GB2340431A

GB2340431A - A method of moulding and a moulding formed thereby

Info

Publication number: GB2340431A
Application number: GB9817890A
Authority: GB
Inventors: Gordon Frederick Smith; Susan Rebboah; Vannessa Goodship
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1998-08-18
Filing date: 1998-08-18
Publication date: 2000-02-23
Also published as: GB9817890D0

Abstract

The method involves providing a thermosetting granular plastics material which is heated to a plastics condition to form a plastics coating material 23 and injected into a mould. A substrate mixture 24 comprising automotive shredder residue and a thermosetting granular plastics material is then injected to spread the coating material 23 over surfaces of the mould so as to envelope the mixture 24. A moulding is thus produced having a substrate including automotive shredder residue and a coating. The automotive shredder residue is sealed within the moulding. This method provides an alternative route for the disposal of automotive shredder residue. The plastics materials may be thermoplastics or elastomers.

Description

2340431 - I A Method of Moulding and a Moulding formed therebv The present

invention relates to a method of forming a moulding by dual injection and to a moulding formed in accordance with such a method. In particular, but not exclusively, the invention relates to the moulding of a vehicle body component.

Known dual injection moulding techniques involve injecting a first plastics material into a mould followed by a second plastics material. The injection steps cause the first material to coat the mould surfaces and the second material to form a substrate for the first. The component so formed may harden in the mould prior to removal from the mould.

An increasing number of motor vehicles are now provided with components such as body panels made from plastics materials.

At the end of the life of a motor vehicle, the motor vehicle is scrapped.

Many of the parts may be reclaimed and recycled. Indeed, there is an increasing drive to increase the proportion of materials salvaged in this way. However, those parts that are not currently salvaged or salvageable are shredded to form automotive shredder residue which is currently disposed of as landfill. Typically, automotive shredder residue comprises fragments of glass, plastics and wood, pieces of metal such as small springs, hydrocarbon residues such as brake fluid and oil, mud and dirt. As such, automotive shredder residue frequently has an extremely pungent, unpleasant odour. However, increased taxes and other environmental legislation is making disposal of such automotive shredder residue as landfill an increasingly unattractive option. Accordingly, there is a need for an alternative disposal route for automotive shredder residue other than as landfill.

It is an advantage of the present invention that it provides a use for automotive shredder residue other than as landfill.

According to a first aspect of the invention there is provided a method of forming a moulding by dual injection comprising injecting a plastics coating material into a mould and injecting a substrate material into the mould to cause the coating material to coat a surface of the mould and to produce a moulding having a coating formed by the plastics coating material, characterised in that the substrate material comprises a mixture of a plastics material and automotive shredder residue, in which the plastics coating material and the plastics material of the mixture exhibit similar behaviour when heated. By this it should be understood that the two plastics materials are both thermosetting plastics materials, both thermoplastic plastics materials or both elastomers.

This has the advantage that the automotive shredder residue is no longer disposed of as landfill, but also has a further useful life as a further component. Further, because the automotive shredder residue is sealed within the coating, the odour of the automotive shredder residue is no longer a problem. In addition, since automotive shredder residue is usually very dark or black in colour, the colour of the plastics materials used, in particular of the coating material, can be used to hide the colour of the automotive shredder residue.

Preferably, the mixture comprises at least 50 per cent plastics material.

According to a second aspect of the invention there is provided a moulding formed by a method according to the first aspect of the invention.

The invention also includes a moulding formed by dual injection comprising a substrate material having a plastics coating material thereon, characterised in that the substrate material comprises a mixture of a plastics material and automotive shredder residue, in which the plastics material of the coating and the plastics material of the mixture exhibit similar behaviour when heated.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Figure 1 shows a diagrammatic cross section through part of a dual injection moulding machine showing the injection into a mould of a granulated plastics material in a plastic condition, Figure 2 shows the introduction of a substrate material into the mould,

Figure 3 shows the form of the moulding after injection of the substrate material is complete, Figure 4 shows a second injection of the powdered plastics material in a plastic condition to finish off the moulding step, Figure 5 shows a diagrammatic view of the moulding removed from the mould and placed in an oven for post curing the coating, Figure 6 shows a cross section to a larger scale through part of a component made by a method in accordance with the present invention, Figure 7 shows a perspective view of a vehicle wing in accordance with the present invention and including an encircled enlargement of a section of the wing and Figure 8 shows a cross section of part of the wing of Figure 7 on the line VIII - VIII in Figure 7.

