US20170044711A1

US20170044711A1 - Process for improving the chemical and/or physical properties of a yarn or fabric

Info

Publication number: US20170044711A1
Application number: US15/304,329
Authority: US
Inventors: Elisabetta CANEPA
Original assignee: CANEPA SpA
Current assignee: CANEPA SpA
Priority date: 2014-04-18
Filing date: 2015-04-17
Publication date: 2017-02-16
Also published as: KR20160145053A; JP2017511433A; DK3132086T3; WO2015159262A1; JP6667451B2; CN106460307B; EP3132086A1; EP3132086B1; CN106460307A

Abstract

A process for improving the chemical and/or the physical properties of a yarn which comprises the step of applying a chitosan-based reinforcement product, a later step of crosslinking the chitosan and a partial and calibrated desizing step for removing the crosslinked chitosan, and the desizing step being carried out by mechanical process.

Description

The present invention relates to a process for improving the chemical and/or physical properties of a yarn or fabric, preferably a thin yarn or fabric made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, used at pure state or blended together
As used herein, the term weaving shall be intended to cover both warp-and-weft weaving and knit-weaving.
As used herein, for example:

- a thin yarn is intended to cover yarns having a yarn count ranging from 50 to 200 Nm;
- animal fibers are intended to cover fibers obtained from insects (e.g. silkworm) or from fleece (e.g. wool, alpaca, vicuna, cashmere, etc.);
- vegetable fibers are intended to cover all the fibers obtained from plants, shrubs, inflorescences, leaves (such as ramie, bamboo, cotton, linen, etc.).

Thin yarns of the above mentioned type are known to be difficult to weave together, due to their thinness which makes them prone to breaking during weaving.
For this reason a weaving technique is known in the art, e.g. from WO 2013/057723, which includes the steps of applying a reinforcement solution comprising chitosan and/or derivatives thereof to the fibers of the yarn, crosslinking the chitosan and/or derivatives thereof, e.g. by exposure to UV radiation and a desizing step, for removing the chitosan and/or derivatives thereof, as well as a partial and calibrated desizing step for removal of both the chitosan and/or derivatives thereof after crosslinking.
It shall be noted in this respect that chitosan and/or its derivatives are easily removed because chitosan and/or its derivatives are soluble under appropriate conditions, such removal being simply obtained by submitting the yarn or fabric to a washing step or one of the usual finishing steps, e.g. a dyeing step obtained by immersing the fibers in a suitable dyeing solution at temperatures above 60° C.
Conversely, the crosslinked chitosan and/or crosslinked chitosan derivatives generate a water-insoluble crosslinked polymer which remains permanently anchored to the fibers even after a number of successive washing steps with hot and/or soapy water or after a hot-dyeing step.
Particularly, crosslinking of chitosan and/or derivatives thereof can increase cohesion thereof to the fibers of the yarns. Particularly, the crosslinked polymer resulting from crosslinking of chitosan and/or derivatives thereof is applied to the treated fibers in substantially undissolvable and durable fashion. The presence of this crosslinked polymer resulting from crosslinking of chitosan and/or derivatives thereof can:

- impart a considerable physico-mechanical resistance to the yarn;
- provide a sanitizing, antifelting and antibacterial effect to the fibers, as well as
- substantially improving finish affinity, particularly dye and print affinity, especially to reactive dyes reacting with —OH and —NH₂groups.

In order to obtain yarns or fabrics with fibers having both the above mentioned advantages and the initial softness, volume, gloss and lightness properties as required, the amount of such crosslinked polymer resulting from crosslinking of chitosan and/or derivatives thereof on the fibers shall not exceed the amount that is strictly sufficient to obtain the required benefits. Thus, for example, any excess of such crosslinked polymer on the fibers will cause the drawback that the yarns and fabrics will exhibit a high resistance but also excessive rigidity.
Therefore, a need is felt for a partial and calibrated desizing step, for removing the crosslinked polymer resulting from crosslinking of chitosan and/or derivatives thereof from the fibers of the yarn or fabric.
According to the prior art, such desizing step may be:

- an enzymatic desizing step, preferably using amylase and/or cellulase enzymes, within the range of pHs, temperatures and activities specific to the enzyme and the relevant substrate or
- a chemical desizing step, e.g. using hydrolyzing acids, preferably diluted hydrochloric and/or sulfuric acid.

