EP4225978A1

EP4225978A1 - Coated lightweight fabric, in particular for a spinnaker

Info

Publication number: EP4225978A1
Application number: EP21786229.1A
Authority: EP
Inventors: Stéphane VERAN
Original assignee: Porcher Industries SA
Current assignee: Porcher Industries SA
Priority date: 2020-10-05
Filing date: 2021-10-04
Publication date: 2023-08-16
Also published as: JP2023545016A; FR3114820A1; CN116249812A; AU2021357581A1; US20230366147A1; KR20230084235A; FR3114820B1; WO2022073901A1; TW202227688A

Abstract

The invention relates to a fabric for lightweight nautical sails for sailboats and other surface vessels, such as spinnakers, asymmetric spinnakers, and gennakers, the fabric being formed from warp yarns and continuous weft yarns made of polyester and being coated on one or both faces with a crosslinked polymer, characterized in that the polyester is polyethylene terephthalate (PET) having a tenacity of 6 cN/dtex or more, in that the fabric has a density of between 20 and 50 yarns/cm in warp and weft, in that the polymer is a polyether-, polyester- or polycarbonate-based cross-linked polyurethane (PU), and in that said PU is derived from the cross-linking (1) of a one-component polyurethane elastomer having a modulus at 100% elongation of between 1 and 15 MPa, better still between 2 and 15 MPa, in particular between 6 and 15 MPa, according to standard DIN 53504, carried out in a solvent phase, and (2) by a cross-linking agent, with a proportion of dry cross-linking agent relative to dry elastomer of between 20% and 75% by weight, in particular between approximately 30 and approximately 75%. The coated fabric has a bias extension at 20 Lbs of between 10 and 30 1/100 inch.

Description

TITLE: Lightweight coated fabric, especially for Spinnaker

The present invention relates to a lightweight fabric formed of continuous warp and weft yarns, this fabric being coated on one and/or both sides with a polyurethane. This lightweight fabric finds its application in particular in the field of light headsails of sailboats and other surface vessels, such as spinnakers, asymmetric spinnakers, and gennakers. The invention also relates to a process for manufacturing this fabric.

A spinnaker, after inflation by the wind, must have a very precise aerodynamic shape. The use of a stiff fabric is therefore preferred to facilitate inflation and maintain the ideal shape. The counterpart of the stiffness of the fabric is the obtaining of fabrics conducive to tearing under strong stresses, causing the bursting of the spinnaker. Traditionally, the use of fabrics whose textile base is Polyamide 6.6 is preferred, the high elasticity and tenacity of Polyamide 6.6 allowing shock absorption. But this polyamide has drawbacks. Polyamide 6.6 is a hydrophilic polymer which gives the fiber a propensity to absorb water. A spinnaker made from a polyamide 6.6 fabric then tends to become heavy and age prematurely under the combined action of UV and hydrolysis. For their part, polyester fabrics, less sensitive to water intake, have proven to be in practice too stiff to be used on sails such as spinnakers. The use of high tenacity polyester fibers, preferably polyethylene terephthalate, supposed to provide even better tear resistance, has not resulted in use in the practice of spinnakers, the great stiffness of the sails thus produced making them suitable for rupture and bursting under high stresses.

Another defect of fabrics for spinnaker is their inadequacy to receive a durable decoration after making the sail, in particular by modern printing techniques.

The objective of the present invention is to remedy the drawbacks of the prior art, by proposing a fabric formed from polyester fibers which has a tear resistance, a modulus and an elasticity allowing its use in the production and use of sails light bows of sailboats and other surface vessels, such as spinnakers, asymmetric spinnakers, and gennakers. Another object of the invention is to provide such a fabric having lower water absorption, and having better resistance to hydrolysis, than the existing solutions based on polyamide fabric.

Another object of the invention is to provide a fabric which has high thermal stability and which makes it possible to print the fabric by sublimation.

