GB2131723A

GB2131723A - Painting plastics components

Info

Publication number: GB2131723A
Application number: GB08236030A
Authority: GB
Inventors: Charles Edward Herriott; Alan Peter Weakley
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1982-12-17
Filing date: 1982-12-17
Publication date: 1984-06-27

Abstract

A plastics component is painted by making at least its surface conductive (by loading conductive powder therein or applying conductive paint), applying a layer of paint by cathodic electro-coating, and applying further coats of paint to the electro-coated layer. By applying an electro-coated layer, the rejection rate of the components is reduced, since the electro-coated layer prevents the formation of blisters in the enamel layer which would otherwise occur due to solvent absorbed in the plastics material coming to the surface on heating the component to cure the enamel layer. An article (e.g. a motor vehicle) having both plastics and metal components can be painted by making the surfaces of the plastics components conductive, assembling the plastics and metallic components, passing the assembled components through a phosphating bath, applying a coat of paint to the components by cathodic electro-coating, and applying further layers of paint to the electro-coating layer. Thus the same painting process can be used for both the plastics and metal components.

Description

SPECIFICATION Painting of plastics components The present invention relates to the painting of plastics and in particular thermosetting plastics components. The invention is particularly applicable to components to be assembled into a motor vehicle but may also find use in the finishing of components to be assembled into other articles made of metal.

Hitherto, certain thermosetting plastics material, such as hand layed fibre glass, sheet moulding compound (SMC) and dough moulding compound (DMS) have been used to manufacture certain components such as grilles. When these components were painted in a conventional manner, using a primer and an enamel coat, there occurred paint defects which, it is believed, were caused by the fact that the solvent used in the paint could collect in pockets in the plastics material but come through when subsequently the article was heated to harden the finish coat. The resulting blisters were the reason for a high rejection rate. Furthermore, the grille and other plastics components were assembled on the vehicle only after the entire vehicle had been sprayed and as a result the paint surface could be damaged on assembly.

By contrast it was found that metal parts and panels had relatively few defects. A common method employed for painting metal parts of a motor vehicle involves the steps of phosphating the metal surface, drying the phosphated surface and applying a protective layer of paint by cathodic electro-coating. The last step involves dipping the entire body in the vehicle in a tank filled with a liquid and ionised paint and attracting the paint to the surface of the component by passing an electric current. The electro-coating adheres strongly to the entire surface of the vehicle and provides a strong and resistant layer.

This layer is normally heated to between 1750 and 1 900C for approximately 10 minutes and, after its application, the vehicle body is primed and enamel coated in the usual manner.

A first aim of the invention is to enable the rejection rate in the painted plastics components to be reduced.

According to a first aspect of the present invention, there is provided a painted plastics component, wherein the painting is effected by rendering conductive at least the surface of the plastics material to be painted, applying a layer of paint to the conductive plastics material by cathodic electro-coating, and applying further coats of paint, as desired, to the electro-coating layer.

This invention is based on the realisation that the electro-coating layer is responsible for the improved rejection rate achieved with metal panels and aims to enable the same advantage to be achieved for plastics components.

The plastics material may be rendered conductive by loading the resin with an electrically conductive powder, but it is preferred to coat the finished plastics component with a layer of electrically conductive paint.

Advantageously, the paint is loaded with graphite but other forms of paint may also prove satisfactory.

In accordance with a second aspect of the invention, there is provided a method of manufacturing an article, such as a motor vehicle, which comprises plastics and metal components, the method comprising the steps of rendering conductive at least the surfaces to be painted of the plastics component, assembling the plastics and metallic components, passing the assembled components through a phosphating bath, applying a coat of paint to the components by cathodic electro-coating, and applying further layers of paint, as desired, to the electro-coating layer.

It has been found that a suitable electrically conductive paint is that obtainable from International Paint under the code 5958 X9010, using catalyst code 0000-7-0300 and thinner code 0000-6-0808. This is a paint loaded with graphite and though this has so far proved the most successful paint other methods of loading may also prove acceptable.

After the conductive layer is applied, the component is electro-coated and may be passed through a phosphating bath prior to electrocoating. With thermosetting plastics components prepared in this manner it was found that they could be heated in the same way as metal components to cure subsequently applied layers of paint without the high risk of paint blisters experienced when painting directly onto the unprepared plastic surface.

Though it is preferred to apply a conductive paint layer to the plastics components, the entire plastics material may be rendered conductive if loaded with a conductive powder. This method is however more expensive to implement and may also affect the mechanical properties of the plastics material. Furthermore, if only some surfaces are coated with conductive paint then only those surfaces will receive the electro-coating layer, thus making more efficient use of the paint applied by cathodic electro-coating.

Thus the invention can reduce the rejection rate in the painting of plastics materials employed in motor vehicles and can also give the advantage that once plastics components have been rendered conductive they may be passed through the same preparation and painting processes as the body panels and other metal components so that no further assembly work need be carried out once the vehicle has been painted.

