WO2022229399A1

WO2022229399A1 - Recyclable textile mesh and paper composite incorporating same

Info

Publication number: WO2022229399A1
Application number: PCT/EP2022/061506
Authority: WO
Inventors: Florence Andrioletti; Freddy MACREZ; Régis Mussier
Original assignee: Porcher Industries
Priority date: 2021-04-30
Filing date: 2022-04-29
Publication date: 2022-11-03
Also published as: FR3122439A1; EP4330456A1; FR3122439B1

Abstract

The invention relates to a textile mesh consisting of at least two, preferably three, layers of threads forming a basic pattern formed by constituent threads of these layers, said threads being respectively oriented in different directions and overlapping at points of intersection to form the basic pattern, in which at least one of the layers consists of threads of polyvinyl alcohol (PVA), and the threads of the layers are bonded together at their points of intersection by a water-soluble hot-melt adhesive. The water-soluble polymer threads and the water-soluble hot-melt adhesive are soluble in water or an aqueous solution in the same temperature range, particularly at a temperature between 20 and 80°C. This mesh can be incorporated into an article, notably a casing, container or packaging, the assembly being able to be easily disintegrated and solubilized in an aqueous medium and under hot conditions, to facilitate a recycling operation.

Description

DESCRIPTION

TITLE: Recyclable textile grid and papermaker composite incorporating it

The present invention relates to a novel textile grid having an ability to be recycled. It also relates to composites, in particular papermaking composites incorporating this new grid as reinforcement. The resulting assembly has good recycling properties.

Textile grids are used for the reinforcement of envelopes, boxes and other packaging made of paper, cardboard or similar. The grid is generally glued to one side of a paper or cardboard support forming all or part of the envelope, cardboard or other, or the grid is placed between two such supports. Reinforcement grids are made by assembling wires made of inorganic material such as glass or synthetic material such as polyester. These grids cause problems during recycling processes for paper or cardboard items. The grid constitutes a hindrance in the hydrothermal repulping processes, by not being soluble in hot water and by hindering, or even blocking, the agitation devices, in particular the blades intended to agitate the water-paper mixture to disintegrate. Textile grids are also used in the reinforcement of gummed adhesive tapes.

Wanting to offer a textile grid keeping its reinforcing properties while being totally or partially recyclable, in particular under the conditions of repulping of these products, in particular envelopes or reinforced cardboard, or even adhesive tapes, requires finding a difficult compromise between the composition of the yarns of the grid, and the nature of the adhesive and its mode of implementation during the manufacture of the grid. It is necessary in particular to select a nature of the wires constituting the grid which can successfully support the manufacturing processes of the grids, to select an adhesive material allowing an assembly of the wires of the grid at their crossing points which is resistant, which does not deteriorate the material of the wires or generate phenomena of shrinkage of the wires during the implementation of the adhesive, shrinkage which would cause deformation of the grid.

In particular, the inventors have found that it is of fundamental importance to implement an adhesive that does not involve any risk of shrinkage of the water-soluble threads, as may be the case with adhesives implemented in solvent phase or in aqueous phase.

Grids made of PVA threads, which are water-soluble by nature, and assembled using a PVA-based glue, are not the best suited. The implementation of this adhesive by impregnation in aqueous phase (JP H07 150457), is by nature capable of generating a certain degradation of the PVA threads due to the water-soluble nature of these threads. In addition, the phase of evaporation of the water provided by the glue, and therefore of heat input, can lead to retraction of the PVA threads, since these threads are heat-sensitive.

The inventors have also been able to determine that the choice of the adhesive and the way in which it is implemented determine the fact that the grid can be made both entirely and partially of water-soluble threads which, unlike the threads of conventional reinforcing grids , are sensitive to solvent-phase or aqueous-phase adhesives and may undergo shrinkage phenomena during the evaporation of the solvent or water. The choices made by the inventors make it possible to manufacture grids that dissolve or disintegrate entirely or only partially, and to offer solutions at different costs.

The present invention therefore aims to remedy these drawbacks of the reinforcement grids and to propose a textile grid which can be used in particular for the reinforcement of envelopes, boxes and other packaging made of paper, cardboard or the like, or even adhesive tapes, while improving the possibilities recycling of these products, in particular during hydrothermal repulping processes with agitation. In particular, the invention aims to provide a grid which is made up solely of water-soluble threads, or which comprises a sufficient proportion or an appropriate distribution of water-soluble threads, to allow disintegration or dissolution of the grid, for example during a hydrothermal plumping. The invention aims in particular to propose a regular reinforcing grid, without deterioration of the threads and without deformation or shrinkage of the warp and/or weft threads during manufacture, and which is therefore both resistant and totally or sufficiently water-soluble in repulping conditions. The invention also aims to provide a grid that can be manufactured without resorting to the use of potentially toxic and aggressive organic solvents.

A first object is therefore a grid formed of at least two layers or layers of threads forming an elementary pattern formed by constituent threads of these layers, the constituent threads of which are respectively oriented in different directions and intersect at crossing points to form the basic pattern. This grid consists only of water-soluble threads, or it comprises a sufficient proportion or an appropriate distribution of water-soluble threads. The yarns of the sheets are glued together at their crossing points by a hot-melt polymeric glue or adhesive (hot-melt, the definition of which is given below), which is nevertheless soluble in water brought to an appropriate temperature. The glue or hot melt adhesive is applied in a molten or liquid state at the time of the manufacture of the grid, then hardened or congealed to ensure bonding crossing points. Curing of the glue is easily achieved by cooling below the melting point of the glue. Preferably, the water-soluble yarns are made of PVA (polyvinyl alcohol or poly(vinyl alcohol)). Preferably, the hot-melt glue is PEG (polyethylene glycol) or a derivative of PEG. Such PEG-type adhesives that can be used here have an unusual hot-melt behavior that can be used in this invention.

