EP1990453A1

EP1990453A1 - Non-run fabric with elastic properties based on polypropylene fibre

Info

Publication number: EP1990453A1
Application number: EP08155995A
Authority: EP
Inventors: Leonardo Polli; Paolo Tagliabue; Luca Cristini
Original assignee: MITI Manifattura Italiana Tessuti Indemagliabili SpA
Current assignee: MITI Manifattura Italiana Tessuti Indemagliabili SpA
Priority date: 2007-05-11
Filing date: 2008-05-09
Publication date: 2008-11-12
Also published as: ITMI20070963A1

Abstract

Elastic knitwear fabric for sports use produced with non-run knitwear machines with chain fabric, in which a non-elastic polypropylene-based yarn is coupled with an elastic yarn based on olefin copolymers of the type known with the trade-name "Elastolefin", which is then stabilized under heat and humidity.

Description

The present invention relates to the production of non-run fabrics for sportswear. It is known that for fabrics destined for bathing or active sports apparel, it is preferable to use non-run and elasticized fabrics, resorting to the combination of elastic and non-elastic yarns. Compared with fabrics produced with circular machines, fabrics produced with these coupled yarns operating with non-run knitting machines with chain fabric have much better characteristics with respect to modulus, tear resistance, resistance to abrasion and pilling, in addition to an improved covering and compactness with the same weight. Finally, the fabrics obtained with weft/warp spinning have much lower elasticity properties.
The use is known, for example, according to patent EP 826.809 , of said non-run knitting machines with a plaiting of opposing yarns, in which the two yarns consist of nylon or polyester multifilament yarns, possibly combined with cotton, as non-elastic yarn, and an elastomer such as Lycra as elastic yarn. For its end-use, the knitted fabric thus produced is then thermofixed by hot, dry treatment, thus creating a lattice which stabilizes the non-run fabric. Generally speaking, in thermofixing, the elastomeric yarn is brought close to its softening point and connected by adhesion points to the fabric thus formed, thus determining its rest length, equal to that in which it was thermofixed. The final elasticity of the fabric therefore depends on the tension given to the elastic yarn during its thermofixing.
The thermofixing operation is generally effected starting from the fabric wound in rolls or beams, winding and passing it continuously in a hot dry environment at temperatures of 180-200°C for times in the order of tens of seconds. The thermofixed fabric is then rewound and sent to the subsequent processings.
These chain woven products have good initial characteristics but, when destined for sports use and in particular for bathing costumes, they have a short duration, due to both the short life of the elastomer and the poor colour fastness: these phenomena can be attributed to the hypochlorite present in swimming-pools, and also to attack on the part of creams, sun-tanning oils and perspiration combined with each other and with solar radiation.
For use in these elasticized fabrics, polypropylene fibre is extremely suitable for its lightness, colour stability, immediate drying capacity, bacteriostaticity, resistance to chemical agents, oxidants and solar radiation. Attempts at this use, however, have so far had little success as the critical point for coupling polypropylene fibre and elastomeric fibres such as Lycra is due to the impossibility of thermofixing the elastomer. Polypropylene fibre cannot be subjected to dry processing at thermofixing temperatures. At much lower temperatures, for example even over 100°C, polypropylene fibres deteriorate, becoming plasticized and irremediably deteriorating.
The combination between polypropylene and elastomer has been effected in weft/warp weaving obtaining, however, a fabric having a poor elasticity and therefore quite unsuitable for use in sportswear as described above. The same combination in a circular machine produces a laddered material have poorer qualitative characteristics for use, and also unstable and with uncontrollable curling. These latter defects can also be found in fabrics produced with linear machines in non-run weaving for chain fabrics, using the technique previously described, in which a high percentage of elastomer is used in relation to the elasticity to be obtained, due to the impossibility of proceeding with thermofixing as is possible, on the contrary, with other fibres, such as nylon or polyester.
The technical problem faced with the present invention consists in exploiting the positive characteristics of polypropylene yarns for elasticized sports fabrics. The objective of the present invention is to effect a coupling of polypropylene yarn with another fibre to produce a non-run and elastic fabric which can be stabilized without resorting to the thermofixing mentioned above. The fabric according to the invention is defined, in its essential components, in the first claim whereas its variants and preferred embodiments are specified and defined in the dependent claims.
In order to better illustrate the characteristics and advantages of the present invention, it is described with reference to some of its typical embodiments indicated in figures 1 to 3 for illustrative and nonlimiting purposes: said figures refer to the production of the elastic fabric according to the invention.
The fabric according to the invention is produced in non-run weaving, by combining a multifilament polypropylene yarn with an extendable yarn based on olefin copolymers of the known type, known with the general trade-name "Elastolefin" or with analogous yarns.
Copolymers of the Elastolefin type based on ethylene and other olefins are suitable for cross-linking to establish transversal bonds between the chains, which give elasticity to the yarns produced with said copolymers. This type of yarn in fact has a less nervous behaviour and is different from the elastomeric yarns of the Lycra type, normally used in the technique of non-run elastic fabrics of the sports type.
The polypropylene yarn is a multifilament yarn with a titer of 20 to 167 dtex, and preferably from 40 to 70 dtex. According to a perfected embodiment of the present invention, the polypropylene yarn is a smooth multifilament yarn. The extendable yarn of the Elastolefin type, on the other hand, is a yarn based on olefin copolymers with a titer of 22 to 78 dtex. This yarn can be monofilament or multifilament.
The weaving process is effected in a single-section non-run knitting machine, with loom gauges 28, 32 and 40, fed with 2,3,4 beam-wound yarn feedings and presented in looping with weaves of 2,3,4 combs or guide needles cooperating with a needle bar in an alternating vertical movement and with sinkers in an alternating transversal movement according to a known operational scheme.
With reference to figures 1 to 3, these illustratively describe looping plaitings which form the elasticized fabric according to the invention.
Figure 1 illustrates some of the possible basic weaves, or basic schemes, to be combined in pairs with each other to obtain the looping or plaiting of the yarns for producing the elastic fabric according to the invention. The numbers 0,1...5 indicate the spaces between the needles, which in turn are illustrated with black points which move in a vertical direction orthogonally with respect to the plane of the figure.
The basic weaves of figure 1 from A to D show weaves for closed stitch plaiting with the thread ferrule which closes on the needle with respectively:

A: weave 10/12 closed stitch
B. weave 10/23 closed stitch
C: weave 10/34 closed stitch
D: weave 10/45 closed stitch

The weaves of figure 1 from E to H, on the other hand, show weaves for open stitch plaiting with the thread ferrule which does not close on the needle, but only borders it, with respectively:

E: weave 01/21 open stitch
F: weave 01/32 open stitch
G: weave 01/43 open stitch
H: weave 01/54 open stitch

The elastic fabric according to the invention is illustratively produced by coupling two different weaves and preferably keeping the Elastolefin based on olefin copolymers, or an analogous elastic thread, for the weaves with a shorter pitch and the polypropylene yarn for the weaves with a longer pitch.
The longer the pitch of the non-elastic chain-looped thread bridles, the more the thread bridle appears to be non-elastic and the less the elastic thread can be seen: the end-fabric has a softer appearance and feel. These fabrics are suitable for producing plush and relax sweatshirts.
The shorter the pitch of the thread bridles, the more compact the fabric is. Intermediate solutions have also been proposed in the known art, with weaves which give bridles having variable lengths, alternating longer and shorter bridles on the same thread, indicated for example in the above-mentioned patent EP 826.809 .
Closed stitch weaves require a greater thread consumption, they give a heavier, more resistant and uniform fabric and allow lower operating rates. Open stitch weaves allow higher operating rates and the possibility of effecting patterns on the fabric, but they give a lighter and less resistant fabric. Intermediate solutions are also proposed in the known art, with mixed stitch weaves, alternating closed and open stitches on the same thread, indicated for example in the above-mentioned patent EP 826.809 .
Figure 2 illustratively shows two weave couplings for producing the basic plaiting for an elastic fabric particularly suitable for bathing costumes, with a good coverage and compactness, generally called "charmeuse". The dashed line indicates the Elastolefin yarn, whereas the continuous line indicates the polypropylene-based yarn.
The weaves B and A of figure 1 are jointly used herein, both closed stitch weaves, with a 10/23 weave for the polypropylene yarn, with bridles equal to two pitches, and 10/12 weave for the Elastolefin yarn. In figure 2 M indicates the coupling of the basic plaiting of the two yarns in counter-phase, to obtain an elastic charmeuse, in which the two different yarns are never wound onto the same needle but always around different needles. The coupling M in counter-phase produces a smoother fabric having a more harmonious behaviour. In figure 2, N indicates the basic coupling of the two yarns in a phase in which, for every two rows, the two different yarns are wound onto the same needle, whereas in the intermediate rows they are wound onto different needles. The coupling N in phase produces a more processed fabric. It should be pointed out that, with the basic weave of figure 2N, the two threads wound onto the same needle every two rows are subjected to tension in the same direction.
Figure 3 shows the overall drawing of the chain stitch, normally called "charmeuse designing", obtained with repetition on the whole front of the machine of the weave of the guide needles according to the basic scheme shown in figure 2M, with coupling of the two yarns in counter-phase. In the overall chain stitch fabric obtained, each needle is wound with closed stitch by both yarns, in which the two yarns are wound onto the needle coming from opposite directions. The two crossing tensions are counter-balanced and produce a stable, balanced fabric which has no preferential deformation.
The fabric produced with basic weaves of the closed stitch type and in counter-phase represents a preferred embodiment of the present invention with respect to the use of polypropylene-based non-elastic yarns and Elastolefin yarns for producing bathing costumes according to the present invention.
A specific characteristic of the present invention is the wet stabilization process of the fabric thus produced which allows the connection between the stitches of the polypropylene non-elastic yarn and the stitches of the extendable Elastolefin yarn. Unlike the elasticized fabrics of the known art, in this stabilization process, the fabric is heated under humidity and to moderate temperatures without subjecting the polypropylene yarn to plasticization and deterioration, but still creating adhesion points between the stitches in the fabric thus formed in the chain knitting machine. The stabilization process of the fabric according to the invention is defined, in its essential elements, in claim eight whereas its variants and preferential embodiments are specified and defined in its dependent claims.
In its essential lines, the stabilization of the elastic fabric based on polypropylene and Elastolefin yarn according to the invention is effected on a piece of fabric operating batchwise and under wet conditions. One or more pieces of fabric, still beam rolled or "cord" unrolled, are introduced into a closed container, for example an autoclave, in which said pieces are impregnated with water and subjected to moderate temperatures, generally from 60° to 100°C. With polypropylene yarns and operating under wet conditions, slightly higher temperatures would still be possible but they would not give a better stabilization effect. The treatment times are in the order of tens of minutes: generally from 20 to 60 minutes of treatment. After stabilization, the fabric is dried in a hot chamber: for example so-called "rameuse" fed with a stream of hot air and which operates on the extended fabric. The piece of fabric thus dried and extended is re-rolled on beams or rolls and transferred to the subsequent processing.
The non-run sports fabric based on polypropylene fibre according to the present invention has considerable advantages and improvements with respect to the fabrics of the known art. Among these, the characteristics of coverage and compactness, colour resistance and resistance to attack of the extendable fibre on the part of the sodium hypochlorite present in swimming pools, are significant. The fabric obtained according to the present invention has characteristics which are entirely suitable for all sporting activities. It is in fact resistant to chemical aggressions caused by sweat, sun-tanning oils and creams and solar radiations.
The fabric according to the invention has properties of comfort and adaptability which allow it to be advantageously used also for medical applications, underwear and outdoor clothing. The characteristic that this fabric can be completely recycled as it totally consists of polyolefins, makes it extremely interesting.

Claims

Elastic knitwear fabric produced starting from a combination of non-elastic yarns with elastic yarns with non-run knitting machines with chain fabric, fed with several yarn feedings wound in beams and presented in looping with a series of combs cooperating with a needle bar in an alternating vertical movement and with sinkers in an alternating transversal movement, characterized in that one of said combined yarns is a multifilament polypropylene yarn and the other of said combined yarns is a yarn of olefin copolymers of the type known with the trade-name of "Elastolefin" or an analogous yarn having an equivalent behaviour.
The elastic fabric according to claim 1, characterized in that the polypropylene yarn is a multifilament yarn with a titer of 20 to 167 dtex, and preferably from 40 to 70 dtex.
The elastic fabric according to claim 1, characterized in that the polypropylene yarn is a multifilament smooth yarn.
The elastic fabric according to claim 1, characterized in that the yarn of the Elastolefin type based on olefin copolymers has a titer of 22 to 78 dtex.
The elastic fabric according to claim 1, characterized in that the yarn of the Elastolefin type based on olefin copolymers is a monofilament yarn.
The elastic fabric according to claim 1, characterized in that for its application for bathing costumes it is produced with basic weaves of the closed stitch type and in counter-phase.
The elastic fabric according to claim 6, characterized in that it is looped with 10/23 weaves for the polypropylene yarn, with bridles equal to two pitches, and with 10/12 weave for the Elastolefin yarn.
A process for the production of an elastic knitwear fabric for sportswear starting from a combination of non-elastic yarns with elastic yarns with non-run knitting machines with chain fabric, fed with several yarn feedings wound in beams and presented in looping with a series of combs cooperating with a needle bar in an alternating vertical movement and with sinkers in an alternating transversal movement, characterized in that one of said combined yarns is a multifilament polypropylene yarn and the other of said combined yarns is a yarn of olefin copolymers of the type known with the trade-name of "Elastolefin" or an analogous yarn based on olefin copolymers and that the stabilization of the elastic yarn is effected on a piece of fabric operating batchwise and under wet conditions at temperatures ranging from 60° to 100°C.
The process for the production of an elastic fabric according to claim 8, characterized in that the stabilization is carried out on one or more pieces of fabric in an autoclave, in which said pieces are impregnated with water and subjected to treatment for 20 to 60 minutes.
The process for the production of an elastic fabric according to claim 8, characterized in that after the stabilization the fabric is dried in a rameuse fed with a stream of hot air, operating on the extended fabric and subsequently rewinding the fabric thus dried.