Vinyl Acetal Polymers

Abstract

Vinyl acetal polymers are terpolymers, with units of vinyl acetate, vinyl alcohol, and vinyl acetal reflecting the three reactions required for their manufacture. Manufacture involves several stages including vinyl acetate polymerization and either sequential or concurrent hydrolysis of poly(vinyl acetate) to poly(vinyl alcohol) and acetalization with an aldehyde in the presence of an acid catalyst. Only poly(vinyl butyral) and to a lesser extent poly(vinyl formal) continue to be made in sizeable commercial quantities. These polymers form hard, unpliable materials that are difficult to process without using solvents or plasticizers. Plasticized poly(vinyl butyral) interlayer for laminated safety glass is by far the largest single application for this class of polymers. Poly(vinyl butyral) provides flexible toughness over a wide range of temperatures and at a lower cost than vinyl acetal polymers derived from longer chain aldehydes. Where stiffer performance at higher temperatures is required, poly(vinyl formal) provides significant property advancement. Applications for vinyl acetal resins make use of their optical clarity, high pigment and filler binding capacity, and excellent adhesion to a variety of surfaces.

Tear fluid collection in dogs and cats using ophthalmic sponges

“…Most ophthalmic sponges are made of either cellulose or polyvinyl acetal (PVA) . Cellulose is a natural hydrophilic material, while PVA is a bioengineered polymer formed by hydrolysis of polyvinyl acetate (hydrophobic) into polyvinyl alcohol (hydrophilic) and subsequent acetalization . The variable affinity of these materials for water impacts their ability to absorb tear fluid, but could also interfere with the subsequent release and recovery of the fluid.…”

Process Intensification of the Synthesis of Poly(vinyl butyral) Using a Microstructured Chemical System

“…Poly­(vinyl butyral) (PVB) is an important polymer product synthesized from the reaction of poly­(vinyl alcohol) (PVA) and n-butanal catalyzed by H + , and is widely used in optics, seals, and bond areas, especially laminated safety glass for automobile windshields, for its refractive index of glass, flexibility, low glass-transition temperature, strong adhesion, and excellent mechanical strength . In recent years, the applications of PVB in the areas of photovoltaic cell encapsulation, , ultrafiltration membrane preparation, , and drug delivery , have also driven the synthesis of PVB products with high purity and low cost.…”

Reverse Dissolution as a Route in the Synthesis of Poly(vinyl butyral) with High Butyral Contents

“…PVB may be synthesized using either poly(vinyl acetate) or poly(vinyl alcohol) (PVA) as a starting material. 1 In the former, a one-step method is applied: the alcoholysis of poly(vinyl acetate) and the acetalization of the resulting poly(vinyl alcohol), as a result of the alcoholysis, proceed simultaneously. This method yields PVB with high contents of impurities; in the latter, where PVA is used as a starting material, 1 butyl aldehyde is typically added into the solution of PVA (usually called forward feeding) to achieve the acetalization using an acid as a catalyst.…”

“…1 In the former, a one-step method is applied: the alcoholysis of poly(vinyl acetate) and the acetalization of the resulting poly(vinyl alcohol), as a result of the alcoholysis, proceed simultaneously. This method yields PVB with high contents of impurities; in the latter, where PVA is used as a starting material, 1 butyl aldehyde is typically added into the solution of PVA (usually called forward feeding) to achieve the acetalization using an acid as a catalyst. Depending on the form of PVB material during the acetalization process, two approaches are used, i.e., precipitation and dissolution.…”

“…Depending on the form of PVB material during the acetalization process, two approaches are used, i.e., precipitation and dissolution. 1 For the precipitation approach, butyl aldehyde is added and reacts with the PVA aqueous solution. The product of PVB precipitates after the acetalization reaches a certain degree.…”