Yarnlike product with spaced polymer rings

[57] ABSTRACT

A generally twistless yarnlike product is kept coherent by means of circumjacent polymer rings applied at intervals, high bulk being achieved by a loop effect as the filaments or fibres are differently contracted between the rings. To make such a product and similar products bound with rings, a bunch of fibres or filaments is temporarily brought in twisted and revolving state, and strips of a polymer in fluid state are spun around by means of the revolution of the bunch.

Claims, 5 Drawing Figures

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PATENTED KC311974

SHEET 1 OF 2

3,857,230

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FIG. 2.

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PATENTED 0EC311974

3,857.230

SHEET 2 OF 2

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3,857,

YARNLIKE PRODUCT WITH SPACED POLYMER RINGS

This is a division, of Ser. No. 120,186, filed Mar. 2, 1971, now U.S. Pat. No. 3,762,142, issued Oct. 2, 5 1973.

Yarns or yarnlike products are known which are kept together through a binding material instead of through twisting. These products are, however, either relatively stiff and compact, or they show little coherency, and 10 their applications are therefore limited. The present invention aims at obtaining an adequate combination of volume, flexibility, resilience, and coherency.

It is known to extrude a bundle of filaments which are thereupon entwined with a thread of molten polymer 15 from a nozzle rotating around the bundle, whereby — without actual twisting — a yarn or yarnlike product is obtained with a structure simulating a twist.

The present invention relates to a yarn or yarnlike product consisting of filamentitious structures, kept in 20 bunched relationship by means of a circumjacent polymer material. The characteristical features of the yarn or yarnlike product according to the invention are that said circumjacent polymer material forms rings which keep the bunch in a compact round shape within short 25 zones, the intervening zones of the bunch being in a bulky state.

Due to the segmental arrangement where zones of strong binding alternating with zones without any direct binding all the above-mentioned properties can be ³⁰obtained at the same time. The rings should preferably, but not necessarily, be adhesively bonded to the circumferential portion of the bunch.

The lengths of the zones supplied with rings should for most purposes be in a range between about 0.2 mm ³⁵and 1 cm, while the lengths of the intervening zones should for most purposes be in a range between about 1 mm and 5 cm. Dependent on the use, the bunch can consist of filaments and/or staple fibres and/or fibrillated film and/or non-fibrillated, transversely compacted film and/or of ribbons and/or other fibrelike or filamentlike structures. The product can further be a single, transversely compacted film kept in the shape of a bunch by means of the rings.

An advantageous embodiment of the product according to the invention is characterized in that the filamentitious structures in each intervening zone have different lengths measured from ring to ring in the unloaded condition of the yarn. This is generally obtained by different shrinkage of the filamentitious structures after the application of the rings, as will be explained below. The relatively long fibres will be bent and will hereby tend to elongate the product, while the relatively short fibres will be straightened out and will tend to contract the length. There is hereby obtained a high and very stable volume.

An embodiment of the product according to the invention, of the type which comprises different lengths between the rings, is further characterized in that said lengths are shorter in the central portion of the bunch and longer in the outer portion of the bunch. Because of the order of this structure there is hereby obtained the most pronounced visual effect of the structure and generally also the highest volume.

An alternative embodiment, also of the type which comprises different lengths between the rings, is characterized in that the distribution of the shorter and the

230 longer filamentitious structures is at random. Although this arrangement generally produces a somewhat lower volume, the bulk is on the other hand generally more stable.

The random distribution can be obtained by blending staple fibres of different ability to shrink and making a raw-yarn herefrom in conventional manner. Another way to obtain random distribution is to lay two network-formed, fibrillated films from different substances one upon the other and compact the plied structure transversely.

It has been mentioned that the longer filamentitious structures and the shorter ones generally represent different amounts of shrinkage, and these differences can be obtained by a variety of selections.

Thus in one embodiment the shorter filamentitious structures consist of an elastomer, and the longer ones consist of a stiffer substance. This selection has the advantage that the elastic material easily elongates until the elongation is stopped by the straighteningout of the stiffer filamentitious structures which will then provide a relatively high tensile strength. Further the elastomer will readily contract to the shorter length and thus the bulk will recover efficiently when the tension has been released. For apparel purposes and in other cases when fine fibres are generally required, the elastomer should preferably be a thermoplastic elastomer of the type where the stabilisation is due to crystalline segments instead of real cross-linking, as for example extrudable polyurethane rubber.

