Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
  • B29C51/14—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor using multilayered preforms or sheets
  • B29C51/145—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor using multilayered preforms or sheets having at least one layer of textile or fibrous material combined with at least one plastics layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
  • B29C70/02—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising combinations of reinforcements, e.g. non-specified reinforcements, fibrous reinforcing inserts and fillers, e.g. particulate fillers, incorporated in matrix material, forming one or more layers and with or without non-reinforced or non-filled layers
  • B29C70/021—Combinations of fibrous reinforcement and non-fibrous material
  • B29C70/025—Combinations of fibrous reinforcement and non-fibrous material with particular filler
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B23/00—Layered products comprising a layer of cellulosic plastic substances, i.e. substances obtained by chemical modification of cellulose, e.g. cellulose ethers, cellulose esters, viscose
  • B32B23/10—Layered products comprising a layer of cellulosic plastic substances, i.e. substances obtained by chemical modification of cellulose, e.g. cellulose ethers, cellulose esters, viscose next to a fibrous or filamentary layer
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
  • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
  • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
  • B32B5/30—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being formed of particles, e.g. chips, granules, powder
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C2/00—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels
  • E04C2/02—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials
  • E04C2/10—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of wood, fibres, chips, vegetable stems, or the like; of plastics; of foamed products
  • E04C2/24—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of wood, fibres, chips, vegetable stems, or the like; of plastics; of foamed products laminated and composed of materials covered by two or more of groups E04C2/12, E04C2/16, E04C2/20
  • E04C2/246—Building elements of relatively thin form for the construction of parts of buildings, e.g. sheet materials, slabs, or panels characterised by specified materials of wood, fibres, chips, vegetable stems, or the like; of plastics; of foamed products laminated and composed of materials covered by two or more of groups E04C2/12, E04C2/16, E04C2/20 combinations of materials fully covered by E04C2/16 and E04C2/20
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
  • B29C51/08—Deep drawing or matched-mould forming, i.e. using mechanical means only
  • B29C51/082—Deep drawing or matched-mould forming, i.e. using mechanical means only by shaping between complementary mould parts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2101/00—Use of unspecified macromolecular compounds as moulding material
  • B29K2101/12—Thermoplastic materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2711/00—Use of natural products or their composites, not provided for in groups B29K2601/00 - B29K2709/00, for preformed parts, e.g. for inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2007/00—Flat articles, e.g. films or sheets
  • B29L2007/002—Panels; Plates; Sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2009/00—Layered products
  • B29L2009/001—Layered products the layers being loose
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
  • B32B2262/10—Inorganic fibres
  • B32B2262/101—Glass fibres
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
  • B32B2264/06—Vegetal particles
  • B32B2264/062—Cellulose particles, e.g. cotton
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/70—Other properties
  • B32B2307/738—Thermoformability
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2607/00—Walls, panels

Definitions

• the present invention relates to a composite panel based on thermoplastic material as well as a thermoforming method for manufacturing it.
• composite panels which are light and inexpensive while having good mechanical properties, in particular as regards their impact and flexural strength.
• these mechanical properties should not be excessively affected by temperatures of the order of 60 to 100 ° C., which are commonly reached near propulsion or heating devices, or even when a non-ventilated vehicle is exposed to the sun
• thermoplastic material loaded with wood particles which are widely used in the automotive industry. Although these plates can in certain cases pose problems if they are subjected to an extremely deep thermoforming, it would be advantageous, given their low cost and their low density, to be able to use them as starting material for manufacturing composite panels presenting the desired properties.
• thermoplastic material comprising reinforcing fibers dispersed within them.
• these fibers generally increase the risk of tearing in the case of deep thermoforming, and these plates have a high density.
• document DE 204831 1 describes a composite panel based on a thermoplastic material, comprising one or more felts (mats) or fabrics of reinforcing fibers, preferably textiles, as well as wood fibers uniformly dispersed throughout its thickness.
• This last characteristic is disadvantageous: in particular, it reduces the mechanical strength of the panel and increases the risk of tearing during its thermoforming. Without this explanation being limiting, it is suspected that the proximity, and a fortiori the contact, of the wood fibers with the reinforcing fibers could moreover harm the anchoring of the latter within the thermoplastic material, thus increasing the risk of tearing during deep thermoforming.
• thermoforming is also absolutely not mentioned.
• thermoplastic material is used for the entire panel, which notably excludes the use of an optimized material, for example less expensive, in the central area.
• the manufacturing process used in this document does not guarantee the uniformity of the thickness of each of the layers of the panel obtained.
