WO2022073902A1

WO2022073902A1 - Coated lightweight fabric, in particular for a gliding wing

Info

Publication number: WO2022073902A1
Application number: PCT/EP2021/077235
Authority: WO
Inventors: Stéphane VERAN
Original assignee: Porcher Industries
Priority date: 2020-10-05
Filing date: 2021-10-04
Publication date: 2022-04-14
Also published as: FR3114821A1; FR3114821B1; JP2023544393A; EP4225979A1; CN116324082A; TW202223199A; KR20230084233A

Abstract

Fabric for a gliding wing, in particular for paragliding, formed from warp threads and continuous weft threads and coated on one or both faces with a polyurethane (PU), the bare fabric having a coverage rate TC of between 1.8 and 4, characterized in that the yarns are made of polyethylene terephthalate (PET), in that the fabric has a density of between 30 and 50 yarns/cm in warp and weft, in that the polyurethane is a polyether-, polyester- or polycarbonate-based cross-linked PU, and in that said PU is derived from the crosslinking (1) of a one-component polyurethane having a modulus at 100% elongation of 5 MPa or less, according to standard DIN 53504, carried out in an organic solvent phase, (2) by a cross-linking agent, with a proportion of dry cross-linking agent relative to dry elastomer of between approximately 5% and approximately 30% by weight.

Description

TITLE: Lightweight coated fabric, especially for flying wings

The present invention relates to a lightweight fabric for a paragliding-type flight wing and to a process for manufacturing this fabric.

In the field of flight wings, for example paragliders, 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 an increase in weight. Indeed, porosity is dependent on the density of the fabric, i.e. the number of warp and weft threads per unit area. The porosity is also dependent on the presence of a coating intended to more or less close the pores of the fabric. The coating is actually essential and constitutes a significant part of the weight of the coated fabric and therefore of the flight wing. The coating is also important to impart the right stiffness properties to the bias.

The coating being an essential element to confer the required porosity, it must be durable. The notion of durability can cover various criteria, for example stability to UVs and stability to hydrolysis and therefore more generally to atmospheric conditions and to water. The stability to hydrolysis must be considered as the preponderant factor in the preservation over time of the porosity properties. Currently, flight wings such as paragliders are made of polyamide and use a polyester-based or polycarbonate-based polyurethane (PU) as coating material. These coatings have a relatively good resistance to UVs, they are on the other hand of limited durability as regards the stability to hydrolysis. The weight of the fabrics is generally between 26 and 40 g/m ² .

The nature of the warp and weft yarns also has an influence on the properties and durability of sails. In practice, the sails are made of polyamide 6.6, which is, however, a hydrophilic polymer which gives the fiber a propensity to absorb water. A paraglider made from a polyamide 6.6 fabric then tends to become heavy and age prematurely under the combined action of UV and hydrolysis. The absorbed water degrades the mechanical performance of the polyamide and the coating.

It is therefore known to produce coated fabrics having adequate porosity when the coated fabric is new. However, in the practice of paragliding, the known coated fabrics see this property deteriorates in a humid environment, which poses the problem of the longevity of the sails made of it.

An object of the invention is to remedy these drawbacks and to propose a coated fabric combining both properties of lightness and mechanical performance, and properties of porosity, of less sensitivity, or even insensitivity, to the taking of water, and durability, which is usable in use in a flight wing, in particular a paraglider, safe and durable.

Another object of the invention is to provide such a fabric which retains the best mechanical properties necessary for a high-level paragliding wing, with in particular an appropriate stiffness in the bias and a high resistance to tearing.

Another objective is to be able to print the fabric by sublimation, and therefore to propose new coated fabrics capable of being printed in this way.

Still other objectives will appear on reading the description of the invention which follows.

