EP3080350A1

EP3080350A1 - A process of making a yarn having weavability features and a process of weaving such yarn

Info

Publication number: EP3080350A1
Application number: EP14830647.5A
Authority: EP
Inventors: Elisabetta CANEPA
Original assignee: Canepa SpA
Current assignee: Canepa SpA
Priority date: 2013-12-13
Filing date: 2014-12-12
Publication date: 2016-10-19
Also published as: WO2015087306A1; ITMI20132090A1

Abstract

A process of making a yarn having weavibility features, comprising the steps of providing a fine yarn which comprises an intimate blend of first fibers and polyvinyl alcohol fibers. Advantageously, before spinning, said fine fiber yarn undergoes a sizing step, to obtain a sized fine yarn having an increased tensile strength as compared with the tensile strength of the original fine yarn. The first fibres are selected from natural animal fibers, vegetable fibers, non-water- soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin.

Description

"A process of making a yarn having weavability features and a process of weaving such yarn"

DESCRIPTION

The present invention relates to a process of making a yarn having weavability features, namely a fine yarn made of natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at a pure state or blended together .

In another aspect, the present invention also relates to a process of weaving said yarn for making a fabric.

As used herein, the term weaving is generally used both for designating warp-and-weft weaving and knit-weaving .

As used herein, for example:

- the term fine yarns is intended to designate yarns having a yarn count, as measured in Nm, of the order of 70 or more, the yarn increasing its fineness as its Nm number increases;

- animal fibers are intended to cover fleece or hair fibers (such as wool, alpaca, vicuna, cashmere and others) ; continuous filaments of animal origin are intended to cover filaments obtained by reeling from whole cocoons (such as silk) ;

- discontinuous filaments of animal origin are intended to cover filaments obtained by unravelling from defective cocoons (such as waste silk);

- vegetable fibers are intended to cover all the fibers obtained from plants, shrubs, inflorescences, roots, leaves (such as cotton, flax, hemp, jute, coir, ramie, bamboo, and others);

- non-water-soluble synthetic polymer fibers are intended to cover, for example, polyamide, polyester, acrylic, polypropylene fibers, and others that are not soluble in aqueous solutions;

- man-made natural fibers are intended to cover, for example, rayon viscose, modal, acetate, cupro, lyocell, and others.

These yarns of the above mentioned type are known to be difficult to spin and weave, due to their fineness which makes them prone to breaking during spinning or later weaving.

Furthermore, at present the following needs are strongly felt in the field of yarns and weaving:

enhancing mechanical properties, such as abrasion resistance, of a thin yarn, and reducing mechanical friction between weft yarns and warp yarns, for trouble-free weaving;

developing an environment-friendly and low- power-consumption process of making a yarn having improved weavability features;

- developing a process of making a yarn having improved features in terms of high resistance to pilling, felting and rubbing, as well as superior mechanical properties while maintaining the desired softness, volume, brightness and lightness features;

- developing a process of making a yarn having improved dye affinity, or improved affinity for the later finishing steps, such as printing.

In view of improving weavability of yarns, in other words imparting the required tensile strength thereto for them to be woven on a loom, yarns have been known for more than ten years to be made from an intimate blend of valuable fibers and water-soluble synthetic fibers, such as polyvinyl alcohol (PVA) fibers, the resulting yarns having an increased tensile strength due to the presence of the water- soluble synthetic fibers. Nevertheless, it shall be noted that weaving very fine yarns, such as yarns having a yarn count of 70 Nm or more, for instance having a yarn count of the order of 95 Nm, weavability is still very problematic.

Prior art document EP 2050845 teaches the provision of a later step in which yarns comprising an intimate blend of valuable fibers and water- soluble synthetic fibers are further doubled and twisted with yarns made of water-soluble fibers, namely PVA fibers.

Nevertheless, referring to EP 2050845, it shall be noted that, although the process taught therein provides a final doubled and twisted yarn, whose tensile and torsion strength is more than adequate for loom weaving, it still suffers from drawbacks, including :

- the use of a very large amount of PVA for each kilogram of valuable fibers employed, and in this respect the detrimental effects resulting from the use of PVA should be noted, not only in terms of an increase of manufacturing costs, but also and especially in terms of the difficulty of removing PVA from the final fabric and the disposal of the bath that contains the PVA removed from the fibers;

- twisting to at least 200 turns per linear meter, which is performed after the above mentioned doubling step changes the number of final twisting turns that will be found in the resulting fabric, as the twisting performed during doubling is algebraically added to or subtracted from the yarn, depending on whether such twisting occurs in the same direction (Z-Z or S-S) or in an opposite direction (Z-S or S-Z) . In this respect, it shall be noted that, in a yarn made of fine fibers, any increase or decrease of twist of the order of 200 turns per linear meter leads to the formation of very different fabrics, whose difference also appears from a visual examination of such fabrics;

doubling of PVA yarns and later removal thereof from the weave of the fabric so obtained by dissolution in a liquid bath, are only applicable to fabrics having a small number of yarns per centimeter, because, once PVA yarns are dissolved in the liquid from the fabric weave, they leave voids between the remaining yarns, made of the valuable fibers only.