Concerning these desizing techniques for partial and calibrated removal of the crosslinked polymer resulting from crosslinking of chitosan and/or derivatives thereof from the fibers of the yarn or fabric, it shall be noted that they cannot be readily implemented, as preventive tests should be made for each different type of fiber to be treated. Furthermore, it shall be noted that the possibility of implementing such partial and calibrated desizing step by enzymatic or chemical procedures requires the introduction of special equipment or parts in the spinning and/or weaving lines, which are not typically provided, in other words these techniques require the provision of a special production line.
Therefore, the invention is based on the problem of conceiving and providing a process for improving the chemical and/or physical properties of a yarn or fabric, to fulfill the above need, while obviating the above prior art drawbacks.
This problem is solved by a process for improving the chemical and/or physical properties of a yarn, particularly a fine yarn, or a fabric as defined in claim 1.
In a further aspect, the invention also relates to the use of a reinforcement product comprising a composition of chitosan and/or derivatives thereof as defined in claim 15.
According to the invention, the yarn, which is preferably a fine yarn, comprises natural animal fibers and/or vegetable fibers, and/or man-made natural polymer fibers and/or man-made natural crosslinked polymer fibers, used at pure state or blended together.

EXAMPLE 1

A process of the invention for improving the chemical and/or physical properties of a yarn made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together, comprises the steps of:
a) providing a yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together;
b) preparing a sizing solution comprising a composition of chitosan and/or derivatives thereof as a reinforcement product;
c) sizing said yarn with said sizing solution to apply said reinforcement product comprising chitosan and/or derivatives thereof to the fibers of said yarn by at least partial impregnation and/or coating;
d) at least partially crosslinking the chitosan and/or derivatives thereof of said reinforcement product applied to the fibers by said sizing step c), to obtain a crosslinked reinforcement polymer from said chitosan and/or derivatives thereof, said polymer being permanently anchored to the fibers of said yarn and
e) performing a desizing step, for partial and calibrated removal of said crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof, and anchored to the fibers of said yarn, from such fibers of said yarn.
Advantageously, the above mentioned desizing step e), for partial and calibrated removal of said crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from such fibers of said yarn is carried out by mechanical means.
The yarn obtained by the above described process steps b), c), d) and e) is a yarn having improved mechanical strength, remarkable sanitizing, antibacterial and antifelting properties and an excellent finish affinity (e.g. dye and print affinity), partial and calibrated desizing for removal of the crosslinked polymer being advantageously obtained simply and quickly by mechanical means.

EXAMPLE 2

A process for improving the chemical and/or physical properties of a fabric or knit comprising yarns made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together, comprising a step of warp-and-weft weaving of said yarns or a step of knitting of said yarns, wherein at least one or both of the warp and weft yarns, preferably the warp yarn only, used in this weaving step or a yarn used in said knitting step, is a yarn that undergoes the following process steps:
a) providing a yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together;
b) preparing a sizing solution comprising a composition of chitosan and/or derivatives thereof as a reinforcement product;
c) sizing said yarn with said sizing solution to apply said reinforcement product comprising chitosan and/or derivatives thereof to the fibers of said yarn by at least partial impregnation and/or coating and
d) at least partially crosslinking the chitosan and/or derivatives thereof of said reinforcement product applied to the fibers by said sizing step c), to obtain a crosslinked reinforcement polymer from said chitosan and/or derivatives thereof, said polymer being permanently anchored to the fibers of said yarn.
After said crosslinking step d), the yarn undergoes a step f) of warp-and-weft weaving of said yarns or a step of knitting of said yarns, wherein one or both of the warp and weft yarns, preferably the warp yarn only, used in this weaving step or in said knitting step, is a yarn that undergoes said process steps b), c) and d).
After said weaving or knitting step f), the fabric or knit so obtained undergo a desizing step g) with partial and calibrated removal of said crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof, from the fibers of the fabric or knit.
Advantageously, the above mentioned desizing step g) with partial and calibrated removal of said crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from such fibers of said yarn is at least partially carried out by acting upon said fibers by mechanical means.

