Method for making a film of polyvinyl butyral used for making laminated glass

Abstract

Method for making laminated glass, whereby a film (2) of polyvinyl butyral is applied between the glass layers (1) whose surface has obtained a roughness at a temperature above 120.degree. C., whereby the glass layers (1) and the film (2) are pressed together at a considerably lower temperature so as to remove the air in between, after which the formed laminate is put in an autoclave under pressure and at a temperature higher than the temperature of the pressing together, characterized in that a film (2) of polyvinyl butyral is used which has elongated threadbare patches (3) which form levels on either side in the polyvinyl butyral surface which extend across the film (2) and which were provided at a lower temperature, however, than the temperature at which the roughness was formed, so that they will quickly disappear at a relatively low temperature because of the viscoelastic behaviour of the polyvinyl butyral, and in that these threadbare patches (3) are made to disappear after or already during the pressing together, but in any case before the laminate is put in the autoclave.

Dependencies are inferred from the claim text.