In another embodiment the shorter filamentitious structures are crimped bicomponent fibres or filaments, and the longer filamentitious structures are mono-component fibres or filaments. Crimped bicomponent fibres generally act like elastomer fibres and have the advantage that they are much easier to blend with other fibres (generally in uncrimped state), and the choice of applicable substances is wider. On the other hand, the tension in stretched state at low elongations is generally lower.

When distinguishing between “shorter” and “longer” filamentitious structures in the cases when some of the fibres are curled-up bicomponent fibres, what matters is, of course, not the lengths along the helices, but the ⁴⁵ lengths measured along the axes of the helices.

In still another embodiment the filamentitious structures are bicomponent fibres of different crimp. In this manner the product has particularly high extensability, but on account — to some extent — of the volume.

⁵⁰ Cut up to short lengths the product of the invention can with advantage be used as an artificial feather or down, e.g. in pillows and quilts. In order to fit well to the shape of the body, the lengths should preferably be . as short as possible in proportion to the transverse ⁵ span, and for this and similar purposes an embodiment of the product is characterized in that it only comprises two rings.

Though the transverse coherency in the yarn or the &gt;₀ yarnlike product is substantially due to the rings, it ° should be understood that the product may also be provided with a slight twist.

The polymer to form the rings can be supplied either in molten or dissolved or emulsified state, or in form of ,,. one or several prepolymers. Correspondingly the solidi³ fication can take place either by cooling or by evaporation of a solvent or of an emulsifier, or by coagulation of the emulsion, or by curing of the prepolymer(s).

3,857,230

The invention can be adapted to produce a product of particularly high bulk. For this purpose the filamentitious structures are oriented by stretching before the application of the polymer rings and maintained oriented during the such application, and that — subsequently — different filamentitious structures are subjected to different shrinkage to develop a bulk. The best results are obtained by use of filamentitious structures from different substances which exhibit different tendencies to shrinkage. The substances need not be from chemically different polymers, but may be from the same polymer but in different grades.

However, it is also possible to cause the different shrinkage by uneven heating (and/or swelling) of different portions of the bunch.

The invention will hereafter be described in further detail with reference to the drawings, of which

FIG. 1 is a photo showing in 4 times magnification a yarn of the invention bound with rings and consisting of bicomponent crimped fibres which are of different lengths between the rings,

FIG. 2 is a schematical representation of the preferred embodiment of the product where the filamentitious structures have different lengths between the rings,

FIG. 3 shows, in perspective and schematical view, a process line for binding a bunch with rings at intervals, FIG. 4, shown in longitudinal view, is a detail of the extruder die for the spotwise supply of polymer in the line of FIG. 3,

FIG. 5 is a transverse section along I—I of FIG. 4.

In FIG. 2 a bunch of many filaments or staple fibres are bound together by the ring-formed entwined polymer strips, 1, 2, and 3, which form rings. The filaments or staple fibres, 4, 5, 6, and 7 are comparatively long, as measured from one edge of a ring to the adjacent edge of an adjacent ring. These long filaments or fibres form a kind of loops and tend to elongate the entire bunch, while the more contracted filaments or staple fibres, 8 and 9, tend to make the entire bunch shorter. For the sake of clarity, the rest of the filaments, e.g. 10, are only indicated as “whiskers” in the immediate neighbourhood of the rings, but should be understood as generally occupying the entire zone between adjacent rings with no or relatively few loose ends. Some of these filaments or fibres, which are only partly shown, should be relatively long, and others relatively short. Of course, it is also possible to use a range of many different lengths in each intervening zone.

The filaments or fibres, 8 and 9, are shown as really straightened out, but could also be of helical configuration as obtained by shrinkage of conjugantly spun filaments or fibres from two components in side-by-side relationship. (Each filament or fibre will then alternate between left-turning and right-turning helices). In similar manner, the “loop-forming” filaments or fibres, 4, 5,6, and 7 can also be of helical configuration although they must of course be less contracted than 8 and 9.