According to one aspect, the textile grid is formed of at least two, preferably three, layers of threads forming an elementary pattern formed by constituent threads of this layers respectively oriented in different directions and crossing at crossing points to form the elementary pattern, where the threads of the layers are glued together at their crossing points by a polymeric glue, characterized in that at least one of the layers is formed of polyvinyl alcohol (PVA) threads, in that the polymeric glue is a water-soluble hot-melt adhesive, and in that the water-soluble polymer threads and the water-soluble hot-melt adhesive are (chosen to be) soluble in water or an aqueous solution in the same temperature range, in particular when hot, typically at a temperature between 20 and 80°C. Preferably, all webs are formed of water-soluble PVA yarns. The glue is used in the molten state to glue the threads at the crossing points.

The yarns of the layers or layers are preferably straight yarns. The straight threads of a first layer or ply are arranged in relation to the straight threads of the other layer or ply by repeating, regularly in the plane of the grid, the pre-established elementary pattern. In one embodiment, the threads of a layer or ply are not straight, they may have a wavy or zigzag arrangement. Layers or tablecloths can simply be layered. They can also be crisscrossed, which means that all or part of the threads of the two layers or layers crisscross like a fabric. All or part of the threads of the grid are made of a material which solubilizes when they are placed in water or an aqueous solution brought to an appropriate temperature, and preferably under stirring facilitating dissolution (we speak of "water-soluble" threads ). Preferably, all the threads of the same ply are of this same nature, and the grid can comprise plies which all meet this characteristic, or only some of the constituent plies meet it. Advantageously, any ply placed in a longitudinal direction or “warp” direction responds thereto. In a preferred embodiment, all of the yarns are water-soluble.

The yarns can be superposed by being distributed in at least two superposed layers whose respective yarns cross each other. They can also be crossed at the way of a fabric. The threads are, at their intersections or their intersections, glued to each other by the hot-melt adhesive, applied in the molten or liquid state, then hardened.

In one embodiment, the grid comprises three superposed layers or layers of wires, one of the layers or layers, called inner, being between the two other layers or layers, called outer. In this case, according to a particular embodiment, the two outer layers or layers, preferably forming the warp yarns, are formed of straight yarns arranged in parallel, superimposed (first case) or offset (second case) in the grid plane. In one embodiment, the outer layers or layers at least are formed of threads of water-soluble material. In another embodiment, the outer layers or webs and the inner layer or web are formed of yarns of water-soluble material. In another embodiment, all of the webs are formed of threads of water-soluble material.

In the first case, the wires of the two outer layers or layers are superimposed in the plane of the grid and are in contact at the same crossing points with the straight wires of the inner layer or layer, which confers increased resistance at the crossover points. bonding. In particular, the grid is formed of two layers of warp yarns and a layer of weft yarns, the warp yarns of the two layers overlapping and being joined two by two at the crossing points with the weft yarns.

In the second case, the threads of the two outer ply or layers framing the inner layer or ply cross the threads of the inner layer or ply alternately in the plane of the grid and in the longitudinal direction of the inner layer (going from a end to the other of this layer, a first yarn from an outer layer crosses the yarns from the inner layer, then it is the turn of a yarn from the other outer layer, then again a yarn from the first outer layer, etc.). In particular, the grid is formed of two layers of warp threads and of a layer of weft threads, the warp threads of the two layers crossing the warp threads alternately, as has just been described, and are therefore glued separately at the crossing points with the weft threads.

The grid may in particular be bidirectional, with wires oriented in one direction and wires oriented in another direction. In particular, the grid comprises a first layer of yarns oriented in a first direction and two other layers of yarns oriented in the same direction different from the first layer. For example, the first layer is a layer of weft threads, the other two layers being layers of warp threads. In particular, the first layer is placed between the two other layers. The threads of the layers oriented in different directions intersect and form an elementary grid pattern. The elemental pattern of the grid includes intersecting threads with an angle of preferably 90°, or close to 90°. This pattern consists of a parallelepiped, in particular square or rectangle, depending on the number of yarns per cm in each of the layers. As will be seen, a rectangular pattern is preferred with the warp yarns forming the long sides of the repeated rectangular pattern.

The grid can also be multidirectional, with groups of wires oriented in at least three different directions. Preferably, it is then three-way, with groups of threads oriented in three different directions. In particular, the grid comprises a first ply of threads oriented in a first direction, a second ply of threads oriented in a second direction, the threads delimiting a diamond pattern, with the threads of the first ply forming for example an angle between 20 and 90°, preferably between 30 and 80°, with the threads of the second ply. The third layer has its yarns oriented in a direction crossing the first two layers. In particular, in a three-way grid, the first and second layers are formed of weft threads, and the third layer is formed of warp threads.

In other words, by regular repetition of the aforementioned pattern, in the two directions defined by the plane of the grid, the whole of this grid is obtained. Thus, the different wires constituting the grid are positioned relative to each other according to a pre-established geometry, both in relative orientation and in relative spacing in the plane of the grid.

The grid preferably has a density of threads or a pitch of between approximately 0.3 and 8 threads/cm, preferably between 0.8 and 4 threads/cm. The number of threads per cm can be identical for all the sheets, or vary from one sheet to another, to form, for example, rectangular patterns.

In one embodiment of a bidirectional grid, the elementary pattern of the grid comprises two sides formed by warp threads and two sides formed by weft threads. It is preferably a rectangle. In a preferred embodiment, the sides of the rectangle formed by the warp threads are longer than the sides formed by the weft threads. This configuration is moreover preferred when the grid comprises non-water-soluble threads, which are then preferentially the weft threads.

In a particular embodiment of a bidirectional grid, the grid comprises two layers of straight warp yarns and a layer of straight weft yarns, the two layers of warp yarns being placed on either side of the layer of warp yarns. weft, the rectilinear warp threads forming a pre-established angle with the rectilinear weft threads, warp threads and weft threads being glued at their points of intersection or superposition. Preferably, the yarns of the two warp layers overlap in the plane of the grid and at the crossing points with the weft yarns. In these different embodiments, the yarns of all the layers can be straight, or, alternatively, the warp yarns are straight and the weft yarns are crimped or zigzag.

