WO1990003256A1

WO1990003256A1 - Method and device for producing rigid products with high surface finish, especially plastic mouldings

Info

Publication number: WO1990003256A1
Application number: PCT/SE1989/000451
Authority: WO
Inventors: Axel Kaufmann
Original assignee: Molybon Agenturer Aktiebolag
Priority date: 1988-09-20
Filing date: 1989-08-29
Publication date: 1990-04-05
Also published as: SE463548B; SE8803322L; SE8803322D0

Abstract

In a method for producing rigid plastic products comprising a thermoformed, fibre-reinforced backing material (10) and an outer layer of a thermoformed, flexible film or foil sheet material (6), the two materials are preheated and thereafter brought together in a compression and moulding tool (1), where they are compression moulded and given their final shape. The method is a one-step method with work cycle times of about 40-60 s. The end product is given a very high surface finish, and there is no need for any complementary work. Furthermore, no solvents are required. A device for carrying the method into effect comprises, apart from the above-mentioned compression and moulding tool (1), feeding means (5, 7) and a preheating oven (8) for the film or foil sheet (6), as well as a feeding means (11) and a preheating oven (9) for the backing (10). In the moulding and compression tool (1), vacuum moulding and compression moulding are combined in one step of operation.

Description

METHOD AND DEVICE FOR PRODUCING RIGID PRODUCTS WITH HIGH SURFACE FINISH, ESPECIALLY PLASTIC MOULDINGS

The present invention relates to a method for producing in one step such rigid products as vehicle body parts, mouldings for liner panels in vehicles, especially- plastic mouldings, and similar articles comprising a layer of a thermoformed fibre-reinforced backing material and, on at least one side thereof, an outer layer of a thermo¬ formed flexible film or foil material with high surface, finish on the surface facing away from the backing material, the two materials being preheated and thereafter brought together and adhered to one another to form said product.

The invention also relates to a device for producing such products.

In the plastic industry, and perhaps above all in the car manufacturing industry, continuous efforts are being made in order to develop new, strong and inexpensive construction materials based on plastic. It is a well- known fact that the number of plastic components in a car has increased considerably during the last few years, while the number of metal components has been reduced correspondingly, the reason therefor being that the plastic materials have proved to be less expensive to manufacture, as well as lighter, thus making it possible to reduce the total weight of the car, especially if large body parts, such as the engine bonnet or the wings, are manufactured in plastic.

To possess sufficient strength, such plastic products have to be reinforced by some kind of fibre reinforcement. A much-liked backing material for that purpose is the so- called GMT material (GlasrnattenverstSrkte Thermoplast- platten) which consists of thermoplastic, usually polypropylene, reinforced by 20-40% glass fibres. A material of this type and a method for the production thereof is described in, for instance, US-A-4,568,581.

The comparatively inexpensive GMT material usually has the form of relatively rigid plates which, before the moulding, are heated to about 200° and then compression moulded in a hydraulic press, the work cycle times for the compression being about 20-60 s, depending on the desired thickness of the product. However, the fibre reinforcement of these backing materials produces visible irregularities in the surface of the moulded product whose surface finish will be unacceptable. Complementary work, such as the application of a primer, patching, sanding, and lacque¬ ring, is therefore necessary. It is not uncommon that a so-called activating primer is applied to the backing material, a soft foil sheet being thereafter applied to said primer in order to produce the desired final finish. In that case, the backing material always has to be pre- moulded.

Another much-liked backing material which can be used for producing the products at issue, is the so-called SMC material (Sheet Moulding Compound) which usually has the form of polyester prepregs with glass fibre reinforcement. SMC products are also compression moulded and have to be worked after shaping in order to obtain a high surface finish. The use of SMC material for producing the products in question is described in, for example, US-A-4,612,149. What these two backing materials and the methods used for producing products based on said materials have in common, is that a number of different operations have to be carried out in different steps, including e.g. pre- • forming, intermediate storage, cooling, compression moulding, patching, sanding and lacquering, and that solvents have to be used in the complementary work, i.e. the application of a primer and a lacquer. Naturally, this involves obvious disadvantages, such as long total work cycle times, as well as costly complementary work. As mentioned above, these two backing materials are moulded by means of compression moulding in a press with two mould halves. After preheating, the materials are positioned in the cavity of the female mould, whereupon the male mould is slammed down into the cavity to effect the compression moulding. Then, the male mould is retracted and the moulded product is removed from the female mould, for instance by means of an ejector. The glass fibre content of the backing material gives the product an unattractive surface which has to be worked to a high surface finish.

