BE1028939B1 - APPARATUS AND METHOD FOR PRODUCING A POLYOLEFIN CLOT, AND METHOD FOR CONTROLLING THE SAME APPARATUS - Google Patents

Abstract

Apparatus for the production of a polyolefin web consisting of at least one layer, comprising an extruder and a flat die associated with the extruder and comprising an opening, intended for the extrusion of the web by pressure and hot casting d a mixture comprising a polyolefinic matrix comprising at least one polymer, and optionally at least one inorganic and/or organic filler, a drive cylinder comprising a metallic outer surface, and a counter-cylinder associated with the drive cylinder and comprising a rubberized outer surface, intended to pre-stretch the extruded web, a means for cooling at least one of said cylinders, so as to cool and at least partially solidify the pre-stretched web, and a means for adjusting at least one of the following quantities: speed, temperature of at least one of said cylinders, distance between the drive cylinder and the counter-cylinder, distance between said cylinders and the slot die opening, slot die width. At least one of said cylinders is replaceable. The apparatus further includes a means for lifting and a means for holding the replaceable cylinder connected to the replaceable cylinder and configured to allow replacement of the cylinder.

Description

APPARATUS AND METHOD FOR PRODUCING A POLYOLEFIN MOP, AND CONTROL METHOD OF SAID DEVICE

TECHNICAL FIELD The invention relates to an apparatus and a process for producing a sheet from a polyolefinic matrix, as well as a method for controlling such an apparatus.

STATE OF THE ART It is known to produce flexible and flexible films, microporous or not, having the capacity to breathe, that is to say to be permeable to gases and to water vapor but impermeable to aqueous liquids, or not, that is to say to be impermeable to gases and to water vapor and to aqueous liquids. It is also known to combine them with other materials such as macro-perforated films, non-woven fabrics, woven fabrics and papers, these other materials providing the mechanical characteristics and the desired feel, in particular the textile feel. . Methods for producing such films already exist. The latter are obtained after stretching sheets produced from a polyolefinic matrix. However, the corresponding production devices do not allow easy and efficient adaptation to different customer requirements, such as a given width and thickness of the film obtained, or else a specific mechanical and/or optical characteristic or a specific feel of the film. . Thus, a single production device according to the state of the art does not currently make it possible to produce a wide variety of films, each having very specific dimensions and characteristics, with a view to satisfying the different needs of customers. This lack of flexibility of current production devices results in increased production time and cost. Therefore, it is necessary to propose an apparatus as well as a process for producing a sheet from a polyolefinic matrix which overcomes the aforementioned problems.

International patent application WO 00/05295 A1 in the name of the applicant describes such an apparatus and such a method for producing microporous films. DISCLOSURE OF THE INVENTION

The object of the invention is to propose an apparatus and a process for producing a web from a polyolefinic matrix allowing better adaptation to the numerous and different requirements of customers in terms of dimensions and characteristics of the webs produced, and a method of controlling the apparatus to reduce the time and cost of producing said webs.

According to a first aspect of the invention, an apparatus is proposed for the production of a web from a polyolefinic matrix comprising at least one polymer, said web consisting of at least one layer.

Said device comprises an extruder and a flat die associated with the extruder and comprising an opening, intended for the extrusion of the sheet by pressure and hot casting of a mixture comprising said polyolefin matrix and optionally at least one mineral filler and / or organic, and a drive cylinder comprising a metallic outer surface, and a counter-cylinder associated with the drive cylinder and comprising a rubberized outer surface, intended to pre-stretch the extruded sheet.

Said apparatus further comprises a means for cooling at least one of the drive cylinder and the counter-cylinder, so as to cool and at least partially solidify the pre-stretched web, and a means for adjusting at least one of the following quantities: speed and temperature of at least one of the drive cylinder and the counter-cylinder, distance between the drive cylinder and the counter-cylinder, distance between the said cylinders and the slot die opening, slot die width.

At least one of the drive cylinder and counter cylinder is replaceable.

The apparatus further includes a means for lifting and a means for holding the replaceable cylinder connected to the replaceable cylinder and configured to allow replacement of the cylinder.

Embodiments of the invention are based inter alia on the inventive idea of an apparatus for - the production of a web from a polyolefin matrix as described above wherein the adjustment means allows the apparatus a great flexibility vis-à-vis the many and different requirements of the customers in terms of dimensions and characteristics of the tablecloths produced.

Indeed, adjusting the speed of at least one of the drive cylinder and the counter-cylinder makes it possible to control the thickness of the pre-stretched web, and adjusting the temperature of at least the one of the drive cylinder and the counter-cylinder makes it possible to control the cooling and at least partial solidification of the pre-stretched web.

However, the thickness and the cooling of the pre-stretched web influence the mechanical and/or physico-chemical characteristics of the web thus produced.

Furthermore, the adjustment of the distance between said cylinders allows control of the thickness of the layer thus produced, and the adjustment of the distance between said cylinders and the opening of the flat die allows the control downstream of the width of the web thus produced.

Indeed, at the exit of the opening of the flat die, the width of the extruded web tends to decrease.

This decrease in width is specific to the molecular structure of the polymers used in the polyolefin matrix, and can be higher or lower from one polymer to another.

It is therefore possible to control the distance between said cylinders and the opening of the flat die in order to thus control the width of the ply during contact of the ply with said cylinders.

Finally, the adjustment of the width of the flat die allows the upstream control of the initial width of the sheet to be extruded, before contact with said cylinders.

In addition, the replaceable cylinder having substantial dimensions and weight, such a means of elevation and such a means of holding the cylinder allow easy and robust mechanized replacement of the cylinder to be replaced.

Typically, one of the cylinders to be replaced is extracted from the pre-stretch bench which it forms with the other aforementioned cylinder, is lifted by the lifting means, is held in the air by the holding means while waiting its replacement or maintenance, then is either placed on the ground if it is replaced, or placed back in position in the pre-stretch bench after maintenance.

It should be noted that the two aforementioned cylinders can be replaced, simultaneously or one after the other, and this by the same lifting and holding means.

Thus, the present invention constitutes an improvement of the invention described in the international patent application WO 00/05295 A1 mentioned above, in that it proposes an apparatus for the production of a polyolefin web capable of adapting to a large number of requirements from customers in terms of dimensions and characteristics of the webs produced by means of adjusting at least one of the aforementioned quantities.

Moreover, the present invention provides greater flexibility to the production apparatus thanks to the possibility of replacing at least one of the driving cylinder and the counter cylinder.

Thus, it is possible to adapt the type of cylinder used according to customer requirements in terms of dimensions and desired properties, particularly in terms of the width of the sheets produced.

The production apparatus of the present invention also makes it possible to reduce the time and cost of producing said webs.

In the context of the invention, the word "sheet" refers to a strip, or ribbon, composed of at least one layer and formed by extrusion, pre-stretching, cooling and at least partial solidification of the aforementioned mixture.

A web thus produced has specific dimensions, such as a given width and thickness, as well as specific mechanical and/or optical properties such as a given resistance to deformation, a given reflection of incident light or a given opacity, etc. .

A web thus produced also has specific physico/chemical properties, for example a hydrophobic character due to the use of polymers in the polyolefinic matrix.

Combined with other materials such as non-woven fabrics, the web can have additional characteristics.

For example, when combined with a hydrophilic nonwoven fabric, by lamination among other things, the sheet, originally hydrophobic on both sides, can become hydrophilic on one of its sides. According to an exemplary embodiment, the sheet is intended for the manufacture of a microporous film permeable to gases and impermeable to aqueous liquids. More particularly, the web can be intended for the manufacture of a soft, flexible and breathable polyolefinic microporous film, formed of at least one layer, permeable to gases and water vapors but impermeable to aqueous liquids, of high mechanical characteristics and with a pleasant touch. Thus, the sheet is capable of being stretched subsequently with a view to reducing its thickness and modifying its mechanical and/or optical and/or physico-chemical characteristics, so as to produce a microporous film. Such a microporous film can be used for the production of surgical material such as surgical gowns, or in an industrial sector such as that of underlayments, as protection and insulation of buildings.

