JPS6222851A - Bottle having gas barrier properties - Google Patents

Abstract

PURPOSE:To improve the balance between gas barrier properties and pressure resistance by improving the uniformity in thickness and orientation properties in the molding of a bottle, by using a mixture of a polyethylene terephthalate resin and an ethylene isophthalate copolyester in a specified ratio. CONSTITUTION:A bottle is formed from a mixture of a polyethylene terephthalate resin (a) and an ethylene isophthalate copolymer (b) which accounts for 10-20pts.wt. of the quantity of the mixture. The copolyester (b) is formed from an acid component consisting of 80-95mol% isophthalic acid and the balance composed of wholly or mostly terephthalic acid and a glycol component substantially consisting of ethylene glycol.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a polyester blow-stretched bottle that has excellent barrier properties against M atoms, carbon dioxide, and the like.

(Conventional technology) Polyethylene terephthalate resin (rPE
Polyester resins such as TJ) are *6
．． It is widely used as a variety of containers, especially hollow containers such as bottles, due to its mechanical strength, gas barrier properties, and hygienic properties. However, PET does not have perfect gas barrier properties for food and beverage containers that require high gas barrier properties. To compensate for this drawback, polyethylene isophthalate 1~ has recently begun to attract attention as a material with high gas barrier properties, and containers with high gas barrier properties that are a blend of PET and polyethylene isophthalate have been proposed (
JP-A No. 59-64658).

(Problem to be Solved by the Invention) However, when trying to make a two-wheel stretched bottle out of a blend of polyethylene isophthalate and PET, the shoulder and bottom parts, which are difficult to stretch, remain extremely thick, and on the other hand, the body part It has been found that the material has the disadvantage that the thickness becomes thinner, and as a result, the gas barrier properties are lowered in the thin wall portion of the ball, resulting in the excellent performance of the raw material not being fully utilized.

(Means for Solving the Problems) The present invention improves the above drawbacks by using raw materials with a specific composition.

The present invention will be explained in detail below. In the following explanation, "part" indicating a ratio means "part by weight", and "1%" means "1 mol%".

The bottle of the present invention is made of PET and ethylene isophthalate copolyester (hereinafter referred to as rEI copolyester).
It consists of a mixture of

Here, PET becomes the main component of the mixture and plays a role in increasing the strength. For PET, 80% or more of the acid component, preferably 90% or more of the glycol terephthalate component.
% or more, preferably 90% or more of the crystalline resin is ethylene glycol. Other acid components of this PET include isophthalic acid, naphthalene-1, 4 or 2.
Examples of the glycol component include 6-dicarboxylic acid, adipic acid, and levacic acid. Examples of other glycol components include diethylene glycol, propylene glycol, 1,4-butanediol, and cyclohexane dimetatool.

Particularly preferred is a PET homopolymer having an intrinsic viscosity of 1.0 or more from the viewpoint of strength and stretchability.

Note that the intrinsic viscosity referred to herein is measured and calculated at 30° C. for a 1% solution using an isobaric ff1fflfi mixed solvent of phenol and tetrachloroethane.

In the El-based copolyester used as other components, 80 to 95% of the acid component is isophthalic acid, all or most of the remainder is terephthalic acid, and the glycol component consists essentially of ethylene glycol. In this way, when an Et-based copolyester containing a small amount of terephthalic acid is used, the compatibility with 1FET is significantly improved compared to when polyethylene isophthalate (pomopolymer) is used.

Since EI polyester tends to become amorphous, it is difficult to stretch it uniformly, and its strength does not improve much.

However, when PET is mixed with this, it becomes possible to stretch it and also improves its strength. However, as the El-based polyester becomes more moldy, it becomes increasingly difficult to draw it uniformly, resulting in non-uniform thickness, and it becomes impossible to fully orient the mixture. As a result, gas barrier properties and pressure resistance are insufficient in the thin walled portions, resulting in restrictions on bottle shape and type of contents. Therefore, in the present invention, the mixing ratio of El-based copolyester is 10 parts to 100 parts of the mixture.
or more and less than 20 copies. If the mixing ratio is within this range, a bottle with an almost uniform thickness can be obtained using a normal blow molding machine, and the uniformity of the thickness and the stretching orienting effect can be easily achieved. A relatively high gas barrier property can be obtained. If the ratio of the El-based copolyester is less than 10 parts, the improvement in b gas barrier properties will not be recognized much compared to normal PET.

If the mixing ratio is within the above range, the gas barrier properties will be improved by about 20 to 60% compared to the case of using only PET.

Either injection molding or extrusion molding can be used to form 1 q of parisons from this mixture. PET and El-based copolyester can be mixed by directly mixing them in a molding machine such as an extruder or injection molding machine, or by melt-mixing the two and then feeding the two to a molding machine. The latter method is preferred. Blow molding may be performed by a method known per se. That is, an injection-molded bottomed parison or an extrusion-molded bottomed parison with one end of the vibrator closed is heated to the appropriate temperature for stretching, and the heated parison is heated in a blow mold at 6 to 15K. (1/c
Blow molding is performed at a pressure of about m2. At this time, conventionally known means are used in combination, such as thinly combing the parts corresponding to the shoulders and the bottom of the parison in advance, and heating the above parts to a slightly higher temperature than other parts when heating the parison. is also preferable.

The obtained bottle is preferably heat-treated at a temperature equal to or higher than the crystallization start temperature of PET to crystallize the PET and impart thermal stability (dimensional stability during heating).

(Effects of the Invention) According to the present invention, a bottle having a uniform thickness and effective stretching orientation can be obtained from an FI-based polysaltal which is difficult to stretch uniformly. Therefore, the bottle of the present invention has improved gas barrier properties and pressure resistance in a well-balanced manner.

Claims (1)

[Claims] 1) A blow bottle made of a mixture of polyethylene terephthalate resin and ethylene isophthalate copolyester, wherein the copolyester has an acid component of 80 to 9
5 mol% is isophthalic acid, the remainder is all or most terephthalic acid, the glycol component consists essentially of ethylene glycol, and the copolyester is contained in the mixture at least 10 parts by weight and less than 20 parts by weight. A gas barrier bottle characterized by: