WO2016034997A1

WO2016034997A1 - Sizing composition for fibers, yarns and/or fabrics and process for preparing such sizing composition

Info

Publication number: WO2016034997A1
Application number: PCT/IB2015/056588
Authority: WO
Inventors: Elisabetta CANEPA
Original assignee: Canepa S.P.A.
Priority date: 2014-09-03
Filing date: 2015-08-31
Publication date: 2016-03-10
Also published as: PL3189187T3; ES2882122T3; PT3189187T; EP3189187B8; EP3189187B1; DK3189187T3; EP3189187A1

Abstract

A sizing composition for fibers and yarns and/or fabrics made from such fibers, comprises chitosan having a molecular weight M_vof 150.000 Da, with a degree of deacetylation of 75-85% and an ambient temperature viscosity of 20-200 cps, said chitosan being dissolved in a 3% to 9% w/v acetic acid or citric acid solution, 3-9% v/v.

Description

Sizing composition for fibers, yarns and/or fabrics and process for preparing such sizing composition

DESCRIPTION

The present invention relates to a sizing composition for fibers and yarns and/or fabrics made from such fibers, particularly for natural animal fibers, vegetable fibers, 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.

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

As used herein, for example:

- thin yarns are intended to cover yarns having a yarn count ranging from 40 to 200 Nm, more preferably a yarn count of 65 Nm or more;

- animal fibers are intended to cover fleece or hair fibers (such as wool, alpaca, vicuna, cashmere, etc.);

- 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);

- synthetic polymer fibers are intended to cover, for example, polyamide, polyester, acrylic, polypropylene fibers, and others; - man-made natural fibers are intended to cover, for example, rayon viscose, modal, acetate, cupro, lyocell, and others.

The technique of applying a sizing composition to yarn fibers has been long known and is generally used to improve weavability of yams, particularly thin yams which are inherently difficult to weave as weft and/or warp yarns due o their thinness and their low tensile breaking load.

Sizing compositions can be generally removed from fabrics by suitable hydrolysis processes (e.g. acid, oxidizing or enzymatic hydrolysis) or are water- soluble such that they may be entirely removed from the fibers by appropriate finishing processing steps, such as washing or dyeing.

It shall be noted that additional needs are felt, such as:

- enhancing the mechanical properties of abrasion resistance of thin yarns, while reducing mechanical friction between weft yams and warp yarns, for trouble-free weaving;

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

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

In view of the above needs, sizing compositions have been tested, which could have a lasting effect on the fibers upon which they are applied, i.e. remain on the fibers even after the above mentioned finishing steps or after successive repeated washing steps. A substantially permanent presence of the sizing composition on the fibers of a yarn or a knit will allow fulfillment of the above mentioned additional needs.

For example, the use of sizing compositions comprising chitosan has been suggested, wherein, after application to the fibers, the chitosan contained in the sizing composition is crosslinked, whereby such chitosan generates a crosslinked polymer which remains permanently anchored to the fibers.

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

It shall be noted that the chitosan-based reinforcement product used in the sizing composition has much better sizing properties than other natural substances.

The above chitosan crosslinking step has the purpose of imparting a considerable physical-mechanical resistance to the fibers upon which chitosan is applied, while ensuring a long-lasting sanitization effect, resisting many repeated washes with hot and/or soapy water, as well as a considerable improvement in the dye affinity, of the treated fibers.

Conversely, the presence of the crosslinked chitosan and/or derivatives thereof on the fibers is likely to impart an excessive stiff feel to the fibers of the fabric or knit, and the fabric or knit are no longer soft and supple, i.e. are said to have a "hard feel", even when it is formed with thin fibers, e.g. cashmere fibers having a yarn count of 70 Nm.

Therefore, the invention is based on the problem of conceiving and providing a sizing composition that fulfills all the above mentioned needs, without imparting stiffness to the fibers of the fabric or knit upon substantially permanent application of such sizing composition to the fibers due to crosslinldng of cliitosan and/or derivatives thereof, contained in the sizing composition.

This problem is solved by a sizing composition as defined in claim 1.

In a further aspect, another problem consists in conceiving a method of preparing a sizing composition comprising cliitosan, which is effective and economic and can be easily implemented in a manufacturing process without requiring excessively long processing/preparation limes, while providing a sizing composition in which cliitosan is finely dissolved.

