CA1300331C

CA1300331C - Method of making panels, apparatus for carrying out the method and panels obtained thereby

Info

Publication number: CA1300331C
Application number: CA000538519A
Authority: CA
Inventors: Mario Miani
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-06-01
Filing date: 1987-06-01
Publication date: 1992-05-12
Anticipated expiration: 2009-05-12

Abstract

The invention relates to a method for making panels which may or may not be used for subsequent molding, to the apparatus for providing this method and to the panels obtained thereby. The method comprises the steps of forming a mixture of thermoplastic resin and organic filler and the plastication of this mixture performed simultaneously with its formation. During the transfer of the organic filler to the subsequent mixing and plastication step, the same is desiccated and mixed. Moreover, during said mixing and plastication step the plasticated mixture is transferred to a subsequent extrusion step. The method is carried out in an apparatus including a single device for the continuous production of a sheet of extruded material.

Description

1;10033i The present invention relates to a method for making panels, to the apparatus for providing this method and to the panels obtained thereby.
The panels whereto the present invention relates consist of essentially stratified flat structures with uniform thickness. These can be successively heat-molded after the step which provides their formation and can be used, indeed as panels to form finished items such as, for example, internal coverings of automotive vehicles.
The starting material for the preparation of these panels substantially consists of a thermoplastic resin and an organic filler. Conventional methods and the related devices for producing these panels entail a separate mixing step, wherein a certain amount of a thermoplastic resin is placed in close contact with the organic filler. The latter substantially consists of wood powder or sawdust, desiccated in a step previous to the mixing step, stored and then transferred to the subsequent processing steps (with problems of protecting the desiccated product from external humidity). In known methods and devices of the type at issue, the particles or fragments of organic filler must be sifted and selected, since they must have (due to processing requirements) controlled and uniform dimensions.
Furthermore, they must be added to the mix in amounts not exceeding 60X by weight, while it would be preferable to use greater amounts of this less expensive component. The aforementioned mixture is traditionally prepared in a turbo-mixer and the mixture thus obtained is subsequently q~

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transferred to a plastication and extruslon unit provided separately from the previous units. The material thus extruded is subsequently laminated. In traditional devices, lamination is performed in a device with rollers or cylinders, which sub~ects the layer of material in output from the extruder to a traction force. This force can in turn lead to discontinuities and irregularities on the surface of the flnished panel, or even lacerate the layer of extruded material.

The transfer of the desiccated organic filler to the mixing step and the transfer of the mixture to the plastication and extrusion unit is a problem of known devices and methods, as well as for the above described reasons, also due to the fact that they make the overall process longer and more troublesome, and increase the complexity of the apparatus by means of which this method is carried out.

The present invention provides a method to be obtained with a smaller number of steps with respect to known methods in a simpler and more rapid manner, and starting from organic filler fragments with non-uniform shape and size and with an initial humldlty content even higher than the values allowed by the prior art.

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1;~00331 The invention also provides panels usable for molding, the composite material whereof is less expensive with respect to traditional materials and anyway still lightweight.

The panels produced by the inventive process have a reduced specific weight due to the low-pressure mixing and compacting, contrary to panels obtained by prior art methods which cause a degradation and disintegration of the wood powder, caused by the high pressure used to melt the plastic material mixed with the wood powder. Panels with a specific weight of even 1.05 kg/dm3 can be produced.

According to one aspect of the present invention there is provided a method of making panels from an organic filler and a thermoplastic resin selected from a group consisting of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially providing an organic filler tank, bulk feeding said organic filler to said organic filler tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a metered quantity of organic fillér, moving said metered quantity of organic filler to a double screw extruder, counter rotating said double screw extruder thereby mixing said organic filler and conveying said organic filler along said extruder, heating said organic filler thereby substantially desiccating said organic filler, feeding a first charge of the thermoplastic resin into said organic filler, thereby lubricating said organic filler, degassing said organic filler, adding a second charge of thermoplastic resin to said organic filler and said first charge of ~ thermoplastic resin to form a mixture containing from over ; - 4 -~ 30033~

60% to 80~ by weight of organic filler and from under 40% to 20% by weight of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticized mixture, extruding said plasticated mixture to form an extruded - 5 plasticated mixture, and shaping said plasticized mixture to form panels.