These and other objectives are achieved with a lightweight fabric formed from poly(ethylene terephthalate) (PET) continuous warp and weft yarns and coated on one or both sides with a polyurethane (PU) , preferably on one side only. The fabric preferably has a density of between 30 and 50 threads/cm in warp and in weft. The polyurethane is advantageously a crosslinked PU based on polyether, polyester or polycarbonate. According to another preferred characteristic, the PU is obtained from a single-component polyurethane elastomer. This elastomer is formed from polyol segments (polyether, polyester or polycarbonate), isocyanate segments, and a chain extender or a hydroxylated crosslinking agent, as is known per se. An important preferred characteristic is that the elastomer has a modulus at 100% elongation less than or equal to approximately 5 MPa, in particular between 1 and 4 MPa, in particular between 1 and 3 MPa, for example approximately 2 MPa, according to the DIN 53504 standard. Another important preferred characteristic is that the elastomer is mixed with a crosslinker (not to be confused with the crosslinking agent used to form the elastomer). In particular, the proportion of dry crosslinking agent relative to the dry elastomer of between approximately 5% and approximately 30% by weight, in particular between approximately 7 and approximately 20% by weight, in particular between approximately 8 and approximately 18% by weight (by example about 8 and about 16% by weight). The crosslinker comprises in particular an isocyanate, melamine, or a mixture of isocyanate and melamine. This crosslinker makes it possible in particular to block all or part of the reactive functions (in particular NCO and alcohol) remaining on the elastomer, to create additional bonds or crosslinks, and to obtain the crosslinked PU forming the coating of the fabric. The fabric according to the invention is intended for, or capable of forming, flight wings, in particular paragliding wings.

The fabric advantageously has a TC coverage rate of between 1.8 and 4, in particular between 2.6 and 3.2. The TC (coverage rate) is that of the PET fabric resulting from the weaving operation, and before any eventual calendering or similar operation. The TC is calculated as follows: TC = (number of filaments/cm x diameter of 1 filament in cm) _Chain + (number of filaments/cm x diameter of 1 filament in cm) _thread . The TC values retained for the invention correspond to values giving the fabric a sufficiently closed configuration, then accentuated by a possible and advantageous calendering, making it possible, on the one hand, to limit the rate of carriage of the coating material for the obtaining a low 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 invention relates in particular to a fabric for a flying wing, in particular a paraglider, formed of continuous warp and weft threads and coated on one or both of its faces with a polyurethane (PU), the bare fabric having a coverage rate TC between 1.8 and 4, characterized in that the threads are made of poly(ethylene terephthalate) (PET), in that the fabric has a density of between 30 and 50 threads/cm in warp and weft, in that the polyurethane is a crosslinked PU based on polyether, polyester or polycarbonate, and in that this PU is derived from the crosslinking (1) of a single-component polyurethane elastomer having a modulus at 100% elongation less than or equal to 5 MPa, in particular between 1 and 4 MPa, in particular between 1 and 3 MPa, according to standard DIN 53504, implemented in the organic solvent phase (in particular dissolved in a solvent), (2) by a crosslinking agent, at a rate of a proportion of dry crosslinker relative to the dry elastomer of between about 5% and about 30% by weight oids, in particular between about 7 and about 20% by weight, in particular between about 8 and about 18% by weight.

The fabrics according to the invention have a surprising capacity to retain their initial porosity (when new), or to experience only a slight increase in this porosity, during aging and therefore the use of the fabric. At the same time, these fabrics also have the advantage of only undergoing a reduced increase in their water absorption during their aging or use. It has therefore been found the formula making it possible to propose a fabric for a flight wing, in particular a paraglider, having excellent properties of porosity, of less sensitivity, or even of nsensitivity, to water intake, over time and use, making it possible to durably preserve the properties of lightness and mechanical performance allowing efficient and safe use of the sail.

The fabric may have a weight, coating included, ranging from 25 to 42 g/m ² , in particular from 27 to 40 g/m ² .

According to one embodiment, the dry take-up rate of the coating material is greater than or equal to 10% by weight, in particular between 10 and 30%, preferably between 12 and 30% by weight, better still between 15 and 25%. The dry take-up rate is the ratio by weight of coating (in particular cross-linked PU) dry on the coated fabric, it is representative of the weight of dried/cross-linked coating present on the final fabric.

