Patent Application
20240133128
The present invention is related to a granule for use in an artificial turf system, and to an artificial turf system using such granules.
Artificial turf systems have been used for long, and have developed through a number of generations to their present form. In general, such systems seek to achieve the same characteristics as their natural counterparts although in certain areas these may have already been surpassed, at least in terms of predictability of behaviour.
At present, typical turf systems comprise a backing layer with an upper surface and an infill layer of soft granules disposed between the fibres. The backing layer may consist of a woven fabric in which artificial grass fibres are tufted to provide pile fibres oriented in an upward position and fixed to the woven fabric by a backing layer of latex or polyurethane. Installation of the turf system typically involves providing a layer of loose sand, strewn between the upstanding turf fibres, which by its weight holds the backing in place and supports the pile in upward position. Onto this sand layer and also between the artificial turf fibres, granules are strewn, forming a loose performance infill layer that provides the necessary sport performance. These performance characteristics will be dependent on the intended use but for most sports will include: rotational and linear grip; force reduction; vertical ball bounce; and rotational friction. This performance can be further supported by applying a shock pad layer directly under the backing layer.
Even if such artificial turfs have now been shown to have similar, or even better, properties than natural turfs, the plastic material used in such turfs is an environmental problem. The plastic material used in the artificial turfs spreads and is broken down into micro-plastics, which contaminates the environment.
Previously known artificial turf systems are e.g. known from U.S. Ser. No. 10/844,553, WO 2006/092337, WO 2006/025973, US 2008/0145574, US 2020/0224374 and US 2015/0191879.
However, there is still a need for an environmentally friendly solution for use in artificial turs, which have similar or even better properties than natural turfs, and which is environmentally friendly.
It is therefore an object of the present invention to provide an artificial turf system, and granules for use therein, which alleviates all or at least some of the above-discussed drawbacks of the presently known systems.
These objects are achieved by means of an artificial turf system, and granules for use in such a system, as defined in the appended claims.
According to a first aspect of the present invention, there is provided an artificial turf system, comprising:
According to another aspect of the present invention, there is provided a granule for use as an infill for an artificial turf system, wherein said granule comprises at least 60 wt % polybutylene adipate terephthalate (PBAT) and a pigment or pigment masterbatch.
The present invention relates to the environmental issue of persistent micro plastic release from infill materials dispersed on artificial turf systems. In comparison to traditional infill materials, a relatively small amount of the present infill is required as infill, which in combination with its biodegradable properties prevents the release of persistent and harmful microplastics to the environment. Thanks to its high flexibility, the new infill in combination with an appropriate artificial turf system, provides ideal playing surfaces for a wide range of outdoor and indoor sports such as football, paddle, lacrosse, basketball, and activities on playgrounds.
PBAT is fully compostable and highly flexible, thus being a sustainable. It has also been found to have very high-performance as infill distributed on artificial turf systems to provide ideal playing surfaces for a variety of outdoor and indoor applications, such as football. The PBAT based granules may be used to provide a fully compostable and highly flexible infill material for artificial turf systems. The new granules are extremely flexible and can be made by fully compostable plastic. The granules may e.g. be shaped as cylindrical granules, highly appropriate for applications such as infill for artificial turfs. The granules alleviate the release of long-lived microplastics to the surrounding environment and nearby watercourses. The new infill is in particular useful as an infill material on artificial turfs for football, where it has passed the highest performance and quality tests by FIFA (FIFA Quality Pro). The outstanding properties are correlated to a high flexibility and softness of the material, giving rise to reduced requirement of infill (<8.5 kg/m2). Used granules may furthermore be recycled as to move towards a circular chemical economy with no harmful impact on the environment.
The pigment forms a protecting surface around the granules that protects them from UV light and hence extends the product lifetime when used as an outdoor infill material. The pigment is preferably a dark pigment, such as having a color of dark green. The pigment may be provided in the form of a pigment masterbatch. A masterbatch is here referring to a solid or liquid additive for plastics comprising a concentrated mixture of pigments, encapsulated in a carrier, such as a resin made of polymer, wax or the like. The masterbatch may contain 20-65 wt % of the pigment.
The granule(s) preferably comprises at least 70 wt % PBAT, and preferably at least 80 wt %, and most preferably at least 90 wt %. In embodiments, the content of PBAT may be at least 95 wt %, and even at least 97 wt %.