EXAMPLE 3

A process for improving the chemical and/or physical properties of a fabric, knit or garment comprising at least one yarnmade from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together. This process comprises the steps of:
h) providing a finished fabric, knit or garment comprising at least one yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, at pure state or blended together;
b) preparing a sizing solution comprising a composition of chitosan and/or derivatives thereof as a reinforcement product;
i) sizing said fabric, knit or garment with said sizing solution to apply said reinforcement product comprising chitosan and/or derivatives thereof to the fibers of said fabric, knit or garment by at least partial impregnation and/or coating;
l) after said sizing step i), crosslinking the chitosan and/or derivatives thereof of said chitosan composition to obtain a crosslinked polymer from said chitosan and/or derivatives thereof, which is permanently anchored to the fibers of said fabric, knit or garment and
m) after said step 1) of at least partially crosslinking the chitosan and/or derivatives thereof of said composition, performing a desizing step with partial and calibrated removal of said crosslinked polymer derived from chitosan and/or derivatives thereof, from the fibers of said fabric, knit or garment.
Advantageously, the above mentioned desizing step m) with partial and calibrated removal of said crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from the fibers of said fabric, knit or garment is at least partially carried out by acting upon said fibers by mechanical means.
Therefore, according to the invention, in all the above described examples, the partial and calibrated desizing step (i.e. a sizing step that does not involve complete removal of the crosslinked polymer applied on the fibers), is at least partially carried out by mechanical desizing, whereby the fibers to be desized are physically acted upon by abrasion, rubbing, brushing and/or by treatments adapted to remove part of the crosslinked chitosan and/or chitosan-derived polymer from the fibers, such as by ultrasonic treatment.
Advantageously, said mechanical abrasion and/or rubbing treatment for partial and calibrated removal of the crosslinked chitosan and/or chitosan-derived polymer may be carried out on the yarn during weaving, e.g. by sliding the yarn in contact with special rigid surfaces. These rigid surfaces may consist of the dent and slaying surfaces of a reed, eye holes, namely healds or Jacquard heddles, through which the yarn is slid during weaving, surfaces of rollers contacted by the sliding yarn during weaving, bristles of a brush, and others.
These mechanical abrasion and/or rubbing treatments may be carried out on yarn fibers even after the weaving or knitting step, i.e. by directly acting upon the finished fabric or knit. In this case, these mechanical treatments are advantageously carried out by brushing the fabric or the knit.
According to an alternative embodiment, the partial and calibrated mechanical desizing step for removing the crosslinked chitosan and/or chitosan-derived polymer from the fibers of the yarn or fabric or knit, may be carried out by ultrasonic treatment of such fibers. Conveniently this may take place, for example, with the fibers of the yarn, fabric or knit immersed in a liquid in which an ultrasound-emitting probe is introduced.
Advantageously, the ultrasonic treatment of the fibers may be carried out at the same time as a step of weaving or finishing during which the fibers are already immersed in a bath, for example during a step of washing the fibers or knit or during a dyeing step.
It shall be understood from the above that, with the possibility of carrying out the desizing step by mechanical means, no further processing step shall be added to those required for producing the yarn, fabric or knit, and no further special equipment shall be added to the one that is specially required for partial and calibrated desizing for removal of the crosslinked chitosan and/or chitosan-derived polymer.
The possibility of carrying out partial and calibrated mechanical desizing for removal of the crosslinked polymer on the fibers does not exclude the possibility that such partial and calibrated desizing step may be also carried out before or after as:

Particularly, the partial and calibrated mechanical desizing step may be carried out in addition to a chemical or an enzymatic desizing step.
The partial and calibrated desizing step using ultrasounds may be carried out at the same time as a partial and calibrated chemical or enzymatic desizing step, using the same bath, which will afford a synergy of effects between the different desizing steps.
According to a preferred embodiment, after the sizing step, the step of crosslinking the chitosan and/or its derivatives is preceded by a a step of drying the fibers of the yarn, fabric or knit and the crosslinked chitosan and/or chitosan-derived polymer applied to the fibers of the yarn, fabric or knit, to thereby facilitate the later chitosan crosslinking step.
Preferably, the chitosan crosslinking step is carried out by a step of UV exposure of the fibers of the yarn, fabric, knit or garment, chemical crosslinking being also possibly provided.
Preferably, the step of sizing said finished fabric, knit or garment is carried out by foularding and/or impregnation of the finished fabric, knit or garment in the sizing solution.
Preferably, such step of sizing the fibers is carried out using a sizing solution comprising:

- low-molecular-weight chitosan;
- acid aqueous solution;
- radical photoinitiator.

Preferably, the chitosan in use has a low molecular weight, e.g. of the order of 150,000 Da. Particularly, it is a chitosan with 75÷85% degree of deacetylation; 20÷200 cps viscosity at a concentration range of 0.5÷10% w/v, preferably 0.8÷3% w/v, more preferably 1% w/v;
Preferably, 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.
Preferably, said step of sizing the fibers of the yarn, fabric, knit or garment with said sizing solution is carried out with a bath ratio ranging from 1÷7 to 1÷35, preferably with a bath ratio ranging from 1÷10 to 1÷30, more preferably with a bath ratio ranging from 1÷16 to 1÷24.
Preferably, said step of sizing said finished fabric, knit or garment with said sizing solution is carried out with a bath ratio ranging from 1÷7 to 1÷35, preferably with a bath ratio ranging from 1÷10 to 1÷30, more preferably with a bath ratio ranging from 1÷16 to 1÷24.
Preferably, this desizing step, with partial and calibrated removal of said crosslinked chitosan-derived reinforced polymer from the fibers of said yarn, leaves said crosslinked chitosan-derived reinforcement polymer on the fibers of said yarn subjected to said sizing step, in an amount of 0.3÷9% w/w based on the dry weight of the yarn after said sizing step.
The above disclosure is susceptible to a number of changes and variants within the inventive concept, as outlined by the annexed claims.
Thus, for example, the yarn, which is preferably a thin yarn, may also comprise a doubled yarn with a monofilament or multifilament yarn containing chitosan or be doubled with a yarn made of discontinuous fibers, containing chitosan.

Claims

1-15. (canceled)

16. A process for improving chemical and/or physical properties of a yarn made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, either in a pure state or blended together, the process comprising:

a) providing a yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, either in the pure state or a blended together;

b) preparing a sizing solution comprising a composition of chitosan and/or derivatives thereof as a reinforcement product;

c) sizing the yarn with the sizing solution to apply the reinforcement product comprising chitosan and/or derivatives thereof to the fibers of the yarn by at least partial impregnation and/or coating;

d) at least partially crosslinking the chitosan and/or derivatives thereof of the reinforcement product applied to the fibers by the sizing step c), to obtain a crosslinked reinforcement polymer from the chitosan and/or derivatives thereof, and the polymer being permanently anchored to the fibers of the yarn and

e) performing a desizing step, for partial and calibrated removal of the crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof, and anchored to the fibers of the yarn, from such fibers of the yarn,

wherein the above mentioned desizing step e) for partial and calibrated removal of the crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from such fibers of the yarn is carried out by mechanical means,

17. A process for improving the chemical and/or physical properties of a fabric or knit comprising yarns made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, either in a pure state or blended together, the process comprising:

a) providing a yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, either in the pure state or blended together;

d) at least partially crosslinking the chitosan and/or derivatives thereof of the reinforcement product applied to the fibers by the sizing step c), to obtain a crosslinked reinforcement polymer from the chitosan and/or derivatives thereof, and the polymer being permanently anchored to the fibers of the yarn;

e) performing a step of warp-and-weft weaving of the yarns or a step of knitting of the yarns, wherein one or both of the warp and weft yarns, preferably the warp yarn only, used in this weaving step or in the knitting step, is a yarn that undergoes the process steps b), c) and d);

f) performing a desizing step, for partial and calibrated removal of the crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof, from the fibers of the fabric or knit,

wherein the desizing step g) with partial and calibrated removal of the crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from such fibers of the yarn is at least partially carried out by acting upon the fibers by mechanical means.