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

These and other objectives are achieved by a fabric formed from continuous high tenacity polyester warp and weft yarns. The fabric is coated on one or both sides with a cross-linked polyurethane (PU). The crosslinked PU according to the invention has the ability to compensate for the excessive stiffness (the very high modulus) and the low elasticity of the fabrics made of high tenacity polyester fibers. The cross-linked polyurethane is flexible and is therefore durable in the face of the mechanical stresses that the sail undergoes during its existence. Preferably, the polyurethane is a polyether, polyester or polycarbonate based PU. The preferred polyurethane is a polycarbonate based PU. 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 about 15 MPa, in particular between 1 and 15 MPa according to standard DIN 53504. Better still, this modulus is between 2 and 15 MPa , in particular between 6 and 15 MPa, more particularly still between 6 and 10 MPa, typically between 6 and 9.5 MPa, for example approximately 8 MPa, according to standard DIN 53504. Another important preferred characteristic is that the elastomer is made of mixture with a crosslinker (not to be confused with the crosslinking agent used to form the elastomer), and that the proportion of dry crosslinker relative to the dry elastomer is between approximately 20% and approximately 75%, better still between approximately 30% and approximately 75% by weight, in particular between approximately 40 and approximately 75% by weight, in particular between approximately 50 and approximately 75% by weight (for example approximately 67%). 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 form, headsails of sailboats and other surface vessels, such as spinnakers, asymmetrical spinnakers, and gennakers.

The invention relates in particular to a fabric for light nautical sails of sailboats and other surface vessels, such as spinnakers, asymmetrical spinnakers, and gennakers, the fabric being formed of warp yarns and continuous weft yarns of polyester and being coated on a or its two faces by a cross-linked polymer, characterized in that the polyester is poly(ethylene terephthalate) (PET), in that the fabric has a density of between 20 and 50 threads/cm, preferably between 25 and 50 threads/cm, in warp and in weft, in that the polymer is a crosslinked polyurethane (PU) based on polyether, polyester or polycarbonate, preferably 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 approximately 15 MPa, in particular between 1 and 15 MPa, in particular between 2 and 15 MPa, more particularly still between 6 and 15 MPa, typically between 6 and 10 MPa, for example between 6 and 9.5 MPa, for example around 8 MPa according to the DIN 53504 standard, implemented in the organic solvent phase (in particular dissolved in a solvent), (2) by a crosslinker, at the rate of a proportion of dry crosslinker relative to to the dry elastomer of between approximately 20 and approximately 75% by weight, better still between approximately 30% and approximately 75% by weight, in particular between approximately 40 and approximately 75% by weight, in particular between approximately 50 and approximately 75% by weight .

Advantageously, the coated fabric has an elongation in the bias under 20 lbs, comprised between 10 and 30,100 ^th of an inch, preferably between 14 and 25,100 ^th of an inch, according to standard NF EN ISO 13934-1. The combination of the modulus at 100% elongation of the PU and the crosslinking rate, each taken in the given intervals, makes it possible in particular to obtain this elongation in the bias allowing to bring the flexibility to the fabric which is necessary for the application. and that the intrinsic tenacity of the PET yarn was not predictable. In particular, the high range of modulus values may be favored over the low range of crosslinker content values, and vice versa.

The dry coating rate relative to the total dry fabric may in particular be greater than 5%, in particular between 5% and 30% by weight, in particular between 10 and 30% by weight, better still between 15 and 25% by weight . The dry coating rate is the ratio by weight of coating (crosslinked PU) dry on the coated fabric, it is representative of the weight of dried/crosslinked coating present on the final fabric. The dry coating rate mentioned here means the total coating rate, either on one side or on both sides, depending on the case selected. Preferably, the polyester is poly(ethylene terephthalate) or PET. 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 threads and weft threads which have a dtex of between 11 and 235 dtex, for example between 22 and 110 dtex, in particular between 22 and 78 dtex, with in particular a DPF (decitex per filament) between 1 and 4, preferably between 1.3 and 3.5.

The tenacity of 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 fibers optionally contain one or more additives, for example a stabilizer and/or an antistatic agent.

