high barrier transparent films
AssigneeHoechst Celanese Corporation
InventorsSubhash Makhija, M. Ishaq Haider, Edward C. Chenevey, Michael Jaffe
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Abstract
A process for making a transparent film comprising a liquid crystalline polymer, and a transparent film made thereby having high barrier properties. In this process, the LCP is dissolved in an appropriate solvent, then cast into a film at ambient or near-ambient temperatures. The film optionally may be dried at elevated temperatures and/or reduced pressures to remove the solvent. The film is then annealed at a temperature between the glass transition temperature (T.sub.g) and the melting point temperature (T.sub.m) of the polymer. The result is a highly transparent film having liquid crystalline morphology and high barrier properties.
Claims13
A process for making a transparent film that comprises a liquid crystalline polymer having repeat units derived from p-hydroxybenzoic acid, hydroquinone, and isophthalic acid, comprising the steps of:
- dissolving said liquid crystalline polymer at a temperature below about 40.degree. C. in a solvent in which said polymer is soluble, which solvent is selected from the group consisting of:
- an aliphatic alcohol having a boiling point below about 100.degree. C. and a pK.sub.a below about 10;
- a co-solvent of trifluoroacetic acid and methylene chloride;
- a co-solvent of pentafluorophenol and 1,1,1,3,3,3-hexafluoro-2-propanol;
- and mixtures thereof;
- forming an amorphous film from said solution at a temperature below about 40.degree. C.;
- annealing said amorphous film at a temperature between the glass transition temperature and the melting point temperature of said polymer;
- and
- stretching said annealed film at least 25% of its length in both the machine direction and the transverse direction, at a temperature below the melting point temperature of said polymer.
Dependencies are inferred from the claim text.