WO2017033159A1

WO2017033159A1 - Procedure for the production of arrangements of foamed polymer particles; arrangements of foamed polymer particles and relative articles

Info

Publication number: WO2017033159A1
Application number: PCT/IB2016/055110
Authority: WO
Inventors: Sergio Brunetti; Damiano CHIMINELLO
Original assignee: Artitec Srl; API Applicazioni Plastiche Industriali SPA
Current assignee: Artitec Srl; API Applicazioni Plastiche Industriali SPA
Priority date: 2015-08-26
Filing date: 2016-08-26
Publication date: 2017-03-02
Anticipated expiration: 2018-02-26
Also published as: ITUB20153233A1

Abstract

The invention refers to a process for the production of arrangements of foamed polymer particles, in particular sheets of foamed polymer particles, in which the particles are arranged in a compact order and mutually connected. The process comprises the following steps: preparing foamed polymer particles (101; 201 ) coated at least partially on the surface by a binding agent not yet activated; distributing (20) a determined amount of the particles on a surface until obtaining an arrangement of particles as a compact packing, in the two- dimensional case preferably with a packing density of > 0.70, more preferably > 0.75, even more preferably > 0.78, and most preferably > 0.90, and in the three-dimensional case preferably with a packing density of > 0.6, more preferably > 0.625; activating (22) the binding agent to connect the particles thus arranged to each other and fix the arrangement obtained. The invention further refers to a mono- or multilayer sheet that can be produced with said process and related articles, such as protections, saddles or elements for the building industry.

Description

PROCEDURE FOR THE PRODUCTION OF ARRANGEMENTS OF FOAMED POLYMER PARTICLES; ARRANGEMENTS OF FOAMED POLYMER PARTICLES AND RELATIVE ARTICLES.

DESCRIPTION

Technical field of the invention

The invention relates to a process for the production of arrangements of foamed polymer particles, in particular for the production of foamed polymer sheets, the relative arrangement or sheet and articles produced therewith. In particular, the arrangement finds application, for example also in the form of inlays, in padding for seats, impact protections, saddles for bicycles or motorcycles, sound-absorbing and/or heat-absorbing elements for the building industry, items of clothing and in shoe soles and insoles.

Prior art

For applications in padding for seats, impact protections, saddles for bicycles or motorcycles, items of clothing and shoe soles and insoles, a shock- absorbing material is required and a sound-absorbing and/or heat-absorbing material is required for building applications. A high breathability of the material is desirable for both groups of applications. In footwear, for example, soles and insoles are known which comprise materials of foamed polymer particles. The production of such soles, insoles or parts thereof usually takes place by molding, as described for example in documents US 2014/0223777 A1 , US 2014/0223783 A1 , US 2014/0223776 A1 and US 2014/0223673 A1 . In all of the documents cited, the particles are arranged randomly within the material, as a result of a deposition of particles in a mold, and they do not have a particular order. The proposed materials are not satisfactory from the point of view of breathability, and precisely from the point of view of a uniform breathability throughout the material.

The prior art knows some documents, such as EP 1 502 726 A1 , WO 93/16129 A1 , WO 2005/037537 A1 , EP 0 401 838 A1 , US 2005/0124708 A1 and CA 2 769 075 A1 , which describe particle arrangements and methods for the production thereof in which the interstices between the particles are at least partially filled and not empty, thus resulting in a non-satisfactory breathability. Only document WO 2005/037537 A1 refers to the breathability of the material, but the description does not sufficiently show how to obtain arrangements with uniform breathability features. None of the documents describes the use of particle arrangements for shoe soles.

Disclosure of the invention

The object of the invention is to propose a process for the production of materials of foamed polymer particles which have an essentially uniform breathability throughout the material and which at the same time have sound- absorbing and/or heat-absorbing features and/or shock-absorbing features in reaction to impacts. Breathability is understood as permeability to water vapor. A further object of the invention is to propose a relative material, in particular a sheet of foamed polymer particles.

The above objects, other objects and advantages which will be better apparent hereinafter are achieved by a process as defined by the first claim, and precisely by a process for the production of arrangements of foamed polymer particles, in particular of sheets of foamed polymer particles, wherein the particles are connected to each other and mutually fixed in their position within the arrangement, which comprises the following steps:

(a) preparing foamed polymer particles coated at least partially on the surface by a binding agent not yet activated;

(b) distributing a determined amount of said particles in two dimensions or in three dimensions on a surface, preferably on a continuous conveyor belt, up to obtain an arrangement of particles as a compact packing, in the two-dimensional case preferably with a packing density of > 0.70, more preferably > 0.75, even more preferably > 0.78, and most preferably > 0.90, and in the three-dimensional case preferably with a packing density of > 0.6, more preferably > 0.625;

(c) activating said binding agent to connect the particles thus arranged to one another and fix the arrangement obtained in step (b); and optionally

(d) a further compaction of the particle arrangement by compression.

Advantageously, the process produces a compact arrangement of the particles that comprises zones in which the particles are arranged in a regular manner. The compact and at least partially regular or essentially regular order ensures a more uniform distribution of the interstices between the particles and consequently a more uniform breathability through the whole arrangement of particles with respect to the arrangement of particles in the prior art as cited above. In the case of spherical particles, the compact order may comprise zones with hexagonal packing of the particles. Preferably, the particles comprise one or more of the following cross-sectional profiles: annular, oval, polygonal, circular or elliptical. Particularly preferred are particles with circular sections, such as spheres, or essentially circular sections, such as ellipsoids.

