US 3852948 A
Differentially shrinkable tow of continuous filaments in which the filaments vary longitudinally thereof in latent shrinkage characteristic between predetermined minimum and maximum limits. The tow is converted into staple fiber lengths and spun into yarn.
Description (OCR text may contain errors)
United States Patent Ruddell et a1.
YARNS, TOWS, AND FIBERS HAVING DIFFERENTIAL SI-IRINKABILITY Inventors: James Nelson Ruddell, 19 Glenroy Ave., Portadown; Herbert Alexander Conway Todd, 25 Coolsara Park, Lisburn, both of Northern Ireland Filed: Feb
Appl. No.: 346,870
Related US. Application Data Continuation-impart of Ser. No. 219,048, Aug. 23,
1962, Pat. No.
3 ,302,3 85 Continuation-impart of Ser. No. 176,455, Feb. 12, 1962, abandoned.
Foreign Application Priority Data Aug. 26, 1961 Northern Ireland 30850/61 Jan. 17, 1962 Northern Ireland 1796/62 Jan. 17, 1962 Northern Ireland 1797/62 May 25, 1962 Northern Ireland 20135/62 US. Cl. 57/140 R, 28/72.17, 57/140 BY,
57/157 MS, 161/172 Int. CL... D02g 3/24 Field of Search 57/34, 55.5, 157, 140;
28/1 C, 72 B, 72 F, 72.17; 161/170, 172,
[4 1 Dec. 10, 1974 Primary ExaminerJohn Petrakes Attorney, Agent, or Firm-William J. Daniel [5 7] ABSTRACT Differentially shrinkable tow of continuous filaments in which the filaments vary longitudinally thereof in latent shrinkage characteristic between predetermined minimum and maximum limits. The tow is converted into staple fiber lengths and spun into yarn.
14 Claims, 17 Drawing Figures PATENYEBM: 10 m4 SHEET 8 OF 6 Arm flue u YARNS, TOWS, AND FIBERS HAVING DIFFERENTIAL SHRINKABILITY This invention concerns the modification of filaments forming or capable of forming assemblies of filaments such as tows, slivers, yarns and fabrics and is a continuation-in-part of our co-pending application Ser. No. 219,048 filed 23rd Aug. 1962, now US. Pat. 3,302,385, itself a continuation-in-part of our copending application Ser. No. 176,455 filed 12th Feb. 1962, now abandoned.
The word filament is used herein, unless the context otherwise indicates, to mean any element having a length which is many times greater than any of its crosssectional dimensions and in particular textile filaments whether in the form of continuous filaments, staple fibres, or otherwise.
The broad object of the invention is to achieve new and improved effects in assemblies of filaments.
A more particular object of the invention is to achieve new or improved effects in assemblies of textile filaments such as tows, slivers, yarns and fabrics.
It is especially the object of the invention to produce from man-made filaments yarns which resemble closely in many of their physical characteristics, such as appearance and handle, and also in their processing characteristics, yarns made from natural materials such as wool.
Further objects of the invention are to provide suitable processes and apparatus for carrying out the foregoing objects.
The manner in which these and other objects not specifically mentioned hereinbefore are achieved will now be described.
According to the present invention a continuous process of simultaneously treating a plurality of filaments adapted to form an assembly of filamentous material comprises the step of variably modifying the ability of the filaments to shrink when subjected to further uniform treatment and so as to retain therein the modification pending such further treatment. The invention also extends to the products of such a process and to machines and apparatus for putting same into practice.
More particularly the invention comprises a continuous method of treating a tow of textile filaments which comprises the step of variably modifying the ability of the filaments to shrink when subjected to a further uniformly applied treatment and so as to retain therein the modification pending such further treatment, said modification varying cyclically along the length of the filaments, the cycle length being not less than 60 inches and not more than 1,600 inches, and the maximum shrinkage differential being at least percent. The particular usefulness of such a tow of filaments is manifested when converted into staple fibre, the mean staple length being such that 0z/2S is not less than 20 and not more than 100 (a being the cycle length and S the mean staple length), and the staple fibre into yarn, which is subsequently subjected to said further uniformly applied treatment either before or after fabrication. The yarn after treatment has many wool-like characteristics, For knitting yarn the maximum shrinkage differential is preferably between percent and 25 percent (in the region of percent being particularly desirable for polyacrylics) and for weaving yarn and carpet yarn, between 7.1/2 percent and 15 percent (in the region of 10 percent being particularly desirable for polyacrylics).
The process is especially useful when the tow is of polyacrylic filaments and there is considerable scope for variation of processing details within the scope indicated above, and'as will be apparent from examples set out hereinafter.
The invention also comprises a process in which the cycle length is equal to twice the staple length, the variability of the modification being either continuous or discontinuous.
According to a further process within the scope of the invention a process of producing a continuous filament bulked yarn includes the step of treating continuously and simultaneously as they are produced and in the absence of twist a plurality of continuous filaments, having the ability when heated to shrink substantially uniformly, variably to modify said ability of the filaments to shrink so as to retain therein the modification pending a subsequent uniform heat treatment.
The invention will now be described more specifically with reference to the accompanying drawings in which:
FIG. 1 is a diagrammatic representation of apparatus for converting a continuous filament tow into yarn according to the invention;
FIG. 2 is a diagrammatic representation of another apparatus for converting a continuous filament tow into yarn according to the invention; 5
FIG. 3 is a diagrammatic representation of yet another apparatus for converting a continuous filament tow into yarn according to the invention;
FIG. 4 is a diagrammatic representation of apparatus for producing continuous filament yarn according to the invention, especially adjacent the spinneret;
FIG. 5 is a diagrammatic representation of another form of apparatus for producing continuous filament yarn according to the invention especially adjacent the spinneret;
FIG. 6 is a diagrammatic representation of apparatus for producing staple fibre from continuous filament tow according to the invention;
FIG. 7 is a diagrammatic representation of apparatus for producing staple fibre from continuous filament tow according to the invention;
FIG. 8 is a diagrammatic representation of a filament assembly according to the invention wherein a plurality of filaments are given a longitudinal variation in a characteristic thereof, for instance shrinkage, the periodicity of the variation being the same for all filaments in the assembly and the variation being in phase for all filaments in the assembly;
FIG. 9 is a view similar to FIG. 8 except that the characteristic within each filament is maintained constant, the variation thereof being between filaments in the assembly;
FIG. 10 is another view similar to FIG. 8 except that the periodicity of the variation changes from filament to filament;
FIG. 11 is an additional view similar to FIG. 8 except that an intermediate filament has its characteristic altered in constant fashion, while that of the filaments on either side thereof is periodically modified and in staggered relationship;
FIG. 12 is a view similar to FIG. 11, except that the periodicity of the variation is considerably lengthened and the variations are less abrupt;
FIG. 13 is an enlarged cross-sectional diagram of a conventional unbulked yarn from the prior art;
FIG. 14 is a view similar to FIG. 13 of a conventional high bulk yarn of the prior art;
FIG. 15 is a view similar to FIGS. 13 and 14 of a typical yarn formed according to the invention;
FIG. 16 is a diagrammatic elevation of the conventional high bulk yarn of FIG. 14; and
FIG. 17 is a view similar to FIG. 16 of a typical yarn produced according to the present invention.
