Method and machine for manufacturing an object having a fibrous matrix

Abstract

The invention relates to a method for manufacturing an object having a fibrous matrix which consists of depositing, on a receiving surface (4') of a mounting (4), at least one fibrous paste including at least fibres and a transport liquid, and removing at least one portion of the transport liquid, characterised in that: the mounting is at least partially porous; the receiving surface is at least partially formed by a material including an open-cell foam and / or an open-cell material obtained at least partially by agglomerating particles; and the receiving surface is adapted or configured such that the transport liquid does not naturally percolate through the mounting without being biased from the outside and such that the transport liquid percolates into the mounting when a sufficient controlled bias is applied to all or part of the paste / mounting system. The invention also relates to a machine for manufacturing an object having a fibrous matrix.

Description

[0001] The present invention relates to the technical field of manufacturing fibrous matrix objects by liquid means. In a preferred but not exclusive application, the invention relates to the manufacturing of fibrous matrix objects comprising in particular cellulose fibers.

[0002] For the purposes of the invention, the term "fibrous matrix object" should be understood to mean any object containing fibers which at least partially ensure the cohesion of said object. As an example of an object comprising a cellulose fiber matrix, it is possible to cite a sheet of paper, a sheet of cardboard, a papier-mâché or molded paper / cardboard object such as, for example, object packing elements for packaging or egg boxes, filters, without this list being either exhaustive or limiting. Furthermore, it should be noted that the invention is not limited to the manufacture of an object whose fibrous matrix is ​​mainly formed of cellulose fibers, the preceding and following examples being given because of their common and widespread nature.

[0003] A sheet of paper is generally formed by continuously depositing paper pulp on a support formed by an endless hydrophilic fabric through which some of the water in the paper pulp diffuses or flows naturally, the removal of water being accelerated by suction prior to pressing and then heating so as to remove most of the water while maintaining a dryness greater than 90%.

[0004] Paper mache or molded paper / cardboard objects are formed by depositing a cellulose fiber-based paste in a wire mold. This deposition is then followed by the removal of water by suction, pressing, and heating to obtain shells. In this context, an international application WO2009 / 034344 described the implementation of a mold made from the agglomeration of particles made of various materials such as glass, plastic, pure metal, or metal alloys.

[0005] These techniques allow the manufacture of fibrous matrix objects but do not allow optimal control of the shapes obtained or of the texture or even the distribution of the fibers in the fibrous matrix object.

[0006] The need therefore arose for a process that would allow optimal control of the distribution of fibers in the manufactured object.

[0007] In order to achieve this objective, the invention relates to a method for manufacturing a fibrous matrix object according to claim 1.

[0008] The implementation of such a support whose receiving face has a wettability with the transport liquid such that the contact angle of a drop of the transport liquid with the receiving face is greater than or equal to 100° allows optimal control of the distribution of the fibers to the extent that as long as the controlled stress is not applied the transport liquid does not percolate in the support and the concentration of transport liquid of the paste deposited on the receiving face does not vary. In addition, the low wettability of the porous material constituting the receiving face with respect to the transport liquid allows very high deposition precision to the extent that when depositing a drop or small quantities of paste on the receiving face this low wettability prevents spreading of the deposit so that it is perfectly controlled.Furthermore, the low or very low wettability induces an almost binary behavior of the support. Indeed, as long as no stress is applied, the transport liquid does not percolate in the support whereas when a stress is applied once the transport liquid has crossed the support the energy necessary to maintain the percolation of the transport liquid decreases due to the capillarity phenomena favored by the low wettability of the material constituting the support. In other words, apart from any stress greater than a given threshold the porous material constituting the receiving face is impermeable to the transport liquid, whereas when the stress exceeds this threshold the percolation begins and the material is no longer impermeable to the transport liquid as long as a stress is maintained.

[0009] It should also be emphasized that the low wettability of the porous material facilitates the detachment or demolding without fluffing of the manufactured fibrous matrix object. In addition, the low wettability or even very low wettability on the surface and internally of the porous material constituting the receiving face makes it possible to avoid clogging of this material, particularly when the pores are very small.

[0010] The isotropic or substantially isotropic nature of the material constituting the receiving surface allows good control of percolation at the receiving face as well as in the core of the material. In addition, this isotropic or substantially isotropic nature allows shaping of the receiving face by machining by ablation of material while taking care not to close the pores at the machined surfaces so that the machined material retains its porosity and wettability characteristics on the surface and in the mass of the porous material.

[0011] The invention also relates to a machine for manufacturing a fibrous matrix object according to claim 7.

[0012] For the purposes of the invention, the wettability characteristics of the porous material constituting the support are present at the receiving surface but also at the heart of the porous material.

[0013] For the purposes of the invention, the term percolation designates the physical phenomenon characterized in that below a stress threshold the transport liquid does not penetrate into the support and remains on the surface of the latter while beyond this stress threshold the transport liquid penetrates and passes through the support.

[0014] For the purposes of the invention, the term paste designates any mixture regardless of the respective proportions of transport liquid, fibers intended to form the fibrous matrix and possible chemical or other adjuvants, additives and / or solid fillers. Preferably, the paste comprises sufficient transport liquid to be malleable and, preferably, more than 30% by mass of transport liquid. For the purposes of the invention, the term paste also encompasses a mixture comprising transport liquid and fibers, which has a fluid behavior as is, for example, the case when the paste comprises more than 90% by mass of transport liquid.

