JP2002002649A - Polyethylene terephthalate resin container - Google Patents

Abstract

(57) [Summary] [Problem] To provide a pet resin container which can prevent a substance impregnated in a recycled pet resin from being eluted into the contents, can be inexpensive, and can use a large amount of the recycled pet resin. A pet resin containing a recycled pet resin obtained by regenerating a used pet resin container is biaxially stretched. The inner surface 6 includes a coating layer made of at least one of amorphous carbon, amorphous silicon, and silicon oxide. The coating layer is formed by a plasma CVD method. The regenerated pet resin has an intrinsic viscosity of 0.70 or more in the regenerating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyethylene terephthalate resin container using a recycled polyethylene terephthalate resin.

[0002]

2. Description of the Related Art A bottle obtained by biaxially stretching a polyethylene terephthalate resin (hereinafter sometimes abbreviated as a PET resin) has excellent mechanical strength, transparency, gas barrier properties, and the like as compared with other plastic containers. In addition, they are less likely to break than glass containers and are lightweight, so they are used for food and drink containers and the like.

However, if the pet resin container is discarded after being used as a food and drink container, it is bulky and does not easily weather, which may cause environmental pollution. Although it is conceivable to perform incineration treatment after collection, there is not always a consensus on so-called thermal recycling in which pet resin is incinerated to recover thermal energy. Therefore, it has been studied to collect used PET resin bottles, regenerate the PET resin, and use the recycled PET resin as a raw material for molded articles.

[0004] Conventionally, as a regenerated pet resin regenerated from a used PET resin bottle, for example, a flake material obtained by forming a recovered used PET resin bottle into a flake shape, and the flake material is extruded. There is known a pellet material obtained by pelletizing the flake material, a mash material obtained by crushing the flake material with a crush mixer, adding water, and granulating the flake material by frictional heat. The recycled pet resin is, for example, formed into a preform for blow molding, and is molded into a bottle or the like by a normal biaxial stretch blow molding method or the like.

[0005] By the way, the contents of the previous use, or various substances contained intentionally or accidentally from the previous use to the collection after the previous use are collected on the used PET resin bottle. I have. The container wall of the PET resin bottle is in a porous state in which microscopic holes that cannot be discerned by the naked eye are formed, and when the various substances permeate into the microscopic holes, they are in a state of the flake material or the like. It cannot be easily removed by washing. As a result, in a bottle molded using recycled PET resin recycled from the used PET resin bottle, there is a possibility that various substances permeating into the minute pores may elute into the contents,
There is a problem that it is not hygienic.

In order to solve the above problem, for example, there has been proposed a method of mechanically or chemically removing various substances adhering to the used PET resin bottle. For example, there are a method of mechanically washing the inner and outer surfaces of the used PET resin bottle to remove surface deposits, a method of degassing the recycled PET resin in a molten state, and a method of heating as a pellet material. .

According to the method, it is said that various substances adhering to the used PET resin bottle can be removed to the extent that they do not affect the human body even under the worst conditions. However, it is unacceptable for consumers to use bottles molded from recycled PET resin containing various substances attached to used PET resin bottles again as food and beverage containers. It is thought that there is.

On the other hand, JP-A-6-255654, JP-B-6-6911, and JP-B-2598858 disclose a recycled pet resin as an intermediate layer and provide a new pet resin (virgin pet) on both sides of the intermediate layer. ) Has been proposed. According to the PET resin bottles described in the above publications, since the recycled pet resin layer is covered with a new pet resin layer, even if the recycled pet resin is impregnated with a hygienic object, the substance is Elution into the contents can be prevented.

