Articles having improved gas barrier properties
View Patent ↗The present invention relates to a blend of sulfo-modified copolyester wherein the diacid is aromatic or cyclic and polyglycolic acid. The blend of sulfo-modified copolyester and polyglycolic acid can be used to prepare containers with good transparency and high gas barrier properties. The preferred sulfo-modified copolyester composition comprises terephthalic acid, isophthalic acid and 5-sulfoisophthalic acid. A method of preparing a blend of sulfo-modified copolyester and polyglycolic acid is disclosed, as well as master batch processes. The present invention also relates to a method of making a container wherein the sulfo-modified copolyester is blended with the polyglycolic acid at an injection molding machine used to make preforms, which are then blown into bottles.
1. A composition in the form of a clear monolayer article, comprising a blend of: (a) a sulfo-modified copolyester comprising an aromatic or cyclic sulfonated diacid and a comonomer; and (b) polyglycolic acid, wherein said sulfo-modified copolyester comprises a 5-sulfoisophthalic acid monomer in the range of about 1 to about 5 mole % and a comonomer in the range of about 5 to about 15 mole %.
2. The composition of claim 1 in which the comonomer is isophthalic acid or 1,4-cyclohexanedimethanol.
3. The composition of claim 1 in which said sulfo-modified copolyester has an intrinsic viscosity in the range of about 0.6 to 1.0 dl/g.
4. The composition of claim 1 , wherein said polyglycolic acid is present in a range of about 1 to about 10 wt. %, based on the weight of the composition.
5. The composition of claim 1 in which the melt viscosity ratio, measured at 275° C. and 100 sec −1 of said copolyester and said polyglycolic acid is greater than 2.
6. The composition of claim 1 in which the melt viscosity ratio, measured at 275° C. and 100 sec −1 of said copolyester and said polyglycolic acid is greater than 10.
7. The composition of claim 1 , wherein said comonomer is isophthalic acid.
8. A method of manufacturing a blend of sulfo-modified copolyester and polyglycolic acid that forms a clear monolayer article, comprising the steps of
a) preparing a master batch of sulfo-modified copolyester by reacting isophthalic acid or C 1 -C 4 -dialkyl isophthalate or 1,4-cyclohexanedimethanol, and a compound according to formula (II):
wherein R is hydrogen, a C 1 -C 4 -alkyl or a C 1 -C 4 -hydroxyalkyl, and wherein
and wherein M is an alkali metal ion, earth alkali metal ion, phosphonium ion or ammonium ion; and
b) melt blending to the master batch of step a) polyglycolic acid and a polyester resin, thereby forming said blend of sulfo-modified copolyester and polyglycolic acid having at least 2.0 but not more than 15 mole % isophthalic acid (IPA) or C 1 -C 4 -dialkyl isophthalate or 1,4 cyclohexanedimethanol; and at least 0.5, but not more than 5.0 mol % of the compound of formula (II); and about 1 to about 10 wt. % of polyglycolic acid, based on the weight of the blend of sulfo-modified copolyester and polyglycolic acid, wherein said blend forms a clear monolayer article.
9. The method of claim 8 , wherein