Preferably, in the various embodiments of grids, the layer or layers or sheets of warp threads at least are formed of threads of water-soluble material. It is also possible for the layer(s) or layers of warp threads and the layer(s) or layers of weft threads to be formed of threads of water-soluble material.

The grid according to the invention comprises threads which have the particularity of dissolving or disintegrating in water or an aqueous solution brought to an appropriate temperature, for example water or a hot aqueous solution between about 10 and about 80 °C, in particular under agitation, and in particular under the conditions of repulping paper or cardboard. These threads are in particular polyvinyl alcohol (PVA) threads, which dissolve under these conditions (“water-soluble”). The PVA yarns are preferably multifilament. As described above, the grid is formed of at least two layers or layers of wires, and for example of three layers or layers. Preferably, it is the whole of a layer or ply which is formed of these water-soluble PVA threads. Also preferably, all the layers or webs are formed of such PVA threads. As a variant, certain layers or webs are made of PVA, the other(s) of another material. Typically, in this embodiment, the grid is formed of the two aforementioned layers of warp threads, which are made of PVA, and of a layer of weft threads, made of another material, in particular suitable for the manufacture of grids on a grid production line. In one embodiment, the layers or sheets of thread which are not made of PVA, are made of polyester (PE).

The yarns (in particular made of PVA or PE) can have a count of between 50 and 1100 dtex, preferably between 76 and 280 dtex. Preferably, all the wires of the grid have the same or similar title. Thus, in a grid comprising PVA yarns and PE yarns, the count of these yarns is preferably identical or substantially identical.

As is known per se, PVA covers the family of polymers whose common point is to contain a generally high proportion of the elementary unit -CH2-CH(-OH)-. The polymer is obtained by saponification or alcoholysis or hydrolysis of a polyvinyl ester. The PVA is generally in the form of a vinyl ester-vinyl alcohol copolymer. The starting vinyl ester used is polyvinyl acetate. The PVA is therefore preferably a poly(vinyl alcohol-co-vinyl acetate) and mainly comprises alcohol groups relative to the acetate groups. It is known in the literature that PVA is obtained by partial or total hydrolysis of the acetate groups of a poly(vinyl acetate) generating the alcohol groups. The PVA is characterized by its percentage of molar hydrolysis, that is to say the molar percentage of alcohol functions relative to the functions (acetate+alcohol).

It is known that commercially available PVA yarns have variable solubilities in water, typically expressed in a temperature range, ranging in particular from 15 to 100°C. For example, NITIVY sells PVA yarns in water solubility temperature ranges of 15-24°C, 31-41°C, 42-52°C, 45-55°C, 48-58° C, 81-89°C, or alternatively 89-97°C. In the invention, it is possible to use PVA yarns having a dissolution temperature in water of the same order as the repulping temperature used. In particular, pragmatically, water-soluble PVAs at a temperature of between approximately 10 and approximately 80° C., in particular between approximately 20 and approximately 70° C., will be retained.

Processes for manufacturing PVA yarns are known. The PVA used for spinning the PVA fibers may in particular have a degree of saponification of at least 95% by mole and/or an average degree of polymerization of approximately 500 to approximately 3000, preferably of approximately 1000 to approximately 2000 .

The water-soluble PVA or the PVA yarn which is made of it may have in particular one, two or the following three characteristics: degree of hydrolysis of the PVA of approximately 80 to approximately 100% by mole, preferably of approximately 95 to approximately 99 .5 mol% (measurement by proton NMR, see examples section); melting point of the PVA yarn from about 170 to about 240°C, preferably from about 200 to about 230°C (measurement by differential scanning calorimetry - DSC, see examples section fracture toughness of the PVA yarn from approximately 3 to approximately 7 cN/dtex, preferably approximately 4 to approximately 6 cN/dtex (measurement by traction on the yarn according to standard NF EN ISO 2062) Preferably, the three aforementioned characteristics are combined.

Advantageously, PVA threads are used which dissolve in water or an aqueous solution during a paper and cardboard repulping process. Such a method can use water or an aqueous solution between about 20 and about 80°C, preferably between about 40 and about 70°C, with stirring. Stirring means a variable geometry stirring blade or a variable geometry stirring screw, and more specifically a conical stirring screw. The presence of acids or bases or other additives or various pollutions in the water or the aqueous solution cannot be excluded.

PE (polyester) yarns are multifilament. They may in particular have one, two or the following three characteristics: glass transition temperature of 60 to 90° C., preferably of 70 to 80° C. (according to standard ISO 11357-3); melting point from 240 to 270° C., preferably from 250 to 260° C. (according to standard ISO 11357-3); forced to rupture of 3 to 7 cN/dtex, preferably 4 to 6 cN/dtex (according to standard NF EN ISO 2062). Preferably, the PE yarn has the three aforementioned characteristics.

The glue used to glue the wires at their crossing points (overlapping or criss-crossing) is a hot-melt polymeric glue, i.e. solid at room temperature, applicable and applied in the molten state, and adhering to the substrate (the wires of the grid) by cooling below its melting point (we say that the glue then hardens or freezes). This hot-melt adhesive is moreover water-soluble at the temperature of dissolution of the water-soluble threads of the grid, or else it degrades under these same conditions. The heat-sensitive adhesive is not implemented in a form dissolved in a solvent or in an aqueous phase.

The water-soluble polymer threads and the water-soluble glue are preferably soluble in water or an aqueous solution in the same temperature range, in particular at a temperature between approximately 10 and approximately 80° C., preferably between approximately 20 and approximately 70 °C. This polymer adhesive is therefore preferably soluble in water or an aqueous solution brought to an appropriate temperature, as indicated above, advantageously with stirring (hydrothermal treatment or repulping).