However, in order to form a PET resin bottle having the above-described structure, first, a multilayered preform in which recycled PET resin is used as an intermediate layer and a new PET resin layer is disposed on both sides of the intermediate layer is formed. And there is an inconvenience that an increase in manufacturing cost is inevitable because a new injection molding machine is required. Further, in the PET resin bottle having the above-described configuration, the recycled PET resin is used only for the intermediate layer of the multilayer structure, and thus its usage is limited to at most about 40% by weight based on the total weight of the bottle. It is inconvenient that it is difficult to use.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances. Accordingly, it is possible to prevent a substance impregnated in a recycled polyethylene terephthalate resin from being eluted into the contents. An object of the present invention is to provide a container made of polyethylene terephthalate resin that can be used in a large amount.

[0011]

In order to achieve the above object, a polyethylene terephthalate resin container according to the present invention is a polyethylene containing a recycled polyethylene terephthalate resin obtained by regenerating a used polyethylene terephthalate resin container. In a container obtained by biaxially stretching a terephthalate resin, at least one of amorphous carbon, amorphous silicon or silicon oxide is provided on the inner surface side.
It is characterized by having a coating layer made of a seed.

The pet resin container of the present invention may have a shape such as a bottle, and may be molded only with the recycled pet resin, or molded with a pet resin obtained by mixing the recycled pet resin with a new (virgin) pet resin. It may be. According to the pet resin container of the present invention, since the coating layer is provided on the inner surface side, it is possible to prevent various substances permeating the recycled pet resin from being eluted into the contents. Therefore, the pet resin container of the present invention can be used as a container for food and drink.

[0013] The coating layer made of at least one of amorphous carbon, amorphous silicon and silicon oxide,
Although it can be formed by various known methods, it is preferably formed by a plasma CVD method. According to the plasma CVD method, since the coating layer can be formed by the molecules in the plasma state, it is possible to effectively prevent various substances permeating the recycled pet resin from being eluted into the contents.

The recycled pet resin obtained by regenerating the used PET resin container has a reduced intrinsic viscosity. If the preform is directly formed and blow-molded, the crystallization speed of the resin increases. The product becomes cloudy,
In some cases, a predetermined transparency cannot be obtained or a predetermined mechanical strength cannot be obtained. Therefore, in the pet resin container of the present invention, the recycled polyethylene terephthalate resin preferably has an intrinsic viscosity of 0.70 or more in the regeneration treatment, thereby preventing the decrease in the transparency or mechanical strength. can do.

Examples of the method for increasing the intrinsic viscosity of the recycled pet resin to 0.70 or more include, for example, a method of solid-phase polymerization of the recycled pet resin in a flake material or a pellet material.
A method of mixing a high-viscosity resin such as a new pet (virgin pet) resin can be used. In order to increase the transparency, there is a method of adding a non-crystalline copolymer.

[0016]

Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory sectional view of a PET resin bottle of the present embodiment, and FIG. 2 is an explanatory sectional view showing a method of manufacturing the PET resin bottle of the present embodiment.

The PET resin bottle 1 of the present embodiment is obtained from a recycled PET resin obtained by regenerating a used PET resin container, and as shown in FIG.
A mouth 3 having a screw portion 2 on the outer peripheral side, a body 4 connected to the mouth 3, and a bottom 5 connected below the body 4 and serving as a grounding portion, and amorphous carbon and amorphous silicon are provided on an inner surface 6. Alternatively, a coating layer (not shown) made of at least one kind of silicon oxide is provided.

Next, the PET resin bottle 1 of the present embodiment will be described.
A method of manufacturing the device will be described.

First, the collected used PET resin bottle is pulverized to produce a flaky flake material having a maximum length of about 10 mm. The used PET resin bottle is pulverized until the obtained flake material passes through a screen having an opening of 8 mm so as not to mix an excessively large flake material.

The flake material obtained from the recovered used PET resin bottle generally has a reduced intrinsic viscosity, and if left as it is, the physical properties of the bottle obtained by blow molding are low. Then, the physical properties of the bottle can be enhanced by solid-phase polymerization of the flake material to make the intrinsic viscosity 0.70 or more, preferably 0.75 or more equivalent to that of a virgin pet.