[0015] For the purposes of the invention, the term fibrous matrix object encompasses all kinds of objects such as, for example, thin objects such as a sheet of paper or cardboard, thick objects such as plates, volume objects with dimensions greater than one millimeter in all three directions, these objects being able to be hollow or solid, without this list being either limiting or exhaustive.

[0016] In the context of the invention, the term deposition must be understood in the broad sense and includes in particular deposition by projection, deposition by dipping, deposition by flow, injection into a mold or any other technique making it possible to apply, place or deposit the paste on the receiving face and / or on a thickness of paste and / or fibrous matrix previously deposited.

[0017] For the purposes of the invention, the support may be in different forms and may, for example, be a plate, a hollow (female) mold whose internal wall forms at least part of the receiving face, a (male) mold whose external wall forms at least part of the receiving face, or even the combination of a hollow mold with a core.

[0018] According to the invention, the material constituting the support face may be a material consisting of an open-cell foam, a synthetic or natural cellular material with open cells or open cells, or a porous material with open cells. In the context of an open-cell cellular material or an open-cell foam, a characteristic quantity is the size or the largest dimension of the open cells or open cells. For the purposes of the invention, a cellular material or a foam may be described as a solid matrix or a solid network delimiting open cells or cells, while a porous material resulting from the agglomeration of particles may be described as a solid matrix defining a network of channels. Thus, a porous material obtained by agglomeration of particles may be seen as the negative or the complementary form of a cellular material or an open-cell foam.It should be noted that a porous material can be formed by the agglomeration of particles of different shapes such as grains, in which case we speak of powder, fibers or filaments. In the case of a porous material, a characteristic quantity is the size or the largest dimension of the pores. In the context of the invention, the dimensional characteristics given for the size of the cells apply to the size of the pores and vice versa.

[0019] In the context of the invention, the materials constituting the receiving face are configured so as to define continuous percolation paths for the transport liquid from the receiving face to a liquid discharge face generally but not necessarily located opposite the receiving face. The material constituting the receiving face and the corresponding part of the support then has low or even very low wettability along the entire percolation paths.

[0020] According to a characteristic of the invention, the receiving face has pores whose size is adapted or configured so that at least 50% and, preferably, at least 90% of the fibers of the pulp are retained. Such a characteristic of the invention aims to guarantee good efficiency of the process. The use of a porous, hydrophobic material allows high retention with very small pores while presenting a very low risk of clogging.

[0021] According to one embodiment of the invention, the pores of the receiving face have an average dimension less than or equal to 250 µm and, preferably less than or equal to 150 µm. According to a characteristic of the invention, the receiving face has an opening factor greater than or equal to 30%.

[0022] it should be noted that the choice, according to the invention, of the material constituting the receiving face of the support so that the transport liquid partially wets the receiving face so that the contact angle of a drop of the transport liquid with the receiving face is greater than or equal to 100°, makes it possible to best control the deposition of the paste on the support, in particular when the paste is deposited in a point manner or in such a way as not to cover the entire receiving face. In the case of use as a transport liquid of a water-based liquid, the receiving face according to this characteristic can be described as hydrophobic.

[0023] According to a variant of the invention, the material constituting the receiving face of the support is superhydrophobic. By superhydrophobic, it is meant that a drop of water deposited on the receiving face has with the latter a contact angle greater than or equal to 150°. By extension, in the context of the present invention the adjective superhydrophobic also applies to the case where the transport liquid is not water, in this case it means that a drop of transport liquid deposited on the surface of a superhydrophobic material has with the latter a contact angle greater than or equal to 150°. The same applies to the term hydrophobic which means in the context of the present that a drop of transport liquid deposited on the surface of a hydrophobic material has with the latter a contact angle greater than or equal to 100°.

[0024] According to another characteristic of the invention, the support comprises a material obtained by sintering particles of materials chosen from: metals, glasses, plastics, ceramics, mixtures of these.

[0025] The use of such a material obtained by sintering, in particular, to constitute the receiving face makes it possible to obtain an isotropic pore size and distribution favorable to the control of the manufacture of the fibrous matrix object. In addition, manufacturing by sintering makes it possible to produce shaped parts of large dimensions which have over the majority of their thickness the characteristics of porosity and pore distribution favorable to the control of percolation. The material obtained by agglomeration of particles can be described as an open-cell material insofar as its pores are sufficiently interconnected to allow the transport liquid to percolate therein or to pass through it under the effect of stress. The same definition applies to open-cell foams. In this case, it is also possible to speak of a sponge.The particles used to form the porous material can also receive a surface treatment prior to their agglomeration, such as a suitable coating which gives them the desired wettability characteristics and promotes their agglomeration.

[0026] For the purposes of the invention, sintering is understood to mean any process which makes it possible to obtain a stable agglomeration of particles and, for example, involves a combination of pressure and heat or involves the application of pressure to particles to form an agglomerate which is then heated without the application of pressure. In the context of the invention, the term sintering also covers laser sintering.