As the sheet resulting from the pre-stretching operation does not typically have the characteristics desired for the microporous film such as, in particular, a low thickness, a microporosity giving it the ability to breathe while being impermeable to aqueous liquids, or mechanical properties necessary for its subsequent use, it is subjected, after having been heated to the appropriate temperature, by calendering for example, to a drawing operation. This operation can be carried out between at least two pairs of rollers, forming a drawing bed, rotating at different speeds. A first pair of rollers constitutes the call pair which simultaneously plays the role of delivering the web to be stretched and possibly of helping to maintain the delivered web at the desired temperature for stretching. A second pair of rollers constitute the actual stretching torque of the web by applying to it the desired stretching rate, this rate being given by the ratio of the linear speeds delivered by the pair of stretching rolls and the pair of call. One or more pairs of subsequent rollers, downstream of said second pair of rollers, can complete the stretching of the web by applying the same stretching rate or other desired stretching rates to it. Thus, a succession of stretching steps alternating with heating and cooling steps, or called annealing steps, at the same temperature or at different desired temperatures, can be applied to the web with a view to obtaining a film microporous. Beyond the successive stretching(s), depending on the production process used, the microporous film can undergo an annealing heat treatment in order to control its shrinkage or even improve its dimensional stability at temperature.

The subsequent stretching of the web can be carried out directly after the pre-stretching, cooling and at least partial solidification stages, by a stretching bench located downstream of the device according to the invention.

Alternatively, the subsequent stretching of the sheet can be carried out by a device other than the device according to the invention, for example by a device belonging to a customer.

The customer can therefore apply the desired specific stretching to said pre-stretched, cooled and at least partially solidified webs, according to his objectives, his applications, and his own requirements. 5 To obtain a microporous film by stretching a web, the pre-stretched web can undergo substantial and practically complete cooling in contact with the drive roll and the counter roll.

This sheet is therefore subsequently reheated to a temperature which is sufficient and depends on the nature of the polyolefinic matrix to be able to be correctly stretched in the appropriate stretching zone, and transformed into a film having the expected characteristics.

This may typically be the case if the subsequent stretching is carried out by a device other than the device according to the invention, such as a device belonging to a customer.

Alternatively, the cooling of the web pre-stretched by the drive cylinder and the counter-cylinder can be partial and limited in a controlled manner to a temperature lying within the range of temperatures necessary for its stretching.

This technique makes it possible to prevent the constituent material of the sheet, which is initially in a quasi-isotropic state before pre-stretching, cooling and practically complete solidification, from undergoing internal physical modifications during these stages, in particular macromolecular deformations and /or a macromolecular orientation and/or an evolution of the crystallinity, which are fixed in the state, during the cooling.

This may typically be the case if the subsequent drawing is carried out directly by a drawing bench located downstream of the device according to the invention.

For example, the stretching of the sheet brought to the temperature required by the partial cooling can be carried out by traction, at the moment when its tangential separation from said drive cylinder occurs, said cylinder acting as a take-up roller. for stretching, as described in the aforementioned international patent application WO 00/05295 A1.

The microporous film produced after stretching the web can have different properties depending on the face concerned.

Thus, associated with other materials such as non-woven fabrics, the microporous film may have additional mechanical and/or optical and/or physico-chemical characteristics.

For example, associated with a non-woven fabric, inter alia by gluing after stretching of the web, the originally matt microporous film, that is to say not reflecting the incident light, on its two faces can have a reflective property of incident light on one of its faces.

More particularly, after stretching, glue can be applied, for example randomly, to one of the faces of the microporous film, and a nonwoven fabric having various properties can thus be glued to said face of the microporous film.

The complex formed by the microporous film,

the glue and the non-woven fabric can remain breathable, i.e. permeable to gases, while remaining impermeable to aqueous liquids. Such a complex based on a microporous film can for example be used for the production of surgical gowns.

According to another exemplary embodiment, the sheet is intended for the manufacture of a non-microporous film, that is to say a film resistant to the penetration of gases and impermeable to aqueous liquids. Such a film can therefore be both impermeable to gases and water vapor and impermeable to aqueous liquids. It should be noted that such a film may not be completely impermeable to gases. Thus, although the non-microporous film is resistant to gas penetration, a small amount can still pass through the film. Such a film does not require subsequent stretching of the sheet, unlike a microporous film. Indeed, as described above, it is the stretching of the web which gives a microporous characteristic to the film, which is obviously not desirable in the case of a non-microporous film. Such a non-microporous film can be used for the production of barrier films for surgical material such as for example sterile operating drapes.

The non-microporous film produced may have different properties depending on the face concerned. Indeed, associated with other materials such as non-woven fabrics, the non-microporous film may have additional mechanical and/or optical and/or physico-chemical characteristics. For example, combined with a hydrophilic nonwoven fabric, among other things by lamination without adding glue during the pre-stretching of the web, the side of the web in contact with the metal outer surface of the drive roll will have a matte property. , which does not reflect incident light, as well as a hydrophobic property, whereas the face of the sheet on which the hydrophilic nonwoven fabric is laminated, which is in contact with the rubberized outer surface of the counter-cylinder, may have a reflecting property of incident light and a hydrophilic property. These different optical properties depending on the face of the sheet concerned can be advantageous for a medical application of the non-microporous film, in particular for the manufacture of sterile drapes. Indeed, these different properties make it easy to recognize the outer face of the non-microporous film from its inner face, so as to use the sterile drape correctly. For a sterile drape, the outer face, which is not in contact with the patient, corresponds to the face - reflective and hydrophilic so as to absorb liquids such as blood during the operation. Thus, the medical profession can easily avoid contaminating the other side, the matte and hydrophobic inner side, in contact with the patient.

According to a preferred embodiment, the cooling means comprises a first cooling device integrated into the drive cylinder and intended to cool the drive cylinder.

Thus, the integration of the first cooling device within the drive cylinder allows a gain in volume of the production device. Also, the drive cylinder being made of metal, the transfer of heat from the sheet to be cooled to its outer metal surface, in contact with the sheet to be cooled, takes place efficiently thanks to good thermal conduction.

According to a preferred embodiment, the cooling means comprises a second cooling device external to the counter-cylinder and intended to cool the counter-cylinder.

Thus, the second cooling device being positioned outside the counter-cylinder allows better heat transfer from its rubberized outer surface, in contact with the sheet to be cooled, towards the outside of the counter-cylinder, because the counter- rubber cylinder does not enjoy optimal heat conduction.

According to an exemplary embodiment, said second cooling device comprises a water reservoir in contact with a lower part of the counter-cylinder. According to an exemplary embodiment, the device further comprises an element in contact with the outer surface of the counter-cylinder and intended to evacuate the cooling water from the outer surface of the counter-cylinder at the outlet of the second cooling device .

According to an exemplary embodiment, the flat die is provided with at least one lateral element insertable at at least one of the two lateral ends of the flat die and intended to reduce the operational width of the flat die.

According to another exemplary embodiment, the opening of the slot die is configured to be partially blocked at at least one of the two side ends of the slot die to reduce the operational width of the slot die.

Thus, the insertion of said side element or the partial blocking of the slot die opening does not reduce the physical width of the slot die, but rather its operational width. In other words, the working width of the flat die, which corresponds to an effective contact between the sheet to be extruded and the flat die, is reduced by the insertion of said side element or by the partial blocking of the opening of flat die to reduce the width of the extruded web. This side element or this partial blocking therefore makes it possible to adjust the width of the sheet to be extruded according to the customer's requirements. This side element can also be inserted at both ends of the flat die, the latter typically having an elongated shape and a thin thickness compared to its width,

in particular at its opening, which is typically located at a lower end of the slot die. This partial blocking can also take place at both ends of the flat die. According to a preferred embodiment, the apparatus further comprises a motor connected to at least one of the drive cylinder and the counter cylinder and intended to regulate the rotational speed of the cylinder. Thus, the motor allows fine adjustment of the speed of rotation of at least one of the cylinders, for example by using a gearbox, which allows precise control of the thickness of the web thus produced. According to a preferred embodiment, the outer surface of the drive cylinder is provided with a pattern selected from regular and irregular patterns, in relief, in hollow, intended to emboss the pre-stretched and cooled web.

Thus, during the pre-stretching of the web, its cooling regulated to a determined temperature and its at least partial solidification, said web can also undergo an embossing operation by means of the drive cylinder. In the latter case, the surface of the drive cylinder is provided with a regular or irregular pattern, raised or recessed, the most frequent forms of which may be lines in the longitudinal, transverse or diagonal direction with respect to the direction of advancement of the web, parallel or intersecting to form geometric figures, more or less open chevrons, sinusoids, teeth, or even figures such as polygonal or circular (hexagon, rhombus, circle, for example) , or randomly distributed figures. For example, the embossing of the pre-stretched web can be achieved by means of triangular or hexagonal patterns, thus allowing subsequent stretching along three axes corresponding to the three sides of the triangles or to the three pairs of opposite sides of the hexagons. According to another example, the embossing of the pre-stretched sheet can be carried out by means of patterns in the shape of quadrilaterals, such as diamonds, rectangles or squares, thus allowing subsequent stretching along two axes corresponding to the two pairs of sides opposites of quadrilaterals.

