US3667094A

US3667094A - Method for heat-setting of crimps of artificial filament tows

Info

Publication number: US3667094A
Application number: US40795A
Authority: US
Inventors: Masahide Yazawa
Original assignee: Polymer Processing Research Institute Ltd
Current assignee: Polymer Processing Research Institute Ltd
Priority date: 1970-05-27
Filing date: 1970-05-27
Publication date: 1972-06-06
Anticipated expiration: 1989-06-06

Abstract

The present invention provides a method of producing excellent crimped fibers, in which artificial fibers are subjected to mechanical crimping, enveloped in a crimped state in a wrapping under tension, and are passed through a high temperature pressurized saturated steam chamber at the annealing temperature of the fibers. The crimps are permanently fixed by the effect of moisture and heat under a lateral pressure. The resulting fibers, when made into an end product, have a high degree of crimp recovery upon reheating in the finishing process, even if the crimps have been straightened by processing in air before finishing operation.

Description

United States Patent [151 3,667,094 Yazawa 1 June 6, 1972 [54] METHOD FOR HEAT-SETTING 0F 3,644,145 7/1962 Tager et al ..28/l.6

CRIMPS 0F ARTIFICIAL FILAMENT 3,389,445 6/1968 Schreffler 3,408,713 1/1968 Parker ct al. ..28/l.6

TOWS

[72] Inventor: Masnhidl: Yuzawa. 'loyku. Japan [73] Assignee: Polymer Processing Research Institute Ltd., Tokyo, Japan [22] Filed: May 27, 1970 [2]] App]. No.: 40,795

[52] US. Cl.. ..28/72.l4

[51] Int. Cl ..D02g 1/12 [58] Field ofSearch ..28/1.6, 1.7, 72.14

[56] References Cited UNITED STATES PATENTS 2,997,747 8/1961 Russo et a] ..28/1.6 3,000,059 9/1961 Russo et a] ..28/l.7 X

Primary Examiner-lmuis K. Rimrodt Attorney-James E. Armstrong and Ronald S. Cornell ABSTRACT finishing process, even if the crimps have been straightened by 7 processing in air before finishing operation.

5 Clains, 5 Drawing Figures PATENTEDJUN 6 I972 SHEET 10F 3 FIG.

FIG. lb

PATENTEBJun 6 I972 SHEEI 2 BF 3 FIG. 3

PA'TENTEDJun 6 I972 SHEET 30F 3 FIG. 4

METHOD FOR HEAT-SETTING OF CRIMPS OF ARTIFICIAL FILAMENT TOWS BACKGROUND OF THE INVENTION Filament tows or yarns of artificial fibers made of various kinds of polymers are now on the market. The heat resistance after these polymers have been formed into fibers varies according to the kind of polymer. In general, filament tows or yarns of artificial fibers are frequently subjected to a heat treatment or an annealing process in order to make the quality unifonn and to improve the heat resistance. However, in the case of regenerated cellulose fibers, even in the case of heating in the presence of water, which serves to swell the fibers, it is necessary to perform a saturated steam treatment at a high temperature of 180 to 200 C. and a high pressure of 9 to 14 kg/cm gage pressure with 25 to 40 percent by weight water, based on the weight of the fibers. Since the atmosphere of the heating chamber is saturated steam containing substantially no non-condensible gases, thepressure developed within the chamber will depend upon the temperature to which the filament tow is heated. (Reference: Japanese Pat. No. 474,880, publication No. 319/Showa 41.) The products on the market are generally those that have not undergone such a heat treatment or annealing process.

From the practical point of view, the highest temperature at which deterioration of the fibers caused by relaxation in molecular orientation at a given treatment temperature is negligible, is frequently called the heat resistance temperature of the fibers. The heat resistance of fibers of synthetic polymers in general differs to some extent according to the type of polymer, average degree of polymerization, degree of molecular orientation, temperature and time of the treatment, or whether or not the fiber has undergone a heat treatment. The heat resistance temperature is accepted as the optimum annealing temperature of the fiber.

For example, the heat resistance temperature for polyvinyl chloride fibers ranges from 1 to 1 C., and for modacryl fibers of 60 percent vinylchloride and 40 percent acrylonitrile, from 120 to 125 C. As for acrylic fibers containing more than 85 percent acrylonitrile copolymerized with another comonomer, the heat resistance decreases as the content of the comonomer increases. Thus, most acrylics on the market generally contain 5 to 7 percent comonomer, and their heat resistance in the presence of water is generally between 130 to 140 C. A 100 percent acrylonitrile polymer has a heat resistance of 160 to 180 C. even in the presence of water, and when dry it can be decomposed and carbonized without causing substantial relaxation of molecular orientation.