The hot-melt adhesive is preferably formed from polyethylene glycol or from a polymer comprising a polyethylene glycol backbone, in particular ether derivatives of polyethylene glycol. The acronym PEG is used herein to refer to all such compounds, unless otherwise indicated. Particular mention will be made of PEGs having: a molecular mass of approximately 1000 to approximately 10,000 g. mol ¹ , preferably from approximately 1200 to approximately 8000 g. mol ^-1 , preferably from about 1500 to about 5000 g. mol ^-1 (according to the ISO 13885-3 standard, determined by steric exclusion chromatography in an aqueous medium using PEG standards of known molecular mass); and/or a melting point of about 35 to about 100°C, more particularly about 35 to about 80°C, preferably about 40 to about 70°C, preferably about 45 to about 65° C (according to ISO 11357-3); and/or a viscosity of about 5 to about 1000 mPa.s at 100°C, preferably about 10 to about 500 mPa.s at 100°C, preferably about 20 to about 200 mPa.s at 100°C (according to standard NF EN ISO 2555). Preferably, the PEG has the three aforementioned characteristics.

The hot-melt glue can be formed from a polymer comprising a polyethylene glycol skeleton comprising two ends comprising a hydroxyl group (PEG itself). Alternatively, the hot-melt adhesive may be formed from a polymer comprising a polyethylene glycol backbone comprising one end comprising a hydroxyl group and one end comprising a methoxyl group (MPEG or methyl ether of poly(ethylene glycol)). Alternatively, the hot-melt adhesive can be formed from a polymer comprising a polyethylene glycol skeleton comprising two ends comprising a methoxyl group (dimethyl ether of poly(ethylene glycol)). Alternatively, the hot-melt adhesive can be formed from a mixture of at least two of the above polymers.

The hot-melt glue can be supplemented with various mineral fillers, for example silica fillers to impart slipperiness to the hardened or solidified residue of the glue and to facilitate, for example, the unrolling of a roll of the recyclable grid of the invention.

The grid therefore comprises the hardened or solidified residue of the glue (by default it is agreed to speak of glue at the points of intersection) fixing the various sheets or layers of threads at the points of intersection of the respective threads. This hardened or solidified residue is advantageously non-sticky to the touch. In one embodiment, the glue is applied over the entire surface of the grid and, consequently, the hardened residue of the glue is also present on the surface of the threads of the different sheets or layers. This does not call into question the dissolution capacity of the structure of the grid between non-water-soluble yarns and PVA yarns which are. The use of water-soluble glue makes it possible to combine the dissolution of the glue at the level of the bonding points between threads, releasing any non-water-soluble threads (for example of PE), and the dissolution of the glue on the surface of the threads of water-soluble PVA , thus allowing the dissolution of the latter. This allows the disintegration of the grid (dissolution of the PVA and release of non-water-soluble threads that may be present) during a repulping-type process. The only non-water-soluble threads (for example made of PE) possibly remaining are not problematic for the repulping process and installation, and in particular do not fundamentally interfere with the operation of the agitation devices, such as the blades of an agitator, the causes the grid structure to no longer exist. During the repulping process, the grid is therefore easily and quickly disintegrated, as is also the paper with which it may be associated. In the embodiment in which the longer sides of the elemental pattern of the grid are formed by the warp threads, the grid is designed to be formed of a maximum of PVA threads and a minimum of water-insoluble threads , for example PE or the like. But we will prefer a grid exclusively made up of PVA threads for a total dissolution.

The thickness of the grid is equal to the thickness of the threads essentially of this grid, except in the quasi-point zones where at least two of the threads intersect or intersect, overlapping in the direction Z, zones in which the thickness of the grid is locally increased at most as many times as the number of wires overlap. By way of non-limiting example, the thickness of the wires, and therefore the thickness of the grid, apart from the overlapping zones of several wires, perhaps of the order of a hundred or a few hundred micrometers, or even more, in particular according to the title of the sons. This thickness can thus be between about 40 and about 400 mhi, preferably between about 60 and about 300 µm. Advantageously, the weight of the grid is between approximately 2 and approximately 300 g/m ² , preferably between approximately 3 and approximately 100 g/m ² .

In one embodiment, the grid is associated with at least one nonwoven support by the hot-melt adhesive to form a complex (grid+nonwoven). Preferably, the nonwoven also consists entirely of water-soluble PVA short fibers. Alternatively, the nonwoven is partially made of PVA water-soluble short fibers. In one embodiment, the nonwoven also comprises or consists of short polyester (PE) and/or glass fibers. The nonwoven can further comprise a binder as is known per se. This binder is advantageously a water-soluble binder under the conditions of dissolution of the PVA threads and of the PEG adhesive. This binder may in particular be based on PVA or PEG.

In another embodiment, the grid is associated with at least one paper support by the hot-melt glue to form a complex (grid+paper). Preferably, the paper is paper with a weight of 10 to 300 g/m ² , preferably 20 to 150 g/m ² , preferably 30 to 100 g/m ² . It may in particular be a Kraft paper.

The grid or the complex (grid + nonwoven) or the complex (grid + paper) form reinforcements which can be used to mechanically reinforce a composite incorporating it, typically by increasing the resistance of the composite to tearing. They can constitute finished or semi-finished products, stored in the form of sheets or, better, rolls.

In particular, these reinforcements are intended to reinforce composites made from sheets of paper. Paper in the generic sense of the term and in this application, unless otherwise specified, refers to both paper and cardboard. We can talk about reinforced paper. It may in particular be a Kraft paper. At the same time, as will have been understood, the grids according to the invention will greatly improve the mechanical and resistance properties of the reinforced papers incorporating them.

The present invention therefore also relates to a product or composite, preferably recyclable, comprising at least one grid as described here. Without having to repeat it, and without indication to the contrary, in what follows, the term “grid” will be understood to mean a single grid, or a complex (grid+nonwoven) or a complex (grid+paper). In particular, the composite comprises at least two sheets of paper. The sheet or sheets of paper confer all or part of the shape of the composite, it being understood that the composite can be a finished product (for example envelope, packaging) or a semi-finished product (composite sheet), in particular intended to form a product finished such as an envelope or wrapper. The composite comprises in particular two sheets of paper, at least one grid according to the invention placed between the two sheets, the assembly being able to be held together by an assembly glue. The assembly glue can be a glue usually used for making envelopes reinforced with a grid, for example a polyethylene glue. Alternatively, the assembly adhesive may be a hot-melt adhesive, in particular made of polyethylene glycol (PEG) or of methyl ether of poly(ethylene glycol) (MPEG) or of dimethyl ether of poly(ethylene glycol). Alternatively, the hot-melt adhesive can be formed from a mixture of at least two of the above polymers.