The present invention is based on the problem of conceiving and providing a process of making a fine yarn, made of natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at a pure state or blended together, having improved weavability features, that fulfills the above needs, while avoiding the above mentioned prior art drawbacks.

This problem is solved by a process as defined in claim 1, for improving the weavability features of a fine yarn made of natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at a pure state or blended together .

In another aspect, the invention also relates to a process of weaving said yarn for making a fabric, as defined in claim 14.

The process of making a yarn having weavability features, according to the invention comprises the steps of:

providing first fibers comprising natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at pure state or blended together;

- providing water-soluble synthetic fibers;

- spinning a fine yarn composed of an intimate blend of said first fibers and said water-soluble synthetic fibers.

Advantageously, the process is characterized in that it comprises a step of sizing said fine yarn using a sizing solution, to obtain a sized fine yarn having an increased tensile strength as compared with the tensile strength of the original fine yarn.

Preferably, the fine yarn count is of the order of 70 Nm or more.

More preferably, the fine yarn count is of the order of 90 Nm or more.

Preferably, said first fibers are substantially made of pure cashmere or chashmere and silk.

Preferably, the above mentioned water-soluble synthetic fibers essentially consist of polyvinyl alcohol (PVA) fibers.

Preferably, the above mentioned step of sizing said fine yarn is carried out using a sizing solution comprising a composition of chitosan and/or derivatives thereof.

Preferably, during sizing, the temperature of the sizing solution is maintained at a temperature of more than 60° and less than the boiling point, e.g. a temperature that ranges from 60°C to 90°C, more preferably a temperature of the order of 70°C. By way of example, the sizing composition in use may comprise natural substances and derivatives thereof, such as :

- starch and starch derivatives (natural starch and chemically modified starch-based products);

- cellulose derivatives ( carboxymethyl cellulose (CMC) ;

protein-based products (glue, gelatin, albumin) .

Otherwise, a synthetic sizing solution may be used, comprising one or more of the following components :

- polyacrylates ;

- modified polyesters;

- polyvinyl alcohol (PVA);

- styrene / maleic acid copolymers .

Additives such as surfactants, solvents, antifoaming agents, etc., may be also added to the sizing formulation, according to the particular requirements to be met for each fine yarn type.

The sizing solution is prepared by hot mixing its components, for optimized component mixing results. Generally, the temperature at which the sizing solution is prepared/mixed is more than 60° and is maintained below the boiling point of the solution, to prevent degradation of one or more components of the sizing solution due to boiling. Preferably, the temperatures at which the components of the sizing solution are mixed range from 60°C to 92 °C, and preferably such temperatures are 70°C or more and less than 90°C.

It shall be noted that the sizing solution may also comprise both synthetic and natural substances and derivatives thereof.

By way of example, a sizing solution comprising

Polyvinyl alcohol (PVA) is as follows:

- 200 liters water;

- 25 kg low viscosity polyvinyl alcohol;

- 25 kg acrylic resin;

- 12.5 kg CMS carboxymethyl starch;

- 1 kg fat composed of fatty acids and

- 8 liters softener

It shall be noted that the presence of polyvinyl alcohol greatly increases the tensile strength of yarns, without causing the problems arising when doubling the fine yarn with a PVA yarn and dissolving the PVA yarn from the weave of the finished fabric.

In accordance with the above described preferred embodiment, the sizing solution in use may advantageously comprise chitosan and/or derivatives thereof .

Chitosan is a natural polymer derived from chitin, which is a protein contained in the exoskeleton of crustaceans, and is a nature-renewable material, since it is obtained from food industry by^¬ products .

A reinforcement product based on chitosan and/or derivatives thereof, used as a sizing agent for the fibers and/or filaments, has better sizing properties than many other natural substances. For instance, the addition of 5 to 15% carboxymethyl chitosan concentrations in the sizing step has provided increases in toughness of cotton fabrics by up to 55%.

