RETICULAR STRUCTURE AND PROCESS FOR MAKING THE SAME

Abstract

Reticular structure made of material including: a biodegradable polymeric composition in a percentage by weight greater than 90% with respect to the total weight of the material of the reticular structure and a stabilizing additive configured, in use, for reducing the degradation of the reticular structure. A process for making said reticular structure and to a use thereof.

Claims

1.-20. (canceled)

21. A monolithic reticular structure for soil consolidation comprising: a plurality of first elements distanced from each other and having an elongated conformation according to a first trajectory, and a plurality of second elements distanced from each other and having an elongated conformation according to a second trajectory transversal to the first trajectory, wherein the first elements and the second elements intersect at nodes to form a mesh, wherein the monolithic reticular structure is made at least in part of a material comprising a biodegradable polymeric composition which is at least 90% by weight of a total weight of the material of the monolithic reticular structure, and wherein the material also comprises a stabilizing additive configured, in conditions of use of the reticular structure, to delay degradation over time of the monolithic reticular structure.

22. The monolithic reticular structure according to claim 21, wherein the said biodegradable polymeric composition comprised between 92% and 99.5% by weight of the total weight of said material.

23. The monolithic reticular structure according to claim 21, wherein the biodegradable polymeric composition is polybutylene succinate.

24. The monolithic reticular structure according to claim 21, wherein the stabilizing additive in in a range of 0.8% and 6% by weight of the total weight of said material.

25. The monolithic reticular structure according to claim 21, wherein the material consists essentially of: polybutylene succinate constituting substantially 98.5% by weight of the total weight of the material, and the stabilizing additive.

26. The monolithic reticular structure according to claim 21, wherein the stabilizing additive comprises a crosslinking agent.

27. The monolithic reticular structure according to claim 21, wherein the stabilizing additive comprises a crosslinking agent comprising carbodiimide groups.

28. The monolithic reticular structure according to claim 27, wherein the crosslinking agent is at least one of aliphatic or aromatic carbodiimide.

29. The monolithic reticular structure according to claim 21, wherein the first elements are stretched corresponding to a stretching ratio greater than 1.5; the stretching ratio is a ratio between a final length of the first elements after a stretching action thereof and an initial length of the first elements before the stretching action.

30. The monolithic reticular structure according to claim 29, wherein the first elements have a stretching ratio in a range 2 to 8.

31. The monolithic reticular structure according to claim 21, wherein the second elements are stretched, wherein the second elements have a stretching ratio greater than 1.5; the stretching ratio is a ratio between a final length of the second elements after a stretching action thereof and an initial length of the second elements before the stretching action.

32. The monolithic reticular structure according to claim 31, wherein the second elements have a stretching ratio in a range of 2 to 5.

33. The monolithic reticular structure according to claim 21, wherein the stabilizing additive comprises at least one of: an ultraviolet stabilizing additive, or a coloring additive.

34. A grass clod comprising: a soil layer, grass emerging from one side of the soil layer, and the monolithic reticular structure according to claim 21 on or embedded in the soil layer.

35. The grass clod according to claim 34, wherein the soil layer extends in thickness between a first surface and a second surface, wherein the monolithic reticular structure is entirely embedded in the soil layer between the first surface and the second surface.

36. The grass clod according to claim 35, wherein the monolithic reticular structure extends substantially parallel to at least one of a first surface or a second surface of the soil layer.

37. A grass roll wound around an axis and comprising: a soil layer, grass emerging from one side of the soil layer, and the monolithic reticular structure according to claim 21.

38. A grass roll comprising: a soil layer with grass growing from a front side of the soil layer, a monolithic reticular structure on the front side of the soil layer, the monolithic reticular structure includes: a mesh of first longitudinal elements spaced apart from each other and generally aligned along a first direction, and second longitudinal elements spaced apart from each other and generally aligned along a second direction transverse to the first direction, nodes of the mesh are at intersections of the first and second longitudinal elements; the monolithic reticular structure is formed of a material comprising a biodegradable polymeric composition which is at least 90% by weight of a total weight of the monolithic reticular structure and a crosslinking agent, wherein the soil layer and monolithic reticular structure are arranged in a roll.

39. The grass roll of claim 38, wherein the crosslinking agent includes carbodiimide groups.

40. The grass roll of claim 38, wherein the biodegradable polymeric composition includes polybutylene succinate in a percentage by weight substantially equal to 98.5% of the total weight of the reticular structure.

41. The grass roll of claim 38, wherein the first longitudinal elements are stretched elements, wherein the first longitudinal elements are stretched by a ratio in a range of 2 to 8 of a final length of the first longitudinal elements after stretching and an initial length of the first longitudinal elements before the stretching.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0122] Some embodiments and some aspects of the invention are described hereinafter with reference to the accompanying drawings, provided only for illustrative and, therefore, non-limiting purposes, wherein:

[0123] FIG. 1 shows a reticular structure according to the present invention;

[0124] FIG. 2 shows a possible application on the ground of a reticular structure according to the present invention;

[0125] FIG. 3 is a schematic representation of a process for manufacturing a grass roll using a reticular structure according to the present invention;

[0126] FIG. 4 shows in detail a collecting step of the process for making a grass roll;

[0127] FIG. 5 schematically shows a process of unwinding and placing a grass roll;

[0128] FIG. 6 is a schematic view illustrating a possible manufacturing process of the reticular structure according to the present invention;

[0129] FIGS. 7A and 7B are comparative graphs of test samples;

[0130] FIG. 8 is a further comparative graph of nets of biodegradable material.

DEFINITIONS

[0131] It should be noted that in the present detailed description, corresponding parts illustrated in the various figures are indicated by the same reference numerals. The figures may illustrate the object of the invention by representations that are not in scale; therefore, parts and components illustrated in the figures relating to the object of the invention may relate solely to schematic representations.

[0132] In the following description and in the claims, the term advancement direction (MD) refers to a direction of movement of a starting semi-finished product formed by an extrusion station and which proceeds along an advancement path through a cooling station, optionally a stretching station and then up to a collection station.

[0133] The advancement direction, in the technical sector, is also called machine direction.

[0134] The term biodegradable means a material (of natural or synthetic origin) capable of degrading over time, optionally through enzymatic processes, for example by the action of bacteria, fungi or by interaction with other microorganisms.

[0135] The term stretched in relation to first and/or second elements (3, 4) of the reticular structure (2) object of the present invention means a process which allows said elements to be lengthened so as to arrange the molecular chains that form the latter (said first and/or second elements 3, 4) according to an orientation markedly oriented along an extension trajectory of the elements themselves. Depending on the stretching degree, the elements can have a more or less thin structure, being able to assume a substantially threadlike conformation. As will be better described below, the stretching is carried out starting from a monolithic semi-finished product with a reticular structure having first precursor bodies substantially spaced from each other intersected with second precursor bodies also substantially spaced from each other: the first and second precursor bodies essentially form a square or rectangular mesh net in which at least the first precursor bodies can, in a non-limiting manner, extend parallel to the extrusion direction. The stretching ratio is also defined as the ratio of a stretched element and the length of the relative precursor body suitable for defining, following the stretching action, said stretched element. In detail, the stretching ratio of the first elements is defined as the ratio between a final length of the first elements after a stretching action thereof and an initial length of the first elements before stretching; the stretching ratio of the second elements is defined as the ratio between a final length of the second elements after a stretching action thereof and an initial length of the second elements before stretching.

[0136] The term compounding means a process which allows preparing a composition by mixing solutions and additives in the molten state to obtain a solid compound in granular form made with said composition and therefore having predetermined features. The granular solid compound is then used in an extrusion process to create reticular structures, for example nets.

[0137] The reticular structure object of the present invention is made by means of an extrusion process using a solid compound in granular form whose composition is obtained by mixing, inside a feeder, a predetermined amount of polybutylene succinate (PBS), optionally added with a stabilizing additive; once the composition has been correctly mixed to obtain a uniform composition, it is sent to an extruder. The extruder by means of a worm screw is configured for compressing the material and guide it out through a die from which the composition comes out in the form of long threads; the threads are then cooled in a water bath, or by spraying. The cooled threads are then sent, for example by means of a conveyor belt, to a granulator configured for breaking the threads into the desired dimensions to generate the solid compound in granular form (also called compound).

[0138] Definition and measurement of the degradation parameter A first test sample, made of said material and which has not undergone any biodegradation (and which is therefore perfectly intact), is subjected to breakage tests and the relative percentage elongation at break AR.sub.1 of such first test sample is measured according to the method set out in the ISO 527-3 standard. A second test samples, identical to the first test samples, is subjected to the biodegradation process defined by the ASTM G160-12(2019) standard for a period of 7 months. At the end of this period, the second test sample is subjected to breaking tests and the relative percentage elongation at break AR.sub.2 of this second test sample is measured according to the method set out in the ISO 527-3 standard.