In one embodiment, the surface of the grid is identical in dimensions with one of the sheets of paper, and grid and paper are laid out with their four edges coinciding. Preferably the second sheet of paper is also of the same dimensions and also coincides with the grid and the first sheet.

In another embodiment, the grid has dimensions smaller than those of the sheets of paper, namely in one direction or in both directions in the plane of the composite. The sheets of paper will then be on at least one edge in direct contact and without grid interposition. In other words, the grid being of dimensions (area) lower than the sheets of paper, the sheets will be in direct contact without grid in places where the grid is not present.

In another embodiment, the grid is arranged astride an edge of one or both sheets of paper, and preferably the grid then also straddles the edge of another sheet of paper or two sheets arranged close to the previous ones, preferably edge to edge. The grid then extends in contact with at least two contiguous sheets of paper on the same plane, and in particular sandwiched between these and two other sheets of paper.

It is understood that the grid(s) can be arranged in different ways with respect to the sheets of paper, in order to place the reinforcement over the entire extent of the composite or in certain parts of the composite.

Preferably, a continuous layer of glue embedding the grid is present between the sheets of paper arranged on either side of the grid, this layer providing the structure of the composite. In the composite or product, the glue is in a dried or frozen state. It was mentioned above that it could be a polyethylene adhesive. Alternatively, the assembly adhesive may be a hot-melt adhesive made of polyethylene glycol (PEG) or of poly(ethylene glycol) methyl ether (MPEG) or of poly(ethylene glycol) dimethyl ether. Alternatively, the hot-melt adhesive can be formed from a mixture of at least two of the above polymers. Alternatively, if the grid has been associated beforehand with at least a first paper or non-woven support by the hot-melt glue to form a complex (grid + paper) or (grid + non-woven), the second layer of continuous glue is present from only one side of the grid (since the other side is glued to the first paper or non-woven support by the hot-melt adhesive), this layer contributing to the structure of the composite. In the composite or product, the glue is in the dried or hardened or frozen state. It was mentioned above that it could be a polyethylene glue. Alternatively, the assembly adhesive may be a hot-melt adhesive made of polyethylene glycol (PEG) or of poly(ethylene glycol) methyl ether (MPEG) or of poly(ethylene glycol) dimethyl ether. Alternatively, the hot-melt adhesive can be formed from a mixture of at least two of the above polymers.

The composite of the invention is intended in particular to form paper, envelopes, containers, shipping bags (mailer bags), packaging and/or packaging sheets and cardboard. They are intended to contain and protect products of all kinds, particularly in the event of transport or storage. They can also be used to package products of any kind for transport or storage and to protect and/or preserve them. A distinction is made between corrugated papers, which are used to manufacture corrugated cardboard, flexible packaging papers and flat cardboard. The paper may in particular be of the Kraft type.

The invention therefore also relates to papers, envelopes, packaging, containers, shipping bags, sheets and cardboard, comprising or formed from one or more composites according to the invention.

The grid and the complexes of the invention are also intended to form reinforced adhesive tapes or tapes by integrating the grid or the complex into the tape structure, forming a composite. These ribbons or strips may be formed of an integrated grid sandwiched between two strips of paper, in particular Kraft paper, an adhesive, in particular a hot-melt adhesive according to the invention ensuring the sandwich assembly, while one side of the ribbon or strip thus formed receiving the adhesive material giving the strip or tape its adhesive character, as is known per se.

As a variant, the tape or band consists of a complex according to the invention, (grid+paper) or (grid+nonwoven), in the form of a band or ribbon. This semi-finished product is then intended to be assembled with a strip of paper, in particular Kraft paper, using an adhesive, in particular a hot-melt adhesive according to the invention, ensuring a sandwich assembly with the grid placed in the center. As before, one face of the tape or tape thus formed receives the adhesive material giving the tape or tape its character as an adhesive, as is known per se. The bands or ribbons have the usual width dimensions for these products. This width may in particular be between approximately 1 or 2 and approximately 15 cm, more particularly between approximately 5 and approximately 10 cm.

In these ribbons, the mechanical resistance is essentially conferred by the warp threads of the grid or by weft threads oriented in a direction which moves away from a direction perpendicular to the warp threads and therefore to the longitudinal direction of the ribbon. To ensure the desired degree of mechanical resistance, the grid may incorporate warp threads according to a density of threads per cm and/or high count(s) suitable for obtaining this result. It is also possible to use a multidirectional grid, in particular tridirectional, capable of conferring a high degree of mechanical resistance and in different directions.

The present invention also relates to a process for preparing a grid according to the invention. The method may in particular comprise the superposition of at least two, preferably three, layers of yarns, the constituent yarns of at least one of these layers being oriented in a direction different from that of the constituent yarns of the other layers and cross them at crossing points to form an elementary grid pattern, at least one of the layers being made of water-soluble yarns. The process comprises the application of the molten (water-soluble) hot-melt glue, in particular in the fluid or liquid state, to the surface of the superposition of layers. To do this, the glue is applied at a temperature at which it is in a fluid or liquid state, therefore at a temperature above its melting point. Once this application of glue has been carried out, cooling is carried out so that the glue hardens or freezes, thanks to which a grid is obtained in which the crossing points are glued. The various characteristics mentioned elsewhere, in particular those relating to the composition of the yarns and of the glue, are applicable to the process.