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Thus according to the present invention there is provided a method of making panels from an organic filler and a thermoplastic resin selected from a group consisting of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially:
providing an organic filler tank, bulk feeding said inorganic filler to said organic filler tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a substantially metered quantity of organic filler, moving said metered quantity of organic filler to a double screw extruder, counter rotating said double screw extruder thereby mixing said organic filler and conveying said organic filler along said double screw extruder, heating said organic filler thereby substantially desiccating said organic filler, feeding a first charge of thermoplastic resin as a melt into said organic filler, to lubricate said organic filler, degassing said organic filler and said first charge of thermoplastic resin, adding a second charge of thermoplastic resin to said organic filler and said first charge of thermoplastic resin to form a mixture containing from over 60% to 80% by weight of organic filler and from under 40% to 20% by weight of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticated mixture, extruding said plasticated mixture to form an extruded plasticated mixture, forming from said extruded plasticated mixture a sheet having at least one side and at least one other side, applying a plastic material to said at least one side and to said at least one other side of said sheet to form a laminated composite, cooling said laminated composite, and cutting said laminated composite into panels.

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In another aspect thereof the present invention provides a method of making panels from an organlc filler and a thermoplastic resin selected from a group consistlng of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially;
providing an organic filler tank, bulk feeding sald inorganic flller to said organlc flller tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a metered quantity of organic filler, moving said substantially metered quantity of organic filler to a double screw extruder, counter rotating said double screw extruder thereby mixing said organic filler and conveying said organic filler along said double volute, heating said organic filler thereby substantially desiccating said organic filler, feeding a small amount of at least one first charge of thermoplastic resin as a melt into said organic filler to lubricate said organic filler, degassing said organic filler and said first charge of thermoplastic resin, adding at least one second charge of thermoplastic resin to said organic filler and said first charge of thermoplastic resin to form a mixture containing from over 60%
to 80% by weight of organic filler and from under 40% to 20% by welght of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticized mixture, extrudlng sald plasticated mixture to form an extruded plastlcated mlxture, formlng from said extruded plastlcated mlxture a sheet having at least one side and at least one other side, coollng sald sheet, cuttlng sald sheet into panels, and hot mouldlng said panels to form items having different shapes.

- 5a -The panels obtalned accordlng to the method and the apparatus described above are also ob~ect of the present invention and are substantially characterized in that they are provided with adapted protective coatings on their outer surface, as well as with a reinforcement material embedded in their thickness.

In fact, according to the present invention it has been surprisingly discovered that, startlng from a melted - 5b -thermoplastic resin and performing lts mlxlng wlth an organlc filler simultaneously with the plasticatlon step, it is possible to use more than 60% by welght of organic filler having even irregular starting size and dimensions. The organic flller mixing and desiccation step provided continuously in the same mixing, plastication and extrusion apparatus allows one to start from a still-humid organic filler but without the use of desiccation, storage and transfer unlts which are normally required in traditional devices this kind. The transfer of the material to the extrusion step, performed simultaneously with the mixing and plastication steps, also has the advantage of making the process according to the invention generally rapid and simple, and of making the apparatus according to the invention less expensive and complicated.

The invention is now described with reference to the figures of the accompanying drawings, which illustrate a preferred embodiment of the apparatus for making panels usable for re-molding, given only by way of non-limitative example of the lnvention, wherein:

figure 1 ls a longitudinal cross section view of the apparatus according to the invention;

figures 2 and 3 are transverse cross section detail views of the apparatus of figure l, respectively at its degassing region and at its resin feed region; and figure 4 is a perspective view in partial cross section of a panel usable for re-molding obtained with the apparatus of figure 1.

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The appara-tus according to the invention comprises a tank 1 provided at the bottom with a rotatable blade 2 and with a lateral opening 3. At the latter there is a vertical material transfer conduit 4 controlled by a screw feeder 5. The conduit 4 substantially connects the inner chamber of the tank 1 with the chamber of an extruder device 6 inside whlch is provided a double screw 7 with counterposed rotation. For the sake of ease and clarity of description, the double screw 7, which in use has screws arranged side-by-side on a horizontal plane ~see figures 2 and 3), is illustrated in figure 1 with the screws arranged on a vertical plane. The form, dimensions and pitch of the screw 7 vary along its length so as to treat the material being processed in a different manner according to its position inside the device 6. On the latter the resin feed sections 9 and 10 (figure 3) and the degassing sections 11 and 12 (figure 2) are also shown.
These sections are in particular provided with small channels 32, 33 respectively for the ingress of resin into the device 6 and for the discharge of the vapors from the latter. At the end of the device 6 opposite to the end 15 connected to the tank 1 there is an extrusion head 13 downstream whereof is provided a lamination device 14 which will be described in greater detail hereinafter.

The organic filler is fed inside the tank 1. The filler is composed of wood fragments (shavings, wood powder sawdust) still humid and with irregular slze and shape. It can be seen that neither the degree of humidity of the filler nor the dimensions or the possible aggregation between fragments are critical, so that it is possible to ~' .

bulk feed the wood fragments to the tank without having tc perform a prevlous sifting or a verification of its degree of humidity.