According to a preferred embodiment, the extruder is configured to extrude the web at a temperature between 170°C and 270°C. The temperature of the sheet is the result on the one hand of the extrusion itself, and on the other hand of the additional contribution of calories by differential heating of various zones, including the connecting tubes of the extruder to the flat die as well as the flat die itself. This temperature and its control allow the water table to be poured under good conditions of efficiency and quality. The pressure generated mainly by the rotation of the extrusion screw of the extruder allows the molten mixture comprising the polyolefinic matrix, and optionally mineral fillers and additives, to come out of the flat die according to the fluidity obtained by the temperature adequacy -types of polymer and according to the resulting width of the flat die. According to a preferred embodiment, the drive roll and counter roll are configured to pre-stretch the extruded web by a ratio in the range of 4 to 25, preferably between 5 and 10.

Indeed, the extruded web can be relatively thick at the exit of the flat die, of the order of a millimeter to tenths of a millimeter for the thinnest webs. Thanks to said cylinders, the thickness of the pre-stretched sheet decreases by a factor ranging from 4 to 25, preferably from 5 to 10, so as to obtain a pre-stretched sheet having a thickness of the order of a hundred microns, or even ten microns for the finest layers. According to a preferred embodiment, the apparatus further comprises a series of cylinders downstream of the drive cylinder and of the counter-cylinder, intended to roll up the pre-stretched and cooled web with a view to storing it.

In this way, the web can be wound on a cardboard or other mandrel, and is thus ready to be delivered to customers. According to a preferred embodiment, the apparatus further comprises a series of cutting elements downstream of the driving cylinder and the counter-cylinder, intended to cut the pre-stretched and cooled web to a determined width. In this way, a final check, and a final adjustment if necessary, of the width of the webs thus produced is possible, before delivery to the various customers. In addition, on leaving the pre-stretching, the ply may have a greater thickness at its lateral ends than at its center due to the extrusion of the ply through the flat die. This greater thickness can be removed using these cutting elements, before winding the sheet. Preferably, said cut out thickness can be reintroduced into the production apparatus in order to reduce the volume of production waste and save money.

According to a preferred embodiment, the extruder and the flat die are suitable for the extrusion of a multilayer sheet. Preferably, the thickness of the multilayer web at the outlet of the flat die is between 300 and 2000 μm.

According to an exemplary embodiment, the extruder comprises a plurality of extrusion units, each intended to extrude a mixture corresponding to each of the layers of different compositions. Preferably, the flat die is provided with a co-extrusion device intended to be fed by each of the extrusion units.

When the sheet thus produced after pre-stretching is formed of a single layer, this pre-stretched layer must have certain mechanical characteristics, in particular good tensile strength in order to withstand without damage the stresses to which it is subjected in its various applications. . This is why the polyolefinic matrix is essentially composed of at least one polymer meeting this mechanical strength requirement which, for this reason, requires a rather high density leading de facto to a high melting point. But this layer, which is the seat of certain internal tensions generated by a subsequent stretching operation, can present certain drawbacks. This is why it may be advantageous for the ply thus produced to be formed of several layers, called a multilayer ply, the main one having high mechanical strength (as mentioned in the case of a single-layer ply) associated with at least one other so-called specific layer, the polyolefinic matrix of which may be formed not only from the polymer(s) used to form the main layer and the secondary layers, but also from at least one specific olefinic polymer and/or copolymer by the effect provided to the layer containing it, such as a low density and therefore a lower melting point.

According to a preferred embodiment, the polyolefinic matrix is formed from polyethylene, PE, or from polypropylene, PP, or from a combination of the aforementioned polymers.

According to a second aspect of the invention, there is proposed a process for producing a web from a polyolefinic matrix comprising at least one polymer, said web consisting of at least one layer. Said method comprises the successive steps of the preparation of a mixture comprising said polyolefinic matrix and optionally at least one mineral and/or organic filler, the extrusion of the sheet by pressure and hot casting of the mixture by an extruder associated with a die plate comprising an opening, the selection of a drive cylinder comprising a metal exterior surface from a set of drive cylinders, and a counter cylinder associated with the drive cylinder and comprising a rubberized exterior surface from a set counter-cylinders, based on a predetermined set of rules,

the pre-stretching of the extruded web by the drive roll and the counter-roller, the cooling and at least partial solidification of the pre-stretched web, by means of at least one of the drive roll and of the counter cylinder. The method further comprises the adjustment of at least one of the following quantities during the pre-stretching, cooling and solidification stages: speed and temperature of at least one of the drive cylinder and the counter- cylinder, distance between the driving cylinder and the counter-cylinder, distance between said cylinders and the opening of the flat die, width of the flat die. The method further includes raising and holding at least one of the drive cylinder and the backing cylinder to allow replacement thereof.

According to an exemplary embodiment, the sheet is intended for the manufacture of a microporous film permeable to gases and impermeable to aqueous liquids. According to another exemplary embodiment, the web is intended for the manufacture of a non-microporous film resistant to the penetration of gases and impermeable to aqueous liquids, as described above. It is clear to those skilled in the art that the advantages described in connection with the embodiments of a production apparatus according to the first aspect of the invention apply to the embodiments of the production method according to the second aspect of the invention, mutatis mutandis. Furthermore, the embodiments of the invention are based inter alia on the inventive idea of a method of producing a web from a polyolefin matrix as described above in which it is possible to select a specific drive cylinder comprising a metallic outer surface, and a specific counter-cylinder associated with the drive cylinder and comprising a rubberized outer surface, based on a predetermined set of rules. Thus, the present invention constitutes an improvement of the invention described in the aforementioned international patent application WO 00/05295 A1, in that it proposes a process for producing a polyolefin web capable of adapting to a large number requirements from customers in terms of dimensions and characteristics of the webs produced thanks to the aforementioned selection, in addition to the adjustment of at least one of the aforementioned sizes. According to a preferred embodiment, the predetermined set of rules comprises the comparison between the width of said web and the width of a web produced directly before said web by said process.

Thus, the aforementioned selection is based on a comparison of width between two webs successively produced by the production method according to the invention. If the width of the previous ply is greater than that of the current ply to be produced, it can be decided for the production of the current ply to select the cylinders used for the production of the previous ply. In particular, in this case it can be decided to keep the same counter-cylinder for the production of the current layer. As for the driving cylinder, it can also be decided to select a cylinder having an outer surface provided with other patterns than those used for the production of the previous sheet, on the basis of another predetermined set of rules such as a subsequent stretching along different axes, for example biaxial.

On the other hand, if the width of the previous layer is less than that of the current layer to be produced, it can be decided for the production of the current layer to select other cylinders than those used for the production of the previous layer. In particular, in this case it may be decided to replace the counter-cylinder for the production of the current layer, or to ensure its maintenance before producing the current layer. In fact, in this case, the previous ply will have a greater thickness at its lateral ends than at its center due to the extrusion of the ply through the flat die. This greater thickness at the lateral ends of the extruded ply will have left marks on the rubber of the outer surface of the counter-cylinder. During the production of the current ply, having a width greater than that of the previous ply, the portion of the outer surface of the counter-cylinder which will have been marked by the production of the previous ply will be in contact with the current ply, this which will leave marks on the current tablecloth, rendering the tablecloth thus produced unsightly and not suitable for sale. In addition, this marking of the current web can alter its properties and therefore its quality.

Thus, in the second case, the counter-cylinder can either be replaced by a new counter-cylinder or at least one that does not show any marks on its outer rubber surface, or remove a thin outer film of rubber from the outer surface of the counter-cylinder, called rectification of the outer surface of the counter-cylinder, for example by abrasion, then to reposition the counter-cylinder at a good relative distance from the drive cylinder. Indeed, as the thickness of the counter-cylinder varies after removal of said thin outer film, the distance between the two cylinders also varies, as well as the tangential speed of the counter-cylinder due to the variation of its radius. Thanks to the adjustment of at least one of the aforementioned quantities by means of the production method according to the invention, a control of the speed of the counter-cylinder and/or of the drive cylinder and/or a control of the distance between Said rolls can be performed to ensure that the actual web will be produced by the process to parameters that meet customer requirements.