In one method of processing a continuous filament tow of high shrinkage characteristics according to the invention the tow is passed continuously through a heated zone. Before entering the heated zone the tow is suitably tensioned, and means are provided to enable the tension in the tow to be controlled within the heating zone and until it is cooled. For example, a set of feed rollers may be disposed prior to the heated zone and a set of takeup rollers after the cooling zone, the speed of one or both sets of rollers being variable. In one such embodiment the rollers are cylindrical and continuous cyclical changes in the speed of rotation of the takeup rollers relative to the feed rollers are employed to achieve a continuously varying shrinkage of the tow along its length. In another such embodiment conical rollers are used, and the position of the tow on the periphery thereof is. used to vary the shrinkage which takes place in the heated zone. When using conical rollers and by causing the tow filaments to be dispersed over the roller peripheries, varying shrinkage characteristics may be introduced transversely of the tow instead of, or in addition to, longitudinal such variations. Clearly the nature and extent of the variations can be controlled as desired within wide limits, and they will be chosen so that'when the resultant continuous tow is cut into staple, fibres will exist which have the desired different shrinkage characteristics. The conversion of the tow into yarn may take place in any suitable way, such as, for example on a Pacific or Rieter tow-to-top converter, or by cutting into staple and carding in either case, followed by conventional drawing and spinning operations. It is important that the conversion should be carried out in away which ensures thorough mixing of the staple fibres and which does not destroy the differential shrinkage characteristics which have been given to the fibres. Finally the yarn is heat-treated at a suitably elevated temperature to cause the fibres to shrink differentially, whereupon the yarn structure is modified, owing to the interaction of the fibres as the differential shrinkage takes place.
There appears in FIG. vl a diagrammatic illustration of one embodiment of apparatus for carrying out the method of this invention which apparatus is particularly adapted for processing commercially available polyacrylic tow. According to this embodiment, the tow is passed from any convenient source through two pairs of spaced-apart feed rollers 11 and 12, respectively, arranged on either side of a steam chamber adapted for the passage of the tow therethrough. The roller pairs are driven by means of the respective motors l3, 14 which are adapted to have the speed thereof altered over a considerable range by an appropriate control. A fan 15 is provided between the outlet of the steam chamber and the second roller pair 12 to direct a cold blast of air against the tow. The purpose of the air blast from fan 15 is to impart to the tow emerging from the steam chamber more rapid cooling than would exist in the ambient atmosphere alone so that the tow has achieved a more stable condition before encountering roller pair 12. After leaving roller pair 12, the tow is advanced to machinery capable of converting the same into staple fibres and ultimately into spun yarn. Such machinery is of types conventionally employed in the art and may include, as appears in FIG. 1, a staple cutting machine, a card, one or more draw frames, a roving frame, and finally, a spinning frame. The staple cutting machine is preferably of the type that can be adjusted to produce staple the length of which varies within narrow limits or is a chosen constant length.
The distance separating the roller pairs and hence the length of the heating zone as defined by the steam chamber and the cooling zone should preferably be relatively small compared with the length of the tow over which a complete cycle of variations occurs. It is advantageous from the standpoint of flexibility of operation for the steam chamber to be designed for operation under pressure or not, as desired, as well as for varying the temperature of the steam supplied thereto. The following examples illustrate the operation of the apparatus of FIG. 1.
EXAMPLE 1 This example describes the processing of a 500,000 denier, 5 denier per filament, commercially available polyacrylic tow made from a co-polymer which is 94 percent acrylonitrile and 6 percent vinyl acetate (Acrilan) on the apparatus of FIG. 1 to produce a woollike yarn according to the invention. The tow has initially a substantially uniform shrinkage characteristic of 20 percent, in saturated steam at 212F.
The relaxing ratio of the roller pairs is caused to vary continuously by adjustment of one or both of roller driving motors from 1 to 0.82 whilst processing eighteen feet of tow, then from 0.82 to 1 Whilst processing a further eighteen feet of tow and so on. The distance between the roller pairs is much less than 18 feet, say about 3 feet. The temperature of the steam chamber is approximately 212F and the pressure atmospheric. The length of the steam chamber is approximately one foot and the linear speed of the tow is 30 feet per minute. After emerging from the steam chamber and before passing between the rollers of pair 12 the tow is caused to pass below the fan which blows a current of cold air over it to promote more rapid cooling to a temperature at which it is stable. From the roller pair 12 the tow is passed to the cutting machine by which it is converted to staple varying in length from 5 to 7 inches. The staple thus produced varies in its shrinkage characteristics in saturated steam at 212F over the whole range of 0 percent to approximately 18 percent, and the distribution of the fibres with different shrinkage characteristics is uniform over the range. Likewise the distribution of fibres of different staple length is uniform over the range of staple lengths. Within each staple fibre there will be a continuous variation of shrinkage characteristic from end to end, but this variation will be very small amounting to no more than a difference of about /2 percent. The staple is then passed through a line of conventional long staple flax type spinning machinery comprising card, draw frame, roving frame and spinning frame. The final yarn produced is 24s worsted count, eight turns per inch.
The yarn is made into hanks and heat-treated in saturated steam at 2l2F for a period of minutes to develop its shrinkage Characteristics which results in a yarn which resembles in its essential physical characteristics a woollen yarn. In handle and appearance it corresponds closely to a woollen yarn. Its processing characteristics and in particular its load-elongation and recovery characteristics also correspond closely to those of a woollen yarn. The yarn is therefore satisfactory for weaving and knitting into excellent fabrics, combining many of the more desirable qualities of both wool and polyacrylics, and which have, in particular, very good dimensional stability and crease resistance.
EXAMPLE 2 In this case two ends of the singles yarn described in I Example 1 are plied before or after the final heattreatment described in the previous example. In either case the result is a yarn which is satisfactory for weaving and knitting into excellent fabric, for example machine knitted outerwear of the fashion type for which wool and conventional high bulk yarns are presently used, and having the same qualities as the fabrics of example 1.
Some differences of appearance of the yarns may arise (reflected to a lesser extent in the appearance of fabrics made therefrom), depending on whether development of its varying shrinkage characteristics is carried out before or after plying.
