EP0504072B1 - Opaque elastic knitwear - Google Patents

Abstract

Elastic knitting material with the appearance of voile and process for obtaining it. The knitted material is made up of two different, polyamide-based yarns, of substantially identical covering in the stretched state, arranged unconventially, one of the yarns being a conventional textured yarn or moss yarn, and the other a torque yarn or stretch yarn, the moss yarns and the stretch yarns being placed alternately relative to one another, each type of yarn being present in the form of Z twist and of S twist according to the following order: 2 Z twist yarns, 2 S twist yarns or 2 S twist yarns and 2 Z twist yarns. The knitted material obtained is balanced and free from stripes. <IMAGE>

Description

The present invention relates to an elastic knit having a veil appearance.

There are essentially two types of stockings and tights made from textured threads: foam and veils.

Foam stockings and tights are obtained from classic textured false twist yarns or foamed yarns. They have a large volume, crimp and elasticity. The knits prepared from these threads are flexible and soft but the tights obtained are covering and opaque. The elasticity of the tights is obtained by the combination of the elasticity of the threads and the geometry of the stitches.

Foam tights, very elastic, therefore have an unflattering appearance.

Sheer tights, on the contrary, are light and transparent. They are obtained from non-swelling, "stretch" or "torque" yarns, which are generally multifilaments with large strands (4 to 7.5 dtex / strand), little or not bulky, having the appearance of 'a flat wire. These threads have a crimp and elasticity which are low to zero but a significant torque effect which gives them nervousness and aptitude for twisting. It is the nervousness and the ability to twist which, when used in hosiery give the product: stockings, tights ... its elastic character. In general, their production process consists in subjecting the wires to a low level of torsion and / or to a heat treatment at a lower temperature than for the foamed wires. They can be obtained by texturing by false twist with a skewer or by friction.

Throughout the description, these threads will be entitled "stretch threads".

Flat, without post-forming, the knits obtained from stretch yarns are not very flattering: the stockings and tights are wide, irregular in appearance; they have hollow passages and the meshes are anarchic; the touch is pretty rough because of the title to the strand high yarn used; this strong strand strength is however necessary for obtaining the elastic performance sought after on knitting. On the other hand on the leg the aspect is spider-like and transparent. However, knits obtained from stretch yarns lack elasticity in width (compression); in particular they insufficiently marry the finest parts of the leg (the ankle), and have relatively permanent deformations, in use, at the knee in particular.

On the leg, the veiled tights therefore have a much more flattering appearance than that of foam tights but an insufficient elasticity, clearly less than that of foam tights, their lack of elasticity and compression results in an important aptitude for peeling. .

Furthermore, the lack of elasticity of the knits does not allow to correctly cover all the measurements, the industry of stockings and tights being limited to 3 or 4 standard sizes to limit the cost of the articles.

We have tried (CH-A-340941) to improve the elastic performance of existing stretch stockings and tights by increasing the torque effect and therefore the inclination of the mesh. If the veil aspect is thus preserved, very quickly a maximum inclination of the stitches is obtained and a bad flat appearance of the knit is obtained which is then unbalanced (inverted stitches).

It has also been proposed to modify the appearance of knitting by using different yarns, one of which has a round section and the other a Y-shaped section (Swiss Patent No. 384,123). However, this knit does not have good elasticity and its appearance does not correspond to a veil appearance.

In order to improve the elastic performance of the knitted fabrics, it has also been tried to weave or vanize the article with an elastane thread; that is to say to introduce on the loom, in parallel, an elastane thread and a flat polyamide thread, alternating with a flat polyamide thread.

However, the knits thus obtained are more expensive and more difficult to implement because of the presence of the elastane thread which is difficult to handle and to work.

The subject of the present invention is a knit that is both elastic, similar to foam knit, and moreover has a veil and transparent appearance.

More particularly it relates to elastic knits in the longitudinal and transverse direction having a veil appearance, made up of two different polyamide-based threads, this knitting is characterized in that one of the threads is a conventional textured thread or foam thread and the other a torque thread or thread stretch.

• i) fil stretch tors Z, fil mousse tors Z/fil stretch tors S, fil mousse tors S.
• ii) fil mousse tors Z, fil stretch tors Z/fil mousse tors S, fil stretch tors S.
• iii) fil stretch tors S, fil mousse tors S/fil stretch tors Z, fil mousse tors Z.
• iv) fil mousse tors S, fil stretch tors S/fil mousse tors Z, fil stretch tors Z.

