JPH06104732B2 - Processing method for thermoplastic polyester containers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a thermoplastic polyester container having a biaxially stretched container body (hereinafter referred to as a polyester container) with excellent gas barrier properties, particularly with respect to oxygen. Another object of the present invention is to provide a treatment method for introducing gas barrier properties, and to provide a method for easily and surely obtaining a polyester container exhibiting excellent gas barrier properties regardless of the humidity in the atmosphere.

[Prior Art] A polyester container having a biaxially stretched container body is non-toxic, and has gas barrier properties and water impermeability superior to those of other synthetic resin molded products,
By virtue of its glassy appearance, cosmetic containers,
It is widely used as a container for liquid seasonings, a container for carbonated beverages such as beer, and a container for pharmaceuticals.

[Problems to be Solved by the Invention] The polyester container has a gas barrier property, particularly oxygen, when the stored food or drug filling is stored in a stable state for a long period of time. It has a drawback that the gas barrier property against is not sufficient. For this reason, it has been attempted to improve the gas barrier property of oxygen and carbon gas by forming a synthetic resin coated with ethylene / vinyl alcohol copolymer on at least the outer surface of the body wall of the polyester container. .

Thus, the gas barrier property of the synthetic resin layer coated with the ethylene / vinyl alcohol copolymer is good under a relative humidity of about 70% RH or less, but is higher than 70% RH. Under relative humidity, the gas barrier property tends to decrease as the relative humidity increases, and there is a drawback that the gas barrier property under high humidity is not sufficient.

[Means for Solving the Problems] The present invention is, of course, not only under moderate relative humidity but also under high relative humidity exceeding 70% RH,
It is possible to provide a treatment method which makes a polyester container having a property of excellent gas barrier properties against oxygen and carbon dioxide gas.

The material of the polyester container targeted by the present invention is a molded product of saturated polyester typified by ethylene terephthalate, and a cylindrical molded body commonly referred to as a polyson is used in a container body molding die. A polyester container obtained by axially stretching or blow-molding the parison under heating capable of expanding the parison and expanding the parison to about 5 to 9 times, and having biaxial orientation by biaxial stretching. Is.

According to the inventions of claims 1 to 6, after forming a first coated synthetic resin layer of an ethylene / vinyl alcohol copolymer on the outer surface of the body of the polyester container,
Of the first coated synthetic resin layer by covering the surface of the coated synthetic resin layer with a heat-shrinkable synthetic resin film having transparency and moisture resistance and heating and shrinking the heat-shrinkable synthetic resin film. It is a treatment method for obtaining a polyester container excellent in gas barrier property and moisture proof by tightening it on the outer surface of the body part of the polyester container through.

Further, the invention of claims 7 to 12 is characterized in that after forming a first coating synthetic resin layer by an ethylene / vinyl alcohol copolymer on the outer surface of the body of a polyester container, the first coating synthesis is carried out. An adhesive layer, a synthetic resin film or a paper label, one of which has moisture resistance, is attached to the surface of the resin layer, and a synthetic resin film or a paper label is affixed with the adhesive layer to provide excellent gas barrier properties and moisture resistance It is a processing method for obtaining a polyester container.

The constitution of the processing method of the present invention will be described in detail below. The inventions of claims 1 and 2 apply a coating agent consisting of a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component to the outer surface of the polyester container body, followed by drying, Thickness 0.5-100 μm, preferably 1-
A first coated synthetic resin layer having a thickness of about 20 μm is formed. The first
Drying of the coated synthetic resin layer after application is usually carried out at 40 to 120 ° C, particularly preferably at 50 to 90 ° C.

Then, the surface of the first coated synthetic resin layer is covered with a heat-shrinkable synthetic resin film having moisture resistance and transparency, and heated by heating means such as hot air to shrink the heat-shrinkable synthetic resin film. Then, the surface of the outer wall of the polyester container is clamped through the first coated synthetic resin layer.

The coating agent comprising a solvent solution containing the ethylene-vinyl alcohol copolymer used as the film-forming component used in the present invention is generally an ethylene-vinyl alcohol copolymer having a solubility index Sp of 11.0 or more, 2 or 3.
Mixed solvent of at least one kind, for example, water / alcohol mixed solvent,
Particularly preferably, those having a concentration of about 1 to 20% by weight dissolved in a mixed solvent of water / methyl alcohol, water / normal propyl alcohol, water / isopropyl alcohol and the like are used.

