GB1590126A

GB1590126A - Method of bulking yarns

Info

Publication number: GB1590126A
Application number: GB5113876A
Authority: GB
Original assignee: Booth B H
Current assignee: Booth B H
Priority date: 1977-11-23
Filing date: 1977-11-23
Publication date: 1981-05-28

Description

(54) METHOD OF BULKING YARNS (71) I, BETTY HOLMES BOOTH, a British subject of Rose Bank, Station Road, Oxenhope, Keighley, West Yorkshire, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in the following statement: This inevntion relates to a method of bulking multifilament yarns of synthetic textile fibres, and to a package therefor.

Synthetic continuous multi-filament yarns are simple and economical to produce, but their appearance handle and thermal properties are such that they are more acceptable to the consumer after further treatment. This usually takes the form of crimping or texturising the filaments to impart crimp to individual filaments and make a yarn assembled from such filaments more bulky, and thus resemble more closely a natural fibre yarn. Texturised yarns have a more natural handle and appearance than untreated continuous filament yarns, and being more bulky, have better thermal insulation properties. This, coupled with the strength of synthetic fibre yarns, makes them ideal for use in knitted, woven and non-woven fabrics.

The invention seeks to provide a simple and economical method of bulking multifilament yarns in a controllable manner, capable of producing high or low bulked yarns or fancy effects, and further to provide a convenient package for the bulked yarn.

According to the present invention there is provided a method of bulking multifilament yarns of synthetic textile fibres which comprises knitting an undrawn or partially drawn yarn into a fabric, shrinking the fabric a predetermined amount onto a former by the action of heat, and de-knitting the yarn.

During the heat-shrinking step each of the filaments of the yarn is set into the loop shapes of the knitted fabric, and retains this shape on de-knitting. As the yarn is pulled from the fabric in the deknitting step, it is gripped by the next adjacent loop. The frictional resistance on each of the filaments is different depending on its position within the yarn, and the result is that most of the component filaments are pulled out of the fabric out of phase with one another causing a high degree of bulking in the de-knitted yarn.

Should the filaments be de-knitted in phase, the yarn would not be bulked but would merely have a sinusoidal or castellated appearance, with each of the fibres following the same path as its neighbour.

The synthetic textile fibres to which this invention relates are primarily polyamides or polyesters, especially the latter. As mentioned the material should be undrawn or partially drawn filament, not set or stabiized, and should preferably have a shrinkage characteristic of at least 30%.

The knitting process may be carried out by any method of machine knitting which allows unravelling, or de-knitting, by pulling one end of the yarn from the knitted fabric. For this reason weft knitting is preferred, and a plain knit fabric is ideal, although more complicated knit structures may be employed to give special crimp effects to the yarn. The knitting may be carried out on a flat-bed or circular machine, but the latter is preferred since it knits under easily controlled, relatively constant tension, at higher speeds, and conversion costs may be lower.

The shrinking step may be carried out by any conventional method, such as immersing in boiling water, steaming or baking. A former or core is used to limit the shrinkage of the fabric, because if the fabric is allowed to shrink fully the loop structure will become so tight that it is impossible to de-knit successfully without an unacceptable amount of yarn breakages.

The degree of heat-shrinking will, in combination with the count of the yarn, determine the fineness or coarseness of the crimp set in the filaments: the more shrinking, the more crimp. The size of former will therefore determine the amount of crimp, and thereby the amount of bulkiness.

The shape of the former may be varied so that the fabric shrinks in different amounts in different areas, giving a fancy yarn effect to the resultant de-knit yarn.

Similarly, part only of the fabric can be heat-shrunk, again giving the de-knit yarn fancy effects.

De-knit yarn according to the invention may have very high bulk and is therefore especially suitable for providing thermal insulation, e.g. in bedsheets, blankets, drapings and quilts. For these purposes undrawn or partially drawn fibre of low quality, which would normally be considered waste, may be used. Of course, the de-knit yarns may be used in any way that texturised yarns are currently used, e.g.

for machine knitting, weaving and nonwovens.