It will be clear that in a process involving treating the tow as in the foregoing examples the substantially uniform shrinkage properties of the tow as originally produced are modified in a variable manner so that by a subsequent treatment uniformly applied the staple fibre produced from the two may be caused to shrink differentially. It is therefore important that the processing conditions employed should not be such as would destroy the ability of the filaments to shrink. Thus when processing a high shrinkage polyacrylic filament tow the use of temperatures which are too high or processing times which are too long or both might render the differential shrinkage referred to impossible and must therefore be avoided.
If heating of a polyacrylic filament tow is in the presence of moisture, the temperature should ordinarily be above 185F, whilst if carried out in dry air the temperature ordinarily should be above 260F. Preferably saturated steam at approximately 212F is used. The time of passage through the zone should not be too short. When using such steam treatment the time of passage through the treatment zone should not be more than six seconds and it is preferred to reduce this time to one second if possible.
A wide variety of results may be obtained when processing filaments on apparatus such as that illustrated in FIG. 1 by adjusting certain variables, the most important of which are the actual range of shrinkage characteristics induced in the filaments; the manner in which the shrinkage characteristics vary within that range; the length of the filaments over which the shrinkage characteristics vary; and the relationship of the staple length of lengths of fibres cut from the filaments to the foregoing. Further examples will now be given.
EXAMPLE 3 A tow similar to that of example 1 is processed on the apparatus of FIG. 1 in such manner that the distribution of the variable shrinkage characteristic throughout the mass of subsequently cut staple fibre is uniform. The staple length is arranged to be constant at six inches, and there is negligible variation of the shrinkage characteristic within the individual fibres.
The staple fibre cut from the tow is processed on long staple flax machinery which gives thorough mixing and a yarn of 16s lea five turns per inch is produced. From the yarn is produced a 4-ply three turns per inch yarn which is fully developed by heating to cause shrinkage in the same way as the yarn in example 1.
The final yarn has an extension to break of 25 percent and a fibre packing factor of 0.27. The instrument used for establishing the extension to break is the Uster single thread strength-testing machine and the instrument used for establishing the fibre packing factor is the Bocking Geometer (described in the Journal of the Textile Institute Vol. 50 No. 12 of December 1959 pages T.655 et seq. which is published in Great Britain for the Textile Institute, 10 Black-friars Street, Manchester 3, England, by McCorquodale & Co. Ltd., Newton-le-Willows, Lancashire, England).
The yarn is very similar in appearance, handle and workability to certain woollen yarns suitable for the hand knitting of outerwear. It is to be particularly noted that the load-extension and recovery characteristics of the yarn are very similar to those of woollen yarn of corresponding bulk and therefore the yarn is very suitable for hand or machine knitting, unlike conventional high bulk yarn usually made from mixtures of two dis tinct types of staple, one with a given non-varying shrinkage characteristic and one with a different nonvarying shrinkage characteristic. Such high bulk yarn has considerably less give" than woollen yarn and for this reason is not as easy to knit.
Fabrics knitted from the yarn of example 3 have all the desirable properties associated with yarns made from fibres, such as polyacrylic fibres, which have low water imbibit-ion anda high natural ability to recover from deformation, and which therefore have what are usually referred to as easy-care qualities, e.g. ease of laundering and drying without the necessity of ironing. In addition the fabric is more resilient than similar garments produced for examplefrom high bulk yarn and show great dimensional stability in washing. Furthermore the yarn when made up into fabric gives a welldefined clarity of stitch in the knitted fabric compared, for example, with similar fabric made from conventional high bulk yarn made from similar fibres. Furthermore the fabric made from the yarn is more resistant to pilling and scuffing than fabric made from conventional high bulk yarn.
EXAMPLE 4 Again a tow similar to that used in example 1 is processed on the apparatus shown in FIG. 1. The variables are adjusted so that the distribution of the variable shrinkage characteristic is not uniform. There is a substantially uniform distribution of fibres having from -5 percent shrinkage but these form 20 percent of the total. There is likewise a substantially uniform distribution among the remaining fibres having shrinkage characteristics from -20 percent. It is also arranged that the fibre length varies from 5 to 7 inches and the distribution of the fibres of different staple lengths is uniform throughout the mass. Within each individual fibre there is negligible variation of shrinkage characteristic.
24s worsted eight turns per inch yarn is produced from the staple cut from the tow in the same manner as in example 3 which is then made 2-ply five turns per inch and fully developed in the manner described in example 1.
The final yarn has an extension to break of 25 percent and a fibre packing factor of 0.24.
The yarn is much softer in handle than wool and in this respect resembles conventional high bulk yarn of similar fibre packing factor. Its load-extension and recovery characteristics, however, are similar to those of a woollen yarn of corresponding bulk. Its other qualities are similar to those described in example 3 although there is a less well-defined clarity of stitch.
EXAMPLE 5 In this example a 500,000 denier, 5 denier per filament, commercially available polyacrylic tow made from a co-polymer which is 94 percent acrylonitrile and 6 percent vinyl acetate is processed to give a woollike yarn. The tow has initially a substantially uniform zero shrinkage characteristic in saturated steam at 212F.
The apparatus of FIG. 1 is used but in this case the variables are adjusted so that the tow is stretched differentially according to a programme as follows. The effective stretching ratio of the rollers is caused to vary continuously from 1 to 1.12 when processing the first eight feet of the tow; from from 1.12 to 1.3 when processing the next four feet of the tow; and from 1.3 to 1.4 when processing the next 8 feet. This is a half cycle of the programme and the effective stretching ratio of the rollers in the next half cycle follows the reverse pattern. Thus the effective stretching ratio of the rollers varies from 1.4 to 1.3 when processing the next 8 feet of tow, from 1.3 to 1.12 when processing the'following 4 feet, and from 1.12 to 1 when processing the next 8 feet. The full cycle is continuously repeated to give a tow 40 percent of which has substantially uniform distribution of variable shrinkage characteristics within the range of 0 percent 10 percent, percent between 10 percent 20 percent and 40 percent between 20 percent percent The tow is then cut to a staple length of six inches and processed on suitable long staple machinery to produce yarn of 24s worsted count with eight turns per inch Z twist. The yarn is two plied with 5 turns S twist and then fully developed as in example 1. The resultant yarn is bulky with an open structure but more similar to a high bulk yarn than the yarn of the previous examples. It exhibits the same advantages claimed in example 3 but to a lesser degree. i
If the effective stretching ratio on the third and fourth parts of the cycle are modified to vary from 1.3 to 1.5 then a range of 20 percent percent instead of 20 percent 25 percent is given and slightly different but still useful yarn is produced.
