EP2486185B1 - Coated lightweight fabric, in particular for webs for flights - Google Patents

Description

The present invention relates to a light fabric formed of warp yarns and continuous weft yarns, this fabric being coated on one and / or both sides with a polyurethane. This lightweight fabric finds its application particularly in the field of flight sails. The invention also relates to a method of manufacturing this fabric.

In the field of flight sails, such as paragliding, fabric manufacturers have long sought to combine lightness, low porosity and durability. The equation is difficult to solve, the decrease in porosity being generally synonymous with weight increase. Indeed, the porosity is dependent on the density of the fabric, that is to say the number of warp and weft son per unit area. The porosity is also dependent on the presence of a coating intended to close more or less the pores of the fabric. The coating is in fact essential and is a significant part of the weight of the coated fabric and therefore the flying wing.

The coating is an essential element to confer the porosity required, it must be durable. The concept of durability can cover various criteria, for example UV stability and stability to hydrolysis and therefore more generally to atmospheric conditions and water. Hydrolysis stability should be considered as the preponderant factor in the long-term preservation of porosity properties.

Coating is also important for imparting good stiffness properties in the bias.

Currently, flying sails such as paragliders use a polyurethane (PU) polyester base as a coating material. These coatings have a relatively good resistance to UVs, they are however of limited durability with respect to stability to hydrolysis. The weight of the lightest coated fabrics thus produced is of the order of 45 g / m ² .

The higher weights, obtained by combining yarn density, choice of coating material, thickness and weight of the coating can produce tissues certainly stable to hydrolysis and having acceptable levels of porosity. However, they are too heavy to be used in the manufacture of high-performance flight sails.

FR 2 840 625 discloses a diagonally stabilized fabric formed of a rip-stop weave comprising warp yarns and weft yarns which are interwoven to present bands and stabilizing zones. This weave is coated with an aqueous mixture of polyurethane and silicone. The physicochemical characteristics of the polyurethane are not specified and the weight of the fabric is 45 g / m ² .

EP 0 305 888 discloses a textile material formed of a substrate impregnated with a water-repellent agent and coated with a polyurethane resin layer modified with a polysiloxane. This modified resin is prepared by reaction between the siloxane polymer and the basic components of polyurethane, isocyanate and diol (polytetramethylene glycol, polyether diol, open ring lactone diols, polycarbonate diol). The weight of the fabrics is greater than 40 g / m ² .

EP 2 184 399 discloses a textile material for paragliding, comprising a polyester fiber-based fabric coated with a urethane-silicone copolymer resin layer. This material is said to have a weight of between 21 and 100 g / m ² . The examples describe a weight equal to or greater than 45 g / m ² .

EP 0 552 374 describes a textile material that can be used for the manufacture of boat sails, paragliders or parachutes. This material comprises a polyester fabric which may optionally be coated with a resin which may be selected from polyurethane, silicone resin and polyvinyl chloride resin, without further specification of the nature of these resins or preferably. It is explicitly stated that this treatment is optional, the textile material does not need to be treated with a resin. The weight of the uncoated or coated fabric may be between 20 and 100, preferably between 30 and 50 g / m ² . The examples describe a polyethylene terephthalate fabric coated with a polyurethane resin for a weight of 25, 48 or 85 g / m ² .

JP 2000234272 describes a fabric for paragliding sail based on polyamide warp and weft threads that can be coated with a synthetic resin which can be an acrylic resin, a polyurethane resin, a silicone resin, a polyamide resin, a polyester resin, a resin polyimide, without further details on the physicochemical characteristics of the resin.

The prior art has not identified the essential criteria for optimizing both the weight of the coated fabric and its porosity, as well as its mechanical properties, to obtain fabrics for the manufacture of advanced flight sails. Thus, the prior art has not identified the coverage rate TC as being an essential criterion. He also did not identified the importance of the choice of physico-chemical characteristics of the coating resin. The prior art has not known how to combine these criteria to obtain fabrics having a coating weight of low value, especially less than or equal to 40 g / m ² . The prior art has also not been able to combine these different criteria to obtain optimum levels of air permeability for such a reduced weight.