18. A process for improving the chemical and/or physical properties of a fabric, knit or garment comprising at least one yarn made from natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers, either in a pure state or blended together, the process comprising:

a) providing a finished fabric, knit or garment comprising at least one yarn made of natural animal fibers, vegetable fibers, synthetic polymer fibers and/or man-made natural polymer fibers at pure state or blended together:

c) sizing the fabric, knit or garment with the sizing solution to apply the reinforcement product comprising chitosan and/or derivatives thereof to the fibers of the fabric, knit or garment by at least partial impregnation and/or coating;

d) crosslinking the chitosan and/or derivatives thereof of the chitosan composition to obtain a crosslinked polymer from the chitosan and/or derivatives thereof, which is permanently anchored to the fibers of the fabric, knit or garment and

e) performing a desizing step, with partial and calibrated removal of the crosslinked polymer derived from chitosan and/or derivatives thereof, from the fibers of the fabric, knit or garment,

wherein the desizing step e) with partial and calibrated removal of the crosslinked reinforcement polymer derived from chitosan and/or derivatives thereof from the fibers of the fabric, knit or garment, is at least partially carried out by acting upon the fibers by mechanical means.

19. The process according to claim 16, wherein the partial and calibrated desizing step is at least partially carried out by mechanical desizing, whereby the fibers to be desized are physically acted upon by one of abrasion, rubbing, brushing and/or by treatments adapted to remove part of the crosslinked chitosan and/or chitosan-derived polymer from the fibers.

20. The process according to claim 19, wherein the mechanical desizing step for physically acting upon the fibers to be desized by abrasion and/or rubbing is carried out on the yarn during the weaving step.

21. The process according to claim 19, wherein the mechanical desizing step for physically acting upon the fibers to be desized by abrasion and/or rubbing is carried out by sliding the yarn in contact with rigid surfaces.

22. The process according to claim 21, wherein the rigid surfaces consist of the surfaces of the reed dents, eye holes through which the yarn is slid during weaving, surfaces of rollers contacted by the yarn and/or the bristles of a brush.

23. The process according to claim 16, wherein the partial and calibrated mechanical desizing step for removing the crosslinked chitosan and/or chitosan-derived polymer from the fibers is carried out by ultrasonic treatment of such fibers while the fibers are immersed in a bath.

24. The process according to claim 23, wherein the ultrasonic treatment of the fibers is carried out at the same time as a step weaving or finishing processing step, during which the fibers are already immersed in the bath.

25. The process according to claim 16, wherein the partial and calibrated mechanical desizing step is carried out in addition to a chemical or an enzymatic desizing step.

26. The process according to 16, wherein the partial and calibrated mechanical desizing step by ultrasonic treatment of the fibers upon which the crosslinked chitosan and/or chitosan-derived polymer is applied is carried out substantially at the same time as the partial and calibrated chemical or enzymatic desizing step, using a same bath,

27. The process according to claim 16, wherein the step of crosslinking the chitosan of the reinforcement product applied to the fibers is preceded by the step of drying the fibers of the yarn and the chitosan of the reinforcement product applied to the fibers of the yarn, to thereby facilitate the later chitosan crosslinking step.

28. A use of a reinforcement product comprising a composition of chitosan and/or derivatives thereof in the process according to claim 16, for improving the chemical and/or physical properties of a yarn.

29. The process according to claim 17, wherein the partial and calibrated desizing step is at least partially carried out by mechanical desizing, whereby the fibers to be desized are physically acted upon by at least one of abrasion, rubbing, brushing and/or by treatments adapted to remove part of the crosslinked chitosan and/or chitosan-derived polymer from the fibers.

