Composite panel of plastic material, and process and device for its fabrication

Abstract: The invention relates to a composite panel of plastic material, preferably of thermoplastic material, comprising at least one layer (1') of filled thermoplastic material, in particular of polypropylene filled with sawdust and/or wood flour and/or wood shavings or similar, known as Woodstock. At least one additional layer (5') consisting at least partially of fibrous thermoplastic material is applied to the layer (1') of Woodstock. This is done by compression and simultaneous partial or complete fusion of the fibrous thermoplastic material and of the layer of Woodstock (5), providing a mechanical fixing by mutual interpenetration of the two layers (1, 5) and incorporation of the non-fused parts such as fibres and fillings. This produces a layer (5') similar to plastic material, with a substantially smooth surface which retains at least partially, for solely aesthetic and/or structural purposes, the fibrous pattern and/or structure. The invention also relates to a process and a device for fabricating the panel according to the invention.

Description: The invention relates to a composite panel of plastic material, according to the preamble of claim 1. JP-A-61005933, JP-A-56005729, JP-A-61125834, JP-A-63170032 disclose a composite panel of plastic material comprising at least one layer of filled thermoplastic material and at least one additional layer consisting at least partially of fibrous thermoplastic material, this additional layer being applied to one face of the layer of filled thermoplastic material. The bonding occurs either only mechanically or by means of lamination by compression under heat. EP-A-0472436 discloses an analogous panel in which an intermediate layer of polypropylene is used as an adhesive sheet for connecting the layer of filled thermoplastic material to the layer of fibrous material. DE-A-2727285 discloses a method for bonding a layer of fibrous fabric material to a base layer of filled thermoplastic material, in which the base layer is extruded and to this extruded base layer the fabric layer is bonded by means of heated pressing drums through which the two superimposed layers are driven. The object of the invention is-to provide a panel of the type indicated above, which is easily fabricated and relatively economical and which makes it possible to improve the mechanical and/or aesthetic properties of composite panels, while keeping unchanged the known characteristics of the said panels, in particular the good thermoforming or moulding characteristics. The invention is also intended to provide a process of fabrication of the said panels which can be used without seriously complicating the known processes of fabrication of said panels and/or without increasing the duration of the process, while limiting to a minimum the work required to adapt existing devices for the fabrication of said panels. The invention achieves the above objects with a panel of plastic material according to the preamble of claim 1 and showing the features of the characterising part of claim 1. The additional layer comprising the plasticized fibrous thermoplastic material may consist of: a felt of thermoplastic fibres, short or long, with random orientation; a fabric or non-woven fabric of fibres of thermoplastic material; a felt, fabric or non-woven fabric of mixtures of fibres of thermoplastic material and of other synthetic and/or natural materials; or thermoplastic lattices, glass fibres, or similar. Preferably, in order to obtain a good chemical bond between the two layers, the additional layer of fibrous thermoplastic material may comprise at least one partial component of polypropylene. The invention also relates to a process for the fabrication of the composite panel of plastic material described initially, comprising the steps defined in the characterizing part of claim 8. Further improvements of the process are defined in claims 9 to 13. According to an improvement of the composite panel, a layer containing plasticized fibrous thermoplastic material may be provided on both faces of the panel of filled polypropylene. As an alternative to the second layer containing the fibrous thermoplastic material, a polypropylene film may be applied to the said panel. The second layer of plasticized fibrous thermoplastic material or polypropylene film is applied to the panel of filled polypropylene by the same process as that used for the first additional layer containing fibrous thermoplastic material, and in particular by compression of the layers against the said panel with simultaneous heating, especially at the stage of calendering the said panel in the same calendering pass in which the first layer containing the fibrous thermoplastic material is applied, or in a subsequent calendering pass. The invention also provides equipment for the fabrication of the panel of plastic material and for the application of the previously mentioned fabrication process which will be described subsequently. The advantages of the invention will be clearly understood from the above description. The composite panel of thermoplastic material not only has excellent thermal deformability and a smooth and plasticized exterior appearance, but also has a somewhat higher degree of mechanical strength than the known panel, owing to the partial retention of the fibrous structure. Moreover, the use of thermoplastic fibres consisting to a large extent of polypropylene makes the composite panel recyclable to a large extent. The process is extremely simple and does not require complicated arrangements or an extension of the manufacturing