[0027] According to a variant of this characteristic, the material constituting the support comprises polyolefin particles, preferably polyethylene and / or polypropylene. The use of polyolefin makes it possible to obtain, at low cost, a suitable material which can easily be shaped to present a pattern or constitute a mold by machining and / or molding. It is also possible to use PTFE particles.

[0028] According to yet another variant of this characteristic, the support has a composite structure comprising at least one layer obtained by sintering particles which forms the receiving face and which is carried by at least one woven matrix. This embodiment variant allows, in particular, continuous manufacture of an object, the support being able to form an endless loop in the manner of a paper machine draining cloth. It should be noted that the weave, the diameter of the threads and the degree of opening of the woven matrix are then chosen so as not to affect the isotropic or substantially isotropic character of the porous material constituting the receiving face.

[0029] According to a feature of the invention, the receiving face has at least one pattern or shape whose smallest dimension is greater than or equal to the smallest average dimension of the fibers. By pattern or shape is meant any three-dimensional structure intended to conform, leave an imprint or influence the formation of the fibrous matrix object obtained by implementing the method according to the invention. The pattern or shape may have small and / or large dimensions. By smallest average dimension of the fibers is meant the average diameter or the average thickness of the fibers of the paste.

[0030] According to a variant of this characteristic, the pattern or shape of the receiving face is obtained by molding and / or machining of the support and / or 3D printing. The shape of the receiving face can thus be obtained by additive machining (by adding material) and / or by subtractive machining (by removing material) in particular.

[0031] According to a characteristic of the invention, the support comprises at least one movable element whose movement allows a modification of the conformation of the receiving face. The implementation of such a movable element allows a modification of the configuration of the receiving face before depositing the fibrous paste or after use and removal of the fibrous paste deposited in the context of this use. It is then possible to speak of a support with a reconfigurable receiving face. All or part of the receiving surface can then be reconfigurable.

[0032] According to a variant of this characteristic, the support comprises: at least one element which is movable relative to the receiving face in a direction normal to the latter and one end of which forms a part of the receiving face and is made of a porous material adapted or configured so that the transport liquid does not percolate naturally through the movable element without external stress and so that the transport liquid percolates into the support when a sufficient controlled stress is applied to all or part of the paste / support system, means for positioning the movable element configured to allow a reversible modification of the position of the movable element and a holding in position of the element during the depositing of the fibrous paste.

[0033] It should be understood that the moving elements are made of a porous material of the same nature or having the same characteristics as the material constituting the rest of the receiving face.

[0034] In the context of this variant, the support may comprise several juxtaposed and / or non-juxtaposed mobile elements which make it possible to define patterns according to their relative positions and in particular their extension in relation to the average level or the average altitude of the receiving face. Such patterns may, for example, be patterns identifiable or readable by the human visual system or readable by an automated or electronic reading system.

[0035] Still within the framework of this variant, the upper or free face of each mobile element can be flat or have a concave and / or convex conformation or even bear its own pattern.

[0036] In the context of this variant again and according to a characteristic of the invention, the receiving surface comprises at least one zone comprising a series of juxtaposed mobile elements associated with positioning means adapted to allow, on the one hand, a modification of the altitude of the heads of the mobile elements relative to each other so as to generate at least one pattern and, on the other hand, an immobilization of the mobile elements in a chosen configuration. The positioning means can then comprise at least one actuator and be adapted to modify the altitude of the head of each mobile element relative to the average altitude of the receiving surface. The positioning means can also simply comprise locking means which are configured to, depending on their state, authorize the movement of the mobile elements or block the movement of the mobile elements.

[0037] The series of movable elements can then be organized according to a two-dimensional line or matrix. The series of movable elements can thus be adapted or configured to form at least one pattern comprising at least one one- or two-dimensional bar code.

[0038] Still within the framework of this variant, the receiving face of the support forms a loop used for the formation of a continuous sheet and the position of the movable elements is modified during the formation of the sheet to form different patterns in different places on the sheet.

[0039] According to another characteristic of the invention, the fibrous suspension is deposited in a controlled manner on the receiving face. For the purposes of the invention, the expression “controlled manner” includes in particular: a check of the position of the deposit on the receiving face, a check of the nature and / or composition of the paste during deposit and / or depending on its position, combinations of these two checks without this list being either limiting or exhaustive.

[0040] According to a variant of this characteristic, the fibrous suspension is deposited by means of a deposition head movable relative to the receiving face according to at least two degrees of freedom and in particular in translation according to two crossed axes. This is a relative movement between the deposition head and the receiving face. Thus, the deposition head can be movable and the support fixed, the head can be fixed and the support can be movable or, the deposition head and the support can both be movable.

[0041] According to another embodiment, fibrous suspensions from different sources are deposited. Thus, sources of pastes of different colors and / or concentrations and / or compositions can be used.

[0042] According to yet another embodiment, the composition of the paste is varied during deposition. For example, it is thus possible to vary the concentration of transport liquid to obtain a certain fineness of surface condition or detail on the surface and / or in the manufactured object. It is also possible to modulate the chemical composition of the paste by modifying, in particular, the concentration of additives such as, for example, dispersants such as quaternary ammonium salts in the case of the use of cellulosic fibers.

[0043] According to a characteristic of the invention, at least one external element of a nature different from that of the paste and / or its constituents is incorporated into the object being formed. Such an external element may be of any nature and for example be an insert, an electronic component, a chemical insert, a reinforcing element, a plant seed without this list being either limiting or exhaustive.

