JPS6143655A - Container having gas barrier property - Google Patents

Abstract

PURPOSE:A container having high strength and improved gas barrier properties, comprising a mixture of an ethylene isophthalate copolymer containing a small amount of a terepththalic acid component and PET. CONSTITUTION:(A) 50-80pts.wt. polyethylene terephthalate comprising an acid component having >=80mol% terephthalic acid and a glycol component having >=80mol% ethylene glycol is blended with (B) 20-50pts.wt. ethylene isophthalate copolyester comprising an acid component 80-95mol% isophthalic acid and almost all the rest of terephthalic acid, and a glycol component of ethylene glycol. An amount of isophthalic acid in the blend is 20-40wt%. The blend is mainly subjected to biaxially oriented blow molding to give bottles.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a container, particularly a bowl, which has excellent barrier properties against oxygen, carbon dioxide, and the like.

(Conventional technology) Polyethylene terephthalate resin (hereinafter referred to as PET)
W polyester resin (abbreviated as ) is widely used for various containers, especially hollow containers such as bottles, due to its excellent mechanical strength, gas barrier properties, hygienic properties, and other 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 has recently begun to attract attention as a material with high gas barrier properties, and PET
A container with high gas barrier properties has been proposed, which is a blend of polyethylene isophthalate and polyethylene isophthalate.
No. 658).

(Problem to be Solved by the Invention) However, in a blend of polyethylene isophthalate and PET, although the two appear to be homogeneously mixed, microscopically, the dispersion is insufficient, and as a result, the mixture However, it has been found that there is a problem in that it is vulnerable to external forces such as shock.

The present invention improves the above-mentioned drawbacks while making use of the high gas barrier properties of ethylene isophthalate-based poly 1 stell.The present invention improves the above-mentioned drawbacks by making use of the high gas barrier properties of ethylene isophthalate-based polyester. This was made based on the discovery that when used, the compatibility of the two is greatly improved, and as a result, the strength of the resulting container is increased.

(Means for solving the problems) The present invention will be described in detail below. In the following explanation, "parts" means "parts by weight" and "%J" means "mol%j" without indicating ratios.

The container of the present invention is made of a mixture of PET and ethylene isophthalate copolyester (hereinafter referred to as EI copolyester).

Here, PET becomes the main component of the mixture and plays a role in increasing the strength. In PET, the acid component is 80% or more, preferably 90% or more is terephthalic acid, and the glycol component is 80% or more, preferably 90% or more.
It is a crystalline resin containing 0% or more, preferably 90% or more of ethylene glycol. Other acid components of this PET include isophthalic acid, naphthalene-1,4 or 2,6-dicarboxylic acid, adipic acid, sebacic acid, etc., and other glycol components include diethylene glycol, propylene glycol, etc. , 1,4-butanediol cyclohexanedimethanol, and the like.

In the EI 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.

Since ET copolyester 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, uniform stretching becomes possible and strength sufficient for practical use is increased.

The gas barrier properties of the resulting container are determined by the ffi<I21] of the isophthalic acid component in the mixture, the inphthalic acid content in the El-based copolyester, and the amount of ET-based copolyester mixed with PET); It is preferable that m of the acid is 20 to 40%, 20
If it is less than 40%, the effect of improving gas barrier properties is small;
%, the strength of the container will be somewhat insufficient. To obtain the above-mentioned isophthalic acid (2), 50 to 80 parts of PET and 20 to 50 parts of El-based copolyester are mixed. If the amount of PET is less than 50 parts, the strength of the container will be insufficient and the stretching will be uneven, 1, and if it exceeds 80 parts, the gas barrier properties will be reduced.

The higher the inphthalic acid content in the El-based copolyester, the better from the viewpoint of gas barrier properties, but if it exceeds 95%, PE
Since it tends not to be homogeneously mixed with T, a copolymer with 5% or more of terephthalic acid is preferred. However, if the amount of terephthalic acid is more than 20%, the gas barrier property decreases by EI.
It is necessary to compensate for this by increasing the amount of the mixed copolyester (2), which reduces the strength of the container.

There are two methods for mixing PET and El-based copolyester: a method of directly mixing them in a molding machine such as an extruder or an injection molding machine, and a method of once melting and mixing the two and then feeding them to a molding machine.
The latter method is preferred in order to improve dispersibility.

The container of the present invention is typically a bottle obtained by the 21111 stretch blow molding method, and can be obtained by blow molding a parison obtained by an extrusion molding method or an injection molding method.

(Effects of the Invention) By mixing El-based copolyester containing a terephthalic acid component with PET, the container of the present invention has a high strength due to uniform dispersion and affinity between the two, and also has gas barrier properties similar to those of ordinary PE. The lower container is more country. For example, 30 parts of ethylene isophthalate-ethylene terephthalate copolyester (containing isophthalic acid 190%) and 70 parts of PET
A parison was molded by injection molding from the mixture with the parts, and then this parison was blow molded to have a body diameter of 120 mm.
2501 + 1111, 114 parts Thickness Q, 4mm round bottom photo/L, tL/, When 10 of these bottles were dropped from a height of 3m with the bottom facing down at 5℃, only one was broken. However, it had sufficient strength for practical use.

Claims (1)

[Claims] 1) 50 to 80 parts by weight of polyethylene terephthalate resin and 20 to 5 parts by weight of ethylene isophthalate copolyester
0 parts by weight of the copolyester, wherein 80 to 95 mol% of the acid component is isophthalic acid and all or most of the remainder is terephthalic acid, and the glycol component is substantially ethylene glycol. A barrier container characterized by being made of a copolyester consisting of. 2) The container according to claim 1, wherein 20 to 40 mol % of the acid component in the mixture is isophthalic acid.