[0139] The value of the degradation parameter is then defined as a ratio AR.sub.1/AR.sub.2 between the percentage elongation at break AR.sub.1 of the first test sample as measured above and the percentage elongation at break AR.sub.2 of the second test sample (measured after said biodegradation of 7 months).

[0140] As mentioned above, the degradation process is based on the method set out in the ASTM G160-12(2019) standard. The process involves the use of dumbbell-shaped samples, cut from sheets. Such samples are exposed to the soil under laboratory-controlled conditions. The soil is inoculated with 2% (based on dry weight) of fresh compost or alternatively obtained from an industrial composting plant that treats the organic fraction of municipal solid waste. The containers (40?16?18 cm) used to contain the underground samples were incubated at constant temperature (25?2? C.) and relative humidity (90?5%). The soil moisture content was kept constant (at 80% of water holding capacity) by spraying demineralized water to correct any evaporation during incubation. The samples were recovered from the soil at regular intervals, for this purpose 6 replicate samples were used to collect a certain amount of data.

DETAILED DESCRIPTION

Reticular Structure

[0141] Reference numeral 2 indicates a reticular structure which can be used for consolidation or to promote soil compaction. The reticular structure 2 can also be used for the protection of plants in the growth phase, the packaging of plants, the packaging of perishable materials (fruit, vegetables), the production of anti-erosive mats, nets for floriculture. More generally, the reticular structure 2 finds application for uses in which the presence of the reticular structure 2 is requiredfor example for consolidation and/or protection and/or reinforcement purposesfor a predetermined period of time and in which it is preferable that there is a biodegradation of the same following the useful period of the reticular structure 2. By useful period it is meant the time period during which it is necessary that the reticular structure is substantially intact and suitable for correctly performing the required function, i.e. for purposes of consolidation and/or protection and/or for reinforcement.

[0142] As can be seen from FIG. 1, the reticular structure 2 comprises a plurality of first elements 3 spaced apart and parallel to each other; the first elements 3 are interconnected to a plurality of second elements 4 which are also spaced apart and parallel to each other: the plurality of second elements 4 are placed transversely, in particular orthogonally, to the first elements 3. In detail, each of the first elements 3 extends along the entire reticular structure 2 and is formed by a plurality of portions aligned along the same line. Similarly, each of said second elements 4 also extends along the entire reticular structure 2, transversely to the first elements 3, and is formed by a plurality of portions aligned along the same line: each of the first elements 3 is intersected by a plurality of second elements 4 and each of the second elements 4 is intersected by a plurality of first elements 3 at nodes 5 to form meshes 6. The reticular structure 2 defines a monolithic grid (net), i.e. in a single piece, consisting solely of said first and second elements 3, 4.

[0143] In detail, the first elements 3 have an elongated conformation according to a first trajectory T1 (FIG. 1). The trajectories T1 of the first 3 elements are parallel to each other. Said first trajectories can be straight so as to form first straight and elongated elements along parallel directions. The first elements 3 have, at least at a portion of the center line defined between two immediately consecutive nodes 5 and orthogonally to the first trajectory T1, a section having a substantially elliptical shape. The possibility of making first elements 3 having, at least at a portion of the center line defined between two immediately consecutive nodes 5 and orthogonally to the second trajectory, a section having for example a rectangular, square, circular or T shape, is not excluded. The first elements 3 have a substantially threadlike structure and therefore have a reduced cross section along their entire extension; for example, the first elements 3 may have a cross section, measured at a portion of the center line defined between two immediately consecutive nodes, with an area lower than 5 mm.sup.2, optionally comprised between 0.1 mm.sup.2 and 1.5 mm.sup.2. The cross section remains substantially constant throughout the extension of the first element 3 with an increase in section at the nodes where the first element widens to join with said second elements 4.

[0144] The second elements 4 also have an elongated conformation according to a second trajectory T2. As can be seen in the accompanying figures, the trajectories T2 of the second elements 4 are parallel to each other. The second trajectories T2 can be straight so as to form first straight and elongated elements along parallel directions.

[0145] The second elements 4 have, at least at a portion of the center line defined between two immediately consecutive nodes 5 and orthogonally to the second trajectory T2, a section having a substantially elliptical shape. It is not excluded the possibility of making second elements 4 having, at least at a portion of the center line defined between two immediately consecutive nodes 5 and orthogonally to the second trajectory, a section having for example a rectangular, square, circular or T shape.