Preferably, the grinding of the outer surface of the counter-cylinder, to the dimensions of adequate roughness and flatness, is carried out using a machine, such as a lathe, installed in the building housing the production near this unit. Thus, it is not necessary to outsource the grinding of the outer surface of the counter-cylinder, which saves time and money while controlling quality. According to an exemplary embodiment, the extrusion step includes inserting at least one side member at at least one of the two side ends of the flat die.

According to another exemplary embodiment, the extrusion step comprises partially blocking the slot die opening at at least one of the two side ends of the slot die. According to a preferred embodiment, the method further comprises a step of embossing the pre-stretched and cooled sheet with a regular or irregular pattern, in relief or in relief, on the outer surface of the drive cylinder. According to a preferred embodiment, the temperature of the web at the exit from the extrusion step is between 170° C. and 270° C.

According to a preferred embodiment, the extruded sheet is pre-stretched according to a ratio comprised in the range 4 to 25, preferably between 5 and 10. According to a preferred embodiment, the method further comprises a step of winding of the web pre-stretched and cooled by a series of cylinders downstream of said cylinders with a view to storing it. According to a preferred embodiment, the method further comprises a step of cutting the pre-stretched and cooled web to a width determined by a series of cutting elements downstream of said cylinders.

According to a preferred embodiment, the extrusion step corresponds to an extrusion by casting of a multilayer fused sheet. Preferably, the thickness of the multilayer web at the outlet of the flat die is between 300 and 2000 μm. According to an exemplary embodiment, a mixture corresponding to each of the layers of different composition of the multilayer web is extruded by an extrusion unit of the extruder comprising a plurality of extrusion units. Preferably, the step of extruding each of said mixtures is followed by a step of co-extrusion of the multilayer sheet. According to a preferred embodiment, the polyolefinic matrix is formed from polyethylene, PE, or from polypropylene, PP, or from a combination of the aforementioned polymers. According to a third aspect of the invention, there is proposed a method for controlling the apparatus according to any one of the embodiments of the first aspect of the invention, comprising the successive steps of the preparation of several mixtures each comprising a polyolefinic matrix comprising at least one polymer, and optionally at least one mineral and/or organic filler, the production, comprising the extrusion, the pre-stretching, the cooling and the at least partial solidification, of several successive layers corresponding to the several mixtures according to the process according to any one of the embodiments of the second aspect of the invention, said successive webs being composed of at least one layer and having a decreasing width from a given web produced by said process to a web produced directly after said tablecloth. The method of controlling the device further comprises replacing the counter-cylinder after the production of the narrowest layer among said successive layers produced by said method, and before starting the method of controlling the device again.

It is clear to those skilled in the art that the advantages described in connection with the embodiments of a production apparatus according to the first aspect of the invention and of a production method according to the second aspect of the invention apply to embodiments of the device control method according to the third aspect of the invention, mutatis mutandis.

Furthermore, the embodiments of the invention are based inter alia on the inventive idea of a method of controlling the apparatus as described above in which it is possible to produce a succession of webs having a width decreasing, and to replace the counter-cylinder after the production of the narrowest ply before starting the device control process again.

Thus, the present invention constitutes an improvement of the invention described in the aforementioned international patent application WO 00/05295 A1, in that it proposes a method for controlling an apparatus for producing webs as described above. capable of improving the aesthetic quality as well as the mechanical properties of the webs produced, while making it possible to reduce the time and the cost of production of said webs. In fact, by producing successive layers from the widest to the narrowest, the counter-cylinder must only be replaced or subjected to maintenance at the end of the control process, that is to say at the end of the process for producing successive webs, which ends after the production of the narrowest web. Thus, the result is a saving in production time. Moreover, thanks to the control method of the present invention, it is avoided that a previous ply narrower than the ply following it directly in the production order does not leave marks on the outer surface of the counter-cylinder, as explained above, leading to a marking of the next sheet, wider than the previous one. This ordering process therefore makes it possible to avoid having to throw it away because of its unsightly nature or its altered properties, and thus to increase the efficiency of the production apparatus and to save money.

According to an exemplary embodiment, the step of extruding said successive layers comprises the insertion of at least one lateral element at at least one of the two lateral ends of the flat die in order to reduce the width of the successively extruded layers.

According to another exemplary embodiment, the step of extruding said successive plies comprises partially blocking the opening of the flat die at at least one of the two lateral ends of the flat die in order to reduce the width of the successive plies extruded.

According to a preferred embodiment, the method further comprises raising and holding the counter cylinder to allow its replacement.

According to a preferred embodiment, the method further comprises an adjustment of the speed of rotation of at least one of the drive cylinder and of the counter-cylinder by a motor connected to said cylinder during the step of pre -drawing said successive layers.

According to a preferred embodiment, the method further comprises cooling the drive cylinder by a first cooling device integrated into the drive cylinder during the step of producing said successive layers.

According to a preferred embodiment, the method further comprises cooling the backing roll by a second cooling device external to the backing roll during the step of producing said successive plies.

According to an exemplary embodiment, said cooling comprises bringing a lower part of the counter-cylinder into contact with a water reservoir.

According to an exemplary embodiment, the method further comprises a step of evacuating the cooling water from the outer surface of the counter-cylinder at the outlet of said second cooling device via an element in contact with the outer surface of the counter -cylinder. According to a preferred embodiment, the method further comprises adjusting the distance between the drive cylinder and the counter-cylinder during the step of producing said successive layers. According to a preferred embodiment, the method further comprises adjusting the distance between said cylinders and the slot die opening during the step of producing said successive plies.

According to a preferred embodiment, the method further comprises a step of cutting successive layers pre-stretched and cooled to widths determined by a series of cutting elements downstream of said cylinders.

BRIEF DESCRIPTION OF THE FIGURES These and other aspects of the present invention will now be described in greater detail, with reference to the accompanying drawing showing an exemplary embodiment of the invention.

Figure 1 schematically illustrates an apparatus for producing a web from a polyolefin matrix according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 schematically illustrates an apparatus for producing a web from a polyolefin matrix according to an exemplary embodiment of the invention.

Upstream of the apparatus illustrated in FIG. 1 there may be one or more containers 1 comprising the constituents which are dosed and mixed before being introduced into the apparatus. The mixture comprises said polyolefinic matrix and optionally at least one mineral and/or organic filler. The polyolefin matrix comprises at least one polymer. This or these containers are fed by one or more silos inside or outside the building housing the device illustrated in Figure 1.

The polyolefinic matrix may be formed from olefinic polymers and/or copolymers chosen from the group consisting of polyolefin plastomeric copolymers of ethylene and alpha-olefins, polyethylene homopolymers or copolymers of ethylene and alpha-olefins, ethylene copolymers -vinyl acetate, EVA, ethylene-methyl acrylate, EMA, ethylene-ethyl acrylate, EEA, ethylene-acrylic acid, EAA, and ionomers, homopolymer polypropylenes, metallocene polypropylenes, propylene-ethylene copolymers, propylene -alpha-olefin.

According to an exemplary embodiment, the polyolefinic matrix can be formed from polyethylene, PE, or from polypropylene, PP, or from a combination of the aforementioned polymers.

The international patent application WO 00/05295 A1 in the name of the applicant, the content of which is included by reference in the present application, describes in more detail such a polyolefinic matrix.

The optional mineral filler entering into the composition of the sheet can be chosen from the group consisting of calcium carbonate, tale, a clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate , magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide magnesium hydroxide, calcium oxide, magnesium oxide zinc oxide, titanium oxide , alumina, mica, powder or glass beads, a zeolite or others, and preferably calcium carbonate and barium sulphate, used alone or as a mixture.

The filler of organic origin entering into the composition of the web can be chosen from the group consisting of cellulose powders, polymer powders, such as polyurethane, epoxy, ABS, polyfluorines, polyamides, of polyesters or other polymers, used alone or as a mixture.

The mixture comprising the polyolefinic matrix and optionally the mineral and/or organic filler may also comprise active agents such as lubricants, pigments, dyes, heat stabilizers, photochemical stabilizers, flame retardants, plasticizers, antistatics, biocides.

International patent application WO 00/05295 A1 in the name of the applicant, the content of which is included by reference in the present application, describes in more detail such mineral and/or organic fillers.

In the context of the invention, the word "sheet" refers to a strip, or ribbon, composed of at least one layer and formed by extrusion, pre-stretching, cooling and at least partial solidification of the aforementioned mixture.