The flake material is heated and crystallized in an inert gas at 130 to 150 ° C. for 1 to 2 hours, for example, in a preheating tank for 5 to 7 hours in an inert gas at 150 to 160 ° C. After being heated and adjusted to a predetermined water content, the water is transferred to the main heating tank, and in the main heating tank, for example, 210 to 23.
The polymer is solid-phase polymerized by heating with an inert gas at 0 ° C., and then cooled. The reason why the inert gas is used for the heating is to prevent oxidation of the pet resin heated to a high temperature, and nitrogen is usually used as the inert gas. The adjustment of the water content is for preventing the hydrolysis of the pet resin heated to a high temperature for the solid-phase polymerization, and is usually performed so that the water content in the crystallized pet resin is 30 ppm or less. Will be

The detailed method of the solid phase polymerization is described in JP-A-6-184291 and JP-A-6-255645.

Next, the flake material is extruded by an extruder and processed into a pellet material, and the pellet material is injection-molded by an injection molding machine to be processed into a preform 7 shown in phantom in FIG. The preform 7 is blow-molded in a mold (not shown) by a biaxial stretching blow method known per se, and is formed into the shape of the PET resin bottle 1 shown in FIG.

However, at this time, the coating layer of the amorphous carbon, amorphous silicon, silicon oxide or the like has not yet been formed on the inner surface 6 of the PET resin bottle 1. Therefore, a PET resin bottle on which the coating layer is not formed is shown as a PET resin bottle 11 in FIG.

Then, the PET resin bottle 11 is
The coating layer is accommodated in the coating layer forming apparatus 12 shown in FIG. 2 and a coating layer (not shown) is formed on the inner surface 13. The coating layer forming device 12 includes a processing chamber 14 that accommodates and seals the PET resin bottle 11 and a microwave generator 15 provided on an outer wall of the processing chamber 14. The portion of the outer wall of the processing chamber 14 where the microwave generator 15 is provided is made of a microwave permeable material 15a.

The processing chamber 14 is provided with an exhaust pipe 16 connected to a vacuum pump (not shown) and a source gas supply conduit 17 connected to a source gas tank (not shown). The PET resin bottle 11 is introduced from the mouth 2 into the inside. Further, the processing chamber 14
Is provided with a flat plate 18 inside, and the mouth portion 2 of the accommodated PET resin bottle 11 is locked in a hole 19 of the flat plate 18.

When the coating layer is formed on the inner surface 13 of the PET resin bottle 11 by the coating layer forming device 12, first, the PET resin bottle 1 is inserted into the hole 19 of the flat plate 18.
The mouth portion 2 of the cartridge 1 is locked, the PET resin bottle 11 is accommodated in the processing chamber 14, and the processing chamber 14 is sealed. Next, a vacuum pump (not shown) is operated to evacuate the processing chamber 14 through the exhaust pipe 17 to make the interior of the processing chamber 14 vacuum.
Supplies the raw material gas for the coating layer. Then, by activating the microwave generator 15 and irradiating a predetermined microwave, a coating layer is formed on the inner surface 13 of the PET resin bottle 11, and the PET resin bottle 1 shown in FIG. 1 is obtained. The coating layer has a thickness of 50 to 3000 to prevent the substance permeating the recycled pet resin from being eluted into the contents.
Preferably, the thickness is Å.

When the coating layer is made of amorphous carbon, the raw material gas may be a gaseous or liquid aliphatic hydrocarbon, aromatic hydrocarbon, oxygen-containing hydrocarbon, or the like at room temperature.
Nitrogen-containing hydrocarbons and the like can be used, and specific examples include carbon compounds such as ethylene, acetylene, methane, ethane, propane, benzene, toluene, xylene, and cyclohexane. The carbon compound forms a coating layer made of polymeric amorphous carbon by irradiating the microwave in the processing chamber 14.

Further, when the coating layer is made of amorphous silicon, silane, disilane,
Siloxane and disiloxane compounds can be suitably used. When the coating layer is a silicon oxide, silane, disilane, tetraalkoxysilane, dialkoxysilane, tetraalkyldisiloxane, and hexaalkyldisiloxane compounds can be suitably used as the source gas. .