PET is made up of repeating units of ethylene terephthalate; however, within the scope of the invention are variants comprising a minor amount of other units, for example less than 10% molar, in particular less than 5% molar of other units, per molecular chain of the polyester (the comonomers to form such other units include, for example, isophthalic acid, naphthalene dicarboxylic acids, adipic acid, hydroxybenzoic acids, diethylene glycol, propylene glycol, trimellitic acid and pentaerythritol).

Polyester yarns are multifilament. They are formed of multiple continuous filaments. According to one embodiment, the fabric comprises warp yarns and weft yarns which have a dtex count of between 11 and 44 dtex, for example between 11 and 33 dtex, with in particular a DPF (decitex per filament) comprised between 1 and 4, preferably between 1.3 and 3.5.

In one embodiment, the warp yarns and the weft yarns are of the same title and of the same DPF.

In another embodiment, the warp yarns and the weft yarns have different counts, the count of the threads in one direction being strictly greater than the count of the threads in the other direction. For example, the count of the yarns in one direction is between 30 and 44 dtex, in particular between 30 and 36 dtex, while the count of the yarns in the other direction is between between 11 and 33 dtex, in particular between 19 and 26 dtex, the count of the threads in the first direction being strictly greater than the count of the threads in the other direction. According to one modality, the top title yarns are in the weft direction. According to another modality, the yarns of higher title are in warp direction.

In another embodiment, it is possible to provide variegated titles in the same direction, warp or weft, or in both directions, warp and weft. In this case, in warp and/or weft, there are at least two types of threads with different counts.

The tenacity (or tensile strength) of the PET yarns is in particular greater than or equal to 6 cN/dtex, in particular between 6 and 7 cN/dtex. Their elongation at break is in particular greater than or equal to 20%, in particular between 20 and 30%. Tenacity and elongation at break are measured according to DIN EN ISO 2062.

PET fibers or yarns having these characteristics are commercially accessible and/or can be produced to order.

The polyester yarns optionally contain one or more additives, for example a stabilizer and/or an antistatic agent.

In one embodiment, the fabric of the present invention is characterized by stiffness in the bias. The bias is said to be in the warp direction when it is measured in the direction at 45° in relation to the warp threads. The bias is said to be in the weft direction when it is measured in the 45° direction with respect to the weft threads. The elongation in % is measured under a force of 3 lbs (Lbs, or 1.36 kg) 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 50 mm wide and 300 mm long are produced. The jaws of the dynamometer are separated by 200 mm and the measurement is carried out at a speed of 100 mm/min.

In particular, the coated fabric according to the invention has an elongation in the bias warp and weft direction under 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 lightweight fabric has an air permeability of less than or equal to 20 L/m ² /min under a pressure of 2000 Pa, as measured according to standard NFG 0711 1 (measurement surface of 100 cm ² ). According to one embodiment, the PET fabric used is a calendered fabric, which means that it has undergone calendering before its coating with PU. Calendering crushes the fabric and spreads the yarns as well as the constituent filaments, which helps to close the pores of the fabric and reduce its porosity.

The fabric of the present invention is obtained by coating polyurethane in solvent phase. The coating may have any of the characteristics mentioned below. First, the fabric can be coated on one or two sides, preferably it is coated on one side.

A polyurethane has a stiff part (isocyanate) and a soft part (polyol). A person skilled in the art knows how to find the compromise between the isocyanate/polyol ratio and the nature of the components to obtain the elastomer with the desired stiffness, characterized by the modulus at 100% elongation. Preferably, the elastomer used in the coating is single-component, the isocyanate having reacted with the polyol, then with the chain extender or the crosslinking agent, forming an elastomer generally still containing reactive functions of the NCO and alcohol type. Those skilled in the art may refer to the literature on the production of copolymers or elastomers obtained from isocyanate, polyol and chain extenders or crosslinking agent, in particular to the Thesis in Polymer Materials and Composites of Ségolène Hibon, INSA Lyon, France, 2006.

