Fire retardant coating composition

1. A halogen-free fire retardant coating composition comprising:

i) film forming polymer

ii) inorganic fire retardant material

characterised in that the fire retardant material comprises a combination of fire retardant filler particles and a metal stannate, a metal hydroxy stannate or a combination thereof, wherein the overall PVC of the composition is from 75 to 97% and the composition has a medium shear viscosity measured at 25° C. of from 0.6 Pa·s to 6.0 Pa·s.

2. A fire retardant coating composition according to claim 1 characterised in that the fire retardant material comprises fire retardant filler particles coated with the metal stannate, or the metal hydroxy stannate, or a combination thereof.

3. A fire retardant coating composition according to claim 1 characterised in that the inorganic fire retardant material is able to give off water, carbon dioxide or a combination thereof when in the form of a dried coating and exposed to the elevated temperatures found in or close to a flame in a fire.

4. A fire retardant coating composition according to claim 2 characterised in that the inorganic fire retardant material is able to give off water, or carbon dioxide, or combination thereof when in the form of a dried coating and exposed to the elevated temperatures found in or close to a flame in a fire.

5. A fire retardant coating composition according to claim 1 characterised in that the fire retardant filler is selected from the group consisting of huntite, hydromagnesite, aluminium trihydroxide and magnesium hydroxide.

6. A fire retardant coating composition according to claim 1 characterised in that the metal hydroxy stannate is zinc hydroxy stannate.

7. A fire retardant coating composition according to claim 1 characterised in that the fire retardant material comprises from 100 to 2000% by weight of the film forming polymer.

8. A fire retardant coating composition according to claim 1 characterised in that the composition also contains at least one component selected from the group consisting of pigments, rheological modifiers, flow aids, dispersants, extenders, anti-foams, crosslinking agents and biocides.

9. A fire retardant coating composition according to claim 1 characterised in that the composition is waterborne.

10. A fire retardant coating composition according to claim 1 characterised in that the particles in the composition are substantially spherical particles up to 1000 microns in diameter.

11. A fire retardant coating composition according to claim 1 characterised as present on a substrate.

12. A fire retardant coating composition according to claim 1 characterised as present as a first dried layer of a fire retardant coating system having a second dried layer over the first dried layer where the second dried layer is of a different composition to the first.

13. A fire retardant coating composition according to claim 1 characterised as having at least two of:

i) a fire retardant filler selected from the group consisting of huntite, hydromagnesite, aluminium trihydroxide and magnesium hydroxide;

ii) a metal hydroxy stannate that is zinc hydroxy stannate;

iii) a fire retardant material comprising from 100 to 2000% by weight of the film forming polymer;

iv) at least one component selected from the group consisting of pigments, rheological modifiers, flow aids, dispersants, extenders, anti-foams, crosslinking agents and biocides;

v) a medium shear viscosity measured at 25° C. from 0.6 pa·s to 6.0 Pa·s;

vi) a composition that is waterborne; or

vi) the particles present a substantially spherical particles up to 1000 microns in diameter.

14. A fire retardant coating composition according to claim 13 present on a substrate.

15. A fire retardant coating composition according to claim 14 characterised in that the fire retardant coating composition present on the substrate is as a first dried layer of a fire retardant coating system having a second dried layer over the first dried layer where the second dried layer is of a different composition to the first dried layer.

16. A fire retardant coating composition according to claim 1 characterised in that the fire retardant coating composition is prepared by:

a) forming a uniform dispersion by combining water and a clay thickener,

b) adding to the dispersion:

i) an antifoam;

ii) a biocide;

iii) a first dispersant;

iv) fire retardant material selected from 1) aluminium trihydroxide coated with zinc hydroxy stannate added over a period of about 3 minutes and 2) aluminium trihydroxide and zinc hydroxy stannate)

v) a thickener; and

vi) water; to form a mixture; and

c) dispersing the mixture to form the millbase;

d) adding to the millbase:

i) fly ash having hollow alumina-silicate spheres;

ii) acrylic polymer latex made by an emulsion polymerization process having a monomer composition of methyl methacrylate/2-ethyl hexyl acrylate/acrylic acid of weight ratio 50.5/48.5/1.0, respectively, with a calculated Tg of 6.4° C. and solids content of 50% by weight;

iii) a thickener different from the first thickener,

iv) glass fibers or calcium carbonate; and

v) a third thickener to form the coating composition.

17. A method of forming a coated substrate comprising:

a) providing a substrate

b) applying onto at least a portion of the substrate at least one layer of a coating composition comprising:

a halogen-free fire retardant coating composition comprised of:

i) film forming polymer

ii) inorganic fire retardant material

characterised in that the fire retardant material comprises a combination of fire retardant filler particles and a metal stannate, a metal hydroxy stannate or a combination thereof, wherein the overall PVC of the composition is from 75 to 97%; and

c) allowing the least one layer to dry.