Enhanced oxygen barrier performance from modification of ethylene vinyl alcohol copolymers (EVOH)

[0126]To a reactor equipped with a mechanical stirrer, nitrogen inlet and external heating, 250 parts water, 500 parts acetic acid, 500 parts ethyl alcohol, and 100 parts poly(ethylene vinyl alcohol) (68% alcohol content) were charged. The mixture was heated to gentle reflux at 90° C. to allow the polymer to completely dissolve in the solution. Then, 5 parts tetrahydrobenzaldehyde were charged. This was followed by charging 2 parts sulfuric acid drop-wise into the content. The reaction content was maintained at 90° C. under stirring for 6 hours. At the end of the reaction, the solution was allowed to cool to room temperature overnight. The solution was neutralized by adding 60 mL of sodium acetate solution (25%). It was stirred for about 1 hour. The reaction solution was slowly added into 4 L acetone under vigorous stirring to result in precipitation. The product was washed in acetone for 2 hours under vigorous agitation, and the product was collected in a white fibrous form by filtrat

[0127]Similarly to Example 1, 500 parts water, 500 parts ethyl alcohol, 100 parts poly(ethylene vinyl alcohol) (68% alcohol content), and 10 parts tetrahydrobenzaldehyde were used. This gave 113 g product: Tg=60° C.; Tm=110° C. (DSC, 10° C. / min).

[0128]Similarly to Example 1, 500 parts water, 500 parts ethyl alcohol, 100 parts poly(ethylene vinyl alcohol) (68% alcohol content), and 20 parts tetrahydrobenzaldehyde were used. This gave 120 g product: Tg=64° C. (DSC, 10° C. / min).