An object of the invention is therefore to provide a coated fabric combining both properties of lightness, porosity and durability, including water stability.

Another object of the invention is to provide such a fabric which further has a suitable stiffness in the bias.

Yet another object of the present invention is to provide a method for obtaining such tissues.

Still other objects will appear on reading the description of the invention.

The invention particularly relates to a lightweight fabric coated according to claim 1. According to one embodiment, the polyurethane has a modulus at 100% elongation less than or equal to 4 MPa, preferably less than or equal to 3 MPa. This module can thus be between 1 and 5, 4 or 3 MPa.

le diamètre des filaments étant exprimé en cm.The TC is that of the fabric resulting from the weaving operation, and before any calendering operation or the like. The TC is calculated as follows: $$\mathrm{TC}{=\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; d}\text{'}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{chain}}{+\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; d}\text{'}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{weft}},$$

the diameter of the filaments being expressed in cm.

The TC values selected for the invention correspond to values conferring on the fabric a sufficiently closed configuration, then accentuated by calendering, making it possible, on the one hand, to limit the wear rate of the coating material in order to obtain 'a bass guitar porosity adapted to the field of use of the fabric, and consequently, on the other hand, to limit the final weight of the coated fabric. The dry weight of the coating material is greater than or equal to 10% by weight, especially between 10 and 30%, preferably between 12 and 30% by weight, more preferably between 15 and 25%. The dry weight ratio is the ratio by weight of coating (in particular PU and crosslinker) dry on the coated fabric, it is representative of the weight of dried / crosslinked coating present on the final fabric.

In one embodiment, the fabric of the present invention is characterized by bias in the bias. Chain bias is the 45 ° direction to the warp threads. The weft direction bias is the direction at 45 ° with respect to the weft threads. The elongation in% is measured under a force of 1.36 kg (3 pounds (Lbs)) applied in the bias. This elongation characterizes the stiffness of the fabric in the bias. The standard used is NF EN ISO 13934-1: specimens of width 50 mm and length 300 mm are produced. The edges of the dynamometer are 200 mm apart and the measurement is made at a speed of 100 mm / min.

In a particular embodiment, the fabric according to the invention has an elongation in the warp and weft direction under 1.36 kg (3 Lbs) less than or equal to 10%. This elongation can thus be between 1 and 10%, preferably between 3 and 10%, better still between 5 and 10%.

According to one embodiment, the light fabric has an air permeability less than or equal to 20 L / m ² / min at a pressure of 2000 Pa, as measured according to NFG 07111 standard (measurement surface of 100 cm ² ).

According to one embodiment, the light fabric comprises warp and / or weft yarns which have a dtex of between 11 and 44 dtex and a DPF (decitex per filament) of between 1 and 4.

According to one embodiment, the bare fabric has a weight of between 20 and 33 g / m ² , preferably between 24 and 28 g / m ² .

According to one embodiment, the coated fabric has a weight of between 25 and 40 g / m ² , preferably between 31 and 36 g / m ² .

According to one embodiment, the fabric comprises from 30 to 50 warp threads per cm and from 30 to 50 weft threads per cm.

According to one embodiment, the fabric comprises threads whose filaments have a DPF (decitex per filament) of between 1 and 3.

In one embodiment, the lightweight fabric of the present invention is obtained by coating an aqueous polyurethane dispersion. The coating may have any of the features mentioned below.

1. (a) on dispose d'un tissu présentant un taux de couverture TC compris entre 1,8 et 4, de préférence compris entre 2,6 et 3,2, TC étant calculé comme suit : $$\mathrm{TC}={\left(\mathrm{nombre\; de\; filaments}/\mathrm{cm}\times \mathrm{diamètre\; d}\prime \mathrm{1}\mathrm{filament}\right)}_{\mathrm{chaîne}}+{\left(\mathrm{nombre\; de\; filaments}/\mathrm{cm}\times \mathrm{diamètre\; d}\prime \mathrm{1}\mathrm{filament}\right)}_{\mathrm{trame}}$$
   
2. (b) on enduit une ou deux faces de ce tissu à l'aide d'un polyuréthane base polyéther ou polycarbonate ayant un module à 100% d'allongement inférieur ou égal à 5 MPa (mesuré selon la norme DIN 53504), avec un taux d'emport sec supérieur ou égal à 10 % en poids, de préférence compris entre 12 et 30 %, mieux entre 15 et 25 %,
3. (c) on chauffe le tissu jusqu'au séchage/réticulation de l'enduction,
4. (d) on récupère un tissu présentant un poids, enduction comprise, allant de 25 à 40 g/m².