The hot-melt adhesive is in particular deposited in the molten state (hot-melt) over the entire surface of the overlapping layers. This can be done by means of a molten glue transfer roller or by any other suitable means. It is possible in particular to use a device comprising a tank containing the glue in the molten state, and two parallel rollers, one serving as a licking roller dipping in the molten glue, while the superposition of layers is caused to pass between the two rollers. applying adequate pressure to the forming grid, before cooling the glue (which sets or hardens). The grid can be calendered at a temperature at which the hot melt glue is softened, in order to reduce the thickness of the grid, including the wires.

The present invention also relates to a process for the preparation of a complex (grid+nonwoven). The hot-melt adhesive is in particular deposited in the molten state (hot-melt) over the entire surface of the overlapping layers. This can be done by means of a molten glue transfer roller or by any other suitable means. It is possible in particular to use a device comprising a tank containing the glue in the molten state, and two parallel rollers, one serving as a licking roller dipping in the molten glue, while the superposition of layers and of the nonwoven is brought to pass between the two rollers applying adequate pressure to the complex being formed, before hardening by cooling the glue (which freezes or hardens). A calendering step can be carried out between the deposition and the hardening of the adhesive to improve the cohesion between the grid and the nonwoven. Alternatively, a calendering step can be carried out after the deposition and after the glue has hardened to improve the cohesion between the grid and the nonwoven. Alternatively, two calendering steps can be carried out, one between the deposition and the hardening of the adhesive and the other after the adhesive has hardened to improve the cohesion between the grid and the nonwoven.

The present invention also relates to a process for the preparation of a complex (grid + paper). The hot-melt adhesive is in particular deposited in the molten state (hot-melt) over the entire surface of the overlapping layers. This can be done by means of a molten glue transfer roller or by any other suitable means. One can in particular use a device comprising a tank containing the glue in the molten state, and two parallel rollers, one serving as a licking roller dipping in the molten glue, while the superposition of layers and paper is caused to pass between the two rollers applying an adequate pressure to the complex in formation, before hardening by cooling the adhesive (which freezes). A calendering step can be carried out between the deposition and the hardening of the glue to improve the cohesion between the grid and the paper. Alternatively, a calendering step can be carried out after the deposition and after the glue has hardened to improve the cohesion between the grid and the paper. Alternatively two calendering steps can be carried out, one between the deposition and hardening of the glue and the other after hardening of the glue to improve the cohesion between the grid and the paper.

In these different processes for manufacturing or applying hot-melt glue, for its application, the glue is heated to a temperature above its melting point. Advantageously, the glue is heated to a temperature about 10 to about 30°C above the melting point. The hardening of the glue is then ensured by lowering the temperature of the glue, in particular by bringing the grid to room temperature or by operating a cooling on the production line.

The invention will be better understood on reading the following description, given solely by way of example and made with reference to the drawings in which: FIG. 1 represents a grid according to the invention.

Figure 2 shows the grid of Figure 1, in section along the line l-l.

As illustrated in Figure 1, the reinforcement grid 1 has a general bidirectional shape defining a plane, when it is laid flat as in Figure 1. In the case illustrated in the figures, it is the XY plane . In the present example, the XY plane is attached to grid 1. Of course, any mention of a plane applied to this grid 1 must be considered for the grid when it is in a planar form, in particular unwrapped, as is the case in Figure 1.

Grid 1 comprises an assembly of wires 2 and 3. Each of these wires is designed to be straight when grid 1 is flat. The wires 2 and 3 are arranged relative to each other by repeating, in the plane of the grid, a pre-established elementary pattern, which is rectangular. The longitudinal son 2 are spaced from each other. Similarly, the transverse son 3 are spaced from each other. Thus, through free spaces are provided.

The expression “grid” refers to a network of wires linked at their intersections. A grid is not necessarily similar to a fabric, insofar as the connection between the threads is not achieved by simple interlacing, but by a bond of the glue type, the threads not necessarily being crossed or interlaced according to the direction Z and being generally distributed more loosely than for a fabric, in order to leave a macroscopic empty space at the heart of each elementary pattern, for example of polygonal, square, parallelepipedic, triangular or other simple shape. In the case presented in FIG. 1, there is simply superposition and bonding at the crossing points.

Among the wires of the grid 1, there are transverse wires 3, extending parallel to the direction X, or at least in an orientation which has a small angle, different from 90° with this direction X, and longitudinal wires 2, extending parallel to the Y direction. In the preferred embodiment of FIG. rectangular or square pattern, so that the transverse threads 3 are parallel to the X direction and the longitudinal threads 2 parallel to the Y direction. Alternatively, the angle at which the threads cross is between 45 and 90°. In this case, the longitudinal wires are parallel to the Y direction, while the transverse wires are not parallel to the X direction, and have an angle between 0° and 45° with this X direction.

The rectangles formed by the wires 2 and 3 have sides of different lengths, the sides 4 for the wires 2 being twice as long as the sides 5 for the wires 3. These values can be varied. Figure 2 is a sectional view along the line II of Figure 1. We see that in fact, the grid 1 includes a second series or layer of longitudinal son 6, which were not visible in Figure 1, because they are exactly superimposed on the wires 2. There are therefore longitudinal rectilinear wires 2 and 6, and transverse rectilinear wires 3, the latter being arranged at a right angle with respect to the longitudinal wires 2 and 6 and being placed between the latter in the Z direction. More precisely, the threads 2 and 6 are parallel and substantially overlapping so that the threads 2 and 6 are linked two by two to the threads 3 by the same bonding points.

For example, grid 1 measures between 1 cm and 10 m, in the transverse direction X, that is to say in width. Grid 1 advantageously measures several meters or tens of meters in the longitudinal direction Y, that is to say in length. More generally, the grids of the invention, like the grid 1, have an elongated dimension along the longitudinal wires and a shorter dimension along the transverse wires or along the transverse direction X. Due to their relatively long length, prefers to provide the grids of the invention, such as the grid 1, in the form of a roll, which can be unrolled for its subsequent use, for example for the manufacture of a composite. To form the roll, the grid is wound around a winding axis perpendicular to the longitudinal direction Y, that is to say that the winding axis is parallel to the transverse direction X. Preferably, the grids of the invention, like the grid 1, are flexible enough to be rolled up.

