JP2007223667A - Plastic container having gas barrier layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic container wherein separation between resin layers experienced in conventional multi-layer plastic containers is prevented while securing satisfactory oxygen gas barrier properties. <P>SOLUTION: The plastic container has at least one gas barrier layer between polyethylene terephthalate resin layers, and the gas barrier layer contains 5-15 parts by weight of a polyethylene terephthalate resin to 100 parts by weight of a polymetaxylene adipamide resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plastic container, and more particularly to a container having an oxygen gas barrier property.

  Conventionally, as one of packaging containers for filling and packaging various articles, there are various types of plastic containers molded by molding methods such as injection molding, extrusion molding, and blow molding. These plastic containers have various advantages such as light weight, resistance to breakage, low cost, easy manufacture, and mass production as compared with glass containers, and are widely used as packaging containers.

  While these plastic containers have the above-mentioned advantages, they have a drawback that they are inferior in gas shielding properties such as oxygen gas. Also, in the plastic container, plasticizers, stabilizers, other additives, residual monomers, etc. contained in the plastic composition may be eluted, which may affect the quality of the contents. There is also a problem. Various proposals have been made to solve the above problems.

  For example, in Japanese Patent Application Laid-Open No. 2003-136057 (Patent Document 1), a container is made of polymetaxylylene adipamide resin (hereinafter also referred to as (polyamide) MXD6), ethylene-vinyl alcohol copolymer resin, polyglycol or the like. A plastic container excellent in oxygen barrier properties in which a resin is used as an intermediate layer and a barrier layer is provided in the resin is disclosed. Also, Japanese Patent Publication No. 2-500846 (Patent Document 2) discloses a plastic container having an oxygen scavenging function by providing a resin layer containing polyester and nylon and cobalt metal. . Furthermore, a plastic container in which a gas barrier resin composition is coated on the surface of a plastic container to form a gas barrier resin film, or a plastic oxide in which a silicon oxide thin film is formed on the surface and inner surface of the plastic container body. Containers (Patent Documents 3 to 5) and the like have been proposed.

Such a multilayer plastic container tends to easily peel off the resin layer when the container is dropped or heated.
JP 2003-136057 A Japanese National Patent Publication No. 2-500846 Japanese Utility Model Publication No. 5-35660 JP 2000-43875 A JP 2000-117881 A

  An object of the present invention is to provide a plastic container that prevents peeling between resin layers in such a conventional multilayer plastic container while ensuring sufficient oxygen gas barrier properties.

  In a plastic container in which a polyethylene terephthalate resin layer is provided with a gas barrier layer mainly composed of a polymetaxylylene adipamide resin, the present inventors provide a polymetaxylylene adipamide resin 100 on the gas barrier layer. On the other hand, it has been found that by including 5 to 15 parts by weight of polyethylene terephthalate resin, it is possible to provide a plastic container that prevents separation between resin layers while ensuring sufficient oxygen gas barrier properties.

  Therefore, the present invention is a plastic container in which at least one gas barrier layer is provided in a polyethylene terephthalate resin layer, and the gas barrier layer is 5 to 15 with respect to the polymetaxylylene adipamide resin 100. It comprises polyethylene terephthalate resin in parts by weight.

Layer configuration diagram 1 plastic container shows a schematic example of a cross-section of the plastic container according to the invention. As shown in FIG. 1, the plastic container of the present invention typically has at least one gas barrier layer 2 provided in a resin layer 1.

  The resin constituting this resin layer is typically a polyethylene terephthalate resin layer.

Gas barrier layer The gas barrier layer provided in the plastic container of the present invention typically blocks or absorbs oxygen.

  The gas barrier layer is preferably 3 to 7% by weight based on the weight of the resin layer. If it is less than 3% by weight, the gas barrier performance cannot be sufficiently exhibited, and if it exceeds 7% by weight, the recyclability of the plastic container is lowered.

<Resin composition>
The gas barrier layer in the present invention comprises 5 to 15 parts by weight of polyethylene terephthalate resin with respect to 100 parts by weight of polymetaxylylene adipamide resin. If it is smaller than the above parts by weight, the effect of improving the adhesion between the gas barrier layer and the resin layer is not sufficiently exhibited, and peeling or the like is likely to occur. If it is larger than the above-mentioned parts by weight, the gas barrier properties will not be sufficiently exhibited.

<Catalyst>
In the gas barrier layer using the polymetaxylylene adipamide resin in the present invention, the polymetaxylylene adipamide resin may contain a complex salt of an inorganic acid salt or an organic acid salt containing a transition metal catalyst. preferable. Thus, the oxygen shielding effect is further improved by containing a complex salt containing a transition metal catalyst. As the transition metal catalyst, a cobalt compound can be preferably used.

