GB2316644A

GB2316644A - Moulding into a plastics shell with enhanced bonding

Info

Publication number: GB2316644A
Application number: GB9617964A
Authority: GB
Inventors: Robert Jankel
Original assignee: R J DESIGNRIGHTS Ltd
Current assignee: R J DESIGNRIGHTS Ltd
Priority date: 1996-08-28
Filing date: 1996-08-28
Publication date: 1998-03-04
Anticipated expiration: 2016-08-28
Also published as: GB2316644B; GB9617964D0

Abstract

The invention relates to a plastics article and to a method of manufacture thereof, particularly but not exclusively to panels manufactured from plastics materials. The invention provides a method of manufacturing a plastics article comprising the steps of: a) forming a plastics shell (8) having a cavity (10); b) attaching a particulate or granular material (14) to an interior wall (12) of the cavity (10) so as to provide a coated surface susceptible to the ingress of a plastics strengthening material in an injectable state; c) applying the plastics strengthening material in an injectable state to the coated surface by introducing the strengthening material into the cavity (10) of the plastics shell (8); and d) providing for the transformation of the plastics strengthening material from the injectable state to a strengthening state such that the strengthening material is rigidly attached to the plastics shell (8) and provides the plastics shell (8) with support. The invention has the advantage over the prior art of providing a plastics article having increased rigidity and structural strength.

Description

A Plastics Article and Method of Manufacture Thereof The invention relates to a plastics article and to a method of manufacture thereof, particularly but not exclusively to panels manufactured from plastics materials.

It is well known that plastics materials can be used to manufacture articles such as motor vehicle body panels. This type of panel may be manufactured from a single sheet of plastics material to form a single skinned panel or, if greater rigidity is required, from two or more sheets of plastics material which are shaped and joined so as to form a double skinned panel or shell having a cavity. Reinforcement means such as a foam filling can be located within the cavity to provide a panel which is both light and strong.

A known method of manufacturing plastics panels having reinforcement means located within a cavity involves generating a dense plastics strengthening material by misting and reacting within the cavity two reactants whose initial reaction product is a fluid or foam having a volume greater than that of the reactants. When the two reactants are reacted within an enclosed cavity, the initial product of their reaction pushes against the interior walls of the cavity. The aforementioned method makes use of an extremely strong, two sided fixture for preventing the cavity walls from deforming. The volume of the reaction is thereby kept constant resulting in very high temperatures and internal fluid or foam pressures. The initial reaction product solidifies as it cools to give a final rigid product. Due to the high internal pressures of the initial liquid product, the solidified final product is a very dense plastics strengthening material. An example of a product which can be used in such a method is Baymer TP PU 1319 G/3 manufactured by Bayer AG.

One problem with the above method is that the fluid or foam product does not adhere very well to the interior walls of the cavity as it cools. The plastics strengthening material of the final product is not therefore adequately secured to the plastics shell. This greatly reduces the forces that can be transmitted between the plastics shell and the plastics strengthening material and reduces the overall rigidity and structural integrity of the plastics panel manufactured.

It is an object of the present invention to provide a method of manufacturing a plastics article having increased rigidity and structural integrity.

It is a further object of the present invention to provide a method of manufacturing a plastics article in which a plastics strengthening material is rigidly attached to the interior wall of a plastics shell.

The invention provides a method of manufacturing a plastics article comprising the steps of: a) forming a plastics shell having a cavity; b) attaching a particulate or granular material to an interior wall of the cavity so as to provide a coated surface susceptible to the ingress of a plastics strengthening material in an injectable state; c) applying the plastics strengthening material in an injectable state to the coated surface by introducing the strengthening material into the cavity of the plastics shell; and d) providing for the transformation of the plastics strengthening material from the injectable state to a strengthening state such that the strengthening material is rigidly attached to the plastics shell and provides the plastics shell with support.

The invention further provides a method of manufacturing a plastics article wherein the particulate or granular material is flock.

