Polyvinyl acetal with high flowability and plasticizer-containing films produced therewith

Abstract

The invention relates to polyvinyl acetals obtainable by reacting polyvinyl alcohol with at least one aldehyde with a degree of acetalisation of at least 75 mol %, characterised by an OH blockiness of the polyvinyl acetal, defined as a quotient from the number of methylene groups of two adjacent alcohol sequences (VV) and the sum of the number of methylene groups of adjacent alcohol/acetal sequences and acetal/acetal sequences (VB+BB), of more than 0.151, as well as a process for the preparation thereof.

1 . Polyvinyl acetals obtainable by reacting polyvinyl alcohol with at least one aldehyde with a degree of acetalisation of at least 75 mol %, characterised by an OH blockiness of the polyvinyl acetal, defined as a quotient from the number of methylene groups of two adjacent alcohol sequences (VV) and the sum of the number of methylene groups of adjacent alcohol/acetal sequences and acetal/acetal sequences (VB+BB), of more than 0.151. 
     
     
         2 . The polyvinyl acetal according to  claim 1 , characterised by a solution viscosity in a 5% by weight solution in ethanol of less than 75 mPas. 
     
     
         3 . The polyvinyl acetal according to either  claim 1  or  claim 2 , characterised in that butyraldehyde is used for acetalisation of the polyvinyl alcohol. 
     
     
         4 . The polyvinyl acetals according to any one of  claims 1  to  3 , characterised by a residual acetate content of 1.0 to 8 mol %. 
     
     
         5 . A process for preparing a polyvinyl acetal according to  claim 1  by acid-catalysed reaction of at least one polyvinyl alcohol with at least one aldehyde, characterised by the following process steps:
 a) reacting the polyvinyl alcohol with the aldehyde at a temperature of 0 to 20° C., 
 b) completing the reaction of a) by heating the reaction mixture to 68 to 90° C., 
 c) cooling the reaction mixture to 15 to 25° C. and separating the polyvinyl acetal, 
 d) neutralising the polyvinyl acetal separated from the reaction mixture. 
 
     
     
         6 . The process according to  claim 5 , characterised in that the temperature in process step b) is maintained over a period of at least 60 min. 
     
     
         7 . The process according to either  claim 5  or  claim 6 , characterised in that the temperature in process step b) is 68° C. to 80° C. 
     
     
         8 . The process according to any one of  claims 5  to  7 , characterised by the absence of emulsifiers or surfactants. 
     
     
         9 . A use of the polyvinyl acetals according to any one of  claims 1  to  5  for the production of plasticizer-containing films for laminate glasses or photovoltaic modules.