Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2002-05-24
2004-05-25
Woodward, Ana L. (Department: 1711)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S220000, C525S425000
Reexamination Certificate
active
06740376
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyester based resin composition which comprises a polyester resin obtained by polycondensation of a dicarboxylic acid having a cyclic acetal skeleton or of a diol component containing a diol and having a cyclic acetal skeleton; a polyamide resin; and as the case may be, a polyethylene terephthalate resin, and which is excellent in transparency, gas barrier properties and pinhole resistance. The present invention also relates to a molded product obtained from the polyester based resin composition.
2. Description of the Related Arts
A polyester resin which is typified by a polyethylene terephthalate resin, and in which an aromatic dicarboxylic acid is a principal dicarboxylic acid component, and an aliphatic diol is a principal diol component (hereinafter sometimes referred to as “aromatic polyester based resin”) is characterized by being excellent in mechanical performance, melting stability, solvent resistance, perfume preservability, recycling properties and the like. Thus it is widely utilized for packaging materials such as films, sheets and hollow containers. However, since the gas barrier properties thereof for oxygen, carbon dioxide and the like are not always favorable, the utilization thereof is limited in applications which require high gas barrier properties. There are available, as a means for imparting gas barrier properties to an aromatic polyester resin, a means by laminating the resin with a metallic foil such as aluminum foil; a means by coating or laminating the resin with an other resin having a high gas barrier property; a means by depositing aluminum or silicon on the resin; and the like means. However, any of the above-mentioned means involves such a problem as impairing transparency, necessitating an intricate production process, or impairing the mechanical performance.
There is available, as a means for imparting gas barrier properties to an aromatic polyester resin without necessitating an intricate production process, a means by mixing the resin with another resin having high gas barrier properties, which is available from polyamide resins typified by nylon
6
and nylon
66
. In particular, excellent gas barrier properties are assured by a polyamide resin which is obtained by polycondensation of meta-xylylenediamine and adipic acid (hereinafter sometimes referred to as “polyamide MXD6”). On the other hand, there is available, as a resin having gas barrier properties other than the polyamide resin, ethylene/vinyl alcohol copolymer resin, which however involves such problems that owing to its poor compatibility with an aromatic polyester resin, the composition of both the resins becomes whitely turbid, impairs stretching properties of the resins just mentioned due to high crystallinity, is inferior in heat stability, and the like.
On the other hand, polyamide MXD6 has high gas barrier properties, has a glass transition temperature, melting point and crystallinity each close to those of the aromatic polyester resin, particularly to polyethylene terephthalate and besides, is excellent in heat stability on melting. Accordingly polyamide MXD6 is easy to melt and mix with the aromatic polyester resin, and is advantageous in that it does not impair the stretching properties or mechanical performance of the aromatic polyester resin, and manifests high gas barrier properties.
However, a resin composition comprising the aromatic polyester resin and the polyamide resin such as polyamide MXD6, which has insufficient transparency, is limited in applications requiring high transparency.
In such circumstances, there are proposed a method in which a mixture comprising the polyamide resin and the polyester resin is incorporated with a tetracarboxylic acid anhydride {Japanese Patent Application Laid-Open No. 272660/1989 (Heisei 1)}; a method in which a compound bearing an epoxy group and an acid anhydride group is employed as one type of compatibilizer for the composition of a thermoplastic polyester resin and a polyamide resin having a meta-xylylene group in its main chain {Japanese Patent Application Published No. 2871/1994 (Heisei 6)}; and a method in which a polycarboxylic acid is blended and melt kneaded with an aromatic polyester resin {Japanese Patent Application Laid-Open No.302952/2000 (Heisei 12)}. Nevertheless, any of the above-mentioned methods necessitates an intricate production process. Further, there is proposed a method by using polyethylene terephthalate (PET) and polymeta-xylyleneadipamide which have a specific relative-viscosity-ratio in a specific range {Japanese Patent Application Laid-Open No. 2800/2001 (Heisei 13)}. However, the method involves such problems as insufficient transparency and hygienic question in the case of using for the purpose of food packaging, and further a problem in that the content inside such a packaging material assumes different aspect from the reality owing to its yellowing and/or pearl-like gloss.
SUMMARY OF THE INVENTION
A general object of the present invention is to eliminate the problems as mentioned hereinbefore, and to provide a polyester resin composition which comprises a polyester resin and a polyamide resin, and which is usable for a film, sheet, thin wall hollow container and the like each being excellent in transparency, gas barrier properties, color tone and pinhole resistance.
Other objects thereof will become obvious from the text of this specification hereinafter disclosed.
As a result of intensive research and investigation made by the present inventors it has been found that there is obtainable a resin composition for use in a film, sheet, thin wall hollow container and the like each being excellent in gas barrier properties, transparency, color tone and pinhole resistance by melt kneading the components composed of a polyester resin and a polyamide resin and, as the case may be, a polyethylene terephthalate resin, with a diol having a cyclic acetal skeleton and/or a polyethylene terephthalate resin. The present invention has been accomplished by the above-mentioned findings and information.
Specifically, the present invention relates to a polyester based resin composition (D) which comprises a polyamide resin (A) and a polyester resin (B), or a polyamide resin (A), a polyester resin (B) and a polyethylene terephthalate resin (C), characterized in that said polyester resin (B) is obtained by polycondensation of a dicarboxylic acid component containing 0.5 to 60 mol % of a dicarboxylic acid having a cyclic acetal skeleton and/or of a diol component containing 0.5 to 60 mol % of a diol having a cyclic acetal skeleton, and that the blending proportions of the polyamide resin (A), the polyester resin (B) and the polyethylene terephthlate resin (C) are each in the range of 1 to 99% by weight, 1 to 99% by weight and 0 to 98% by weight, respectively on the basis of total sum weight of the components (A), (B) and (C). The present invention also relates to a molded product obtained from the resin composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The resin composition according to the present invention is the polyester based resin composition which comprises a polyamide resin (A) and a polyester resin (B), and optionally a polyethylene terephthalate resin (C). In the following, specific description will be given of the resins to be employed in the present invention, blending proportions thereof, mixing method and molded products obtained from the foregoing polyester based resin composition.
Polyamide Resin (A)
The polyamide resin (A) is a well known moldable resin which is obtained by polymerizing an amino acid, lactam or diamine and dicarboxylic acid each as a monomer.
The amino acid monomer is specifically exemplified by 6-aminocapronic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and p-aminomethylbenzoic acid. The lactam is exemplified by &egr;-caprolactam and &ohgr;-laurolactam.
The diamine monomer is exemplified by but not limited to tetra-methylenediamine, hexam
Hayashi Takeo
Hirokane Takeshi
Kurokawa Masahiro
Oguro Dai
Antonelli Terry Stout & Kraus LLP
Mitsubishi Gas Chemical Company Inc.
Woodward Ana L.
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