cycle. The device for the application of the process may also be made as a simple and inexpensive addition or modification to existing installations for the fabrication of conventional panels of filled polypropylene. The invention also relates to other characteristics which further improve the composite panel of thermoplastic material, the process and the device for its fabrication as mentioned above, and which form the subject of the subsidiary claims. The particular characteristics of the invention and the advantages derived therefrom will be understood in greater detail from the description of some preferred embodiments, illustrated by way of example and without restriction in the attached drawings, in which Figs. 1 and 2 show two variant embodiments of equipment for the fabrication of a composite panel of plastic material according to the invention. Fig. 3 shows a detail of the two layers of Woodstock and fibrous thermoplastic material before they are fixed together. Fig. 4 shows in a similar way to Fig. 3 a detail of the panel after the fixing together of the layers of Woodstock and of fibrous thermoplastic material. With reference to Fig. 1, a panel 1 of polypropylene filled with wood flour and/or sawdust and/or wood shavings or similar, known as Woodstock, is extracted from an extrusion aperture 2 and fed between two calendar rollers 103, 203 of a following calender 3. The two calender rollers 103, 203 are parallel to each other, are heated to specified temperatures, and exert a predetermined pressure on the panel 1; they are also rotated in opposite directions to each other. The ratio of the thickness of the panel 1 to the aperture between the lips of the drawing machine is preferably between 1:1 or 1.5:1 and 4:1, in particular between 2:1 and 3:1. For example, for a panel thickness of 2 mm, the aperture between the lips of the drawing machine 2 will be between 4 and 6 mm. A strip 5, consisting at least partially of fibres of thermoplastic material, is unwound from a storage reel 4 which is mounted rotatably parallel to the two calender rollers 103, 203 on braked expanding bars (not shown in detail), and this strip 5 is fed together with the panel 1 between the calender rollers 103, 203. In the example shown in Fig. 1, the reel 4 of strip 5 comprising fibres of thermoplastic material is disposed below the pair of calender rollers 103, 203, so that the strip 5 is superimposed on and is consequently fixed to the lower face of the said panel 1. The fixing takes place at the time of calendering between the rollers 103, 203, as a result of the compression of the strip 5 against the panel 1 and the simultaneous heating of the rollers to a temperature sufficient to cause partial fusion of the strip 5 of material consisting at least partially of fibres of thermoplastic material. According to an improvement, before it reaches the calender rollers 103, 203 the strip 5 comprising the thermoplastic fibres may be subjected to a pre-heating stage using heating means 6, for example those of the type comprising electrical resistance heaters or of the infrared type, or similar. The strip 5, consisting at least partially of fibres of thermoplastic material, may be applied to Woodstock panels 1 of any thickness. The strip 5 preferably consists of a felt, a fabric, a non-woven fabric, or similar, containing at least partially fibres of thermoplastic material. Preferably, the fibres of thermoplastic material are polypropylene-based, and are mixable with other materials, in any form, but particularly where 0% to 50% of the said materials is also in the form of fibres. The strip 5 of felt, fabric, or non-woven fabric may advantageously have a 70% to 80% content of polypropylene fibres and a 20% to 30% content of other types of fibres, such as viscose, polyester, polyamide, cotton, jute, or similar, or glass fibre. The weight of the strip 5 of fibres may. vary according to the specific applications from 30 to 1000 g/m 2 . The best relationship between the weight of the strip and the characteristics of the finished composite panel is obtained with fibre strips from 100 to 250 g/m 2 . The thicknesses of the strips may vary in direct proportion to the weight of the strip 5 from 0.3 to 1.0 mm, preferably from 1 to 3 mm. In this case, the temperatures of the calender rollers 103, 203 are between 75 and 150°C, and preferably from 85 to 100°C, for the first, upper roller, while for the second they lie within the range from 85 to 150°C, or preferably from 90 to 100°C. The pressures exerted by the calender rollers 103, 203 are between 50 and 150 bar, and preferably between 70 and 80 bar, for both the first and the second roller. A further improvement consists in the provision of a calender 3 consisting of three parallel calender rollers 103, 203, 303, rotating and aligned with each other vertically, and exerting specified pressures on the material which is made to pass between them. The additional lower calender roller 303 enables an additional strip 8 to be joined to the panel 1 on the opposite side to that to which the strip 5 containing the thermoplastic fibres is joined. This second strip 8 is taken from a reel 7 supported rotatably and parallel to the calender rollers 103 to 303 and disposed above the calender rollers 103 to 303, and on the other side of the calender 3 away from the extrusion aperture 2. The reel 7 is also mounted on a core consisting of braked expanding bars. The strip 8 may be a strip comprising fibres of thermoplastic material, or a felt, a fabric or a non-woven fabric of a type similar to the strip 5. Alternatively, the strip 8 may be a film of thermoplastic material, in particular