[0146] The first and second elements 3, 4 lie substantially on the same plane to substantially define a net with a flat conformation. The second elements 4 have a substantially threadlike structure and have a reduced cross section along their entire extension; for example, the second elements 4 may have a cross section, measured at a portion of the center line defined between two immediately consecutive nodes, with an area lower than 5 mm.sup.2, optionally comprised between 0.1 mm.sup.2 and 1.5 mm.sup.2. The cross section may be constant throughout the extension of the second element 4 with an increase in section at the nodes 5 where the second element 4 widens to join with said first elements 3.

[0147] The ratio between the distance between two first adjacent elements 3 and the distance between two second adjacent elements 4 is comprised between 0.5 and 2, optionally between 0.8 and 1.2. The meshes 6 of the reticular structure 2 are substantially square. Obviously, the possibility of making meshes having a different shape, for example rectangular, triangular or rhomboidal, is not excluded. Quantitatively, the minimum distance between two first adjacent elements 3 is comprised between 4 mm and 200 mm, optionally between 10 mm and 50 mm. Likewise, the minimum distance between adjacent second elements 4 is comprised between 4 mm and 200 mm, optionally between 10 mm and 50 mm. As these distances vary, the dimensions of the meshes 6 vary and may have a through area comprised between 16 mm.sup.2 and 40000 mm.sup.2, optionally comprised between 200 mm.sup.2 and 3000 mm.sup.2.

[0148] The reticular structure 2 can be stretched at least along an extension direction of the first elements 3 and/or of the second elements 4 to define a mono-stretched and/or bi-stretched reticular structure 2; for example, the reticular structure 2 can be stretched along the extension of the first elements 3 only, i.e. along the first trajectory T1. The reticular structure 2 can be stretched along two directions, in particular along the extension of the first and second elements 3, 4 to define a bi-stretched reticular structure as illustrated for example in FIG. 1: in this configuration, the reticular structure is stretched both along the first trajectory T1 and along the second trajectory T2. The stretching ratio, i.e. the ratio between the length of the elements (first elements and/or second elements) after stretching and their length before stretching, is greater than 1.5. In detail, the first elements 3 are stretched along the first trajectory T1; the first elements 3 have a stretching ratio higher than 1.5, optionally comprised between 2 and 8, more optionally between 2.5 and 4.

[0149] The second elements 4 are stretched along the second trajectory T2; the second elements 4 have a stretching ratio higher than 1.5, optionally comprised between 2 and 5, more optionally between 2 and 4. The threadlike structure of the first and second elements 3, 4 is substantially defined by the stretching action which accentuates the elongation of said elements and thinning the cross section thereof.

[0150] The reticular structure 2 substantially has two extension directions (i.e. the directions in which the first element 3 and the second elements 4 extend): the structure 2 has an overall height, or thickness, orthogonal to such extension directions much smaller than the dimensions defined in the two extension directions (for example length and width of the reticular structure 2 to define a reticular structure 2 having a substantially uni-planar shape. The height of the reticular structure 2 is defined by the (maximum) height of the first and/or second elements 3, 4 or by the height defined at the nodes 5. The specific weight of the reticular structure 2 is comprised between 10 g/m.sup.2 and 25 g/m.sup.2 (optionally between 12 g/m.sup.2 and 18 g/m.sup.2).

[0151] The reticular structure has a specific tensile strength, along the first and/or second elements, equal to or greater than 0.5 kN/m, optionally comprised between 0.7 kN/m and 10 kN/m, even more optionally between 0.7 kN/m and 3 kN/m; the specific tensile strength is measured with the method set out in the ASTM D7179 standard.

[0152] The reticular structure 2 is made at least in part of biodegradable material. In particular, the reticular structure 2 is made of a material comprising: [0153] a biodegradable polymeric composition in a percentage by weight higher than 90% with respect to the total weight of the material of the reticular structure; [0154] a stabilizing additive configured, in use, for reducing the degradation of the reticular structure (2).

[0155] The reticular structure 2 may comprise a percentage by weight of said biodegradable polymeric composition comprised between 92% and 99.5%, optionally between 95% and 99%, with respect to total weight of the material of the reticular structure. The biodegradable polymer composition may comprise polybutylene succinate; in particular, the biodegradable polymeric composition of the material of the reticular structure 2 consists solely of polybutylene succinate (polymeric composition consisting of 100% polybutylene succinate).

[0156] The stabilizing additive may be comprised in a weight percentage comprised between 0.8% and 6%, optionally of between 1% and 3% with respect to the total weight of said material. The reticular structure 2 may be made of a material comprising: [0157] polybutylene succinate in a percentage by weight substantially comprised between 98% and 99%, optionally 98.5%, with respect to the total weight of the material of the reticular structure; [0158] the stabilizing additive, how much is missing to reach 100% by weight of the material of the reticular structure, optionally the stabilizing additive is substantially equal to 1.5% by weight, with respect to the total weight of the material of the reticular structure.

