Patent GB-1392560-A (GB)
Title: Laminations
IPC: B32B17/00
Filed: 1972-09-18
Abstract: 1392560 Laminated glass PPG INDUSTRIES Inc 18 Sept 1972 [16 Sept 1971 (3)] 43111/72 Heading B5N A method of making a transparent laminated window comprising a smoothly surfaced layer of plastics laminated to a sheet of glass comprises forming an assembly comprising a sheet of glass, a preformed sheet of a polyvinyl butyral or a polyurethane having approximately uniform thickness throughout its entire extent and a glass mould conforming to the shape of the glass sheet, the preformed sheet being interposed between the glass sheet and the glass mould with a parting material that is separable from at least one of the glass mould and the preformed sheet interposed between the preformed sheet and the mould, maintaining the assembly under a pressure of at least 50 lbs. per square inch and a temperature of approximately 200 to 400 F. for sufficient time to laminate the preformed sheet to the glass sheet, reducing the pressure and temperature and removing the mould from the laminated assembly of glass sheet and preformed sheet. In a first embodiment, the plastics material is thermoplastic and is first assembled with the glass sheet to form a sub-assembly which is then applied to a glass mould more rigid than the preformed sheet throughout the laminating cycle and having a smooth rigid operative surface. In a second embodiment, a preformed polyurethane sheet having a thickness of between 1 mil. and 100 mils. is assembled with a glass sheet of a thickness of from 50 mils. and 250 mils. to form a sub-assembly. In a third embodiment is preformed sheet of thermoplastic polyvinyl butyral or polyurethane is interposed between a glass sheet and a glass mould having a narrow peripheral groove, a parting agent being interposed between the preformed sheet and the mould, the assembly is subjected to a temperature of 200 to 350 F. and a pressure of 50 to 250 lbs. per square inch, a prying tool is inserted into the peripheral space between the mould and the preformed sheet and the mould is removed by continuing to widen and enlarge the peripheral space inwardly. In a fourth embodiment, a parting material which adheres to the mould but not to the preformed sheet is applied to the mould prior to assembly of the components and the pressure and temperature applied are as set forth on the third embodiment. In a fifth embodiment, the preformed sheet is a thermoplastic polyvinyl butyral or polyurethane, the glass sheet is curved, the glass mould is more rigid than the preformed sheet throughout the laminating temperature cycle, has a shaping surface sheet conforms to the shape of the curved glass sheet and has physical properties compatible with those of the curved glass sheet through the temperature range applied during lamination; the parting agent is non-adherent both to the mould and the preformed sheet and the assembly is subjected to a temperature of 200 to 400 F. and a pressure of more than 50 lbs. per square inch. The method of the invention preferably includes the step of removing air trapped between the interfaces of the assembly before pressure is applied, e.g. by application of vacuum to the assembly contained in a flexible bag, lamination being effected by subjecting the bag to heat and pressure in an autoclave. An adhesive may be applied to at least one of the surfaces to be laminated. When a curved glass sheet is used, it is preferred that the preformed sheet is bonded to the concave surface of the glass sheet. Many suitable polyvinyl butyral and polyurethane resins and types of glass which may be used are specified. The parting agent may be a polysiloxane which may be formed in situ on the mould, a polyethylene terephthalate film, polyvinyl fluoride or a metal or metal oxide coating on the operative surface of the mould. The process of the invention may be used for the production of a multilayer laminate.