The manufacture of the grids of the invention, such as the grid 1, can be carried out on industrial lines suitable for the production of grids. Depending on the choices made on the line, the longitudinal threads (threads 2 and 6 for grid 1) are warp threads and the transverse threads (threads 3 for grid 1) are weft threads. The production process can advantageously be a continuous process, from the warp yarn supply reels, to the grid storage roll (roll-to-roll). As an example of a line for manufacturing a grid, those skilled in the art may refer to EP 3 023 303.

The dimensions of the grids of the invention, like the grid 1, are adapted according to the type of use, and in particular the dimensions of the composite to be produced. In particular, in the case of a paper envelope, provision is made for the grid to have dimensions similar to those of the two sheets of paper or of the two sides of the same sheet of paper between which it must be interposed. Coming from a grid roll, this will require cutting the grid at least transversely to the Y direction to cut the grid coupon to the desired size. Alternatively, the grids of the invention, like the grid 1, can be provided in a form other than a roll, in particular flat, with a length of between a few centimeters or tens of centimeters and a few meters.

For the implementation of a process for manufacturing a composite, a layer of binder or glue is preferably applied to the surface of a first sheet of paper facing upwards. The grid 1 or another grid of the invention is then placed on this layer of binder or glue, in particular by embedding it in this layer. Provision may be made to cover the grid with binder or additional glue, to complete the layer of binder or glue and ensure that the grid is embedded in this layer. A second sheet of paper is then placed on this grid coated with glue or binder. After a time of pressing and hardening of the glue or drying, a composite is obtained, which can then be used to form an envelope or any other packaging.

Example 1: Examples of glues. [Table 1]

The protocol is as follows for the evaluation of the solubilization time in water at 60°C. A volume of 40 ml of water is placed in a 100 ml beaker. The beaker is placed on a hot plate. The solvent is stirred with a stirring paddle at 700 rpm. The water is heated to 60°C. A mass of about 2 grams of the glue is immersed in water. Once the glue is in the water, a stopwatch is started to measure the time required to obtain a perfectly clear solution, and therefore the complete solubilization of the glue.

Example 2: Solubility of the PVA fiber in water at 60°C. The experiments were carried out on the following PVA fibres. The hydrolysis rate was measured by proton NMR in deuterated DMSO. The melting temperature and the crystallization temperature were measured by DSC.

The NMR measurements were carried out on a Brucker Neo 600 MHz NMR spectrometer. A mass (approximately 20 mg) of sample is taken and then DMSO-d6 is added in order to obtain a content of 0.3%. Chemical shifts are measured in ppm and are calibrated against the deuterated solvent peak (2.50 ppm). The intensity of the signals makes it possible to calculate the rate of hydrolysis according to the following scientific article: G. van der Velden and J. Beulen, 300-MHz 1 H-NMR AND 25-MHz 13C NMR Investigations of sequence distributions in vinyl alcohol -vinyl acetate copolymers, Macromolecules, (1982), 15, 1071-1075. The table below describes the assignments of the peaks according to their chemical shifts on the ¹ H NMR spectrum for each type of proton resulting from a PVA polymer bearing acetate groups and alcohol groups resulting from hydrolyzed acetate groups. [T able 2]

By integrating the area (A) of the peaks and applying the formulas described below, it is possible to calculate the molar percentage in acetate groups (%acetate), then the hydrolysis rate of the PVA polymer in molar percentage (% hydrolysis = %alcohol).

%acetate = [ (ACH3/3)/(ACH2/2) + (AcHOAcetate)/(AcH2/2) + (AcHOAcetate)/(AcHOAcetate+AcHOH) + (ACH3/3)/ ( AcHOAcetate+ ACHOH) ] X 1 00 / 4

%hydrolysis = %alcohol = 100 - %acetate

The DSC measurements were carried out on a Mettler-Toledo DSC 3+ device under nitrogen with the following method: a 10-minute plateau at 0°C, an initial rise in temperature from 0 to 150°C, a drop from 150 to 0 °C, a second rise in temperature from 0 to 260°C and a fall from 240°C to 0°C.

[Table 3]

The protocol is as follows to determine the solubilization time. A volume of 40 ml of water is placed in a 100 ml beaker. The beaker is placed on a hot plate. The solvent is stirred with a stirring paddle at 700 rpm. The water is heated to 60°C. A length of about 5 cm of the PVA yarn is immersed in water. Once the PVA thread has been immersed in water, a stopwatch is started to measure the time required to obtain a perfectly clear solution, and therefore the complete solubilization of the PVA thread.

[Table 4]

Examples 3 to 6: Manufacture of grids and complexes (grid + kraft paper):

The grids and complexes (grid + kraft paper) were manufactured on an industrial pilot line. The polyester fiber has a count of 76 dtex and a breaking tenacity of 4.6 cN/dtex (NF EN ISO 2062). The PVA fiber is Nitivy's SL110 fiber with a count of 110 dtex and a breaking tenacity of 4.7 to 5.7 cN/dtex. The PEG used is RENEX PEG 2000 from Croda with a molar mass of approximately 2000 g. mol ¹ (ISO 13885-3 with PEG standards). The PEG is heated between 50 and 100°C, ideally between 55 and 60°C in the pilot line tank. The deposit cylinders are heated between 50 and 70°C, ideally between 55 and 60°C. Kraft paper has a weight of 60 g/m ² .

[T able 5]

The protocol for evaluating behavior in water at 60°C is as follows. A volume of 100 ml of water is placed in a 200 ml beaker. The beaker is placed on a hot plate. The solvent is stirred with a stirring paddle at 700 rpm. The water is heated to 60°C. A sample of about 5 cm in length and 5 cm in width and 5 cm in length of the grid or complex (grid + kraft) is immersed in water. Once the grid is immersed in the water, observations are made and a stopwatch is started.