EXAMPLE 6 In this example a carpet yarn is produced from a 15 denier per filament high shrinkage polyacrylic tow.
The tow is processed on the apparatus shown in FIG. 1 with the variables adjusted to give uniform distribution of variable shrinkage characteristic within the range 0-10 percent; a uniform staplelength of six inches; and substantially no variation of the shrinkage characteristic within individual fibres.
The staple fibre cut from the tow is crimped in a stuffing box and then spun on the standard long staple machine carpet system to SS cotton count three turns per inch and then folded 3-ply 1.1/2 turns per inch.
Shrinkage development is as described in example I.
The resultant yarn is of higher bulk than conventional carpet yarn made from synthetic fibres, but has a lower initial modulus which makes it easier t0 process on the tufting machine. When tufted into carpet it exhibits high tread resilience and good covering power.
The foregoing examples it will be noted refer to the production of polyacrylic yarns for the reason that polyacrylic tow is currently readily available in high shrinkage form and can very conveniently have its shrinkage characteristic modified in accordance with the present invention by the method of differential relaxation employed in the foregoing examples. This particular mode of practising the invention is, however, as will readily be appreciated, applicable to any filament which has a high shrinkage characteristic and which can have this characteristic modified differentially so as to be capable of development by a subsequent treatment. Examples of other filaments are polyamides, such as nylon, polyesters such as polyethylene terephthalate, and polyolefins such as polypropylene.
The diagrammatic illustration of FIG. 2 is of a modified embodiment of apparatus especially adapted for the processing of such other filaments. This modified embodiment is very similar to the embodiment illustrated in FIG. 1 except in two respects. First, the roller pairs 16, 17 respectively, are driven at the same constant speed either by means of constant speed motors (not shown) or by appropriate control of motors similar to motors l3, 14 of FIG. 1. Second, the steam chamber is replaced by a heating member 18 through which hot air is circulated so as to heat a tow passing in proximity thereto to a temperature which can be varied cyclically over a considerable range.
The following example illustrates the practice of the invention on the apparatus of FIG. 2
EXAMPLE 7 In this example a polyethylene terephthalate tow of 200,000 denier, 3 denier per filament, is processed in the apparatus of FIG. 2. The material is supplied by the producer so processed during and after hot drawing step that it has a uniform shrinkage characteristic of 18 percent when subjected to a temperature of 356F in the absence of moisture.
The heater 18 is so controlled as to heat the tow passing therethrough to a continuously varying temperature between the limits of 158F and 356F. The temperature is caused to vary in a linear manner from maximum to minimum over eighteen feet of passing tow and back again over a like length of passing tow. The tow so processed in an analogous manner to the tow of example 1 is converted to 6 inch staple, and spun into yarn, which is then heat-treated at 3567F in the absence of moisture to produce a yarn with a structure modified in a similar manner as in example In this example it will be noted that a somewhat different method is employed to modify the shrinkage characteristic differentially. The principal reason for this is that polyethylene terephthalate has different processing characteristics to those of, say, polyacrylonitrile. Difficulties exist in processing polyethylene terephthalate on the apparatus of FIG. 1 since in order to prevent the filaments becoming set or partially set the processing speeds necessary would give rise to practical problems. Of course setting or partial setting would preclude or considerably diminish the subsequent shrinkage development which is necessary for the satisfactory practising of the present invention. The principles involved are in general the same, however, and the processing variables may be adjusted in an analogous manner to the variables involved in the previous examples, and likewise different end results may be obtained.
Where a viscose rayon tow is to be processed according to the invention, a further modification of the apparatus is preferably employed for this purpose, as is illustrated diagrammatically in FIG. 3. As can be seen in this figure, the tow is passed first through an aqueous bath 19 containing a polymerizable resin-impregnating composition such as a water-soluble ethylene urea formaldehyde precondensate and a suitable resinifying catalyst, such as magnesium or ammonium chloride, and then through a pair of driven nip rollers 20. The upper roller of the pair 20 is supported for vertical movement and loaded resiliently by means of a spring 21, lever 22 and rotating arm 23. This system is so designed that it operates to effect a variable expression of the bath liquid. For example it can be arranged to leave the ethylene urea formaldehyde resin on the tow in amount from 2 percent to 10 percent of the weight of the tow, the amount varying continuously from the maximum to the minimum and back again over successive 18 feet lengths of the tow. In practice to obtain such a range of expression a multiple bath system using baths of different concentrations might well be necessary but in the embodiment as illustrated, for simplicity, only one bath is shown.
The tow is then passed through a baking oven 24 maintained at a sufficiently high substantially constant temperature, say within the limits 302F to320F, to cure the ethylene urea formaldehyde condensate to an insoluble resin.
Next the resin treated tow passes through a bath 25 of warm water and then through a bath 26 containing a solution of an appropriate fibre finish (to aid spinning) dispersed in cold water (e.g. a 0.1 percent solution of CIRRASOL HA, obtainable from Imperial Chemical Industries Limited). From this bath the tow passes through a hot air drier 27. After being dried the tow is processed on spinning machinery similar to that already described with reference to FIG. 1, and finally the yarn thus produced immersed in aqueous caustic soda solution or like shrinking agent. Thus, by using a caustic soda solution of 30 Twaddell plus 10 percent common salt the shrinkage varies from a maximum of about 20 percent where the resin deposited is 2 percent to a minimum of 5 percent where the resin deposited is 10 percent, so as to give rise to a similarly modified structure to the yarn described in example 1. At some convenient later stage it may be necessary to process the yarn or fabric made therefrom so that all the fibres are cross linked or stabilized to substantially the same degree, for example by the application of a creaseresist resin. Otherwise, there may be a tendency during later processing and use, particularly washing, for the special characteristics of the yarn to be lost.
It is to be noted that although the process of this example depends on variable expression of the resin treating bath liquid, the latter may be alternatively, or additionally (as stated), caused to vary in resin concentration as the tow passes therethrough.
The foregoing examples all refer to the modification of the shrinkage characteristic of textile filaments and are examples of a very important aspect of the present invention. These particular processes are applicable to all filaments which can be put into a condition where they can be shrunk differentially. In general all wholly synthetic thermoplastic filaments can be so treated along with many other manmade filaments. Specific methods and apparatus have been described in the foregoing examples, but the particular method and apparatus chosen will depend on the particular characteristics of the material from which the filaments are made. Thus as has been shown in the foregoing examples it is preferred to process polyacrylic filaments in one particular manner, polyethylene terephthalate filamentsin another manner, and viscose filaments in still another manner. Polyamide filaments can be processed according to the present invention in a similar manner to polyethylene terephthalate filaments. Generally speaking polyamide filaments are currently available, however, with a total shrinkage characteristic of about 10 percent which would limit the range of end results obtainable. However, polyamide filaments with a higher total shrinkage characteristic can be produced thus enabling the range of end results to be extended. Furthermore polyamide filaments can be given variable shrinkage characteristics by chemical processing in which a chemical, causing fibre shrinkage, is applied differentially to the filaments, subsequent development being by uniform application of the chemical to the filaments. An example of such a chemical is phenol in aqueous solution ofa concentration less than 4.1/2 percent. Furthermore although the foregoing examples relate to high shrinkage tows similar principles are applicable to fully relaxed tows in which case differential shrinkage could be induced by differential stretching, and without it being necessary to use heat, although heating can be employed if desired.