The invention further provides a method of manufacturing a plastics article wherein a bracing member is located in the cavity.

The invention further provides a method of manufacturing a plastics article wherein the bracing member is enclosed by the plastics strengthening material.

The invention further provides a method of manufacturing a plastics article wherein the bracing member comprises protrusions for enhancing the fixing thereof to the plastics reinforcement.

The invention also provides a plastics article manufactured in accordance with method of the present invention.

The method of the present invention has the advantage over the relevant prior art of providing means for rigidly securing a plastics strengthening material to the interior walls of a plastics shell. The plastics strengthening material and the plastics shell are thereby fixed relative to one another allowing forces to be effectively transmitted therebetween. The plastics articles produced by this method have a greater rigidity and structural integrity than those produced by the aforementioned prior art method.

A method according to the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of the plastics shell of a plastics article according to the invention prior to assembly; Figure 2 is a cross-sectional view of the plastics shell of Figure 1 prepared for assembly; Figure 3 is a cross-sectional view of a plastics article according to the invention prior to the transformation of the plastics strengthening material from the injectable state to a strengthening state; and Figure 4 is a cross-sectional view of a plastics article according to the invention.

Figure 1 shows an upper member 2 and a lower member 4 of a plastics panel.

The members 2,4 are made from Bayblend PC (Polycarbonate) and are manufactured using conventional vacuum forming techniques. Alternative plastics materials and production techniques such as injection moulding can be used as appropriate. The upper member 2 and lower member 4 are manufactured so as to incorporate mating surfaces 6. The mating surfaces 6 allow the members 2,4 to be located and fixed adjacent one another to form a plastics shell 8 having a cavity 10 (see Figure 3).

Figure 2 shows the members 2,4 immediately before they are located and fixed adjacent one another to produce the plastics shell 8. Prior to the assembly of the plastics shell 8, a particulate material in the form of flock is attached to the interior walls 12 of the members 2,4 using conventional adhesives. The adhesive and flock are preferably sprayed onto the interior walls 12, the adhesive being applied prior to the flock. A flock coating 14 is thereby formed on the members 2,4. The flock material is not attached to the mating surfaces 6 to ensure that the joining of the members 2,4 is not unnecessarily hindered A bracing member 16 is also provided between the members 2,4 prior to the assembly of the plastics shell 8. The bracing member 16 is made from a metallic material and manufactured using conventional extrusion, milling or rolling techniques. However, alternative materials and production techniques may be used as appropriate. The bracing member 16 is an elongate beam having a substantially rectangular cross-section. Two serrated protrusions 18 project from two opposite sides of the bracing member 16 and extend along the full length of the bracing member 16.

The bracing member 16 may be held in the required position prior to assembly by support members (not shown) moulded into the lower member 4.

Once the flock coating 14 has been attached to the interior walls 12 and the bracing member 16 has been located in the required position, the members 2,4 are joined to one another at the mating surfaces 6. The members 2,4 are joined using plastic welding techniques, adhesives or other suitable attachment means to provide a seal 22. The design of the members 2,4 is such that the seal 22 is unbroken. The location of the upper member 2 adjacent the lower member 4 thereby provides the enclosed cavity 10.

A plastics strengthening material such as Baymer TP PU 1319 G/3 is then introduced in liquid form into the cavity 10 through the plastics shell 8 or seal 22.

Figure 3 shows that the material is provided in sufficient quantity to fill the cavity 10 and caused to react to form a fluid or foam product 24. The fluid or foam product 24 of the reaction has a greater volume than that of the reactants and pushes against the interior walls 12 forming the cavity 10. The exterior walls 26 of the members 2,4 are enclosed and supported by extremely strong, two sided supporting means (not shown) to prevent them from moving apart or becoming distorted. As the fluid or foam product 24 presses against the interior walls 12, the fluid or foam product 24 infiltrates and surrounds the fibres of the flock coating 14 under high internal pressure. The serrated protrusions 18 of the bracing member 16 are also surrounded by the fluid or foam product 24.