[0159] In detail, the stabilizing additive may comprise a crosslinking agent, for example selected from the group comprising carbodiimide groups. Crosslinking agents comprising carbodiimide groups have the following general formula:

##STR00001##

wherein R1 and R2 independently consist of a hydrogen atom, aliphatic, saturated or unsaturated hydrocarbons, having from 1 to 10 carbon atoms and/or aromatic hydrocarbons having from 6 to 16 carbon atoms. R1 and R2 independently consist of linear, cyclic or branched alkyl, alkenyl, aryl, aralkyl, aralkenyl groups, optionally substituted with a halogen atom, a primary, secondary or tertiary amino group, an ester group, a sulfate or sulfonate group, or a ketone group. One or both of the R1 and R2 groups may contain a further carbodiimide group, so as to form an oligomeric or polymeric carbodiimide. Preferably, the carbodiimide used in the present invention is soluble or dispersible in water, but aqueous dispersions of water-insoluble carbodiimides may also be used.

[0160] The carbodiimide can be selected from the group consisting of ethyl dimethylaminopropyl carbodiimide (EDC-HCl); 1,3-di-p-tolylcarbodiimide 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide; 1,3-diisopropylcarbodiimide; 1,3-dicyclohexylcarbodiimide; 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide methyl-p-toluenesulfonate; 1-tert-butyl-3-ethylcarbodiimide; 1,3-dicyclohexylcarbodiimide; 1,3-bis(trimethylsilyl) carbodiimide; 1,3-di-tert-butylcarbodiimide; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide methyldide; and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0161] Carbodiimides are commercially available under the brand name Ucarlink? from Union Carbide company (e.g. Ucarlink? XL-29SE and Ucarlink? XL-20), under the brand name Carbodilite? from Nisshinbo Industries, Inc. (for example Carbodilite? HMV-15CA and Carbodilite? V02-L2), and with the brand name Nexoll from the company Euro-Chemical (for example Nexoll CDI B/S).

[0162] In detail, the material of the reticular structure 2 is biodegradable; the biodegradability of said material is such that the value of the degradation parameter is lower than 20, optionally comprised between 1 and 10, even more optionally comprised between 1, 2 and 5; the degradation parameter is identified and measured as defined in the description.

[0163] In fact, the degradation parameter is representative of how the material with which the reticular structure 2 can be made allows it to keep its mechanical features substantially constant, for a predetermined period of use, so that the reticular structure made by means of said material can correctly perform its function (for example of containment and/or protection). FIG. 7A illustrates by way of example the trend of the breaking strength of a test sample made of the material described above for the reticular structure (i.e. polybutylene succinate with stabilizing additive) and according to the dictates of the ISO 527-3 standard; this test sample was also subjected to a biodegradation process according to the ASTM G160-12 (2019) standard for a period of 15 months. As can be seen from FIG. 7A, the variation in the breaking strength over time of the test samplemade of the material of the reticular structure 2 [i.e. polybutylene succinate (identified with the abbreviation PBS) with stabilizing additive] is minimal, lower than 20%, optionally between 1% and 10%. The breaking strength of said test sample seems to stabilize in the period between 10 and 15 months.

[0164] As can be seen from FIG. 7A, test samples made according to the dictates of the ISO 527-3 standard, but made of different materials (polybutylene succinate PBS without additives or polybutylene succinate adipate PBSA without additives), when subjected to the same biodegradation process mentioned above, show important variations in the breaking strengthin the order of 100%already after a duration of the biodegradation process, equal to 2 months.

[0165] The same results are visible in FIG. 7B, in which the percentage elongation at break of samples made according to the dictates of the ISO 527-3 standard and subjected to the biodegradation process described above are compared. As can be seen, the material (polybutylene succinate+stabilizing additive) of the reticular structure 2 has a degradation parameter variation lower than 20, optionally between comprised 1 and 10, even more optionally between 1.2 and 5; wherein the degradation parameter is defined (as described above) as a ratio AR.sub.1/AR.sub.2 between the percentage elongation at break AR.sub.1 of the first test sample as measured above and the percentage elongation at break AR.sub.2 of the second test sample (measured after said biodegradation of 7 months). In fact, said polymeric composition (polybutylene succinate+stabilizing additive) allows the test sample subjected to the biodegradation process mentioned above to maintain a certain structurality, so that said test sample may have in the long term (for example up to 15 months) excellent mechanical features and in particular low fluctuations in the percentage elongation at break.