Moreover, in the semi-finished product obtained by the process according to the invention, also the following features are essentially uniform: density, hardness and rebound of the material. The sound-absorbing or heat-absorbing features are also uniform.

If the surface for example is a conveyor belt, the arrangement obtainable by the process according to the invention is a sheet.

Preferably, the surface, and in particular the conveyor belt, comprises boundaries to contain the particles. In the case of the conveyor belt, said boundaries advantageously are walls or sides which extend in the longitudinal direction along the edges of the belt. The boundaries are adapted to prevent an escape of the particles from the belt and preferably extend essentially perpendicular with respect to the belt. Moreover, the boundaries help create a high compactness and regularity in the arrangement of the particles. The boundaries allow the determination of a predetermined width of the particle arrangement as a layer or sheet. In a preferred variant of the invention, the conveyor belt is a roller shutter belt. For the production of two-dimensional particle arrangements in which the particles are arranged with great regularity, and precisely with a coordination number 4 or 6, as shown in figures 4a and 4b, it is advantageous to use a pin structure on the belt, as shown in figures 6a and 6b, to impart regularity to the arrangement.

The surface may also be the bottom of a container.

Advantageously, the surface is tilting, for example in multiple directions, to be able to tilt the surface during the process also in different directions.

The binding agent preferably does not alter the size of the particles during its activation. As binding agents, glues may be used or also functional groups anchored on the surface of the particles that in chemical reactions bind to one another, for example by means of crosslinking reactions, in the case of polymerizable functional groups. Binding agent is also understood as the material of the particle itself, when melted on the surface. This melting is often accompanied by the deformation of the particle.

In a highly preferred variant of the invention, the binding agent is a glue. The fact that particles are bonded together and not connected, for example by melting prevents the deformation thereof and ensures constant dimensions thereof, an important fact for a regular or at least partially regular packing. The use of glue as a binding agent allows obtaining sufficient breathability of the material, and this also in the case of a further compaction of the particle arrangement by compression (step (d) of the process). The connection of the particles through melting can impair the breathability of the material.

Advantageously, the glue is a water-based polyurethane glue. Preferred glues are biodegradable and/or recyclable. The glue may be thermoplastic or thermosetting. However, preferably, the type of glue is selected based on the polymeric material to be bonded. Particularly preferred are thermoplastic glues. Thermoplastic glues ensure very satisfactory results in terms of breathability of the material.

In order to improve the adhesion between the particles after the activation of the binding agent, it is possible to carry out, in a variant of the invention, a further hot-sintering of the particles by fusion. This sintering can result in a modification of the particle geometry, but does not significantly alter the relative position of the particles. This sintering causes a reduction in the breathability of the material.

The breathability of the arrangement of particles, advantageously, is also controlled by selecting the compression degree (step (d) of the process according to the invention) and/or diameter and/or shape of the particles.

In a preferred variant of the invention, the activation of the binding agent in step (c) occurs through heating. An activation via heating is easily achievable and does not require complex instruments. Of course, depending on the type of binding agent chosen, other types of activation of the binding agent may also be contemplated, such as radiation, for example by light, water, oxygen, radical activations, etc. In the case of a glue as a binding agent, heating activation is particularly preferred.

Advantageously, step (a) of the process according to the invention uses a glue as a binding agent and further comprises the following steps:

(a1 ) preparing foamed polymer particles, preferably dried;

(a2) distributing glue on the particle surfaces;

(a3) drying the glue without activating it;

(a4) where necessary, separating the particles; and optionally (a5) preheating the particles provided with glue without activating the glue. The drying process serves to eliminate moisture in the material which may result from the polymer production process or from absorbing any ambient humidity.

Preferably, the glue distribution takes place with a mechanical process. Such a mechanical process may be, for example, a mechanical rotation of the particles with an amount of glue into a container, as is the case for example in the production of sugared almonds or peanuts. A controlled dosage of the amount of glue is preferred to ensure uniform thickness of the particle coating with glue.

A separation of the particles is necessary when agglomerations are formed in order to allow depositing single particles on the surface and an independent movement of each particle, for example during the vibration of the surface which represents an embodiment variant of the process that will be described hereinafter.

Advantageously, the separation of particles takes place mechanically. Step (a4) may take place, for example, in a contactless grinder that is provided with two discs rotating in the opposite direction.

The optional preheating of particle with glue without activating the glue allows speeding up the arrangement of particles, for example in the form of a sheet. Drying preferably is not forced, therefore it takes place for example at room temperature, so as not to alter the features of the glue and not to induce the crosslinking thereof.

Step (a5) takes place at a temperature lower than the glue activation temperature. If the glue activation temperature is, for example, about 90°C, preheating can take place, for example, at about 70°C. In this way, glue is not activated and the production speed increases.

Preferably, in order to activate the glue it must be heated at least at the activation temperature of the glue. To this end, the arrangement of particles can be introduced into a furnace where particle gluing will start, so as to set the arrangement and form, for example, the sheet.