• the present invention therefore aims to provide a lightweight composite panel, simple to manufacture, inexpensive, having good resistance to bending and impact, and capable of withstanding without tearing a thermoforming, even deep. It is further desirable that this panel can be manufactured in a simple manner from a plate of thermoplastic material reinforced with cellulosic particles, such as a WOOD-STOCK® plate.
• the invention relates to a composite panel comprising at least three layers based on thermoplastic material, among which an internal layer (A) containing cellulose particles dispersed therein, as well as two lateral layers (B), arranged on either side of said internal layer, reinforced with fabrics of reinforcing fibers and substantially free of cellulosic particles.
• thermoplastic material among which an internal layer (A) containing cellulose particles dispersed therein, as well as two lateral layers (B), arranged on either side of said internal layer, reinforced with fabrics of reinforcing fibers and substantially free of cellulosic particles.
• thermoplastic material constituting each of the layers (A) and (B) essentially comprises one or more thermoplastic polymers, such as for example polyolefins, polyamides, fluorinated polymers or vinyl polymers.
• thermoplastic polymers such as for example polyolefins, polyamides, fluorinated polymers or vinyl polymers.
• polyolefins such as homo- and copolymers of ⁇ -olefins, and in particular propylene.
• the copolymers optionally used advantageously comprise at least 70% by mass of propylene.
• Excellent results have been obtained with polypropylene (PP) homopolymer, that is to say comprising at least 99% by mass of propylene.
• the thermoplastic material may also comprise one or more usual additives such as stabilizers, lubricants, antioxidants, pigments, antistatic agents, compatibilizers, coupling agents, etc.
• additives such as stabilizers, lubricants, antioxidants, pigments, antistatic agents, compatibilizers, coupling agents, etc.
• the amounts of such additives can be any; they are generally moderate.
• no additive is present in amounts exceeding 10% relative to the mass of the thermoplastic material.
• thermoplastics constituting the internal layer (A) and each of the two lateral layers (B) can be identical or different.
• a different thermoplastic material is used for the inner layer (A), in particular having less homogeneous or lower mechanical properties than the one or more thermoplastic materials constituting the side layers (B). It may in particular be a foam or, more advantageously, a less expensive recycled thermoplastic material.
• the polymers included in these thermoplastic materials have sufficient mutual compatibility, so that it is not necessary to interpose an adhesive layer between these two layers. It can advantageously be different polyolefins.
• the thermoplastic material constituting each of the layers (A) and (B) comprises at least 50% by mass of one or more polyolefins (relative to the total mass of the polymers of the layer in question).
• one or more propylene polymers are used as polyolefin (s).
• the thermoplastic material constituting each of the layers (A) and (B) comprises at least 70% by mass of propylene, which may as well be contained in a homopolymer, in a copolymer or in a mixture of several homo - And / or copolymers.
• cellulosic particle can be used in the internal layer (A), in particular sawdust, wood flour, wood fibers, particles of paper or cardboard, or vegetable fibers such as fibers. flax, cotton or bamboo, straw waste, and mixtures thereof. These particles preferably have average dimensions of about 0.1 to 3 mm. It is desirable that their water content does not exceed 15% by mass.
• compatibilizing agents such as unsaturated organosilanes (vinyltriethoxysilane, gamrnamethacryloxypropyltrimethoxysilane, etc.), as well as possibly one or peroxides.
• the effect of such compatibilizers can be further increased by the joint use of small amounts of suitable crosslinking agents, for example poly- tri-, tetra- or penta-acrylates.
• Another compatibilization method consists in using a thermoplastic material comprising one or more polymers modified so as to exhibit an increased affinity with respect to cellulosic particles, such as a polyolefin grafted with maleic anhydride.
• the concentration of the cellulosic particles within the internal layer (A) is generally at least 30 parts by mass (relative to 100 parts by mass of thermoplastic material), preferably at least 70 parts. Furthermore, this concentration is generally at most 250 parts, and preferably at most 150 parts.
• each of the two lateral layers (B) comprises one or more fabrics of reinforcing fibers, which can be of any known type. It is preferred to use inorganic fibers, for example carbon, glass or metal fibers. Very good results have been obtained with glass fiber fabrics. These fibers have a long length, generally several decimeters; their length often corresponds at least to the length or width of the panel. These fibers are advantageously compatible, or made compatible, with the thermoplastic material; to this end, they can in particular be provided with an appropriate size, for example based on silanes.
• the fiber fabrics used have a structure favoring their anchoring within the thermoplastic material.
• the side layers (B) can also be made from fabrics of reinforcing fibers and fibers of thermally plastics material. Further details on the fabrication of layers (A) and (B) are provided below, in relation to the process.