[0166] In fact, such material (polybutylene succinate+stabilizing additive) is such that a test samples according to the ISO 527-3 standard is subjected to the biodegradation process defined by the ASTM G160-12 (2019) standard for a period longer than 2 months, optionally longer than 7 months, even more optionally comprised between 8 and 15 months, may maintain structural continuity along the entire extension of said test samples. Moreover, said material is such that a test sample according to the ISO 527-3 standard is subjected to the biodegradation process defined by the ASTM G160-12 (2019) standard for a period longer than 20 months, optionally longer than 16 months, does not maintain structural continuity throughout the extension of said test sample. In detail, the test sample, as defined in the ISO 527-3 standard, extends between a first and a second end; this test sample subjected to the biodegradation process defined by the ASTM G160-12 (2019) standard for a period longer than 20 months, optionally longer than 16 months, is configured for defining a separation between said first and second ends. In other words, said test sample subjected to the biodegradation process defined by the ASTM G160-12 (2019) standard for a period longer than 20 months, optionally longer than 16 months, is configured for exhibiting such biodegradation as to define a complete separation of said first and second ends.

[0167] FIG. 8 instead illustrates the trend of the percentage elongation at break of two identical reticular structures.

[0168] The trend of the percentage elongation at break of the reticular structure 2 made by means of a material according to the present inventionor made of a material comprising a biodegradable polymeric composition (in particular polybutylene succinate) and at least one stabilizing additive and subjected to a biodegradation process according to the aforementioned standard (ASTM G160-12 (2019) is schematized with a continuous line; as can be seen, the substantially constant trend of the percentage elongation at break of the test sample [made of polybutylene succinate+stabilizing additive) subjected to the biodegradation process according to the aforementioned standard (ASTM G160-12 (2019)] shown in FIG. 7A is reflected in the substantially constant trend of the percentage elongation at break of a reticular structure 2 made of a material comprising a biodegradable polymeric composition (in particular polybutylene succinate) and at least one stabilizing additive. The greater variation over time of the percentage elongation at break of a reticular structure made entirely of polybutylene succinate (without additive) and subjected to the biodegradation process according to the aforementioned standard (ASTM G160-12 (2019)) is also shown.

Manufacturing Process

[0169] The present invention also relates to a process for manufacturing a reticular structure 2 according to the above description and/or according to any one of the accompanying claims.

[0170] The process involves the realization of the first and second elements 3, 4 by means of an extrusion process (simultaneous extrusion of the first and second elements 3, 4), optionally by means of a pulsating technology. It is not excluded the use of an extrusion head that uses a counter-rotating technology. The extrusion head is fed by means of a solid compound in granular form made by means of a known compounding technology. The solid granular compound is made of a biodegradable material, for example polybutylene succinate (PBS) optionally added with a stabilizing additive, used to make the material of the reticular structure 2.

[0171] The extrusion process, schematically represented in FIG. 6, involves the simultaneous extrusion of first and second precursor bodies by means of an extrusion head 100; the first precursor bodies are longitudinal elements that extend along an extrusion direction E (therefore along an advancement direction MD of the extruded material exiting the head 100) while the second precursor bodies are elements transversal to the first precursor bodies: first and second bodies precursors forming a monolithic reticular integral body. The advancement direction MD is also recognized in the sector as the machine direction, i.e. the direction in which the apparatus for the extrusion and formation of the reticular structure allows the latter advance.

[0172] The extrusion step is executed at a temperature comprised between 110? C. and 180? C., optionally comprised between 150? C. and 175? C.; the material exiting the extrusion head is advanced at a speed comprised between 5 meters/minute and 12 meters/minute, optionally comprised between 6 meters/minute and 10 meters/minute. The extrusion can be executed with a cylindrical head suitable for forming a reticular structure having a cylindrical shape.

[0173] Subsequently, such reticular structure exiting the extrusion head is cooled to be cut longitudinally to then be opened and spread flat. FIG. 5 illustrates a cutting station 101 of the cylindrical reticular structure and a subsequent distension station 102 in which the open reticular structure is spread on a single plane. The spread reticular structure can define the reticular structure 2 having first and second unstretched elements. This structure, once spread, is ready to be rolled up in a collection station (not shown). Alternatively, after the formation of the monolithic integral body, the latter can undergo a stretching process.

