Laminated metal sheet
AssigneeCMB Foodcan plc
InventorsPeter J. Heyes, Nicholas J. Middleton
Life of this patent
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Abstract
A laminated metal sheet, the metal sheet having adhered on at least one major surface thereof a film of a non-crystalline polyester, and a process for the preparation thereof. The laminated metal sheet is particularly useful for forming into drawn and wall ironed (DWI) cans. The laminate is also useful for forming other non-retorted packaging components.
Claims32
A process for making a laminate of metal and non-crystalline polyester, characterized by the steps of:
- (i) providing a sheet of metal and monolayer film of biaxially-oriented polyester having a semi-crystalline structure,
- (ii) heating the sheet of metal to a temperature T.sub.1 above the melting point of the film,
- (iii) applying the film to the sheet under pressure and under conditions such that the outer surface of the film remains below its melting point to form an initial laminate,
- (iv) heating the initial laminate by indirect means so that the film is raised to a temperature T.sub.2 above its melting point, and after holding at such elevated temperature,
- (v) quenching rapidly the heated initial laminate to a temperature below the glass transition point of the polyester to form the aforesaid laminate of metal and non-crystalline polyester, by passage through a curtain of water.
A process for making a laminate of metal and non-crystalline polyester characterized by the steps of:
- (a) providing a composite film comprising an inner layer of polyester (A1) and an outer layer of polyester (A2) in which at least one of said polyester layers is a biaxially oriented polyester having a semi-crystalline structure;
- (b) heating the sheet metal to a temperature T.sub.1 above the softening point of the inner layer;
- (c) applying the composite film to the heated sheet metal under pressure and under conditions such that the outer surface layer remains below its melting point to make an initial laminate;
- (d) heating the initial laminate by indirect means to a temperature T.sub.2 above the melting point of both the inner and outer layers to make a laminate;
- and after holding at such elevated temperature
- (e) quenching the laminate rapidly to a temperature below the glass transition points of the polyesters to achieve a laminate of sheet metal and polyesters in which the film in the laminate is non-crystalline.
A laminated metal sheet comprising sheet metal, one or both major surfaces having adhered directly thereto a composite polyester film, wherein the composite polyester film comprises:
- (a) an inner polyester layer of single polyester having a softening point below 200.degree. C. and a melting point below 250.degree. C. but above 150.degree. C.;
- and
- (b) an outer polyester layer having a melting point above 220.degree. C. and formed from a biaxially oriented polyester having a semi-crystalline structure;
- wherein:
- (c) the polyester film is substantially non-crystalline;
- and
- (d) the polyester film has an intrinsic viscosity between 0.5 and 1.1;
- such that the laminated metal sheet is suitable for making drawn and wall ironed cans.
A laminated metal sheet comprising sheet metal, one or both major surfaces having adhered directly thereto a composite polyester film, characterized in that the composite polyester film is substantially non-crystalline and comprises an inner polyester layer and an outer polyester layer, wherein the outer polyester layer has a higher melting temperature than the inner polyester layer and at least one of the layers has been formed from a biaxially oriented polyester having a semi-crystalline structure.
Dependencies are inferred from the claim text.