' The highest heat resistance in water of polyvinyl alcohol fiber even after heat treatment is about 100 C., and the heattreated fiber even after acetalization with formaldehyde shows a heat resistance in water of about 120 C. However, in a dry state it has a heat resistance of 210 to 220 C., whether or not it has been treated with formaldehyde.

The heat resistance of a copolymer fiber consisting of 85 percent vinylidene chloride and 15 percent vinyl chloride lies between 100 to 1 15 C.

The heat resistance of polyamide fibers differs according to their composition. For Nylon 6 it is from about 130 to 150 C. in the presence of water and about 180 to 190 C. in dry heat. The heat resistance of Nylon 66 is about 15 to C. higher than that of Nylon 6.

The heat resistance of polyethylene terephthalate fiber in the presence of water is about 160 C. and 175 to 200 C., in dry heat, that of high density polyethylene fiber is 120 to 125 C., and that of polypropylene fiber is 145 to 150 C. As for these olefinic fibers, no difference between the heat resistance in the dry and wet states is observed.

It is impossible to heat-set a mass of fibers evenly in a short period of time by a dry heat method whether it is done by dry hot air or by contact conduction with a heated surface. Disadvantages of the dry heat method are well known in the literature. Dry hot air, moreover, oftencauses oxidation of fibers,

and dyed fibers change colors at high temperatures. Up to this time, the dry heat method is only used in heat setting of twists of undyed fine filament yarns.

For a tow of several hundred thousand denier, crimping of polyester fibers is carried out only by the stufi'er box method with steam up to C. Continuous heat setting of fiber crimps by means of steam at a high temperature and pressure has never been performed. As for crimp setting of acrylic fibers, the tow is crimped in a stufier box, and about 50 to 100 kg of the crimped tow, gathered in mass, are heat-treated with saturated steam in a batch-type autoclave. In this process, if the tow is packed so tightly as to press each fiber fimily, the steam cannot penetrate into the core of the fiber mass, and thus it is not evenly heated. In addition, if the fibers are not subjected to heat treatment in order to be contracted 20 to 23 percent of the length, they do not become fibers of practical use, because of low knot strength and susceptibility to fibrillation. In practical operation, however, they are stufl'ed loosely in the autoclave so as to have as low a density as possible to allow contraction. Further, they are heat-treated with repeated treatments applying vacuum followed by steaming, and the practical temperature for the heat treatment is often lower than the optimum temperature by 5. to 8 C., as explained hereinunder in details.

Since a part of the crimps are not pressed by' some means or others, the strain once given at the time of crimping returns by heat to the previous non-crimped state. This kind of phenomenon is well-known as plastic memory". The crimps of fibers in the lower part remain as they are, due to the pressure imposed upon them by the weight of fibers from the upper part. However, since the buckled parts of the fibers in the upper part of the mass are not pressed firmly, the crimps are apt to be straightened and their molecular orientatini is not rearranged, resulting in the failure of firm fixation of crimped state. Accordingly, for crimp setting, the process mentioned above, is inadequate. Since the fibers at the bottom of the autoclave are pressed by the weight from above, the relax annealing of 20 to 23 percent contraction is not able to occur. The fibers at the upper part are, however, free enough for contraction, but the crimp setting is insufficient. As the fibers at the bottom are not free for contraction, the crimpsetting may become better to some degree after a sufficiently high temperature heat treatment. But under these conditions due to the difference of contraction in yarious layers of fibers, variation in physical properties and unevenness in dyeing occur. Accordingly, although a temperature about 135 C. is the optimum temperature for heat treatment of acrylic fibers, as a practical procedure, heat treatment at the less desirable temperature of to 128 C. is used. Thus, the greatest disadvantages of acrylic fibers that are subjected to batch-type autoclave heat treatment are unevenness in contraction and unevenness in quality caused by heating of the fibers at temperatures insufi'icient for optimum heat treating, namely, crimp setting.