With reference to Figure 1, the injection moulding machine has a mould having first and second halves 12, 13 defining a hollow cavity 14 therebetween. The hollow cavity 14 communicates with a block 15 which defines a passageway 16 for material from a first extruder 17 and a second passageway 18 for material from a second extruder 19. A rotary valve 20 is positioned between the block 15 and an inlet port 22 in mould half 13 for selection of the material to be injected into the cavity 14.

The first extruder 17 is associated with a first heater 17a and is operated to deliver a coating material 23 formed by heating a thermosetting granulated plastics material 23a into a thermoplastic phase in which it takes on a putty-like plastic condition. A suitable granulated plastics material has been found to be one which will have a plastic condition at a temperature of around 170"C with a putty-like viscosity.

The second extruder 19 is associated with a second heater 19a and is operated to deliver a substrate material 24 formed by heating a mixture 24a. The mixture 24a comprising automotive shredder residue and a thermosetting plastics material is prepared. The mixture 24a comprises approximately equal proportions of automotive shredder residue and thermosetting plastics material. If desired, a greater or lesser proportion of automotive shredder residue may be used. The automotive shredder residue has had any larger fragments removed, and is preferably subject to grinding to further reduce the size of the residue prior to preparation of the mixture. The small size of the residue together with the presence of the plastics material acts to prevent damage to the second extruder 19. To prevent damage to the second extruder it is suggested that no more than 70 per cent 5 of the mixture comprise automotive shredder residue.

As shown in Figure 1, an initial quantity of the coating material 23 is injected into the cavity 14, the mould being at a temperature in a range of, for example, 20C to 100"C. The valve 20 is then rotated to shut off feed of material 23. As shown in Figure 2, the mixture 24a is heated by'the second heater 19a associated with the second extruder 19 and is injected into the cavity 14 behind the injected material 23 as shown in Figure 2. Injection of the mixture 24a causes the mixture 24a to spread the coating material 23 over the mould surfaces 14a defining cavity 14 and injection is continued until the surfaces are coated with the material 23 and the material 23 envelopes the mixture 24. The mixture 24a thus forms a substrate or core 24 as shown in Figure 3 having a coating or skin formed by the material 23.

In Figure 4, the valve 20 is rotated again to shut off feed from the second extruder 19 and to permit injection of coating material 23 into the port 22 so that the machine is ready for another injection cycle.

The heat applied to the thermosetting coating material 23 while it is temporarily in the extruder 17 is absorbed by the material and, once in the mould 10, the heat will begin the curing process of the material. That process may begin as the material is being spread over the mould surfaces by the incoming substrate material or may begin after the injection steps are complete. Preferably, however, the curing of the thermosetting coating material 23 and the thermoplastics material of the substrate mixture 24 will allow sufficient time to enable cross-linking to take place between the two materials thereby ensuring an extremely good bond between them. The bond between the coating material 23 and the thermosetting material of the substrate material 24 may be further enhanced if the same thermosetting material is used for the coating material 23 and as part of the substrate material 24. Instead of a cross-linking occurring between the coating and substrate materials, a good bond alone may be achieved between them due to their intimate contact during injection.

If additional heat is required to cure the thermosetting coating material 23, the moulding (indicated at 11 in Figure 5) can be removed from the mould 10 and placed in an oven 30. The oven is pre-heated to a temperature of around, for example 250C. The moulding 11 is subjected to heat at that temperature, as indicated by arrows, for a period which is sufficient to cure the coating material 23 but which is insufficient to have a significant softening effect on the bulk of the thermosetting plastics material of the substrate material 24. It is believed that with careful control of timing and temperature, a good bond will be achieved between the coating material 23 and the substrate material 24.

The thermosetting plastics material of the substrate material 24 is 5 preferably selected so that it will have an affinity to the coating material 23.

The injection moulding tool 10 can provide a superfine surface finish for the coating. Moreover, by producing a coating in a dual injection moulding process, the finished coating will be free from contamination by air-borne dust as well as being uniform and consistent.

If desired, the substrate mixture 24 can include a thermosetting material instead of a thermoplastics material. In such a case, the coating material 23 should also take the form of a thermoplastics material. The injection steps will be the same as that described above with reference to the drawings except that the mould will be hotter e.g. at a temperature in a 15range 100C to 180C.

It is envisaged that the method in accordance with the invention can be used to produce by injection moulding various body components of a motor vehicle.

