JPH0536301B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a multilayer container made of polyester resin. (Prior Art) In recent years, containers such as biaxially stretched blow bottles made of polyester resin such as polyethylene terephthalate have become widely used. During the process of molding this polyester resin into containers, it may generate extremely small amounts of acetaldehyde, and if this remains in a sealed container, its odor will adversely affect the taste and aroma of the contents, such as soft drinks. I was afraid. Conventionally, in order to prevent the generation of acetaldehyde, methods such as sufficiently drying the polyester resin during the polymerization stage, reducing acetaldehyde through oxidation and reduction, and melting the resin at the lowest temperature possible when molding it. is being done. (Refer to JP-A-52-110177 and JP-A-53-28693) (Problems to be solved by the invention) However, the above method requires continuous precise process control from polymerization of polyester resin to molding of the container. A complicated problem arose. (Means for Solving the Problems) In view of the above problems, the present invention attempts to reduce the acetaldehyde component by adding another resin to the polyester resin at the stage of molding the container. The gist is that the innermost layer is made of a mixture of ethylene terephthalate polyester resin and polyamide, and the outer layer is made of ethylene isophthalate polyester resin or a mixture of ethylene isophthalate polyester resin and ethylene terephthalate polyester resin. It is a multilayer container. The present invention will be explained in detail below. In the following explanation, "part" indicating a ratio represents a "polymerization part". The ethylene terephthalate polyester resin (hereinafter simply referred to as PET) used here is:
A crystalline resin is used in which terephthalic acid accounts for 80 mol% or more, preferably 90 mol% or more of the acidic component, and ethylene glycol accounts for 80 mol% or more, preferably 90 mol% or more of the glycol component. Other acid components of this PET include isophthalic acid and naphthalene.
Examples include 1, 4 or 2, 6-dicarboxylic acid, adipic acid, sebacic acid, and other glycol components include diethylene glycol, propylene glycol, 1, 4-butanediolcyclohexanedimethanol, and the like. this
PET is selected from those listed above, but those with an intrinsic viscosity of 0.8 or more are preferred. In the present invention, polyamide resin (hereinafter simply PA)
) as nylon 6, nylon 6, 6,
Aliphatic nylons such as nylon 610, nylons containing metaxylylene groups, or copolymers or mixtures thereof are used. In the present invention, the mixing ratio of PET and PA is preferably 0.05 to 10 parts of PA per 100 parts of PET.
A range of at least 1 part and less than 1 part is more preferable. P.A.
If it is less than 0.05 parts, the effect of reducing acetaldehyde will be small, and if it is more than 10 parts, it will adversely affect the excellent properties of PET, resulting in deterioration of physical strength, moldability, etc., so 0.05 to 10 parts is preferable. Also, P.A.
If it is less than 1 part, the resulting container is unlikely to become cloudy and there is no need to add colorants to improve the appearance.
This method is more preferable because a transparent container can be obtained. In addition, ethylene isophthalate thermoplastic polyester resin (hereinafter simply referred to as
PEI) is polyethylene isophthalate or a copolyester whose main component is ethylene isophthalate, with an acidic content of 80%
Preferably, ~95 mol% is isophthalic acid, all or most of the remainder is terephthalic acid, and the glycol component consists essentially of ethylene glycol. By mixing PET with PEI as the outer layer,
It also has the effect of improving the physical strength of the outer layer and improving the adhesive strength with the inner PET layer. In this case, the mixing ratio of PET and PEI in the outer layer is preferably in the range of 50 to 80 parts of PET and 120 to 50 parts of PE. If PET is less than 50 parts, the strength of the mixture will not be sufficiently improved compared to PEI alone, and the effect of mixing will be small. Furthermore, if PET exceeds 80 parts, the effect of improving gas barrier properties due to PEI will be reduced, so the above mixing ratio is preferable. In the body, which is the main part of the container, it is preferable from the viewpoint of gas barrier properties that the innermost layer and the outer layer as a whole contain about 20 to 40% of the isophthalic acid component. To do this, the mixing ratio and the thickness ratio between the innermost layer and the outer layer may be set appropriately, but the thickness ratio is generally set so that the ratio of the outer layer is 0.5 of the total thickness.
It should be about ~0.8. The container of the present invention includes a two-layer container in which the inner layer is a mixture layer of PET and PA and the outer layer is PEI or the mixture layer, a three-layer container in which the outermost layer is a protective layer such as PET,