The subject of the invention is also a process for producing a light coated fabric, in which:

1. (a) a fabric having a TC coverage ratio of between 1.8 and 4, preferably in the range of 2.6 to 3.2, wherein TC is calculated as follows: $$\mathrm{TC}={\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; d}\text{'}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{chain}}+{\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; d}\text{'}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{weft}}$$
   
2. (b) one or both sides of this fabric are coated with a polyether-based polyether or polycarbonate base having a modulus at 100% elongation of less than or equal to 5 MPa (measured according to DIN 53504), with a dry matter content greater than or equal to 10% by weight, preferably between 12 and 30%, better still between 15 and 25%,
3. (c) the fabric is heated to drying / crosslinking of the coating,
4. (d) recovering a fabric having a weight, including coating, ranging from 25 to 40 g / m ² .

According to one embodiment, the polyurethane has a modulus at 100% elongation less than or equal to 4 MPa, preferably less than or equal to 3 MPa. This module can thus be between 1 and 5, 4 or 3 MPa.

According to one embodiment, the fabric comprises warp and / or weft threads having a dtex of between 11 and 44 dtex and a DPF (decitex per filament) of between 1 and 4,

According to one embodiment, before coating in step (b), the fabric is calendered. The calendering crushes the fabric and spreads the yarns and the constituent filaments, which helps to close the pores of the fabric and reduce the porosity.

According to one embodiment, one calenders between a tool, cylinder or calender roll and a counter-platinum. The face of the fabric that has undergone the passage of the calendering tool, called the calender face, is smoothed with respect to the other face.

According to a modality, the coating is produced on this calender face. The adhesion of the polymer can be improved by first applying a treatment to this smooth surface. primer. It can be a physical treatment or a chemical treatment. This is for example a chemical treatment providing functional groups capable of reacting with groups of the polymer to form chemical bonds.

According to another embodiment, the coating is made on the other side, unsmoothed. It is understood that the rate of carriage varies according to the face concerned, this rate being higher on the unsmoothed face, which allows the skilled person to play on the amount and weight of the coating. We can also coat both sides.

According to another embodiment, one calendering between two tools, cylinders or calendering rollers. Both sides of the fabric are smoothed. One or both sides are then coated, with or without tacking treatment as described above.

The calendering is preferably carried out at a temperature of between 150 and 250 ° C, preferably between 180 and 210 ° C. The calendering is preferably carried out with a pressure of from 150 to 250 kg, preferably from 180 to 230 kg. The speed of rotation of the calender can be between 1 and 30 m / min, preferably between 10 and 20 m / min.

According to one embodiment, the fabric used in step (a) has a weight of between 20 and 33 g / m ² , preferably between 24 and 28 g / m ² .

According to one embodiment, the fabric resulting from step (c) has a weight of between 25 and 40 g / m ² , preferably between 31 and 36 g / m ² .

According to one embodiment, the fabric used comprises from 30 to 50 warp threads per cm and from 30 to 50 weft threads per cm.

According to one embodiment, the fabric used comprises threads whose filaments have a DPF (decitex per filament) of between 1 and 3.

In one embodiment, the lightweight fabric of the present invention is obtained by coating an aqueous polyurethane dispersion.

In one embodiment, the lightweight fabric of the present invention is obtained by coating a solvent-phase polyurethane dispersion.

A polyurethane has a steep portion (isocyanate) and a flexible portion (polyol). The ratio between these two components makes it possible to obtain a more or less stiff polymer. A polyol type polyether or polycarbonate is stable to hydrolysis and therefore durable.