The coating composition is completed with a crosslinker, in particular an isocyanate or a melamine, or even a mixture of the two. By isocyanate is meant both an isocyanate and a polyisocyanate, alone or mixed with one or more other isocyanates and/or polyisocyanates. The term "isocyanate" should be understood here as combining the terms "isocyanate" and "polyisocyanate". Polyisocyanates are preferred. As regards melamine, it may in particular be melamine itself (1,3, 5-triazine-2,4,6-triamine) or a melamine-containing compound or resin, for example a melamine-formaldehyde resin.

According to one embodiment, the proportion of dry crosslinking agent relative to the dry elastomer is between approximately 5% and approximately 30% by weight, in particular between approximately 7 and approximately 20% by weight, in particular between approximately 8 and approximately 18 % in weight. According to one embodiment, the polyurethane (and the starting elastomer) is polyether-based. In particular, the polyether-based polyurethane is linear or branched and comprises a polyol part of the polyether type and an isocyanate part.

According to another embodiment, the polyurethane (and the starting elastomer) is polyester-based. In particular, the polyester-based polyurethane is linear or branched and comprises a polyol part of the polyester type and an isocyanate part.

According to another embodiment, the polyurethane (and the starting elastomer) is polycarbonate-based. In particular, the polycarbonate-based polyurethane is linear or branched and comprises a polyol part of the polycarbonate type and an isocyanate part.

As regards the elastomer and the crosslinker, the isocyanate part is preferably aliphatic, in fact aromatic isocyanates have the particular disadvantage of yellowing over time, which makes them less preferred, even if they can be used .

In one embodiment, the lightweight fabric of the present invention is obtained by coating with polyurethane in the solvent phase. This method of producing a coated fabric from the polyester fabric is another object of the invention. The coating may have any of the characteristics mentioned below.

The coating step is carried out by techniques conventionally used in the coating of textiles, such as direct coating. “Direct coating” means coating by direct application, for example using a doctor blade, cylinder, air knife, scarf, Meyer bar (or Champion process).

Another object of the invention is the use of a PU elastomer or a cross-linked PU coating as defined here, for the coating of a high tenacity PET fabric as defined here. This coating is in particular intended to give it the property or properties described here, in particular an elongation in the bias as described here; and/or very low water absorption when new and after aging or use as described herein; and/or no or very little increase in porosity between new coated fabric and coated fabric after aging or use as described herein. This use can result in the manufacturing process which follows and which is another object of the invention.

The process for manufacturing the coated fabric comprises in particular the following steps: (a) a polyester fabric according to the invention is available; preferably, this fabric is calendered;

(b) one or two faces of this fabric are coated with a solvent-based PU according to the invention, preferably from a single-component elastomer dissolved in the solvent and mixed with the crosslinker, as described here, with a coating rate in accordance with the invention;

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

(d) a coated fabric according to the invention is obtained;

(e) optionally, the fabric is printed, for example by sublimation, on one or both sides.

The subject of the invention is in particular a process for manufacturing the coated fabric in which: a fabric made of poly(ethylene terephthalate) (PET) having a density of between 30 and 50 threads/cm, in warp and in weft; one or two faces of this fabric are coated with a mixture of single-component polyurethane elastomer having a modulus at 100% of elongation less than or equal to approximately 5 MPa, in particular between 1 and 4 MPa, in particular between 1 and 3 MPa, according to standard DIN 53504, of solvent for the elastomer and of a crosslinker, at the rate of a proportion of dry crosslinker relative to the dry elastomer of between approximately 5% and approximately 30% by weight, in particular between about 7 and about 20% by weight, in particular between about 8 and about 18% by weight; the fabric is heated until the coating dries and reticulates,

- A coated fabric is obtained;

- Optionally, the fabric is printed, for example by sublimation, on one or both sides.

This process aims to manufacture a fabric as described above and consequently, the characteristics of the elements entering into the composition of the fabric are applicable to the process, to the choice of these elements for their implementation in the process, without it it is necessary to repeat them in what follows.

The PET fabric can advantageously undergo calendering before coating.