SUMll/IARY OF THE INVENTION The present invention provides a method of heat setting of crimps, wherein crimps are applied to fibers gathered in a tow form including a tow and yarns gathered in a tow form (hereinunder denoted as a tow for simplicity) mechanically, for example by means of a stufier box before or after a bleaching or dyeing process, and the tow is thereafter introduced into a heating chamber of saturated steam wherein the tow is permanently crimped. Before introducing into a heating chamber the tow is enveloped in a wrapping in a tapered guide conduit, the tow being fed in excess to the wrapping so that the tow may have crimps at least to an extent corresponding to the crimping ratio of the tow plus the shrinkage of the tow during subsequent heat treatment. During the wrapping operation the tow is increased in density by the tapering of the conduit, the outlet of which is substantially elliptical in shape. The tow is then introduced into a pressurized heating chamber containing saturated steam without substan- "tially any non-condensible gases and heated at the heat resistance temperature of the fibers, the temperature of which differs according to the particular fibers as previously explained. In the heating chamber a lateral pressure is applied to the tow by the tension of the wrapping; by sliding the wrapped tow over fixed bars or curved surfaces arranged in the heating chamber; by changing the running direction of the tow on rollers; by pressing the tow between rollers; or by a suitable combination of these means. While under tension the tow is subjected to moisture at a high temperature and pressure to set the bends and crimps by heat, and is drawn out into the atmosphere where the crimped tow is separated from the wrapping. The tow is subsequently processed and the wrapping is reused as required. The heat-fixed crimps of the treated filament tow are stable and durable, possessing an excellent crimp recovery upon reheating even if the crimps are straightened during subsequent processing.

DETAILED DESCRIPTION I In order to set crimps, it is necessary to rearrange the molecules so that the distorted molecular orientation at the buckled parts of the crimped fibers can be stabilized in the buckled state. If a sufficiently strong lateral pressure is not applied to the crimps, even if they are heated at a high temperature, the crimps are apt to vanish, remain unstable and are not firmly fixed. Moreover, if such crimps are straightened in subsequent processing, the degree of crimp recovery is low.

Use of high pressure steam at a high temperature lowers the optimum treating temperature by 20 to 50 C. in comparison with that required in dry heat process, because the moisture serves as a softening agent or plasticizer for fibers that have a certain hydrophylic property. Thus, saturated steam is an ideal heating medium for fibers because it facilitates even heating in a short period of time at a lower processing temperature.

In this invention the crimped parts of the fibers are sub jected to a sufficiently strong lateralpressure and fibers in the form of a thick tow are passed continuously into a heating chamber of saturated steam at a high pressure and a high temperature. At this time, the softening point and the treating temperature for the fibers in most cases are lowered by moisture because it acts as a softening agent. The method of this invention enables a continuous and uniform processing operation in which the treating temperature used is higher by about C. than that of the conventional batch-type autoclave method. Also, according to the new method, the required treating period is less than 60 seconds, including heating up time of the wrapped tow. The resulting products are of uniform physical properties because of the perfect crimp setting resulting from uniform heat treatment at a uniform temperature. A characteristic of this invention consists in its ideal practice of permanent crimp setting, because an ideal even heat treatment is only possible when it is done within the range of i 1 to 2 C. of the optimum temperature, namely, the heat resistance temperature of the particular fiber being treated so far as the other conditions, such as the lateral pressure imposed upon fibers, are maintained almost constant throughout the whole length of the tow.

When a crimped tow, enveloped in and guided by a wrapping under tension, travels a zigzag course on fixed bars in the pressurized heating chamber, the tension of the wrapping lying on the outer side of the wrapped tow becomes greater than that of the inner one which contacts with the bars. Thus the fibers enveloped in the wrapping receive a lateral pressure from the outside wrapping and are pressed onto the bars. Similar phenomenon is seen, when the wrapped tow changes its running course on a roller. In this case, the lateral pressure increases as the difference in tension and the pulling tension imposed upon wrappings for passing through the heating chamber increase, and when it turns along rollers or bars, or it is passed between rollers, the lateral pressure is evenly applied to each fiber. It is possible with this invention to attain the molecular re-orientation at the buckled parts of the fibers, because it is possible to apply an outer lateral pressure to the crimped parts of enveloped fibers through the wrapping using at the same time the plasticizing effect of pressurized steam at the optimum temperature. Thus, pemtanent fixation of mechanically given crimps has been achieved for the first time with this invention. Since fibers pass continuously in fon'n of a tow in saturated steam at the optimum temperature, the period of time required to heat evenly through to the core of the tow is only about 20 to seconds. Comparing this with the batch-type autoclave method in which one operation period requires more than 30 minutes (with repetition of steps: evacuation pressurized steam charge evacuation pressurized steam charge evacuation etc. excluding the time for charging and discharging the tow, the method of this invention provides much greater speed and efficiency, and the required apparatus can be made in amore compact form and at a lower cost.