In variants of the invention, the particles in the arrangement are arranged in only two dimensions, or in three dimensions. In the case of a two-dimensional arrangement, you have a monolayer sheet, i.e. a single layer of particles with a height that matches the diameter of the particles, while in the case of a three- dimensional arrangement, the particles are arranged also one on top of the other, occupying the third dimension as well. The height of the arrangement thus exceeds the diameter of the particles. In order to create multilayered sheets as will be described hereinafter, sheets are preferred in which the particles are arranged in only two dimensions.

In a preferred variant of the invention, the foamed polymer particles are subjected, preferably before applying the binding agent, to one or more sieving. The sieving allows obtaining particles that have a predetermined particle size distribution. The more uniform the particle sizes, the more regular the particle arrangement.

In a preferred variant of the invention, the distribution of a predetermined amount of said particles in two dimensions or three dimensions on a surface takes place with a dispensing and positioning device which dispenses one or more particles and arranges the particles respectively individually, or in groups randomly or in predetermined positions on the surface in which, in the case of random positioning, the surface is already vibrating with or after the particle distribution on the surface and in which, in the case of positioning in predetermined positions, regular coordination numbers for particles are observed.

In particular, in the case of particle positioning in predetermined positions, pins are advantageously located on the belt which extend perpendicular to the belt surface. Preferably, the pins are arranged according to a regular order, for example so that the pins form equidistant lines in which the pins represent the angles of equilateral triangles or squares, so that a particle is inside the triangle (creating a hexagonal arrangement layer, i.e. with coordination number 6) or the square (coordination number 4).

Predetermined positions correspond to arrangements as shown in figures 4a and 4b, i.e. to two-dimensional compact arrangements with coordination number 4 or 6. Each particle is coordinated by an equal number of other particles, and thus has a predetermined coordination number. Particularly preferred are known arrangements of crystal lattices of metals, salts and minerals.

In a preferred variant of the invention, the particles are essentially spherical, in particular for highly regular arrangements obtainable by positioning in predetermined positions. Advantageously, the particles have essentially equal dimensions with a tolerance < ± 25%, preferably < ± 15%. In the case of positioning in predetermined positions, the lower tolerance is preferable for the diameter.

Preferably, the particles have diameter ranging between 3.0 and 9.0 mm.

An ideal breathability, e.g. for the use of the material in soles or insoles, can be obtained with a material obtained with a random positioning of the particles on the belt and with a vibration of the belt when the particles are not perfectly spherical and hence when the particles have cross sections that slightly deviate from the circular shape and are closer to an ellipse. The expression "essentially spherical" should be understood to include particles whose elliptical section profiles are characterized by a semi-major axis and by a semi- minor axis in which the length of the semi-major axis does not exceed the length of the semi-minor axis by more than 25%, preferably by more than 15%, yet more preferably by more than 10%. In the case of a non-ideal sphere, the term "diameter" includes the aforesaid semi-axes and it is thus the extension of the particle that preferably corresponds in every direction in space to values included between 3.0 mm and 9.0 mm. The extension of the particle in the three directions included between 3.0 mm and 9.0 mm is also preferred for non-spherical or essentially spherical particles; the same holds true for the tolerances that indicate the range within which the dimensions of the particles may vary to assure that they are essentially equal in their dimensions. Particles with perfect spherical shape entail an at least nearly ideal arrangement of the particles, such as hexagonal or cubic packing in metals, and consequently reduced breathability compared to less regular arrangements. Advantageously, an additional compression according to step (d) of the process according to the invention does not alter in a significant manner the essentially spherical or ellipsoidal geometry of the particles. In order not overly to reduce breathability, a compression deforms the foamed polymers only slightly, essentially maintaining the mutual order of the particles reached in step (b) of the process according to the invention, inasmuch as the particles are mutually fixed with the binding agent in their position.

The essentially spherical shape of the particles and the essential uniformity of the dimensions allows at least partially regular packing. The maximum packing, achievable in parts of the arrangement or sheet where the geometry of the particles closely approaches the ideal spherical shape, would be a regular compact packing such as a cubic or hexagonal compact packing or also a mixed cubic-hexagonal compact packing that have a density of 0.74 relative to the maximum of a random compact packing with a packing density of between 0.625 and 0.641 . The packing density is defined as the fraction of space filled by particles. The difference relative to the value of 1 corresponds to the fraction of space occupied by the interstices. The packing density thus corresponds to the ratio between the volume occupied by the particles and the total volume consisting of the volume occupied by the particles and of the volume occupied by the interstices. In the case of a two-dimensional arrangement, the packing density corresponds to the ratio between the surface area occupied by the particles and the total surface area consisting of the surface area occupied by the particles and of the surface area occupied by the interstices. The term "surface area" is defined as a surface that includes all the centres of the particles arranged in a monolayer.

Advantageously, the packing density, in particular in the three-dimensional arrangement according to the invention obtained with a random arrangement of the particles on the belt and the vibration of said belt not compressed further according to step (d) of the process according to the invention, especially in the case of essentially spherical particles, does not exceed the value of 0.72, more preferably the value of 0.75, yet more preferably the value of 0.68. An excessively high density reduces the volume of the interstices and of the respective channels formed between the interstices, to the detriment of permeability/breathability for gases and liquids.