Preferably, the above described sizing solution containing chitosan comprises:

chitosan and/or derivatives thereof, preferably low molecular weight chitosan, more preferably chitosan having a molecular weight of 150,000 Da, degree of deacetylation 75-85%; viscosity 20-200 cps at ambient temperature and at a concentration range of 0.5-10% w/v, preferably 0.8-3% w/v, more preferably 1% w/v;

- an acid aqueous solution and

- a radical photoinitiator . The above mentioned acid aqueous solution preferably comprises acetic acid at a concentration of 1.5-3.8% v/v, preferably at a concentration of 1.8-2.22% v/v, more preferably at a concentration of 2% v/v.

If the above mentioned step of applying a reinforcement product comprising a composition of chitosan and/or derivatives thereof to the yarn fibers is carried out by dipping the latter into a bath of said composition, there will be preferably a bath ratio ranging from 1-7 to 1-35, more preferably a bath ratio ranging from 1-10 to 1-30, most preferably a bath ratio ranging from 1-16 to 1-24.

According to a preferred and advantageous embodiment of the inventive process, such process includes a step of crosslinking at least part of the chitosan and/or derivatives thereof of the sizing solution applied to the fibers of said fine yarn upon sizing, to obtain a crosslinked reinforcement polymer, permanently anchored to the fibers of the fine yarn.

Such crosslinking of at least part of the chitosan and/or derivatives thereofof the sizing solution applied to the fibers of said fine yarn is performed by overcoming a technical prejudice existing in the field of yarns and weaving: i.e. that the chitosan polymer may only be used to impart a temporary effect to the fibers and/or filaments of the yarns, which is designed to disappear after a first washing step or in other finishing steps.

Conversely, crosslinking of chitosan and/or derivatives thereof on the fibers of the fine yarn ensures permanent adhesion of the chitosan-derived polymer and its components, such that the beneficial effects of chitosan may be maintained with time.

Crosslinking of chitosan and/or derivatives thereof allows the fibers of the fine yarn to be imparted a considerable physical-mechanical resistance, a long-lasting sanitization effect, resisting many repeated washes with hot and/or soapy water, as well as a considerable improvement in the finish affinity, e.g. the dye affinity, of the fibers of the fine yarn.

The technique of crosslinking chitosan and/or its derivatives applied to the fibers of the fine yarn is used before weaving the fine yarn, against the prejudice existing in the field of yarns and weaving, particularly for valuable yarns/fabrics such as cashmere or silk, that crosslinking of chitosan would lead to an undesired excessive structural stiffening of the yarns, which would make them no longer suitable for making soft, valuable fabrics.

Conversely, according to a further auxiliary aspect of the present invention, the fibers and filaments of the treated yarns are coated with a thin layer of reinforcement product, which may be at least partially crosslinked and, if needed, partially removed in a partial and calibrated manner. Otherwise, the portion of the crosslinked chitosan and/or derivatives thereof that remains on the fibers of the fine yarn , maintains its beneficial effects, as mentioned above, due to the presence of chitosan.

Preferably, the step of crosslinking at least part of the chitosan and/or derivatives thereof of the sizing solution applied to the fibers of the fine yarn, is preceded by a step of drying the fibers of the fine yarn and the sizing solution applied thereto, to assist crosslinking of chitosan ' and/or derivatives thereof.

Preferably, such crosslinking of the chitosan and/or derivatives thereof of the sizing solution applied to the fibers of the fine yarn, is carried out by a step of ultraviolet exposure of the chitosan and/or derivatives thereof of the sizing solution applied to the fibers of the fine yarn. Preferably, the above-mentioned step of partial and calibrated removal of the crosslinked reinforcement polymer from the fibers of the fine yarn is carried out such that the amount left on the fibers of the fine yarn of said crosslinked reinforcement polymer derived from chitosan and/or chitosan derivatives is 0.1-9 % w/w based on the dry weight of the. fibers.

Preferably, the above mentioned step of partial and calibrated removal of the crosslinked reinforcement polymer from the fibers of the fine yarn is carried out using a hydrolyzing desizing solution, e.g. by immersion in such hydrolyzing desizing solution. This desizing step:

- provides enzymatic desizing, preferably using protease, amylase and/or cellulase enzymes or

- provides chemical desizing, using hydrolyzing acids, preferably hydrochloric and/or sulfhydric acid diluted to a concentration of 3-10% v/v, more preferably 5-7% v/v.

