Field of the invention

The present invention concerns core spun yarn. The yarn of the invention comprises a spun core wrapped by a second yarn sliver comprising natural dyed fibres, such that the core is e.g. covered with natural dyed fibres. The present invention also concerns a method for producing the core spun yarn and the use of the core spun yarn, such as in denim fabrics.

Background of the invention

A core spun yarn is a two-component structure with a core and a sheath. Generally, continuous filament yarn is used as core and staple fibres are used as sheath covering. The core spun yarn is typically used to enhance functional properties of the fabrics such as strength, durability and stretch comfort. Filament fibres are fibres of long continuous lengths, while staple fibres refer to those of shorter lengths. Natural fibres, such as cotton and wool, are staple fibres. The staple fibre is usually between 20 mm - 50 mm, as for example cotton. Synthetic fibres, such as nylon and polyester, are considered filament fibres.

Both natural dyes and synthetic dyes can be used in colouring of textile materials. Natural dyes are dyes or colourants derived from plants, invertebrates, or minerals. Most of the natural dyes are vegetable dyes from plant sources, roots, berries, bark, leaves, and wood and other biological sources such as fungi and lichens. Synthetic dyes are man-made. These dyes are made from petroleum, sometimes in combination with mineral-derived components.

Denim is a sturdy cotton warp-faced textile in which the weft passes under two or more warp threads. This twill weaving produces a diagonal ribbing that distinguishes it from cotton duck. The most common denim is indigo denim, in which the warp thread is dyed, while the weft thread is left white. As a result of the warp-faced twill weaving, one side of the textile is dominated by the blue warp threads and the other side is dominated by the white weft threads. This causes blue jeans to be white on the inside. Typically, the prior art yarn used in the weaving of denim fabric is dyed after the core spun yarn is prepared, e.g. by dipping the yarn in tanks of dyestuff. When the yarn is dipped in dye, it is typically stretched out throughout its length. In this process, the dyes do not draw completely into the core of the yarn. Thus, the core remains uncoloured while the outer part of the yarn is colored. Traditionally, there is a great deal of excess colour that sits on the surface of the yarn after dyeing which must be removed after the fabrics are made, so that they do not colour off so violently. Still, one would very often find that brand new denim garments colours off. The core spun yarn of the prior art, and the methods used for preparing such yarn, has a negative impact on the environment. For example, the use of chemical indigo dyeing has a significant and severe environmental impact due to high consumption of water, dyes, chemicals and energy. Traditional chemically dyed indigo denim yarn is yarn dyed in a process that requires very large amounts of water, dyes and chemicals during dyeing. When the yarn is ready, it is covered by large amounts of excess dyes, which must be removed through an after-treatment process. This after-treatment happens after the denim garments are sewn, typically with a very high water consumption. The working environment for the workers in the denim industry in general comes with a health hazard.

US2015176160 A1 discloses a core spun yarn with a core of filament fibres, such as polyester, and indicates that fabrics made of the yarn can be dyed after sewing.

W09426822 provides a process for preparing fibres for dying and fixing natural dyes to fibres.

The purpose of the present invention is to provide a product and a method to produce it, that addresses at least one of these problems while retaining the benefits of prior art.

Summary of the invention

In one aspect, the invention provides a core spun yarn where a spun core is covered with natural dyed fibres. In another aspect, the present invention provides a method for producing a core spun yarn characterized by dyeing fibres in natural dyes, and subjecting ultrasonic waves to the natural dyes including the fibres, and thereafter spinning the dyed fibres around a spun core. The invention further concerns use of the core spun yarn in manufacturing of fabrics, and provides a fabric comprising the core spun yarn of the invention.

Brief description of the drawings

The present invention will be described in greater detail in the following with reference to the embodiments shown in the drawings, in which:

Figure 1 shows a sketch of core spun yarn of the prior art.

Figure 2 shows a sketch of the core spun yarn according to the invention.

Figure 3 shows a sketch of the core spun yarn according to the invention, where the core comprises an inner elastic core.