polypropylene, which is applied to the panel 1 to improve the fixing of a coating, for example of fabric, felt, simulated leather, or similar, to the composite panel on the opposite side to the layer of plasticized fibrous thermoplastic material 5. In this case, the third calender roller 303 is also heated to a temperature between 85 and 120°C, preferably between 85 and 95°C, while a pressure of between 50 and 150 bar, and preferably between 70 and 80 bar, is exerted. Obviously, it is also possible, as an alternative to the configuration of the rollers 103, 203, 303 illustrated, to provide two pairs of rollers disposed in succession with respect to the direction of movement of the strip of material in the calender 3. Fig. 2 shows a variant embodiment of the device as shown in Fig. 1. In this case, the reel 4' of strip 5 of thermoplastic fibres and the reel 7' for the additional strip or polypropylene film 8 are disposed in a way symmetrically opposite that shown in Fig. 1 with respect to the calender 3. Additionally, whereas in the device as shown in Fig. 1 the strip 5 containing the thermoplastic fibres was applied to the panel 1 between the upper roller 103 and the intermediate roller 203 and the additional strip of thermoplastic fibres or polypropylene film 8 was applied between the intermediate roller 203 and the lower roller 303, in the example in Fig. 2 the said panel 1, the strip 5 of thermoplastic fibres and the strip or film 8 are fed together between the upper calender roller 103 and the intermediate one 203 and are therefore joined together at the time of this first calendering pass. As shown in Figs. 3 and 4, the strip 5 of felt, fabric, or non-woven fabric, comprising the thermoplastic fibres and initially having a considerable thickness, is compressed against the panel 1 at the time of calendering and is simultaneously heated to a temperature which causes the partial fusion of the thermoplastic fibres. Once calendered, the strip comprising the thermoplastic fibres is fixed to the Woodstock panel 1, forming a composite panel of thermoplastic material with one layer 1' of filled polypropylene and one similar layer 5' of plastic or plasticized material with a lesser thickness than that of the strip 5. This layer 5' has a smooth outer surface and partially retains, both aesthetically and structurally, the marks of the pattern or structure of the fibres of the strip 5. The two layers 1', 5' are fixed together by two different types of bond, namely a bond of the mechanical type due to the pressure exerted on the two panels, which causes interpenetration between the thermoplastic materials in their fused state and incorporation of the non-fused parts, in other words the non-fused fibres and fillers, so that, on cooling, the layers 1', 5' are fastened together; and a bond, due to the fact that part of the fused thermoplastic material, in particular the fused polypropylene component of one of the layers 1', is bonded with the fused thermoplastic material, or with the fused polypropylene of the other layer 5'.

Claims: Composite panel of plastic material, comprising at least one first layer (1') of polypropylene filled with sawdust and/or wood flour and/or wood shavings and at least one additional layer (5') consisting at least partially of fibrous thermoplastic material, characterised in that - a) this additional layer (5') is applied to one face of the first layer (1) by compression and simultaneous partial fusion of the fibrous thermoplastic material and of the first layer providing - b) a mechanical fixing of the two layers (1', 5') by interpenetration and incorporation of the non fused parts, in particular parts of fibre and/or filling - c) and fixing by bonding of part of the fused fibrous thermoplastic material and of the thermoplastic material of the first layer which is also fused - d) this additional layer (5') being after bonding similar to plastic material, with a substantially smooth surface which retains at least partially, whether for solely aesthetic or also for structural purposes, the fibrous pattern and/or structure - e) the two layer being bond together by two heated calender rollers (103, 203), the one of which (103) being in contact to the first layer (1'), being heated at a temperature between 75 and 150°C, preferably between 85 and 100°C - f) the second (203) of the said calender rollers being in contact to the additional layer (5'), being heated at a temperature of 85 to 150°C, preferably between 90 and 100°C; g) the two rollers exerting a pressure of compression of the two layers (1', 5') one against the other between 50 and 150 bar, preferably between 70 and 80 bar. Composite panel according to claim 1, characterised in that a further additional layer (8) comprising plasticized fibrous thermoplastic material, or a felt or a fabric or a non-woven fabric of the type similar to the additional layer (5) according to claim 1 is provided on the face of the first layer (1) opposite to the one bonded to the additional layer. Composite panel of plastic material according to Claim 1, characterized in that it consists of three layers, namely one intermediate first layer (1') and two outer layers (5') containing at least partially the fibrous thermoplastic material or a single outer layer (5') containing at least partially the fibrous thermoplastic material on one side of the first layer (1') and on the other side of this layer a layer consisting of a film of thermoplastic material (8) also applied by compression against the first layer (1) and simultaneous heating which may be applied only to the film (8). Composite panel of plastic material according to one or more of the