• their constituent thermoplastic material is preferably homogeneous; in particular, it does not have a fibrous structure, even in the case of layers (B) made from fabrics co-mixed with reinforcing fibers and thermoplastic fibers.
• reinforcement fiber fabrics leads to higher mechanical performance than other types of fiber-based reinforcement such as uniformly dispersed short fibers or felts (mats). In addition, it greatly reduces the risk of tearing the panel in the event of deep thermoforming. This result is surprising insofar as the deformability of an article based on thermoplastic material reinforced with a fiber fabric is a priori considered to be lower than if this article was reinforced with short fibers, for example.
• the concentration of reinforcing fibers within each of the side layers (B) is generally of the order of 10 to 70% (relative to the total weight of each of the layers (B)).
• concentration is expressed relative to the mass of the entire panel, we arrive at significantly lower values than in panels uniformly loaded with fibers, for comparable mechanical properties, which leads to a specific mass and a lower material costs.
• the two lateral layers (B) are substantially free of cellulosic particles, that is to say that they contain less than 5% by mass thereof. Ideally, these layers are completely free of cellulosic particles.
• the layers (A) and / or (B) can optionally contain one or more conventional inorganic fillers such as calcium carbonate, talc, etc.
• the thicknesses of the layers (A) and (B) can be freely chosen according to the requirements imposed on the composite panel.
• the thickness of the inner layer (A) is generally at least 1 mm. It is generally at most 4 mm.
• the thickness of each of the lateral layers (B) is generally at least 0.1 mm. It is also generally at most 0.5 mm.
• the ratio between the thickness of the central layer (A) and that of each of the lateral layers (B) is between 2 and 40.
• the composite panel of the invention may possibly comprise one or more other layers of any material, provided that their presence does not disturb the thermoforming of the panel.
• additional layers are however preferably also based on thermoplastic material.
• It may in particular be a thin decorative layer of thermoplastic material applied to at least part of the outer surface of one of the side layers (B), or of each of the two side layers (B).
• Such decorative layers can for example be made from PVC or polyolefins, optionally in the form of a foam layer with a closed surface, and can optionally be grained or textured.
• a layer of adhesive can be interposed between a side layer (B) and any adjacent surface decorative layer.
• the lateral layers (B) are not necessarily immediately adjacent to the internal layer (A). Furthermore, one or more other layers may optionally be arranged on the side of a side layer (B) opposite the side where the inner layer (A) is located, that is to say closer to one of the two exterior surfaces of the panel.
• composite panels having the following structures could meet the definition of the invention B / A / B, D / B / A / B / D, D / B / A / B, B / D / A / B, B / D / A / D / B, D / B / D / A / B (D representing any layer, or even several layers whatever).
• the side layers (B), and in particular the reinforcing fiber fabrics which they contain are not too far from the exterior surfaces of the panel. It is preferred that the distance (measured perpendicular to the thickness of the panel) separating the center of the thickness of each side layer (B) from the nearest outer surface of the panel does not exceed the distance separating the centers of the thickness of layers (A) and (B).
• the composite panels of the invention can in particular be used in the interior trim of vehicles, for example for manufacturing dashboards, rear panels, door trim, bodywork elements, etc.
• the panels can be manufactured by any known process, continuous or discontinuous, in particular by rolling or hot pressing of the different layers
• the manufacture of the composite panels of the invention can advantageously be carried out in line with the manufacture of said plates, which avoids having to heat them. Another particularly advantageous method of manufacturing the panels is described below. Because of the advantages offered by the panels of the invention when thermoformed, the invention also relates to a panel as described above, thermoformed.
• thermoformed panel is intended to denote a panel which has been shaped so that at least one of its parts undergoes a deformation which, measured perpendicular to the mean plane of the panel, is at least 2 times its thickness, and in particular at least 10 times its thickness.
• Another aspect of the present invention relates to a particular method allowing the manufacture of a composite panel as described above. According to the previously known methods, a first manufacturing step makes it possible to obtain a flat composite panel, for example by rolling or hot pressing of different layers. This panel can then be thermoformed in a second step. Thermoforming is therefore applied to a monolithic composite panel, sometimes thick, which generally leads to tearing in the event of deep thermoforming.
• thermoforming consists in placing the panel between two half-molds each having the shape of the article which it is desired to obtain, and applying by means of these a high pressure to the panel, after having heated it.
• the two half-molds are generally qualified as male and female half-molds respectively, according to their shape.
• the present invention also aims to provide a simple method of manufacturing composite panels as defined above, which makes it possible to assemble their different layers and to thermoform them, even deeply, simultaneously, without causing tearing.