Another method used for producing plastic products is vacuum moulding, which means that a thermoplastic film or foil sheet is heated and then sucked into the cavity of a female mould provided with vacuum conduits connected to a vacuum source. On condition that the mould itself has a high finish, the shaped product also obtains a high surface finish, termed class A in technical language. However, vacuum moulding of the above-mentioned GMT and SMC backing materials is extremely difficult because of their structure and fibre content.

One object of the present invention is to provide a method for producing such rigid products as mentioned above which comprise a fibre-reinforced backing material, but which nevertheless have a high surface finish, type class A.

Another object of the invention is that the produc¬ tion should comprise only one step of operation with far shorter total work cycle times than possible thus far. A further object of the invention is that the pro¬ duction should be carried out wholly without solvents.

Furthermore, the invention aims at providing a device for producing rigid products of the above-mentioned type in one step of operation using uncomplicated equipment. The invention therefore provides a method and a device in which compression moulding and vacuum moulding have been combined to manufacture products with a fibre- reinforced backing material for which a film or foil sheet material has been applied which has a high surface finish.

The method provided is of the type described by way of introduction and is characterised in that the film or foil sheet material is fed into a female mould with a cavity and is sucked against the walls of said cavity for moulding of its surface finish side in contact with said walls; that the backing material, at the same time or shortly thereafter, is fed into the female mould and positioned on top of the said sheet material; that a male mould is subsequently inserted in the cavity of the female mould so that said backing material and said sheet material are compression moulded and given their final shape; and that the male mould is finally retracted from the female mould and the finished product is removed therefrom to cool.

In accordance therewith, there is also provided a device for producing in one step such rigid products as vehicle body parts, mouldings for liner panels in vehicles, especially plastic mouldings, and similar articles comprising a layer of a thermoformed, fibre- reinforced backing material and, on at least one side thereof, an outer layer of a thermoformed, flexible film or foil sheet material with high surface finish on the side facing away from the backing material, said device comprising means for preheating said sheet material and said backing material, respectively, and means for feeding said sheet material and said backing material into .a means for shaping and compression moulding of the two materials to form said product. The device is characterised in that the moulding and compression means comprises a female mould with a cavity into which a male mould can be moved for compression moulding and shaping, the male mould having a shape which substantially coresponds to the shape of the cavity; and that the female mould comprises conduits opening into the cavity and connected to a vacuum source for sucking and moulding said sheet material against the walls of the cavity before activation of the male mould for compression moulding of the two materials within said cavity.

Further characteristics of the present invention are stated in the appended subclaims.

The invention will now be described in more detail below, reference being had to the accompanying schematic drawing of a device for carrying the method according to the invention into effect. In the drawing, a moulding and compression means is generally designated 1 and comprises a stationary female mould 2 with a cavity 3, and a male mould in the form of a vertically movable plunger 4, the shape of which corre¬ sponds to the shape of the cavity 3. Both the plunger and the cavity have satisfactory surface smoothness.

To the left in the drawing, there is shown a film or foil sheet 6 rolled on a roll 5 and consisting of a flexible thermoformed plastic material, in this embodiment ABS. The sheet 6 which is preferably about 0.15-0.40 mm thick, is fed by means of a roller gear 7 into the mould¬ ing and compression means 1 via a preheating oven 8 with a temperature of about 190°C.

To the right in the drawing, there is shown another preheating oven 9 with a temperature of about 240°C, the backing material in the form of plates 10 being heated and plasticised in said oven before it is fed into the mould¬ ing and compression means 1 by a pick-up robot 11.

The feeding may also be carried out manually or by other mechanical means. Before heating, the plates 10 are comparatively rigid and preferably have a thickness of about 3-4 mm. They consist of a thermoformed glass fibre- reinforced material which in this embodiment is made up of GMT as referred to in the introduction.