These wires have a Z twist or an S twist and are present according to the following arrangements below:

• i) Z twisted stretch yarn, Z twisted foam yarn / S twisted stretch yarn, S twisted foam yarn
• ii) Z-twisted foam yarn, Z-twisted stretch yarn / S twisted foam yarn, twisted S stretch yarn
• iii) twisted stretch yarn S, twisted foam yarn S / twisted stretch yarn Z, twisted foam yarn Z.
• iv) S twisted foam yarn, S twisted stretch yarn / Z twisted foam yarn, Z twisted stretch yarn.

In addition, the foam and stretch yarns have a substantially identical title or a different title leading, on knitting, to an identical covering power.

The arrangement i) above is the preferred arrangement of the invention.

The present invention also relates to a process for obtaining knitted fabrics which are both elastic and veil-like, consisting of knitting on a circular loom 4 scraps, two different threads based on polyamide, of cover substantially identical in the stretched state, arranged alternately and unconventionally according to the order of falls 1 to 4: 2 twisted Z wires, 2 twisted S wires or 2 twisted S wires and 2 twisted Z wires.

The final titer usable for obtaining such knits generally varies between 8 dtex and 22 dtex.

It is desirable to use substantially identical stretch and foam cover yarns to avoid the well-known phenomenon of transverse locks or stripes, due to the difference in the nature of the yarns.

• soit des fils de titre sensiblement identique,
• soit des fils de titre différent conduisant, sur le tricot, à l'obtention d'un aspect ou pouvoir couvrant identique.

By cover substantially identical to the stretched state means:

• either wires of substantially identical title,
• or yarns of different title leading, on knitting, to obtaining an identical appearance or covering power.

The foamed yarns used according to the present invention are conventional yarns obtained by false twist texturing preferably having a maximum of elasticity and a minimum of covering. The strands thus chosen have a relatively high strand count, for example of the order of 3 to 6 dtex, and a preferentially low number of strands, 3 to 5 for example. Their elasticity or contraction of crimp E% is greater than or equal to 40%, preferably from 50 to 80% (the measurement being made on a Texturmat commercial device - see the measurement method below, example 1). Their torque effect is weak to very weak.

• sur une flotteuse de 1 m de périmètre, on confectionne un flotillon de 100 m de longueur, on attache les extrémités du fil ;
• on fait glisser le flotillon à l'extrémité des bras de la flotteuse et on accroche une masse de 0,210 g par dtex,
• on enlève le flotillon en prenant soin de ne pas faire de vrille et on laisse la torsion se réaliser,
• on place le flotillon sur un torsiomètre et on compte le nombre de tours,
• on exprime la torsion en tour/mètre.

Stretch or torque threads are obtained by false twist texturing by skewer or friction; they must have a significant torque effect, compatible with the requirements of knitting; for example the torque effect can be between 30 and 70 turns, preferably 50 to 70 turns, depending on the total titer of the wire used. The torque effect is measured according to the following method of the bottle:

• on a float of 1 m perimeter, we make a flotillon of 100 m in length, we attach the ends of the wire;
• we slide the bottle at the end of the arms of the float and hang a mass of 0.210 g per dtex,
• we remove the bottle, taking care not to twist and let the twist take place,
• we place the bottle on a torsiometer and count the number of turns,
• we express the twist in turn / meter.

The torque effect depends on the strand titer, the molecular orientation of the strands, the module, etc.

The E% crimp contraction (Texturmat) of the stretch or torque yarns used is less than 5%.

The stockings and tights made from knitwear according to the invention come from stretch and foam yarns which, surprisingly, are arranged in an unconventional order, while the usual knitting of stockings and tights with a single type of yarn is made by alternating 1 row of twist yarn Z then 1 row of twist yarn S, so as to obtain a flat, balanced knit with good elasticity.

On the contrary, according to the invention, the alternation of tors Z / tors S is replaced by alternation of double tors Z - tors Z / tors S - tors S or alternation of double tors S / tors S then tors Z / tors Z with alternating stretch and foam yarns; preferably, the following double alternation is used: 1 twisted stretch yarn Z, 1 twisted foam yarn Z, 1 twisted stretch yarn S, 1 twisted foam yarn S. The knits thus obtained, despite this double alternation of twists, are balanced and free from scratches; moreover, they are elastic and have a veil, transparent appearance on the leg, as well as good compression, including at the level of the thin parts of the leg. In particular, they have an elasticity very close to that of foam knits.