Further, the heat-shrinkable synthetic resin film having moisture resistance and transparency used in the present invention, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyvinylidene chloride, polyacrylonitrile or a copolymer thereof or Acrylonitrile / styrene /
A synthetic resin film of a butadiene copolymer can be used.

In the treatment method of the present invention, it is preferable that the outer surface of the body portion of the polyester container is subjected to a degreasing treatment in advance so that a uniform coated synthetic resin layer can be obtained before applying the treatment step.

The first coated synthetic resin layer made of an ethylene / vinyl alcohol copolymer has a vinyl alcohol unit of 40%.
When the content is up to 85 mol%, the tendency of the oxygen barrier property to decrease with an increase in the relative humidity of polyvinyl coal can be compensated to some extent with the other base of the copolymer, polyethylene. Can cover but is not always sufficient.

Therefore, the invention of claim 1 is a transparent heat-shrinkable synthetic resin film (thickness: about 30 μm) having moisture resistance on the surface of the first coating synthetic resin layer made of the ethylene / vinyl alcohol copolymer. And shrinking the film by heating it with a heating means such as hot air to tighten the film on the outer wall surface of the polyethylene container through the first coated synthetic resin layer. The effect of the coated synthetic resin layer and the effect of the moisture-proof and heat-shrinkable thermoplastic resin film are synergized to provide a polyester container which exhibits a sufficient gas barrier property even at a high relative humidity.

In the inventions of claims 3 and 4, prior to the coating operation for forming the first coated synthetic resin layer, at least the outer surface of the body wall of the polyester container is subjected to flame treatment and corona discharge treatment in advance. Alternatively, it is subjected to adhesion improving treatment such as plasma treatment.

Further, the inventions of claims 5 and 6 are such that ethylene / vinyl acetate copolymer, vinyl chloride polymer, vinyl acetate polymer, vinyl chloride / acetic acid are preliminarily formed on at least the outer surface of the body wall of the polyester container. A primer layer is formed by applying a coating agent containing a thermoplastic synthetic resin such as a vinyl copolymer, an isocyanate-based polymer, soluble nylon, chlorinated polyolefin, and saturated polyester as a film-forming component and drying it.

An ethylene / vinyl alcohol copolymer is used on the surface of the invention of claims 3 and 4 which has been subjected to the adhesion-improving treatment or on the surface of the primer layer of the inventions of claims 5 and 6. By the treatment for forming the first coated synthetic resin layer, the first coated synthetic resin layer can be surely laminated and adhered to the outer surface of the polyester container, and a polyester container excellent in gas barrier property and moisture proof can be obtained. it can.

Next, according to the inventions of claims 7 and 8, the same as the above, after forming a first coated synthetic resin layer made of an ethylene / vinyl alcohol copolymer on the outer surface of the polyester container, the adhesion is performed. A synthetic resin film or a paper label is attached using the agent layer. Thus, at least one of the adhesive layer, the synthetic resin film, and the paper label is moisture-proof. That is, claim 7
In the inventions of the items 8 and 9, in place of the heat-shrinkable synthetic resin film having a moisture-proof property, at least one of an adhesive, a synthetic resin film, and a paper label having a moisture-proof property is bonded to the first coating composition. It is adhered to the outer wall surface of the polyester container through the resin layer, and the moisture-proof effect of the first coated synthetic resin layer and the moisture-proof effect of the adhesive, the synthetic resin film or the paper label are synergistically enhanced. It is possible to obtain a polyester container exhibiting a sufficient gas barrier property even under the relative humidity of.

As the moisture-proof adhesive layer, for example, an epoxy resin adhesive, a polyurethane adhesive, an acrylic resin adhesive, a rubber adhesive, a hot-melt adhesive, or the like can be used, and a moisture-proof synthetic resin can be used. As the film, a general film known as this type of film can be used.

