Method for producing films based on plasticized polyvinyl acetal having a predefined viscosity
AssigneeKuraray Europe GmbH
InventorsMichael Haerth, Daniel Wenzlik
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Abstract
Plasiticized polyvinylacetal films with greater film-to-film uniformity are produced by a process of extruding a melt stream containing a polyvinyl acetal and a plasticizer at 150-250° C., the film having a predefined melt viscosity at 60-170° C., by providing a first melt stream of at least a first plasticizer and a first polyvinyl acetal resin and measuring its melt viscosity at 60-170° C. online; and adjusting the 60-170° C. melt viscosity by adding a second plasticizer and/or a second polyvinyl acetal resin to the first melt stream in an amount to provide a second melt stream with a melt viscosity at 60-170° C. having a difference of at most 20% to the predefined melt viscosity at 60-170° C.
Claims18
A process for reducing fluctuations in melt viscosity of a plasticized polyvinyl acetal product at a first temperature greater than or equal to 60° C. and less than or equal to 170° C., where the plasticized polyvinyl acetal is melted and extruded at a second temperature which is an extrusion temperature which is different from said first temperature, and is greater than or equal to 150° C. and less than or equal to 250° C., the process comprising:
- a) establishing a predefined value of melt viscosity of plasticized polyvinyl acetal at said first temperature;
- b) providing a first composition comprising at least one polyvinyl acetal and at least one plasticizer;
- c) melting and extruding said first composition at the extrusion temperature and measuring the melt viscosity at said first temperature;
- d) providing a second composition different from the first composition, the second composition comprising one or more polyvinyl acetals, one or more plasticizers, or a mixture thereof;
- e) adjusting the melt viscosity at said first temperature by varying the amount of said second composition added to said first composition in the extruder to form an adjusted composition,
- wherein the melt viscosity of the adjusted composition is within ±20% of the predefined melt viscosity at said first temperature, measured under the same conditions as step c).
Dependencies are inferred from the claim text.