When the product of the reaction cools and cures, the fluid or foam product 24 changes to a solid state to form a fmal solid product 28 in the form of a high density foam (see Figure 4). The fibres of the flock coating 14 become bonded to the solid product 28 and the serrated protrusions 18 provide a firm attachment of the solid product 28 to the bracing member 16. Once the strengthening material has solidified, the means for supporting the exterior walls 26 are removed and the manufacture of the plastics panel is complete.

Approximate timings for the use of the plastics strengthening material are as follows: Mixing time approx 10s Cream time 35 - 45s Curingtime 150- 180s A density of between 30 and 40kg/m3 can be achieved.

Figure 4 shows a cross-sectional view of a plastics panel manufactured in accordance with the method described above. The plastics panel comprises a plastics shell 8 incorporating an upper member 2 and lower member 4 joined at mating surfaces 6 to form a completely enclosed cavity 10. The members 2,4 are made from Bayblend PC (Polycarbonate). The interior walls 12 of the members 2,4 are provided with a particulate material in the form of flock coating 14. A bracing member 16 in the form of an elongate beam having a substantially rectangular cross-section is located substantially centrally within the cavity 10. The bracing member 16 is made from a metallic material and incorporates two serrated protrusions 18 located on two opposite sides. The cavity 10 contains a solid foamed plastics strengthening material 28 which infiltrates and bonds to the flock coating 14. A rigid connection is thereby provided between the plastics shell 8 and the plastics strengthening material 28. The plastics strengthening material 28 also surrounds the bracing member 16 and is rigidly attached thereto by means of the two serrated protrusions 18.

The present invention is not limited to the specific method or embodiment described above. Alternative arrangements and suitable materials will be apparent to a reader skilled in the art. For example, the plastics shell 8 and the bracing member 16 may take an alternative shape or alternative but appropriate materials may be used.

Claims

1. A method of manufacturing a plastics article comprising the steps of: a) forming a plastics shell having a cavity; b) attaching a particulate or granular material to an interior wall of the cavity so as to provide a coated surface susceptible to the ingress of a plastics strengthening material in an injectable state; c) applying the plastics strengthening material in an injectable state to the coated surface by introducing the strengthening material into the cavity of the plastics shell; and d) providing for the transformation of the plastics strengthening material from the injectable state to a strengthening state such that the strengthening material is rigidly attached to the plastics shell and provides the plastics shell with support.

2. A method of manufacturing a plastics article as claimed in claim 1, wherein the plastics shell is formed using vacuum forming or injection moulding techniques.

3. A method of manufacturing a plastics article as claimed in any one of the preceding claims, wherein the particulate or granular material is flock.

4. A method of manufacturing a plastics article as claimed in any one of the preceding claims, wherein an adhesive is used to attach the particulate or granular material to the interior wall of the cavity.

5. A method of manufacturing a plastics article as claimed in any one of the preceding claims, wherein the plastics shell is rigidly held during the transformation step so as to prevent deformation.

6. A method of manufacturing a plastics article as claimed in any one of the preceding claims, wherein a bracing member is located in the cavity.

7. A method of manufacturing a plastics article as claimed in claim 6, wherein the bracing member is surrounded by the plastics strengthening material during the transformation step.

8. A method of manufacturing a plastics article as claimed in claim 6 or 7, wherein the bracing member comprises protrusions for enhancing the fixing thereof to the plastics reinforcement.

9. A method of manufacturing a plastics article as claimed in claims 6 to 8, wherein the bracing member is made of a metallic material.

10. A method of manufacturing a plastics article as claimed in any one of the preceding claims, wherein the plastics article is a base panel or body panel of a motor vehicle.

11. A method of manufacturing a plastics article substantially as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.

12. A plastics article manufactured in accordance with the method claimed in any one of the preceding claims.

13. A motor vehicle incorporating at least one base panel or body panel manufactured in accordance with the method claimed in claims 1 to 11.

14. A plastics article substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.