  The gas barrier layer in the present invention preferably comprises 300 to 550 ppm of cobalt in polymetaxylylene adipamide resin. If it is less than 300 ppm, the effect of improving the gas barrier property by cobalt is not sufficiently exhibited. Moreover, if it is about 550 ppm, even if a polyethylene terephthalate resin is added, the gas barrier property normally required can be ensured, and in order to avoid wasting cobalt, 550 ppm or less is preferable.

  Examples of the cobalt compound to be added include cobalt stearate and cobalt neodecanoate.

<Other ingredients>
In the plastic container of the present invention, acetaldehyde and formaldehyde from the container may elute into the packing when placed in a high temperature environment such as a use application such as a hot warmer bender. Further, depending on the type of contents to be filled in the container, some may be altered by ultraviolet rays. In particular, when filling drugs, quasi-drugs, etc., the deterioration of the packing material due to ultraviolet rays becomes a problem.

  Therefore, the gas barrier layer constituting the plastic container of the present invention preferably contains a compound having an ultraviolet shielding function or an acetaldehyde absorption function. These compounds can be added to the resin layer constituting the plastic container or provided in the resin as an ultraviolet shielding layer. However, in consideration of the recyclability and functionality of the container, they are added to the gas barrier layer. It is preferable to do.

  As the compound having an ultraviolet shielding function, a commercially available ultraviolet absorber (for example, tinuvin) is preferably used. These ultraviolet absorbers can be formed by adding them as a master batch or liquid injection to the molten polymer at the time of container molding. Further, a resin capable of shielding ultraviolet rays, for example, polyethylene naphthalate (shielding at 380 nm or less) may be formed in multiple layers as a gas barrier layer. Furthermore, various wavelengths can be shielded by adding not only ultraviolet rays but also black, red and sepia colorants.

  Moreover, as a compound which has an acetaldehyde absorption function, AA Scavengers (made by ColorMatrix) etc. can be used suitably, These can be added to a molten polymer at the time of container shaping | molding.

Manufacturing method of plastic container The plastic container according to the present invention can be molded using molding methods such as extrusion molding, injection molding, blow molding, cast molding, thermoforming, etc., among these, It is preferable to form by biaxial stretch blow molding.

  The plastic container of the present invention is typically produced by a method of subjecting a preform (also called a preform) to biaxial stretch blow molding. Typically, a gas barrier layer can be formed in the polyethylene terephthalate resin layer by using a co-injection molding method in forming the preform.

  The co-injection molding method used in the present invention uses, for example, a hot runner nozzle schematically shown in FIG. 2, and the conditions are set so that the co-injection timing of polyethylene terephthalate resin and gas barrier resin is schematically shown in FIG. This can be done.

  Specifically, the hot runner nozzle 20 shown in FIG. 2 has two flow paths A and B. The flow path A further includes a central linear flow path A1 and a cylinder provided outside thereof. And is divided equally into the channel A2. The channel B is provided in a cylindrical shape between the two channels A1 and A2. A check valve 21 is provided at the upper end of the central flow path A1, and the check valve 21 is movable up and down due to the difference in resin pressure between the flow path A1 and the flow path B. When the flow rate is high, the flow path B can be opened. The flow path B opens to the flow path A 1, and the flow path A 1 merges upward to exit the hot runner nozzle 20 and communicate with the cavity 31 of the injection mold 30.

  The manufacturing process of the multilayer preform using the hot runner nozzle 20 as described above will be described with reference to the co-injection program shown in FIG. 3 and the schematic diagrams showing the co-injection states shown in FIGS. In this example, a polyethylene terephthalate resin (PET resin) is flowed through the flow path A, and a gas barrier resin is flowed through the flow path B. First, in step 1, polyethylene terephthalate resin is injected from the flow path A. At this time, as shown in FIG. 4, the check valve 21 of the hot runner nozzle 20 is closed by the injection pressure of the polyethylene terephthalate resin, and only the polyethylene terephthalate resin is injected from the flow paths A1 and A2. Next, in step 2, the injection rate of the polyethylene terephthalate resin is lowered, and in step 3, the gas barrier resin is injected from the flow path B while continuing the injection of the polyethylene terephthalate resin in the same manner as in step 2. At this time, since the injection pressure of the gas barrier resin is larger than the injection pressure of the polyethylene terephthalate resin, the check valve 21 opens according to the difference, and the gas barrier resin is injected accordingly. As shown in FIG. 5, the gas barrier resin injected in step 3 travels between the two polyethylene terephthalate resin layers 40 a and 40 b injected from the flow paths A 1 and A 2 to form a gas barrier resin layer 50. At this time, the gas barrier resin layer 50 proceeds between the two polyethylene terephthalate resin layers 40a and 40b without contacting the inner wall of the mold, so that the material temperature is less decreased and the fluidity is large. Therefore, the polyethylene terephthalate resin layer 40a, It moves at a speed faster than 40b. Further, when the injection rate of the polyethylene terephthalate resin is increased without stopping the injection of the gas barrier resin in step 4, as shown in FIG. 6, in addition to the polyethylene terephthalate resin layers 40a and 40b injected in step 3, a new polyethylene is added. The terephthalate resin layers 40c and 40d advance in the material. At this time, since the check valve 21 is somewhat closed by the injection pressure of the polyethylene terephthalate resin, the gas barrier resin is injected thinly. Moreover, since the polyethylene terephthalate resin layers 40c and 40d travel between the material layers, they move at a faster speed than the polyethylene terephthalate resins 40a and 40b. Next, in step 5, the injection of the gas barrier resin is stopped, and an amount of polyethylene terephthalate resin sufficient to fill the mold is injected into the state shown in FIG. 7, and finally, in the mold 30 as shown in step 6. The pressure (holding pressure) is applied and the injection is terminated. In order to produce such a multilayer preform, it is necessary to regulate and control the cylinder temperature at injection, cylinder pressure, the viscosity difference between the polyethylene terephthalate resin and the gas barrier resin, etc. Therefore, it is important to keep the temperature of the material constant.