The foregoing examples are also all directed to the production of yarns from staple fibre in accordance with the present invention and further examples will now be given also relating to production of yarn from staple fibre, but illustrating that it is not necessary for i all the staple fibre which is used to have been produced according to the present invention, or if so produced to be of the same type.
EXAMPLE 8 In this example 5 denier per filament high shrinkage polyacrylic tow is processed on the apparatus of FIG. 1. The distribution of the variable fibre shrinkage characteristic is uniform and the range from 0-10 percent. The staple length is uniform at 6 inches and there is substantially no variation of shrinkage characteristic within individual fibres. The staple fibre cut from the tow is carded and the slivers produced are blended O 50 with slivers of 56s quality wool combed top on the conventional worsted system and spun to s worsted count yarn. The yarn exhibits fairly even distribution of the different fibres with perhaps a tendency for the wool to predominate at the outside.
The final yarn has an extension to break of 22 percent and a handle similar to that of yarn made from wool. The yarn is not subject to shrinkage or other conditions to develop its varying shrinkage characteristics but woven into fabric having ends per inch and 35 picks per inch. This fabric is developed by immersing in water at approximately 2 l 2F in a tensionless condition. Care is exercised not to allow the fabric to crease before it is cooled. The fabric thus developed has approximately 39 ends per inch and approximately 39 picks per inch. It has a warp and weft crease recovery value of 150 by the British Standard Method of Tests for the Recovery of Fabrics from Creasing, BS 3086; 1959, published by British Standards Institute, British Standards House, 2 Park Street, London W.l, and
printed by Baynard Press, London S.W.9. The fabric is very similar to a corresponding woollen fabric, has easy-care qualities and is suitable for skirts and suitings. It is particularly stable dimensionally.
EXAMPLE 9 g the apparatus from the 6 denier per filament tow had a uniform distribution of fibre shrinkage characteristic within the range of 10-18 percent and a uniform staple length of 6 inches. In both cases there was a negligible variation ofthe shrinkage characteristic within the individual fibres. The two component staple fibres were blended together in the proportions 60 percent (0-10 percent shrinkage fibre) percent (l0l8 percent shrinkage fibre) and the resultant blend spun on the flax system to s lea ten turns per inch singles. This was then used to produce 2-ply six turns per inch yarn.
The final yarn was developed in the same manner as in example 1 and woven into a plain ,fabric with 25 picksper inch and 25 ends per inch.
The yarn after development had an extension to break of 26 percent and a handle similar to that of yarn made from wool. The yarn was of open structure throughout, the inner portion consisting predominantly of the 6 denier fibres and the remainder consisting predominantly of 3 denier fibres. The fabric had a crease recovery value of 156 (weft) and 154 (warp) by the Monsanto or Shirley test. A soft handle was also evident.
There are several known methods of producing continuous multifilament bulked yarns, for example, those methods based on false-twisting the filaments, passing the filaments over a heated sharp edge, subjecting the filaments to an air blast, and passing the filaments through a stuffer-box. All such methods, however, involve additional processing of the yarn as supplied by the producer that is to say, by throwing operations.
In the embodiments of apparatus thus far described, all of the strands in the given tow assembly are processed in like manner, the variations created therein varying uniformly across the entire assembly. It is within the scope of the present invention, however, to produce variations which differ or are non-uniform in corresponding regions of the filaments making up the assembly. One embodiment of apparatus for producing this effect is illustrated diagrammatically in FIG. 4 of the accompanying drawings. Such apparatus is disposed so that a plurality of continuous filaments as pro duced in the known manner from a spinneret and its associated drawing system can be passed continuously in the absence of twist therethrough. Of course the method could be applied as an additional process at some later time if desired.
In the apparatus of FIG. 4 a continuous sheet 30 of synthetic filaments having a relatively low uniform shrinkage characteristic say, of less than 10 percent for polyacrylic filaments, and thus capable of being further drawn to a substantial degree are passed side-by-side through a drawing system which includes two spaced pairs 28, 29 of conical rollers. Both the rollers of the first pair 28 have their smaller ends in juxtaposition at one edge of the sheet of filaments 30, whilst both the rollers of the second pair 29 have their smaller ends at the other edge of the sheet of filaments 30. Both pairs of rollers 28, 29 are driven at like peripheral speeds and are linked by a mechanism 31 which repeatedly causes the rollers of each pair 28, 29 to separate in turn. Thus, the filaments will be successively and repeatedly under the drawing influence of first one pair of rollers 28 and then the other pair 29. When under the influence of the one pair 28, the filament at the smaller ends of the rollers will be stretched a minimum amount whilst the filament at the larger ends of the rollers will be stretched a maximum amount. The filaments inbetween will be stretched to varying degrees between the two extremes. When under the influence of the other pair the effect will be reversed, since the filament previously subjected to minimum stretch will now be subjected to maximum stretch and vice versa. The roller pairs are similarly dimensioned and the sheet of filaments extends over like parts thereof, and so the filaments at or near the centre of the sheet will always be stretched by substantially the same amount. It will usually be necessary to provide a compensating system 32 associated with the roller pairs 28, 29 because the filaments will, from time to time, have different linear speeds. The system 32 will include a movable roller, under which the filaments pass, which is adjusted in position continuously to deflect the filaments in such a manner that a substantially constant tension is preserved in each.
After passing through the drawing system all, or nearly all, the filaments will have been stretched by varying amounts along their length, depending on the speed of the conical rollers and the frequency of the change over from one pair to the other, the effect being variable also across the sheet of filaments.
The filaments are subsequently twisted to form a yarn and then shrunk by uniform heat-treatment. Since the amount of shrinkage at any given part of a filament at a given temperature depends on the amount that part of the filament has previously been stretched, the shrinkage will differ along the length of each filament and also transversely of the yarn, the result beingthat, in any short length of the yarn the filaments which shrink least are caused by the other filaments to loop and spread, which gives the yarn as a whole increased bulk without high stretch at low loads. The effect may, if desired, be further varied by changing the twist in the yarn.