PBAT is a per se well known thermoplastic polymer, which is known to be a highly flexible and tough co-polyester.
The PBAT is preferably fossil-based or partly bio-based. Preferably, the PBAT is at least partly bio-based, i.e. Bio-PBAT.
The granule(s) preferably have/has a diameter size in the range of 0.1-5 mm, and preferably 0.5-5 mm, and more preferably 1-5 mm, and preferably 1.5-4 mm, and most preferably 1.5-3.5 mm, and with a length in the range of 1-15 mm, and preferably 1.5-10 mm, and most preferably 1.5-5 mm. Thus, the granule(s) may have a mean diameter size of 2.5 mm±1.0 mm and a length varying between 1-15 mm. Shorter lengths than 1 mm are also feasible, such as down to 0.5 mm or down to 0.1 mm. Thus, the length may alternatively be in the range 0.1-15 mm, 0.5-15 mm, 0.1-5 mm, 0.5-5 mm, 0.5-4 mm and the like.
The above-discussed diameters and lengths may be used for granule(s) having a cylindrical shape, having a circular cross-section. However, the same preferred diameter and lengths dimensions will apply also for granules forming cylinders with a non-circular cross-section, as well as for granules not in the form of cylinders. A diameter for non-circular cross-sections is consequently to be interpreted broadly and covers a mean cross-sectional dimension also for non-circular shapes. The diameter for such non-circular shapes may e.g. be calculated based on the perimeter of the non-circular shape, whereby the diameter d may be calculated as d=p/π.
In a preferred embodiment, the granule(s) are in the form of a cylinder. A cylinder has a uniform cross-section over its entire length. In one embodiment, the cross-section is be in the form of a circle, providing a circular cylinder. However, other cross-sectional shapes may also be used, such as shapes in the form of a triangle, a square, a rectangle, and other polygon shapes. The cross-sectional shape may also be an oval, or other, more complex shapes, such as the shape of a star, a crystal shape, a three- or four-leaf clover, etc.
In some embodiments, the granules may also be shaped in other 3-dimensional shapes than the one of a cylinder, such as in the form of a discus, a sphere or the like.
In some embodiments, the granules may be shaped as an ellipsoid. An ellipsoid has three pairwise perpendicular axes of symmetry which intersect at a center of symmetry, the center of the ellipsoid. The line segments that are delimited on the axes of symmetry by the ellipsoid may be referred to as the principal axes, or simply axes of the ellipsoid.
The granules may have the shape of an ellipsoid where the three axes have different lengths, whereby the ellipsoid may be referred to as a triaxial ellipsoid, and the axes are uniquely defined.
The granules may have the shape of an ellipsoid where two of the axes have the same length, whereas the third has a different length. In this case, the ellipsoid may be referred to as an ellipsoid of revolution, i.e. a biaxial ellipsoid or a spheroid. In this case, the ellipsoid is invariant under a rotation around the third axis.
The third axis may be shorter than the other two, whereby the ellipsoid forms an oblate spheroid. An oblate spheroid may be seen as an ellipse rotated about its minor axis, to form a flattened spheroid, shaped like a lentil.
Alternatively, the third axis may be longer than the other two, whereby the ellipsoid forms a prolate spheroid. A prolate spheroid may be seen as an ellipse rotated about its major axis, forming the shape of an American football or rugby ball.
The three axes may also have the same length, whereby the ellipsoid forms a sphere.
The granule(s) preferably have/has a Shore D hardness of 44 or less, and preferably in the range 25-44, and more preferably 32-42, and most preferably 34-40.
In a preferred embodiment, the dark pigment is a dark green pigment.
The granule(s) preferably have/has a flexural strength, measured in accordance with ISO 178:2019, within the range of 2-17 MPa, and preferably 3-8 MPa, and most preferably 4-6 MPa.
The granule(s) preferably have/has a flexural modulus, measured in accordance with ISO 178:2019, of 50-250 MPa, and preferably 55-150 MPa, and most preferably 60-90 MPa.
The granule(s) preferably have/has an offset stretch (0.2%), measured in accordance with ISO 178:2019, of 1-10 MPa, and preferably 2-7 MPa, and most preferably 3-6 MPa.
