Polyester resin composition and film using the same

Details Polyester resin composition and film using the same Polyester resin composition and film using the same

2001-03-12

2003-10-07

Short, Patricia A. (Department: 1712)

Stock material or miscellaneous articles

Structurally defined web or sheet

Physical dimension specified

C525S444000

Reexamination Certificate

active

06630230

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polyester resin composition, more precisely a polyester resin composition which can provide a polyester film having a low minimum stretching temperature and excellent heat shrinkability and flexibility.
BACKGROUND OF THE INVENTION
Recently, polyethylene terephthalate films have been studied for use in heat-shrinkable labels mainly for PET bottles. It will be beneficial for the recycling of PET bottles, if labels are made of the same kind of resin as the bodies of the bottles. However, although polyethylene terephthalate films are excellent in heat resistance, mechanical properties, transparency and the like, they suffer poor elongation, which makes them likely to be torn, and insufficient shrinkability at a low temperature.
To overcome these problems, polyethylene terephthalate copolycondensated with various dicarboxylic acid components and/or glycol components has been studied. However, such a material has not necessarily provide sufficiently improved heat shrinkability at low temperature. Moreover, it has also been studied to improve flexibility and elongation of the resin by blending various elastomers. However, because addition of polyester elastomers even in a small amount makes the resin white, i.e., opaque, for example, this technique has not been practically used yet.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a polyester resin composition which can provide a polyester film having a low minimum stretching temperature, and exhibiting excellent heat shrinkability and flexibility.
To achieve the aforementioned object, the present inventors earnestly conducted studies. As a result, it was found that a polyester resin composition comprising an amorphous polyethylene terephthalate resin in admixture with a particular polyester ether resin at a weight ratio of 97/3 to 50/50 could exhibit excellent properties, and thus the present invention has been accomplished.
That is, according to the present invention, there is provided a polyester resin composition comprising (a) an amorphous polyethylene terephthalate resin and (b) a polyester ether resin in admixture at a weight ratio of 97/3 to 50/50, wherein the polyester ether resin (b) is prepared by copolycondensation of (b1) dicarboxylic acid and/or ester derivative thereof consisting mainly of an aromatic dicarboxylic acid and/or ester derivative thereof, and (b2) diols consisting mainly of a C2-C6 alkylene glycol and a poly(C2-C4 alkylene oxide) glycol, and segments derived from the poly(C2-C4 alkylene oxide) glycol constitute 1 to 30% by weight of the polyester ether resin (b), and the polyester ether resin (b) has a peak temperature of tan &dgr; of 20 to 60° C.
According to another aspect of the present invention, there is provided a polyester film which is composed of a blended resin comprising (a) an amorphous polyethylene terephthalate resin and (b) a polyester ether resin in admixture at a weight ratio of 97/3 to 50/50, wherein the polyester ether resin (b) is prepared by copolycondensation of (b1) dicarboxylic acid and/or ester derivative thereof consisting mainly of an aromatic dicarboxylic acid and/or ester derivative thereof, and (b2) diols consisting mainly of a C2-C6 alkylene glycol and a poly(C2-C4 alkylene oxide) glycol, and segments derived from the poly(C2-C4 alkylene oxide) glycol constitute 1 to 30% by weight of the polyester ether resin (b), and the polyester ether resin (b) has a peak temperature of tan &dgr; of 20 to 60° c.
Preferably, the aromatic dicarboxylic acid is terephthalic acid.
The C2-c6 alkylene glycol is preferably ethylene glycol or tetramethylene glycol, more preferably tetramethylene glycol.
The poly(C2-C4 alkylene oxide) glycol is preferably polytetramethylene oxide glycol.
The segments derived from poly(C2-C4 alkylene oxide) glycol preferably constitute 3 to 20% by weight of the polyester ether resin (b).
According to embodiments of the present invention, there are provided a polyester resin composition comprising (a) an amorphous polyethylene terephthalate resin and (b) a polyester ether resin in admixture at a weight ratio of 97/3 to 50/50, wherein the polyester ether resin (b) is prepared by copolycondensation of dicarboxylic acid and/or ester derivative thereof consisting mainly of terephthalic acid and/or ester derivative thereof, and diols consisting mainly of tetramethylene glycol and polytetramethylene oxide glycol, and segments derived from the polytetramethylene oxide glycol constitute 1 to 30% by weight of the polyester ether resin, and the polyester ether resin (b) has a peak temperature of tan &dgr; of 20 to 60° C.; and a polyester film which is composed of a blended resin comprising (a) an amorphous polyethylene terephthalate resin and (b) a polyester ether resin in admixture at a weight ratio of 97/3 to 50/50, wherein the polyester ether resin (b) is prepared by copolycondensation of dicarboxylic acid and/or ester derivative thereof consisting mainly of terephthalic acid and/or ester derivative thereof, and diols consisting mainly of tetramethylene glycol and polytetramethylene oxide glycol, and segments derived from the polytetramethylene oxide glycol constitute 1 to 30% by weight of the polyester ether resin, and the polyester ether resin (b) has a peak temperature of tan &dgr; of 20 to 60° C.
According to the present invention, the amorphous polyethylene terephthalate resin (a) preferably has a glass transition temperature of 50° C. or higher.
According to the present invention, the poly(C2-C4 alkylene oxide) glycol preferably has a number average molecular weight of 500 to 6,000.
According to the present invention, the polyester ether resin preferably has a melting point of 200 to 240° C.
According to the present invention, the polyester ether resin preferably has a melt viscosity of 500 to 30,000 poises as measured at a temperature of 250° C. under a shear rate of 91.2 sec
−1
.
According to the present invention, the polyester ether resin preferably has a peak temperature of tan &dgr; of 20 to 60° C.
The polyester film of the present invention is preferably a heat-shrinkable film.
The polyester film of the present invention preferably has a heat shrinking ratio of 15% or more along the main shrinking direction, and less than 15% along the direction perpendicular to the main shrinking direction at 70° C.
The polyester film of the present invention preferably has a thickness of 3 to 500 &mgr;m, more preferably 20 to 200 &mgr;m.
PREFERRED EMBODIMENTS OF THE INVENTION
Embodiments and methods for practice of the present invention will be explained in detail hereinafter.
The component (a) of an amorphous polyethylene terephthalate resin used for the present invention may be, for example, a polyester resin produced by copolycondensation of a component consisting of terephthalic acid or ester derivative thereof and an ethylene glycol component, together with a component consisting of one or more other dicarboxylic acids or ester derivatives thereof and/or one or more other glycol components, i.e., an amorphous co-PET resin.
Specific examples of the amorphous polyethylene terephthalate resin include, for example, polyester resins produced by copolycondensation of terephthalic acid, ethylene glycol, and a dicarboxylic acid other than terephthalic acid, polyester resins produced by copolycondensation of terephthalic acid, ethylene glycol, and a glycol other than ethylene glycol, polyester resins produced by copolycondensation of terephthalic acid, ethylene glycol, a dicarboxylic acid other than terephthalic acid, and a glycol other than ethylene glycol and the like. One kind of the amorphous polyethylene terephthalate resin may be used alone, or two or more kinds of the resin may be used in combination.
Examples of the aforementioned dicarboxylic acid component other than terephthalic acid include, for example, components consisting of aromatic dicarboxylic acids, alicyclic dicarboxylic acids, aliphatic dicarboxylic acids, ester derivatives thereof and the like. Mixtures thereof may als

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