The following three composition examples may be considered as possible examples of sizing solutions comprising chitosan:

EXAMPLE 1 of a sizing solution containing chitosan

- cold water litersl92 - chitosan Kg 10

- acetic acid L 10

- starch Kg 17

- fat Kg 0.8

- softener liters6.7

EXAMPLE 2 of a sizing solution containing chitosan

- cold water liters 192

- chitosan Kg 11.5

- acetic acid Kg 11.5

- starch Kg 15

- fat Kg 0.8

- softener liters 6.7

EXAMPLE 3 of a sizing solution containing chitosan

- cold water liters 155

- chitosan Kg 3

- citric acid Kg 8

- catalyst

Kg 6

(NaH2P04)

where it shall be noted that sizing compositions like those of Examples 1 and 2 are particularly suitable for cashmere fibers, wools and the like, whereas the composition of Example 3 is more suitable for fibers such as cotton and the like.

Obviously, the sizing solution may be selected according to the particular fibers of the fine yarn to be sized.

In this respect, it shall be noted that a sizing solution comprising both chitosan and polyvinyl alcohol (PVA) may be used.

As possible examples of fine yarns in intimate blends to be sized, the following yarns may be considered, by way of example only:

- single-ply yarn with a yarn count of 70 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers;

- single-ply yarn with a yarn count of 80 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers;

- single-ply yarn with a yarn count of 90 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers;

- single-ply yarn with a yarn count of 95 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers;

- single-ply yarn with a yarn count of 100 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers;

- single-ply yarn with a yarn count of 110 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers; - single-ply yarn with a yarn count of 120 Nm comprising an intimate blend of 50% of said first fibers and water-soluble synthetic fibers.

It shall be noted that the amount of first fibers may be other than the above mentioned 50%, and may range from 30% to 80% based on the total fibers of the fine yarn, preferably from 35% to 70% based on the total fibers of the fine yarn.

Furthermore, even when using the above mentioned amounts of first fibers and water-soluble fibers, two- three- or more-ply yarns may be provided, such as: a 2/90 Nm fine yarn (i.e. a two-ply fine yarn with a yarn count of 90 Nm 90) or a 3/90 Nm fine yarn (i.e. a three-ply fine yarn with a yarn count of 90 Nm) .

From the above described sized fine yarns, which comprise first fibers comprising natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at a pure state or blended together, spun in intimate blend with second water-soluble synthetic fibers, the process of making a fabric of fine yarns comprises the following steps: - a weaving step, in which the above described sized fine yarns are woven and

- a later dissolution step, in which the water- soluble synthetic fibers contained in the yarns of said plurality of sized fine yarns of the fabric are dissolved in an aqueous solution,

which provide a fabric only composed of the first fibers of said fine yarns that have undergone the weaving step.

In the above-mentioned weaving step, the intimately blended and sized fine yarns may also be of different types. Thus, there may be different fine yarns for wefts and warps, but also different fine yarns for wefts and/or different fine yarns for warps, according to the particular type of fabric to be obtained.

The above mentioned process of making a fabric preferably comprises a step of desizing the fibers of said fabric for removing the sizing solution applied to the fibers of the sized fine yarns.

This desizing step may be carried out before, after or during the possible partial and calibrated removal of part of the crosslinked chitosan applied to the fibers of the fine yarns after possible crosslinking, provided that part of it is required to be removed.

The dissolution of the polyvinyl alcohol (PVA) provided in intimate blend in the fine yarns of the fabric may be conveniently obtained by immersing the fabric in a slightly acidic water-soluble solution (with indicative pH values ranging from 4 to about 6) at a suitable temperature, indicatively 30°C or more.

Preferably, the temperature of the bath shall range from 50°C to 70° centigrade, considering that:

- at too low temperatures (e.g. 15-20°C) complete dissolution of PVA fibers is hardly or impossibly achievable, whereas

- at temperatures of 85-90°C or more, the above- mentioned first fibers of the fabric (such as cashmere or wool fibers) may be degraded.

In the light of the above disclosure, the process of the invention as described above, and the yarn that can be obtained with such process, can fulfill the needs addressed herein.

By carrying out the sizing step on the intimately blended fine yarn, such yarn may be woven without being exposed to breakage, and the intimately blended fine yarn does not need to be doubled with another PVA yarn, which would be highly undesirable, as mentioned above. Also, it shall be noted that, in the fabrics obtained with the above described process of the invention, the presence of chitosan on the fibers imparts dimensional stability and pilling resistance to the fabric fibers, such that no anti-pilling or dimensional change-preventing processes are required to be carried out on the fibers of the resulting fabrics, which will avoid the need for treatment and/or finishing processes that involve cost increases and use harmful substances, requiring disposal of the processing residues as special waste.

