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.

Description

TECHNICAL FIELD[0001]The invention relates to polyvinyl acetals with high flowability, a process for their preparation and their use in plasticizer-containing films.PRIOR ART[0002]Polyvinyl acetals, in particular polyvinyl butyral have long been known in the fields of architectural and automobile construction as a basic material for the production of intermediate layer films for laminate safety glasses as well as adhesive films for photovoltaic modules.[0003]Polyvinyl acetals and their reaction products are materials produced on an industrial scale that, over the years, have had to be adapted to many different application profiles. The molecular structure of the polymer chain was studied in this connection with regard to composition (degree of acetalisation, residual acetate content and residual alcohol content), chain length, aldehyde used and compatibility with different plasticizers. The object of these studies is often merely the polyvinyl acetal however, and not the processabil...

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Benefits of technology

[0032]In a further variant of the invention the polyvinyl acetals according to the invention have increased molecular weight and increased solution viscosity, which must lie within the above limits, as a result of crosslinking via carboxyl groups, polyaldehydes, glutardialdehydes or glyoxylic acid.

Problems solved by technology

The object of these studies is often merely the polyvinyl acetal however, and not the processability or adjustment of specific properties of the reaction products.

A lack of flowability of films can be offset to a certain extent by raising processing temperatures or extending processing times. However, in industrial processes the increase in processing temperature and / or the extension of machine cycle times is undesirable since the energy efficiency or capacity utilisation of the production plants is thus lowered.

However, this is not always possible for reasons of compatibility with the respective polyvinyl acetal and generally also leads to increased inherent adhesiveness of the film.

This reduces its processability and is generally undesirable.

Furthermore, the flowability of the polyvinyl acetals described in GB 2007677 improves with an increasing degree of acetalisation (butyraldehyde drained weight), which has a detrimental effect on the obtainment of highly acetalised polyvinyl acetals with a degree of acetalisation over 75 mol %.

However, in this instance a low acetalisation temperature is used in such a way that the sequence of repeating units in the polyvinyl acetal is not adjusted to the thermodynamic balance.

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