According to the invention, this additional technical problem is solved by means of a process as defined in claim 9 or in claim 10 for preparing a sizing composition of the invention.

In a further aspect, the invention also relates to a process as defined in claim 20 for crosslinldng cliitosan and/or derivatives thereof contained in the sizing composition of the invention on fibers impregnated with such sizing composition.

According to the invention, the sizing composition to be used for sizing the fibers (particularly natural animal fibers, vegetable fibers, 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) or theyarns, fabrics or knits obtained from such fibers is a sizing composition comprising cliitosan and/or derivatives thereof.

Advantageously, the chitosan and/or derivatives thereof as used for preparing the sizing composition of the invention have:

- a molecular weight ranging from 120,000 Da to 1 80,000 Da, preferably a molecular weight of the order of 150,000 Da, such molecular weight being expressed as viscosity average molecular mass, or Mv

- a degree of deacetylation of 70-90%, preferably a degree of deacetylation of 75-85% and/or

- a viscosity at ambient temperature (indicatively a temperature of about

25°C, Brookfield viscosity) of 20-200 cps, 1% w/w chitosan in 1 % w/v acetic or citric acid.

The chitosan and/or derivatives thereof are preferably dissolved in a 3% to 9% w/v inorganic acid solution, with a pH of less than 6.5.

Preferably, the chitosan and/or derivatives thereof are dissolved in a 3% to 9% w/v acetic acid or citric acid solution, 3-9% v/v.

By way of example only, pyruvic acid and tartaric acid may be used as further organic acids. Preferably, the chitosan and/or derivatives thereof in the sizing composition are in a solid state (e.g. powder, granules or flakes) or in a fluid state (e.g. in the form of a high-density paste), before being dissolved by agitation and/or by dispersion in said sizing composition.

Preferably, the above mentioned sizing composition also comprises starch and/or fish glue at a ratio of 1 : 1 to the amount of chitosan and/or derivatives thereof.

Preferably, to facilitate UV crosslinking of chitosan and/or derivative, the above mentioned sizing composition is enriched with additional crosslinking agents, comprising:

- double-bond monomers, preferably acrylic monomers with low environmental impact,

- drying oils, preferably linseed oil consisting of oleic and linoleic acid, and/or

- polycarboxylic acids.

Preferably, the above mentionedacrylic monomers are added in an amount substantially equal to the w/v percent of chitosan and/or derivatives thereof in the sizing composition.

Preferably, the above mentioned polycarboxylic acids comprise citric acid added in an amount not more than 2% w/v based on the amount of dry chitosan in the sizing composition.

Furthermore, crosslinking of chitosan and/or derivatives thereof, applied to the fibers, may be obtained by chemical and/or thermal treatment, with the sizing composition bath including formulations containing double-bond acrylic monomers, e.g. 2-hydroxy ethyl methacrylate (HEMA), or polycarboxylic acids, such as citric acid.

Advantageously, before being used for sizing fibers, the above mentioned sizing composition undergoes a dissolution step, by agitating the chitosan and/or derivatives thereof in the sizing composition for a period of more than 10 hours, and preferably the sizing composition undergoes agitation for a period of 12 hours to 24 hours, at a temperature ranging from 60°C to 80°C, preferably a temperature of about 70°C.

In a different and more advantageous production mode, alternative to the above described dissolution by agitation, the above mentioned sizing composition is prepared by submitting the sizing composition to be prepared to a step of dissolution by dispersion, during which the chitosan that has been added into the sizing composition is dissolved after being finely dispersed in the sizing composition. The above mentioned step of dissolution by dispersion of the chitosan and/or derivatives thereof is carried out by dispersion means that are adapted to achieve fine dispersion of the chitosan and/or derivatives thereof in the bath (i.e. the sizing composition) by high-speed impacts with the solid chitosan particles contained in the bath.

Preferably, these dispersion means comprise at least one COWLES-type impeller or an impeller having blades, particularly, but without limitation, a toothed-disk impeller, with the teeth formed of blades, preferably having a sawtooth shape. According to preferred embodiment, these blades or teeth are placed at the outer peripheral edge of the impeller disk and/or project out of both sides of said disk.