The general technique utilized in connection with the apparatus of FIG. 4 can be readily adapted to the needs of filaments which by their nature exhibit a better response to a heat treatment than to a stretching operation, such as those formed of polyethylene terephthalate polymer, by substituting for the variable stretching means of FIG. 4, a means for applying to the filaments a variable heat treatment. Thus, as shown in FIG. 5, the filaments in this case are processed in a manner analogous to that used in the embodiment of FIG. 4 except that instead of conical rollers, two hot air heaters 33, 34 are used through which the filaments are passed at a constant speed by feed and withdrawal roller systems (not shown). Their heating effect is arranged to vary across the sheet of filaments. The first heater 33 when in operation causes the filaments at one edge of the sheet to be heated to a relatively high temperature at which the filaments exhibit maximum shrinkage and the filaments at the other end of the sheet to relatively low temperature at which no shrinkage occurs with a selected temperature gradient therebetween. The other heater is arranged to have a reverse effect. As in the case of the rollers of the previous example the heaters are brought alternately into operation. The result of this is that the filaments are given markedly differential shrinkage characteristics in like manner to that appearing in filaments processed in the apparatus of FIG. 4. The following example illustrates the operation of the embodiment of FIG. 5.
EXAMPLE Filaments of polyethylene terephthalate which are produced with a uniform shrinkage characteristic of percent at 356F in the absence of moisture are processed in the absence of twist in the apparatus of FIG. 5, the heating action of the first heater 33 being such as to heat the filaments at one edge of the sheet to a temperature of 356F and the filaments at the other end of the sheet to a temperature of 122F, with the filaments between the two edges varying uniformly between these extremes. The temperature gradient of the second heater 34 is made to be precisely opposite from that of the first heater 33. The heater temperature and yarn rateof travel therethrough are regulated in such amanner that a variable shrinkage characteristic of from 0 percent to 18 percent is induced. When twisted and subjected to a suitable further constant temperature heat treatment the yarn bulks as the differential shrinkage takes place. i
In another procedure for producing a bulked continuous filament yarn a continuous sheet of polyacrylic filaments having a shrinkage characteristic of less than 2 percent are passed over a hot godet heated to 280F and then to a cold godet held at 50F. The godets are linked by a variable speed drive, the hot godet being driven at a suitably constant speed while the cold godet is varied in speed in a cyclic manner over the range 1.01-1.25 times the speed of the hot godet. The sheet of filaments delivered by the cold godet is passed over a spreader roller and a series of fixed guides which are so positioned to ensure that the passed length traversed by the various filaments across the width of the sheet from the spreader roller to a delivery roller varies between P and P +a/2 where P is the shortest distance between the spreader roller and the delivery roller and a is the filament length passing during one cycle of speed variation of the cold godet.
By reason of the variable drawing introduced between the two godets the sheet of filaments emerging from the spreader roller has in it a cyclic variation in shrinkage characteristics of the order of 0-20 percent. This variation exists in each filament and is in phase from filament to filament. The guides cause the filaments to be displaced longitudinally at the delivery roller so that the variation becomes out of phase to the maximum extent possible between the filaments, the phase change varying from 0 to 01/2 across the sheet. Thus the filament assembly has been constructed such that in any cross section thereof each filament will have a different shrinkage characteristic varying from 0 percent 20 percent approximately. When the assembly thereafter has twist inserted into it and is exposed to steam at 212F the parts of the filaments with the higher shrinkage characteristics will tend to buckle those with the lower shrinkage characteristics and so form an open structured bulked filament yarn which will have desirable tensile characteristics or properties in that its extension under low loads will be similar to that of bulked spun yarns of the type previously described. Such yarns will result in more stable fabrics demanding less critical processing conditions in winding, weaving and knitting operations.
If desired, the treatment effective to impart to the filaments the variable shrinkage characteristics can be carried out in conjunction with the staple cutting step of the over-all process instead of in a separate prelimi nary step as has been the case in the embodiments thus far described. One form of apparatus in which the variable shrinkage treatment and the staple cutting steps are carried out concurrently is illustrated in FIG. 6. As shown in this Figure the tow is fed by means of a pair of nip rollers 35, 36 rotating at constant speed to another pair of rollers of special design whereby the tow is reduced to staple. The lower roller 37 of the second pair is of rubber and is cylindrical and concentrically mounted. The upper driven roller 38 which is surfaced with rubber carries cutters 39 at spaced intervals around its periphery and is eccentrically mounted, its bearings being arranged to reciprocate along the line of centres of the two rollers. Means 40 for directing a steam jet on the tow as it enters the nip between the rollers of the second pair is provided. It is important that the filaments are cooled before they emerge from the nip of the second pair of rollers and the point of application of the steam jet is chosen accordingly and special cooling means, such as means 41 for projecting a jet of cooling air on roller 38, provided if necessary. The speed of rotation of the second pair of rollers, the spacing and position of the cutters and the eccentricity of the top roller areso chosen that staple of appropriate length is cut from the tow, each fibre, due to the continuously varying peripheral speed of the top roller, resulting from its eccentricity, having been relaxed in a continuous variable manner, say, from percent to 20 percent from end to end.
EXAMPLE l2 Yarn is spun from the staple prepared by processing a high shrinkage tow of polyacrylic filaments on the apparatus of FIG. 6 at the relaxation range of 6-20 per cent and when appropriately heat-treated exhibits a structure which varies from very open at the outside to quite compact at the core.
Clearly the nature of the variation in the fibres may be controlled in many different ways and different end results thereby obtained.
Concurrent reduction of the tow into staple and introduction of the variable shrinkage characteristic to the filaments thereof can also be accomplished with a different type of known staple cutting machine, according to which a cutting blade is passed transversely across a moving sheet of filaments. One such apparatus embodying the present concept is diagrammatically illustrated in FIG. 7. According to the apparatus of FIG. 7, a suitable high shrinkage tow, for example of polyacrylic filaments, is cut into staple by a cutter 42 of the Nordholm or Braidwater type carrying a steam nozzle 43 at a given distance behind the cutter blade. The details of the mounting and operation of the cutter 42 and associated steam nozzle 43 have not been shown since they are either well-known in the art or obvious to a person skilled in the art. In this way a part of each fibre is automatically steam relaxed so as almost completely to inihibit any further heat shrinkage thereof. In this case the variation of the shrinkage characteristic is substantially discontinuous, and when the staple is spun into yarn, and the yarn subsequently subjected to an appropriate heat-treatment the latter exhibits a more sharply defined transition from a compact core to an open-structured surface,
Discontinuous variations in the shrinkage characteristics of a group of continuous filaments may be obtained by similar means but without cutting.