The coating composition comprises a crosslinking agent, in particular an isocyanate or a melamine, or a mixture of both.

By isocyanate is meant both an isocyanate and a polyisocyanate, alone or in admixture with one or more other isocyanates and / or polyisocyanates. The term "isocyanate" should be understood herein to include the terms "isocyanate" and "polyisocyanate".

According to one embodiment, the proportion of dry crosslinker relative to the dry polyurethane is 5% or more than 5%, especially between 10 and 30%, by weight.

According to a preferred embodiment, the polyurethane is based on polyether.

In one embodiment, the polyether polyether base is linear or branched and comprises a polyol polyether portion and an isocyanate portion. In a particular embodiment, the isocyanate portion is preferably aliphatic, in fact the aromatic isocyanates have the disadvantage of yellowing over time.

In another embodiment, the polyurethane is based on polycarbonate.

In one embodiment, the polycarbonate base polycarbonate is linear or branched and has a polycarbonate polyol portion and an isocyanate portion. In a particular embodiment, the isocyanate portion is preferably aliphatic, in fact the aromatic isocyanates have the disadvantage of yellowing over time.

In one embodiment, the isocyanate crosslinking agent used is blocked (in particular masked isocyanate functions) in order to have a product having a longer pot life ("pot-life"), as is known per se. . In general, one skilled in the art is well acquainted with the field of polyurethanes and is able to propose coating compositions in accordance with the invention and in particular for producing a coating having the appropriate elongation modulus.

The coating step is carried out by the techniques conventionally used in the coating of textiles such as direct coating.

The term "direct coating" is understood to mean a coating by direct application using a doctor blade or a cylinder or by an air knife, coating by a scarf, at the Meyer bar (or Champion process).

In one embodiment, the method comprises after step c) one or more post-treatment stage (s) giving the fabric antifouling and / or water-repellent properties.
By anti-soiling treatment is meant treatment with anti-static and / or anti-tack products. The term "water-repellent treatment" means treatment with fluorinated resins with or without isocyanate extender. The water-repellent treatment is followed by a drying / crosslinking step.

In one embodiment, the post-treatment is applied by any method known to those skilled in the art and in particular by padding, coating, spraying or plasma treatment.

According to one embodiment, the polyurethane used is flexible and is therefore durable with mechanical stresses. It meets the following specifications: 1 to 5 MPa according to DIN 53504

In the aqueous phase embodiment, the polymer is finely dispersed in water in the form of micrometer beads. This dispersion is stable thanks to the addition of surfactants. During the process, the coating deposited on the fabric dries under the action of the heat of the furnaces (evaporation of the water) and the balls collect (coalescence). We then have a microporous film. As the temperature rises in the furnaces, the balls melt and form a continuous film.

The aqueous phase polyurethane has the intrinsic characteristics of the polymer and physicochemical characteristics related to its shaping. Thus, in one embodiment of the invention, the aqueous phase polyurethane is characterized by a modulus at 100% elongation less than 5 MPa. The aqueous phase polyurethane can also be characterized by a concentration of the dispersion of between 30 and 60%. Finally, the aqueous phase polyurethane of the present invention can be characterized by a viscosity of less than 10,000 Pa.s at 23 ° C. (DIN EN ISO / A3).

In the solvent phase embodiment, the polymer is dissolved in the medium and the coalescence phase is avoided. The film naturally forms during the evaporation of the solvent.

In one embodiment of the invention, the solvent is selected from the group consisting of aromatic solvents, alcohols, ketones, esters, dimethylformamide and n-methylpyrrolidone.

In a particular embodiment, the solvent is selected from the group consisting of toluene, xylene, isopropanol, butanol, 1-methoxypropan-2-ol, methyl ethyl ketone, acetone, butanone, and the like. ethyl acetate, dimethylformamide and n-methylpyrrolidone.

In one embodiment, the polyurethane solvent phase may be characterized by its concentration of between 20 and 50%.

In one embodiment, the polyurethane solvent phase may be characterized by a viscosity of less than 100,000 Pa.s at 23 ° C. (DIN EN ISO / A3 standard).