The device is intended for the production of such rigid plastic products as vehicle body parts, mouldings for liner panels in vehicles, and similar articles. In these forms, the end product should comprise a layer of a backing material, i.e. compression moulded GMT plates 10, and a film or foil sheet layer 6 applied and adhered thereto, said sheet layer, after shaping and compression moulding, having a class A finish on the surface facing away from the backing material.

The production according to the invention of plastic products is carried out as follows.

The plastic sheet 6 is heated in the preheating oven 8 and fed into the moulding and compression means 1 by means of the roll gear 7 and, optionally, further feeding means ( ot shown). The feeding is such that the sheet 6 is positioned over the cavity to cover it (dash-dot line), whereupon a clamping frame 12 is applied against the upper side of the female mould 2 so that the sheet 6 is fixed round the cavity 3. Thus, the clamping frame 12 is positioned circumferentially round and somewhat outside the cavity 3.

When the sheet 6 has been fastened in this manner, a vacuum pump 13 is activated to give a suction effect via the vacuum conduits 14 disposed in the female mould 2 and opening into the cavity 3. Thus, the sheet 6 is pulled down and firmly sucked against the walls 15 of the cavity 3, the finish side of the sheet facing the cavity walls. For the sake of clarity, only two vacuum conduits 14 are shown, but anyone skilled in the art realises that there has to be a number of such conduits to exert a sufficient suction effect on the sheet 6.

At the same time or shortly afterwards, preferably a second or so thereafter, the backing material, i.e. the- GMT plates 10, which has been heated in the preheating oven 9, is fed into the cavity 3 of the moulding and compression means 1 and positioned on top of the plastic film or foil sheet 6 firmly held therein by suction. Subsequently, the plunger 4 is slammed down into the cavity 3 and the hot GMT plates 10 and the hot sheet 6 are pressed together so that the product is given the shape defined by the shapes of the cavity 3 and the plunger 4. It should be pointed out that the plunger 4 comprises venting ducts 16 through which the air in the cavity 3 is evacuated when the plunger 4 is slammed down.

After the shaping and compression moulding in the moulding and compression means 1, the plunger 4 is retracted from the cavity 3, whereupon the clamping frame 12 is removed from the female mould 2. The vacuum pump 13 is switched off and the finished product is removed manually or by means of a pick-up robot or the like (not shown) from the cavity 3. Finally, the product is taken to a suitable place for cooling. In order to start a another work cycle, a new sheet 6 is advanced to cover the cavity 3, and the procedure is repeated.

The plunger 4 and the female mould 2 are preferably provided with cooling ducts 17 and 18, respectively, in which a cooling agent is circulated to impart to these two main components of the moulding and compression means 1 a temperature clearly below the above-mentioned preheating temperatures, preferably about 20-40°C. Furthermore, the plunger 4 preferably is provided with means 19 for punch¬ ing out a desired portion of the sheet 6 when the plunger 4 is slammed down into the cavity 3.

In short, the invention can be said to reside in a combination of compression moulding and vacuum moulding in one step and in one and the same machine. Therefore, it is possible to obtain very short, total work cycle times, while maintaining a satisfactory quality of the end product, as well as a high surface finish. Practical tests using GMT as a backing material have shown that total work cycle times of but 40-60 s can be obtained. This should be compared with prior art methods comprising several steps of operation, e.g. preforming, intermediate storage, compression moulding, application of a primer, patching and sanding etc, with total work cycle times ranging up to a few minutes. Thus, considerable savings in time and money are achieved by means of the present invention. It should also be pointed out that the invention by no means is restricted to the embodiment described above, and that several modifications of the invention are conceivable within the scope of the inventive idea as defined in the appended claims.

Naturally, the invention can be applied to other materials than those mentioned by way of example in this description. Many other plastic materials can serve as backing material or sheet material, and if desired, sheet material can be applied to both sides of the backing material. In certain conditions, it is possible, in a manner equivalent to what has been described above, to apply a nonplastic sheet material, e.g. a knitted fabric material. However, it must be possible to adhere such a material by suction to the walls of the mould cavity and to fix it to the backing material when compression moulding takes place. In that case, the main object is not to obtain a high surface finish, but to produce a rigid product in one step and without the use of solvents. Finally, it should be pointed out that the peripheral equipment employed, i.e. the preheating ovens, the feeding means etc, may be of a different type. The feeding of the GMT plates may, in some cases, be carried out manually and, moreover, the removal of the end product from the cavity may be carried out by means of a further pick-up robot (not shown).

