Highly filled undercoat for non-stick finish

Abstract

The invention relates to a composition applicable as a undercoat for a non-stick coating on a substrate, comprising (a) inorganic filler of ceramic particles, the particles having an average particle size of 1 micrometer or less and an aspect ratio of not greater than 2.5, (b) adhesion promoter wherein the weight proportion of inorganic filler to adhesion promoter is in the range of 5:1 to 1.7:1, and (c) from 0 to 25 wt. % of a fluoropolymer based on the weight of the composition of the undercoat layer after baking.

What is claimed is:  
     
         1 . Composition applicable as a undercoat for a non-stick coating on a substrate, comprising (a) inorganic filler of ceramic particles, the particles having an average particle size of 1 micrometer or less and an aspect ratio of not greater than 2.5, (b) adhesion promoter wherein the weight proportion of inorganic filler to adhesion promoter is in the range of 5:1 to 1.7:1, and (c) from 0 to 25 wt. % of a fluoropolymer based on the weight of the composition of the undercoat layer after baking.  
     
     
         2 . The composition of    claim 1    wherein the amount of fluoropolymer based on the weight of the composition of the undercoat after baking is from 1 to 15 wt. %.  
     
     
         3 . The composition of    claim 1    wherein the particle size of the ceramic particles is in the range of 0.1 micrometer to 1.0 micrometer.  
     
     
         4 . The composition of    claim 1    wherein the fluoropolymer is non-melt-fabricable.  
     
     
         5 . The composition of    claim 1    wherein the fluoropolymer is a blend of non melt-fabricable fluoropolymer with a melt viscosity in the range from 1×10 7  to 1×10 11  Pa.s and melt fabricable fluoropolymer with a viscosity in the range from 1×10 3  to 1×10 5  Pa.s.  
     
     
         6 . The composition of    claim 1    wherein said adhesion promoter is at least one of polyamide imide, polyimide, polyarylene sulfide and polyethersulfone resins.  
     
     
         7 . The composition of    claim 1    wherein the inorganic filler is selected from a group of inorganic nitrides, carbides, borides and oxides.  
     
     
         8 . The composition of    claim 7    wherein the inorganic filler is aluminum oxide.  
     
     
         9 . The composition of    claim 1    in the form of a baked layer on a substrate.  
     
     
         10 . The composition of    claim 9    wherein the substrate prior to coating is smooth.  
     
     
         11 . A substrate coated with a non-stick coating, said coating comprising an undercoat and a fluoropolymer overcoat, said undercoat containing (a) inorganic filler of ceramic particles, the particles having a particle size of 1 micrometer or less and an aspect ratio of not greater than 2.5, (b) at least one adhesion promoter wherein the weight proportion of inorganic filler to adhesion promoter is in the range of 5:1 to 1.7:1, and (c) from 0 to 25 wt. % of a fluoropolymer based on the weight of the composition of the undercoat layer after baking.  
     
     
         12 . The coated substrate of    claim 11    wherein said undercoat contains from 1 to 15 wt. % of a fluoropolymer based on the weight of the composition of the undercoat after baking.  
     
     
         13 . The coated substrate of    claim 11    wherein the undercoat is a base coat on said substrate.  
     
     
         14 . The coated substrate of    claim 11    wherein the undercoat is a primer on said substrate.  
     
     
         15 . The coated substrate of    claim 11    wherein the undercoat is a primer applied to a base coat.  
     
     
         16 . The coated substrate of    claim 11    wherein said substrate prior to coating is smooth.  
     
     
         17 . The coated substrate of    claim 11    which is a metal substrate.  
     
     
         18 . The coated substrate of    claim 17    wherein at least a portion of the metal substrate is coated with a ceramic coating.  
     
     
         19 . The coated substrate of    claim 11    wherein said overcoat comprises an intermediate coating and a topcoat.  
     
     
         20 . The coated substrate of    claim 11    wherein said overcoat comprises a fluoropolymer which is a non-melt fabricable fluoropolymer with a melt viscosity in the range from 1×10 7  to 1×10 11  Pa.s.  
     
     
         21 . The coated substrate of    claim 11    wherein said overcoat comprises a fluoropolymer which is a blend of a non-melt fabricable fluoropolymer with a melt viscosity in the range from 1×10 7  to 1×10 11  Pa.s and melt-fabricable fluoropolymer with a melt viscosity in the range from 1×10 3  to 1×10 5  Pa.s.  
     
     
         22 . The coated substrate of    claim 11    wherein said overcoat contains in addition inorganic filler of ceramic particles, the particles having an average particle size of 1 micrometer or less.  
     
     
         23 . The coated substrate of    claim 22    wherein said overcoat contains in addition organic adhesion promoter.  
     
     
         24 . The coated substrate of    claim 23    wherein said adhesion promoter is at least one of polyamide imide, polyimide, polyarylene sulfide and polyethersulfone resins.