Process for the continuous production of high molecular weight polyester resin

Claim 2

Process for the continuous production of high molecular weigh polyester resin from polyester resin having a lower molecular weight, in which the resin is blended in a molten state with an additive adapted to accellerate the achievement of high viscosity, transformed into a granulate and then treated in a solid state polycondensation reactor, characterized in that the additive is a dianhydride of an aromatic tetracarboxylic acid.

Claim 3

Process according to claim 1, characterized in that the additive is selected from the group consisting of pyromellitic dianhydride, benzophenone dianhydride, 2,2 - bis (3,4-dicarboxyphenyl) propane dianhydride, 3,3′, 4,4′ - biphenyltetracarboxylic acid dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3, 4 - dicarboxyphenyl) thioether diahydride, bisphenol A bisether dianhydride, 2,2 - bis (3,4-dicarboxylphenyl) hexafluoropropane dianhydride, 2, 3, 6, 7 - naphtalenetetracarboxylic acid dianhydride, bis (3, 4 - dicarboxyphenyl) sulfone dianhydride, 1, 2, 5, 6 - naphthalenetetra­carboxylic acid dianhydride, 2,2′, 3,3′ - biphenyl­tetracarboxylic acid dianhydride, hydroquinone bisether dianhydride, bis (3,4 - dicarboxyphenyl) sulfoxide dianhydride, 3, 4, 9, 10 - perylene tetracarboxylic acid dianhydride and mixtures thereof.

Claim 4

Process according to claim 2, characterized in that the additive is pyromellitic dianhydride or 3,3′, 4,4′ benzophenonetracarboxylic dianhydride or mixture thereof.

Claim 5

Process according to claim 1, characterized in that the blending is performed in a counter-rotating non-intermeshing vented twin screw extruder.

Claim 6

Process according to claim 4, characterized in that the anhydride is firstly dispersed in a polyester powder and then is fed to the extruder.

Claim 7

Process according to claim 4, characterized in that the pressure in the extruder is below 150 torrs.

Claim 8

Process according to claim 4 or 5, characterized in that the temperature of the melt polyester in the extruder is comprised between 200° and 350°C and in that the residence time in the extruder is comprised between 30 and 120 sec.

Claim 9

Process according to anyone of the preceeding claims, characterized in that the dianhydride fed to the extruder is comprised between 0,1 to 1% by weight with respect to the polyester resin.

Claim 10

Process for upgrading recycled PET, particularly from crashed bottles, characterized in that the recycled PET is blended in a molten state with a dianhydride of an aromatic tetracarboxylic acid, is transformed into a granulate and then is treated in a solid state polycondensation reactor.

Claim 11

Process for upgrading recycled PET, particularly from crashed bottles, characterized in that the recycled PET is blended in a molten state with a dianhydride of an aromatic tetracarboxylic acid, is transformed into a granulate and then is treated in a solid state polycondensation reactor.