The granule(s) may comprise PBAT as the only polymeric constituent. However, the granule(s) may also comprise a blend of PBAT and one or more other thermoplastic polymers. In that case, the polymeric part of the blend, excluding possible filler material, preferably comprises at least 70 wt % of PBAT and 30 wt % or less of the other thermoplastic polymer(s). Put differently, in case other thermoplastic polymers are included in the blend, in addition to PBAT, the total amount of these other thermoplastic polymers is preferably less than half the amount of PBAT.
The granule(s) may further comprise 1-30 wt % of another compostable polymer, and preferably at least one of: polyethylene furanoate (PEF), polyhydroxy alkanoates (PHA), polylactic acid (PLA), polybutylene succinate (PBS), poly(butylene succinate-co-butylene adipate) (PBSA), polycaprolactone (PCL), thermoplastic starch (TPS), and starch, or combinations thereof. Such materials may be included in the blend to adjust the hardness, flexibility, and other properties of the material.
The granule(s) may comprise 1-30 wt % of another biobased polymer, and preferably at least one of: PLA, polyhydroxy alkanoates (PHA), polyhydroxybutyrate (PHB), polyamide 11 (PA11), polyamide 1010 (PA1010), Bio-polyethylene (Bio-PE), Bio-polypropylene (Bio-PP), Bio-polyvinyl carbonate (Bio-PVC), Bio-polethylene terephthalate (Bio-PET) and Bio-polybutadiene (Bio-PBU), or combinations thereof. “Bio” here indicates that the materials are biobased. Such materials may be added to make the granule(s) even more attractive from an environmental point of view.
The granule(s) may further comprise a filler material, wherein the filler material comprises at least one of: chalk, talc, kaolin, wood fiber, bast fiber, lignocellulose, cellulose, hemicellulose, lignin, flax, and hemp, and combinations thereof. Such filler material(s) may be added to improve other properties of the material, and to facilitate other conditions and requirements. Filler materials, such as chalk or the like, may e.g. be added for the purpose of reducing cost, increasing specific density or adjusting other characteristics of the granule(s).
The total amount of the filler material(s) is preferably less than 40 wt %, and may in embodiments be less than 30 wt %, less than 20 wt %, less than 10 wt %, or less than 5 wt %. In embodiments, no filler material may be used. However, in other embodiments, the amount of filler material(s) may be at least 1 wt %, at least 5 wt %, at least 10 wt %, at least 20 wt % or at least 30 wt %. Thus, the amount of filler material(s) may be in the range of 0-40 wt %, and preferably in the range of 1-40 wt %, such as 1-30 wt %, 1-20 wt % or 1-10 wt %.
Regardless of whether the granule(s) is formed of only PBAT and pigment/pigment masterbatch, or if other constituents are added, such as other thermoplastic polymers, fillers or the like, the material is preferably blended to form a homogenous material. The granule(s) are preferably in their entirety made of homogeneous material.
For production of the granules, the material is mixed into a master batch. The material may then be extruded, to form a strand, and be cut into granules using e.g. a strand pelletizer. In the process of strand pelletizing, the strand may be fed from the die of the extruder into a cooling water bath, and subsequently be cut and dried in the pelletizer. The result may be smooth green-grey extruded granules of cylindrical shape with a mean diameter size of 2.5 mm±1.0 mm and a length varying between 1.0-15 mm.
Production of non-cylindric shapes can be made in a similar way, and e.g. by use of an underwater pelletizing process in an underwater pelletizer.
After use, the granules are fully compostable. Specifically, preliminary tests indicate that the above-discussed granule(s) meets the requirements related to disintegration specified in the standard ISO 20200 (Disintegration test).
The granules may also be recycled by gathering the granules, separating them from dust, washing, drying, and re-processing them, to increase the bio-sustainability.
The artificial turf system may further comprise a resilient layer comprising a shock-pad structure beneath the substrate and an additional particulate layer between the shock-pad structure and the infill layer. The additional particulate layer may comprise particulates of at least one of: sand, grit, rubber, cork, wood, elastomer and plastic particulates, or combinations thereof. In a preferred embodiment, the additional particulate layer comprises sand.
These and other features and advantages of the present invention will in the following be further clarified with reference to the embodiments described hereinafter.
For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:
In the following detailed description, preferred embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention.
An embodiment of a granule for use as an infill for an artificial turf system is schematically illustrated in
The above-discussed diameters and lengths may be used also for granule(s) having a cylindrical shape with non-circular cross-sections, as well as for non-cylindrical granule(s), as will be exemplified in more detail in the following. In such cases, a diameter for non-circular cross-sections relates to is a mean cross-sectional dimension. The diameter for such non-circular shapes may e.g. be calculated based on the perimeter of the non-circular shape, whereby the diameter d may be calculated as d=pin.
However, the granule may also be in the form of other cylindrical shapes, having other cross-sections. Such alternative shapes are schematically illustrated in
The cylinder may have a length which is greater than the diameter, as in the illustrative example of
In some embodiments, the granules may also be shaped in other 3-dimensional shapes than the one of a cylinder, such as in the form of a sphere, as schematically illustrated in
In some embodiments, the granules may be shaped as an ellipsoid. An ellipsoid has three pairwise perpendicular axes of symmetry which intersect at a center of symmetry, the center of the ellipsoid. The line segments that are delimited on the axes of symmetry by the ellipsoid may be referred to as the principal axes, or simply axes of the ellipsoid.
The granules may have the shape of an ellipsoid where the three axes have different lengths, whereby the ellipsoid may be referred to as a triaxial ellipsoid, and the axes are uniquely defined.
The granules may, as illustrated in
The third axis z, i.e. the length c, may be shorter than the other two axes, i.e. the radius a, whereby the ellipsoid forms an oblate spheroid, as illustrated in
Alternatively, the third axis z, i.e. the length c, may be longer than the other two axes, i.e. the radius a, whereby the ellipsoid forms a prolate spheroid, as illustrated in FIG. 4d. A prolate spheroid may be seen as an ellipse rotated about its major axis, forming the shape of an American football or rugby ball. Here, the length of the granule is c, and the diameter is 2*a, and c>a.
The three axes may also have the same length, whereby the ellipsoid forms a sphere, as in the illustrative example of
The above-discussed shapes, and in particular the cylindrical shapes and the spheroid shapes, provides granules that immediately reach a packed structure when placed as an infill layer in an artificial turf system. This packed structure is reached directly after installation and is stable during time because it cannot compact more than this. However, the particles are loose enough to move under influence of force. This results in a structure of the infill layer, which is responsible for a natural turf character.
The granules may be used as an infill for an artificial turf system. Such an artificial turf system is schematically illustrated in
The fibers may be synthetic fibers composed of polyethylene, polypropylene or nylon. The fibers are for example single fibers or multiple fibers but also a mixture of multiple fibers and single fibers may be used. The thickness of the fibers may vary. However also a mix of thick and thin fibers is possible. The general criteria for making the backing sheet and the fibers are known in the art, and hence do not require a detailed description.
The infill layer 25, comprising the above-discussed granules, is placed above the substrate 21. The infill layer 25 may have granules provided in the range of 5-12 kg/m2, preferably 6-10 kg/m2, and most preferably 7-8.5 kg/m2, such as about 8 kg/m2 or about 8.5 kg/m2. The weight of the infill layer is preferably less than 8.5 kg/m2.
The infill layer can be present at a depth that is sufficient to adequately support the pile fibers over a substantial portion of their length, and may depend on the length of these fibers and the desired free pile. In a preferred embodiment, the infill layer has a depth of at least 10 mm. In other embodiments, the infill layer may be present to a depth of at least 20 mm or even to a depth of greater than 30 mm. It will be understood that the final depth will also depend upon whether the infill layer is the only layer on the substrate supporting the pile fibers and if a shock pad or other form of resilient layer is applied. In a preferred embodiment, the infill layer has a depth in the range of 10-25 mm, and preferably 15-20 mm, such as about 17 mm. Depending on the nature of the sport, the pile fibers may extend at least 10 mm or at least 15 mm or even more than 20 mm above the level of the infill.
The system may also comprise one or more additional particulate layers disposed on the substrate beneath the infill layer. The additional particulate layers may have various functions, including shock absorption, pile stabilization, drainage, filling and the like and may be selected from the group comprising: sand, grit, rubber particles, elastomer particles, thermoplastic particles and any other particles that do not meet the definition of the infill granules. In the illustrative example, the additional particulate layer 24 comprises sand, such as silica sand.