[0044] According to a characteristic of the invention, the manufacturing method comprises a step of depositing a layer of a conductive material on a fibrous matrix layer.

[0045] According to another characteristic of the invention, the paste is deposited continuously. Of course, according to the invention, the paste can also be deposited discreetly, punctually and / or in strips or segments in particular.

[0046] According to one embodiment of the invention, the paste is deposited in several layers.

[0047] According to one embodiment of the invention, the deposition of the paste is carried out in a bath of transport liquid so that no face of the layer being formed is in contact with air or a gas during the deposition phase until the desired thickness is obtained.

[0048] According to another form of implementation, one or more layers of different or distinct fibrous suspensions are successively deposited.

[0049] According to a variant of this form of implementation, at least part of the transport liquid is removed between the deposition of each layer of fibrous suspension.

[0050] According to a characteristic of the invention, part of the transport liquid is eliminated by heating.

[0051] According to an alternative embodiment of the invention, the paste used comprises particles intended to increase in volume during the removal of the transport liquid to compensate for this removal so as to avoid shrinkage phenomena and thus confer a certain dimensional stability to the fibrous matrix object during its formation. In addition, the use of such particles makes it possible to induce prestressing of the fibrous matrix, increasing its mechanical resistance characteristics. The particles used may, for example, be microbeads such as those marketed under the name EXPANCEL ® by the company AKZONOBEL.

[0052] According to a characteristic of the invention, a part of the transport liquid is removed by pressure or constraint.

[0053] According to the invention, the transport liquid may be of any suitable nature depending on the nature of the fibers used. According to one embodiment, the transport liquid is water-based.

[0054] According to the invention, the fibrous matrix may comprise fibers of any kind: synthetic, of artificial or natural origin, processed or not, and, of course, mixtures of these fibers. According to a characteristic of the invention, the fibers comprise fibers of animal and / or plant origin.

[0055] According to a variant of this characteristic, the fibers comprise cellulose fibers. The use of cellulose fibers makes it possible to take advantage of the hydrogen bonds which naturally ensure the holding and cohesion of cellulose fiber matrices without the use of glues or adhesive products. Of course, the use of cellulose fibers does not exclude the incorporation of adhesives or glue into the fibrous pulp within the scope of the invention.

[0056] Thus, it is possible to incorporate into the paste a binder, ideally compatible with the fibrous suspension and whose kinetics or even nature of solidification (polymerization, crosslinking, crystallization, etc.) is faster than those of the fibrous suspension alone so as to give the deposit mechanical strength more quickly than that resulting from the sole contribution of the fibers after elimination of the majority of the transport liquid. It should be noted that the binder used can then be permanent, i.e., be retained after the “setting of the fibers” or, on the contrary, be non-permanent, i.e., be eliminated after the “setting of the fibers”.

[0057] According to a characteristic of the invention, the fibrous paste comprises, as binder, particles of plaster or gypsum precursors such as hemihydrated or semihydrated calcium sulfate called hemihydrate and / or anhydrite Ca 2 SO 4 or anhydrous calcium sulfate. The hemihydrated calcium sulfate as well as the anhydride has the particularity of not precipitating or crystallizing in the form of gypsum above a certain dilution threshold. Thus, the rapid elimination of the transport liquid makes it possible to reach the concentration level from which the gypsum crystallizes, ensuring the coherence of the fibrous deposit. Within the framework of this characteristic, the fibrous paste may comprise at least 10% by weight of hemihydrated or semihydrated calcium sulfate and / or anhydrite and at least 50% by weight of fiber such as, for example, cellulose fibers.It should be noted that plaster and cellulose fibers are particularly compatible materials insofar as, after setting, the plaster always contains water molecules favorable to the establishment of hydrogen bonds with the cellulose fiber. Thus, the plaster / cellulose fiber composite material has particularly interesting and good mechanical resistance characteristics. According to a characteristic of the invention, the paste comprises at least 30% by mass of particles of hemihydrate or semi-hydrated calcium sulfate and / or anhydrite.

[0058] According to the invention, the stress allowing the support to pass from a non-passing state, without percolation of the transport liquid into the support, to a passing state in which the transport liquid passes into the support, can be of any suitable nature such as a mechanical and / or electrical and / or electromagnetic stress on the support.

[0059] According to one embodiment of the invention, the stress is a sufficient pressure difference, created between a part of the receiving face and a part of the face opposite the receiving face so as to cause the percolation of the transport liquid into the support and / or through the latter. This pressure difference may, for example, consist of the application of pressure to the paste deposited on the receiving face either by direct mechanical pressure or by hydraulic pressure or by the combination of the two.

[0060] According to a variant of this form of implementation, the pressure difference is created by suction at the face opposite the receiving face. The pressure difference can also be generated by a depression of the environment in contact with the face of the support opposite the receiving face.

[0061] In this variant, the suction can be applied to only part of the face of the support opposite the receiving face so as to only affect part of the receiving face.

[0062] Still within the framework of this variant, the suction can be applied only in relation to areas of the receiving face carrying paste.

[0063] According to the invention, the intensity of the depression can also be modulated either by acting on the value of the depression applied at the level of the face opposite the receiving face or by modulating the thickness of the support so as to modulate the pressure losses in the support. Thus, the support can have a constant thickness over its entire extent or a thickness whose value is likely to vary depending on the measurement point.

[0064] The invention also relates to a fibrous matrix object comprising at least one layer of fibrous material obtained according to the manufacturing method according to the invention.

[0065] According to a variant of the invention, the fibrous matrix object comprises a stack of several layers of fibrous material, each obtained according to the manufacturing method in accordance with the invention.

[0066] According to an embodiment characteristic of a manufacturing machine according to the invention, the machine comprises, as means for supplying the fibrous paste, a paste deposition head movable relative to the support in at least one direction, the deposition head further comprising means for extracting at least part of the transport liquid before depositing the paste on the support. Extracting part of the transport liquid just before depositing the paste on the support is particularly advantageous when manufacturing an object with a fibrous matrix using an additive machining process also known as 3D printing. Indeed, in the context in particular of the use of cellulose fibers, extracting part of the transport liquid in the head makes it possible to activate the formation of hydrogen bonds which contribute to the stability of the paste deposit.Similarly, when implementing plaster precursors in the paste, the extraction of the transport liquid makes it possible to increase the concentration of plaster precursors so as to initiate the plaster formation reaction, which contributes to the stability of the deposit produced. It should be noted that the plaster formation reaction being exothermic, the heat it releases contributes to the elimination of part of the transport liquid contained in the deposit.

[0067] According to one embodiment of the machine, the extraction means comprise means for suctioning the transport liquid.

[0068] According to a variant of this embodiment, the deposition head comprises at least one deposition nozzle connected to a paste reservoir by a supply channel, a part of which located upstream of the nozzle comprises a porous peripheral wall connected to a suction source.

[0069] According to a characteristic of this variant, the porous peripheral wall is formed at least in part by an isotropic or substantially isotropic material comprising an open-cell foam and / or an open-cell material obtained at least in part by agglomeration of particles and having a wettability with the transport liquid such that the contact angle of a drop of the transport liquid with the receiving face is greater than or equal to 100°, the porous material being such that the transport liquid does not percolate naturally through the porous wall without external stress and that the transport liquid percolates into the support when a controlled stress is applied to all or part of the paste / porous wall system. Preferably, the porous material constituting the porous wall is hydrophobic with respect to the transport liquid and particularly preferably superhydrophobic with respect to the transport liquid.

[0070] Of course, the different characteristics, variants and forms of implementation of the method and / or of realization of the machine according to the invention can be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other.

[0071] Furthermore, various other characteristics of the invention emerge from the examples below which illustrate non-limiting forms of implementation of the manufacturing method according to the invention of an object with a fibrous matrix. Other other characteristics of the invention also emerge from the examples described in relation to the appended figures which illustrate non-limiting forms of embodiment of machines according to the invention for implementing the manufacturing method according to the invention of an object with a fibrous matrix. There figure 1 is a schematic view of a dynamic form with a hydrophobic or even superhydrophobic porous support for the formation of a fibrous matrix object according to the invention. The figure 2 is a partial schematic view of a support with a reconfigurable area for forming a pattern on a fibrous matrix object according to the invention. The figure 3 is a schematic perspective partially torn from the support illustrated in the figure 2 . There figure 4 is a schematic view of a machine with a paste depositing head movable along the three axes X, Y, Z relative to the support receiving the paste. The figure 5 is a schematic section of a variant of the deposition head that can be implemented with the machine illustrated in figure 4 It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0072] According to a first example of implementation of the method for manufacturing an object with a fibrous matrix in accordance with the invention, it is proposed to produce an object from cellulose fibers having a volume conformation as opposed to a plate or a sheet.

[0073] For this purpose, a support is prepared in the form of a mold made from a stack of sintered polyethylene plates such as those marketed by the company 2F Technologies, for example, having pores with a size of around 100 µm and an opening factor of around 40%. The plates are assembled and machined to form two half-molds which, when assembled, define a molding cavity with a filling channel. The internal wall of the cavity then forms the receiving face of the support. The plates can then be pre-cut prior to their stacking or, on the contrary, be stacked and secured together for subsequent machining.It should be noted that to the extent that the porous material used has its characteristics of porosity and wettability on the surface and in the mass, the mold formed by stacking and machining has the same characteristics, particularly at the interfaces or joints between the stacked plates.

[0074] Furthermore, a cellulose fiber pulp is prepared by grinding and mixing paper sheets in an aqueous carrier liquid to obtain a relatively liquid pulp.

[0075] The paste is then introduced, at ambient pressure, into the mold until it is filled. Given the physicochemical properties of the mold material, the transport liquid does not percolate into the support so that the transport liquid concentration does not vary during filling.

[0076] Then, a depression is applied to the outer face of the support, which in this case is the face opposite the receiving face of the paste. The applied depression induces percolation of the transport liquid through and out of the mold so that the fibers of the paste are pressed against the walls of the mold and a hollow object with a fibrous matrix is ​​obtained.

[0077] For the manufacture of a solid object, the feed of paste is continued while the vacuum is applied to the face(s) of the support opposite the receiving face.