A web thus produced has specific dimensions, such as a given width and thickness, as well as specific mechanical and/or optical properties such as a given resistance to deformation, a given reflection of incident light or a given opacity, etc. .

A web thus produced also has specific physico/chemical properties, such as a given porosity or a hydrophobic character due to the use of polymers in the polyolefinic matrix.

Combined with other materials such as non-woven fabrics, the web can have additional characteristics. For example, when combined with a hydrophilic nonwoven fabric, by lamination among other things, the sheet, originally hydrophobic on both sides, can become hydrophilic on one of its sides.

The web can be intended for the manufacture of a microporous film permeable to gases and impermeable to aqueous liquids. More particularly, the web can be intended for the manufacture of a soft, flexible and breathable polyolefinic microporous film, formed of at least one layer, permeable to gases and water vapors but impermeable to aqueous liquids, of high mechanical characteristics and with a pleasant touch. Thus, the sheet is capable of being stretched subsequently with a view to reducing its thickness and modifying its mechanical and/or optical and/or physico-chemical characteristics, so as to produce a microporous film. The stretching of the sheet generates fractures and micro-channels between the mineral fillers distributed randomly in the sheet and the polymer matrix which constitutes the sheet. The entanglement of the micro-channels generates the microporous character of the film thus produced. International patent application WO 00/05295 A1 in the name of the applicant, the content of which is included by reference in the present application, describes such microporous films in more detail.

The sheet can also be intended for the manufacture of a non-microporous film, that is to say a film resistant to the penetration of gases and impermeable to aqueous liquids. Such a film can therefore be both impermeable to gases and water vapor and impermeable to aqueous liquids. It should be noted that such a film may not be completely impermeable to gases. Thus, although the non-microporous film is resistant to gas penetration, a small amount can still pass through the film. Such a film does not require subsequent stretching of the sheet, unlike a microporous film. Indeed, as described above, it is the stretching of the sheet which gives a microporous characteristic to the film, which is obviously not desirable in the case of a non-microporous film.

Whether for the production of webs intended for microporous or non-microporous films, the various constituents of the aforementioned mixture can be conveyed, for example by suction, into a mixing tower (not shown) upstream of the apparatus illustrated in Figure 1. These different constituents of the mixture can come from different containers, as shown above. A succession of dosers upstream of the device illustrated in Figure 1 can dose, for example gravimetrically, the various constituents of the mixture.

For the production of webs intended for microporous films, the mixture may comprise a high mass fraction of mineral fillers, such as calcium carbonate, CaCOs. Due to the presence of CaCO3, the mixture thus formed is hygroscopic. For this reason, the apparatus illustrated in FIG. 1 may comprise a means for drying the mixture (not represented) comprising the polyolefinic matrix and the CaCO:3 before production of a web from this mixture. Thus, the apparatus illustrated in Figure 1 can for example comprise a cylinder through which hot air passes so as to eliminate traces of water on the surface of the granules of the raw material. Indeed, without this drying, the residual moisture present within the mixture can create steam when the temperature of the mixture rises during the extrusion step described below. This vapor can create a series of holes in the extruded web, which alters its properties and therefore its quality. For the production of webs for non-microporous films, the drying step described above is not necessary. The mixture can comprise a low mass fraction of mineral fillers, such as for example titanium dioxide, TiO». The TiO2 pigment then gives the web thus produced an opacity and a white color. According to another embodiment, a non-microporous film may not include any filler, and therefore have a transparent or translucent property. The apparatus illustrated in Figure 1 comprises an extruder 2 and a flat die 3 associated with the extruder 2 and comprising an opening 3', intended for the extrusion of the sheet by pressure and hot casting of the mixture.

The extruder 2 can be configured to extrude the sheet at a temperature between, for example, 170° C. and 270° C., depending on the nature of the constituents of the mixture to be extruded. The flat die 3 can be provided with at least one lateral element (not shown) insertable at at least one of the two lateral ends of the flat die 3 and intended to reduce the operational width of the flat die 3 in order to reduce the width of the extruded web. Alternatively, the 3° opening of the flat die 3 can be configured to be partially blocked at at least one of the two lateral ends of the flat die 3, so as to reduce the operational width of the flat die 3 in order to reduce the width of the extruded web. The insertion e of a side element or the partial blocking of the opening 3' of the flat die 3 does not reduce the physical width of the flat die 3, but rather its - operational width. In other words, the working width of the flat die 3, which corresponds to an effective contact between the sheet to be extruded and the flat die 3, is reduced by the insertion of said side element in order to reduce the width of the sheet. extruded. Thanks to the aforementioned insertion or partial blocking, the extruder 2 and the flat die 3 can extrude webs having variable widths depending on whether or not these elements are present in the flat die 3. The insertion of an element lateral is preferably carried out from the two lateral ends of the flat die 3 symmetrically with respect to the central axis of the flat die 3. The temperature of the sheet is the result on the one hand of the extrusion itself, and on the other hand from the additional contribution of calories by differential heating of different zones, including the connecting tubes (not shown) of the extruder 2 to the flat die 3 as well as of the flat die 3 itself. This temperature and its control allow the water table to be poured under good conditions of efficiency and quality. The pressure generated mainly by the rotation of the extrusion screw (not shown) of the extruder 2 allows the molten mixture comprising the polyolefinic matrix, and optionally mineral fillers and additives, to leave the flat die 3 according to the fluidity obtained by the adequacy temperature-types of polymer and according to the width resulting from the flat die 3.

Extruder 2 and flat die 3 can be adapted to extrude a multilayer sheet. The thickness of the multilayer sheet at the outlet of the flat die 3 can be between 300 and 2000 μm. The extruder 2 may comprise a plurality of extrusion units, each intended to extrude a mixture corresponding to each of the layers of different compositions. The flat die 3 can be provided with a co-extrusion device intended to be fed by each of the extrusion units. For example, if an additive, such as a colorant, is added to the mixture, the co-extrusion can make it possible to obtain a two-layer sheet, the first layer of which can be white in color and the second layer can be blue in color. . This produces a sheet whose color varies from one side to the other. As described below, after the co-extrusion step, the two assembled layers of the two-layer sheet come into contact with a drive cylinder 5 associated with a counter-roller 4 for a step of pre-stretching the sheet. bilayer. The blue colored layer may be in contact with drive cylinder 5, while the white colored layer may be in contact with counter cylinder 4.

According to another embodiment, the extruder 2 and the flat die 3 can be adapted to the extrusion of a monolayer web. The thickness of the monolayer web at the outlet of the flat die 3 can also be between 300 and 2000 μm. International patent application WO 00/05295 A1 in the name of the applicant, the content of which is included by reference in the present application, describes in more detail such mono- or multi-layer webs.

The apparatus illustrated in Figure 1 further comprises a drive cylinder 5 comprising a metallic outer surface, and a counter-cylinder 4 associated with the drive cylinder 5 and comprising a rubberized outer surface, intended to pre-stretch the web extruded. At least one of drive cylinder 5 and counter cylinder 4 is replaceable.

The outer surface of drive cylinder 5 may be provided with a pattern selected from regular and irregular patterns, in relief, in hollow, intended to emboss the pre-stretched and cooled web.

The pattern is made according to shapes which are lines in the longitudinal direction, transverse, diagonal with respect to the direction of advancement of the tablecloth, parallel or intersecting to form geometric figures, more or less open chevrons, sinusoids , gears, polygonal or circular figures such as hexagons, rhombuses, or circles.

For example, the embossing of the pre-stretched web can be achieved by means of triangular or hexagonal patterns, thus allowing subsequent stretching along three axes corresponding to the three sides of the triangles or to the three pairs of opposite sides of the hexagons.

According to another example, the embossing of the pre-stretched sheet can be carried out by means of patterns in the shape of quadrilaterals, such as diamonds, rectangles or squares, thus allowing subsequent stretching along two axes corresponding to the two pairs of sides opposites of quadrilaterals.

Drive roll 5 and counter roll 4 can be configured to pre-stretch the extruded web in a ratio in the range 4 to 25, preferably between 5 and 10. Indeed, the extruded web can be relatively thick at the outlet of the flat die 3, of the order of a millimeter to a tenth of a millimeter for the thinnest layers.

Said cylinders 4, 5 make it possible to reduce the thickness of the pre-stretched sheet so as to obtain a pre-stretched sheet having a thickness of the order of a hundred microns, or even ten microns for the thinnest sheets. finer.