Claims

1. Method for producing in one step such rigid products as vehicle body parts, mouldings for liner panels in vehicles, especially plastic mouldings, and similar articles comprising a layer of a thermoformed fibre- reinforced backing material (10) and, on at least one side thereof, an outer layer of a thermoformed flexible film or foil sheet material (6) with high surface finish on the surface facing away from the backing material (10), the two materials (6, 10) being preheated and thereafter brought together and adhered to one another to form said product, c h a r a c t e r i s e d in that the foil or film sheet material (6) is fed into a female mould (2) with a cavity (3), and is sucked against the walls (15) of said cavity for moulding of its surface finish side in contact with said mould walls (15); that the backing material (10), at the same time or shortly thereafter, is fed into the female mould (2) and positioned on top of said sheet material (6); that a male mould (4) is subsequently inserted in the cavity (3) of the female mould (2) so that said backing material (10) and said sheet material (6) are compression moulded and shaped; and that the male mould (4) is finally removed from the female mould (2) and the finished product is removed therefrom to cool.

2. Method as claimed in claim 1, c h a r a c t e r ¬ i s e d in that the sheet material (6) is firmly held . against the walls of the cavity (3) by suction applied via conduits (14) opening into the cavity and connected to a vacuum source (13).

3. Method as claimed in claim 1 or 2, c h a r a c ¬ t e r i s e d in that the female and male moulds (2, 4) are cooled to a temperature clearly below the preheating temperature of the two materials (6, 10).

4. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the air in the cavity (3) is evacuated via venting ducts (16) in the male mould (4) when this enters the cavity (3) of the female mould (2).

5. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that a clamping frame (12) is applied against, the female mould (2) to fix the sheet material (6) thereto before suction is applied to the cavity (3), and that a desired portion of the sheet material (6) is punched out during compression moulding by punching means (19) provided on the male mould (4).

6. Device for producing in one step such rigid products as vehicle body parts, mouldings for liner panels in vehicles, especially plastic mouldings, and similar articles comprising a layer of a thermoformed fibre- reinforced backing material (10) and, on at least one side thereof, an outer layer of a thermoformed flexible film or foil sheet material (6) with high surface finish on the side facing away from the backing material (10), said device comprising means (8; 9) for preheating said sheet material (6) and said backing material (10), respectively, and means (5, 7; 11) for feeding said sheet material (6) and said backing material (10) into a means (1) for shaping and compression moulding of the two materials (6, 10) to form said product, c h a r a c t e r i s e d in that the moulding and compression means (1) comprises a female mould (2) with a cavity (3) into which a male mould (4) can be moved for compression moulding and shaping, the male mould (4) having a shape which substantially corresponds to the shape of the cavity (3); and that the female mould (2) comprises conduits (14) opening into the cavity (3) and connected to a vacuum source (13) for sucking and moulding said sheet material (6) against the walls (15) of the cavity (3) before activation of the male mould (4) for compression moulding of the two materials (6, 10) within said cavity (3).

7. Device as claimed in claim 6, c h a r a c t e r ¬ i s e d in that the female and male moulds (2, 4) comprise cooling ducts (18; 17) for cooling to a temperature clearly below the preheating temperature of the two materials (6, 10).

8. Device as claimed in claim 6 or 7, c h a r a c ¬ t e r i s e d in that the male mould (4) comprises venting ducts (16) for evacuation of the air in the cavity (3), during shaping and compression moulding.

9. Device as claimed in any one of claims 6-8, c h a r a c t e r i s e d in that the moulding and compression means (1) also comprises a clamping frame (12) applicable against the female mould (2) for fixing the sheet material (6) before suction is applied to the cavity (3), and means (19) for punching out the desired portion of said sheet material (6) during shaping and compression moulding.

10. Device as claimed in any one of claims 6-9, c h a r a c t e r i s e d in that the sheet material (6) is band-shaped and rolled on a roll means (5) from which the sheet material (6) can be fed into the moulding and compression means (1) via the preheating means, and that the backing material is in the form of separate, compara¬ tively rigid plates (10) insertable piece by piece in the moulding and compression means (1) via the preheating means.