BRIEF DESCRIPTION, OF THE DRAWINGS In FIG. 1a is shown a series of apparatus, in which a filament tow which has been spread in flat to have almost an uniform thickness is passed through a steam chamber at atmospheric pressure, and is crimped by means of a stuffer box. The crimped tow of controlled crimping is sent into a tapered guide conduit, through which'a wrapping to envelop the tow passes under a tension. While the tow is being enveloped by the wrapping, the density of the filament tow is increased at the outlet side of the conduit.

In FIG. 1b is shown the manner in which the crimped tow is enveloped to the extent of 1% times of its circumference by the wrapping, which is maintained under tension, and folded in U-shape for easy passing through pressure seals shown in FIG. 2 and FIG. 4.

In FIG. 2 is shown an apparatus, in which the wrapped tow is introduced into a high temperature pressurized saturated steam chamber through a narrow valve-controlled pipe at the inlet side. The tow is shifted sideways on rollers having axes which incline to each other as shown in FIG. 3, while enveloped by the wrapping under tension. The'tow is subjected to a strong lateral pressure from the roller surfaces, while it changes its direction, and it is drawn out into the air through a narrow pipe having multiple valves.

In FIG. 4 is shown an apparatus for the practice of this invention, in which the wrapped tow under tension runs continuously over the surfaces of rollers which are positioned and arranged in a heating chamber. T

DETAILED DESCRIPTIGN OF THE DRAWINGS In FIG. 1a an uncrimped tow 1 passes between the first pinch rollers 2, 2', and over guide bar 3, and is fed vertically into steam chamber 4 at a temperature of approximately C. under tension by which the tow may be stretched as much as 3 to 5 percent between the first pinch rollers 2, 2' and the second pinch rollers 5, 5', while care-is taken so that condensed water does not contact with the tow. The tow is then passed between guide rollers 6, 7, and 8 and then passes

pinch rollers

9, 9 and is pressed into stuffer box 10, within which it is folded and crimped. Stuffer box 10 is rectangular in section, and is constructed such that its bottomplate can be moved up and down at a predetermined pressure. Crimped tow ll, pushed out from stufier box 10, is received by .l-shaped slant conduit 12, slides in a downward direction, and is accumulated at the bottom of the conduit. Even if the crimped tow is pushed out inconstantly at an indefinite speed, the accumulated tow at the bottom of conduit 12 serves as a buffer zone and provides a constant speed supply for subsequent processing. The crimped tow is pulled by the travel of the wrapping, passes over guide bar 13, and while it passes through tapered guide conduit 14 for' application of the wrappings, it is shaped so that both sideends of the wrapping are overlapped like the front side of a Japanese kimono,as

shown in of FIG. 1b in which the tow is enveloped in the wrapping to the extent of one and a half times. At this time wrapping 15 is subjected to tension by the difference of peripheral speeds between

pinch rollers

16, 16 and 17, 17'. In addition, the guide conduit 14 tapers into a small section at its outlet so the crimped tow is tightly enveloped in the wrapping. When it is necessary to supply more crimped tow into the wrapping, it is possible with the use of tongue-shaped blade 18 having projected parts (not shown) on its lower side which push the tow forward by frictional contact with the fiber during forward travel of the blade and slide over the fibers on return travel. By regulating the amplitude and the number of reciprocating motion of the blade, a desired increase in supply is possible. Tow 19, enveloped in wrapping 15, is then introduced into a pressurized steam chamber through a narrow pressure-sealing tube having a circular or elliptical cross section. At this time the tow cannot escape from the wrapping if the overlapped part of the wrapping is bent inwardly as shown in 19, 19' ofFIG. 1b.

FIG. 2 shows a high pressure steam chamber for high temperature crimp setting of a wrapped fiber bundle. Wrapped fiber bundle 19 is introduced into saturated steam chamber 23, through pinch rollers 20, 20' and orifice-22 with tapered inlet pipe, the degree of orifice opening being controlled by valve 21.

As shown in FIG. 3 the tow shifts sideways successively on a pair of driving

rollers

24, 25, the axes of which incline somewhat toward each other.