The fact that the particles are already foamed and do not foam further during the process assures the dimensional regularity of the particles and the uniformity in their distribution and consequently a satisfactory breathability. For applications of the arrangement of particles according to the invention that, for example, do not involve use in soles or insoles, the concept of the invention regarding the packing of the particles can nonetheless also be transferred to non-foamed and non-foamable polymeric particles. If a determined breathability of the material is not required, obviously, the process according to the invention can also be carried out with foamable particles that have not yet been foamed or have not yet been fully foamed, which can be foamed after step (b), e.g. upon activating the binding agent, in order to close the interstices. In an advantageous variant of the invention, said particles have stable shape, i.e. are not deformed during the process, e.g. by compression. In this case, the uniform breathability of the material, resulting from the uniform distribution of the interstices, achievable only through a rather regular order of the particles, is not accompanied by an additional reduction of the space occupied by the interstices due to the compression of the particles. The fact that the preferred shape of the particles in the random distribution on the belt is essentially, but not perfectly, spherical, enables the particles to have a high, but not perfect order, which results in a sufficiently large density of the interstices to assure sufficient breathability.

On 16 March 2015, Wikipedia, under "Random close packing", with reference to F.A.L Dullien in "Porous Media. Fluid Transport and Pore Structure", second edition, Academic Press Inc., 1992, contained the following comparison of the packing densities achievable with different methods: Table 1 :

Simple pouring of spherical particles on a bed (or into a mould) generates a density from 0.609 to 0.625, whilst use of a vibrating bed creates a density between 0.625 and 0.641 with high regularity. It seems contradictory to speak, in the case of the use of a vibrating ben, of random packing, inasmuch as it is a very close packing, consequence of a high order of the particles compared, for example, to a distribution achievable by the simple pouring of particles into a mould.

A positioning of the particles in predetermined positions makes it possible to obtain packings close to the theoretical ideal value achieved in metals or crystals.

Such distribution in predetermined positions can take place, for example, with a device that works by vacuum and aspirates one or more particles, then releasing it/them and positioning it/them, commanded for example by a computerised control unit, in well-defined positions on the surface. Such a device is advantageously a movable Cartesian coordinate system.

The optional additional compaction of the particles, if desired, reduce the space of the interstices but can be used to adjust the thickness of the sheet. Such compacting can take place, for example, by guiding in parallel with the continuous conveyor belt a body in the form of a sheet so that the sheet of particles is channelled between the belt and this body and where the body exerts a pressure on the layer of particles. Alternatively, the sheet could be passed through a calender. Sheets thus compressed also have another density with respect to the one obtained before compression. During compression, the particles partly lose the essentially spherical shape, but compression does not affect the order of the particles, because the particles are already mutually fixed. Compression advantageously takes place at the activation temperature of the binding agent. Compression shall preferably be progressive until the desired thickness is reached.

The fact that the particles are measured out on the surface, in particular on the conveyor belt, makes it possible to adjust the specific weight of the sheet (material/cm²). The sheet is preferably produced continuously.

A vibration of particles within a random distribution increases the density of the packing and introduces a certain regularity in the distribution of the particles (Table 1 ).

The vibration advantageously takes place in sequences of cycles in the three axes x, y and z. The duration of the vibration preferably does not exceed a total of 3 minutes.

The distribution of spheres on a vibrating belt creates a very compact packing of spheres in which the interstices are distributed homogeneously. This distribution remains essentially stable when subjected to compression. The packing thus achievable, i.e. through the use of a vibrating bed, will generally have a density of approximately 0.64. With respect to a packing achievable by the pouring of particles in a container, a packing achievable with a vibrating bed is no longer a free packing but a closed packing; hence, the shift is made from random loose packing to random close packing.

The invention is not limited to the use of spherical particles, but can also be implemented with particles having other geometries. However, a high regularity describable in geometric terms, metallic or crystalline packings, is obtained with (essentially) spherical particles.

In a variant of the invention, the arrangement of the particles corresponds to a metallic or crystalline arrangement.

In a variant of the invention, the arrangement is a two-dimensional arrangement of the particles in which the coordination number corresponds to 4 or 6.

The packing density can be determined according to various known methods, e.g. through microscopic determination of the surface area of the particle sections in different sections of known surface area of the sheet (in case of spherical particles of known size, it is sufficient to count the number of circles in the section of known surface area); or calculating the occupied volume of the particles knowing the volume of the sample, the density of the material of the particles and their weight (which can be determined, e.g., by the total weight of the sample minus the weight of the glue, determinable after chemical extraction of the glue; approximately, the weight of the sample - neglecting the weight of the glue - matches the weight of the particles).

In a particularly preferred variant of the invention, in step (b) a tangential or similar stress is applied on said arrangement of particles, resulting, in the case of a three-dimensional arrangement obtained by a random distribution of the particles on a belt and the vibration of the belt, preferably in a packing density > 0.64. This stress can, for example, be applied acting with a blade on the arrangement of particles to adjust the height thereof and consequently of the sheet. The particles thereby move by sliding over one another and are further compacted, creating a homogeneous distribution of interstices and assuring essentially uniform breathability throughout the sheet. Particularly in the case of two-dimensional arrangements or sheets, the order of the particles randomly poured on the belt approaches, at least in some regions of the arrangement, the regular compact packing of the hexagonal type (ideal density 0.91 ). The maximum random packing achievable in two-dimensional distributions corresponds to a density of 0.84.

Advantageously, the surface slopes slightly, this promoting a sliding of the particles or particle layers, thus probably developing tangential stresses which result - especially in arrangements that are initially more or less random - in (at least partially) regular distributions of the particles within the arrangement (of the sheet) which match or approach the ideal cubic and/or hexagonal compact packing.

