Sulfonated aliphatic-aromatic copolyesters

A method of improving the biodegradability and polar solvent solubility of a polyester, comprising forming the polyester from

• (a) about 20 to about 60 mole percent based on the total moles of aromatic dicarboxylic acid or ester, of one or more of isophthalic dicarboxylic acid or an alkyl diester thereof,
• (b) about 40 to about 80 mole percent based on the total moles of aromatic dicarboxylic acid or ester, of one or more of terephthalic acid, an alkyl diester thereof, 2,6-naphthalene dicarboxylic acid, or an alkyl diester thereof,
• (c) about 15 to about 60 mole percent based on the total moles of dicarboxylic acid or ester, of one or more linear aliphatic dicarboxylic acids or an alkyl diester thereof,
• (d) about 0.1 to about 5 mole percent based on the moles of total dicarboxylic acid or ester, of one or more alkali or alkaline earth metal salts of 5-sulfoisophthalic dicarboxylic acid or an alkyl diester thereof,
• (e) about 90 to 100 mole percent based on the total amount of glycols, of one or more linear aliphatic glycols, and
• (f) 0 to about 10 mole percent based on the total amount of glycols of one or more of di(ethylene glycol) and tri(ethylene glycol);
• such that said polyester is amorphous, insoluble in water and soluble in polar organic solvents.

A method of forming a film or coating that comprises solvent casting or solvent coating a an amorphous polyester comprising:

• (a) about 20 to about 60 mole percent based on the total moles of aromatic dicarboxylic acid or ester, of one or more of isophthalic dicarboxylic acid or an alkyl diester thereof,
• (b) about 40 to about 80 mole percent based on the total moles of aromatic dicarboxylic acid or ester, of one or more of terephthalic acid, an alkyl diester thereof, 2,6-naphthalene dicarboxylic acid, or an alkyl diester thereof,
• (c) about 15 to about 60 mole percent based on the total moles of dicarboxylic acid or ester, of one or more linear aliphatic dicarboxylic acids or an alkyl diester thereof,
• (d) about 0.1 to about 5 mole percent based on the moles of total dicarboxylic acid or ester, of one or more alkali or alkaline earth metal salts of 5-sulfoisophthalic dicarboxylic acid or an alkyl diester thereof,
• (e) about 90 to 100 mole percent based on the total amount of glycols, of one or more linear aliphatic glycols, and
• (f) 0 to about 10 mole percent based on the total amount of glycols of one or more of di(ethylene glycol) and tri(ethylene glycol);
• said polyester being insoluble in water and soluble in polar organic solvents.