The additional particulate layer 24, here of sand, may have a weight of 10-20 kg/m2, and preferably 12-17 kg/m2, such as about 15 kg/m2. The additional particulate layer may have a depth of 5-15 mm, such as about 10 mm.
Beneath the substrate 21 a resilient layer 23 comprising a shock-pad structure may be provided. The shock-pad may e.g. be made of PE closed-cell foam. The shock-pad may have a thickness in the range 8-15 mm, and preferably 10-13 mm, such as 12 mm, and may have a density of 25-75 kg/m3, such as 50 kg/m3.
The granules are preferably made of a homogeneous material. The material comprises at least 60 wt % polybutylene adipate terephthalate (PBAT) and a pigment or pigment masterbatch. The pigment is preferably dark, such as a dark green pigment. The pigment protects the granules from degradation due to UV radiation, and also makes the granules more heat absorbing.
The granule(s) preferably comprises at least 70 wt % PBAT, and preferably at least 80 wt %, and most preferably at least 90 wt %. In embodiments, the content of PBAT may be at least 95 wt %, and even at least 97 wt %.
The PBAT may be fossil-based, but is preferably at least partly bio-based, and may in embodiments be only bio-based, i.e. Bio-PBAT.
The granules may comprise PBAT as the only polymeric constituent. However, the granules may also comprise a blend of PBAT and one or more other thermoplastic polymers. In that case, the polymeric part of the blend, excluding possible filler material, preferably comprises at least 70 wt % of PBAT and 30 wt % or less of the other thermoplastic polymer(s). Put differently, in case other thermoplastic polymers are included in the blend, in addition to PBAT, the total amount of these other thermoplastic polymers is preferably less than half the amount of PBAT. For example, the granules may comprise 1-30 wt % of another compostable polymer, and preferably at least one of: polyethylene furanoate (PEF), polyhydroxy alkanoates (PHA), polylactic acid (PLA), polybutylene succinate (PBS), poly(butylene succinate-co-butylene adipate) (PBSA), polycaprolactone (PCL), thermoplastic starch (TPS), and starch, or combinations thereof. Such materials may be included in the blend to adjust the hardness, flexibility, and other properties of the material. Additionally, or alternatively, the granules may comprise 1-30 wt % of another biobased polymer, and preferably at least one of: PLA, polyhydroxy alkanoates (PHA), polyhydroxybutyrate (PHB), polyamide 11 (PA11), polyamide 1010 (PA1010), Bio-polyethylene (Bio-PE), Bio-polypropylene (Bio-PP), Bio-polyvinyl carbonate (Bio-PVC), Bio-polethylene terephthalate (Bio-PET) and Bio-polybutadiene (Bio-PBU), or combinations thereof.
The granules may further comprise a filler material, wherein the filler material comprises at least one of: chalk, wood fiber, lignocellulose, cellulose, hemicellulose, lignin, bast-fiber, flax and hemp, and combinations thereof. The total amount of the filler material(s) is preferably less than 40 wt %, and may in embodiments be less than 30 wt %, less than 20 wt %, less than 10 wt %, or less than 5 wt %. In embodiments, no filler material may be used. However, in other embodiments, the amount of filler material(s) may be at least 1 wt %, at least 5 wt %, at least 10 wt %, at least 20 wt % or at least 30 wt %. Thus, the amount of filler material(s) may be in the range of 0-40 wt %, and preferably in the range of 1-40 wt %, such as 1-30 wt %, 1-20 wt % or 1-10 wt %.
For production of the granules, the material is mixed into a master batch. The material may then be extruded, to form a strand, and be cut into granules using e.g. a strand pelletizer. In the process of strand pelletizing, the strand may be fed from the die of the extruder into a cooling water bath, and subsequently be cut and dried in the pelletizer. The result may be smooth green-grey extruded granules of cylindrical shape with a mean diameter size of 2.5 mm±1.0 mm and a length varying between 1.0-15 mm.
For production of non-cylindrical shapes, such as spheres or spheroids, pelletizing with die-face cutters may be used, where the melt is cut directly at the die opening, before a cooling medium, usually air or more often water, transports the freshly cut particles away, cooling them in process. In particular, it is possible to use underwater pelletizing for formation of such granules.