An important preferred characteristic is that the bare fabric has a density between 20 and 50 threads/cm, preferably between 25 and 50 threads/cm, in weft and a density between 20 and 50 threads/cm, preferably between 25 and 50 threads/cm in warp. Preferably, the yarn density is identical in warp and weft. As a variant, the density in warp and in weft can be different, in particular with a variation between 10 and 30% between warp and weft, the density being higher in warp or in weft, preferably in warp.

In one embodiment, the fabric has a hybrid construction, with the use of fibers or yarns of different counts between the warp and the weft. The fabric can then have warp yarns and weft yarns which have a dtex (count) of between 11 and 235 dtex, in particular between 22 and 110 dtex, in particular between 22 and 78 dtex, with the warp yarns having a count higher than the count of weft threads. As a non-preferred variant, it is the weft yarns which have a higher count. By higher, one can in particular mean that the count of the threads in one direction is greater by 1.5 or 2 to 5 times the count of the threads in the other direction.

The weight of the coated fabric may in particular be between 25 and 130 g/m ² , preferably between 30 and 120 g/m ² .

The fabric of the present invention is characterized by stiffness in the bias. The bias is called warp direction because it is measured in the 45° direction with respect to the warp threads. This stiffness in the bias is expressed by the elongation in 100 ^th of an inch, which is measured under a force of 20 pounds (Lbs, or 89N) 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 with a width of 76.2 mm and a length of 300 mm are produced. The jaws of the dynamometer are separated from each other by 152.4 mm and the measurement is carried out at a speed of 50 mm/min. In the bias, the specimens are cut from the fabric according to these dimensions, by applying an angle of 45° with respect to the warp direction of the fabric, then the two pieces of fabric are superimposed and subjected together to the effect of the dynamometer. The elongation in 100 ^th of an inch in the warp and weft directions is carried out according to the same standard, and in this case a single piece of fabric is used.

The elongation in the bias of the coated fabric under 20 lbs, can in particular be between 10 and 30,100 ^th of an inch, preferably between 14 and 25,100 ^th of an inch. This is the preferred target that the invention sets itself. The flexible polyurethane coating achieves this objective, despite the fact that high Young's modulus PET yarns, generally between 3 and 15 GPa, give the fabric high stiffness and low elasticity. A coated fabric with a bias stretch of less than ^10,100ths of an inch will be too stiff and may burst under heavy stress. A fabric with a bias stretch greater than 30 ^100ths of an inch will be too soft and will give a sail, such as a spinnaker, with degraded aerodynamic performance.

The Young's modulus or modulus of elasticity characterizing polyester or PET fibers or yarns is the constant in pascals which links the stress and the deformation generated by this stress when one is in the elastic range of the material. It is obtained by measuring the slope at the origin of the force=f(strain) curve. The elongation at break is (L-L0)/L0*100, L being the length at break and LO the initial length of the sample.

The modulus at 100% elongation as used to characterize the elastomer is no longer Young's modulus but an equivalent measured at 100% elongation.

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. Unless otherwise indicated, the term "isocyanate" should be understood herein as grouping 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 compound or a resin containing melamine , for example a melamine-formaldehyde resin.

According to one embodiment, the proportion of dry crosslinking agent relative to the dry elastomer is between approximately 20 and approximately 75% by weight, better still between approximately 30% and approximately 75% by weight, in particular between approximately 40 and approximately 75% by weight, in particular between about 50 and about 75% by 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 one 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. A polycarbonate-based polyurethane is used in the examples and constitutes a particularly suitable embodiment.

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

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 crosslinked 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. The coating also provides appropriate porosity for the use for which the fabric is intended. 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;

(b) one or two faces of this fabric are coated with a solvent-based polyurethane 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) is available having a density of between 20 and 50 threads/cm, preferably between 25 and 50 threads/cm, in warp and weft; one or two faces of this fabric are coated with a mixture of single-component polyurethane elastomer having a modulus at 100% elongation as described above, of solvent for the elastomer and of a crosslinking agent, to due to a proportion of dry crosslinker relative to the dry elastomer as described above; 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 and its coating are applicable to the process, to the choice of these elements for their implementation in the process, without it being necessary to repeat them in what follows.