The coating composition of the fabric of the present invention, an aqueous polymer dispersion, may further comprise additives.

Said additives may be any additive commonly used in fabric coating compositions. They are especially chosen from the group consisting of viscosity modifiers, UV stabilizers, dyes, dispersants and surfactants. In one embodiment, the coating comprises an anti-UV agent.
The fabric of the present invention may be any tissue known to those skilled in the art requiring coating. In particular, the fabric of the present invention consists of son of synthetic or artificial material. It may be in particular polyamide, polyester or viscose.

The invention has the advantage of using fine son and having a high number of constituent filaments. In addition to providing lightness to the fabric, it allows, at the time of coating, and especially if the latter is preceded by a step of spreading the fibers by calendering, substantially reduce the porosity of the fabric before coating, this which makes it possible to reduce the polymer load and therefore the relative weight of the coating, and in the end it also makes it possible to reduce the final weight of the fabric, while having good properties in terms of porosity and durability.

In one embodiment of the invention, the fabric is made of warp yarns and weft yarns having different mechanical characteristics.

The invention also relates to a lightweight fabric obtainable by the implementation of the method according to the invention.

This type of fabric can be advantageously used as a flying veil, especially paragliding, which requires mechanical strengths, resistance to weather conditions and significant resistance over time.

• porosité après lavage: elle doit rester de préférence inférieure ou égale à 70 L/m²/min sous 2000 Pa ;
• porosité après sollicitation mécanique : elle doit rester de préférence inférieure à 40, de préférence à 20 L/m²/min sous 2000 Pa ;
• porosité après hydrolyse et sollicitation mécanique : elle doit rester de préférence inférieure ou égale à 70 L/m²/min sous 2000 Pa.

The fabric of the invention advantageously has a high durability, especially a high water stability. This stability can be assessed by different accelerated aging methods, described in the examples section:

• porosity after washing: it should preferably remain less than or equal to 70 L / m ² / min under 2000 Pa;
• porosity after mechanical stress: it must remain preferably less than 40, preferably 20 L / m ² / min under 2000 Pa;
• porosity after hydrolysis and mechanical stress: it must remain preferably less than or equal to 70 L / m ² / min under 2000 Pa.

The fabrics according to the invention can find application in all applications where the weight gain, durability, especially water stability, and porosity has an advantage.

The invention thus relates to an article such as a paraglider sail, comprising or fabricated from a fabric according to the invention.

The invention will now be described by means of examples corresponding to the preferred embodiments, these being given by way of illustration without being limiting.

Example 1

• Chain yarn: 22 dtex with a DPF of 1.7
• Weft yarn: 33 dtex with a DPF of 1.1
• Material of the yarns: polyamide, polyester or viscose
• Contexture: 43.7 threads / cm warp and 47.6 threads / cm weft

Coverage rate 2.8

The calendering is carried out at a temperature of between 180 and 210 ° C., at a pressure of between 180 and 230 kg, and at a speed of between 10 and 20 m / min.

Coating formulation:

• PU base polyéther, aliphatique, module 100% allongements 2 MPa : 70% (sec : 31,5 %)
• Durcisseur à base d'isocyanate : 15% (sec : 6,8 %)
• Additifs : 10%
• Epaississant : 5%

(sauf indication contraire, les % sont en poids)

• PU polyether base, aliphatic, modulus 100% elongations 2 MPa: 70% (dry: 31.5%)
• Hardening agent based on isocyanate: 15% (dry: 6.8%)
• Additives: 10%
• Thickener: 5%

(unless otherwise indicated,% is by weight)

The coating is performed by squeegee, and is followed by a drying step (at a temperature between 90 and 120 ° C), then a crosslinking step (temperature between 140 and 210 ° C). The speed is between 10 and 30 m / min.

• Formulation: Résine fluorée 10%
• Eau 89%
• Mouillant 1%

The fabric then undergoes a water repellent post-treatment:

• Formulation: Fluorinated resin 10%
• Water 89%
• Wetting 1%

This post treatment is applied by padding, then drying (temperature between 90 and 120 ° C), followed by crosslinking (temperature between 140-210 °), speed between 10 and 30 m / min.