Or it may have even more layers. In this case, generally no adhesive layer is required between the PET layer and the mixture layer. In order to mix PET and PA or PET and PEI, for example, both resins can be dry blended and then extruded while being kneaded using an extruder for pellet production to produce mixed resin pellets. In addition, in order to mold the multilayer container of the present invention,
There is no difference from conventional methods for producing polyester containers, such as biaxial stretch blow molding, extrusion molding onto a sheet, and vacuum forming or pressure forming of this multilayer sheet to obtain a container. Among these, bottles obtained by the biaxial stretch blow molding method are typical, and can be obtained by blow molding a multilayer parison obtained by a multilayer coextrusion method or a multilayer injection molding method. In particular, it is practical to use multilayer injection to first inject the inner PET parison, then inject the outer layer only to the body and bottom portions of the parison, leaving only the PET layer at the mouth. (Effects of the Invention) According to the present invention, a multilayer container having the following excellent performance can be obtained (1) Since the innermost layer is made of a mixture of PET and PA,
A container that generates a small amount of acetaldehyde can be stably obtained by the extremely common method of mixing resins. (2) By using PEI or a mixture of PEI and PET for the outer layer, a container with higher gas barrier properties than ordinary PET containers can be obtained. (3) When adding PET to PEI in the outer layer,
The strength is significantly improved compared to PEI alone, and the uniformity of stretching is also increased, as PET is included as a common component in the outer and inner layers.
Both layers adhere firmly. (Example) Polyethylene terephthalate homopolymer (intrinsic viscosity [η] 0.76, melting point 225℃, glass transition temperature 70℃) was used as PET, and nylon 6 (hereinafter referred to as PA) was used as PET.
PA6) or nylon 66 (hereinafter referred to as PA66) is used as PEI, and ethylene isophthalate/ethylene terephthalate copolymer (isophthalic acid content 90 mol%) is used as the inner and outer layers of the bottle using a resin mixed in the amounts shown in the table. was molded. In addition, as a comparative example, a single-layer bottle made only of PET was molded. The mixture is prepared by dry blending resins in a predetermined proportion and extruding the mixture while kneading it using an extruder for pellet production to produce mixed resin pellets. Molding is carried out by first injecting the inner layer of PET and PA mixed pellets into a mold to form a bottomed cylindrical parison, and then using another mold to inject the outer layer material into the body and bottom portions of the parison. A two-layer parison was obtained. Next, the parison is blow molded to a height of 250 mm, a body diameter of 120 mm, a body thickness of approximately 0.4 mm, and an outer layer thickness ratio of 0.7.
It was made into a round bottom bottle. The following items were evaluated for each bottle. (1) Method for measuring the amount of acetaldehyde generated: After replacing the inside of the molded container with nitrogen gas, sealing it tightly, and leaving it in an atmosphere at 22°C for 24 hours,
The amount of acetaldehyde in the gas phase in the container is measured by the peak height of the gas chromatograph. When the peak height of the container to be measured is H, and the peak height of the container made only of PET is _H1 , the aceratodehyde reduction rate is ( _H1 -H)/ _H1x100 . (2) Gas barrier properties A bottle is filled with water containing 4 gas volumes of carbon dioxide gas, left in an atmosphere of 23℃ and 50% RH, and the amount of carbon dioxide gas escaping from the bottle is measured by the decrease in the bottle's internal pressure. It is expressed as the period (weeks) during which the internal pressure decreases by 15%.

[Table] As is clear from the results in the table, the bottles of the present invention in Examples 1 to 4 had a greater AA reduction rate of 70% than the normal PET bottle in Comparative Example 1, and the gas barrier properties also improved after 25 weeks. more and normal
PET bottle (same thickness, gas barrier properties approximately 12 weeks)
better than. Here, Example 1, in which the outer layer was made only of PEI, was somewhat inferior in drop strength. Further, in Example 3 in which 5 parts of nylon 6 was added, white turbidity was observed in the inner layer.

Claims (1)

[Claims] 1 The innermost layer is made of a mixture of ethylene terephthalate polyester resin and polyamide resin,
A multilayer container characterized in that the outer layer is made of an ethylene isophthalate polyester resin or a mixture of an ethylene isophthalate polyester resin and an ethylene terephthalate polyester resin.