When producing staple fibres according to the invention the effect of subsequent processing steps should be taken into consideration. For example, it is often desirable, if producing sliver using a card other than a flax card, to have crimp in the fibres. The step of imparting the crimp after the fibres have been subjected to variable modification, may, and often does, cause the temperature of the fibres to be elevated, and such elevated temperatures will in certain cases modify the variable characteristics produced by the processing according to the invention. This will be so, for example, where the characteristic is shrinkage on subsequent heat- 7 treatment if the temperature reached in crimping is sufficiently high. It is, however, fortunately, a simple matter to compensate for this by introducing a correspondingly greater variability in the first place, so that the desired end result is still achieved. The alternative would be to choose a crimping method where a rise in temperature does not occur, or is so small as not substantially to effect the variability of the characteristic.
It will be appreciated that several of the foregoing examples which specify that the development takes place for instance in the yarn before it is fabricated could be modified so that development takes place after fabrication. Clearly the selected time of development will depend on the particular type of desired end result. Thus if development takes place in the fabric the yarn modification will, to some extent, be restricted by the inter relation of the fabricated ends of yarn. Of course, if the yarn is to be dyed before fabrication, it almost inevitably follows that development will have to take place at the time of dyeing.
As has been stated the foregoing examples all relate to the treatment of textile filaments and involve the modification of the shrinkage characteristics thereof. It will be clear that the possibilities of variation on this theme are numerous and the same would apply where the property was some property other than the shrinkage characteristic. In order to illustrate these possibilities it will be convenient to analyse fully the application of the invention by way of example to textile filaments and utilising the ability of certain such filaments to have their shrinkage characteristic modified in a variable manner. Thus, according to the present invention, the following may be produced:
I. A group of continuous filaments each filament having a like varying longitudinal shrinkage characteristic. This is achieved for example by providing pairs of cylindrical rollers before and after a heated Zone, between which tow passes, and continuously varying their relative speed, as in example 1, before cutting takes place.
FIG. 8 illustrates such a group of continuous filaments and the variation of the shrinkage characteristic is shown in this Figure by the thickness of the line representing each individual filament. It is to be stressed that this is merely a convention and is not intended to indicate the specific variation in the cross-sectional dimension of the filament.
It is also pointed out that in this Figure and in FIGS. 9 to 12 such filaments have been shown for the purposes of illustration and not limitation. In practice there would of course usually be a far greater number than this.
When the material of this group is in the form of a tow it will normally be used for producing staple fibre and in this connection reference should be made to group IV hereunder.
When the material of group I is in the form of a continuous filament yarn it can be utilized in accordance with the present invention in a number of different ways. For example it could be combined with a natural yarn and then a subsequent development treatment employed to produce, say, a fancy yarn.
It may be used in a fabric either alone or with other yarns. Thus for example if woven alone in a suitable pattern into a fabric and then developed a seersucker effect would be obtained. Yet another way of utilising such a yarn would be to cause the filaments to be displaced longitudinally relative to one another say by twist or air blast or by causing them to traverse a varying path length, before development whereafter a bulking effect is achieved.
II. A group of continuous filaments each (or many) having a different but unvarying longitudinal shrinkage characteristic. This may be, for instance, achieved by producing a pair of cylindrical nip rollers before a heated zone, and a pair of conical nip rollers after the heated zone, the speeds of the two pairs being fixed and passing tow through the system.
FIG. 9 illustrates filaments of this group the differential shrinkage characteristic being illustrated by use of the same convention adopted in FIG. 8.
In the form of tows filaments of this group may be reduced according to the present invention to staple fibre (see group IV hereunder).
In the form of continuous filament yarn interesting possibilities exist. It is difficult to envisage a commercial method of producing such yarn which will not involve an output in which the length of the individual filaments produced per unit time does not vary. One method of compensating for such a variable output would be to twist the yarn appropriately whereby to produce a yarn with successive compact nodes with a more open structure between the nodes. Although on developing such a yarn the bulk would be reduced, such yarns are useful in producing a woven fabric of very even structure. In this case the fabric would be woven from the. yarn before development and the development treatment applied to the finished fabric. In this way the initial bulk of the yarn would govern the spacing of the ends and picks and when the bulk was reduced or removed by the development treatment a fabric of very even structure would result.
III. A group of continuous filaments each (or many) having a different and varying longitudinal shrinkage characteristic. This is achieved, for example, by providing a pair of cylindrical rollers before the heated zone and a pair of conical rollers after the heated zone and varying their relative speed.
FIG. illustrates such a group of filaments using the same convention as before.
Continuous filament tows, like those of the previous groups, could be used to produce staple fibre from which yarns would be spun and in this connection reference should be made to group IV hereunder.
In the form of continuous filament yarn there are a widerange of possibilities and the continuous filament yarns of groups I and II might be considered as being special limiting cases in this range. It is to be noted that there is again the problem, as with continuous filament yarns of group I], of the variable output. In order to avoid the problem of variable output the filaments may be processed, for example, in the manner illustrated in FIG. 4, and FIG. 11 illustrates the manner in which the shrinkage characteristic varies in the group of filaments to treated. The discontinuities longitudinally of each filament will be noted but there is of course a continuous variation of shrinkage characteristic transversely of the yarn. Furthermore, the discontinuities would be displaced by twist and no unevenness along the length ofthe yarn would occur on development. FIG. 12 illustrates a group of filaments produced as illustrated in FIG. 5. In this case the longitudinal discontinuities are not so pronounced.
IV. A group of staple fibres including a number of types having different shrinkage characteristics. This may be achieved by converting any one or more of the groups of continuous filaments of I, II and III above into staple. The number of different types depends on the group or groups used and the number of filaments in it. The variation of shrinkage characteristics along the length of each fibre may be arranged to be substantially none up to a high variation according to the relationship between staple length and the processing conditions chosen.
Many of the specific examples given heretofore illustrate such groups of staple fibres and their usefulness.
V. A group of staple fibres each fibre having like variable longitudinal shrinkage characteristics. This may be achieved by producing a group of continuous filaments of group I, and suitably synchronising the cutting of the staple with the variable processing conditions, by using an eccentric cutter as in the embodiment of FIG. 6 (the variation being continuous) or by using a Nordholm or Braidwater cutter in the manner described in the embodiment of FIG. 7 (the variation being substantially discontinuous).
As has been indicated yarn produced from group IV staple fibres are of considerable interest and importance and when describing yarns produced from such staple fibres in the foregoing examples reference has been made for comparison purposes to conventional high bulk yarn produced from synthetic staple fibre. In order to aid a fuller understanding of the invention the structure of various yarns both conventional and according to the present invention will now be described.