[0078] Such a method of manufacturing solid fiber matrix objects makes it possible to produce, for example, but not exclusively, packing elements for packaging, inserts for the production of composite parts.

[0079] The manufacture of a three-dimensional object such as a shell or a solid object in accordance with the invention may also involve rotating the support or mold so as to achieve centrifugal molding. The passage of the transport liquid through the support then results at least in part from centrifugal force, which may be supplemented by the application of a vacuum.

[0080] According to the invention, a mold made of hydrophobic and preferably superhydrophobic porous material can also be used, comprising several cavities of solid objects to be manufactured, distributed around a central channel for supplying the paste and connected to this central channel by the radial channels so as to be able to be used in a centrifuge. Thus, the paste is supplied via the central channel while the distribution of the paste in the cavities and the elimination of the transport liquid results from centrifugal force. This manufacturing method is very similar to spincasting.

[0081] According to another example of implementation of the method according to the invention, a support is prepared in the same material as for the previous example in the form of a plate whose receiving face has hollow and bumpy conformations, for example spherical caps.

[0082] Paste is applied to the entire receiving surface and then a depression is applied to the entire surface of the support opposite the receiving surface in order to eliminate some or even most of the transport liquid. This produces a sheet of paper with hollows and bumps without having to resort to embossing.

[0083] According to yet another example of implementation, a support is used in the same material as for the previous examples with a flat and hydrophobic receiving face.

[0084] Several cellulose fiber pastes are prepared, each with a different color.

[0085] The different pastes are then deposited in points on the receiving face so as to form a pattern. Since the receiving face is, on the one hand, hydrophobic and, on the other hand, adapted to not allow percolation of the paste under the effect of its own weight for small heights of water, the different points or drops of paste are stable and do not mix. When the desired quantities of the different pastes have been deposited at the chosen locations on the receiving face, suction is applied to the face of the support opposite the receiving face. This produces a fibrous matrix object with a pattern integrated into the "mass" of the fibrous matrix.

[0086] A fibrous matrix object manufactured according to the invention may, after its manufacture, undergo various treatments or operations aimed in particular at modifying the state or appearance of its external surface and / or its mechanical or chemical characteristics. The fibrous matrix object manufactured according to the invention may also be subject to machining operations and / or be integrated into a composite object.

[0087] It is also possible to manufacture an object according to the invention on a pre-existing object. Thus, it is possible to manufacture an object according to the method according to the invention in a window arranged in a sheet of paper placed on the receiving face of the support. The paste will then be deposited in such a way that when the transport liquid is removed it adheres to a part or less of the edges of the window.

[0088] There figure 1 illustrates another form of implementation of the method according to the invention for producing a fibrous matrix object in sheet or plate. For this purpose, a machine 1 called a dynamic former is used, such as described in particular by US patent 3,210,241 or marketed by the French company TECHPAP or the Canadian company CANPA. The machine 1 comprises a sealed drum tank 2 driven in rotation about its vertical axis of symmetry Δ by an electric geared motor 3. The machine 1 further comprises in the tank an annular support 4 which defines a cylindrical receiving surface 4' located at a distance from the axis Δ. The annular support 4 delimits in the tank 2 a central chamber 5 for introducing the paste and a peripheral chamber 6 for discharging the transport liquid.The machine 1 further comprises means 7 for depositing the dough on the receiving surface 4', means 8 for supplying transport liquid into the central chamber 5 and means 9 for discharging the transport liquid from the discharge chamber 6. Such a machine is well known to those skilled in the art and therefore does not require further description.

[0089] Machine 1 makes it possible in particular to deposit the paste on the receiving surface in a liquid medium so that the paste deposition is carried out in such a way that the fibrous matrix object being formed is permanently bathed by the transport liquid until the desired deposit thickness is obtained. In the context of machine 1, the stress inducing the evacuation of the transport liquid is the centrifugal force induced by the rotation of the tank during deposition. When the desired deposit thickness is reached, no more paste or transport liquid is supplied to the central chamber so that the transport liquid is entrained into the evacuation chamber from which it is evacuated.

[0090] According to the invention, at least a portion of the annular support 4 and at least the portion forming the receiving surface 4' is porous and formed at least in part by an isotropic or substantially isotropic material comprising an open-cell foam and / or an open-cell material obtained at least in part by agglomeration of particles and having a wettability with the transport liquid such that the contact angle of a drop of the transport liquid with the receiving face is greater than or equal to 100°. The material used for producing the receiving face is adapted or configured so that the transport liquid does not percolate naturally through the support without external stress and so that the transport liquid percolates into the support when a controlled stress is applied to all or part of the paste / support system.

[0091] According to an embodiment variant, a sintered polyethylene plate such as, for example, marketed by the company 2F Technologies, having pores having a size of the order of 100 µm and an opening factor of the order of 40%, was used for the formation of the support surface. The machine 1 then made it possible to produce, as a fibrous matrix object, a cellulose-based sheet which has the characteristic of not having any floc or clumps of cellulose fibers or traces induced by the receiving surface except at the places where the conformation of the latter had been modified to reveal a pattern on and in the fibrous matrix object. Thus, apart from the patterns, the cellulose-based sheet does not have any floc visible to the naked eye and has an isotropic distribution of cellulose fibers and pores.

