Barrier and film properties of plastisol coatings, a water free coating application based on mixtures of starch, poly(vinyl alcohol) and poly(alkyl methacrylate)

摘要

Plastisol coatings based on starch and poly(vinyl alcohol) were investigated. Dry powders based on two different ratios of these two water-soluble polymers were prepared by spray drying aqueous polymer solutions. An oxidized and hydroxypropylated potato starch and a poly(vinyl alcohol) grade with a degree of hydrolysis of 72.5% were used. Poly(alkyl methacrylate) was used in order to improve the water vapour barrier of the coated materials. Starch-containing plastisol pastes were produced by two different routes: (1) by adding a liquid plasticizer (glycerol or poly(ethylene glycol)) to the starch/poly(vinyl alcohol)-based powder and (2) by mixing the dry starch/poly(vinyl alcohol)-based powder with the dry poly(alkyl methacrylate) powder and subsequently adding a mixture of liquid plasticizers (glycerol and dipropylene glycol benzoate) to the powder mixture. Free plastisol films and coated papers were produced. Two different base-papers were investigated; greaseproof paper and paperboard. It was possible to produce pure starch/poly(vinyl alchohol) plastisol coatings as well as plastisol coatings based on a mixture of incompatible polymers. Stratified structures created by a double layer coating operation were also investigated. In the case of the double coatings, the first plastisol layer was a pure starch/poly(vinyl alcohol) plastisol according to route 1 and the second layer was a pure poly(alkyl methacrylate) plastisol. The plastisol coatings resulted in improvements in the water vapour and oxygen barrier properties.