According to a preferred embodiment, the COWLES-type impeller or the impeller with blades comprises a varying number of peripheral teeth, e.g. ranging from ten to forty. The number of teeth of the impeller varies, namely increases, with the outside diameter of the impeller.

The outside diameter of the COWLES-type impeller or the impeller with blades is at least 5 cm, and may be up to 100 cm in the case of large dispersers. Preferably, the diameter of the COWLES-type impeller or the impeller with blades ranges from 12 cm to 40 cm.

In short, the bath in which the chitosan and/or derivatives thereof are added in a solid state (e.g. powder, granules or flakes) or in a fluid state (e.g. in the form of a high-density paste) is contained in a tank of a disperser in which said COWLES impeller or said impeller with blades is rotatably actuated at high speed, i.e. at a peripheral speed of rotation of the impeller of 10 meters/second or more and less than 40 m/second, preferably at a peripheral speed of the impeller of 13-32 meters/second. This will afford a surprising and effective dispersion of the particles of chitosan and/or derivatives thereof in the bath, to complete and rapid dissolution of the particles of chitosan and/or derivatives thereof in the bath, leading to the formation of the sizing composition of the invention.

According to a preferred embodiment, the inside diameter of the above mentioned tank is twice to six times the maximum outside diameter of the COWLES-type impeller or the impeller with blades. More preferably, the inside diameter of the above mentioned tank is three to four times the maximum outside diameter of the COWLES-type impeller or the impeller with blades, which will provide an advantageous condition when the inside diameter of the tank is about three times the maximum outside diameter of the COWLES-type impeller or the impeller with blades.

Advantageously, complete dispersion of particles of chitosan and/or derivatives thereof in the bath, which is achieved using a COWLES impeller or an impeller with blades, and leads to the dissolution of such particles of chitosan and/or derivatives thereof in the bath, and to the formation of the sizing composition comprising chitosan and/or derivatives thereof, is obtained in very short process times, indicatively also less than one hour, e.g. of the order of 35- 45 minutes, with no need to extend said dispersion step to multiple hours, as required by the dissolution by agitation as described above.

It shall be further noted that the above mentioned complete dissolution by dispersion of particles of chitosan and/or derivatives thereof in the bath, which is achieved using a COWLES impeller or an impeller with blades, can be also achieved at ambient temperature, indicatively also at temperatures of about 15°C, optimal results being also achievable with temperatures of less than 40°C. Therefore, said dissolution by dispersion of chitosan and/or derivatives thereof in the bath does not require extended heating at temperatures of the order of 60- 80°C, as required in dissolution by agitation as described above.

Advantageously, the crosslinking of chitosan and/or derivatives thereof contained in the above mentioned sizing composition on fibers impregnated with such sizing composition is obtained by exposing the fibers impregnated with said sizing composition to the radiation of a UV lamp.

Preferably, the step of crosslinking on the fibers impregnated with chitosan and/or derivatives thereof contained in such sizing composition is obtained by exposing the fibers impregnated with said sizing composition to the radiation of a UV lamp:

- having a power of 400 W to 600 W, preferably a power of about 500W, and

- having an intensity of 10 mV/cm² to 30 mV/cm², preferably an intensity of about 20 mV/cm²,

for an exposure time ranging from 20 to 80 seconds, preferably for an exposure time ranging from 30 to 65 seconds, at a distance from the UV lamp ranging from 15 cm to 30 cm, preferably at a distance of the order of 20 cm from the UV lamp.

Preferably, the above mentioned step of exposure of the impregnated fibers to the radiation of the UV lamp is preceded by a step of wringing, partially drying or completely drying the fibers.

Alternatively, as described above, the crosslinking of the fibers of chitosan and/or derivatives thereof, contained in the above mentioned sizing composition may be obtained by chemical and/or thermal treatment, possibly after a step of wringing, partially drying or completely drying the fibers.

Experimental tests proved that the use of the sizing composition of the invention for sizing the fibers, and the later step of crosslinking and/or derivatives thereof contained in the sizing composition can provide fibers, e.g. in the forms of a yarn, a fabric or a knit, that can fulfill the above mentioned needs. This is because said fibers have an amount of crosslinked chitosan and/or chitosan derivatives substantially permanently applied thereto, such amount allowing to achieve the desired beneficial effects, without causing the fibers to have a stiff or poorly soft feel.

