The present application relates to a multi-layer fire resistant and insulative coating for the protection of structural steel, and in particular for use in coating a fire-fighting vehicle.

Intumescent materials are widely documented and used as fire retardant coatings in a variety of applications including the protection of structural steel where the objective is to not allow the steel to reach 550°C. Steel first expands with increasing heat, but once above its critical temperature, it loses its strength and buckles.

When exposed to heat an intumescent material swells, thus increasing in volume and decreasing in density. Intumescent materials are typically endothermic to varying degrees, as they can contain chemically bound water, this can be very important in fire testing. Hydrates in the intumescent material or endothermic coating tend to maintain the temperature of their substrate to 100°C, the boiling point for water, until all the hydrates are spent. In fireproofing applications using water-bearing products, the temperature increase in the substrate or the item to be protected, tends to "flatline" at the 100°C mark, until the water is spent. Then, the temperature will resume increasing. This buys time for the substrate.

Different applied thicknesses of intumescent coating will give varying thicknesses of 'char', and therefore differing time periods of fire resistance to protect a certain size steel section.

Hydrated metal silicates are known fire-proofing materials and are extensively employed in building construction to insulate apertures and passages in buildings against the passage of fire and smoke. Under the high temperatures existing during a fire, the water of hydration of the metal silicates are driven off causing the composition to expand by up to forty times its original volume forming a foam structure that insulates the building against heat generated by the fire. Limitations and technical barriers of similar existing products are the relatively low fire exposure resistance and reduced operability of electronic systems in such extreme conditions and environments.

The steel structures of the World Trade Centre were protected by intumescent paint but the high wind speeds generated by the ferocity of the fire on 9/11 created a strong wind due to a chimney effect and this blew the coating off the steelwork thus causing the beams to exceed their critical temperature and fail. Thus the use of intumescent coatings is currently limited when considering a fire fighting vehicle. Furthermore, typical intumescent materials form a 'soft char' when activated which can be easily damaged or removed in extreme environmental conditions. More robust chars tend to be more difficult to apply and need to be applied in a thick layer and therefore are more expensive.

There is a need for an intumescent coating for an autonomous unmanned fire fighting vehicle able to fight efficiently against fires in hazardous environments, particularly where men and firemen are highly jeopardized.

Areas of usage include:

o Wild fires & forest fires

o Oil refineries and chemical plants

o Storage areas of chemicals

o Storage areas of flammable materials

o Army storage depots for explosives

o Nuclear power stations

o Airports for special circumstances (fire/explosion of airplanes)

o Transportation of flammable materials (trains, lorries, etc.) o Forests, for areas non-accessible by fire-fighting vehicles and/or firemen and where only fire-fighting airplanes and helicopters can be used (only during daylight). It can also be used to clear the path (using flail tool) and create accessible zones for fire-fighting vehicles

o Forests with dangerous areas (where unexploded cells or mines exist below the ground surface)

The vehicle ideally has to resist temperatures of 750°C for 15 minutes and 400°C for at least 30 minutes of operation without suffering significant structural damage. The remote controlled movement and thermal imaging systems should then be able to operate and return the vehicle from the fire site.

Limitations and technical barriers of existing products are the relatively low fire exposure resistance and reduced operability of electronic systems in such extreme conditions and environments.

The present invention addresses these issues and provides a new concept for fire protection and temperature resistance of discovered and undiscovered parts of a vehicle.

In accordance with a first aspect of the invention, there is provided a coating as claimed in claim 1.

The invention provides a means of protecting the structural steel vehicle and ensuring that preferably the protected surface (typically 10mm thick steel) does not reach a temperature in excess of 250°C, whilst insulating electronic systems within the vehicle from the extremes of temperature.

A transparent water resistant topcoat comprising an acrylic material, a silicone, PFTE or a fluorochemical material protects the water sensitive silicate based multilayer structure. Metallic flake incorporated into the uppermost layer of the intumescent coating acts as a reflector and reduces the heat transmitted to the coating. This increases the temperature at which the vehicle can operate. Once the critical temperature is reached the multi-layer intumescent coatings trigger to protect the vehicle from structural damage and failure. It is intended that the multilayer intumescent coating only triggers when the vehicle is at risk, thereby protecting the vehicle although the coating will need to be reapplied.

The coating can be applied to structural steel with no need for a primer or expensive surface preparation. Before activation the coating is extremely resistant to impact/structual damage etc. Upon activation the coating remains intact and consolidated and strongly adheres to the sheet substrate; however, after use it can be easily be removed for re-application

The disclosures in United Kingdom patent application no. 1009390.4, from which this application claims priority, and in the abstract accompanying this applications are incorporated herein by reference.

EXAMPLES

A) Actual Formulation - Preferred Formulation B) Formulation Range - Other possibilities