Example 2

• Chain yarn: 22 dtex with a DPF of 1.7
• Weft yarn: 33 dtex with a DPF of 1.1
• Material of the yarns: polyamide
• Contexture: 43.7 threads / cm warp and 47.6 threads / cm weft
• Fabric weight: 27.7 g / m ²
• Coverage rate 2.8

• Formulation d'enduction : (5,8 g/m²)
• Evotop U80ES 70 % (PU base polyéther, aliphatique, module 100% allongements 2 MPa)
• Rottal 444 15% (durcisseur isocyanate)
• Additifs 10% (anti-UV, agent mouillant, biocide)
• Rotta 1227 5% (épaississant)

The calendering is carried out at a temperature of between 180 and 210 ° C., at a pressure of between 180 and 230 kg, and at a speed of between 10 and 20 m / min.

• Coating formulation: (5.8 g / m ² )
• Evotop U80ES 70% (PU polyether base, aliphatic, modulus 100% elongations 2 MPa)
• Rottal 444 15% (isocyanate hardener)
• 10% additives (anti-UV, wetting agent, biocide)
• Rotta 1227 5% (thickener)

The coating is performed by squeegee and then a drying step (temperature between 90 and 120 ° C) / crosslinking (temperature between 140-210 ° C) is performed. The speed is between 10 and 30 m / min.

• Formulation : Thobotex SLF 10% (résine fluorée)
• Eau 89%
• Mouillant 1%

The fabric then undergoes a water repellent treatment (0.5 g / m ² ):

• Formulation: Thobotex SLF 10% (fluororesin)
• Water 89%
• Wetting 1%

This post treatment is applied by padding, followed by drying (temperature between 90 and 120 ° C) / crosslinking (temperature between 140-210 ° C), speed between 10 and 30 m / min.

The fabric obtained has a weight of 34 g / m ² (weight of the fabric before coating 27.7 g / m ² , the contribution of the water-repellent treatment to the final weight of the fabric is approximately 0.5 g / m ² )

The elongation in% is measured under a force of 3 pounds (Lbs) applied in the bias. This elongation characterizes the stiffness of the fabric in the bias. The standard used is NF EN ISO 13934-1. Specimens of width 50 mm and length 300 mm are produced. The edges of the dynamometer are 200 mm apart and the measurement is made at a speed of 100 mm / min.

Lengthening in the warp direction at 1.36 kg (3 Lbs): 6.0% Elongation in the weft direction bias under 1.36 kg (3 Lbs): 6.3% We also measure the aging of the fabric by different methods .

The porosity of the fabric is measured after 4 cycles of 1 hour of washing with water at 30 ° C. Ideally the porosity after treatment should be less than 70 L / m ² / min.

The porosity is also measured after mechanical stressing. To carry out this measurement, the fabric fixed on a mill-type assembly is floated at high speed (4-blade assembly, the fabric being fixed at the end of one of the blades). Ideally the porosity after 1:30 of treatment should be less than 40 L / m ² / min, preferably less than 20 L / m ² / min.

The porosity of the fabric after hydrolysis is also measured. To do this we place the fabric for 4 hours in a pressure cooker pressure cooker with water at temperature and operating pressure. 1 hour of float treatment is then applied as determined above and the porosity of the final fabric is measured. Ideally the porosity after treatment should be less than 70 L / m ² / min.

Results:

• Porosity at new 1 L / m ² / min under 2000 Pa.
• Porosity after 4 washes 30 ° C: 52 L / m ² / min under 2000 Pa.
• Porosity after hydrolysis plus float: 9 L / m ² / min under 2000 Pa.
• Porosity after 90 min of floats: between 10 and 14 L / m ² / min under 2000 Pa.

