Copolymers of a polyvinyl butyral backbone with polylactic acid grafts and their compounds are disclosed, which can be used to produce clear, flexible and ductile bio-based films. The copolymers are amorphous and have been shown to maintain clarity, flexibility, and ductility after continuous exposure to thermal aging at 80 C. for one week.

An ethylene-vinyl alcohol copolymer has an ethylene content of 20 to 60 mol % and includes a carboxylic acid group and a lactone ring group present at terminals thereof, wherein the molar concentration (Y/Z) of a lactone ring molar content (Y) to a sum (Z) of a carboxylic acid molar content (X) and the lactone ring molar content (Y) is not less than 58 mol %. The ethylene-vinyl alcohol copolymer is excellent in high-temperature thermal stability substantially without thermal decomposition, and is free from odor emanation and coloration even if being processed at a higher temperature.

An ethylene-vinyl alcohol copolymer has an ethylene content of 20 to 60 mol % and includes a carboxylic acid group and a lactone ring group present at terminals thereof, wherein the molar concentration (Y/Z) of a lactone ring molar content (Y) to a sum (Z) of a carboxylic acid molar content (X) and the lactone ring molar content (Y) is not less than 58 mol %. The ethylene-vinyl alcohol copolymer is excellent in high-temperature thermal stability substantially without thermal decomposition, and is free from odor emanation and coloration even if being processed at a higher temperature.

An ethylene-vinyl alcohol copolymer has an ethylene content of 20 to 60 mol % and includes a carboxylic acid group and a lactone ring group present at terminals thereof, wherein the molar concentration (Y/Z) of a lactone ring molar content (Y) to a sum (Z) of a carboxylic acid molar content (X) and the lactone ring molar content (Y) is not less than 58 mol %. The ethylene-vinyl alcohol copolymer is excellent in high-temperature thermal stability substantially without thermal decomposition, and is free from odor emanation and coloration even if being processed at a higher temperature.

A curable composition which enables the formation of a cured product having a low dielectric constant, low dielectric loss tangent, high heat resistance, good elongation and excellent tensile strength and which has excellent film forming properties; a cured product of the curable composition; and a method for forming an insulating film using the curable composition. This curable composition contains a modified maleimide compound, a radical generator and a thiol compound. The curable composition may contain a photo-radical generator as the radical generator. The curable composition may contain a protonic acid.

A curable composition which enables the formation of a cured product having a low dielectric constant, low dielectric loss tangent, high heat resistance, good elongation and excellent tensile strength and which has excellent film forming properties; a cured product of the curable composition; and a method for forming an insulating film using the curable composition. This curable composition contains a modified maleimide compound, a radical generator and a thiol compound. The curable composition may contain a photo-radical generator as the radical generator. The curable composition may contain a protonic acid.

A novel acrylic polymer is provided. The novel acrylic polymer is an acrylic polymer which has a lactone ring structure in the main chain and has a melt flow rate of 2 g/10 minutes or more as measured at 230 C. under a load of 3.8 kg according to JIS K 7210.

A novel acrylic polymer is provided. The novel acrylic polymer is an acrylic polymer which has a lactone ring structure in the main chain and has a melt flow rate of 2 g/10 minutes or more as measured at 230 C. under a load of 3.8 kg according to JIS K 7210.