According to one embodiment, the PET fabric is calendered before coating between a calendering tool, cylinder or roller and a counter-plate. The side of the fabric which undergoes the passage of the calendering tool, called the calendering side, is smoothed with respect to the other side. According to one modality, the coating is carried out on this calendering face. The adhesion of the polymer can be improved by first applying a primer treatment to this smooth face. 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 modality, the coating is carried out on the other side, not smoothed. It is understood that the take-up rate varies according to the face concerned, this rate being higher on the unsmoothed face, which allows the person skilled in the art to play on the quantity and the weight of the coating. You can also coat both sides.

According to another embodiment, the PET fabric is calendered before coating between two calendering tools, cylinders or rollers. Both sides of the fabric are smoothed. One or both sides are then coated, with or without adhesion treatment as described above.

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

The lightweight fabric of the present invention is obtained by coating with polyurethane in the solvent phase. The coating may have any of the characteristics mentioned below.

PU has a modulus at 100% elongation of less than or equal to approximately 5 MPa, in particular between 1 and 4 MPa, in particular between 1 and 3 MPa, according to standard DIN 53504. It is dissolved in an organic solvent . The polymer is dissolved in the medium. The PU crosslinker is added to this solution. In particular, the proportion of dry crosslinking agent relative to the dry polyurethane is between approximately 5% and approximately 30% by weight, in particular between approximately 7 and approximately 20% by weight, in particular between approximately 8 and approximately 18% by weight. The fabric of the present invention is obtained by coating polyurethane dissolved in a solvent. In particular, the coating contains the single-component elastomer (formed in particular from the isocyanate, the polyol and the chain extender or the crosslinking agent), in solution in the solvent. The film forms naturally during the evaporation of the solvent. The solvent is an organic solvent and can in particular be chosen from the group consisting of aromatic solvents, alcohols, ketones, esters, dimethylformamide and n-methylpyrolidone. In a particular embodiment, the solvent is chosen from the group consisting of toluene, xylene, isopropanol, butanol, 1-methoxypropan-2-ol, methyl ethyl ketone, acetone, butanone, ethyl acetate, dimethylformamide, n-methylpyrrolidone, and a mixture of at least two of them. For example, a mixture of toluene and isopropanol.

In one embodiment, the solvent-phase polyurethane can be characterized by its concentration of between 20 and 50% by weight of uncrosslinked PU, in particular single-component elastomer, relative to the PU and solvent mixture. In one embodiment, this solvent-phase polyurethane, in particular the elastomer in solution in the solvent, can be characterized by a viscosity of less than 100,000 mPa.s at 23° C., preferably between 5,000 and 60,000 mPa.s at 23°C (DIN EN ISO/A3 standard).

In particular, the drying and crosslinking step first comprises drying, for example at a temperature of between approximately 90 and approximately 120° C., then cross-linking at a temperature of between approximately 140 and approximately 210° C.

The fabric coating composition of the present invention may further comprise additives. Said additives can be any additive commonly used in fabric coating compositions. They are chosen in particular from the group consisting of viscosity modifiers, UV stabilizers, colorants, dispersants and surfactants. According to one embodiment, the coating comprises an anti-UV agent.

In one embodiment, the method comprises, after drying and crosslinking, one or more post-treatment step(s) giving the fabric anti-soiling and/or water-repellent properties. By anti-fouling treatment is meant a treatment using anti-static and/or anti-tack products. By water-repellent treatment is meant a treatment using fluorinated resins with or without crosslinking of the fluorinated resin, for example unisocyanate. The water-repellent treatment is followed by a drying/cross-linking step. In one embodiment, the post-processing is applied by any known method of skilled in the art and in particular by padding, coating, spraying or plasma treatment.

The invention has the advantage of using fine yarns and comprising a high number of constituent filaments. In addition to bringing lightness to the fabric, this allows, at the time of coating, and in particular if the latter is preceded by a step of spreading the fibers by calendering, to significantly 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 ultimately this also makes it possible to reduce the final weight of the fabric, while having good properties in terms of porosity and durability.

The coated fabrics described here prove capable of being printed by the so-called sublimation technique. According to one aspect of the invention, this coated fabric is colored, printed or decorated by a sublimation technique. This can in particular be implemented by printing a pattern on a support (transfer support) with one or more sublimable dyes at high temperature. The support is then applied in contact with the coated fabric, then hot calendered, for example at approximately 200° C. and under pressure. The dyes pass into the gas phase and are transferred to the coating, and/or to the surface and/or to the fiber. PET polyester remains stable at this temperature.

The invention also relates to a lightweight fabric obtained or capable of being obtained by implementing the method according to the invention.

The subject of the invention is thus an article such as a flight wing, in particular for a paraglider, comprising or made from a fabric according to the invention. It can carry a pattern printed by sublimation.

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

- porosity after hydrolysis and mechanical stress: it must preferably remain less than or equal to 20 L/m ² /min, in particular less than or equal to 12 L/m ² /min, in particular less than or equal to 10 L/m ² / min according to standard NFG071 1 1; and/or a water absorption according to the Tappi 441 om-90 standard of less than or equal to 1%, in particular less than or equal to 0.9%, for example less than or equal to 0.5%, both new and after ageing. The invention will now be described with the aid of examples corresponding to the preferred embodiments, these being given by way of illustration without however being limiting.

Example :

This example compares the impact of a polyurethane coating on one side of a classic PU coated polyamide 6.6 fabric (Control) and a high tenacity polyethylene terephthalate (PET) fabric coated on one side with a PU according to the invention.

PA6.6 is a classic polyamide fabric in the field of paragliding, however with a PU coating obtained from PU elastomer with a modulus at 100% elongation of 2 MPa and isocyanate + melamine formaldehyde crosslinker. The proportion of dry crosslinker to dry elastomer is 8.4%. The PU is processed in a 50/50 mixture of toluene and isopropanol.

In example 1, the PET has a PU coating obtained from PU elastomer having a modulus at 100% elongation of 2 MPa and isocyanate + melamine formaldehyde crosslinker. The proportion of dry crosslinker to dry elastomer is 8.4%. The PU is processed in a 50/50 mixture of toluene and isopropanol.

In example 2, the PET has a PU coating obtained from PU elastomer having a modulus at 100% elongation of 2 MPa and isocyanate + melamine formaldehyde crosslinker. The proportion of dry crosslinker to dry elastomer is 15.4%. The PU is processed in a 50/50 mixture of toluene and isopropanol.

In both cases, the PU is a one-component PU based on aliphatic polycarbonate.

The tenacity of PET is 6.25 cN/dtex. The elongation at break is 24.6%.

The coating is carried out using a doctor blade, and is followed by drying at 100°C, then crosslinking at 180°C. The speed is 27 m/min.

[Table 1]

Methods and measures employed in the application (characteristics of the invention and examples):

NF EN ISO 2062 - Determination of breaking strength and elongation at break of individual yarns using a constant rate of elongation tester, using Method A of the standard.

Breaking force (unit centiNewton - cN): maximum force developed to break the sample during a tensile test conducted until failure

Elongation at break (%): increase in the length of the sample measured when it breaks

Tenacity (cN/tex): quotient of the breaking force expressed in cN by the linear mass of the yarn expressed in dtex (1 tex = 1 g per 1000 m of yarn length).

The test makes it possible to measure the force and the elongation at break of the sample, characteristic quantities of the yarn.

The wire is placed between two clamps, 500 mm apart. The device (Dynamometer) then moves the grippers away from each other at a constant displacement speed of 500 mm/min and measures the force applied continuously. The force required to break the thread is measured as well as the increase in length of the thread upon breaking. Mean breaking force and mean elongation at break are the two data characterized by this test. Tenacity is calculated from the breaking force related to the linear mass. The 100% elongation modulus of the one-component polyurethane elastomer is measured according to DIN 53504. The modulus is defined in 3.4 of the “Spannungswerte” standard. The measurement is carried out on dumbbell-shaped specimens (Schulterstab) of type S2, with however a bar length Is of 55 mm and a thickness of 200 μm. The equipment used is a dynamometer. The dumbbell specimen is placed in the fixing clamps, spaced apart by a length Lo with the minimum possible pretension. The clamps are then moved away from each other at a constant speed of 400 mm/min and the dynamometer measures the force applied as a function of the elongation. The modulus or stress at 100% elongation in MPa is the force ratio measured at 100% elongation on the initial section of the specimen. This is described in paragraph 9.4 Spannungswerte of DIN 53504.

Porosity and water absorption are and have been rated new and after aging.

For ageing, the porosity of the tissue after hydrolysis is also measured. To do this, the fabric is placed for 4 hours in a pressure cooker pressure cooker with water at operating temperature and pressure. We then apply 1 hour of treatment by floating in the open air and at high speed the fabric fixed on a windmill-type assembly (assembly with 4 blades, the fabric being fixed at the end of one of the blades).

Water absorption new and after aging is, and has been measured according to Tappi 441 om-90. It is expressed in %. The equipment consists of a square rubber support and a metal ring coated at its base with a rubber seal. The sample is placed on the square holder and the metal ring is placed on the sample. A clamping device makes the system watertight. A certain quantity of water (100 ml) is placed in the ring, in contact with the sample for a determined time (1 minute). When the time is up, the water is removed from the cylindrical ring, the residual water remaining on the surface of the sample is removed using a cylinder as described in the standard, via a round- return of this cylinder to the sample placed between two blotters, without applying pressure. The percentage of water absorbed is calculated by weight difference before and after contact with water.

The porosity is, and was measured new and after aging in accordance with standard NFG 071 11 or standard NF EN ISO 9237 - Determination of the air permeability of fabrics, the latter replacing the former, but giving results identical. The sample is mounted on a circular sample holder. A suction is launched in order to create a depression of 2000 Pa which induces a flow of air through the sample. The flow rate of this flow is measured and given in L/m ² /min. The % elongation of the fabric under a force of 3 pounds (Lbs) applied in the bias is measured, and was measured. This elongation characterizes the stiffness of the fabric in the bias. The standard used is NF EN ISO 13934-1. Is realiz-ie test pieces 50 mm wide and 300 mm long. The jaws of the dynamometer are 200 mm apart and the measurement is, and was carried out at a speed of 100 mm/min.

Example 2:

This example compares the tenacity impact of PET yarn.

In the “Low tenacity PET control” example, the PET has a tenacity of 4.3 cN/dtex, lower than that of the yarn used in the invention. The fabric in both cases has a PU coating obtained from PU elastomer with a 100% elongation modulus of 2 MPa and isocyanate + melamine formaldehyde crosslinker. The proportion of dry crosslinking agent relative to the dry elastomer is 15.4% for the two tests. The PU is implemented in a 50/50 mixture of toluene and isopropanol, identical formulation for the two tests.

The elongation in the bias of the control fabric is less than 5.2% of the example according to the invention and its porosity after aging is also significantly higher than that of the example according to the invention. This result is surprising, knowing that the degree of coating is higher in the control than that of the fabric of the example according to the invention.

Example 3: This example shows the effect of the modulus at 100% elongation of PU.

Example Control PET has a PU coating obtained from PU elastomer having a modulus at 100% elongation of 8 MPa and melamine formaldehyde crosslinker. The proportion of dry crosslinker relative to the dry elastomer is 15.1%. The PU is processed in a 50/50 mixture of toluene and isopropanol in the same way as the other examples. The textile support is the same.

The use of a PU with a modulus of 100% elongation of 8 MPa leads to an elongation in the bias outside the specifications of the invention, and a very high porosity after aging.

The water resistance of the fabrics of the invention is remarkable. These fabrics are also printable by sublimation. Finally, the fabrics of the invention have a high level of porosity stability after aging, a performance which was not expected.