After a prescribed period of time of travel in the chamber 23 (in most cases a period less than 1 minute is sufficient), the tow is drawn out into the atmosphere by

pinch rollers

32, 32 after passing through

valves

26, 27 and 28 which are attached to pressure-sealing narrow pipe 31 at the outlet side.

Narrow side pipes

29 and 30, each having a valve, are provided to leak steam directly into the air. This steam pressure sealing method and apparatus are described in my other patents (U.S. Pat. Nos. 2,954,687 and 3,213,470). For purposes ofthis invention the pressure-sealing method is not limited to the above one; thus any other suitable pressure sealing method may be used. Another effective method to use, for example, is one in which a narrow pipe 50 to 70 cm long having a variable cross section, that is, from a circle to an ellipse because of the elasticity of the material (for example, a polytetrafluoroethylene pipe laminated with a thin glass fiber fabric, or a thin elastic metal pipe), is held between two metal plates, and the distance between the plates is adjusted such that the cross section of the pipe orifice can be changed.

Steam is supplied through pipe 37, and condensed water is taken out through pipe 36 and a trap. Roof 33 may be provided, if necessary, to prevent condensed water from falling on the wrapped tow. Pipe 35 is a vent, and the pressure is indicated by gage 34.

When the axes of rollers 24 and have an inclination of a certain angle to each other, traverse shifting of the wrapped tow is satisfactorily accomplished as shown in FIG. 3. If there is concern that the tow may escape from the wrapping due to too great a distance between 24 and 25, guide conduits 38, 38' should be provided to bend the wrapped tow outwardly from the roller with a certain curvature so that the overlapped part of the wrapping can pass through the conduit by means of frictional contact. Another way of preventing escape of the tow from the wrapping is to provide a number of bars (not shown) on the path of the wrapped tow so that the tow can travel a zigzag course.

FIG. 4 shows an apparatus in which a number of rollers are vertically arranged, over which the wrapped tow moves successively. The crimps of crimped fibers are heat-set while the tow passes over these rollers. Wrapped tow 19 is introduced into pressurized steam chamber 43, passing through valve 41 having a tapered inlet guide pipe and through pressure sealing narrow pipe 42, and is fed to externally driven roller 44. The tow then moves upward, passing between three

free rollers

45, 46 and 47 moving on bearings in the chamber. The free rollers are light in weight so that the fibers do not stick together and are spaced a little apart from each other. The tow then runs onto externally-driven roller 48, and on three

light guide rollers

49, 50 and 51 similar to those described above. Afterwards it passes over externally driven roller 52, light guide roller 53 and roller 54, which is spaced at a certain distance from roller 53, and which is arranged at an angle with respect to the group of rollers 44 to 53 below. The tow changes its way downward and shifts sideways as much as the width of the wrapped tow before it is held again between

rollers

53 and 52. It runs successively downward on these rollers. When the total number of rollers is an odd number, the outlet end of the tow comes out at the opposite side from the inlet. The tow, afier passing through multiple-valved pressure sealing narrow pipe 55 at the outlet side, is drawn into the air by

pinch rollers

56, 56. Even if a large number of rollers are arranged and operated as described above, there is no danger that the wrapped tow may slip from the ends of rollers, provided that every other roller is fitted with flanges or ribs at the side ends. If the width of a wrapped tow is so wide as not to pennit the tow to run doubly on the rollers, several heating chambers constructed as shown in FIG. 4 may be arranged in series, and the tow, after being heat-treated for a required period of time (in most cases a period less than one minute) and passing through the pressure seal, is drawn out into the air. The wrapped tow, while being drawn out into the air after heat treatment, is separated from the wrapping.

The wrapping used in the invention is generally a product of a woven or knitted fabric, including a net or the like, irrespective of density of texture, and in form of a thin band or belt having a width sufficient to envelop within it a tow of crimped fibers of highest possible density and the preferable width is one and half times wider than the apparent circumference of the crimped tow to be heat-set. Useful wrappings also include those of the above type reinforced at both selvages with a narrow tape sewed on it, especially in the case of a net or knitted fabric.

If staple fibers cut from a crimped tow interfere with spinning process because of too many crimps, the crimped tow should be stretched between rollers while it is passed in a steam chamber at atmospheric pressure so that the residual crimps do not interfere with the spinning process. The residual crimps are temporarily fixed by cooling as they are and the tow is cut into fibers of a suitable length for spinning material.