[0092] There figure 2 illustrates another embodiment of a support for a machine according to the invention making it possible to produce a pattern on and in the fibrous matrix object produced by depositing the paste on the support. According to this embodiment, the support 20 comprises, in a zone Z of the receiving surface 21, a series of juxtaposed mobile elements 22 associated with positioning means 23 adapted to allow, on the one hand, a modification of the altitude of the heads 24 of the mobile elements relative to each other and relative to the average altitude of the receiving surface so as to generate at least one pattern and, on the other hand, an immobilization of the mobile elements in a chosen configuration.

[0093] According to the example illustrated, the part of the support forming the receiving surface is made of a material such as a sintered polyethylene plate such as, for example, those marketed by the company 2F Technologies, having pores having a size of the order of 100µm and an opening factor of the order of 40%.

[0094] In the same way, each of the movable elements 22 is formed by a parallelepiped bar with a rectangular or square base made of the same material as the rest of the receiving surface. The movable elements are then juxtaposed so as to form a rectangular matrix as shown in figure 3 formed of lines and columns allowing to create a pattern such as a one or two-dimensional code. As long as the juxtaposed elements are made of the same material as the rest of the support surface with a length lsubstantially equal to the thickness e of the support the behavior of the entire receiving surface including zone Z is substantially uniform. It should be noted that the difference in length / and thickness e corresponds to the depth of the pattern produced.

[0095] In the present case, the positioning means 23 comprise, for each mobile element 22, a control rod 25 linked to an electromagnetic actuator 26 controlled by a control unit UC. Each actuator 26 has two states, respectively high and low. The high state corresponds to a position in which the head of the corresponding mobile element is at the same level as the rest of the receiving surface while the low state corresponds to a position in which said head is located below the level of the rest of the receiving surface. Thus, the control unit UC can control the configuration of the zone Z in order to produce patterns according to requirements and in particular to modify the message likely to be coded by the two-dimensional bar code defined by the zone Z during the successive manufactures of fibrous matrix objects on the receiving surface 21.

[0096] There figure 5 shows another machine 30 allowing the manufacture of a fibrous matrix object according to the invention by depositing paste on a receiving surface by means of a head movable along the three axes X, Y, Z.

[0097] The machine 30 comprises a tank 31 equipped with a porous support 32 according to the invention which delimits in the tank 31 a deposition chamber 33 located above the support and an evacuation chamber 34 located below the support 32. The deposition chamber 33 is open on the top of the tank 31 while the evacuation chamber 34 is connected to a suction unit 35. The suction unit 35 is adapted to establish a vacuum in the evacuation chamber 34 so as to suck up the fluids which are liquid and / or gaseous therein and to induce the percolation through the support 32 of the transport liquid of the paste deposited on the receiving face 36 of the support 32.

[0098] The machine 30 comprises, as means 40 for depositing paste on the receiving surface, a depositing head 41 connected to at least one paste supply unit 42. The depositing head 41 is carried by a gantry system 43 of the cross table type which is configured to ensure a displacement of the depositing head 41 in translation along the three axes X, Y, Z forming an orthogonal base of the space. The XY axes are then substantially parallel to the horizontal plane defined by the receiving surface 36 while the Z axis is substantially orthogonal to the receiving surface 32. The gantry system 43, the suction unit 35 and the supply unit are then controlled by a control unit UC.

[0099] Thus, the control unit UC controls all the elements of the machine so as to deposit the paste on the receiving surface 36 to form a fibrous matrix object according to a process similar to additive machining also called 3D printing. During the deposition, the suction unit 35 operates so as to ensure the percolation of the transport liquid as the paste is deposited.

[0100] According to an alternative embodiment of the invention, the deposition head 41 is configured to allow extraction of a portion of the transport liquid before deposition of the paste on the receiving surface 36.

[0101] Thus, the deposition head 41 comprises a supply channel 45 connected to the supply unit 42 and opening at a deposition nozzle 46. The deposition head 41 then comprises, as means for extracting the transport liquid, a part P of the supply channel 45 located just upstream of the nozzle 46 which is made of a hydrophobic and preferably superhydrophobic porous material. The part P is in the form of a tube 47 made of porous material, the inner wall 48 of which forms the corresponding part of the supply channel 45 and the outer wall 49 of which forms a wall of an annular suction chamber 50 surrounding the tube 47.

[0102] The tube 47 is made of a hydrophobic or even superhydrophobic porous material having the same characteristics as that of the support as described previously. It should be noted that the hydrophobic characteristics of the material make it possible to avoid the risk of clogging of the feed channel at the nozzle.

[0103] The suction chamber 50 is connected to the suction unit 35 via control means 51 controlled by the control unit UC. Thus, when the paste is deposited, the control unit UC controls the suction at the suction chamber 50 so as to extract the transport liquid to increase the viscosity of the paste so as to increase its strength. In addition, when using a paste containing cellulose fibers, the extraction of the transport liquid activates the formation of hydrogen bonds. In the same way, in the case of the use of plaster precursors in the paste, the extraction of the transport liquid activates the crystallization of the gypsum, which contributes to the solidity of the deposit during the formation of the fibrous matrix object.

[0104] Furthermore, it should be noted that the machine as described in connection with the figures 4 et 5can also be used for bath deposition of transport liquid. In this case, the tank 31 is filled with the transport liquid during the entire phase of deposition of the paste to form the fibrous matrix object.