In a preferred variant of the invention, the surface has an inclination of up to 30 degrees, more preferably between 5 and 15 degrees.

Preferably, the inclination of the surface or conveyor belt is combined with the use of a blade or the like to adjust the height of the sheet.

In a preferred variant of the invention, in the process according to the invention - in the presence of step (d) - after step (d) the following steps are added:

(e) maintaining compression, preferably at least at the activating temperature of the binding agent;

(f) cooling the arrangement formed in the previous steps;

(g) releasing pressure and optionally cutting the arrangement of particles; and (h) stabilising the arrangement of particles and - in the absence of step (d) - adding the aforesaid steps (f) and (g) and, optionally, cutting the arrangement of particles.

In case of compression, cooling preferably takes place in continuous, progressive compression until a set temperature is reached. The binding agent can thus be deactivated.

Pressure is preferably released at the end of the cooling. Cutting makes it possible to create plates or sheets of different measures or also bodies having different shapes, e.g. inlays for soles, saddles or protections.

Advantageously, the stabilisation of the sheet is carried out at ambient temperature; it serves the purpose of optimising the characteristics of the finished product.

Advantageously, the polymers are thermoplastic polymers.

In a preferred variant of the invention, the foamed polymers are selected among polyethylene (PE), ethylene vinyl acetate (EVA) styrene block thermoplastic elastomers (TPE-S), thermoplastic polyurethanes (TPE-U), thermoplastic polyester or co-polyester elastomers (TPE-E), and preferably from a mixture comprising at least EVA or PE and mixtures thereof, or otherwise ethylene-propylene rubber (EPR) and in addition block co-polymers of the styrene-ethylene-propylene-styrene (SEPS) or styrene-ethylene- butylene-styrene (SEBS) type. This latter mixture is described in the document WO 2002/020657 A1 .

In another preferred variant of the invention, the foamed polymers comprise a biodegradable elastomeric polymeric composition having hardness from 50 Shore A to 65 Shore D and comprising (a) from 15 to 50% by weight of a thermoplastic urethane polyester with a hardness from 50 to 90 Shore A; (b) from 35 to 75% by weight of a co-polyester having hardness from 32 to 70 Shore D and (c) from 5 to 40% by weight of a non-phthalate plasticiser. The thermoplastic polyester urethane preferably consists of a polyester, an isocyanate and a chain extender in which the ratio between the quantity of polyester and of the chain extender with respect to the quantity of isocyanate is lower than 8:2 and in which the polyester is a co-polymer of a diol selected from the group comprising butanediol, propanediol, ethylene glycol and mixtures thereof and of an aliphatic organic acid selected from the group comprising adipic acid, succinic acid, glutaric acid and mixtures thereof and in which the chain extender is selected from the group comprising butanediol, propanediol, ethylene glycol and mixtures thereof.

Advantageously, the co-polyester is a co-polymer of a diol, which is selected from the group comprising butanediol, propandiol, ethylene glycole and mixtures thereof, and an aliphatic organic acid selected from the group comprising adipic acid, succinic acid, glutaric acid and mixtures thereof and terephthalic acid.

Suitable polymeric compositions are described, for example, in the document WO 2009/1 12438 A1 .

An example for a particularly suitable mixture is the product APINAT® by API S.p.A., Italy. Obviously, all types of foamed polymers can be used, which are suitable for use of the arrangement or sheet of particles which could, for example, also be an application in insulation for construction (thermal and/or acoustic insulation).

Advantageously, the aforementioned foamed polymers are foamed by means of foaming agents of a chemical and/or physical nature. Preferably, within the polymeric mixture, a mixture of both foaming agents is used in a percentage of 15% by weight, yet more preferably of 10%.

In preferred variants of the invention, the particles within the arrangement can be made of different materials, selected preferably from those listed above. The invention is not limited to determined materials of foamed polymers. The selection of the material depends on the application of the semi-finished product.

The above specified materials are particularly suitable for the application of the material in soles or insoles for shoes, in saddles or protections, e.g. within items of sports apparel.

According to a preferred variant of the invention, the particle arrangement is a sheet of particles, preferably a two-dimensional arrangement of the particles, and a plurality of these sheets obtained according to the process according to any one of the claims 1 through 9 are superposed one over the other and preferably glued together to form a laminar sheet, i.e. a multilayer sheet. Advantageously, they are thin laminae and in particular two-dimensional laminae, i.e. with a single layer of particles. In two-dimensional sheets, a high order of the particles can be achieved, which increases the uniformity of the breathability, density, hardness and rebound of the material. In two- dimensional sheets, the preferred maximum limit value for the packing density is greater than the values indicated for three-dimensional arrangements. In a preferred variant of the invention, individual sheets present a regular hexagonal arrangement of the particles.

In an advantageous variant of the invention, the multi-layer sheet comprises sheets of different materials. This offers the possibility of providing the multilayer sheet with a combination of different characteristics deriving from the different materials used for the individual sheets.