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.

In one embodiment, the method comprises, after the drying and crosslinking step, one or more post-treatment step(s) giving the fabric anti-soiling and/or water-repellent properties. By “anti-soiling” treatment, we mean a treatment with using anti-static and/or anti-tack products. By “water-repellent” treatment is meant a treatment using fluorinated resins with or without a crosslinking agent for the fluorinated resin, for example an isocyanate. The water-repellent treatment is followed by a drying/cross-linking 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. It is also possible to carry out a treatment with silicone to improve the slipperiness of the fabric.

According to one embodiment, before coating, the fabric is calendered. 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. According to one embodiment, calendering is carried out between a calendering tool, cylinder or roller and a counter-plate. The side of the fabric that has undergone the passage of the calendering tool, called the "calendering side", is smoothed compared 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 called adhesion treatment. This is, for example, a chemical treatment providing functional groups capable of reacting with groups in 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 dry coating rate varies according to the side concerned, this rate being higher on the unsmoothed side, 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, calendering is carried out 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 is preferably carried out at a temperature between about 150 and about 250°C, preferably between about 180 and about 210°C. The calendering is preferably carried out with a pressure ranging from approximately 150 to approximately 250 kg, preferably between approximately 180 and approximately 230 kg. The rotation speed of the calender can be between approximately 1 and approximately 30 m/min, preferably between approximately 10 and approximately 20 m/min. 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).

Consequently, in one embodiment, the lightweight fabric of the present invention is obtained or capable of being obtained by coating polyurethane, preferably one-component elastomer, in solvent phase.

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.

The coated fabrics described here prove capable of being printed by the technique known as sublimation. 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. Dyes pass into the gaseous phase and are transferred to the coating, and/or to the surface and/or to the fiber. PET polyester remains stable at this temperature.

Spinnakers (standard or asymmetrical) and gennakers are windward inflatable sails, which typically include three angled tops, commonly referred to as head or halyard point, clew point and tack point. These veils are obtained by assembling widths, in particular several radial widths which open out from each angular vertex, each radial width being obtained beforehand in the form of a flat fabric coupon, cut according to the geometric needs of the width to obtain.

The subject of the invention is thus an article such as a headsail for a sailboat and other surface vessels, such as a spinnaker, asymmetrical spinnaker, and gennaker, comprising a coated fabric according to the invention or made from a or more coated fabrics or fabric widths according to the invention. In particular, the article may comprise several fabrics or widths according to the invention, assembled to form the article in question. In one embodiment, the nautical sail bears a sublimation printed design. In particular, the nautical sail bears a pattern made up of dye inside the PU coating and/or on the surface or inside the PET yarns.

The invention also relates to said widths cut from a fabric according to the invention.

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

PA6.6 is a classic polyamide fabric in the spinnaker field, with a PU coating obtained from PU elastomer with a 100% elongation modulus of 32.4 and melamine formaldehyde crosslinker. The proportion of dry crosslinker relative to the dry elastomer is 104%. The PU is implemented in a 50/50 mixture of toluene and isopropanol. PET has a PU coating obtained from PU elastomer having a 100% elongation modulus of 8 and melamine formaldehyde crosslinker. The proportion of dry crosslinker relative to the dry elastomer is 66.9%. The PU is implemented in a 50/50 mixture of toluene and isopropanol.

The tenacity of PET is 6.8 cN/dtex. The elongation at break is 24.6%.

The coating is carried out using a doctor blade, and is followed by a drying step at 100°C, then a crosslinking step at 170°C). The speed is 27 m/min.

[Table 1 ]

[Table 2]

Example 2:

The fabric of the invention of Example 1 in yarns of 33 dtex is taken up and compared to counter-Examples 1 and 2, which differ from it by combinations of PU modulus and crosslinking rate which are outside the limits. of the invention.

[Table 3]

Methods and measurements used 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.

