring the temperature of the fiber band from about 100 C. to 195200 C. When this latter mentioned temperature is reached the fiber band is then held, at this temperature for the remainder of its passage through the oven which takes on the order of about 7 seconds.

A tapered jet 54 leading from a duct 38 and located adjacent the discharge side of each of the driven rolls 20 directs a high velocity stream of heated air from the ducts 38 into the nip between the driven roll and the fiber band leaving the roll. The tapered jet serves to reduce the risk of roll wraps by causing filaments that may have broken from the band and have started to adhere to one of the rolls to be blown from the roll in return to the fiber band. The jets 54 also serve as air knives for assisting in driving off moisture from the fiber band. The jets further serve, when the oven is initially activated, to raise the temperature of the driven rolls to the ambient operaing temperature of the oven so that the oven will attain effective operating conditions as soon as possible.

Since the tapered jets must of necessity be mounted closely to each of the driven rolls, damage could result to a jet should a large wrap occur on a roll. It may be' desirable, therefore, to provide for each of the driven rolls a wrap detector device 56. The detector device has a blade 58 mounted on a shaft 60, the blade pivots on the shaft as a wrap of predetermined size builds up and operates a limit switch (not shown) to shut down the operation of the oven.

It has been found that the combination of features that have heretofore been described have resulted in an effective fiber band processing operation where roll wraps within the oven have been minimized and where the quality of the staple fiber has been such as to have received uniform heating and thereby resulting in more uniform dye take-up. The resulting fiber staple length is of high tenacity and blends well with other fibers such as cotton, and processes well in mill equipment.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. An oven for heat setting a continuous length synthetic fiber band and comprising:

means defining a substantially enclosed cabinet,

driven rolls within the cabinet for guiding the fiber band in predetermined paths while in the cabinet;

enclosed air ducts disposed adjacent said predetermined paths and having wall surfaces defining therethrough multiple perforations, the extent and number of such perforations being substantially in alignment with the width of the fiber band to be heat set and with the length of the paths followed by such fiber band;

means for heating air;

means for propelling heated air into said air ducts and through the multiple perforations insaid wall surfaces at a velocity sufiicient to impinge and pass through said fiber band, the temperature of such heated air being sufficient to evaporate any mositure from the fiber band and to raise the temperature of the fiber band to its heat setting temperature; and

means adapted to direct heated air at high velocity from said air ducts into the nip that is formed between each driven roll and the fiber bandon the side of the roll where the fiber band is discharged from the driven roll.

2. An oven for heat setting a continuous length synthetic fiber band as defined in claim 1, and wherein each of said driven rolls are arranged in said oven so that the fiber band frictionally wraps around approximately of each said roll as the fiber band is guided by the rolls in said predetermined paths.

3. An oven for heat setting a continuous length synthetic fiber band as defined in claim 1 and wherein each of said driven rolls is made of stainless steel having a :hrome-plated-surface and provided'with a matte finish tdapted to reduce surface contact between each of the rolls and the fiber band as the fiber band comes into con- :act with the driven rolls. v

4. An oven for heat setting a continuous length syn thetic fiber. band as defined in claim 1, and wherein said Jeated air velocity from the multiple perforations in said air ducts and on tothe fiber'bandis on the order of 4200 feet per minute and the temperature, of. said heated air is about 220--C.

5. An oven for heat setting acontinuous length synthetic fibenband-as defined in claim.1, and further =comprising a roll wrap-detectordevicelocatedadjacent each thetic fiber band. as: defined in claim 1, and wherein said fiber band is of at least 900,000'denier, and isv approximately eight (8) inches wide and one-sixteenth (V inch thick- 4 1 7. An oven for heat setting a continuous length. synthetic fiber band as defined in claim 6-and wherein said synthetic fiber band is a polyester material of polyethylene terephthalate.

8. Apparatus for heat setting a continuous length synthetic fiber band at a constant length, and comprising:

means definitea substantially enclosed cabinet;

driven rolls within the cabinet for guiding the fiber band in predetermined paths while in the cabinet;

enclosed air ducts within the cabinet and disposed adjacent said predetermined paths and having wall surfaces defining therethrough multiple perforations, the extent and number of such perforations being substantially in alignment with the width of the fiber band to be heat set and with the length of the paths followed by such fiber band; means for heating air; a means for propelling heated air into said air ducts and through the multiple perforations in said wall surfaces at a velocity suflicient to impinge and pass through said fiber band, the temperature of such heated air being sufficient to evaporate any moisture from the fiber band and to raise the temperature of the fiber band to its heat setting temperature;

means adapted to direct heated air at high velocity from said air ducts into the nip that is formed between each driven roll and the fiber band on the side of the roll where the fiberband is discharged from the driven roll; and

roll means disposed along the path of and adapted-to guide the fiber band after the fiber band leaves'said cabinet, and around which roll means said fiber band is frictionally wrapped substantially 180; and means for driving said roll means and said driven roll means at the same peripheral speedso that said 8 i means for cooling the fiber band below its heat setting temperature.

10. Apparatus for heat setting a continuous length synthetic fiber band at a constant length as defined in claim 8, and wherein said fiber band is a polyester material of polyethylene terephthalate. 11; Apparatus'for heat setting acontinuous length sy'nthetic fiber bandat a constant length as defined in claim 10, and wherein said-fiber band is of at-least 900,000 denier, and is approximately eight (8) inches wide and one-sixteenth A inch thick.

12. Apparatus for heat setting a continuous length synthetic fiber band at a constant length as defined in claim 9 and wherein said means for cooling the fiber band below its heat setting temperature-is a water bath having a temperature sufficient to bring the temperature of said fiber band below its heat setting temperature. Y

v 13. The method-of heat setting a fiber band of polyester material that has moisture content of about 20% while-maintaining the-band. at constant length by the use of perforated ducts mounted in an enclosure and connected to a source ofheated air of the temperature of about 220 C. and having a volume flow of about 12,000 c.f.m. and by the further use in the enclosure of. driven rolls positioned at the ends of the perforated .ducts; said method comprising the steps of:

advancing said fiber band progressively through said enclosure with stretche s thereof trained around and about 180 of the surface of each of the driven rolls and with the stretches extending to and from the driven rolls passing in parallel spaced relation to and along the length of eachofthe perforated ducts; continuously discharging heated air at the rate of about 4200feet per minute from the perforations of each of the ducts upon and through the surfaces of the fiber band; continuously exhausting from the enclosure a predetermined amount of the heated air and the resulting moisture evaporated from the fiber band; and advancing said fiber band from said enclosure and cooling the fiberband below its heat setting temperature while continuing to hold'the fiberband at a constant length. 3 14. The method of heat setting a fiber band of'polyester material as defined in claim 13, and further comprising the step of maintaining the ambient temperature within the cabinet and surrounding the fiber band at' substantially the same temperature as that within the perforated ducts. v

References Cited UNITED STATES PATENTS LLOYD 1.. KING, Primary Examiner I Us. c1. X.R. 34-159 Hurxthal 34157 Eggs? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,500,555 D3... March 17, 197

Inventor) T. O'Brien Patton; S. M. Caldwell: S. W. Bartholomew It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[- Column 7, line 29, "definite" should be -defining. T

SIGNED AND SEALED JUL 2 1970 ISEAL) Atteat:

mm M- may I". E. mm. a. Atteating Officor 3011111195 of Patm

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