Claims (17)

1. A light fabric made from continuous warp yarns and weft yarns, this fabric being coated on one or both surfaces thereof with a polyurethane, characterized by the combination of the following characteristics:

   - the bare fabric has a coverage rate TC comprised between 1.8 and 4, preferably comprised between 2.6 and 3.2, TC being calculated as follows: $$\mathrm{TC}={\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; of\; one\; filament}\right)}_{\mathrm{warp}}+{\left(\mathrm{number\; of\; filaments}\times \mathrm{diameter\; of}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{weft}},$$

   

   the diameter of filaments being expressed in cm,

   - the polyurethane has a polyether or polycarbonate base having a tensile stress at 100% elongation of less than or equal to 5 MPa (measured according to standard DIN 53504), its dry impregnation rate is greater than or equal to 10% by weight, preferably comprised between 12 and 30%, better still between 15 and 25%,

   - the fabric has a weight, including the coating, of 25 to 40 g/m².
2. The light fabric according to claim 1, characterized in that the polyurethane has an elongation tensile stress of less than or equal to 4 MPa, preferably less than or equal to 3 MPa.
3. The light fabric according to claim 1 or 2, having an air permeability of less than or equal to 20 L/m²/min under 2000 Pa, as measured according to standard NFG 07111 over a measuring surface of 100 cm².
4. The light fabric according to any one of the preceding claims, characterized in that it has an elongation in the warp and weft direction bias under 1.36 kg (3 lbs.) of less than 10%, according to standard NF EN ISO 13934-1.
5. The light fabric according to the preceding claim, characterized in that it has an elongation in the warp and weft direction bias under 1.36 kg (3 lbs.) comprised between 1 and 10 %, preferably comprised between 3 and 10%, better still between 5 and 10%.
6. The light fabric according to any one of the preceding claims, characterized in that the warp and/or weft yarns have a dtex comprised between 11 and 44 dtex and a DPF (decitex per filament) comprised between 1 and 4.
7. The light fabric according to any one of the preceding claims, characterized in that the weight of the bare fabric is comprised between 20 and 33 g/m², preferably between 24 and 28 g/m².
8. The light fabric according to any one of the preceding claims, characterized in that the weight of the coated fabric is comprised between 31 and 36 g/m².
9. The light fabric according to any one of the preceding claims, characterized in that the fabric comprises 30 to 50 warp yarns per cm and 30 to 50 weft yarns per cm.
10. The light fabric according to any one of the preceding claims, characterized in that the polyurethane coating comprise an isocyanate and/or melamine crosslinking agent, the proportion of dry crosslinking agent relative to the dry polyurethane is 5 wt % or more than 5 wt %, in particular between 10 and 30 wt %.
11. The light fabric according to any one of the preceding claims, characterized in that it also comprises an antifouling and/or water repellant treatment.
12. A method for manufacturing a coated light fabric, in particular a fabric according to any one of the preceding claims, in which:

    (a) a fabric having a coverage rate TC comprised between 1.8 and 4, preferably comprised between 2.6 and 3.2, is used, TC being calculated as follows: $$\mathrm{TC}={\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; of}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{warp}}+{\left(\mathrm{number\; of\; filaments}/\mathrm{cm}\times \mathrm{diameter\; of}\mathrm{1}\mathrm{filament}\right)}_{\mathrm{weft}},$$

    

    the diameter of filaments being expressed in cm,

    (b) one or two surfaces of that fabric are coated using a polyether- or polycarbonate-based polyurethane having a tensile stress at 100% elongation of less than or equal to 5 MPa (measured according to standard DIN 53504), with a dry impregnation rate greater than or equal to 10 wt %, preferably comprised between 12 and 30 wt %, better still between 15 and 25 wt %,

    (c) the fabric is heated until the coating is dried/crosslinked,

    (d) a fabric is recovered having a weight, including coating, of 25 to 40 g/m².
13. The method according to claim 12, characterized in that, before coating in step (b), the fabric is calendered.
14. The method according to claim 13, characterized in that the coating is done on the calendering surface.
15. The method according to claim 13, characterized in that a finishing treatment is applied on the surface of the fabric, before coating of that surface, said finishing treatment increasing the catching of the coating on the fabric.
16. The method according to any one of claims 13 to 15, characterized in that it comprises a coating on the surface opposite the calendering surface.
17. The method according to any one of claims 13 to 16, characterized in that it comprises post-treatment step(s) giving the fabric antifouling and/or water repellant properties.