According to the inventions of claims 9 and 10, prior to the coating operation for forming the first coated synthetic resin layer, at least the outer surface of the body wall of the polyester container is preliminarily subjected to flame treatment and corona discharge treatment. Or, it is subjected to adhesion improving treatment such as plasma treatment.
The invention of claim 12 is an ethylene / vinyl acetate copolymer, a vinyl chloride polymer, a vinyl acetate polymer, a vinyl chloride / vinyl acetate copolymer, an isocyanate-based polymer, a soluble polymer, which is previously soluble on at least the outer surface of the body wall of the polyester container. Nylon,
A primer layer is formed by applying a coating agent containing a thermoplastic synthetic resin such as chlorinated polyolefin or saturated polyester as a film component, and drying it to form a primer layer. The first coated synthetic resin layer made of an alcohol copolymer is formed, and by these treatments, the first coated synthetic resin layer can be surely laminated and adhered to the outer surface of the polyester container.

[Examples] Specific actions and effects of the method of the present invention will be described below based on examples.

Example 1 A bottomed cylindrical parison of polyethylene terephthalate was molded into a bottle-shaped polyester container having the following narrow neck in a biaxially stretch blow molding mold.

Container weight: 32g Standard capacity: 500cc Surface area: 354cm ³ Container body wall thickness: 0.39mm Result of measuring oxygen permeability of the container by MOCON method 0.027cc / d
It was ay. However, the measurement is performed at atmospheric pressure (O ₂ : 0.21 atm), and the relative humidity is 100% RH inside the container and 50% RH outside air atmosphere.
Met.

After removing oil and fat components and dust adhering to the outside of the container with Daiflon, ethylene.
A vinyl alcohol copolymer solution (7% by weight) was applied by a dipping method and then dried at 65 ° C. for 5 minutes to form a first coated synthetic resin layer of ethylene vinyl alcohol copolymer having a thickness of about 6 μm. The surface is covered with a heat-shrinkable resin film of acrylonitrile / styrene / butadiene copolymer having a thickness of about 30 μm and heated to about 80 ° C., and the film is shrunk to the surface of the first coated synthetic resin layer. Tightened to obtain a polyester container.

The oxygen permeation rate of the obtained polyester container was 0.011 cc / day as a result of measuring relative humidity in the container at 100% RH, relative humidity in the outside air atmosphere at 50% RH and atmospheric pressure, and relative humidity in the outside air atmosphere. At 80% (others are the same as the above measurement conditions)
It was 0.016cc / day.

Example 2 A first coated synthetic resin layer of the same ethylene / vinyl alcohol copolymer was formed on the outer surface of the same polyester container as in Example 1, and a polyurethane-based adhesive was applied to the surface of the first coated synthetic resin layer. About 30 μm thick with coating agent
Of the acrylonitrile / styrene / butadiene copolymer is covered with a heat-shrinkable film, then heated to about 80 ° C to shrink the heat-shrinkable film, and a polyester adhesive is used to adhere the polyester. I got a container.

The oxygen permeation rate of the obtained polyester container was 0.0080 cc / day as a result of measuring relative humidity in the container at 100% RH, relative humidity in the outside air atmosphere at 50% RH and atmospheric pressure, and relative humidity in the outside air atmosphere. At 80% (others are the same as the above measurement conditions)
It was 0.011cc / day.

[Operations and Effects of the Invention] The present invention is configured as described above, and a first coated synthetic resin layer made of an ethylene / vinyl alcohol copolymer is formed on the outer surface of a polyester container, and the surface is heat-shrinkable. The synthetic resin film is heated and shrunk to be tightened on the outer surface of the polyester container, or a synthetic resin film having moisture resistance or a paper label is attached via an adhesive. The effect of the resin layer and the moisture-proof heat-shrinkable synthetic resin film or the moisture-proof adhesive, the effects of the synthetic resin film or the paper label are synergistically combined with each other in a low-humidity atmosphere or even in a high-humidity atmosphere An excellent gas barrier property against oxygen and carbon dioxide gas can be always expressed.

Further, the present invention forms a first coated synthetic resin layer on the outer surface of a polyester container, laminates a heat-shrinkable synthetic resin film having moisture resistance on the surface, and heats the film to tighten the outer surface of the polyester container. Or a polyester container having an excellent gas barrier property that is not reliably affected by the humidity in the atmosphere by a simple means of attaching a moisture-proof synthetic resin film or a paper label via an adhesive. Can be obtained.