Due to the “loop-effect” the structure exhibits, as it has proven, a high and resilient bulk. Furthermore, the firm binding at intervals provides for a high resilience in respect of bending of the yarnlike product.

In FIG. 3 a twistless raw-yarn or similar, 11, is shown taken from a bobbin, 12, but could of course be taken directly from a card or an extrusion device. 11 can be any kind of raw-yarn or similar, even a single, relatively narrow film. From a set of driven feed rollers, 13 14, and 15 the yarn is fed into a zone where it is kept in twisted and revolving condition by means of a falsetwist device consisting of the section-formed, driven rollers, 16 and 17. These rollers rotate as shown by the arrows, 18 and 19, and at the same time each section, when passing the nip, is moved at a constant velocity in the directions shown by the arrows, 20 and 21, respectively, i.e. the two rollers, 16 and 17 constantly act in different directions on the yarn, hereby producing a false-twist. Having passed the nip, each section is reverted to be ready for the same twisting action when it again meets the nip. These reciprocations, synchronized with the rotations, are guided by a set of camdevices. For a more detailed description of the falsetwist rollers, see the article “False Twist and Stretching Process for Tape”, in “Plastics Rubbers”, Jan. 22, 1970. This device is particularly fast, enables simultaneous treatment of many yarns, and a high tension in the zone of twist. It is of advantage to establish such a tension in order to overcome the friction from the supply means which counteract the revolution of the yarn.

In the zone between the feed-rollers, 14-15, and the sectionformed rollers, 16-17, the yarn, here numbered 22, will be in twisted and revolving condition, but having left the section-formed rollers, 14-15, the yarn, here numbered 23, will again be twistless. The application of the rings, 24, is carried out by means of a kind of printing roller, 25, which is rotated so as to follow the advance of the yarn, 22. This printing roller, however, is also an extrusion die, see the more detailed FIGS. 4 and 5. The molten polymer is fed from the extruder, 26, through a fitting 27, and into a central die part, 28, which does not follow the rotation of 25.

For the sake of clarity, FIG. 3 only shows the processing of one yarn, but in actual fact several yarns should be processed simultaneously, as it also appears from the construction in FIG. 4.

In order to distribute the molten polymer between the different yarns, the central die part, 28, houses a distribution chamber, 29, supplied with a number of slots, 30, which are evenly distributed along the length of the “printing roller”. Each slot, 30, feeds an array of radial channels, 31, in the rotating roller, 25, each array of channels terminating in a circular row of orifices from which the “printing” takes place. There is sealing between the fixed central die part, 28, and the rotating roller, 25, and the extrusion through each channel, 31, takes place in pulsations when the orifice is in the position for “printing”.

In order to ensure a smooth distribution of the polymer in each spot, each row of orifices is placed at the bottom of a semi-cylindrical groove, 32, the diametre of which is only slightly bigger than the diametre of the twisted yarn, 22. The resistance against the revolution of the yarn is minimalized by only letting the yarn contact the “printing roller” over a short distance, however long enough to make the yarn turn not less than one revolution around itself during the contact in order to form a well-shaped ring.

To obtain this it is furthermore essential to rotate the “printing roller” at such a speed that the orifices exactly or almost exactly follow the advance of the yarn. For the sake of clarity, the drive is not really shown, but only indicated by the arrow, 33.

Further, the die is heated for the extrusion, but the heating elements are not shown. Neither are shown the thread guides before the feed roller, 13, and before the

3,857,230 “printing roller”, 25, which keep the different yarns spaced apart and ensure a safe guiding of the yarns to the grooves, 32.

Between the “printing roller”, 25, and the false-twist rollers, 16 and 17, the rings, 24, are strongly cooled by means of a water spray or a water bath (not shown). A cooling bath, however, must be so constructed that any substantial hindrance against the revolution of the yarn, 22, is avoided.

To avoid squeezing of the rings, the section-forming rollers, 16, and 17, must be coated with soft rubber, or a more practical measure is to supply one or both surfaces with grooves which are spaced at the same distance from one another as the distance between the rings, 24, at the same time as the “printing roller”, 25, and the false-twisting rollers, 16 and 17, are syncronized in such manner that the rings, 24, will fit into said grooves and a squeezing of the rings hereby will be prevented.