Detailed description The invention provides a core spun yarn wherein a base yarn constitute a spun core wrapped by a second yarn sliver, and wherein the second yarn sliver comprises natural dyed fibres. The fibres of the second yarn sliver is preferably twisted around the central spun core. The invention provides a core spun coloured yarn, wherein the manufacturing of the yarn has a low environmental impact. Generally in the core spun yarn of the prior art, continuous filament yarn of polyester is used as the core and staple fibres are used as sheath covering. In one embodiment, the spun core (2) of the present invention is however based on staple fibres (for example cotton) and preferably not on filament fibres as traditionally used. In one embodiment, the core (2) is a spun yarn comprising natural or regenerated fibres. The natural fibres of the core may be selected from one or more of the group of cotton, hemp, jute, silk and wool and regenerated fibres such as cellulosic regenerated fibres such as lyocell, rayon, viscose and modal.

In one embodiment, the spun core further includes an inner elastic core to provide elasticity to the yarn. The elastic inner core is made of e.g. polyester, elastane and/or polyurethane. In one embodiment, the spun core of the core spun yarn is mainly made of natural or regenerated fibres, such as of at least 50% by weight of such fibres, preferably more than 70% by weight of such fibres. The inner elastic core is preferably a minor part. The spun core of the yarn has a light colour.

Preferably, the yarn of the spun core is undyed, or alternatively is dyed in a light colour. Preferably, the spun core has a colour that differs from the colour of the second yarn wrapped around the core.

The second yarn of the core spun yarn of the invention comprises natural dyed fibres. Hence, the spun core is preferably covered with fibres that have been coloured with natural dyes, wherein the natural dyed fibres are wrapped around the spun core. The fibres of the second yarn, i.e. the fibres wrapped around the spun core, are preferably natural or regenerated fibres, such as selected from the group of cotton, hemp, jute, silk and wool and regenerated fibres such as cellulosic regenerated fibres such as lyocell, rayon, viscose and modal, and are preferably cotton fibres.

The covering fibres (3) have a colour obtained from natural dyestuff. The natural dyes used are preferably dyes derived from plants, but may also be naturally existing dyes from plant sources, roots, berries, bark, leaves, and wood and other biological sources such as fungi and lichens. The colour of the wrapping fibres (3) spun around the spun core (2) is in a preferred embodiment natural indigo. According to the invention, also other natural dyes can be used to obtain a core spun yarn of other colours, such as by using the same preparation and dyeing technique to create denim products in different colours. Preferably, the resulting colour of the wrapping fibres is dark, in contrast to the colour of the spun core, and is more preferably indigo, blue or black, and most preferably indigo. Unlike core spun yarn of the prior art, the wrapping fibres (3) are dyed before spinning these dyed fibres around the spun core. The colour of the core is preferably undyed and therefore differs from the colour of the fibres 3 spun around the core 2. Hence, in the obtained core spun yarn of the invention there is a clear distinction between the colour of the core and the colour of the wrapping fibres. The core spun yarn according to the invention is for use e.g. as a yarn in denim fabrics, such as in the warp yarn for such. The core is provided in a high colour contrast to the covering fibre in order to allow for a worn denim appearance as the outer dyed fibre is worn and reveals the contrasting lighter coloured core underneath.

The covering fibres of the core spun yarn of the invention are in one embodiment dyed in an ultrasonic dyeing process where only natural dyes are used in the dyeing process. By utilizing ultrasonic technology, it is possible to dye the textile fibres, such as with natural indigo, in large volumes, with a high quality and with a low environmental impact, and at a commercially acceptable price. Dye-tanks are filled with fibres and natural dyestuff and exposed to ultrasound waves providing a high colour fastness. By utilizing innovative yarn spinning technology, it is according to the invention created high quality environmentally friendly denim yarns for a new generation of sustainable and responsibly made denim products. The use of ultrasound in the dyeing of yarns and textiles is energy saving, reduces processing times, maintains or improves product quality and reduces the use of auxiliary chemicals. In one aspect, the invention provides a method (process) for producing a core spun yarn comprising the steps of

i) dyeing fibres with natural dyes, and

ii) subjecting ultrasonic waves to the natural dyes including the fibres (3), and thereafter iii) spinning the dyed fibres (3) around a spun core (2).