[0174] The reticular structure exiting the extrusion head defines a monolithic semi-finished product with a reticular structure having first and second precursor bodies spaced apart and interconnected to essentially define a semi-finished product in the form of a net. In one embodiment, the semi-finished product is extruded by means of a head which uses a pulsating technology; the first precursor bodies extend along the extrusion direction while the second precursor bodies extend orthogonally to said first precursor bodies to define a square or rectangular mesh semi-finished product.

[0175] Subsequently, such monolithic semi-finished product with a reticular structure exiting the extrusion head is cooled to be cut longitudinally, i.e. along the extension direction of the first precursor bodies to then be opened and spread flat. FIG. 6 illustrates a cutting station 101 of the monolithic semi-finished product with a reticular structure and a subsequent stretching station 102 wherein said semi-finished product is spread on a single plane. When lying flat, the first precursor bodies define longitudinal bodies extending along the advancement direction MD while the second precursor bodies define transverse bodies placed orthogonally to the advancement direction.

[0176] The semi-finished product, when stretched, can be stretched along the first and/or second precursor bodies.

[0177] The process can, for example, carry out the step of stretching only the first precursor bodies or only the second precursor bodies to define a mono-stretched reticular structure 2. Alternatively, the manufacturing process can provide for a double stretching action, i.e. both along the extension of the first precursor bodies and along the extension of the second precursor bodies to define a bi-stretched (or also called bi-oriented) reticular structure.

[0178] In the accompanying figures, a process which provides for the stretching of both the first and second precursor bodies has been illustrated, in a non-limiting manner. For example, the process can provide for a first stretching action of the first precursor bodies in a longitudinal stretching station 103 placed immediately downstream of the stretching station. The stretching of the first precursor bodies defining said first stretched elements 3 can be executed by means of the movement of the semi-finished product along the advancement direction at a speed greater than that of extrusion to allow an elongation of the semi-finished product along the machine direction; for example, the stretching speed of the first precursor bodiesdefining said first stretched elements 3is carried out, along the advancement direction MD, at a speed comprised between 23 meters/minute and 27 meters/minute. During the stretching step, the semi-finished product is heated to a temperature comprised between 65? C. and 110? C. In particular, the stretching step of the first precursor bodies is executed, optionally in a water bath, at a temperature comprised between 75? C. and 90? C. Of course, the possibility of stretching the first precursor bodies is not excluded even when the semi-finished product with a reticular structure is in its circular shape or before the cutting step.

[0179] The process can also involve for a second stretching action performed on the second precursor bodies in a transversal stretching station 104 placed downstream of the stretching station, in particular immediately downstream of the longitudinal stretching station 103. The stretching of the second precursor bodies for defining said second stretched elements 4 can be performed by means of a pulling step, for example by gripping pliers, of the semi-finished product with a reticular structure according to a direction orthogonal to the advancement direction. The stretching speed of the second precursor bodiesfor defining said second stretched elements 4is executed at a speed comprised between 4 meters/minute and 30 meters/minute, optionally comprised between 8 meters/minute and 20 meters/minute. The step of stretching the second precursor bodies is executed, optionally in a casing inside which there is heated air, at a temperature comprised between 85? C. and 110? C. It is not excluded that the step of stretching the second precursor bodies can be executed before stretching the first precursor bodies. Following the formation of the reticular structure and therefore of the first and second elements 3, 4 (optionally stretched), the reticular structure is subsequently cut transversely to the first elements according to a predetermined length, measured in the direction of the first elements 3 to define said reticular structure 2. The reticular structure 2, before the cutting step, can be wound in a roll in a collection station.

[0180] Further manufacturing systems are possible and are evident for those skilled in the art of extrusion, such as starting from a flat extrusion head to make a sheet which will then be subjected to the cold drilling and ironing steps to obtain of the reticular structure 2.

Grass Clod

[0181] The present invention also relates to a grass clod 1 comprising a reticular structure 2 as described above and/or according to any one of the accompanying claims.

[0182] The grass clod 1 comprises a soil layer S, a predetermined quantity of grass G emerging from one side of the soil layer and at least a reticular structure 2 housed at least partially in the soil layer. The reticular structure 2 is configured, in use, for consolidating at least the soil layer; the soil layer extends in thickness between a first and a second surface, optionally the thickness of the soil layer S is greater than 0.5 cm, optionally it is comprised between 0.65 cm and 2.5 cm; the grass clod has a surface extension greater than 0.25 m.sup.2, optionally it is comprised between 0.25 m.sup.2 and 1.5 m.sup.2.

Process for Making a Grass Clod

[0183] The present invention also relates to a process for making a grass clod 1 comprising a reticular structure 2 as described above and/or according to any one of the accompanying claims.