To obtain a final knit having good dyeing regularity, the foam and stretch yarns used must have a substantially identical dye affinity (kinetics, yield). They can be knitted on any known conventional material, at the usual speeds linked to the material used.

They can be produced from stretch and foam yarns based on polyamide 6 or 66, more particularly polyhexamethyleneadipamide (PA 66) or copolyamide containing at least 85% of hexamethyleneadipamide units and up to 15% of other units obtained in replacing, for example the starting adipic acid with another diacid such as terephthalic acid, sebacic acid, etc., or by replacing the two monomers with caprolactam for example. The starting polyamides may also contain additives such as matting agents, stabilizing agents with regard to light, or with regard to heat, oxidation, additives intended to reduce accumulation static charges or to modify the ability to dye, etc.

In fact, the stockings and tights thus obtained have both the advantages of foam tights, namely an elasticity and a compression of substantially the same level, and the advantages of veil tights: their arachnean and transparent appearance.

Their production and finishing do not require more precautions than those required for a traditional foam wire, with or without post-forming.

They are also of significant economic interest because they are less expensive than the stockings and tights based on stretch son only, while having their flattering appearance. In addition, they are available in conventional sizes for all customers.

Such knits are easy to dye in all colors, under the usual conditions for dyeing polyamide yarns, using acid or plastosoluble dyes.

The examples which follow are given as an indication but not limiting to illustrate the invention.

EXAMPLE 1

We realize a measurement knitting corresponding to a commercial size 2, at a speed of 1100 rpm, on a circular knitting machine for stockings and tights, 4 scraps, known in the trade under the brand MATEC type HS, comprising 400 needles .

We use the following threads:
- 1 polyamide 66 thread, of title 17 dtex / 3 strands, shiny, of round section, of texturing type stretch, of twist S and an identical thread of twist Z, having the following characteristics: - elongation at break% 30 - CN / tex toughness 41 - crease contraction E% 1.5 - torque effect 68 - secant module at 8% elongation 267.4
- 1 polyamide 66 yarn, title 17 dtex / 3 strands, shiny, of round section, texturing type FT or foam, twisted S and one twisted thread Z, having the following characteristics: - elongation at break% 33 - CN / tex toughness 47 - crease contraction E% 73 - torque effect 1 - secant module at 8% elongation 191.9
The measurements of crimp contraction E% and of contraction of crimped intermediate K% are carried out using a commercial device known under the brand Texturmat according to the method described in standard AFNOR G 07.305 (A). A flotilla of 2500 d / tex wire having previously undergone a heat treatment of 10 min in an oven at 130 ° C (in the standard 120 ° C), in order to develop crimping, is successively subjected to traction under different loads.

• L1 = correspond à la longueur de l'éprouvette sous une charge de 500 g (200 mg/dtex)
• L2 = correspond à la longueur de l'éprouvette sous une charge de 2,5 g (1 mg/dtex)
• L3 = correspond à la longueur de l'éprouvette sous une charge de 25 g (10 mg/dtex)

• .
  
• .
  

   L'allongement de rupture et la ténacité sont mesurés sur un appareil connu dans le commerce sous la marque Instron 1122. Chaque mesure est effectuée sur une éprouvette titrée au préalable on mesure la longueur initiale de l'éprouvette et la longueur à la rupture, la force de rupture. Pour bien caractériser un fil chaque valeur doit être une moyenne de 20 mesures, les calculs étant effectués au moyen d'un calculateur relié au dynamomètre.

• .
  

• Lr = longueur de rupture correspondant à la force de rupture
• L0 = longueur initiale

• .
  

   Le tricot est réalisé avec la disposition suivante :

• chute n° 1 : - fil stretch tors Z
• chute n° 2 : - fil mousse tors Z
• chute n° 3 : - fil stretch tors S
• chute n° 4 : - fil mousse tors S.

We measure successively the corresponding lengths:

• L1 = corresponds to the length of the test piece under a load of 500 g (200 mg / dtex)
• L2 = corresponds to the length of the test piece under a load of 2.5 g (1 mg / dtex)
• L3 = corresponds to the length of the test piece under a load of 25 g (10 mg / dtex)

• .
  
• .
  

The elongation at break and the toughness are measured on an apparatus known in the trade under the brand Instron 1122. Each measurement is carried out on a test piece previously titrated, the initial length of the test piece and the length at break are measured, the breaking force. To properly characterize a wire, each value must be an average of 20 measurements, the calculations being carried out using a computer connected to the dynamometer.

• .
  