In step ii) the fibres and the natural dyestuff, such as indigo, are mixed together, such as in a tank, and are then exposed to ultrasonic waves.

The embodiments and features described in the context of the first aspect directed to the core spun yarn, also apply to this aspect directed to the method. In one embodiment, the invention provides the method disclosed for preparing the core spun yarn of the first aspect.

In a preferred embodiment, in step iii) the spun core that is used is undyed. Hence, the fibres that have been coloured with natural dyes are spun around a core thread that is undyed. A further aspect is a core spun yarn obtainable by the disclosed method. Chemically dyed indigo denim yarn of the state of art is yarn typically dyed in a process that requires very large amounts of water, dyes and chemicals during dyeing. The natural dyed core spun yarn according to the present invention, goes through a dyeing process that generates a low amount, such as is completely without, waste water, with the use of no or a low amount of chemicals and a low energy consumption. After the yarn is spun, there are no excess dye-stuffs in the yarn, which means the denim garments do not need after-treatment. This gives a further significant reduction in water consumption.

When using the core spun yarn of the invention in manufacturing denim fabrics the characteristic look of worn denim is achieved. The look of worn denim with white areas is achieved because of the light colour of the core, and the clear distinction in colour between the core and sheath fibres. This appearance of the yarn is essential for the yarn to be used for denim fabric manufacture.

In a further aspect, the invention provides a woven fabric comprising the core spun yarn of the first aspect. More preferably, the invention provides a woven fabric comprising a warp and a weft, wherein at least one of the warp and the weft consist of a core spun yarn according to the first aspect. The embodiments and features described in the context of the first aspect directed to the core spun yarn, also apply to this aspect directed to the fabric comprising the core spun yarn. The core of the spun yarn is preferably made from natural or regenerated fibres, such as cotton, hemp, jute, silk or wool, or regenerated fibres as cellulosic regenerated fibres such as lyocell, rayon, viscose or modal, or mixtures of these. This yarn can also be a core yarn with an elastic inner core (4) covered by natural or regenerated fibres to achieve an elastic yarn that can be used for manufacture of elastic denim fabrics. The second yarn of the core spun yarn product comprises natural dyed fibres. Hence, the spun core is covered with natural dyed fibres, wherein the natural dyed fibres are wrapped around the spun core.

In a preferred embodiment, the woven fabric comprises a core spun yarn, comprising a spun core comprising stable fibres, wherein the core spun yarn is covered with natural dyed fibres, and wherein the colour of the dyed fibres is natural indigo. More preferably, the woven fabric is a denim fabric. The yarn and the fabric of the invention are environmentally friendly products, achieved by a production and colouring method which is very environmentally friendly. Further, environmentally friendly raw material and also the manufacturing process is much more careful to the environment than the traditional way of manufacturing denim fabrics. The covering fibres (3) are dyed with natural dyes before spinning the dyed fibres (3) around a spun core (2). In the manufacturing process of the core spun yarn according to the invention, no excess water is used in the dyeing and only natural dyes are used.

Figure 1 shows a core spun yarn of the prior art, wherein the left hand figure is with no elastics and the right hand figure is with elastics. Figure 2 shows a core spun yarn 1 of the present invention where the spun core 2 is covered with natural dyed fibres 3.The yarn of Figure 2 has no elastics.

Figure 3 shows a further yarn according to the invention where it comprises a core 2 including, such as embracing, an inner elastic core 4. Flence, the yarn of Figure 3 is with elastics. To achieve an elastic fabric the yarn in this embodiment has a spun core 2 with an inner elastic core 4.

The core spun yarn of the invention can be made with different coarseness and fineness, and which preferably is suitable for use in weaving of denim fabrics. Preferably, the yarn count of the final yarn according to the invention is in the range from Ne 7 to 30, wherein Ne is defined as the number of 840 yards strands per 1 English pound of mass.

While the invention has been described with reference to specific examples and embodiments, the scope of the invention is determined by the accompanying claims.