Claims (12)

[Claims] 1. A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component on the outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body. Is coated and dried to form a first coated synthetic resin layer, and then the surface of the first coated synthetic resin layer is covered with a moisture-proof transparent heat-shrinkable synthetic resin film, The heat shrinks the heat-shrinkable synthetic resin film,
A method for treating a thermoplastic polyester container, which comprises tightening the outer surface of the body wall of the thermoplastic polyester container through the coated synthetic resin layer of. 2. The method for treating a thermoplastic polyester container according to claim 1, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having a vinyl alcohol unit content of 40 to 85 mol%. 3. The outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body is subjected to flame treatment, corona discharge treatment, or plasma treatment, and thereafter, to the treated surface. A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component is applied and dried to form a first coated synthetic resin layer, and then the surface of the first coated synthetic resin layer is coated. Covering with a transparent heat-shrinkable synthetic resin film having moisture-proof property and heating to shrink the heat-shrinkable synthetic resin film, and the thermoplastic polyester through the first coated synthetic resin layer. A method for treating a thermoplastic polyester container, which comprises tightening the outer surface of a body wall of the container. 4. The method for treating a thermoplastic polyester container according to claim 3, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having a vinyl alcohol unit content of 40 to 85 mol%. 5. An ethylene / vinyl acetate copolymer, vinyl chloride polymer, vinyl acetate polymer, vinyl chloride is formed on the outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body. Forming a primer layer with a coating agent containing a thermoplastic synthetic resin such as vinyl acetate copolymer, isocyanate-based polymer, soluble nylon, chlorinated polyolefin, and saturated polyester as a film-forming component, and thereafter, on the primer layer surface , A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component is applied and dried to form a first coated synthetic resin layer, and then the surface of the first coated synthetic resin layer. Is covered with a transparent heat-shrinkable synthetic resin film having a moisture-proof property, and the heat-shrinkable synthetic resin film is heated. The resin film to contract, the first
A method for treating a thermoplastic polyester container, which comprises tightening the outer surface of the body wall of the thermoplastic polyester container through the coated synthetic resin layer of. 6. The method for treating a thermoplastic polyester container according to claim 5, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having a vinyl alcohol unit content of 40 to 85 mol%. 7. A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component on the outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body. Is applied and dried to form a first coated synthetic resin layer, and then a synthetic resin film or a paper label is attached to the surface of the first coated synthetic resin layer via an adhesive layer. A method for treating a thermoplastic polyester container, wherein at least one of the adhesive, the synthetic resin film, and the paper label is moisture-proof. 8. The method for treating a thermoplastic polyester container according to claim 7, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having a vinyl alcohol unit content of 40 to 85 mol%. 9. The outer surface of the body wall of a thermoplastic polyester container having a biaxially stretched container body is subjected to flame treatment, corona discharge treatment, or plasma treatment, after which the treated surface is A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component is applied and dried to form a first coated synthetic resin layer, and then on the surface of the first coated synthetic resin layer. A thermoplastic polyester comprising a synthetic resin film or a paper label attached via an adhesive layer, wherein at least one of the adhesive or the synthetic resin film or the paper label is moisture-proof. Processing method of container. 10. The method for treating a thermoplastic polyester container according to claim 9, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having a vinyl alcohol unit content of 40 to 85 mol%. 11. An ethylene / vinyl acetate copolymer, a vinyl chloride polymer, a vinyl acetate polymer, a vinyl chloride is provided on the outer surface of the body wall of a thermoplastic polyester container having a container body that is biaxially stretched. Forming a primer layer with a coating agent containing a thermoplastic synthetic resin such as vinyl acetate copolymer, isocyanate-based polymer, soluble nylon, chlorinated polyolefin, and saturated polyester as a film-forming component, and thereafter, on the primer layer surface , A coating agent comprising a solvent solution containing an ethylene / vinyl alcohol copolymer as a film-forming component is applied and dried to form a first coated synthetic resin layer, and then the first
On the surface of the coated synthetic resin layer, a synthetic resin film or a paper label is attached via an adhesive layer, and at least one of the adhesive, the synthetic resin film and the paper label is moisture-proof. A method for treating a container made of thermoplastic polyester, which is characterized in that 12. The method for treating a thermoplastic polyester container according to claim 11, wherein the ethylene / vinyl alcohol copolymer is an ethylene / vinyl alcohol copolymer having 40 to 85 mol% of vinyl alcohol units.