Spun yarns made of the above-described fibers display latent ability to recover crimps applied at the time of setting, when treated with steam or water at to C. in a tention-free state. Accordingly, fabrics of high bulkinees may be obtained. Crimped tows obtained in accordance with the present invention, even if the crimps are straightened during tow spinning process, show a recovering property of crimps at the time of setting, when steamed at a temperature about 100 C. Accordingly, resulting fabrics become those of high bulkiness, when steamed at atmospheric pressure.

The wrapping, after separation from the tow, is returned to the tow enveloping device for reuse, after being turned over, spread and ironed on a hot roller to remove wrinkles.

Fibers gathered in a tow form applicable for this invention are not only filament tows or yarns as hereinbefore described, but also spun yarns, fibrillated fiber yarns from uniaxially stretched fiber-formable polymer film or other filamentary materials capable of being gathered in a tow form.

My invention is further illustrated by the following examples:

EXAMPLE 1 A regenerated cellulose fiber tow of 500,000 deniers was spun by the viscose method. A single filament of the tow was 1.5 deniers, had a strength of 3.5 g/d and an elongation of l5 percent. It was neutral or slightly arnmoniacally alkaline. The

having a bottom plate to which a certain air pressure was applied and rollers positioned on the inlet side 100 mm in width and 120 mm in diameter. The crimped tow had an apparent thickness of 800,000 deniers. It was introduced into a tapered guide conduit and was enveloped in a cotton cloth, 320 mm in width and 90 g/m in weight as in FIG. 1b, under tension between delivery rollers 16, 16' and

drawing rollers

17, 17. The wrapped tow, after being folded double with the overlapped part in the center, was introduced into an autoclave as shown in FIG. 2 to undergo staturated steam treatment for 45 seconds at a gage pressure of kg/cm and was drawn into the air. A part of the crimped tow, when separated from the wrapping, maintained a definite length in water at 100 C. for 30 minutes in a straightened state, but after removal of tension, the crimps recovered almost to the original state, showing very stable and strong recovery. Wrinkled parts of the wrapping were flattened afier strong ironing, but when dipped into hot water, they once more became wrinkled. Thus, when processed according to the invention, wrinkles of a cotton cloth were stably fixed, even against ironing.

A major part of the crimps of the tow were straightened under tension in a steam chamber at atmospheric pressure,

temporarily fixed in the straightened state by cooling and then the tow was cut into lengths of 50 mm. Cut fibers were used for blended and unblended spinning. An unblended spun yarn, when steamed at 100 C. in a tension-free state, become a high bulky yarn, which showed that the mechanically applied crimps were extremely stably fixed,'and the yarn had high resilience. The Laue spots in the X-ray diffraction photographs were fairly distinct, showing an increase in the crystalline area. The water absorption of the raw fibers was 70 to 72 percent" after dehydration by a certain centrifugal force, but absorption after heat treatment was lowered to 55 percent. This obviously shows a decrease in swelling properties. The wet Youngs modulus in water showed a high value. No substantial degradation of the polymer was observed. It was observed that the crimped fibers were suitable for blend spinning with synthetic staple fibers, in place of mercerized cotton.

EXAMPLE 2 An acrylic fiber (Cashimilon: Trade name of acrylic fiber manufactured by 'Asahi Kasei 'Kogyo Co. Ltd. Japan) 5,000,000denier tow consisting of single fibers of 3 deniers was padded to take up 1.3 percent-Cathilon Yellow 3 GLH, 0.5 percent Cathilon Red BLH, and 1.4 percent Cathilon Red BHH based on the weight of the fibers in the atmosphere.

Note; These names. are the trade name of dyestuffs supplied from Hodogaya Kagaku Kogyo Co. Ltd. After the tow was dyedbypassing through a high temperature and high pressure dyeing machine, maintained at 134 C. with saturated steam, it

'. was rinsed, oiled and dried. After that, it was heated under g/m' in weight, under tension between rollers l6, l6 and 17,

17' as in FIG. 1. While passing along on the bottom of guide conduit 14, the crimped tow, 100 mm in width, was enveloped in the wrapping to the extent of 1% times. The wrapped plateshaped tow, drawn out by pinch rollers l7, 17' from the extremityof the guide conduit, was folded double so that the overlapped part. of the wrapping could be enveloped in the center of the fold at the outlet of the conduit. The wrapped tow was then: passed through the equipment as shown in FIG. 2 and was heated for one minute at 135 C. under the tension of the wrapping. The resulting crimps were so stable and permanent that even if the crimps were straightened at a temperature about 100 C., the fibers recovered to the original crimped state immediately after relaxing the tension. The crimp stability was by far higher than that of a tow which was only heated at 100 C. and crimped in a stuffer box. The major part of the crimps of the heat-set crimped tow of this Example were temporarily fixed by cooling in a straightened state after the tow was passed through a steam chamber at C. It was then cut into staple fibers and spun into yarns. Knitted goods made of the yarns, after steaming, recovered crimps and became articles of high bulk and elegant touch.