The raw material gas may be used alone.
You may mix and use more than one kind. Further, the source gas is:
Oxygen, may be used in combination with a gas such as hydrocarbons, argon,
It may be diluted with a rare gas such as helium before use.

Although the coating layer forming apparatus 12 irradiates the raw material gas introduced into the processing chamber 14 with microwaves to form the coating layer, a PET resin bottle is used instead. High-frequency power may be applied between an internal electrode provided near 11 and an external electrode provided on an outer wall of the processing chamber 14. According to the method of applying the high frequency power, when the source gas is the carbon compound, a coating layer made of amorphous carbon having no polymer property is formed.

The constitution of an apparatus for forming a coating layer of amorphous carbon, amorphous silicon or silicon oxide is described in JP-A-8-509166 and JP-A-2-700.
No. 59, JP-A-8-53117, etc., there are detailed descriptions, and the apparatus described in the above-mentioned publication can be appropriately modified and used for forming the coating layer of the present embodiment.

Next, a pet resin bottle 1 of the present embodiment as an example having the coating layer of 0.1 μm in thickness and a pet resin as a comparative example having no coating layer formed thereon The elution of various substances permeating the recycled pet resin into the contents was compared between the bottle and the bottle. The PET resin bottles of Examples and Comparative Examples blow-molded from the preform 7 contain a trace amount of antimony as a polymerization catalyst, and contain acetaldehyde due to the thermal decomposition of the pet resin accompanying the heat history by the blow molding. In. Therefore, by comparing the elution of the antimony and the acetaldehyde, an index of the elution of various substances permeating the recycled pet resin into the contents was used.

For the antimony, the PET resin bottles of Examples and Comparative Examples filled with water as contents were kept at 95 ° C. for 30 minutes, and then the concentration of antimony in the contents was measured. As for the acetaldehyde, the PET resin bottles of Examples and Comparative Examples filled with water as contents were kept at 70 ° C. for 180 minutes, and further kept at room temperature for 180 minutes, and then the concentration of acetaldehyde in the contents was reduced. It was measured. Table 1 shows the results.

[0035]

[Table 1]

As shown in Table 1, according to the PET resin bottle 1 of the present embodiment having the coating layer, the PET resin bottle 11 on which the coating layer was not formed, the antimony and the acetaldehyde were added to the contents. It is clear that the eluted concentration of is 1/10 or less. Therefore, it is considered that the PET resin bottle 1 of the present embodiment provided with the coating layer also has an excellent effect of preventing the elution of various substances permeating the recycled pet resin into the contents.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing one configuration example of a polyethylene terephthalate resin container of the present invention.

FIG. 2 is an explanatory sectional view showing one method for producing the polyethylene terephthalate resin container of the present invention.

[Explanation of symbols]

1: polyethylene terephthalate resin container; 6: inner surface; 7: preform.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) // C08L 67:00 B65D 1/00 BF Term (Reference) 3E033 AA01 BA18 BB08 CA03 CA06 CA16 CA18 DA03 DB01 DD01 EA04 EA10 GA02 4F006 AA35 AB72 AB73 AB74 BA11 CA07 DA01 EA03 4F100 AK43A AT00B BA02 DA01 EJ38A JL16

Claims (2)

[Claims] 1. A container obtained by biaxially stretching a polyethylene terephthalate resin containing a recycled polyethylene terephthalate resin obtained by regenerating a used polyethylene terephthalate resin container, wherein amorphous carbon, amorphous silicon Alternatively, a container made of polyethylene terephthalate resin, comprising a coating layer made of at least one kind of silicon oxide. 2. A coating layer comprising at least one of amorphous carbon, amorphous silicon and silicon oxide,
2. The polyethylene terephthalate resin container according to claim 1, wherein the container is formed by a plasma CVD method.