• another object of the present invention relates to a process for thermoforming a composite panel comprising at least three layers based on thermoplastic material, among which an internal layer (A) containing cellulosic particles dispersed therein, as well as two lateral layers (B), arranged on either side of said internal layer, reinforced with fabrics of reinforcing fibers and substantially free of cellulosic particles, according to which these different layers are assembled and thermoformed simultaneously, without prior assembly layers (A) and (B).
• This process combines assembly and thermoforming, which leads to saving time and energy, since only one heating is enough to assemble the different layers and simultaneously thermoform the composite panel thus obtained.
• thermoforming a thermoforming such that at least part of the panel undergoes during thermoforming a deformation which, measured perpendicular to the mean plane of the panel, is at least 5 times its thickness, and in particular at least 15 times its thickness.
• the method is especially advantageous when the slope of at least one zone of the edge of the deformed part forms an angle of at least 30 ° relative to the mean plane of the panel.
• the various layers are placed in a metal frame, in such a way, however, that their relative sliding is possible.
• a frame comprising two similar parts which are placed on either side of the different layers stacked on top of each other, so as to pinch and stretch them while subjecting them to a definite pressure on their periphery.
• This pressure must be high enough so that the different layers are taut and substantially flat, but low enough to allow displacement of the layers or of some of their parts if necessary, to avoid any tearing.
• One can in particular use a frame provided springs or cylinders arranged at regular intervals on its periphery, so as to exert a determined pressure on the periphery of the stack of layers.
• the different layers have dimensions greater than those of this frame, and are arranged therein so as to extend beyond it, so that they always remain pinched by the frame even after a slight lateral movement, if any. It is moreover obvious that the frame used must have dimensions greater than those of the mold, so as not to prevent its closing.
• the different layers can be preheated together, after having been superimposed, or else separately, before being superimposed.
• the stacking of the different layers, secured by a frame as described above or by any equivalent device is then placed in an oven, for example infrared, in which it is heated beyond of the processing temperature of the thermoplastic which has the highest processing temperature.
• an oven for example infrared, in which it is heated beyond of the processing temperature of the thermoplastic which has the highest processing temperature.
• Tf melting temperature
• PVC amorphous thermoplastic material
• the stack is heated to a temperature of about 190 ° C ( ⁇ 20 ° C).
• the different layers are not assembled before their thermoforming, they are stacked on top of each other, and their simple contact is generally sufficient to ensure the heating of the internal layer through the external layers
• the choice of infrared radiation the appropriate wavelength also makes it possible to influence its penetration into the layers of thermoplastic material. It can also be useful to confer on the different layers different absorption powers by means of pigments and / or of suitable charges. Thus, for example, very good results have been obtained using non-pigmented side layers and an inner layer (A) of dark color.
• the preheated stack is quickly introduced into a mold thermoforming, where the layers are simultaneously assembled and thermoformed by applying high pressure to them.
• the mold is cooled, and the panel is allowed to cool therein under pressure to a determined temperature, for example up to 50 ° C., before extracting it.
• the duration of this pressing depends in particular on the thickness of the panel.
• the heating and the thermoforming can both take place in the mold.
• the stack of different layers can be placed directly, without preheating, between two half-molds fixed to the two jaws of a heating press. These jaws, and therefore the mold, are first partially closed, so that the two half-molds come into contact with the stack. The mold is not completely closed until the stack has reached the temperature necessary for thermoforming.
• the residence time in the heating press will require in this case a much longer duration than in the previous case, generally of the order of several minutes, in order to allow each of the layers to reach the necessary temperature. thermoforming.
• thermoforming the panel can possibly be cooled in the same press, this particular variant would require the press to alternate heating and cooling, which would increase the duration of the process. It is therefore preferable, when this variant is chosen, to use a heating press and a cooled press.
• the mold is detached from the jaws of the heating press, without opening it, and it is installed in the cooled press, where the panel it contains can cool under pressure.
• the layers (A) and (B) are not joined before their thermoforming, neither directly nor indirectly, but are simply stacked on top of each other. Regarding any additional layers, they can either be pre-assembled with one of the layers (A) and (B), or else be previously joined to any other layer.
• the method is carried out in a thermoforming mold comprising a male half-mold and a female half-mold, and a vacuum is created in the female half-mold during at least part of the thermoforming; preferably, the pressure is reduced to a value of 0.05 to 0.02 MPa.
• the stack of layers is deposited on the female half-mold, in contact with its entire periphery, which defines a closed volume as far as the shape of the female half-mold lends itself to it. We then put this volume in depression.
