WO2010071910A2

WO2010071910A2 - Yarns and threads from blends of fibres and articles therefrom

Info

Publication number: WO2010071910A2
Application number: PCT/AT2009/000490
Authority: WO
Inventors: Johann Leitner; Bob Jeavons; Karin KÄMPF
Original assignee: Lenzing Ag
Priority date: 2008-12-23
Filing date: 2009-12-17
Publication date: 2010-07-01
Also published as: WO2010071910A3; AT507758A1; EP2382344A2; CN102272365A

Abstract

The invention relates to blends of fibres in the form of yarns and threads from cotton with cellulosic staple-fibres of the Lyocell type as well as articles therefrom.

Description

Yarns and Threads from Blends of Fibres and Articles therefrom

It is known to blend fibres of different types to provide articles therefrom with certain properties.

It is known from Lenzinger Berichte, vol. 42, March 1887, page 46, that a blend of cotton with fibres of the viscose type or modal type can improve the yarn quality. But it was found that the tenacity and elongation of the yarns is only slightly depending on the viscose content (Lenzinger Berichte, vol. 62, March 1967, page 46, last paragraph, page 47 - fig. 2).

Cellulosic fibres of the viscose type and modal type are produced according to the viscose process. In recent years the "amine-oxide-process" or "Lyocell process" has been established as alternative to the viscose process, wherein cellulose, without forming a derivative, is dissolved in an organic solvent of an amine-oxide, in particular N-methylmorpholine-N-oxide (NMMO).

In said process, the solution of cellulose is usually extruded by means of a forming tool, whereby it is moulded. Via an air gap, the moulded solution gets into a precipitation bath, where the moulded body is obtained by precipitating the solution. The moulded body is washed and dried, optionally after further treatment steps.

Cellulosic fibres produced from such solutions are called "solvent-spun" fibres and have received the generic name "Lyocell" by the BISFA (The International Bureau for the Standardisation of man made Fibres). A process for the production of Lyocell fibres is described, for instance, in US 4,246,221. The amine-oxide process yields fibres which are distinguished by a high tensile strength, a high wet-modulus and a high loop strength. Other possible solvents for the production of solvent-spun cellulosic fibres are so-called "ionic liquids". These solvents are described e. g. in WO 03/029329 and WO 06/108861. For the purpose of this patent application the expressions "solvent-spun cellulosic fibre" and "Lyocell" are used synonymously.

These solvent-spun cellulosic fibres not only have higher dry and wet tenacities compared to other cellulosic fibres but they also exhibit a certain property called fibrillation. The fibrillation tendency of a single fibre can be measured e.g. by the NSF method (wet abrasion value), described in WO 99/19555. For a variety of applications this fibrillation is advantageous. For other applications the fibrillation is undesirable.

In the meantime different treatments of the Lyocell fibres were developed to decrease their tendency to fibrillate, resulting in a high NSF value. Most of these treatments include a chemical cross linking step in the never-dried state using different cross linking substances.

Lyocell fibres are mainly used in the form of cut fibres of a discrete length, i.e. as so-called "staple fibres". If in the following "Lyocell fibres" are mentioned, Lyocell fibres in the form of staple fibres are meant by that.

Yarns and threads from blends of cotton and Lyocell fibres with a Lyocell fibre content above 50 % are already available commercially. The Lyocell fibre is determining the properties like tenacity and elongation of the blend due to its high content.

Cotton as a naturally product is available in qualities and with qualities which differ very much and the price depends on the quality. Yarns made of 100 % cotton show a high variation in the yarn parameters.

It is also known from AATCC Review, issue May 2002, pages 25 to 29, that the blending of Lyocell fibres together with naturally coloured cotton fibres could enhance the yarn strength significantly. It was found that the use of 20 % Lyocell enhanced yarn strength in rotor yarns nearly 40 % and 60 % Lyocell increased yarn tenacity over 75 %. Blending of naturally coloured cotton with Lyocell in needlepunch nonwovens resulted in more than doubled nonwoven strength, as measured in the ball burst test.

But this document clearly showed that the improvements were only made by using cotton types like naturally coloured cotton which originally show poor mechanical properties. The same document showed that in blends with a high-quality white cotton the improvements by blending with Lyocell are diminishing.

It is the object of the invention to provide blends of fibres from cotton and cellulosic staple fibres of the Lyocell type in the form of yarns and threads with improved yarn properties as well as improved tenacity and elongation in regard to 100 % cotton yarns or cotton threads respectively. It is also a certain object of the invention to find an economic way to compensate poor fibre properties of certain cotton types like naturally coloured cotton, organic cotton or recycling cotton.

Said objects are achieved in that the content of the Lyocell fibres in the blends of cotton and Lyocell fibres is less then 50 % (by weight) based on the total blend.

Preferably the content of the Lyocell fibres in the yarns and threads according to the invention is 25 to 33 % by weight.

The titer of the Lyocell fibres preferably is 0,9 to 2,5 dtex, particularly preferably 1 ,3 to 1 ,7 dtex.

The cutting length of the Lyocell fibres is 28 to 51 mm, preferably 34 to 38 mm.

The yarns and threads according to the invention can be produced according to any known manufacturing method. An overview can be found in "Alfons Hofer, Stoffe 1. 1st ed., Deutscher Fachverlag GmbH, Frankfurt am Main, 1992)."