The device may further comprise a series of cylinders (not shown) downstream of the drive cylinder 5 and the counter-cylinder 4, intended to roll up the pre-stretched and cooled web with a view to storing it.

In this way, the web can be wound on a cardboard or other mandrel, and is thus ready to be delivered to customers.

The device may further comprise a series of cutting elements (not shown) downstream of the drive cylinder 5 and the counter-cylinder 4, intended to cut the pre-stretched and cooled web to a determined width.

In this way, a final check, and a final adjustment if necessary, of the width of the webs thus produced is possible, before delivery to the various customers.

In addition, on leaving the pre-stretching, the sheet has at its lateral ends a greater thickness than at its center due to the extrusion of the sheet through the flat die 3. This greater thickness is eliminated at the end of the sheet. using these cutting elements, before winding the web.

These cutting elements can be configured to cut a few centimeters at each side end of the sheet.

Preferably, said cut out thickness can be reintroduced into the production apparatus in order to reduce the volume of production waste and save money.

The apparatus illustrated in Figure 1 further comprises means for cooling at least one of the drive cylinder 5 and the counter-cylinder 4, so as to cool and at least partially solidify the pre-stretched web. . The cooling means may comprise a first cooling device (not shown) integrated into the drive cylinder 5 and intended to cool the drive cylinder 5. The drive cylinder 5 being made of metal, the heat transfer from the sheet to be cooled towards its metallic outer surface, in contact with the sheet to be cooled, takes place efficiently thanks to good thermal conduction. The cooling means may comprise a second cooling device (not shown) external to the counter-cylinder 4 and intended to cool the counter-cylinder 4. The second cooling device positioned outside the counter-cylinder 4 allows a better transfer of heat from its rubberized outer surface, in contact with the sheet to be cooled, towards the outside of the counter-cylinder 4, because the rubber-coated cylinder 4 does not enjoy optimum heat conduction. The second cooling device may comprise a water tank in contact with a lower part of the counter-cylinder 4. The apparatus may further comprise an element in contact with the outer surface of the counter-cylinder 4 and intended to evacuate the cooling water from the outer surface of the counter-cylinder 4 at the outlet of the second cooling device.

The contact time of the sheet with the drive cylinder 5 can be regulated by an additional counter-cylinder 6 which, depending on its position, increases or decreases the length of the embracing arc of the drive cylinder 5 by the tablecloth. The tangential output of the sheet can be controlled by counter-cylinder 6.

When the sheet is intended for the production of a microporous film, the sheet to be stretched can, optionally as indicated in FIG. rollers 7, 8, placed downstream of the drive cylinder 5 and which constitutes the tangential stretching torque of a first stage of partial stretching, by applying a desired stretching rate to it. Thus, the sheet can be stretched to form a microporous film, between the drive cylinder 5 and the pair of rollers 7, 8. According to one embodiment, the cylindrical surface of at least one of the rollers 7, 8 can also be provided with patterns, as previously mentioned, to allow embossing of the film. According to another embodiment, the cylindrical surface of at least one of the rollers 7, 8 is not provided with telmotifs, and is therefore smooth.

Since the sheet resulting from the pre-stretching operation does not typically have the characteristics desired for a microporous film such as, in particular, a low thickness, a microporosity giving it the ability to breathe while being impermeable to aqueous liquids, or mechanical properties necessary for its subsequent use, it can be subjected, after having been heated to the appropriate temperature, by calendering for example, to a drawing operation. This operation can be carried out between at least two pairs of rollers 5, 6 and 7.8, forming a drawing bed, rotating at different speeds. A first pair of rollers 5, 6 constitutes the call pair which simultaneously plays the role of delivering the web to be stretched and possibly of helping to maintain the delivered web at the desired temperature for stretching. A second pair of rollers 7, 8 constitutes the actual stretching pair of the web by applying the desired stretching rate to it, this rate being given by the ratio of the linear speeds delivered by the pair of stretching rolls 7, 8 and the pair of take-up rollers 5, 6. One or more pairs of subsequent rollers (not shown), downstream of the second pair of rollers 7, 8, can complete the stretching of the web by applying the same rate to it. stretch or other desired stretch ratios.

Thus, a succession of stretching steps alternating with heating and cooling steps, or called annealing steps, at the same temperature or at different desired temperatures, can be applied to the web with a view to obtaining a film microporous. Beyond the successive stretching(s), depending on the production process used, the microporous film can undergo an annealing heat treatment in order to control its shrinkage or even improve its dimensional stability at temperature.

The subsequent stretching of the sheet can be carried out directly after the pre-stretching, cooling and at least partial solidification stages, by a stretching bench such as the bench 7, 8 located downstream of the apparatus according to the invention. . Alternatively, the subsequent stretching of the web can be carried out by a device other than the device according to the invention, for example by a device belonging to a customer. The customer can therefore apply the desired specific stretching to said pre-stretched, cooled and at least partially solidified webs, according to his objectives, his applications, and his own requirements.

To obtain a microporous film by stretching a sheet, the pre-stretched sheet can undergo substantial and practically complete cooling in contact with the drive roll 5 and the counter-cylinder 4. The temperature of the sheet can reach from 20 to 30° C., for example 25° C., after practically complete cooling of the sheet. This sheet is therefore subsequently reheated to a temperature which is sufficient and depends on the nature of the polyolefinic matrix to be able to be correctly stretched in the appropriate stretching zone and transformed into a film having the expected characteristics. This may typically be the case if the subsequent stretching is carried out by an apparatus other than the apparatus according to the invention, such as an apparatus belonging to a customer. Alternatively, the cooling of the pre-stretched sheet by the drive cylinder 5 and the counter-cylinder 4 can be partial and limited in a controlled manner to a temperature lying within the range of temperatures necessary for its stretching. , for example at a temperature between 80 and 90°C. This technique makes it possible to prevent the constituent material of the sheet, which is initially in a quasi-isotropic state before pre-stretching, cooling and practically complete solidification, from undergoing internal physical modifications during these stages, in particular macromolecular deformations and /or a macromolecular orientation and/or an evolution of the crystallinity, which are fixed in the state, during the cooling. This can typically be the case if the subsequent drawing is carried out directly by a drawing bench such as the bench 7, 8 located downstream of the device according to the invention. For example, the stretching of the sheet brought to the necessary temperature by the partial cooling can be carried out by traction, at the moment when its tangential separation from the drive roll 5 occurs, the drive roll 5 playing the role of take-up roll for stretching. International patent application WO 00/05295 A1 in the name of the applicant, the content of which is included by reference in the present application, describes in more detail such stretching of the web.

The device illustrated in Figure 1 further comprises a means of adjustment (not shown) of at least one of the following quantities: speed and temperature of at least one of the drive cylinder 5 and the counter- cylinder 4, distance between drive cylinder 5 and counter cylinder 4, distance between said cylinders 4, 5,6, 7 and 8 and opening 3' of flat die 3, width of flat die 3.

— Adjusting the speed of at least one of drive roll 5 and counter roll 4 controls the thickness of the pre-stretched web, and adjusting the temperature of at least one of the drive cylinder 5 and of the counter-cylinder 4 makes it possible to control the cooling and at least partial solidification of the pre-stretched web. However, the thickness and the cooling of the pre-stretched web influence the mechanical and/or physico-chemical characteristics of the web thus produced. Furthermore, the adjustment of the distance between said cylinders 4, 5 allows the control of the thickness of the web thus produced, and the adjustment of the distance between said cylinders 4, 5 and the opening 3 'of the flat die 3 allows downstream control of the width of the web thus produced. Indeed, at the exit of the 3° opening of the flat die 3, the width of the extruded web tends to decrease. This decrease in width is specific to the molecular structure of the polymers used in the polyolefin matrix, and can be higher or lower from one polymer to another. It is therefore possible to control the distance between the said cylinders 4, 5 and the opening 3′ of the flat die 3 in order thus to control the width of the ply during the contact of the ply with the said cylinders 4, 5. Finally, the adjustment of the width of the flat die 3 as described above allows the upstream control of the initial width of the sheet to be extruded, before contact with the said cylinders 4, 5. The apparatus may further comprise a motor (not shown) connected to at least one of the drive cylinder 5 and the counter-cylinder 4 and intended to adjust the speed of rotation of the cylinder. The motor may include a gearbox, which allows precise control of the thickness of the web thus produced.