Another aspect of the invention concerns a three-dimensional or two- dimensional arrangement, in particular a sheet, of particles of foamed polymers in which said particles are essential spherical and connected, preferably glued to each other, and mutually fixed in their position within the arrangement, and in which said particles preferably have essentially equal dimensions with a tolerance < ± 25%, preferably < ± 15%, and they are arranged, in the case of three-dimensional arrangement, in a compact order with a packing density > 0.6, preferably > 0.625, yet more preferably > 0.64, or, in the case of a two-dimensional arrangement, with a packing density > 0.70, more preferably > 0.75, yet more preferably > 0.78 and most preferably > 0.90. Advantageously, the packing density, in particular in the non-compressed three-dimensional arrangement according to the invention, especially in the case of essentially spherical particles, does not exceed the value of 0.72, more preferably the value of 0.75, yet more preferably the value of 0.68.

Advantageously, the breathability of the particle arrangement is similar (equal) to or greater than the breathability of leather. Preferably, the breathability, i.e. the permeability to water vapour, according to the ISO 17699 method at 23 ± 1 °C and with relative humidity of 50 ± 3% is equal to or greater than 0.8 mg/cm² h, more preferably between 0.8 and 10.0 mg/cm² h and still more preferably between 0.8 and 1 .6 mg/cm² h. Values around 0.8 mg/cm² h are observed in particle arrangements according to the invention without lights visible to the naked eye, while values close to 1 .6 mg/cm² h are observed in particle arrangements according to the invention with lights visible to the naked eye. Permeability to water vapour was determined with plate-shaped samples whose dimensions are 150 x 150 x 6 mm. According to shoe standards EN ISO 20345:201 1 , EN ISO 20346:2014 and EN ISO 20347:2012 a leather shall have vapour permeability no lower than 0.8 mg/cm² h; hence, the particle arrangement according to the invention fully achieves the values required for leather in shoes. Normally, a technical fabric has vapour permeability of 4 mg/cm² h. The selection of the type and/or degree of regularity in the positioning of the particle in predetermined positions or in the vibration of the surface, the selection of the distribution of the particles' diameters, the selection of the shape of the particles, the selection of the degree of compression of the particle arrangement make it possible to vary or adjust the water vapour permeability of the semi-finished product.

Advantageously, the density of the semi-finished product, i.e. of the arrangement of foamed polymer particles measured at ambient temperature, varies between 0.30 and 0.60 g/cm³. A typical foamed polymeric material used to make the particles has, for example, preferably a density of approximately 0.390 g/cm³. Advantageously, the density of the arrangement can be varied by varying the compactness of the packing of the particles and/or the degree of compression applied on the arrangement.

In a preferred variant of the invention, a multi-layer sheet comprises a plurality of sheets as defined above, which are stacked on top of each other and preferably glued to each other.

Advantageously, the plurality of sheets is a plurality of two-dimensional sheets. A last aspect of the invention refers to an article produced with an arrangement, a sheet or a part of the sheet according to any of the claims 12 through 14, or with an arrangement, a sheet or a part of the sheet obtained according to the process of the claims 1 through 1 1 , in which the article is preferably selected among padding for seats, impact protections, saddles for bicycles or motorcycles, sound-absorbing and/or heat-absorbing elements for the building industry, and items of clothing.

All the characteristics indicated above for the process according to the invention can, mutatis mutandis, be transferred to the arrangement, in particular to the sheet and to the article according to the invention and vice versa.

Variants of the invention are object of the dependent claims.

The description of preferred examples of execution of the process, of the arrangement, of the sheet and of the article according to the invention is given by way of non-limiting example.

Brief description of the drawings

- Fig. 1 shows, in a flowchart, the various steps of an example of execution of the process according to the invention;

- Fig. 2 shows a device to carry out a distribution of the foamed polymer particles on a vibrating belt;

- Figs. 3a-3i show photographs of sheets according to the invention;

- Figs. 4a and 4b show ideal two-dimensional arrangements of particles with, respectively, coordination numbers 4 and 6;

- Fig. 5 shows the steps of a distribution of particles according to the invention to obtain a two-dimensional sheet with a hexagonal order of the particles;

- Figs. 6a and 6b respectively show in sketched form (fig. 6a) and in photograph form (fig. 6b) a pin structure to aid the regular arrangement of the particles.

Description of preferred exemplary embodiments

An example of execution of the process according to the invention is shown in the flowchart of figure 1 .

The process is divided in two main steps: the preparation of foamed polymer particles and the manufacture of a sheet.

In the first step of the preparation of the particles, the particles are dried 10 to eliminate humidity from the material that may derive from the process for the production of the particles or from the absorption of humidity from the environment. If desired, the step can also comprise a sieving of the particles to obtain a homogeneous particle size distribution.

It is followed by the second step which consists of the distribution 12 of water- based thermoplastic polyurethane glue on the surface of the particles. The distribution takes place with a mechanical process as described above and with a controlled dosage of the quantity of glue to assure a uniform thickness of the glue on the particles.

The third step involves the drying 14 of the glue. Drying takes place in "non-forced" form, i.e. at ambient temperature, in order not to alter the characteristics of the thermoplastic glue.

The fourth step is the mechanical separation 16 of the particles. During the application of the glue, agglomerations of particles may be formed that are dissolved in order to arrange the particles independently from each other. One method for separating the particles is to introduce them between two rotating disks. This is a separation without direct contact.

The subsequent step is the pre-heating 18 of the particles at a temperature that does not activate the glue. Such pre-heating aids in increasing the speed of production of the sheet.

Subsequently, the step of manufacturing the sheet starts.