30. The process according to claim 29, wherein the mechanical desizing step for physically acting upon the fibers to be desized by abrasion and/or rubbing is carried out on the yarn during the weaving step.

31. The process according to claim 29, wherein the mechanical desizing step for physically acting upon the fibers to be desized by at least one of abrasion and/or rubbing is carried out by sliding the yarn in contact with rigid surfaces.

32. The process according to claim 31, wherein the rigid surfaces consist of the surfaces of the reed dents, eye holes through which the yarn is slid during weaving, surfaces of rollers contacted by the yarn and/or the bristles of a brush.

33. The process according to claim 29, wherein the mechanical desizing step for physically acting upon the fibers to be desized by abrasion and/or rubbing is carried out on the fabric, knit or garment.

34. The process according to claim 33, wherein the mechanical desizing step by abrasion and/or rubbing is carried out by brushing the fabric, knit and/or garment, or by sliding the fabric in contact with rigid surfaces.

35. The process according to claim 17, wherein the partial and calibrated mechanical desizing step for removing the crosslinked chitosan and/or chitosan-derived polymer from the fibers is carried out by ultrasonic treatment of such fibers while the fibers are immersed in a bath.

36. The process according to claim 35, wherein the ultrasonic treatment of the fibers is carried out at a same time as a step weaving or finishing processing step, during which the fibers are already immersed in a bath.

37. The process according to claim 17, wherein the partial and calibrated mechanical desizing step is carried out in addition to a chemical or enzymatic desizing step.

38. The process according to claim 17, wherein the partial and calibrated mechanical desizing step by ultrasonic treatment of the fibers upon which the crosslinked chitosan and/or chitosan-derived polymer is applied is carried out substantially at the same time as the partial and calibrated chemical or enzymatic desizing step, using the same bath.

39. The process for improving the chemical and/or physical properties of a yarn according to claim 17, wherein the step of crosslinking the chitosan of the reinforcement product applied to the fibers is preceded by the step of drying the fibers of the yarn and the chitosan of the reinforcement product applied to the fibers of the yarn, to thereby facilitate the later chitosan crosslinking step.

40. A use of a reinforcement product comprising a composition of chitosan and/or derivatives thereof in the process according to claim 29 for improving the chemical and/or physical properties of a yarn.

41. The process according to claim 18, wherein the partial and calibrated desizing step is at least partially carried out by mechanical desizing, whereby the fibers to be desized are physically acted upon by at least one of abrasion, rubbing, brushing and/or by treatments adapted to remove part of the crosslinked chitosan and/or chitosan-derived polymer from the fibers.

42. The process according to claim 41, wherein the mechanical desizing step for physically acting upon the fibers to be desized by abrasion and/or rubbing is carried out on the fabric, knit or garment.

43. The process according to claim 42, wherein the mechanical desizing step by abrasion and/or rubbing is carried out by brushing the fabric, knit and/or garment, or by sliding the fabric in contact with rigid surfaces.

44. The process according to claim 18, wherein the partial and calibrated mechanical desizing step for removing the crosslinked chitosan and/or chitosan-derived polymer from the fibers is carried out by ultrasonic treatment of such fibers, while the fibers are immersed in a bath.

45. The process according to claim 44, wherein the ultrasonic treatment of the fibers is carried out at a same time as a step weaving or finishing processing step, during which the fibers are already immersed in a bath.

46. The process according to claim 18, wherein the partial and calibrated mechanical desizing step is carried out in addition to a chemical or an enzymatic desizing step.

47. The process according to claim 18, wherein the partial and calibrated mechanical desizing step by ultrasonic treatment of the fibers upon which the crosslinked chitosan and/or chitosan-derived polymer is applied is carried out substantially at a same time as the partial and calibrated chemical or enzymatic desizing step, using a same bath.

48. The process according to claim 18, wherein the step of crosslinking the chitosan of the reinforcement product applied to the fibers is preceded by the step of drying the fibers of the yarn and the chitosan of the reinforcement product applied to the fibers of the yarn, to thereby facilitate the later chitosan crosslinking step.