• the vacuum thus applied generally does not in itself cause the application of the stack of layers against the entire surface of the female half-mold.
• both the internal layer (A) and the lateral layers (B) are manufactured separately, in steps prior to thermoforming, and are each in the form of homogeneous sheets of thermoplastic material comprising different reinforcements or fillers .
• the internal layer (A) can be produced in a manner known per se, for example by the extrusion of a thermoplastic material with which the desired quantity of cellulose particles has been mixed, by means of an extruder provided with a flat die, possibly followed by a grille.
• the side layers (B) can also be produced by any suitable technique, for example by impregnating a fabric of fibers with a molten thermoplastic material, or by laminating a fabric of fibers between two sheets of heated thermoplastic material. .
• the lateral layers (B) can also be produced from one or more fabrics of reinforcing fibers and fibers of thermoplastic material ("knitted fabrics"), such as for example the composite polypropylene-glass fibers TWINTEX® from VETROTEX.
• thermoplastic material reinforced with reinforcing fiber fabrics.
• the anchoring of the reinforcing fibers within the thermoplastic material is particularly good.
• the lateral layers (B) are not used in the form of such homogeneous plates, but are directly used in the form of fabrics made up of reinforcing fibers and fibers of thermoplastic material, such as described above, without prior step of consolidation of these fabrics into homogeneous plates (that is to say plates of which the constituent thermoplastic material is homogeneous).
• the use of such mixed fabrics leads to additional advantages: in particular, it makes it possible to carry out even deeper thermoformings without the risk of tearing. In addition, the panels thus obtained are more homogeneous.
• the proportion of reinforcing fibers is 30 to 70% relative to the total weight of these fabrics.
• Example 3 is in accordance with the invention, and Examples 1R, 2R and 4R are given for comparison. Examples 1R to 4R - Properties of different composite panels
• thermoforming process in two stages: the heating and the thermoforming proper in a first press, heated, and a cooling under pressure in a second, cooled press, in which we transfer the mold containing the panel after thermoforming.
• the operating conditions were as follows:
• the different panels measured 250 x 350 mm, and had the following structure: (1R) WOOD-STOCK plate (marketed by G. O R. Applicazioni Spécial.), made of PP loaded with 50% by mass of wood particles, 2.5 mm thick.
• (2R) panel obtained by hot pressing of a stack of 4 layers of balanced fabrics (that is to say comprising the same number of fibers per unit of length in each of the two main directions) of fibers streaked with glass and of PP.
• These fabrics have a surface mass of 600 g / m 2 and a mass content of glass fibers of 60%.
• (4R) AZDEL® PM 10400 plate consisting of a polypropylene plate reinforced with an isotropic felt (mat) of long glass fibers.
• the composite panels thus produced had the following properties.
• the impact resistance was evaluated by means of a non-notched Charpy test (standard
• the panels according to the invention have a low specific mass (D), good impact resistance, as well as a high flexural modulus (in particular when expressed by unit of mass - cf. reports F20 / D and F] ⁇ f / R), and relatively independent of temperature (see the ratio F100 / F20), despite a relatively low content of glass fibers (23%).
• the stack of the three layers is heated by infrared radiation to a temperature of 190 ° C., and introduced into a thermoforming mold conditioned at a temperature of 30 ° C. ⁇ 10 ° C., the male part of which is fixed to the upper plate. of a press, has a frustoconical protrusion 22 cm in diameter (at the base) and 55 mm high, with a draft angle of 5 °, and the female part of which, fixed to the lower plate of the press, comprises a correspondingly shaped cavity. Pressing is carried out under a pressure of 1.6 MPa.
• Example 5 is repeated using exclusively a WOOD-STOCK plate, without any side layer (with preheating at 175 ° C instead of 190 ° C). The panel obtained after thermoforming is torn.
• Example 5 is repeated using exclusively an Azdel plate identical to that used in Example 4R, without any side layer (with preheating to 190 ° C). The panel obtained is also torn.

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• Engineering & Computer Science (AREA)
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• Structural Engineering (AREA)
• Laminated Bodies (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)

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• 1997
  • 1997-05-03 WO PCT/EP1997/002430 patent/WO1997043121A1/fr not_active Application Discontinuation
  • 1997-05-03 EP EP97923062A patent/EP0898511A1/de not_active Withdrawn
  • 1997-05-03 CN CN97196497A patent/CN1225604A/zh active Pending
  • 1997-05-03 AU AU28971/97A patent/AU2897197A/en not_active Abandoned
  • 1997-05-03 JP JP09540513A patent/JP2000510062A/ja active Pending

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