• Lr = breaking length corresponding to the breaking force
• L0 = initial length

• .
  

The knitting is carried out with the following arrangement:

• chute n ° 1: - Z stretch twisted yarn
• chute n ° 2: - twisted foam wire Z
• chute n ° 3: - twisted stretch thread S
• chute n ° 4: - twisted foam thread S.

It is both transparent, elastic and has a good veil appearance. It is balanced, does not spin.

It is dyed black under the usual conditions for dyeing PA yarns using an acid dye at 98 ° C. It is free from scratches.

It has the following characteristics, broadly, compared to a pure stretch knit and a pure foam knit, obtained from the same threads as those used for the production of the knit according to the invention, of commercial size 2, also produced on a knitting machine circular 4 falls known in the trade under the brand MATEC type HS, speed 1100 rpm: Thigh Pure stretch Z / S / Z / S Pure Z / S / Z / S foam Stretch / foam Z / Z / S / S Elasticity E% 247 594 576 Reversal R% 57.6 72.4 69.6 Deformation D% 104 200 176 Force (CN) 260 750 460 Ankle Elasticity E% 114 295 233 Reversal R% 50 60 56 Deformation D% 39 76 60 Force (CN) 200 400 325

   Force CN = force correspondant à une déformation de l'article de 200 mm pour la cuisse et 100 mm pour la cheville.The characteristics of knits are measured on a stockings dynamometer by the following method:
Each end of the sample to be checked is hooked into the clamps of the dynamometer. We measure the length L0 of the sample without pretention. A load is gradually applied up to a predetermined value depending on the title of the wire and the number of stitches. The force / elongation curve is thus plotted and the length LM of the sample is determined under the predetermined load. We gradually remove the load and draw the return curve. The length LR is determined which is the length of the sample at the moment when the force is canceled (LR> L0). We are doing a second cycle. We determine L01, new length of the unpretentious sample (L01> L0, but L01 <LR because of a relaxation phenomenon). A second force / elongation curve is drawn which, for the predetermined load, restores the length LM. We gradually remove the load and draw the return curve. The LR1 is determined at the moment when the force is canceled, LR1 turns out to be practically equal to LR. We calculate elasticity, elastic recovery and deformation by the following formulas:

Force CN = force corresponding to a deformation of the article of 200 mm for the thigh and 100 mm for the ankle.

Figure 1 shows the stretch knit of the prior art obtained from stretch son of 17 dtex / 3 strands, according to the method described in Example 1 (magnification 32 X).

FIG. 2 shows the knitted fabric obtained according to the invention, seen under a microscope with a magnification of 32 X, corresponding to Example 1.

FIG. 3 shows a foam knitting of the prior art made from title foam strands of 17 dtex / 3 strand, according to the method described in Example 1, with the same magnification.

The photographs were taken on non-post-formed articles while the knits were stretched identically bidirectionally, so as to exactly reproduce the conditions of the wear.

In Figure 1 we observe the very characteristic stitches of stretch knitting, highlighting its transparency.

In Figure 3 we notice the blurred appearance and the opacity of the foam knit, in particular the loops, tendrils, and open parts due to the significant crimp characteristic of the foam son.

In FIG. 2, the knit according to the invention has a transparent appearance which is little different from stretch knit, more specifically the special arrangement of the 2 by 2 stitches is noted. held in stretch mesh and gives the whole knit its good elasticity.

On the leg, the general appearance of the article (Figure 2) has regular, well-structured stitches, as opposed to the more cloudy and fuzzy knit, as shown in Figure 3.

It is more akin to the appearance of stretch knitting (Figure 1).

COMPARATIVE EXAMPLE 1

• chute n° 1 : - fil stretch tors Z
• chute n° 2 : - fil stretch tors S
• chute n° 3 : - fil mousse tors Z
• chute n° 4 : - fil mousse tors S.

From the same threads as those used in Example 1, knitting is carried out on the same machine, according to the following arrangement:

• chute n ° 1: - Z stretch twisted yarn
• fall n ° 2: - twisted stretch thread S
• chute n ° 3: - twisted foam wire Z
• chute n ° 4: - twisted foam thread S.

The knitted fabric thus obtained on the finished article has very marked stripes making such an article non-marketable.

COMPARATIVE EXAMPLE 2

• chute n° 1 : - fil stretch tors Z
• chute n° 2 : - fil mousse tors S
• chute n° 3 : - fil stretch tors Z
• chute n° 4 : - fil mousse tors S.