  The plastic container according to the present invention preferably has a minimum thickness of 0.25 mm or more, more preferably 0.3 mm or more.

  It does not specifically limit as a form of the plastic container of this invention, It can be set as a bottle shape, cup shape, bowl shape, and other forms.

Articles Combined with Plastic Container In the present invention, the container may be covered with a shrink film or the like outside the container. By imparting ultraviolet and / or visible light shielding function to this shrink film, it is possible to obtain further ultraviolet shielding effect and the effect of shielding light of longer wavelength, and alteration due to ultraviolet rays etc. of pharmaceuticals and quasi drugs It can be applied to fillings that are easy to do. The shrink film is not limited to a transparent film, and a colored film such as black, sepia, or silver may be used. The entire container including the lid of the container may be covered.

  As the lid of the container combined with the plastic container according to the present invention, it is preferable to use a container having a gas barrier property like the container. For example, a lid using a liner material made of a film having a barrier property, or a lid in-molded using a film having a gas barrier property, and an aluminum cap may be used.

  Hereinafter, the plastic container according to the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  PET (polyethylene terephthalate resin) was used as the resin used for the resin layer. Polyamide MXD6 S6007 (polymetaxylylene adipamide resin, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as the resin used for the gas barrier layer, PET and / or cobalt stearate (manufactured by Wako Pure Chemical Industries, Ltd.) A mixture was used. For these resins, a co-injection molding machine (IN-90, manufactured by Kortec) was used to prepare a preform (preform) having a three-layer structure (PET resin layer / gas barrier layer / PET resin layer). At that time, the ratio of the gas barrier layer to each of these resin layers was kept constant at 5 wt%.

  From the obtained preform, plastic containers having a full injection capacity of 280 ml and 350 ml were prepared by biaxial stretch blow molding.

  The following evaluation was performed about each obtained container.

Peel test (drop test)
A 280 ml bottle was used and capped after 280 ml of water was filled. The bottle is stored in a thermostatic chamber (Espec: PL-2KP) with each temperature setting for one week, then dropped from the height of 50 cm or 100 cm once from the bottom and once from the side, and peeled off. Was confirmed. The test was performed with 10 pieces under each condition. In addition, heating cooling is a drop test after cooling to room temperature after storing at 60 ° C./1 week. The results are shown below.

  From the above results, it can be seen that the more the PET resin is mixed in the gas barrier layer, the better the peeling is. It is thought that the strength was increased by adding PET between the layers that had been pseudo-bonded so far, and increasing the number of completely bonded portions. In addition, the tendency is slightly improved when cobalt is added, but the peeling is improved. It is thought that PET and polyamide MXD6, which are difficult to mix, are more easily kneaded as a slip effect of cobalt stearate.

Peel test (heat resistance test)
In the same manner as the peel test (drop test), 60 ° C. for 1 week and 60 ° C. for 1 week were tested for heating and cooling. In addition, the following actual machine tests were conducted.

  A 350 ml bottle was used and capped after filling with 350 ml of water. Using a hot warmer TW-75 made by Nippon Heater, the dial was set to MAX and the liquid temperature was about 70 ° C. (55 ° C. when set to an appropriate temperature), and a severe condition test was performed.

This MAX setting was left for one week, and after one week, the heater was turned off to cool to room temperature. After cooling, it was confirmed whether the body or bottom of the bottle was peeled off. The results are shown below.

  From the above results, it was found that, in the heat resistance evaluation as well as the above drop test results, the addition of PET to the gas barrier layer has an effect of improving peeling. In the product to which cobalt was added, a more excellent effect appeared.