Claims

1 . Fabric for a flight wing, in particular a paraglider, formed from continuous warp and weft threads and coated on one or both sides with a polyurethane (PU), the bare fabric having a TC coverage rate of between 1.8 and 4, preferably between 2.6 and 3.2, TC being calculated according to the formula TC = (number of filaments/cm x diameter of 1 filament in cm) _Chain + (number of filaments/cm x diameter of 1 filament in cm) tr _ame , characterized in that the yarns are made of poly(ethylene terephthalate) (PET), in that the PET has a tenacity greater than or equal to 6 cN/dtex, in particular between 6 and 7 cN/dtex, in that the fabric has a density of between 30 and 50 threads/cm in warp and weft, in that the polyurethane is a cross-linked PU based on polyether, polyester or polycarbonate, and in that this PU is derived from the crosslinking (1) of a single-component polyurethane having a modulus at 100% elongation less than or equal to 5 MPa, in particular between 1 and 4 MPa, in particular bind between 1 and 3 MPa, according to the DIN 53504 standard, implemented in the organic solvent phase, (2) by a crosslinker, at a rate of a proportion of dry crosslinker relative to the dry elastomer of between approximately 5% and approximately 30% by weight, in particular between approximately 7 and approximately 20% by weight, in particular between approximately 8 and approximately 18% by weight.

2. Fabric according to claim 1, characterized in that the PET yarns have an elongation at break greater than or equal to 20%, in particular between 20 and 30%, according to the DIN EN ISO 2062 standard.

3. Fabric according to any one of the preceding claims, characterized in that the fabric has a weight, coating included, ranging from 25 to 42, in particular from 27 to 42 g/m ² .

4. Fabric according to any one of the preceding claims, characterized in that the dry take-up rate of the coating material is greater than or equal to 10% by weight, in particular between 10 and 30%, preferably between 12 and 30% by weight, better still between 15 and 25%.

5. Fabric according to any one of the preceding claims, characterized in that the fabric comprises warp yarns and weft yarns which have a dtex of between 1 1 and 44 dtex, preferably between 1 1 and 33 dtex, with in particular a DPF (decitex per filament) of between 1 and 4, preferably between 1.3 and 3.5.

6. Fabric according to any one of the preceding claims, characterized in that the PU crosslinker is an isocyanate, a polyisocyanate, melamine, a compound comprising melamine, or a mixture of isocyanate and melamine.

7. Fabric according to any one of the preceding claims, having an air permeability less than or equal to 20 L/m ² /min under 2000 Pa, as measured according to standard NFG0711 1 on a measurement surface of 100 cm ² , and/or water absorption according to the Tappi 441 om-90 standard of less than or equal to 1%, both new and after ageing.

8. Fabric according to any one of the preceding claims, characterized in that it has an elongation in the warp and weft direction bias under 3 lbs less than or equal to 10%, in particular between 1 and 10%, preferably between 3 and 10%, better between 5 and 10%, according to standard NF EN ISO 13934-1.

9. Flight wing, in particular for paragliding, comprising a fabric according to any one of claims 1 to 8.

10. Veil according to claim 9, characterized in that it bears a pattern printed by sublimation.

11 . Method of manufacturing a coated fabric according to any one of claims 1 to 8, in which: a poly(ethylene terephthalate) (PET) fabric is provided having a density of between 30 and 50 threads/cm , in warp and weft; the PET yarns have a tenacity (or tensile strength) greater than or equal to 6 cN/dtex, in particular between 6 and 7 cN/dtex; one or two faces of this fabric are coated with a mixture of single-component polyurethane elastomer having a modulus at 100% of elongation less than or equal to approximately 5 MPa, in particular between 1 and 4 MPa, in particular between 1 and 3 MPa, according to standard DIN 53504, of a solvent for the elastomer and of a crosslinker, at a rate of a proportion of dry crosslinker relative to the dry elastomer of between approximately 5% and approximately 30% by weight, in particular between approximately 7 and approximately 20% by weight, in particular between approximately 8 and approximately 18% by weight; the fabric is heated until the coating dries and reticulates,

- A coated fabric is obtained;