[0105] Of course, various other variations of the invention may be envisaged within the scope of the appended claims.

Claims

1. A method for manufacturing an object with a fibrous matrix consisting of depositing, onto a reception face (4', 21, 36) of a support (4, 20, 32), at least one fibrous pulp , at least comprising fibres and a carrier liquid, and consisting of removing at least a portion of the carrier liquid, with the reception face (4', 21, 36) being adapted or configured so that the carrier liquid does not naturally percolate through the support (4, 20, 32) without an external stress and so that the carrier liquid percolates through the support (4, 20, 32) when a controlled stress is applied to all or part of the pulp / support system, said method being characterised in that the part of the support forming the reception face (4', 21, 36) is at least porous and is at least partly formed by an isotropic or substantially isotropic material comprising an open-cell foam and / or an open-cell material at least partly obtained by particle agglomeration and exhibiting wettability with the carrier liquid such that the contact angle of a drop of the carrier liquid with the reception face is greater than or equal to 100°.

2. The method for manufacturing an object with a fibrous matrix according to the preceding claims, characterised in that the material forming the reception face (4', 21, 36) is selected so that the carrier liquid partially wets the reception face such that the contact angle of a drop of the carrier liquid with the reception face (4', 21, 36) is greater than or equal to 150°.

3. The manufacturing method according to the preceding claim, characterised in that the material forming the reception face (4', 21, 36) comprises particles of plastic material, preferably of polyolefins and even more preferably of polyethylene and / or polypropylene.

4. The method for manufacturing an object with a fibrous matrix according to any of the preceding claims, characterised in that the reception face (4', 21, 36) has at least one pattern or shape, the smallest dimension of which is greater than or equal to smallest average dimension of the fibres of the pulp.

5. The method for manufacturing an object with a fibrous matrix according to any of the preceding claims, characterised in that the fibrous suspension is deposited by means of a deposition head (41) that is movable relative to the reception face (4', 21, 36) by at least two degrees of freedom.

6. The method for manufacturing an object with a fibrous matrix according to any of the preceding claims, characterised in that the pulp comprises particles of hemihydrate or semihydrated calcium sulfate and / or of anhydrate.

7. A machine for manufacturing an object with a fibrous matrix comprising a first support (4) with a reception face (4') for receiving a fibrous pulp for forming the object at least comprising fibres and a carrier liquid, with the reception face (4') being adapted or configured so that the carrier liquid does not naturally percolate through the support (4) without an external stress and so that the carrier liquid percolates through the support (4) when a controlled stress is applied to all or part of the pulp / support (4) system, said machine being characterised in that the part of the first support (4) forming the reception face (4') is at least porous and is at least partly formed by an isotropic or substantially isotropic material comprising an open-cell foam and / or an open-cell material at least partly obtained by particle agglomeration and exhibiting wettability with the carrier liquid such that the contact angle of a drop of the carrier liquid with the reception face (4') is greater than or equal to 100°.

8. The machine according to claim 7, characterised in that the material forming the reception face (4') of the support (4) is selected so that the carrier liquid partially wets the reception face (4') such that the contact angle of a drop of the carrier liquid with the reception face (4') is greater than or equal to 150°.

9. The machine according to any of claims 7 or 8, characterised in that material forming the support (4) comprises particles of polyolefins, preferably of polyethylene and / or polypropylene.

10. The machine according to any of claims 8 to 9, characterised in that the reception surface (4') comprises at least one movable element (22), the displacement of which allows the conformation of the corresponding zone (Z) of the reception surface (4') to be modified.

11. The machine according to claim 10, characterised in that the reception surface (4') comprises at least one zone (Z) comprising a series of juxtaposed movable elements (22) associated with positioning means adapted to allow, on the one hand, the altitude of the heads (24) of the movable elements (22) to be modified relative to each other so as to generate at least one pattern and, on the other hand, the movable elements (22) to be immobilised in a selected configuration.

12. The machine according to any of claims 8 to 11, characterised in that it comprises a deposition head (41) that comprises at least one deposition nozzle (46) connected to a pulp reservoir (42) by a feed channel (45), a part of which located upstream of the nozzle (46) comprises a porous peripheral wall (48) connected to a suction source (35).

13. The manufacturing machine according to the preceding claim, characterised in that the porous peripheral wall (48) is at least partly formed by an isotropic or substantially isotropic material comprising an open-cell foam and / or an open-cell material at least partly obtained by particle agglomeration and exhibiting wettability with the carrier liquid such that the contact angle of a drop of the carrier liquid with the reception face (4') is greater than or equal to 100°, with the porous material being adapted or configured so that the carrier liquid does not naturally percolate through the support (4) without an external stress and so that the carrier liquid percolates through the support (4) when a controlled stress is applied to all or part of the pulp / support (4) system.

14. The machine according to the preceding claim, characterised in that the material forming the porous peripheral wall (48) is selected so that the carrier liquid partially wets the reception face such that the contact angle of a drop of the carrier liquid with the reception face is greater than or equal to 100° and preferably greater than or equal to 150°.

15. The machine according to any of claims 12 to 14, characterised in that the deposition head is movable relative to the reception face with at least two degrees of freedom.

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