Abstract: The present invention provides the structure of a multilayered unit for windows, comprising a plurality of planar members, a flexible film disposed between, and spaced from, two of said planar members, and a stretching member capable of developing elasticity for stretching the flexible film taut by imparting thereto a force in a direction angularly displaced to the film surface of the said flexible film extending at least over that region of said planar members which forms a window, and the planar member present on at least one side of the flexible film being transparent or semi-transparent.The present invention also provides a multilayered unit for windows and a multilayered window having the same stretching member as in the above structure.

Abstract: A process for purifying beta-lactones, which comprises contacting a beta-lactone selected from the group consisting of alpha, alpha-dimethyl-beta-propiolactone, beta-propiolactone and a mixture of these with a solid alkaline earth metal hydroxide.