An aspect of the invention is that the bulked yarn may be used directly from the heat-shrunk fabric (hereinafter referred to as the "package") for a number of enduses, e.g. hand knitting, or for warping up for subsequent processing. Then the undrawn or p.o.y. (partially orientated yarn) is merely knitted, and the fabric heatshrunk; the fabric itself (which is fairly rigid when shrunk) provides the package for the yarn and rewinding or balling is not necessary. Again, circular knitting is preferred to produce a tubular fabric or "sock". The user, e.g. a domestic handknitter, merely pulls the end of yarn and starts knitting directly from the package, which is especially suitable for use in hand knitting.

Thus the invention also provides a bulked yarn package which comprises a fabric knitted from undrawn or partially drawn synthetic multifilament yarn and heat shrunk onto a former. The package of the invention will be available under the trade name "Crimpac".

Any count of yarn which can be knitted may be used in the process of the invention, from very fine counts up to relatively coarse counts, limited only by the gauge of the needles.

Garments hand knitted from de-knit yarn of the invention were aesthetically pleasing and had good thermal insulation properties. For handknitting it is preferred to make the package from p.o.y. multifilament, although undrawn multifilament may also be used.

Non-woven formations are currently being used in a multitude of products such as car seat covers, furniture covers, surgical dressings, interlinings, soil stabilizing, sheeting, road reinforcement sheeting, filters, drapings, etc. In all or almost all of these it is most desirable that the fibrous web, which is usually the base of non wovens, should be of uniform thickness and density, this should be maintained throughout the web in both "warp" and "weft" directions. Of the present day methods now employed in making web formations, the most usual is carding.

By this method it is very difficult to achieve the desired uniformity and quality owing to many reasons such as: carding faults, the subsequent layering of the web, the intermittant feed from the hopper, and pebble effects. Also a carded web has relatively poor stability and presents handling problems in subsequent processing.

Using de-knit yarns of the invention the foregoing difficulties do not arise because the carding method is not used. Fibrous webs may be produced according to the invention by laying side by side, preferably in a parallel manner, the bulked yarns as the, are drawn from the packages of the invention.

This is achieved by using a conventional sectional warping machine. The number of packages to be used depends upon the number of ends required in each section.

The package may be conveniently placed in the position usually occupied by the creel.

A revolving swift or balloon overcomes the de-knitting resistance and pulls the crimped yarn under tension from the package. Because of this tension, the yarn has not yet been allowed to become lofty although it is already crimped. In this manner a web of any desired density, weight, length and width can be built up onto the swift. The sheet of web, still under tension, can then be run off from the swift to a subsequent process. At this stage the tension of the yarns is relaxed allowing the yarns to become lofty for the subsequent process, e.g. for adhesive application or needle punching, for quilt making or other formation for which non-woven webs are currently being used. Because it is less expenive, it is preferred to start with undrawn yarn for non-woven end-uses.

The same procedure as described above may be employed to make up a warp beam for weaving. In this case the sheet of yarn is taken from the swift by beaming off in the conventional warping manner. The beam of yarn can then be placed in a loom for weaving.

The process of the invention may be carried out in a continuous manner by using knitting machinery which has a knitting zone, a heating (e.g. steaming) zone and a de-knitting zone. The heating zone shrinks the knitted fabric and acts as the core or former from which the yarn is continuously de-knitted and wound onto a conventional cone or cheese.

The invention will be illustrated further by the following Examples; Example I - from undrawn yarn.

An undrawn nylon mutifilament yarn plied up to 4000 D/Tex was knitted on a 42" diameter, single feed circular knitting machine having 6 needles per 1". This yarn has a shrinkage potential of approx. 40% when subjected to heat. The knitted fabric was shrunk onto a former in boiling water to form a package of the invention. The yarn was then de-knitted by pulling the end from the shrunk fabric (hereinafter called the "package"). The resultant yarn was of very high bulk and capable of withstanding lengthwise pull without breaking.

The length of the de-knitted yarn pulled from 1 metre of "package" was 500 metres.

Example 2 - from P.O.Y.

Partially drawn (P.O.Y.) polyester multifilament yarn up-plied to 4000 D/Tex: was knitted on the above mentioned circular machine. This P.O.Y. yarn has a shrinkage potential of approx 60%. After heat treatment in boiling water at 1000C on a former the deknitted yarn had no significant increase in bulkiness when compared with that of Example 1 but the length of deknitted yarn pulled from 1 metre of "package" was 525 metres.

WHAT I CLAIM IS: 1. A method of bulking multi-filament yarns of synthetic textile fibres which com- prises knitting an undrawn or partially drawn yarn into a fabric, shrinking the fabric a predetermined amount onto a former by the action of heating and de-knitting the yarn.

2. A method as claimed in claim 1 in which the synthetic textile fibre is a polyamide or a polyester.

3. A method as claimed in either of claims 1 or 2 in which the filament has a shinkage characteristic of at least 30%.

4. A method as claimed in any of claims 1 to 3 in which the knitting step is carried out on a weft knitting machine.

5. A method as claimed in claim 4 in which the knitting machine is a circular knitting machine.

6. A method as claimed in any of claims 1 to 5 in which the fabric is a plain knit fabric.

7. A method as claimed in any of claims 1 to 6 in which the shrinking step is carried out by immersion in boiling water, by steaming or by baking.

8. A method as claimed in any of claims 1 to 7 in which part only of the fabric is heat shrunk.

9. A method as claimed in any of claims 1 to 8 in which the former is shaped so that the fabric shrinks different amounts in different areas.

10. A bulked yarn package which comprises a fabric knitted from undrawn or partially drawn multi-filament yarn of synthetic textile fibres and heat shrunk onto a former.

11. A package as claimed in claim 10 in which the synthetic textile fibres are polyamide or polyester.

12. A package as claimed in either of claims 10 or 11 in which the fabric is a plain, circular-knitted fabric.

13. A method of producing a fibrous web which comprises laying side by side bulked yarns drawn from packages according to claim 10.

14. A method of bulking multi-filament yarns of synthetic textile fibres substantially as hereinbefore described with reference to as illustrated in the foregoing Examples.

15. A bulked yarn package substantially as hereinbefore described with reference to and as illustrated in the foregoing Examples.

16. A method of producing a fibrous web from yarn bulked according to claim 1 and substantially as hereinbefore particularly described.

17. A bulked yarn whenever made according a method as claimed in any of claims 1 to 9 or 14.

18. A woven, knitted or non-woven fabric or formation made from yarns according to claim 17.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. An undrawn nylon mutifilament yarn plied up to 4000 D/Tex was knitted on a 42" diameter, single feed circular knitting machine having 6 needles per 1". This yarn has a shrinkage potential of approx. 40% when subjected to heat. The knitted fabric was shrunk onto a former in boiling water to form a package of the invention. The yarn was then de-knitted by pulling the end from the shrunk fabric (hereinafter called the "package"). The resultant yarn was of very high bulk and capable of withstanding lengthwise pull without breaking. The length of the de-knitted yarn pulled from 1 metre of "package" was 500 metres. Example 2 - from P.O.Y. Partially drawn (P.O.Y.) polyester multifilament yarn up-plied to 4000 D/Tex: was knitted on the above mentioned circular machine. This P.O.Y. yarn has a shrinkage potential of approx 60%. After heat treatment in boiling water at 1000C on a former the deknitted yarn had no significant increase in bulkiness when compared with that of Example 1 but the length of deknitted yarn pulled from 1 metre of "package" was 525 metres. WHAT I CLAIM IS:

1. A method of bulking multi-filament yarns of synthetic textile fibres which com- prises knitting an undrawn or partially drawn yarn into a fabric, shrinking the fabric a predetermined amount onto a former by the action of heating and de-knitting the yarn.