JPH0472693B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a multilayer container with excellent barrier properties against oxygen, carbon dioxide, and the like. (Prior art) Polyester resins such as polyethylene terephthalate resin (hereinafter abbreviated as PET) have traditionally been
Taking advantage of its excellent mechanical strength, gas barrier properties, hygienic properties, and other properties, it is widely used as a variety of containers, especially hollow containers such as bottles. However
PET does not have perfect gas barrier properties for containers for food and beverages that require a high degree of gas barrier properties. It is being done. Recently, ethylene isophthalate polyester has begun to attract attention as a material with high gas barrier properties. (Problems to be Solved by the Invention) However, although ethylene isophthalate polyester has high gas barrier properties, it has low strength because it is amorphous. Therefore, it is possible to improve the strength by stretching this, but in reality it is difficult to perform a uniform stretching process, and even if it is stretched, the strength will not improve much. There are also concerns about hygiene, depending on the contents of the container. The present invention improves the above-mentioned drawbacks while taking advantage of the high gas barrier properties of ethylene isophthalate polyester. (Means for solving the problems) The present invention will be explained in detail below. In the following description, "part" indicating a ratio indicates "part by weight" and "%" indicates "mol %". In the present invention, the innermost layer is made of PET and the outer layer is made of PET.
It is made of a mixture of PET and ethylene isophthalate copolyester (hereinafter referred to as EI copolyester). The PET used here as the innermost layer not only provides hygiene to the container, but also serves to increase its strength. As for PET, 80% or more of the acid component, preferably 90% or more of the acid component is terephthalic acid and glycol component.
A crystalline resin containing 80% or more, preferably 90% or more of ethylene glycol is used. 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, , 4-butanediol, cyclohexanedimethanol, and the like. The PET to be used as a component of the outer layer is selected from those listed above, but one with an intrinsic viscosity of 0.8 or more is preferred. In addition, the EI polyester used as the other component of the outer layer is polyethylene isophthalate or a copolyester mainly composed of ethylene isophthalate, and in particular, 80 to 95% of the acid component is isophthalic acid, and all or most of the remainder is is terephthalic acid and the glycol component is preferably ethylene glycol. Isophthalic acid content in EI copolyester
If it is less than 80%, the gas barrier properties of the mixture will not improve significantly when mixed with PET. Moreover, if it exceeds 95%, the homogeneous miscibility with PET tends to decrease slightly and the strength of the mixture tends to decrease considerably, so the above-mentioned copolyesters are preferred. The mixing ratio of PET and EI polyester in the outer layer is in the range of 40 to 80 parts of PET and 20 to 60 parts of EI polyester. If the amount of PET is less than 40 parts, the strength of the mixture will not be sufficient and the outer layer may be destroyed by external force, and the stretchability will also be poor. Moreover, if it exceeds 80 parts, the gas barrier properties will be insufficient. A particularly preferable mixing ratio is 50 to 70 parts of PET and 30 to 70 parts of EI polyester.
The range is 50 copies. Mixing PET into the outer layer also has the effect of improving the adhesive strength with the inner PET layer. In the body, which is the main part of the container, it is preferable that the innermost layer and the outer layer as a whole contain about 20 to 40% of the isophthalic acid component. For this purpose, the mixing ratio and the thickness ratio between the innermost layer and the outer layer may be appropriately set, and the thickness ratio is generally such that the ratio of the outer layer is about 0.5 to 0.8 of the total thickness. The container of the present invention is a two-layer container in which the inner layer is PET and the outer layer is the mixture layer, the innermost layer and the outermost layer are PET,
It may be a three-layer container in which the intermediate layer is the mixture layer, or a container with an even larger number of layers. In this case, generally no adhesive layer is required between the PET layer and the mixture layer. The container of the present invention is typically a bottle obtained by a biaxial stretch blow molding method, and can be obtained by blow molding a multilayer parison obtained by a multilayer coextrusion method or a multilayer injection molding method. In particular, by multi-layer injection, first the inner layer PET parison is injected, then the outer layer is injected only into the body and bottom portions of the parison, and the mouth part is made of PET.
It is practical to use only layers. (Effects of the Invention) According to the present invention, a multilayer container having the following excellent performance can be obtained. (1) By using a mixture of EI polyester and PET for the outer layer, a container with higher gas barrier properties than ordinary PET containers can be obtained. (2) Furthermore, by adding PET to the outer layer, the strength is significantly improved compared to the case of EI polyester alone, and the uniformity of stretching is also increased. (3) Since the outer layer and the inner layer contain PET as a common component, both layers adhere strongly and there is no risk of peeling. (4) When a copolyester containing a small amount of terephthalic acid component is used as an EI polyester,
It has good dispersion affinity with PET, and as a result, the strength of the mixture is high, which is particularly preferred. (5) By using PET for the inner layer, the container is strengthened and has excellent hygiene, with no risk of foreign matter leaching out. (Example) A two-layer bolt was molded using PET as the inner layer and the following two types of materials as the outer layer. No. 1 Ethylene isophthalate-ethylene terephthalate copolyester (Isophthalic acid content 90
%) (Comparative example) No. 2 Ethylene isophthalate-ethylene terephthalate copolyester (Isophthalic acid content
A mixture of 40 parts (90%) and 60 parts PET (invention).For molding, first the inner layer PET is injected into a mold to form a low cylindrical parison, and then the outer layer material is injected into the parison in another mold. A two-layer parison was obtained by injecting into the body and bottom portions. Next, the parison is blow molded to a height of 250 mm, a body diameter of 120 mm, and a body thickness of approximately
The bottle had a round bottom of 0.4 mm and an outer layer thickness ratio of 0.7. In the bottle No. 1, the stretching was somewhat uneven, and variations in body thickness were observed. The following items were evaluated for each bottle. (1) Gas barrier properties Fill a bolt with water containing 4 gas volumes of carbon dioxide gas, leave it in an atmosphere of 23℃ and 50% RH, and measure the amount of carbon dioxide gas escaping from the bottle by the drop in bottle internal pressure. It is expressed as the period (weeks) during which the internal pressure decreases by 15%. (2) Bottle impact strength 10 bottles each with the bottom facing down at a temperature of 5℃
Then, the number of pieces that would cause the lower part to break was determined by dropping them from a height of 3 m. The above results are shown in Table 1.

[Table] As is clear from the results in Table 1, the bottle of the present invention (No. 2) has excellent drop strength and gas barrier properties of ordinary PET bottles (same thickness but gas barrier properties of approximately
12 weeks). On the other hand, No. 1 has excellent gas barrier properties but is inferior in drop strength.

Claims (1)

[Claims] 1. The innermost layer is polyethylene terephthalate resin,
The outer layer is made of 40 to 80 parts by weight of polyethylene terephthalate resin and 20 parts by weight of ethylene isophthalate polyester.
A multilayer container consisting of a mixture with ~60 parts by weight. 2 Ethylene isophthalate polyester is
Claim 1, characterized in that 80 to 95 mol% of the acid component is isophthalic acid, all or most of the remainder is terephthalic acid, and the glycol component is a copolyester consisting essentially of ethylene glycol. Multilayer container as described. 3. The multilayer container according to claim 1 or 2, wherein 20 to 40 mol% of the acid components in the innermost layer and the outer layer in the container body are isophthalic acid.