EXAMPLE 3 then passed in such a manner that-the overlappedside could contact the surface of roller 44; mm in diameter and 150 mm in width, in the pressurized steam treatment chamber a shown'in FIG. 4. The tow was run upward successively from roller 44 to roller 54, and when the tow was returned from roller 54 to roller 53, it was shified aside as much as 75 mm. It was run again successively downward on these rollers and was drawn in the air through a narrow pipe having pressure sealing valves. In this case, the temperature of the saturated steam was C., and the heat treatment period for the wrapped tow was 45 seconds. The wrapped tow from the steam chamber was then separated from the wrapping. The tow was further processed, and the wrapping, after removal of the wrinkles and ironing on hot rollers, was-reused as tow wrapping at the inlet side.

Single fibers of the tow thus obtained became 3.5 deniers thick due to heat shrinkage during the heat treatment. The crimps were extremely stably set. The crimps could be easily stretched under tension in hot water at 100 C., but in a relaxed state after removal of tension, they recovered to the original crimped stated.

Excessively stabilized crimps of stable fibers for the use of spinning material interfere with the spinning process, resulting in the fonnation of nap yarns. Therefore, a tow of excessive crimps was passed through a steam chamber of 95C., and after the major part of the crimps were staretched and temporarily fixed by cooling in the stretched state, the tow was cut into staples. After spinning, weaving or knitting, the products were heated in a tension-free state to recover the crimps that were fixed at 160 C. Bulky products were obtained.

' EXAMPLE 4 900 polyethylenetelephthate yarns, each of which consisted of 25 filaments of 3 denier and had 100 twists per meter, were divided into 3 groups of 300 yarns each after partially warped.

After fixing the arranged order of the warped yarns at both the ends of each group by stitching obliquely with threads, the whole yarns lined in parallel were crimped with a stuffer box together with evenly distributed fine powder of talc to produce crimped yarns in a tow form of 100,000 denier, namely 50 percent excess supply was done.

The whole crimped yams in a tow form were enveloped in a cotton wrapping cloth 300 mm wide and having 35 gram weight per meter (about 300,000 denier cloth), travelling under a tension and the wrapped crimped yarns were introduced into a saturated steam chamber, as shown in FIG. 2, maintained at 160 C. and-subjected the wrapped crimped yarns to heat-treatment for 30 seconds.

Each yarn after heat-treatment became about 100 denier thick due to the 30 percent contraction during the heat-treat-' to that of the pressure sealing device) was kept at 12-15 percent and the fiber-density was raised gradually to percent and then up to 35 percent as the wrapped yarns were heated up by the leaking steam through the sealing device, otherwise the introducing resistance of the wrapped yams through the inlet sealing device became too large.

At the outlet pressure sealing device, the fiber density was kept constant at 30-35 percent during the heat treatment period of the fibers and the number of valves attached to the device was 3 or 4.

The wrapped yarns after heat-treated were drawn out into the atmosphere, seperated from the wrapping cloth and divided into three original groups, each of which was again divided into each single yarn followed by winding on each bobbin.

Advantageously, in this invention the degree of crimping can be controlled by suitably regulating the apparent deniers of the tow at the time when the wrapping envelopes the tow. In this way fibers crimped to an extent suitable for proper use can be obtained. of course, if a tow of crimped conjugate (composite) fibers is passed through a saturated steam chamber, after having been crimped with stuffer box and supplied in excess to the wrapping according to the method of this invention, such tow is also heated at the softening point of the fibers, that is, at the optimum temperature for annealing. Thus a combination of mechanically given crimps and conjugate crimps is fixed, or if supply in excess is slight, the mechanical crimps applied in the stuffer box method vanish and the generated conjugate crimps only are fixed. At any rate, it is an advantage of this invention that the extent of crimping is suitably controlled for permanent fixation. This results from heat setting at the highest possible temperature within the softening temperature range, that is, at the annealing point of the fibers, at which the strength of the fibers is not lowered to a measurable extent. Of course, since the fibers contract at the annealing point, the crimps will not remain after the heat treatment, unless a supply in excess corresponding to the sum of the contraction due to annealing plus apparent contraction due to crimping is done.