After use, the granules are fully compostable. Specifically, the granules are believed to meet the requirements related to disintegration specified in the standard ISO 20200 (Disintegration test).
The granules may also be recycled after use by gathering the granules, separating them from dust, washing, drying, and re-processing them, to increase the bio-sustainability.
For evaluation of the new granules, a number of tests have been performed. For these tests, granules comprising more than 90 wt % of PBAT were used, in combination with a dark green pigment. The granules had a cylindrical shape with a mean diameter size of 2.5 mm±1 mm and a length of about 1-5 mm.
The hardness and flexural properties of the granules were first examined by standardized methods using a 3 mm thin plastic plate, which was created by pressing the granules together under high pressure at 200° C. The plates were then subjected to thermal conditioning for 3 h at 23° C. before testing. Compared to already existing infills, e.g. polyethylene (PE), as discussed in U.S. Ser. No. 10/844,553, the new granules are considerably softer with a Shore D hardness of 37, measured by the Bareiss Digitest apparatus according to ISO 48-4 for two layers of the plastic plate.
It is concluded that the granules preferably should have a Shore D hardness of 44 or less, and preferably in the range 25-44, and more preferably 32-42, and most preferably 34-40.
Flexural properties of the granules were measured by the Tinius Olsen H5ST apparatus, equipped with a three-point bend test fixture, according to ISO 178:2019. In comparison to harder reference plastics (PP and PC), the new granules have a low flexural strength (5.2 MPa) and modulus of elasticity in flexure (75.7 MPa) similarly to the flexible LDPE reference, see table 1. The flexural modulus for the new granules is hence in the bottom range for semi-rigid plastics (70-700 MPa) compared to tests on harder, less flexible reference materials (PP and PC) that ended up in the rigid region (>700 MPa).
It was concluded that the new granules should preferably have a flexural strength, measured in accordance with ISO 178:2019, within the range of 2-17 MPa, and preferably 3-8 MPa, and most preferably 4-6 MPa.
It was further concluded that the granules should preferably have a flexural modulus, measured in accordance with ISO 178:2019, of 50-250 MPa, and preferably 55-150 MPa, and most preferably 60-90 MPa.
It was further concluded that the granules should preferably have an offset stretch (0.2%), measured in accordance with ISO 178:2019, of 1-10 MPa, and preferably 2-7 MPa, and most preferably 3-5 MPa.
The density of new granule material was determined to be 1.25 g/cm3 and it has a melting point of 110° C., which is well above the application requirements.
Accelerated weathering tests, performed using the Ci5000 Weather-Ometer apparatus from ATLAS according to the SAE J1960 method, showed no visual erosion or color change for the exposed material at various temperatures, relative humidity's, and UV light intensities.
Preliminary tests on compostability of the new material has also been made, and the preliminary tests indicate. that the granules meet the requirements for compostability according to ISO 20200.
Use of the granules as infill material for an artificial turf system have also been tested. Tests according to the highest playing performance protocol (FIFA Quality Pro) were executed by SPORTS LABS. A 40 mm monofilament turf was used as a carpet together with 8 kg/m2 of the above-discussed granules as an infill to a depth of approximately 17 mm on top of an approximately 10 mm thin layer of silica sand corresponding to 15 kg/m2. As shockpad, a 12 mm thick PE closed-cell foam having a density of 50 kg/m3 was used.
As table 2 shows, excellent playing performance was observed in all tests in both dry and wet conditions. The combination of the new granules-infill, silica sand, carpet and shock pad hence creates an artificial turf system well within the FIFA Quality Pro requirements that is highly appropriate for both outdoor and indoor applications.
Thus, it was found that the new granule, when used as an infill for an artificial turf system, fulfilled all the requirements for both FIFA Quality and FIFA Quality Pro, both in dry and wet conditions. With out wanting to be bound by any theory, it is believed that these excellent results are at least partly due to the relatively low hardness and the great elasticity, verified by the measured flexural properties of the material.
The invention has now been described with reference to specific embodiments. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word “comprising” does not exclude the presence of other elements or steps than those listed in the claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21158469.3 | Feb 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/072993 | 8/18/2021 | WO |