preceding Claims 1 to 3, characterized in that the layer (5') containing the fibrous thermoplastic material consists partially of fibres of thermoplastic material in a proportion from 100% to 50% and preferably from 80% to 70%, and partially of other materials, particularly in the form of fibres, with a percentage content from 0% to 50%, preferably from 20% to 30%. Composite panel of plastic material according to Claim 4, characterized in that the non-thermoplastic material part consists of fibres of viscose, polyester, polyamide, cotton, jute, glass fibre or other synthetic or natural materials, while the fibres of thermoplastic material consist of polypropylene. Composite panel of plastic material according to one or more of the preceding claims, characterized in that the layer (5') comprising the fibrous thermoplastic material consists of: a felt of thermoplastic fibres, short or long, with random orientation; a fabric or non-woven fabric; or thermoplastic lattices or glass fibres; the said layer being compressed, and simultaneously heated to temperatures of partial or complete fusion of at least the fibrous thermoplastic material part and possibly of some or all of the other fibrous materials mixed with the first, against a panel (1) of filled polypropylene. Composite panel of plastic material according to Claim 6, characterized in that the strip (5) of felt, fabric or non-woven fabric has, before fixing to the panel (1), a weight between 30 and 1000 g/m 2 , preferably between 100 and 250 g/m 2 , and a thickness between 0.3 and 10 mm, preferably between 1 and 3 mm. Process for the fabrication of a composite panel of plastic material according to one or more of Claims 1 to 7 comprising a stage of extrusion of a panel (1) of filled polypropylene, a stage of superimposition of a layer (5) containing at least partially the fibrous thermoplastic material on the said panel (1), characterized by the subsequent compression of the two layers (1, 5) against each other, with the simultaneous heating of at least the layer (5) containing the fibres of thermoplastic material, and preferably of both the said layers (1, 5), to a temperature sufficient to ensure the partial fusion of at least the fibrous thermoplastic material and possibly of other components of the said layer (5) and the fixing of the two layers (1, 5) together by mechanical fixing, as a result of their interpenetration and the incorporation of their non-fused parts (1, 5), in particular of the non-fused fibres and fillers, and by fixing, as a result of the bonding of the fused thermoplastic components of the two layers (1, 5). Process according to Claim 8, characterized in that the stage of compression and heating of the layer containing the fibrous material against the layer of filled polypropylene are executed at the stage of calendering of a strip (1) of filled polypropylene by heated calender rollers (103, 203, 303), the additional layer containing the fibrous thermoplastic material being applied during the said stage of calendering of the filled polypropylene panel (1), by feeding a strip (5) containing fibrous thermoplastic material between the calender rollers (103, 203) at the same time as the panel (1) and in such a way that it is superimposed on the panel. Process according to Claim 9, characterized in that the strip (5) containing the fibrous thermoplastic material is subjected to a pre-heating stage (6) before it is fed to the calender (3). Process according to Claims 8 to 10, characterized in that the calender rollers (103, 203) for joining the strip (5) to the panel (1) are heated to a temperature between 75 and 150°C, and preferably from 85 to 100°C, for the first roller (103), and to a temperature between 85 and 150°C, or preferably from 90 to 100°C, for the second roller (203). Process according to Claim 11, characterized in that each of the calender rollers (103, 203) for the application of the strip (5) containing the fibres of thermoplastic material to the panel (1) exerts a pressure of between 50 and 150 bar, and preferably between 70 and 80 bar. Process according to one or more of the preceding Claims 8 to 12, characterized in that the additional second layer containing the fibrous thermoplastic material or the layer of polypropylene are applied to the free side of the layer (1') of filled polypropylene by superimposition on this layer and compression with simultaneous heating of a strip (8) containing at least partially the fibrous thermoplastic material, or of a film (8) of thermoplastic material. Device for the application of the method of fabrication according to Claims 8 to 13 of a composite panel of plastic material according to Claims 1 to 8, comprising: an extrusion head (2) for a panel (1) of thermoplastic material mixed with filler material, in particular polypropylene filled with sawdust and/or wood flour and/or wood shavings; a calender (3) with at least two calender rollers (103, 203) which can be heated and pressed against the panel (1) which is fed between them together with a strip (5) comprising fibrous thermoplastic material superimposed on the panel and unwound from a reel (4, 4') supported rotatably parallel to the rollers (103, 203) and interacting with means of braking the unwinding motion characterized in that means (6) of pre-heating the strip are provided before the calender (3) with respect to the direction of feeding of the strip (5, 8) to the calender.

Inventors: GENTILCORE EZIO, ODINO ADRIANO, GENTILCORE, EZIO, ODINO, ADRIANO
Applicants: GOR APPLIC SPECIALI SRL, G.O.R. APPLICAZIONI SPECIALI S.P.A.
Application year: 1995
Main classification: B32B31
IPC codes: B32B37, B32B21, B32B27, B32B3