By virtue of its rotation, the blade 2 causes the advance of the wood fragments towards the lateral opening 3, from which they fall along the conduit 4 towards the inner chamber of the device 6; the screw feeder 5 substantially has the function of metering the amounts of organic filler discharged into the device 6. In the portion of the double screw 7 comprised between lo the section 15 for the inlet of the organic filler into the device 6 and the resin supply section lO, the wood fragments are sub~ected to the following treatment: they are heated by the heater plates 16 provided on the skirt of the device 6, they are mixed favoring thereby the formation of a uniform organic mass and facilitating the removal of humidity, and are finally conveyed towards the further processing steps. In this first portion of the device, there occurs substantial desiccation of the wood shavings so as to make the mass formed thereby homogeneous and uniform. This first portion also provides a section 9 for the inflow of a melted thermoplastic resin (polyethylene, polypropylene/ polyvinylchloride) having substantially the function of lubricating the organic filler mass, thereby facilitating its transfer into the device 6. The resin, which is in any case not indispensable in this step, is fed in very small amounts. The release of the vapors through the degassing section 11 also occurs in this first portion of the device 6.

The actual introduction of the thermoplastic resin into the device 6 occurs at the section 10. The thermoplastic resin is added in a melted state, and is substantially composed of polyethylene, polypropylene, polyvinylchloride alone or in mixture. In the portion of device 6 comprised between the resln inlet section lo and the section 17 immedlately upstream of the extrusion head 13, the following processes simultaneously occur:
formation of a mixture of organic filler and thermoplastic resin:
the amounts of the components fed to the device 6 being such that the mixture thus obtained contains from over 60~ to 80~ by weight of organic filler and from under 40% to 20~ by weight of thermoplastic resin with respect to the overall weight of the mixture; plastication of the mixture as it forms; also in this portion of the device 6, heater plates 16 are in fact provided, which soften the mixture; transfer of the plasticated mixture to the subsequent extrusion step.

A degassing section 12 is also provided in this portion of device 6 comprised between the above described sections 10 and 17.

The plasticated mass, again under the action of the double screw 7, is extruded through the head 13 as a sheet like paste material 18. The lamination device 14 comprises a calender, the rollers 19, 20 whereof are arranged below the extrusion head 13 so as to receive the material 18, paste-like and not very consistent, mainly by gravity feed. Indeed the material forms a small accumulation 21 on the calender which contributes to make the thickness of the ~3003~1 -- 10 _ layer of material more uniform and regular. Also, by acting on the distance and on the speed of the cylinders it is possible to achieve the accurate control of the dimensions of the sheet produced. The latter is covered on one side by a film of plastic material 29 of the same type as the material introduced into the device 6 at the film head 22, further laminated between the rollers 20 and 23, coated on the opposite side with another film of plastic material 24 (the same or different to the previous material) applied by means of the film head 25, further covered with a finishing material 31 (fabric, aluminum, etc.) and again laminated between the rollers 23 and 26. The stratified laminated material 27 at the output of the apparatus 14 is subsequently cooled and cut into panels 28 (figure 4).
A reinforcement 34 (figure l), consisting, for example, of a metal net embedded into the thickness of the material 18, can be included in the layer 18 of extruded material originating from the head 13.
The panel 28 thus obtained can be further hot-molded to form items having different shapes, such as for example the dashboard and the other inner parts of the passenger compartment of automotive vehicles, packaging material, such as continuously heat-formed fruit-boxes and the like.
Naturally, the invention as described and illustrated above is susceptible to further modifications and variations without thereby abandoning the present scope of protection.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of making panels from an organic filler and a thermoplastic resin selected from a group consisting of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially providing an organic filler tank, bulk feeding said organic filler to said organic filler tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a metered quantity of organic filler, moving said metered quantity of organic filler to a double screw extruder, counter rotating said double screw extruder thereby mixing said organic filler and conveying said organic filler along said extruder, heating said organic filler thereby substantially desiccating said organic filler, feeding at least one first charge of thermoplastic resin into said organic filler, thereby lubricating said organic filler , degassing said organic filler, adding a second charge of thermoplastic resin to said organic filler and said first charge of thermoplastic resin to form a mixture containing from over 60% to 80% by weight of organic filler and from under 40% to 20% by weight of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticized mixture, extruding said plasticated mixture to form an extruded plasticated mixture, and shaping said plasticized mixture to form panels.

2. A method according to claim 1, further comprising an intermediate step of embedding at least one reinforcement element in said extruded plasticized mixture.