FIG. 13 is intended to illustrate a cross section taken through a conventional unbulked yarn made from synthetic staple fibre all of a given shrinkage characteristic.
FIG. 14 illustrates to substantially the same scale a cross section through a conventional high bulk yarn made from synthetic staple fibre of two different shrinkage characteristics. The dark circles represent fibres with the higher shrinkage characteristic and the light circles the fibres with the lower shrinkage characteristic. The preponderance of fibres with the higher shrinkage characteristic at the core of the yarn is due to the tendency of these fibres to loop in and out of the core over relatively long distances, that is to say a substantial length of each fibre tends to remain in the core. The fibres having the lower shrinkage characteristic, on the other hand, tend toloop in and out of the core rapidly so that a relatively short portion thereof remains in the core.
FIG. 16 is a diagrammatic elevation to a large scale of a yarn of this type, but for clarity the number of fibres at any cross-section is ten compared with forty in FIG. 14. Furthermore, no fibre ends are shown in the short element illustrated.
FIG. 15 is a cross section through a yarn spun from synthetic staple fibres produced according to the invention the fibres having substantially a continuum of different shrinkage characteristics. In this case the different shrinkage characteristics are illustrated by different letters of the alphabet. The yarn of example 1 would be a yarn of this type, and it is assumed that there is negligible variation of shrinkage characteristic longitudinally of each fibre.
FIG. 17 is a diagrammatic elevation to a large scale ofa yarn of this type, but, again, for clarity the number of fibres at any cross section is only ten, and no fibre ends are shown.
A yarn which may loosely be described as somewhere between a conventional high bulk yarn and the yarn illustrated in FIG. 15 may be produced by utilising staple fibre falling within group V and having a continuous variation along each fibre. The tendency of such a yarn will be to have a greater compactness at the core than that illustrated in FIG. 15. This tendency may be exaggerated by utilising staple fibre of group V with discontinuous rather than continuous variation in the shrinkage characteristic and whilst in appearance, handle and tensile properties such a yarn would be very similar to a conventional high bulk yarn, it differs from such yarn in that instead of looping in and out of the core there is a tendency for all the fibres to become anchored at one end in the core and usually with the other end at or near the surface of the yarn. Such a yarn is particularly useful for the manufacture of blankets and other types of brushed fabrics since the brushing is facilitated and there is less shedding of fibres.
Although the majority of the foregoing examples have been concerned with the production of what may be described as bulked yarns from wholly synthetic thermoplastic filamentous material, and involve the step of causing such material to have variable shrinkage characteristics, it is to be understood that the invention is by no means limited to such procedure. Thus, textile filaments may be treated in accordance with the invention so that they are given a differential affinity for a dyestuff. One method of achieving this would be to treat the filament surface with a suitable resin in a variable manner whereupon on subsequently having applied thereto a suitable uniform dyeing process a corresponding variable uptake of dye will occur, the resin being removed during or after dyeing if necessary or desirable. One of the main applications of such embodiments is to enable man-made filaments to dye in a similar manner to natural fibres. For example wool fibres have differential dyeing properties whereas manmade fibres tend to have much more uniform such properties. As a consequence tartans, for instance of man-made materials, never seem to have the appearance of woollen tartans, and this is thought to be a result of the aforesaid difference. Furthermore, differential crease-resistant properties could be given to fibres by the differential application of crease-resist finishes thereto in accordance with the invention. Also, the invention is not limited to the treatment of wholly synthetic thermoplastic yarn (as evidence by the foregoing example relating to viscose rayon) or even to other man-made fibres or filaments. Thus, a sliver of flax could have applied to it in irregular fashion a protective treatment which would result in the fibres having differential shrinkage characteristics capable of manifesting themselves after spinning under the influence of a suitable further treatment.
Furthermore, it is clear from the examples that a variety of simple means exist for endowing the particular material being treated with the desired variable latent characteristics, and for this reason the various mechanical and other means have been illustrated in diagrammatic form only. It is also clear that the group of filaments or fibres treated according to the invention may be quite small or very large. Thus, for example, a number of tows may be treated simultaneously in similar manner as in examples 1 to 4 and supplied to a can before further processing. Furthermore, if, as has already been stated, instead of a high shrinkage tow, as described for instance in example 1, a relaxed tow is treated, the same principles are involved except that in order to give it variable shrinkage characteristics variable stretching rather than variable relaxation takes place in the heated zone.
1. A tow of continuous filamentary textile material adapted to be'subdivided into staple fibers of generally predetermined length in which the continuous filaments thereof cyclically vary in gradual and continuous manner in latent shrinkage characteristic longitudinally thereof between predetermined minimum and maximum limits of significantly different values, the length of the cycle of said variation being substantially greater than said predetermined length of said staple fibers.
2. Staple cut from the tow of claim 1.
3. Spun yarn produced from the staple of claim 2.
4. The tow of claim 1 wherein said cyclical variation in latent shrinkage characteristic occurs uniformily in at least substantially all of the filaments in said tow.
5. The tow of claim 1 wherein the length of said cycle ranges from about inches to about 1,600 inches, and the difference between said maximum and minimum values is at least 5 percent.
6. Staple fiber produced from the tow of claim 5 wherein the mean staple length is selected to give a ratio relative to the cycle length within the range of 1/40 1/200.
7. The tow of claim 5 wherein the maximum latent shrinkage value differs from the minimum value by about 25-30 percent.
8. Staple fiber produced from the tow of claim 7 and having a distribution of fibers therein such that 40 percent have a latent shrinkage varying from the minimum value to the minimum value plus l0 percent, 20 percent have a latent shrinkage varying from the minimum value plus 10 percent to the minimum value plus 20 percent, and 40 percent have a latent shrinkage varying from the minimum value plus 20 percent to the maximum value.
9. The tow of claim 1 wherein said cycle length is at least twice the generally predetermined length of said staple fibers.
10. A tow of continuous man-made textile filaments in which the continuous filaments thereof vary in latent shrinkage characteristic gradually and continuously from filament to filament across the tow from a minimum value to a significantly different maximum value, the characteristic of each of substantially all of said filaments being at least slightly different from that of the other filaments, the latent shrinkage characteristic of each filament also varying longitudinally thereof between minimum value and a significantly different maximum value.
11. Staple cut from the tow of claim l0.
l2. Spun yarn produced from the staple of claim 11.
13. The tow of claim 10 wherein said longitudinal variation occurs cyclically along the length of the filaments, the length of said cycle ranging from about 60 inches to about 1,600 inches and difference between each of said minimum and maximum values is at least 5 percent.
14. Staple fiber produced from the tow of claim 13 wherein the mean staple length is selected to give a ratio relative to the cycle length within the range of H40 -l/200.