After the false-twist rollers, 16 and 17, follows a set of driven pull-rollers, 36 and 37, which assist the falsetwist rollers, 16 and 17, in setting-up a tension in the yarn, 22, while the latter is guided in revolving state over the “printing roller”, 25. As already mentioned, this tension is set-up to overcome the resistance against said revolution.

If the raw-yarn, 11, consists of filaments, fibres or other filamentitious structures of different substances, and if there is established a high tension before and/or during the false-twist, then there will generally spontaneously develop a bulk when the tension is released in twistless state. This is indicated at 34 before the spooling on the bobbin, 35, and is due to different shirnkage of the different substances. To further promote such different shrinkage, an oven can be provided for in the line after the rollers, 36 and 37, but a heat treatment to develop the bulk can of course also be carried out during respooling of the yarn or in the final textile product.

To produce short lengths for use as feather or down substitute, the bobbin, 35, is substituted by a cutting device, which is syncronized with the “printing roller”, so as to cut regularly between the rings.

Yarnlike products manufactured according to the invention may be applied for a great variety of textile and technical purposes, and the applications range from the highest fineness used of yarn, i.e. about 20 denier, to the coarsest yarn, i.e. about 100 denier, with preference, however, for the range from about 500 denier to about 30.000 denier. The examples below illustrate different applications.

EXAMPLE 1

This example illustrates the use of the invention to manufacture a bulked effect-yam for curtains.

The raw-yarn consists of bicomponent filaments from polypropylene and polycaprolactame bonded in sideby-side relationship by means of a thin layer of an ionomer polyethylene which exhibits adhesive properties. The raw-yarn is produced by the method and apparatus explained in the article “Split Film Gets a Second Look”, in “Textile Industries”, July 1969. Due to casual irregularities of the dieparts the fibres in the yarn exhibit different crimpability, after stretching, and the distribution of the differences is almost at random. The average fibre denier is about 20 and the yarn denier about 4.000.

By means of a laboratory line as shown in FIG. 3, short rings of polypropylene are applied at a mutual distance of 2 cm. The melt index of the polypropylene is 10 according to ASTM D 1238-62T, condition K. In order to obtain a smooth “print” it has proven advantageous to use such a relatively low-viscous grade. The rings are cooled in a water bath. The false-twist is carried out with 6 turns perl 0 cm.

The bulk is developed by heating to 120°C in relaxed state by which each of the filaments crimps in helical manner, but to different degrees. The look of the yarn is almost as shown in the photo, FIG. 1. The yarnlike structure is used as weft in a fabric with fine nylon threads as warp, whereby a very attractive visual effect is obtained.

EXAMPLE 2

This example illustrates the use of the invention to manufacture a feather substitute for filling of pillows or quilts, staple

For this purpose the raw-yarn should be a carded blend of 4 denier monocomponent polyethyleneterephthalate staple fibres and 4 denier bicomponent polyethyleneterephthalate staple fibres, again in a yarn denier of about 4.000. The materials for the rings should be a copolymer of polyethyleneterephthalate and polyethyleneglycol of melting point 180°C and melt index 2 according to the same ASTM specification, but condition E. The rings should be applied as thin and short as possible and at a spacing of 4 cm. After elimination of the twist the yarn should be cut between the rings to short lengths, each comprising 2 rings, and the bulk developed by heating.

EXAMPLES

This example illustrates the use of the invention to manufacture a grass substitute.

As raw-yarn is used two flat, network-formed webs, each formed by needle-fibrillation of oriented film. One is made from polypropylene and the other one from polycaprolactame. Each has an average fibre denier of about 50 and a yam denier of about 2.000.

The two flat networks which are taken from two spools are assembled one on top of the other without any adhesion, and are fed into the line of FIG. 3. The polymer for the rings, and the process is the same as in example 1, but by means of wider orifices the rings are made about 3 mm long, and the spacing between the rings is 1 cm.

The resulting product, after heat treatment at 120°C, shows high resilience and a stable high bulk and is suitable as a tufting product for sport-fields, etc.