I claim:

l. A method for heat-setting of crimps on artificial fibers gathered in a tow form which have been previously crimped by mechanical means comprising:

1. enveloping said crimped fibers gathered in a tow form in a wrapping, while the fibers being fed lengthwise in excess to the wrapping so that the fibers enveloped in the wrapping can have crimps at least to an extent corresponding to the sum of the predetermined crimping ratio of the fibers plus the degree of contraction of fibers at the heat-treating temperature thereof,

2. increasing the density of the crimped fibers in the wrapping by mechanical compression,

3. introducing the compressed crimped fibers into and subjecting to travelling through a pressurized zone substantially containing only saturated steam at a predetermined temperature selected within the range of the heat resistance temperature of the fiber, while guided by the enveloping wrapping which is travelling under a tension,

4. heat-treating the wrapped fibers in said zone while subjecting the fibers to a sufliciently strong lateral pressure from the wrapping, lying on the outer side of the fibers, and travelling under a tension, along larger radii of curveture than that lying inner side of the fiber and travelling in contact with more than one curved surfaces 5. withdrawing the wrapping which envelopes the fibers therein from said zone and 6. separating the wrapping from the fibers.

2. A method of claim 1, in which the fibers gathered in a tow form is a tow consisting of a plurality of individual artificial filaments.

3. A method of claim 1, in which the fibers gathered in a tow form are scores of filament yarns arranged in a tow form.

4. A method of claim 1, in which increase of the density of crimped fibers in the wrapping is efiected by passing the fibers enveloped in the wrapping through a tapered conduit.

5. A method of claim 4, in which the supply of the crimped fibers in the wrapping is increased by applying a forward thrust to the crimped fibers at the inlet side of the tapered conduit, thereby forcing the fibers into the wrapping as it is received by the conduit.

UNITED STATES PATENT OFFECE CERTIFICATE OF CORREC'HGN Patent No. 3,667,094 Dated June 6, 1972 Invent0r(s) Masahide Yazawa rs in the above-identified patent It is certified the 1t error appea by corrected as shown below:

and that said Letters Patent are here Column 7, line 45, "5,000,000" should read 500,000

Signed and sealed this 19th day of December 1972.

(SEAL) Attest:

ROBERT GO'ITSCHALK EDWARD M.FLETCHER,JR.

Commissioner of-Patents Attesting Officer FORM po'wso USCOMM-DC 60876-P69 US. GOVERNMENT PRINTING OFFICE 1 1969 386"53.

Claims

1. A method for heat-setting of crimps on artificial fibers gathered in a tow form which have been previously crimped by mechanical means comprising: 1. enveloping said crimped fibers gathered in a tow form in a wrapping, while the fibers being fed lengthwise in excess to the wrapping so that the fibers enveloped in the wrapping can have crimps at least to an extent corresponding to the sum of the predetermined crimping ratio of the fibers plus the degree of contraction of fibers at the heat-treating temperature thereof, 2. increasing the density of the crimped fibers in the wrapping by mechanical compression, 3. introducing the compressed crimped fibers into and subjecting to travelling through a pressurized zone substantially containing only saturated steam at a predetermined temperature selected within the range of the heat resistance temperature of the fiber, while guided by the enveloping wrapping which is travelling under a tension, 4. heat-treating the wrapped fibers in said zone while subjecting the fibers to a sufficiently strong lateral pressure from the wrapping, lying on the outer side of the fibers, and travelling under a tension, along larger radii of curveture than that lying inner side of the fiber and travelling in contact with more than one curved surfaces 5. withdrawing the wrapping which envelopes the fibers therein from said zone and 6. separating the wrapping from the fibers.

4. heat-treating the wrapped fibers in said zone while subjecting the fibers to a sufficiently strong lateral pressure from the wrapping, lying on the outer side of the fibers, and travelling under a tension, along larger radii of curveture than that lying inner side of the fiber and travelling in contact with more than one curved surfaces

4. A method of claim 1, in which increase of the density of crimped fibers in the wrapping is effected by passing the fibers enveloped in the wrapping through a tapered conduit.

5. withdrawing the wrapping which envelopes the fibers therein from said zone and

6. separating the wrapping from the fibers.