Patent GB-858053-A (GB)
Title: Improvements in or relating to the extrusion of polyvinyl acetal resin sheets
IPC: B29C48/03
Filed: 1957-01-23
Abstract: Roughened polyvinyl acetal resin sheets having reduced premature adhesion are made by forcing a compressed, plasticized polyvinyl acetal resin at a temperature of at least 164 DEG C., and having a superheated water content of 0,6-15,0% of the weight of the plasticized resin, through a sheetforming extrusion die into the atmosphere to release the pressure on the resin and enable the superheated water to emerge from the body of the resin and thereby produce a substantially uniform roughening of the sheet of the order of 46-100 peaks per inch extending 0,2-1,0 mil above the surface. The polyvinyl acetal specified is a butyral, and plasticizers specified are triethylene glycol dihexoate, di (mono ethyl ether of ethylene glycol) adipate, and di-butyl sebacate.  In general the peak height increases and the peak frequency decreases as the water content increases.  In the examples a 7% aqueous slurry of a polyvinyl butyral was prepared, to which was added 41% by weight of the resin of triethylene glycol dihexoate.  The water content was reduced to 15% and the temperature raised to 100-155 DEG C. while filtering and extruding. The required water content was attained in a vacuum zone, and the material was then extruded through a 6 inch sheet die of slit opening of approximately 20 mils and of land length of 1/16 inch.  In the Examples there were the following variables: (i) Water, per cent by weight, 0,6-5,14; (ii) Melt Temperature 164-166 DEG C.; (iii) Die Pressures, 290-500 p.s.i.; and (iv) Take-off, 12,2-39,0 ft./min.  The extruded sheet was then treated to drive off any undesired residual water, powdered, and rolled up on a mandrel.  Use.  Laminated safety glass.ALSO:Roughened polyvinyl acetal resin sheets having reduced premature adhesion are manufactured by forcing a compressed, plasticized polyvinyl acetal resin at a temperature of at least 164 DEG C. and having a superheated water content of 0,6-15,0% of the weight of the plasticized resin through a sheet forming extrusion die into the atmosphere to release the pressure on the resin and enable the superheated water to emerge from the body of the resin and thereby produce a substantially uniform roughening of the sheet of the order of 46-100 peaks per inch extending 0,2-1,0 mil above the surface. The polyvinyl acetal specified is a butycol, and plasticizers specified are triethylene glycol dihexonte, di (monoethyl ether of ethylene glycol) adipate, and dibutyl sebacate.  In general the peak height increases and the peak frequency decreases as the water content increases.  In the examples a 7% aqueous slurry of a polyvinyl butyral was prepared, to which was added 41% by weight of the resin of triethylene glycol dihexoate.  The water content was reduced to 15% and the temperature raised to 100-155 DEG C. by filtering and extruding.  The required water content was obtained in a vacuum zone, and the material was then extruded through a 6 inch sheet of die of slit opening of approx. 20 mls. and of land length 1/16 inch.  In the examples there were the following variables: (1) water, per cent by weight, 0,6-5,14; (ii) melt temperature 164-166 DEG C.; (iii) die pressures, 290-500 p.s.i.; and (iv) take-off, 12,2-39,0 ft. min.  The extruded sheet was then treated to drive off any undesired residual water, powdered, and rolled up on a mandrel.