A further advantage in the application of a layer of paint to the plastics components by cathodic electro-coating is that the enamel layer on the plastics components ages in the same way as the metal components, because the electro-coating layer acts as a barrier between the paint layers and the underlying metal or plastics material

CLAIMS 1. A painted plastics component, wherein the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Painting of plastics components The present invention relates to the painting of plastics and in particular thermosetting plastics components. The invention is particularly applicable to components to be assembled into a motor vehicle but may also find use in the finishing of components to be assembled into other articles made of metal. Hitherto, certain thermosetting plastics material, such as hand layed fibre glass, sheet moulding compound (SMC) and dough moulding compound (DMS) have been used to manufacture certain components such as grilles. When these components were painted in a conventional manner, using a primer and an enamel coat, there occurred paint defects which, it is believed, were caused by the fact that the solvent used in the paint could collect in pockets in the plastics material but come through when subsequently the article was heated to harden the finish coat. The resulting blisters were the reason for a high rejection rate. Furthermore, the grille and other plastics components were assembled on the vehicle only after the entire vehicle had been sprayed and as a result the paint surface could be damaged on assembly. By contrast it was found that metal parts and panels had relatively few defects. A common method employed for painting metal parts of a motor vehicle involves the steps of phosphating the metal surface, drying the phosphated surface and applying a protective layer of paint by cathodic electro-coating. The last step involves dipping the entire body in the vehicle in a tank filled with a liquid and ionised paint and attracting the paint to the surface of the component by passing an electric current. The electro-coating adheres strongly to the entire surface of the vehicle and provides a strong and resistant layer. This layer is normally heated to between 1750 and 1 900C for approximately 10 minutes and, after its application, the vehicle body is primed and enamel coated in the usual manner. A first aim of the invention is to enable the rejection rate in the painted plastics components to be reduced. According to a first aspect of the present invention, there is provided a painted plastics component, wherein the painting is effected by rendering conductive at least the surface of the plastics material to be painted, applying a layer of paint to the conductive plastics material by cathodic electro-coating, and applying further coats of paint, as desired, to the electro-coating layer. This invention is based on the realisation that the electro-coating layer is responsible for the improved rejection rate achieved with metal panels and aims to enable the same advantage to be achieved for plastics components. The plastics material may be rendered conductive by loading the resin with an electrically conductive powder, but it is preferred to coat the finished plastics component with a layer of electrically conductive paint. Advantageously, the paint is loaded with graphite but other forms of paint may also prove satisfactory. In accordance with a second aspect of the invention, there is provided a method of manufacturing an article, such as a motor vehicle, which comprises plastics and metal components, the method comprising the steps of rendering conductive at least the surfaces to be painted of the plastics component, assembling the plastics and metallic components, passing the assembled components through a phosphating bath, applying a coat of paint to the components by cathodic electro-coating, and applying further layers of paint, as desired, to the electro-coating layer. It has been found that a suitable electrically conductive paint is that obtainable from International Paint under the code 5958 X9010, using catalyst code 0000-7-0300 and thinner code 0000-6-0808. This is a paint loaded with graphite and though this has so far proved the most successful paint other methods of loading may also prove acceptable. After the conductive layer is applied, the component is electro-coated and may be passed through a phosphating bath prior to electrocoating. With thermosetting plastics components prepared in this manner it was found that they could be heated in the same way as metal components to cure subsequently applied layers of paint without the high risk of paint blisters experienced when painting directly onto the unprepared plastic surface. Though it is preferred to apply a conductive paint layer to the plastics components, the entire plastics material may be rendered conductive if loaded with a conductive powder. This method is however more expensive to implement and may also affect the mechanical properties of the plastics material. Furthermore, if only some surfaces are coated with conductive paint then only those surfaces will receive the electro-coating layer, thus making more efficient use of the paint applied by cathodic electro-coating. Thus the invention can reduce the rejection rate in the painting of plastics materials employed in motor vehicles and can also give the advantage that once plastics components have been rendered conductive they may be passed through the same preparation and painting processes as the body panels and other metal components so that no further assembly work need be carried out once the vehicle has been painted. A further advantage in the application of a layer of paint to the plastics components by cathodic electro-coating is that the enamel layer on the plastics components ages in the same way as the metal components, because the electro-coating layer acts as a barrier between the paint layers and the underlying metal or plastics material CLAIMS

1. A painted plastics component, wherein the painting is effected by rendering conductive at least the surface of the plastics material to be painted, applying a layer of paint to the conductive plastics material by cathodic electro-coating, and applying further coats of paint, as desired, to the electro-coating layer.

2. A painted plastics component as claimed in claim 1, wherein the plastics material after being rendered conductive is passed through a phosphating bath prior to being electro-coated.

3. A painted plastics component as claimed in claim 1 or claim 2, wherein the surface to be painted is rendered conductive by the application of a layer of conductive paint.

4. A painted plastics component as claimed in claim 3, wherein the conductive paint is loaded with graphite.

5. A method of manufacturing an article, such as a motor vehicle, which comprises plastics and metal components, the method comprising the steps of rendering conductive at least the surfaces to be painted of the plastics components, assembling the plastics and metallic components, passing the assembled components through a phosphating bath, applying a coat of paint to the components by cathodic electro-coating, and applying further layers of paint, as desired, to the electro-coating layer.