[0184] The process comprises a first step of laying the reticular structure 2 on a soil portion. In detail, the reticular structure in roll form is unrolled and then spread over the soil portion. The reticular structure 2 can therefore be arranged above (resting on) the exposed surface of the ground or it can be pressed onto the ground in such a way that at least part of said reticular structure 2 can immerse itself in the ground, remaining in any case in proximity to the exposed surface. Following the laying (spreading) of the reticular structure 2, the process comprises a step of sowing the soil by laying grass seeds. After sowing, the grass follows the normal growth process which can last, for example, depending on the conditions and treatments of the soil, from 6 months to 14 months. During the growth step of the grass, the reticular structure is configured for being incorporated into the soil layer and to the grass for allowing the consolidation of the soil. Following the growth of grass on the soil portion, the process provides for a cutting step in the soil to delimit a grass clod. The grass clod thus cut is then collected. The grass clod thus created is then ready to be laid on a ground for making a turf.

Grass Roll

[0185] The present invention also relates to a grass roll R comprising a reticular structure 2 as described above and/or according to any one of the accompanying claims.

[0186] The grass roll R is wound around an axis in a spiral pattern (see for example FIGS. 3 and 4) and comprises a soil layer S, a predetermined amount of grass G emerging from one side of the soil layer and at least one reticular structure 2 engaged to the soil layer. The reticular structure 2 is configured, in use, for consolidating at least the soil layer S; the soil layer S extends in thickness between a first and a second surface, optionally the thickness of the soil layer is greater than 0.5 cm, optionally it is comprised between 0.65 cm and 2.5 cm. The grass roll R, completely unwound and arranged on a plane, has a length of between 1 meter and 40 meters; said length being measured along an unwinding direction of the same grass roll R. The roll R has a width equal to or greater than 0.6 meters, optionally comprised between 0.6 meters and 2 meters; said width being measured along the axis around which said grass roll is wound.

Process of Making a Grass Roll

[0187] The present invention also relates to a process for making a grass roll comprising a reticular structure 2 as described above and/or according to any one of the accompanying claims.

[0188] The process for making the roll is schematically shown in FIG. 3. This process comprises the same steps of spreading the reticular structure 2 and sowing described above for the grass clod. Following the growth of grass on the soil portion, the process involves a cutting step in the soil to delimit a grass clod along an extension direction. The grass clod thus cut is then placed by means of a rolling action of the clod (see for example FIG. 4) around an axis orthogonal to the extension direction to define said grass roll. The grass roll thus created is then ready to be unwound on a ground for the making a turf. The unrolling (opening) process of the roll is schematically shown in FIG. 5.

Advantages

[0189] The present invention entails, compared to the solutions of the prior art, considerable advantages. In particular, the reticular structure 2 made of at least partly biodegradable material is suitable for performing numerous uses. The reticular structure 2 in fact has excellent physical/mechanical properties and reduced construction costs; furthermore, the fact that the reticular structure 2 has the aforementioned features allows producing grass clods and/or grass rolls that are extremely stable and therefore easier to collect and transport. In detail, the reticular structure, by virtue of its material, is suitable for not degrading during the growth period of the grass so as to maintain its mechanical features and therefore consolidate the soil correctly; the reticular structure 2 is also configured for degrading after a predetermined period of time, generally following the growth of the grass and the collection and subsequent installation of the grass clod or roll. In fact, the material used allows the reticular structure 2 to be highly preforming in terms of consolidation of the ground (grass clods or grass rolls) but at the same time to be biodegradable and therefore not negatively impacting the environment. The material used for the reticular structure 2 allows it to degrade in a controlled manner after a predetermined period.

[0190] The reticular structure 2, by virtue of the material of the reticular structure, is also processable even by means of the most delicate production processes such as extrusion by means of a pulsating head. It should be noted that often, the extrusion with a pulsating head is preferable to counter-rotating extrusion heads because it allows obtaining a semi-finished product having square or rectangular meshes in which an order of elements (for example the first precursor bodies adapted to define said first elements 3) extends along the extrusion direction E and therefore of advancement of the semi-finished product along the steps of the production process and an order of elements (for example the second precursor bodies suitable for defining said second elements 4) placed orthogonally to said extrusion direction E/advancement of the semi-finished product; the semi-finished product thus constituted is more easily subjected to a stretching action of the material and moreover it is more controllable in the stretching ratios since the first and second precursor bodies are respectively placed substantially parallel and orthogonally to the advancement direction of the semi-finished product.