Example 7: Tear Resistance

This example compares a single sheet of kraft paper, a "kraft/kraft" complex (two sheets of kraft paper glued one against the other), and a composite according to the invention "kraft + grid / kraft", formed from complex of example 6 associated with a sheet of kraft paper, in a glued sandwich of two sheets of kraft paper enclosing the grid. The same cellulose acetate-based adhesives are used in the different samples. The kraft paper is also the same in the different samples (grammage 60 g/m ² ). The tear values given are the maximum breaking forces, in Newtons (N). The tearing measurements were carried out according to standard NF EN ISO 13937-2 of May 2000: Textiles - Tearing properties of fabrics - Part 2: determination of the tearing force of the trousers test specimens (Single tear method), test specimens 8.2 .1 as per standard.

Example 8: Gummed tape

For an application of the gummed tape type, preference will be given to a grid with a three-way geometry in order to better distribute the forces applied to the tape. However, bidirectional grids can also be envisaged, even if in this case, the weft threads will not participate in a significant way in the mechanical effort. It was explained above that the person skilled in the art can play on the title of the wires of the grid, their tenacity and/or on the density of the wires, to adjust the mechanical resistance of the ribbon, like all the other achievements described in this application. The mechanical tensile strength in the warp direction is indeed an important characteristic of these tapes, it is therefore possible to play on the tenacity, the title and/or the density of the warp yarns to obtain sufficient levels of resistance.

A resistance of at least 17 daN/5 cm (measured according to standard NF ISO 40606) can be sought in the chain. For reference, the resistance of the complex of Example 6 is 2.8 daN/5 cm.

The grid resistance is measured on the grid alone, without complex. It is also possible to calculate the resistance of the grid alone from the resistance of a warp thread, multiplied by its warp density and by 5 cm.

Design example: - With PVA SL yarn (Nitivy) from Table 3, in 110 dtex version: three-way grid with a density of 7 warp yarns per cm. The chain resistance of this grid is expected to be at least 18.1 daN/5 cm.

With the PVA SF yarn (Nitivy) from Table 3, in the 660 dtex version: three-way grid with a density of 2 warp yarns per cm. The chain resistance of this grid is expected to be at least 21.8 daN/5 cm.

The gummed adhesive tapes used in current practice have widths of 40, 50, 60 or 70 mm, or 1 to 3 inches (thus 2.54 to 7.62 cm). It is possible to produce gummed adhesive tapes, having in particular its width dimensions, by complexing a grid according to the invention, for example a bidirectional grid formed from one or the other of the two examples of threads mentioned above, laminated (stuck) between two krafts, then the standard adhesive to give the adhesive character to the tape is applied to an outer face of one of the kraft papers of the complex.

It is also possible to achieve this by employing a bidirectional grid according to the teaching of this application, with adjustment of the tenacity, the title and/or the density of the warp yarns to obtain sufficient levels of resistance.

Claims

1. Textile grid formed of at least two, preferably three, layers of threads forming an elementary pattern formed by constituent threads of this layers respectively oriented in different directions and crossing at crossing points to form the elementary pattern, where the yarns of the sheets are glued together at their points of intersection by a polymeric glue, characterized in that at least one of the sheets is formed of water-soluble polyvinyl alcohol (PVA) yarns, in that the polymeric glue is a glue water-soluble hot-melt implemented in the molten state when assembling the layers of threads, then hardened or congealed to ensure the bonding of the crossing points, and in that the threads made of water-soluble polymer and the water-soluble hot-melt glue are soluble in water or an aqueous solution in the same temperature range, in particular at a temperature between 10 and 80°C, preferably between 20 and 70°C.

2. Textile grid according to claim 1, characterized in that the hot melt adhesive is based on PEG.

3. Textile grid according to claim 2, characterized in that the hot-melt adhesive comprises a PEG comprising a polyethylene glycol having two ends comprising a hydroxyl group, a methyl ether of poly (ethylene glycol) or a dimethyl ether of poly (ethylene glycol) , or a mixture of at least two of these compounds.

4. Textile grid according to claim 2 or 3, characterized in that the PEG has a molecular weight of 1000 to 10000 g. mol ^-1 , in particular from 1200 to 8000 g. mol ^-1 , preferably from 1500 to 5000 g. mol ^-1 .

5. Textile grid according to any one of claims 1 to 4, characterized in that one of the layers is formed of polyester (PE) yarns.

6. Textile grid according to any one of claims 1 to 5, characterized in that it comprises at least one layer of warp yarns, preferably two layers of warp yarns, these warp yarns being made of PVA, and that it comprises a layer of weft threads, these weft threads being preferably made of PVA or PE, the warp threads and the weft threads being respectively oriented in different directions and crossing at crossing points to form the basic pattern of the grid.

7. Textile grid according to any one of claims 1 to 6, characterized in that the grid is bidirectional and the elementary pattern of the grid is a rectangle with two sides formed by warp yarns and two sides formed by warp yarns. weft, the sides formed by the warp yarns being longer than the sides formed by the weft yarns.

8. Textile grid according to any one of claims 1 to 6, characterized in that the grid is three-way with groups of yarns oriented in three different directions.

9. Textile grid according to any one of claims 1 to 8, characterized in that it is glued to a nonwoven, preferably water-soluble, and/or to a sheet of paper.

10. Composite comprising a textile grid according to any one of the preceding claims and at least one sheet of paper or cardboard to the surface of which the grid is glued, preferably the grid is glued between two sheets of paper or cardboard.

11. Article, in particular envelope, container, shipping bag, sheet, adhesive tape or packaging, comprising or formed from at least one composite according to claim 10.

12. A method of manufacturing a textile grid according to any one of claims 1 to 9, comprising the superposition of at least two layers of threads whose constituent threads are respectively oriented in different directions and intersect at points of crossing to form an elementary grid pattern, at least one of the layers being made up of water-soluble threads, the application of a molten water-soluble hot-melt adhesive, in particular made of PEG, to the surface of the superposition of layers, then the hardening of the glue by cooling, thanks to which a grid is obtained in which the crossing points are glued.