Polyester resin compositions and processes for the preparation thereof

A polyester resin composition comprising a thermoplastic polyester resin and a silane-treated foliated phyllosilicate, wherein the silane-treated foliated phyllosilicate is prepared by introducing an organo-silane represented by the following general formula (I):

• YnSiX4−n (1)
• wherein n denotes an integer of 0 to 3, Y denotes a hydrocarbon group having 1 to 25 carbon atoms, X denotes a hydrolyzable group or a hydroxyl group, n units of Y or (4−n) units of X may, respectively, be the same or different if n or (4−n) is at least 2,
• into a swellable phyllosilicate, and wherein the maximum layer thickness of the silane-treated foliated phyllosilicate in the polyester resin composition is more than 200 Å and up to 1,800 Å;
• wherein said hydrocarbon group optionally comprises at least one of the following:
• an ester bond, an ether bond, an epoxy group, an amino group, a carboxyl group, a carbonyl group, an amide group, a mercapto group, a sulfonyl bond, a sulfinyl bond, a nitro group, a nitroso group, a nitrile group, a halogen atom, and a hydroxyl group;
• and wherein the dispersing particle number [N] of the silane-treated foliated phyllosilicate particles present in a 100 m2 area of the polyester resin composition is at least 30 based on unit proportion.