Process for preparing a stabilized polyester

A process for the preparation of a stabilized polyester that is low in the generation of aldehydes which comprises reacting one or more diacids with one or more diols in an esterification process, and/or one or more diesters with one or more diols in a transesterification process in the presence of an effective amount of a stabilizer selected from the group consisting of

• a) a polyhydric alcohol of the formula I
• E—(OH)n (I)
• wherein n is 3 to 4000, and
• E is an aliphatic, cycloaliphatic, aromatic or a mono-, di- or poly-sucrose moiety;
• with the proviso that, if n is 3 or 4 and E is an aliphatic moiety, then additionally at least one sterically hindered hydroxyphenylalkylphosphonic ester or monoester is present;
• b) a compound of the formula II
• 29
• wherein
• R1 is hydrogen, C1-C20alkyl, phenyl or C1-C4alkyl substituted phenyl;
• biphenyl, naphthyl, —CH2—O—C1-C20alkyl or —CH2—S—C1-C20alkyl,
• R2 is C1-C20alkyl, phenyl or C1-C4alkyl substituted phenyl;
• biphenyl, naphthyl, —CH2—O—C1-C20alkyl or —CH2—S—C1-C20alkyl, or R1 and R2 together are a radical of the formula III
• 30
• wherein
• R3, R4 and R5 independently of each other are C1-C20alkyl, phenyl or C1-C4alkyl substituted phenyl,
• c) a sterically hindered amine which comprises at least a radical of the formula IV or V
• 31
• wherein
• G is hydrogen or methyl, and
• G1 and G2 are hydrogen, methyl or together are oxygen,
• d) a polyacrylamide of the formula VI
• 32
• wherein
• R′1 and R′2 are independently of each other hydrogen, C1-C20alkyl, phenyl or C1-C4-alkyl substituted phenyl;
• biphenyl, naphthyl, —CH2—O—C1-C20alkyl or —CH2—S—C1-C20alkyl;
• or R′1 and R′2 together are a radical of the formula III
• 33
• R′1 and R′2 together with the nitrogen atom to which they are attached form an unsubstituted or C1-C4alkyl substituted imidazolyl, pyrrolyl, pyrrolidonyl, piperidinyl or piperazinyl ring;
• and
• q is 5 to 300000;
• or
• a polyacrylamide copolymer wherein the comonomer is an acrylic acid, an acrylic acid salt or an acrylic ester;
• or
• e) hydroxylamines and/or nitrones.