In step 20, the pre-heated particles are measured out in a predefined quantity - to be able to adjust the specific weight of the future sheet - on a continuous conveyor belt that is slightly sloped. The belt can be set in vibration to give a high order if the particles were poured in a disorderly manner on the belt. It is also possible to arrange the particles in an orderly manner on the belt, e.g. with a movable system with three Cartesian axes, able to arrange the particles in determined positions. In this case, on the belt there may be pin structures with regular order, to maintain the particles in a regular order. With the advance of the belt, a continuous layer of particles is formed. With a blade or a similar instrument, it is possible, when required, optionally to exert a cutting force or a tangential force on the surface of the layer opposite to the surface that bears on the belt. On one hand, application of this force regulates the thickness of the layer, but on the other hand it also creates a further compacting of the particles which results in an additional order of the particles. It follows step 22 of the heating of the particles at the activation temperature of the selected thermoplastic glue. The glue is activated and the gluing of the particles to each other starts. The order of the particles is fixed.

If desired, a progressive compacting 24 of the sheet is continued, e.g. in a calender, to obtain the desired thickness of the sheet. The compacting comprises the crushing of the particles.

In step 26, the compression is maintained at temperature for a determined period, e.g. from 1 to 5 minutes, according to the desired thickness.

Consequently, in step 28 the sheet is cooled under continuous and progressive compression down to a set temperature; compression is released at the end of the cooling and the sheet exits continuously. An optional cut to measure follows.

The process ends with the stabilisation 30 of the finished product at ambient temperature to optimise the characteristics of the finished product.

Figure 2 shows a device able to distribute the foamed polymer particles at random on a belt. From the dosing device 100 defined quantities of particles 101 are dispensed on the vibrating conveyor belt 104 in translational motion according to the arrow 105. At the time of distribution on the belt the order of the particles is random; only the vibration induces a high packing of the particles. The belt is inclined. The vibration takes place for approximately 3 minutes. From above it acts a blade 103 that exerts a tangential force on the layer of particles that is formed during the vibration and the movement of the belt. The vibration already causes a high compaction of the particles that is further increased as described above by the tangential force. Downstream of the blade 103 the sheet has uniform height and the particles are distributed in a very compact and regular form.

Figures 3a to 3e show semi-finished products obtained with the vibrating belt process and random pouring of the particles on the belt, whilst figures 3f to 3i show semi-finished products obtained by positioning the particles in predetermined positions on the belt.

Figure 3a shows a prospective view of a two-dimensional sheet as produced according to the process described above, i.e. with a vibrating belt. The sheet comprises ellipsoidal particles and a high compactness of the particles is noted.

The two- or three-dimensionality of the sheet can be achieved with the suitable quantities of particles/area of the surface and with a related positioning of the instrument that adjusts the height of the particle arrangement.

Figure 3b shows a prospective view of a multi-layer sheet according to the invention that comprises three monolayer sheets. In the upper sheet extensive regions can be clearly observed in which the particles are arranged according to a hexagonal regular order obtainable with the vibration and inclination of the belt.

Figure 3c shows a lateral view of the sheet of figure 3b. A hexagonal compact packing of the particles of the dimension of the thickness of the sheet is clearly visible.

Figure 3d shows a prospective view of a three-dimensional sheet according to the invention in a production with vibrating belt without additional compression; and figure 3e shows such a three-dimensional sheet with an additional compression in which the interstices are partially occupied by the particles deformed during compression.

Figures 3f and 3g show from above some particle arrangements in which each particle has a coordination number 4. Individual sheets of this type can be arranged one above the other in such a way that the particles of different sheets are directly superposed or in such a way that the particles of a sheet are positioned in the interstices of at least another sheet.

In figures 3h and 3i, a hexagonal distribution of the particles is noted (coordination number 6). Here, too, individual sheets of this type can also be arranged on top of each other in such a way that the particles of different sheets are directly superposed or in such a way that the particles of one sheet are located in the interstices of at least another sheet according to a cubic or hexagonal compact packing.

Figures 4a and 4b show, respectively, an ideal monolayer of spheres arranged with a coordination number 4 or with a coordination number 6.

Figure 5 shows different steps of a possible positioning of the particles in predetermined positions in which in step (i) the particles 201 are arranged in contact in a row with a vacuum device that releases and positions the particles 201 one by one according to a predefined programme that manages the movement and positioning of the particle dispensing device. In step (ii), a second row of particles 201 was arranged and in step (iii) a third file, forming a hexagonal arrangement of the particles. Arranging additional rows of particles, a sheet is obtained.

Figure 6a shows that to promote regular positioning and prevent a displacement of the particles before gluing, on the belt an arrangement of pins 211 can be located that extend vertically with respect to the belt. Figure 6a is a top view. These pins 211 form for example a triangular arrangement in which between three pins 211 that form a triangle a particle 201 is positioned. An example for such a pin structure is shown in the photograph of figure 6b.

Upon execution, additional modifications or execution variants, not described herein, may be made to the process, the arrangement, the sheet and the article of the invention. Where such changes or such variants should fall within the scope of the following claims, they shall be understood as all protected by the present patent.