Thus, the apparatus illustrated in Figure 1 produces a web from a polyolefin matrix by a method comprising the successive steps of preparing a mixture comprising said polyolefin matrix and optionally at least one mineral and/or organic filler, the extrusion of the sheet by pressure and hot casting of the mixture by an extruder 2 associated with a flat die 3 comprising an opening 3', the selection of a drive cylinder 5 comprising a metallic outer surface from among a set of cylinders drive cylinder, and a backing roll 4 associated with the driving roll 5 and comprising a rubberized outer surface among a set of backing rolls, based on a predetermined set of rules, the pre-stretching of the web extruded by the drive cylinder 5 and the counter-cylinder 4, the cooling and at least partial solidification of the pre-stretched web, by means of at least one of the drive cylinder 5 and u counter cylinder 4.

The predetermined set of rules may include comparing the width of said web to the width of a web produced directly before said web by said process. Thus, the aforementioned selection is based on a width comparison between two webs successively produced by the production process. If the width of the previous ply is greater than that of the current ply to be produced, it may be decided for the production of the current ply to select the cylinders 4, 5 used for the production of the previous ply. In particular, in this case it can be decided to keep the same counter-cylinder 4 for the production of the current layer. As for the drive cylinder 5, it can also be decided to select a cylinder having an outer surface provided with other patterns than those used for the production of the previous sheet, on the basis of another predetermined set of rules such as subsequent stretching along different axes, for example biaxial.

On the other hand, if the width of the previous ply is less than that of the current ply to be produced, it can be decided for the production of the current ply to select cylinders other than those 4, 5 used for the production of the ply. former. In particular, in this case it may be decided to replace the counter-cylinder 4 for the production of the current layer, or to ensure its maintenance before producing the current layer. Indeed, in this case the previous ply will have, at its lateral ends, a greater thickness than at its center due to the extrusion of the ply through the flat die 3. This greater thickness at the lateral ends of the extruded ply will have left marks on the rubber of the outer surface of the counter-cylinder 4. During the production of the current ply, having a width greater than that of the previous ply, the portion of the outer surface of the counter-cylinder 4 which will have been marked by the production of the previous sheet will be in contact with the current sheet, which will leave marks on the current sheet, making the sheet thus produced unsightly and not suitable for sale. In addition, this marking of the current web can alter its properties and therefore its quality.

Thus, in the second case, the counter-cylinder 4 can either be replaced by a new counter-cylinder or at least one that does not show any marks on its outer rubber surface, or remove a thin outer film of rubber from the outer surface of the cylinder against 4, called rectification of the outer surface of the cylinder against 4, for example by abrasion, then to reposition the cylinder against 4 at a good relative distance from the drive cylinder. Indeed, as the thickness of the counter-cylinder 4 varies after removal of said thin outer film, the distance between the two cylinders 4, 5 also varies, as well as the tangential speed of the counter-cylinder 4 due to the variation of its Ray. Thanks to the adjustment of at least one of the aforementioned quantities by means of the production process, a control of the speed of the counter-cylinder 4 and/or of the drive cylinder 5 and/or a control of the distance between said cylinders 4, 5 can be performed to ensure that the actual web will be produced by the process to parameters that meet customer requirements.

Preferably, the rectification of the outer surface of the counter-cylinder 4, to the dimensions of adequate roughness and flatness, is carried out using a machine (not shown), such as a lathe, installed in the building. housing the production device, close to this device. Thus, it is not necessary to subcontract the grinding of the outer surface of counter-cylinder 4, which saves time and money while controlling quality.

As described above with respect to the web producing apparatus, the production process further comprises adjusting at least one of the following quantities during the pre-stretching, cooling and solidification steps: speed and temperature of at least one of drive cylinder 5 and counter-cylinder 4, distance between drive cylinder 5 and counter-cylinder 4, distance between said cylinders 4, 5 and opening 3' of flat die 3, width of flat die 3.

The apparatus illustrated in Figure 1 is controlled by a control method comprising the successive steps of the preparation of several mixtures each comprising a polyolefinic matrix comprising at least one polymer, and optionally at least one mineral and/or organic filler, the production , comprising the extrusion, the pre-stretching, the cooling and the at least partial solidification, of several successive sheets corresponding to the several mixtures according to the aforementioned production process.

Said successive webs consist of at least one layer and have a decreasing width from a given web produced by said process to a web produced directly after said web.

The control method of the apparatus may comprise the insertion of at least one side element at at least one of the two lateral ends of the flat die 3, or the partial blocking of the 3° opening of the flat die 3 at at least one of the two lateral ends of the flat die 3 in order to reduce the width of the layers successively extruded.

The device control method illustrated in Figure 1 further comprises the replacement of the counter-cylinder 4 after the production of the narrowest layer among said successive layers produced by said method, and before restarting the control method of the device.

The method of controlling the device therefore makes it possible to produce a succession of layers having a decreasing width, and to replace the counter-cylinder 4 after the production of the narrowest layer before starting the method of controlling the device again.

Thus, the control method of the device is able to improve the aesthetic quality as well as the mechanical properties of the sheets produced, while making it possible to reduce the time and the cost of production of said sheets.

Indeed, by producing successive layers from the widest to the narrowest, the counter-cylinder 4 must only be replaced or subjected to maintenance at the end of the control process, that is to say at the end of the process for producing successive layers, which ends after the production of the narrowest layer.

Thus, the result is a saving in production time.

In addition, thanks to the control method of the device, it is avoided that a preceding sheet narrower than the sheet following it directly in the production order does not leave marks on the outer surface of the counter-cylinder 4, such as explained above, leading to a marking of the next sheet, wider than the previous one.

This ordering process therefore makes it possible to avoid having to throw it away because of its unsightly nature or its altered properties, and thus to increase the efficiency of the production apparatus and to save money.

As indicated above, at least one of the drive cylinder 5 and counter cylinder 4 of the device shown in Figure 1 is replaceable. The device illustrated in Figure 1 further comprises a lifting means and a holding means (not shown) of the replaceable cylinder 4; 5 connected to replaceable cylinder 4; 5 and configured to allow replacement of cylinder 4; 5. In particular, the control method of the device may include the elevation and detention of the counter-cylinder 4 to allow its replacement or maintenance. The counter-cylinder 4 having substantial dimensions as well as a substantial weight, such a means of elevation and such a means of holding the counter-cylinder 4 allows an easy and robust mechanized replacement of the counter-cylinder 4. Typically, the counter-cylinder cylinder 4 is extracted from the pre-stretch bench which it forms with drive cylinder 5, is lifted by the lifting means, is held in the air by the holding means while awaiting replacement or maintenance, then is either placed on the ground if it is replaced, or placed back in position in the pre-stretch bench after maintenance. It should be noted that the two aforementioned cylinders 4, 5 can be replaced, simultaneously or one after the other, and this by the same lifting and holding means.

Although the principles of the invention have been set forth above in connection with specific embodiments, it should be understood that this description is made merely by way of example and does not constitute a limitation of the scope of the invention. protection which is determined by the claims appended below.

Claims (39)