The above disclosure is susceptible to a number of changes and variants within the inventive concept, as outlined by the annexed claims.

~k k -k -k -k -k

Claims

1. A process of making a yarn having weavability features comprising t he s teps of :

- providing water-soluble synthetic fibers;

- spinning a fine yarn composed of an intimate blend of said first fibers and said water-soluble synthetic fibers,

characterized in that it comprises a step of sizing said fine yarn using a sizing solution, to obtain a sized fine yarn having an increased tensile strength as compared with the tensile strength of the original fine yarn.

2. A process of making a yarn as claimed in claim 1, wherein the count of said fine yarn is of the order of Nm 70 or more.

3. A process of making a yarn as claimed in claim 1 or 2, wherein the count of said fine yarn is Nm 90 or more .

4. A process of making a yarn as claimed in any of claims 1 to 3, wherein said first fibers are substantially made of pure cashmere or cashmere and silk.

5. A process of making a yarn as claimed in any of claims 1 to 4, wherein said water-soluble synthetic fibers substantially consist of polyvinyl alcohol (PVA) fibers.

6. A process of making a yarn as claimed in any of claims 1 to 5, wherein said step of sizing said fine yarn is carried out using a sizing solution comprising a composition of chitosan and/or derivatives thereof.

7. A process of making a yarn as claimed in claim

6, wherein said sizing solution comprises:

- chitosan, preferably low molecular weight chitosan, more preferably chitosan having a molecular weight of 150,000 Da, degree of deacetylation 75-85%; viscosity 20-200 cps at a concentration range of 0.5- 10% w/v, preferably 0.8-3% w/v, more preferably 1% w/v;

- acid aqueous solution and

- radical photoinitiator .

8. A process of making a yarn as claimed in claim

7, wherein said acid aqueous solution comprises acetic acid at a concentration of 1.5-3.8% v/v, preferably at a concentration of 1.8-2.22% v/v, more preferably at a concentration of 2% v/v.

9. A process of making a yarn as claimed in any of claims 6 to 8, comprising a step of crosslinking at least part of the chitosan and/or derivatives thereof of said sizing solution applied by sizing to the fibers of said fine yarn, to obtain a crosslinked reinforcement polymer, permanently anchored to the fibers of said fine yarn.

10. A process of making a yarn as claimed in claim 9, wherein said step of crosslinking at least part of the chitosan and/or derivatives thereof of said sizing solution applied to the fibers of said fine yarn, is preceded by a step of drying said fibers and/or said fine yarn and the sizing solution applied to the fibers of said fine yarn.

11. A process of making a yarn as claimed in claim 9 or 10, wherein said step of crosslinking at least part of the chitosan and/or derivatives thereof of said sizing solution applied to the fibers of said fine yarn, is carried out by a step of UV exposure of said chitosan and/or derivatives thereof of said sizing solution applied to the fibers of said fine yarn .

12. A process of making a yarn as claimed in any of claims 9 to 11, comprising a step of partial and calibrated removal of said crosslinked reinforcement polymer from said fibers of said fine yarn, such that the amount left on said fibers of said fine yarn of said crosslinked reinforcement polymer derived from chitosan and/or chitosan derivatives is 0.1-9 % w/w based on the dry weight of said fibers.

13. A process of making a yarn as claimed in any of claims 1 to 12, wherein said sizing solution comprises low-viscosity polyvinyl alcohol.

14. A process of making a fabric , characterized in that it comprises :

- a weaving step, which comprises the use of a plurality of fine yarns sized obtained by the process of making a yarn as claimed in any of claims 1 to 13 and comprising first fibers spun in intimate blend with second water-soluble synthetic fibers, to obtain a fabric, said first fibers comprising natural animal fibers, vegetable fibers, non-water-soluble synthetic polymer fibers, man-made natural polymer fibers, continuous filaments of animal origin and/or discontinuous filaments of animal origin, to be used at a pure state or blended together;

- a later step of dissolving from fibers of said fabric the water-soluble synthetic fibers contained in the yarns of said plurality of sized fine yarns of the fabric in an aqueous solution.

15. A process of making a fabric as claimed in claim 14, comprising a step of desizing the fibers of said fabric for removing the sizing solution contained in the yarns of said plurality of sized fine yarns.