3. A method according to claim 1, further comprising steps of; forming from said extruded plasticated mixture a sheet having at least one side and at least one other side applying a plastic material to said at least one side of said extruded sheet to form a laminated component, cooling said laminates composite, and cutting said laminated composite into panels.

4. A method according to claim 1, further comprising the steps of; forming from said extruded plasticated mixture a sheet having at least one side and at least one other side, applying a plastic material to said at least one side and to said at least one other side of said extruded sheet, to form a laminated composite, cooling said laminated composite and cutting said laminated composite into panels.

5. A method according to claim 1, further comprising the steps of; embedding at least one reinforcement element in said extruded plasticized mixture, forming from said extruded plasticated mixture a sheet having at least one side and at least one other side, applying a plastic material to said at least one side and to said at least one other side of said sheet to form a laminated composite, cooling said laminated composite and cutting said laminated composite into panels.

6. A method according to claim 5, further comprising the step of applying a finishing material to said plastic material applied to said at least one side of said sheet.

7. A method according to claim 6, wherein said finishing material is aluminum.

8. A method according to claim 6, wherein said finishing material is a fabric.

9. A method according to claim 1, further comprising the step of hot moulding said panels thereby forming items having different shapes.

10. A method of making panels from an organic filler and a thermoplastic resin selected from a group consisting of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially;
providing an organic filler tank, bulk feeding said organic filler to said organic filler tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a substantially metered quantity of organic filler, moving said metered quantity of organic filler to a double screw extruder counter rotating said double screw, extruder thereby mixing said organic filler and conveying said organic filler along said double screw extruder, heating said organic filler thereby substantially desiccating said organic filler, feeding a first charge of thermoplastic resin as a melt into said organic filler, to lubricate said organic filler, degassing said organic filler and said first charge of thermoplastic resin, adding a second charge of thermoplastic resin to said organic filler and said first charge of thermoplastic resin to form a mixture containing from over 60% to 80% by weight of organic filler and from under 40% to 20% by weight of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticated mixture, extruding said plasticated mixture to form an extruded plasticated mixture, forming from said extruded plasticated mixture a sheet having at least one side and at least one other side, applying a plastic material to said at least one side and to said at least one other side of said sheet to form a laminated composite, cooling said laminated composite, and cutting said laminated composite into panels.

11. A method according to claim 10, further comprising the step of applying a finishing material to said plastic material applied to said at least one side of said laminated composite.

12. A method according to claim 10, further comprising the step of hot moulding said panels.

13. A method according to claim 11, wherein said finishing material is aluminum.

14. A method according to claim 11, wherein said finishing material is a fabric.

15. A method according to claim 10, further comprising the intermediate step of embedding at least one reinforcement element in said extruded plasticized mixture.

16. A method of making panels from an organic filler and a thermoplastic resin selected from a group consisting of polyethylene, polypropylene and polyvinylchloride, alone or in mixture, said method comprising the steps of sequentially; providing an organic filler tank, bulk feeding said inorganic filler to said organic filler tank, moving at least some of said organic filler from said organic filler tank, metering a quantity of said organic filler moved from said organic filler tank to provide a metered guantity of organic filler, moving said substantially metered quantity of organic filler to a double screw extruder, counter rotating said double screw extruder thereby mixing said organic filler and conveying said organic filler along said double screw extruder, heating said organic filler thereby substantially desiccating said organic filler, feeding a first charge of thermoplastic resin as a melt into said organic filler to lubricate said organic filler, degassing said organic filler and said first charge of thermoplastic resin, adding a second charge of thermoplastic resin to said organic filler and said first charge of thermoplastic resin to form a mixture containing from over 60% to 80% by weight of organic filler and from under 40% to 20% by weight of thermoplastic resin, degassing said mixture, plasticizing said mixture to form a plasticized mixture, extruding said plasticated mixture to form an extruded plasticated mixture, forming from said extruded plasticated mixture a sheet having at least one side and at least one other side, cooling said sheet, cutting said sheet into panels, and hot moulding said panels to form items having different shapes.

17. A method according to claim 16, further comprising the intermediate steps of; embedding at least one reinforcement element in said extruded plasticized mixture, applying a plastic material to said at least one side and to said at least one other side of said sheet to form a laminated composite, applying a finishing material to said plastic material applied to said at least one side of said laminated composite.

18. A method according to claim 16, wherein said finishing material is aluminum.

19. A method according to claim 16, wherein said finishing material is a fabric.

20. A method according to any one of claims 1 to 9, wherein the first charge of thermoplastic resin is fed as a melt in a small amount to the organic filler prior to introduction of said second charge to lubricate the organic filler as it passes through the extruder.