1. Apparatus for producing a web from a polyolefinic matrix comprising at least one polymer, said web consisting of at least one layer, said apparatus comprising: - an extruder (2) and a flat die (3 ) associated with the extruder (2) and comprising an opening (3'), intended for the extrusion of the sheet by pressure and hot casting of a mixture comprising the said polyolefinic matrix and optionally at least one mineral filler and/or organic ; - a drive cylinder (5) comprising a metallic outer surface, and a counter-cylinder (4) associated with the drive cylinder (5) and comprising a rubberized outer surface, intended to pre-stretch the extruded sheet; - a means of cooling at least one of the drive cylinder (5) and the counter-cylinder (4), so as to cool and at least partially solidify the pre-stretched web; and - means for adjusting at least one of the following quantities: speed and temperature of at least one of the drive cylinder (5) and of the counter-cylinder (4), distance between the drive (5) and the counter-cylinder (4), distance between said cylinders (4, 5) and the opening (3') of the flat die (3), width of the flat die (3); wherein at least one of the drive cylinder (5) and counter cylinder (4) is replaceable; characterized in that the apparatus further comprises elevating means and replaceable cylinder holding means (4; 5) connected to the replaceable cylinder and configured to allow replacement of the cylinder. 2. Apparatus according to claim 1, wherein the apparatus is configured to produce a web intended for the manufacture of at least one of the following two types of films: a microporous film permeable to gases and impermeable to aqueous liquids, and a non-microporous film resistant to gas penetration and impermeable to aqueous liquids. 3. Apparatus according to any preceding claim, wherein the cooling means comprises a first cooling device integrated in the drive cylinder (5) and intended to cool the drive cylinder (5). 4. Apparatus according to any preceding claim, wherein the cooling means comprises a second cooling device external to the counter-cylinder (4) and intended to cool the counter-cylinder (4). 5. Apparatus according to claim 4, wherein said second cooling device comprises a water reservoir in contact with a lower part of the counter cylinder (4). 6. Apparatus according to claim 5, further comprising an element in contact with the outer surface of the counter-cylinder (4) and intended to evacuate the cooling water from the outer surface of the counter-cylinder (4) at the outlet of the second cooling device. 7. Apparatus according to any one of the preceding claims, in which the flat die (3) is provided with at least one lateral element insertable at at least one of the two lateral ends of the flat die (3) and intended to reduce the flat die operating width (3); or wherein the opening (3') of the slot die (3) is configured to be partially blocked at at least one of the two side ends of the slot die (3) to reduce the operational width of the slot die (3 ). 8. Apparatus according to any preceding claim, further comprising a motor connected to at least one of the drive cylinder (5) and counter cylinder (4) and for adjusting the rotational speed of the cylinder . 9. Apparatus according to any one of the preceding claims, wherein the outer surface of the drive cylinder (5) is provided with a pattern selected from regular and irregular patterns, in relief, in relief, intended to emboss the web pre-stretched and cooled. 10. Apparatus according to any preceding claim, wherein the extruder (2) is configured to extrude the web at a temperature between 170°C and 270°C. 11. Apparatus according to any preceding claim, wherein the drive roll (5) and counter roll (4) are configured to pre-stretch the extruded web at a ratio in the range 4 to 25 , preferably between 5 and 10. 12. Apparatus according to any preceding claim, further comprising a series of rolls downstream of the drive roll (5) and backing roll (4), for rolling up the pre-stretched and cooled web for to store it. 13. Apparatus according to any one of the preceding claims, further comprising a series of cutting elements downstream of the drive cylinder (5) and the counter-cylinder (4), intended to cut the pre-stretched and cooled web. at a certain width. 14. Apparatus according to any one of the preceding claims, in which the extruder (2) and the flat die (3) are suitable for the extrusion of a multilayer sheet, in which the thickness of the multilayer sheet at the outlet of the flat die (3) is between 300 and 2000 μm. 15. Apparatus according to claim 14, in which the extruder (2) comprises a plurality of extrusion units, each intended to extrude a mixture corresponding to each of the layers of different compositions, in which the flat die (3) is provided with a co-extrusion device intended to be supplied by each of the extrusion units. 16. Apparatus according to any preceding claim, wherein the polyolefin matrix is formed of polyethylene, PE, or polypropylene, PP, or a combination of the aforementioned polymers. 17. Process for producing a web from a polyolefinic matrix comprising at least one polymer, said web consisting of at least one layer, said process comprising the successive steps of: - preparing a mixture comprising said polyolefinic matrix and optionally at least one mineral and/or organic filler; - the extrusion of the sheet by pressure and hot casting of the mixture by an extruder (2) associated with a flat die (3) comprising an opening (3°): - the selection of a drive cylinder (5) comprising a metallic outer surface among a set of drive cylinders, and a counter-cylinder (4) associated with the drive cylinder (5) and comprising a rubberized outer surface among a set of counter-cylinders, on the basis of a predetermined set of rules; - the pre-stretching of the extruded web by the drive cylinder (5) and the counter-cylinder (9): - the cooling and at least partial solidification of the pre-stretched web, by means of at least l one of the drive cylinder (5) and the counter cylinder (4); wherein the method further comprises adjusting at least one of the following quantities during the pre-stretching, cooling and solidification steps: speed and temperature of at least one of the driving cylinder (5) and of the counter-cylinder (4), distance between the driving cylinder (5) and the counter-cylinder (4), distance between said cylinders (4, 5) and the opening (3') of the slot die (3), width of the slot die (3): characterized in that the method further comprises raising and holding at least one of the drive cylinder (5) and the counter-cylinder (4) to allow its replacement. 18. Process according to claim 17, in which the web thus produced is intended for the manufacture of at least one of the following two types of film: a microporous film permeable to gases and impermeable to aqueous liquids, and a non-microporous film resistant to gas penetration and impermeable to aqueous liquids. 19. A method according to claims 17 or 18, wherein the predetermined set of rules comprises comparing the width of said web to the width of a web produced directly before said web by said process. 20. A method according to any one of claims 17-19, wherein the extruding step comprises inserting at least one side member at at least one of the two side ends of the flat die (3) or partial blocking of the opening (3°) of the slot die (3) at at least one of the two lateral ends of the slot die (3). 21. Method according to any one of claims 17-20, further comprising a step of embossing the pre-stretched and cooled sheet with a regular or irregular pattern, in relief or in relief, on the outer surface of the cylinder of drive (5). 22. Process according to any one of claims 17-21, in which the temperature of the web at the exit from the extrusion step is between 170°C and 270°C. 23. A method according to any of claims 17-22, wherein the extruded web is pre-stretched at a ratio in the range 4 to 25, preferably between 5 and 10. 24. Method according to any one of claims 17-23, further comprising a step of rolling up the pre-stretched and cooled sheet by a series of cylinders downstream of said cylinders (4, 5) with a view to storing it. 25. Method according to any one of claims 17-24, further comprising a step of cutting the pre-stretched and cooled web to a width determined by a series of cutting elements downstream of said cylinders (4, 5). 26. Process according to any one of claims 17-25, in which the extrusion step corresponds to an extrusion by casting of a molten multilayer sheet, in which the thickness of the multilayer sheet at the outlet of the flat die (3) is between 300 and 2000 µm. 27. Method according to claim 26, in which a mixture corresponding to each of the layers of different composition of the multilayer web is extruded by an extrusion unit of the extruder (2) comprising a plurality of extrusion units, in wherein the step of extruding each of said mixtures is followed by a step of co-extrusion of the multilayer web. 28. Process according to any one of claims 17-27, in which the polyolefinic matrix is formed of polyethylene, PE, or of polypropylene, PP, or of a combination of the aforementioned polymers. 29. Method for controlling the device according to any one of claims 1-16, comprising the successive steps of: - the preparation of several mixtures each comprising a polyolefinic matrix comprising at least one polymer, and optionally at least one mineral filler and/or organic; - the production, comprising the extrusion, the pre-stretching, the cooling and the at least partial solidification, of several successive layers corresponding to the several mixtures according to the process according to any one of claims 17-28, the said successive layers consisting of at least one layer and having a decreasing width from a given web produced by said process to a web produced directly after said web; characterized in that the method further comprises the replacement of the counter-cylinder (4) after the production of the narrowest layer among the said successive layers produced by the said method, and before restarting the method of controlling the apparatus. 30. Method according to claim 29, in which the step of extruding said successive layers comprises the insertion of at least one lateral element at least one of the two lateral ends of the slot die (3) or the partial blocking of 'opening (3) of the flat die (3) at at least one of the two lateral ends of the flat die (3), in order to reduce the width of the layers successively extruded. 31. A method according to claims 29 or 30, further comprising raising and holding the backing cylinder (4) to allow its replacement. 32. A method according to any one of claims 29-31, further comprising adjusting the rotational speed of at least one of the drive cylinder (5) and the counter cylinder (4) by a motor. connected to said cylinder during the step of pre-stretching said successive plies. 33. A method according to any one of claims 29-32, further comprising cooling the drive cylinder (5) by a first cooling device integrated into the drive cylinder (5) during the production step. of said successive layers. 34. Method according to any one of claims 29-33, further comprising cooling the counter-cylinder (4) by a second cooling device external to the counter-cylinder (4) during the step of producing said webs successive. 35. Method according to claim 34, in which said cooling comprises bringing a lower part of the counter-cylinder (4) into contact with a reservoir of water. 36. Method according to claim 35, further comprising a step of discharging the cooling water from the outer surface of the counter-cylinder (4) at the outlet of the said second cooling device via an element in contact with the outer surface of the counter-cylinder (4). 37. A method according to any one of claims 29-36, further comprising adjusting the distance between the drive roll (5) and the backing roll (4) during the step of producing said successive layers . 38. A method according to any one of claims 29-37, further comprising adjusting the distance between said cylinders (4, 5) and the opening (3°) of the flat die (3) during the production step of said successive layers. 39. A method according to any one of claims 29-38, further comprising a step of cutting successive layers pre-stretched and cooled to widths determined by a series of cutting elements downstream of said cylinders (4, 5).