GB2130919A

GB2130919A - Method of and composition for treating glass-fibre reinforced polyester resin boat hulls and the like

Info

Publication number: GB2130919A
Application number: GB08332196A
Authority: GB
Inventors: Roy Vincent Osborne
Original assignee: Richmond Marine Ltd
Current assignee: Richmond Marine Ltd
Priority date: 1982-12-03
Filing date: 1983-12-02
Publication date: 1984-06-13
Also published as: GB2130919B; GB8332196D0

Abstract

A method of treating glass-fibre reinforced polyester resin boat hulls and other articles, the surface of which is subjected to prolonged exposure to water in use, in order to prevent damage to a gel layer on the surface by the "osmosis" effect comprises treating the surface, prepared as required with a layer of a composition comprising a mixture of a metal powder and a moisture- hardenable polyurethane prepolymer resin, and thereafter causing or allowing the resin to harden. The preferred metal powder is copper, which also has an anti-fouling effect, particularly if the hardened layer is given a matt finish.

Description

SPECIFICATION Method of and composition for treating glassfibre reinforced polyester resin boat hulls and the like The present invention relates to a method of and compositions for the treatment of boat hulls and other articles which in use are exposed to the action of water and which are made of a glassfibre reinforced plastics material. The invention is particularly applicable to boat hulls and will be described with particular reference to such use, but it is not limited to this use.

Because of their lightness, strength and cheapness, boat hulls are nowadays frequently made of glass-fibre reinforced polyester resin material. In the manufacture of such hulls, it is usual to provide an outer layer of a polyester resin on the surface of the hull during manufacture. This layer which is generally referred to as the "gel layer" or "gel coat" is formed initially on the inside of the mould used to form the hull, the glass-fibre reinforcement and impregnating resin being subsequently applied thereto to build up the hull.

It has been found, however, that such boat hulls in use suffer from a deterioration of the gel layer (often referred to as "osmosis") in which the hull exhibits a series of various sized blisters below the water-line caused primarily by penetration of water through the gel layer during prolonged immersion, and leading to erosion of the gel layer and the laminate.

It is an object of the present invention to provide a method of treating a boat hull or other article made of glass-fibre reinforced polyester resin and having a surface exposed to the action of water in use, which protects the hull or other article and prevents such deterioration of the gel coat and laminate.

According to one aspect of the invention, there is provided a method of treating a boat hull or other article having a surface which is exposed in use to the action of water and which is made of glass-fibre reinforced polyester resin having a gel layer at said surface, said method comprising the steps of applying to the said surface a layer of a composition comprising a mixture of a metal powder with a polyurethane prepolymer resin which can be hardened on curing by exposure to moisture, and causing or allowing said resin to cure. The preferred metal powder is copper powder, although other metal powders, such as powdered zinc or aluminium, can be used.

According to another aspect of the invention, there is provided a composition for use in such a method comprising a mixture of copper powder and a polyurethane prepoiymer resin which can be cured by exposure to moisture.

The prepolymer resin is normally used in the form of a solution having a solids content such that when thoroughly mixed with the required amount of copper powder, the resulting mixture can be applied to the prepared hull surface by means of a brush or roller, or in any other suitable way, and will thereafter react with moisture to form a hard shell which has been found effectively to prevent the penetration of water through the gel layer. The fact that the polyurethane prepolymer can be cured by reaction with moisture makes it particularly suitable for use with boat hulls where, generally speaking, it is not possible to provide ideal working conditions, such as would be required, for example, for the use of conventional 2-pack (resin/hardener) polyurethane or epoxy resins.The presence of the copper powder also appears to assist curing by chemical action, possibly catalytic in nature.

The presence of copper powder in the composition has the additional advantage that it will act as an anti-foulant discouraging marine growth, if the outer glaze is removed from the cured layer where curing is complete, in order to provide the desired matt finish for the hull. It has, indeed, been found that if a high proportion of copper powder is used, the desired matt finish may be automatically produced, without the necessity of removing an outer glaze.

While various proportions of copper powder to prepolymer resin may be used, it is preferred to use the two components in the approximate proportions of 500 g of copper powder to 1 litre of the prepolymer resin component.