Oxygen permeation test (gas phase)
Under conditions of a temperature of 23 ° C. and a humidity of 40% RH, an oxygen permeation test was performed by a method known as the Mocon method using an 280 ml bottle using an oxygen permeation tester (OXTRAN, manufactured by MOCON). The results are shown below.

From the above results, the barrier improvement rate (BIF: Barrier Improvement Factor) calculated by dividing the numerical value before improvement by the numerical value after improvement is shown below.

  From the above results, it was found that the barrier property was improved by adding cobalt. Maintaining excellent barrier properties with a cobalt content of 300 ppm or more and a PET mixing amount of 15 parts by weight or less with a BIF of more than 10 times (if it is more than 10 times, there is an effect of preventing oxygen deterioration for some contents). I was able to.

Oxygen permeation test (liquid phase)
An 280 ml bottle was filled with water in an oxygen-free state (8 to 10 ppm) and stored in a thermostat (PL-4KP) at 60 ° C. for 1 to 4 weeks. Meanwhile, the transition of dissolved oxygen concentration in the liquid was measured using an oxygen analyzer (Hach Ultra Analytics).

  FIG. 8 shows dissolved oxygen (ppm) with the passage of storage period (unit, week) in a bottle container in which 0 to 20% of PET is mixed with polymetaxylylene adipamide resin containing 500 ppm of cobalt to form a gas barrier layer. It is a graph which shows how [] changed. FIG. 9 shows dissolved oxygen (ppm) with the passage of the storage period (unit, week) in a bottle container in which 0 to 20% of PET is mixed with polymetaxylylene adipamide resin containing 400 ppm of cobalt to form a gas barrier layer. It is a graph which shows how [] changed. FIG. 10 shows dissolved oxygen (ppm) with the passage of the storage period (unit, week) in a bottle container in which 0 to 20% of PET is mixed with polymetaxylylene adipamide resin containing 300 ppm of cobalt to form a gas barrier layer. It is a graph which shows how [] changed. When the tendency of oxygen absorption (decrease tendency) is seen, and it is less than the initial value of 9 ppm after 3 weeks, it can be evaluated that a temporary effect was observed.

  As can be seen from the graph, when 500 ppm of cobalt was included, a tendency of oxygen absorption was also observed, and even after adding PET, it was less than 9 ppm after 3 weeks. On the other hand, when the cobalt content was 400 and 300 ppm, the tendency of oxygen absorption was observed, but the mixture of PET 20% showed a value of 9 ppm or more after 3 weeks. Further, when the amount of PET resin mixed is large, a space for oxygen permeation is generated in the gas barrier layer, and the balance between the speed of permeation and absorption of oxygen cannot be maintained, and it was difficult to exert the effect.

It is a schematic sectional drawing of the plastic container of this invention. It is sectional drawing of the hot runner nozzle for co-injection molding methods, and an injection mold. It is a graph which shows a co-injection program. It is a schematic sectional drawing which shows the state (step 1) of co-injection. It is a schematic sectional drawing which shows the state (step 3) of co-injection. It is a schematic sectional drawing which shows the state (step 4) of co-injection. It is a schematic sectional drawing which shows the state (step 5) of co-injection. It is a graph which shows the relationship between the storage period of a bottle container, and the amount of dissolved oxygen. It is a graph which shows the relationship between the storage period of a bottle container, and the amount of dissolved oxygen. It is a graph which shows the relationship between the storage period of a bottle container, and the amount of dissolved oxygen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polyethylene terephthalate resin layer 2 Gas barrier layer 20 Hot runner nozzle 21 Check valve 30 Injection mold 31 Cavity 40a, 40b, 40c, 40d Polyethylene terephthalate resin layer 50 Gas barrier resin layer

Claims (7)

A plastic container comprising at least one gas barrier layer provided in a polyethylene terephthalate resin layer,
A plastic container, wherein the gas barrier layer comprises 5 to 15 parts by weight of polyethylene terephthalate resin with respect to 100 parts by weight of polymetaxylylene adipamide resin.   The plastic container according to claim 1, wherein the gas barrier layer comprises a complex salt of an inorganic acid salt or an organic acid salt containing a transition metal catalyst.   The plastic container according to claim 2, wherein the complex salt of an inorganic acid salt or an organic acid salt containing the transition metal catalyst is a cobalt compound.   The plastic container according to claim 3, wherein the gas barrier layer comprises 300 to 550 ppm of cobalt in polymetaxylylene adipamide resin.   The plastic container according to claim 3, wherein the cobalt compound is cobalt stearate.   The plastic container according to claim 1, wherein the gas barrier layer is 3 to 7% by weight of the polyethylene terephthalate resin layer.   The plastic container according to claim 1, which is obtained by subjecting a preform formed by a co-injection molding method to biaxial stretch blow molding.

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