From the same threads as those used in Example 1, knitting is carried out on the same machine, according to the following arrangement:

• chute n ° 1: - Z stretch twisted yarn
• chute n ° 2: - twisted foam wire S
• chute n ° 3: - Z stretch twisted yarn
• chute n ° 4: - twisted foam thread S.

The knitted fabric thus obtained is unbalanced by the Z twist. It tends to turn on the leg when worn; it is not marketable.

EXAMPLE 2

Knitting is carried out in the manner indicated according to Example 1 with the following threads:
- 1 polyamide 66 yarn, 13 dtex / 3 strands, shiny, round section, stretch type texturing, S twist and 1 Z twist thread, having the following characteristics: - elongation at break% 24.9 - CN / tex toughness 42.3 - crease contraction E% 2.63 - contraction of intermediate crimp 0.61 - torque effect 60.5 - secant module at 8% elongation 334.5
- 1 polyamide 66 yarn, 13 dtex / 3 strand, shiny, of round section, texturing type FT or foam, twisted S, and a twisted thread Z, having the following characteristics: - elongation at break% 29.7 - CN / tex toughness 42.5 - crease contraction E% 69.15 - contraction of intermediate crimp 57.3 - torque effect 1 - secant module at 8% elongation 224 The arrangement of the wires corresponds to that indicated in Example 1.

As in Example 1, the knitted fabric obtained is transparent, elastic and has a veil appearance. It is balanced and does not spin.

It undergoes a dye identical to that indicated in Example 1. It does not show any scratches.

It has the following broad characteristics: Thigh Pure stretch Z / S / Z / S Pure Z / S / Z / S foam Stretch / foam Z / Z / S / S Elasticity E% 257 733 576 Reversal R% 57.2 73.6 71.2 Deformation D% 109 247 189 Force (CN) 200 750 375 Ankle Elasticity E% 121 400 266 Reversal R% 48.7 60.7 62 Deformation D% 38 127 66 Force (CN) 175 500 330

Claims (11)

1. Knitted fabric elastic in the longitudinal and transverse directions and having a voile appearance, consisting of two different polyamide-based yarns, characterised in that one of the yarns is a bulked yarn and the other is a "stretch" yarn, these yarns having a Z-twist or an S-twist and being present according to the following arrangements below:

   i ) Z-twist stretch yarn, Z-twist bulked yarn/S-twist stretch yarn, S-twist bulked yarn.

   i i) Z-twist bulked yarn, Z-twist stretch yarn/S-twist bulked yarn, S-twist stretch yarn.

   i ii) S-twist stretch yarn, S-twist bulked yarn/Z-twist stretch yarn, Z-twist bulked yarn.

   i v) S-twist bulked yarn, S-twist stretch yarn/Z-twist bulked yarn, Z-twist-stretch yarn.

   and in that the yarns have a substantially identical linear density or have a different linear density leading, in the knitted fabric, to an identical covering capacity.
2. Elastic knitted fabric according to Claim 1, characterised in that the two yarns have a substantially identical linear density.
3. Elastic knitted fabric according to Claim 1, characterised in that the two yarns have a substantially identical covering capacity.
4. Knitted fabric according to Claim 1, characterised in that the overall linear density of each yarn forming the knitted fabric is between 8 and 22 dtex.
5. Knitted fabric according to Claim 1, characterised in that the polyamide used is polyamide 66.
6. Process for obtaining a knitted fabric according to Claim 1, characterised in that there are knitted, on a circular 4-feeder knitting machine, two different polyamide-based yarns having a cover factor substantially identical in the tensioned state, one being a traditional textured yarn or bulked yarn and the other being a torque yarn or stretch yarn, the bulked and stretch yarns being arranged alternately relative to one another unconventionally in the order of feeders 1 to 4: 2 Z-twist yarns, 2 S-twist yarns or 2 S-twist yarns, 2 Z-twist yarns.
7. Process according to Claim 6, characterised in that the two yarns are placed according to the following arrangement: 1 Z-twist stretch yarn, 1 Z-twist bulked yarn, 1 S-twist stretch yarn and 1 S-twist bulked yarn.
8. Process according to Claim 6, characterised in that the two yarns have a substantially identical linear density.
9. Process according to Claim 6, characterised in that the two yarns have a substantially identical covering capacity.
10. Process according to Claim 6, characterised in that the overall linear density of each yarn forming the knitted fabric is between 8 and 22 dtex.
11. Process according to Claim 6, characterised in that the polyamide used is polyamide 66.

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