The copper powder used is preferably a sintered powder, the particles of which are irregular in shape and has a 200 mesh STD particle size. Other copper powders of different mesh size may, however, be used.

Where a newly-manufactured hull, or one with the gel layer still in good condition, is to be treated in accordance with the invention, it is only necessary to rub the hull down before applying the polyurethane prepolymer-copper powder mixture.

However, when treating a hull in which the gel layer is already badly blistered or eroded by the penetration of water, it may be desirable for best results to first coat the hull with an epoxy resin primer, before applying the polyurethane-copper mixture.

In one specific example of a composition according to the invention, a polyurethane prepolymer resin ("SPECTRAGLAZE" marketed by Spectrum Resins Systems Ltd.) having a 45% solids content is mixed with a sintered copper powder with irregular particles having a 200 mesh STD particle size, in the proportions of 1 litre of resin to 500 g of copper powder. A layer of the mixture was applied to the gel layer of a glassfibre reinforced polyester resin boat hull and allowed to harden by the action of moisture. After curing was complete the outer resin glaze was removed from the hardened shell formed to provide a protective layer which was effective both in preventing penetration of water through the gel layer and as an anti-foulant coating to discourage marine growth.

Moisture-hardening polyurethane prepolymer resins suitable for use in the present invention are well known to those skilled in the coating art and are commercially available. Besides the "SPECTRAGLAZE" resin referred to above, suitable commercially available resins include those marketed by Bayer under the Trade Marks "DESMODUR El 361" and "DESMODUR Eft375".

Both of these are polyisocyanate prepolymer resin solutions based on toluene di-isocyanate, 'DESMODUR E1361" being dissolved in 1:1 ethyl glycol acetate/xylene and having a solids content of about 61% and an NCO-content of about 6.5%, while "DESMODUR El 375" is dissolved in ethyl acetate to.a solids content of about 75% and has an NCO-content of about 8.4%. Both can be thinned as required by the addition of further solvent.

If zinc or aluminium powders are used in place af copper powder, these can be used in the same psbportions with'respect to the resin as the copper powder, and may have a particle size of 200 mesh for aluminium and 300 mesh for zinc powder.

Copper powder has, however, particularly useful anti-foulant and curing-assisting properties and is therefore greatly preferred for use in the present invention.

Claims

CLAIMS-

1. A method óf treating a boat hull or other article having a surface which is exposed in use to the action of water and which is made of glass fibre reinforced pólyester resin having a gel layer at said surface, said method comprising the steps of applying to the said surface a layer of a composition comprising a mixture of a metal powder with a polyurethane prepolymer resin which can be hardened on curing by exposure to moisture, and causing or allowing said resin to cure.

2. A method as claimed in Claim 1, wherein said metal powder is copper powder.

3. A method as claimed in Claim 2, wherein after the completion of curing, any outer glaze present on the surface of the cured layer is removed to provide a matt surface.

4. A method as claimed in Claim 2 or Claim 3, wherein said surface is coated with an epoxy resin primer, prior to the application of said layer.

5. A method as claimed in any one of Claims 2 to 4, wherein said copper powder is present in said mixture in an amount of approximately 500 g per litre of polyurethane prepolymer resin.

6. A method as claimed in any one of Claims 2 to 5, wherein said copper powder is a sintered powder having irregularly-shaped particles of 200 mesh STD particle size.

7. A method of treating a boat hull or other article having a surface which is exposed in use to the action of water and which is made of glassfibre reinforced polyester resin having a gel layer at said surface, substantially as hereinbefore described with reference to the example.

8. A boat hull or other article having a surface which is. exposed in use to the action of water, which is made of glass-fibre reinforced polyester resin having a gel layer at said surface, and which has been treated by a method as claimed in any one of Claims 1 to 7.

9. A composition for use in a method as claimed in Claim 1 comprising a mixture of copper powder and a polyurethane prepolymer resin which can be cured by exposure to moisture.

10. A composition as claimed in Claim 9, wherein said copper powder is present in an amount of approximately 500 g per litre of polyurethane prepolymer resin.

11. A composition as claimed in Claim 9 or Claim 10, wherein said copper powder is a sintered powder having irregularly-shaped particles of 200 mesh STD particle size.

12. A composition for use in the method of Claim 1, substantially as hereinbefore described.