Namely, according to the specific compounds that form the sizing composition in use, the specific method of producing such sizing composition and the specific crosslinking method, the sized fibers only have crosslinked, i.e. permanently applied, thereto, the amount of crosslinked chitosan and/or crosslinked chitosan derivatives that is required to achieve the desired effects, and the rest of the sizing composition may be removed, by desizing, with a simple washing step with water at 35-40°C or a later finishing step. Particularly, such later water washing or finishing step only removes the chitosan and/or derivatives thereof that have been crosslinked but do not adhere to the fibers.

In the light of the above disclosure, the sizing composition as described above, and the process of preparing the sizing compositionof the invention and the crosslinking process in use, can fulfill the above mentioned needs, while obviating the lamented drawbacks.

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

Claims

1. A sizing composition for fibers and yarns and/or fabrics made from such fibers, particularly for natural animal fibers, vegetable fibers, 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, wherein said sizing composition comprises chitosan and/or derivatives thereof, characterized in that:

- said chitosan and/or derivatives thereof have a molecular weight M_v ranging from 120,000 Da to 180,000 Da, preferably a molecular weight M_v of the order of 1 50,000 Da, with a degree of deacetylation of 70-90%, and an ambient temperature viscosity of 20-200 cps with 1 % w/w chitosan in 1 % w/v acetic or citric acid;

- said sizing composition comprises an inorganic acid solution with a pH of less than 6.5 at 3-9% v/v, in which 3% to 9% w/v of said chitosan and/or derivatives thereof are dissolved:

- by agitation or

- by a dispersion step that is carried out using a COWLES-type impeller or an impeller with blades, preferably a sawblade impeller, which can impact the solid particles of chitosan and/or derivatives thereof at high speed.

2. A sizing composition as claimed in claim 1 , wherein said inorganic acid solution with a pH of less than 6.5 at 3-9% v/v, is an acetic acid, a citric acid, a pyruvic acid or a tartaric acid solution.

3. A sizing composition as claimed in claim 1 or 2, wherein the degree of deacetylation of said chitosan and/or derivatives thereof is 75-85%.

4. A sizing composition as claimed in claim 1 , 2 or 3, wherein the chitosan and/or derivatives thereof are in a solid state, preferably powder, granules or flakes, or in a fluid state, e.g. in the form of a high-density paste, before being dissolved by agitation and/or dispersion in said solution containing an inorganic acid with a pH of less than 6.5 at 3-9% v/v.

5. A sizing composition as claimed in any of claims 1 to 4, wherein said solution of chitosan and/or derivatives thereof in an inorganic acid, with a pH of less than 6.5 comprises starch and/or fish glue at a ratio of 1 : 1 to the amount of chitosan and/or derivatives thereof.

6. A sizing composition as claimed in any of claims 1 to 5 wherein, to facilitate UV crosslinking of chitosan and/or derivative, said sizing composition is enriched with additional crosslinking agents, comprising:

- polycarboxylic acids.

7. A sizing composition as claimed in claim 6, wherein said acrylic monomers are added in an amount substantially equal to the w/v percent of chitosan and/or derivatives thereof in the sizing composition.

8. A sizing composition as claimed in claim 6, wherein said polycarboxylic acids comprise citric acid added in an amount not more than 2% based on the amount of dry chitosan in the sizing composition.

9. A process of preparing a sizing composition as claimed in any of claims 1 to 8, wherein said sizing composition comprising chitosan and/or derivatives thereof undergoes agitation, for dissolving the chitosan and/or derivatives thereof for a period of more than 10 hours, and preferably undergoes agitation for a period of 12 hours to 24 hours, at a temperature ranging from 60°C to 80°C, preferably a temperature of about 70°C.

10. A process of preparing a sizing composition as claimed in any of claims 1 to 8, wherein said sizing composition comprising chitosan and/or derivatives thereof undergoes a step of dissolution by dispersion, which is carried out by dispersion means that are adapted to achieve fine dispersion of the chitosan and/or derivatives thereof contained in the sizing composition by high-speed impacts with the solid particles of chitosan and/or derivatives thereof contained in the bath, to dissolution of said solid particles of chitosan and/or derivatives thereof in the bath.