In one preferred embodiment of the invention the solvent spun cellulosic fibres are Lyocell fibres with a high NSF value. Especially preferred are Lyocell fibres with an NSF value of more than 200.

For most applications the solvent spun cellulosic fibres with high NSF value are cross-linked with an alkali-resistant cross-linking agent, because the fibre blend according to the invention is preferably mixed with other cellulosic fibres and such fibres are commonly exposed to alkaline baths during dyeing and finishing. Therefore alkali-resistant cross-linking is preferred, but the acid- resistant cross-linked solvent spun cellulosic fibers in principal show the same advantages with respect to pilling performance and may be used especially for applications which require acidic steps during the aftertreatment.

Especially suitable is an alkali-resistant cross-linking agent of the following formula (I):

X

1 1 X^ΛNΛ0(R),

(I) wherein X represents Halogen, R=H or an ionic residue and n=0 or 1 , or a salt of this compound. In principle this treatment is already known from WO 99/19555.

Even more surprisingly it was found that the dyeability of the solvent spun cellulosic fiber with an NSF value of more than 200 was compatible with that of cotton, which resulted in even dyeing results and increased dye-house economy. Also suitable, especially for the case when mixtures with synthetic fibres, i. e. polyester are intended, is an acid-resistant cross-linking treatment which is already known from WO 94/09191. One preferred cross-linking agent in this embodiment of the invention is 1 ,3,5-triacryloylhexahydro-s-triazine (THAT)

In one preferred embodiment of the invention the solvent spun cellulosic fibres are cross-linked in the never dried state. Solvent-spun fibres in their state before the first drying are designated as "never dried" fibres. It has been shown that the use of compounds of the formula (I) on never dried fibres in particular produces a considerable reduction in the tendency to fibrillate.

In a preferred embodiment the cotton fibres are recycling cotton fibres, i. e. cotton fibres which were already processed once into textiles and then recycled by well-known methods. Such recycled cotton fibres have poor fibre properties because of the many mechanical as well as chemical influences they had experienced in their first "textile life" and during the recycling process. Therefore the fibre length could have been decreased by e.g. cutting, abrasion, breakage or even by the decomposing effect of chemicals (acids, bleaching agents, laundry chemicals, dyestuffs, oxygen, sunlight, etc.). By blending with lyocell according to the invention such disadvantages can be balanced, resulting in very economic fibre blends showing good mechanical properties.

A further embodiment of the present invention is a product containing the yarns and threads according to the invention, preferably a textile article in the form of woven fabrics or knitted fabrics.

Particularly preferred are textile articles essentially consisting of the yarns or threads according to the invention.

The use of the yarns and threads according to the invention and the products made therefrom is a further embodiment of the invention. A further embodiment of the present invention is a method to compensate the poor fibre properties of cotton fibres, wherein the cotton fibres with poor fibre properties are blended with less than 50 % by weight of Lyocell fibres, followed by making yarns or threads from this blend, the content of Lyocell fibres in the yarns or threads being less than 50 % by weight.

In the following the present invention will be described in more detail by way of examples. Nevertheless the invention is explicitly not limited in any way to the scope of these examples:

Examples 1 to 6:

Yarns were made by Ring-spinning from blends of different cotton-types and Lyocell fibres as described in Table 1. The improvements in the yarn-qualities as well as improvements in tenacity and elongation of the yarns given in % compared to a yarn (Ne 80/2) containing 100 % of the corresponding cotton type are shown in Table 1 :

Table 1

The results show that yarns and threads made of blends of cotton and Lyocell fibres with a content of less than 50 % Lyocell fibres show improvements in yarn properties as well as improvements in tenacity and elongation.

Claims

Claims:

I . Yarns or threads from a blend of cotton with Lyocell fibres, characterized in that the content of Lyocell fibres in the blend is less than 50 % by weight.

2. Yarns or threads according to claim 1 , characterized in that the content of the Lyocell fibres in the yarns and threads is 25 to 33 % by weight.

3. Yarns or threads according to claim 1 or 2, characterized in that the titer of the Lyocell fibres preferably is 0,9 to 2,5 dtex, particularly preferably to 1 ,3 to 1 ,7 dtex.

4. Yarns or threads according to one or several claims of claim 1 to 3, characterized in that the cutting length of the Lyocell fibres is 28 to 51 mm, preferably 34 to 38 mm.

5. Yarns or threads according to one of the preceeding claims, characterized in that the Lyocell fibres are Lyocell fibres with an

NSF value of more than 200.

6. Yarns or threads according to one of the preceeding claims, characterized in that the cotton fibres are recycling cotton fibres.

7. Textile article containing a yarn and/or a thread according to one or several claims of claim 1 to 6.

8. Textile article according to claim 6, characterized in that it consists essentially of a yarn or a thread according to one or several claims of clam 1 to 6.

9. Use of a textile article according to claim 7 to 8 in textiles.

10. Use of a yarn or thread according to claim 1 to 6 in textiles.

I 1. Method to compensate the poor fibre properties of cotton fibres, wherein the cotton fibres with poor fibre properties are blended with less than 50 % by weight of Lyocell fibres, followed by making yarns or threads from this blend, the content of Lyocell fibres in the yarns or threads being less than 50 % by weight.