Polyfvinyl acetate dispersions

Butyl glycolate reduces the viscosity of alkyd resin paints. It improves the flow properties and gloss in air-drying and oven-drying paints, especially in coil coating and leather lacquers. It is also used to lower the film-forming temperature in polyfvinyl acetate) dispersions. 

Over the past years considerable attention has been paid to the dispersing system since this controls the porosity of the particle. This is important both to ensure quick removal of vinyl chloride monomer after polymerisation and also to achieve easy processing and dry blendable polymers. Amongst materials quoted as protective colloids are vinyl acetate-maleic anhydride copolymers, fatty acid esters of glycerol, ethylene glycol and pentaerythritol, and, more recently, mixed cellulose ethers and partially hydrolysed polyfvinyl acetate). Much recent emphasis has been on mixed systems. 

An example is shown in Fig. 18-17, where v and attenuation (= 8.686a) at 2 X 10 Hz are plotted against temperature for polyfvinyl acetate), as reported by Thurn and Wolf. Three zones of dispersion are apparent. The one at 93 C undoubtedly represents the primary transition from glasslike to rubberlike consistency, in which o drops by about 50% because of the virtual disappearance of the jG term in equation 13 as it becomes smaller than K by several orders of magnitude. But... 

Lamination of Paper and Board. Adhesives based on starch, dextrin, glutin and poly(vinyl alcohol), and also emulsion adhesives, mainly polyfvinyl acetate), are used for the lamination of paper and board. Only when high initial tack and a lay-flat effect are required are hot glues based on glutin still in use. Starch-based adhesives modified with silicate, casein-stabilized copolymer dispersions, and rubber latices are used in the lamination of paper to aluminum foils. Modified polyacrylate solutions and reactive polyurethane adhesives are used mainly for paper-to-plastic lamination. 

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