11. A process of preparing a sizing composition as claimed in claim 10, wherein said dispersion means for carrying out said step of dispersion of chitosan and/or derivatives thereof comprise at least one COWLES-type impeller or an impeller having blades, particularly a toothed-disk impeller, with the teeth formed of blades, preferably having a sawtooth shape.

12. A process of preparing a sizing composition as claimed in claim 1 1 , wherein said step of dispersion of chitosan and/or derivatives thereof is carried out by introducing the bath in which chitosan and/or derivatives thereof have been added in a solid or fluid state, into a tank of a disperser in which said COWLES impeller or said impeller with blades is rotatably, preferably at a peripheral speed of rotation of the impeller of more than 10 meters/second and less than 40 m/second, preferably at a peripheral speed of the impeller of 13-32 meters/second.

13. A process of preparing a sizing composition as claimed in any of claims 9 to 12, wherein said chitosan and/or derivatives thereof have a molecular weight M_v ranging from 120,000 Da to 180,000 Da, preferably a molecular weight M_v of the order of 150,000 Da, with a degree of deacetylation of 70- 90%, and an ambient temperature viscosity of 20-200 cps with 1% w/w chitosan in 1% w/v acetic or citric acid;

- said sizing composition comprises an inorganic acid solution with a pH of less than 6.5 at 3-9% v/v, in which 3% to 9% w/v of said chitosan and/or derivatives thereof are dissolved, preferably an acetic acid, a citric acid, a pyruvic acid or a tartaric acid solution.

14. A process of preparing a sizing composition as claimed in claim 13, wherein the degree of deacetylation of said chitosan and/or derivatives thereof is 75-85%.

15. A process of preparing a sizing composition as claimed in any of claims 9 to 14, wherein said chitosan and/or derivatives thereof are dissolved by agitation or by dispersion in said sizing composition from a solid state, preferably powder, granules or flakes, or from a fluid state, preferably in the form of a high-density paste.

16. A process of preparing a sizing composition as claimed in any of claims 9 to 15, wherein said solution of chitosan and/or derivatives thereof in an inorganic acid, with a pH of less than 6.5 comprises starch and/or fish glue at a ratio of 1 : 1 to the amount of chitosan and/or derivatives thereof.

17. A process of preparing a sizing composition as claimed in any of claims 9 to 16 wherein, to facilitate UV crosslinking of chitosan and/or derivative, said sizing composition is enriched with additional crosslinking agents, comprising:

- polycarboxylic acids.

18. A process of preparing a sizing composition as claimed in claim 17, wherein said acrylic monomers are added in an amount substantially equal to the percent of chitosan and/or derivatives thereof in the sizing composition.

19. A process of preparing a sizing composition as claimed in claim 18, wherein said polycarboxylic acids comprise citric acid added in an amount not more than 2% based on the amount of dry chitosan in the sizing composition.

20. A process of crosslinking chitosan and/or derivatives thereof contained in the sizing composition as claimed in any of claims 1 to 8, on fibers impregnated with said sizing composition, wherein said crosslinking step is earned out by:

- by exposing the fibers impregnated with said sizing composition to the radiation of a UV lamp and/or

- by chemical and/or thermal treatment, preferably with the sizing composition bath including formulations containing double-bond acrylic monomers, preferably 2-hydroxy ethyl methacrylate (HEMA), or polycarboxylic acids, preferably citric acid.

21. A process of crosslinking chitosan and/or derivatives thereof as claimed in claim 20, wherein said crosslinking step is carried out by exposing said fibers impregnated with said sizing composition to the radiation of a UV lamp:

- having a power of 400W to 600W, preferably a power of about 500W, and 2 2

- having an intensity of 10 mV/cm to 30 mV/cm , preferably an intensity of about 20 mV/cm ,

for an exposure time ranging from 20 to 80 seconds, preferably for an exposure time ranging from 30 to 65 seconds, at a distance from the UV lamp ranging from 15 cm to 30 cm, preferably at a distance from the UV lamp of the order of 20 cm.

22. A process for crosslinking chitosan and/or derivatives thereof as claimed in claim 20 or 21, comprising a step of wringing, partially drying or completely drying the fibers impregnated with said sizing composition, before carrying out said crosslinking step on the impregnated fibers.