Claims

CLAIMS 1 ) Process for the production of arrangements of foamed polymer particles, in particular sheets of foamed polymer particles, wherein the particles are connected together and fixed to one another in their position within the arrangement, comprising the following steps: (a) preparing foamed polymer particles (101 ; 201 ) coated at least partially on the surface by a binding agent not yet activated; (b) distributing (20) a determined amount of said particles in two dimensions or in three dimensions on a surface, up to obtain an arrangement of particles as a compact packing, in the two-dimensional case preferably with a packing density of > 0.70, more preferably > 0.75, even more preferably > 0.78, and most preferably > 0.90, and in the three-dimensional case preferably with a packing density of > 0.6, more preferably > 0.625; (c) activating (22) said binding agent to connect the particles thus arranged to one another and fix the arrangement obtained in step (b); and optionally (d) a further compaction (24) of the particle arrangement by compression. 2) Process according to claim 1 , characterized in that said binding agent is a glue. 3) Process according to claim 1 or 2, characterized in that said activation (22) in step (c) takes place by heating. 4) Process according to any one of claims 2 or 3, characterized in that said step (a) comprises the following steps:

(a1 ) preparing particles of foamed polymer material, preferably dried (10);

(a2) distributing (12) a glue on the particle surfaces;

(a3) drying (14) the glue without activating it;

(a4) where necessary, separating (16) the particles; and optionally

(a5) preheating (18) the particles provided with glue without activating the glue.

5) Process according to any one of the preceding claims, characterized in that said foamed polymer particles (101 ; 201 ) are subjected, preferably before applying the binding agent, to a sieving.

6) Process according to any one of the preceding claims, characterized in that said distribution (20) of a predetermined amount of said particles in two dimensions or three dimensions on a surface takes place with a dispensing and positioning device (100) which dispenses one or more particles and arranges the particles respectively individually, or in groups randomly or in predetermined positions on the surface (104) in which, in the case of random positioning, the surface (104) is already vibrating with or after the distribution of the particles (101 ) on the surface and in which, in the case of positioning in predetermined positions, regular coordination numbers for particles (201 ) are observed.

7) Process according to any one of the preceding claims, characterized in that the particles (101 ; 201 ) are essentially spherical and have essentially the same size with a tolerance < ± 25%, preferably < ± 15% and in that the particles have preferably a diameter of between 3.0 mm and 9.0 mm.

8) Process according to any one of the preceding claims, characterized in that in step (b), a tangential effort is applied on said particle arrangement (101 ) resulting, in the case of a three-dimensional arrangement, preferably in a packing density of > 0.64.

9) Process according to any one of the preceding claims, characterized in that the foamed polymers are selected from polyethylene (PE); ethylene vinyl acetate (EVA); styrene block co-polymer-based thermoplastic elastomers (TPE-S); urethane-based thermoplastic elastomers (TPE-U); polyester or co-polyester-based thermoplastic elastomers (TPE-E); a mixture comprising at least EVA or PE and mixtures thereof or otherwise ethylene-propylene rubber (EPR) and in addition styrene-ethylene-propylene-styrene (SEPS) or styrene- ethylene-butylene-styrene (SEBS) block co-polymers; and preferably from a biodegradable elastomeric polymeric composition having a hardness of 50 Shore A to 65 Shore D and comprising (a) 15 to 50% by weight of a thermoplastic urethane polyester with a hardness of 50 to 90 Shore A; (b) 35 to 75% by weight of a co-polyester with a hardness of 32 to 70 Shore D and (c) 5 to 40% by weight of non-phthalate plasticiser.

10) Process according to any one of the preceding claims, characterized in that said particle arrangement (101 ; 201 ) is a sheet of particles, preferably a two-dimensional arrangement of the particles, and in that a plurality of these sheets obtained according to the process according to any one of the claims 1 to 9 are superposed one over the other and preferably glued together to form a laminar sheet, i.e. a multilayer sheet.

1 1 ) Process according to any one of the preceding claims, characterized in that said surface is a continuous conveyor belt (104). 12) A three-dimensional or two-dimensional arrangement, in particular a sheet, of particles of foamed polymers (101 ; 201 ) in which said particles are essentially spherical and connected, preferably glued to each other, and mutually fixed in their position within the arrangement, and in which said particles preferably have essentially equal dimensions with a tolerance < ± 25%, preferably < ± 15%, and they are arranged, in the case of three- dimensional arrangement, in a compact order with a packing density > 0.6, preferably > 0.625, yet more preferably > 0.64, or, in the case of a two- dimensional arrangement, with a packing density > 0.70, more preferably > 0.75, yet more preferably > 0.78 and most preferably > 0.90.

13) Arrangement according to claim 12, characterized in that the water vapour permeability of said arrangement determined according to the ISO 17699 method at 23 ± 1 °C and with relative humidity of 50 ± 3% is equal to or higher than 0.8 mg/cm² h, more preferably between 0.8 and 10.0 mg/cm² h and still more preferably between 0.8 and 1 .6 mg/cm² h.

14) Multilayer sheet characterized in that it comprises a plurality of sheets, according to claim 12 or 13, which are stacked on top of each other and preferably glued to each other.

15) Article produced with an arrangement, a sheet or a part of the sheet according to any of the claims 12 to 14, or with an arrangement, a sheet or a part of the sheet obtained according to the process of the claims 1 to 1 1 , in which the article is preferably selected among padding for seats, impact protections, saddles for bicycles or motorcycles, sound-absorbing and/or heat- absorbing elements for the building industry, and items of clothing.

16) Use of an arrangement, a sheet or a part of the sheet according to any of the claims 12 to 14, or of an arrangement, a sheet or a part of the sheet obtained according to the process of the claims 1 to 1 1 in soles or insoles for shoes.