The elongations of the fabric are measured according to standard NF EN ISO 13934-1, as described in the general description. The lower elongation in the direction of the warp and weft yarns due to the polyester nature is compensated by a higher elongation in the bias (measured here in the warp direction). This elongation in the bias compensates for the excessive rigidity of PET and avoids the risk of rupture and bursting under high stress. The mechanical performance is equivalent or even superior, this reflecting a polyester fabric suitable for spinnaker use.

The water absorption by the coated fabric of Example 1 was measured according to the Tappi 441 om-90 standard. One measurement was taken on the new coated fabric, another after ageing. 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 support and the metal ring is placed on the sample. A clamping device makes the system watertight. A certain amount 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.

For ageing, the fabric is placed for 4 hours in a pressure cooker with salt water (30 g/l) 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).

The fabric according to the invention has seen its water absorption hardly change unfavorably after aging. This level of resistance to water intake is another surprising result.

Claims

CLAIMS Fabric for light nautical sails of sailboats and other surface vessels, such as spinnakers, asymmetric spinnakers, and gennakers, the fabric being formed of warp yarns and continuous weft yarns of polyester and being coated on one or both sides with a crosslinked polymer, characterized in that the polyester is 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 20 and 50 threads/cm, preferably between 25 and 50 threads/cm, in warp and in weft, in that the polymer is a crosslinked polyurethane (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 of between 1 and 15 MPa, better still between 2 and 15 MPa, in particular between 6 and 15 MPa, more particularly still between 6 and 10 MPa, typically between 6 and 9.5 MPa, according to standard DIN 53504, implemented in the solvent phase, (2) by a crosslinker, at the rate of a proportion of dry crosslinker relative to the dry elastomer of between 20% and 75% by weight, in particular between 30 and 75% by weight, in particular between about 50 and about 75% by weight. Fabric according to Claim 1, characterized in that the coated fabric has an elongation in the bias under 20 lbs, of between 10 and ^30,100ths of an inch, preferably between 14 and ^25,100ths of an inch, measured on test specimens of width 76.2 mm and 300 mm long according to standard NF EN ISO 13934-1. Fabric according to Claim 1 or 2, characterized in that the fabric comprises warp threads and weft threads which have a count of between 1 1 and 235 dtex, in particular between 22 and 1 10 dtex, more particularly between 22 and 78 dtex, with a DPF (decitex per filament) of between 1 and 4, preferably 1.3 and 3.5. Fabric according to any one of the preceding claims, characterized in that the PET has an elongation at break greater than or equal to 20%, in particular between 20 and 30%, according to standard DIN EN ISO 2062. Fabric according to any one of the preceding claims, characterized in that the dry coating rate of reticulated PU relative to the total dry fabric is greater than 5% by weight, in particular between 5 and 30% by weight, preferably between 10 and 30 % by weight, better still between 15 and 25 % by weight. Fabric according to any one of the preceding claims, characterized in that the weight of the coated fabric is between 25 and 130 g/m ² , preferably between 30 and 120 g/m ² .

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

8. Fabric according to any one of the preceding claims, characterized in that the isocyanates or polyisocyanates, and/or the crosslinker are aliphatic.

9. Light nautical sail, in particular spinnaker, asymmetrical spinnaker, or gennaker, comprising a fabric according to any one of claims 1 to 8, or formed from the assembly of several fabrics according to any one of claims 1 to 8.

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

11 . Method of manufacturing the coated fabric according to any one of claims 1 to 8, comprising: a poly(ethylene terephthalate) (PET) fabric is provided having a density of between 20 and 50 threads/cm, preferably between 25 and 50 threads/cm, in warp and in weft, and the PET has a tenacity 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 about 15 MPa, in particular between 1 and 15 MPa, better still between 2 and 15 MPa, in particular between 6 and 15 MPa, in particular between 6 and 10 MPa, typically between 6 and 9.5 MPa, according to standard DIN 53504, of solvent for the elastomer and of a crosslinking agent, at a rate of a proportion of dry crosslinking agent with respect to the dry elastomer comprised between approximately 20% and approximately 75% by weight, in particular between approximately 30 and approximately 75% by weight, in particular between approximately 50 and approximately 75% by weight; the fabric is heated until the coating dries and reticulates,

- A coated fabric is obtained;