An example of a vehicle body wing in accordance with the invention is shown in Figures 8 and 9.

Utilising a mould normally used for the injection moulding of a vehicle front wing 50 for subsequent spray or dip painting after it has been removed from the mould, the mould was positioned on a machine for providing dual injection of plastics material. The two extruders of the machine were supplied with coating material 23 and substrate mixture 24 respectively.

The coating material used was a granulated thermoplastics material heated to a temperature of 190'C. Such heating brought the coating material to its plastic phase enabling it to be injected by its extruder into the mould using an injection pressure of around 1300 bar.

The substrate mixture 24 was a mixture of a granulated thermoplastics material and automotive shredder residue and was heated to a temperature of 230C to enable it to be injected by the second extruder at a pressure of 1300 bar.

A white polypropylene was used as the granulated thermoplastics material in each case.

Using the injection method as described with reference to Figures 1 to 4, the mould was be heated to a temperature of 60"C, the materials 23, 24 then injected into the mould and the moulded materials left in situ in the mould for a period of around 90 seconds to allow the materials to cure. The 5 moulded wing 50 was then removed from the mould and inspected.

The coating material 23 completely enveloped the substrate 24 leaving no light patches or uncovered areas.

The wing 50 was moulded so as to include integral fixing flanges 52, 53 with fastener receiving apertures 52a, 53a therein and a stiffening 10 flange 54.

Claims

- 11 CLAIMS

1. A method of forming a moulding by dual injection comprising injecting a plastics coating material into a mould and injecting a substrate material into the mould to cause the coating material to coat a surface of the mould and to produce a moulding having a coating formed by the plastics coating material, characterised in that the substrate material comprises a mixture of a plastics material and automotive shredder residue, in which the plastics coating material and the plastics material of the mixture exhibit similar behaviour when heated.

2. A method according to claim 1, characterised in that the mixture comprises at least 30 per cent plastics material.

3. A method according to claim 2, characterised in that the mixture comprises at least 50 per cent plastics material.

4. A method according to any previous claim, characterised in that the plastics coating material and the plastics material of the substrate material are both thermosetting polymers.

5. A method according to claim 4, characterised in that the same thermosetting polymer is used for the plastics coating material and for the plastics material of the substrate material.

6. A method according to any of claims 1 to 3, characterised in that the plastics coating material and the plastics material of the substrate material are both thermoplastic polymers.

7. A method according to claim 6, characterised in that the same thermoplastic polymer is used for the plastics coating material and for the plastics material of the substrate material.

8. A method according to any of claims 1 to 3, characterised in that the plastics coating material and the plastics material of the substrate, material are both elastomers.

9. A method according to claim 8, characterised in that the same elastomer is used for the plastics coating material and for the plastics material of the substrate material.

10. A method of producing a component by dual injection substantially as described herein with reference to and as illustrated in the accompanying drawings.

11. A moulding formed by a method according to any of claims 1 to 10.

12. A moulding formed by dual injection comprising a substrate material having a plastics coating material thereon characterised in that the substrate material comprises a mixture of a plastics material and automotive shredder residue, in which the plastics coating material and the plastics material of the mixture exhibit similar behaviour when heated.

13. A moulding according to claim 12, characterised in that the mixture comprises at least 30 per cent plastics material.

14. A moulding according to claim 12, characterised in that the mixture comprises at least 50 per cent plastics material..

15. A moulding according to any of claims 12 to 14, characterised in that the plastics coating material and the plastics material of the substrate material are both thermosetting polymers.

16. A moulding according to claim 15, characterised in that the same thermosetting polymer is used for the plastics coating material and for the plastics material of the substrate materiaL

17. A moulding according to any of claims 12 to 14, characterised in that the plastics coating material and the plastics material of the substrate material are both thermoplastic polymers.

18. A moulding according to claim 17, characterised in that the same thermoplastic polymer is used for the plastics coating material and for the plastics material of the substrate material.

19. A moulding according to any of claims 12 to 14, characterised in that the plastics coating material and the plastics material of the substrate material are both elastomers.

20. A method according to claim 19, characterised in that the same elastomer is used for the plastics coating material and for the plastics material of the substrate material.

21. A moulding formed by dual injection constructed and arranged substantially as described herein with reference to and as illustrated in the accompanying drawings.

22. A moulding according to any of claims 13 to 21 in the form of a motor vehicle body part.