JP2001114354A - Foamed container body and foamed container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed container body and a foamed container of superior bonding properties when a cover member is stuck on the container body. SOLUTION: A polyolefin foamed container body 1 is used for sealing a direct cover member 20 on the periphery of an opening, and at least an edge section 2 on the periphery of the opening is provided with a non-foamable layer, and the surface roughness of the non-foamable layer is Ra<=4 μm and its thickness is 5 μm or more, and also a foamed container thereof is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed container and a foamed container, and more particularly to a polyolefin foamed container and a foamed container capable of storing foods and the like therein.

[0002]

2. Description of the Related Art Cups, trays, and other containers for home meal replacement (HMR), which are cooked foods heated using a microwave oven, have excellent lightness and heat insulation properties that can be touched by hand after heating. Are widely used, and polystyrene foams are widely used at present.

[0003] However, the heat resistance of polystyrene is not yet sufficient, and polyolefin resin foams, particularly polypropylene foams having high heat resistance, have been increasingly substituted.

As foams of polyolefins such as polyethylene and polypropylene, foams using chemical blowing agents such as azodicarbonamide compounds and nitroso compounds, and low-boiling aliphatic hydrocarbons such as propane and butane are used as blowing agents. Known foams and foams using carbon dioxide are known.

[0005] Of these, the use of a chemical foaming agent is not preferable in terms of cost, and it is conceivable to use carbon dioxide as a foaming agent.

[0006]

However, when carbon dioxide gas is used as a foaming agent, the foam is easily broken in the foaming step, and it is difficult to produce a foam itself. Polypropylene, which is relatively easy to make into a foam, is also known,
The foam sheet obtained by foaming carbon dioxide gas by the conventional production method using such polypropylene has insufficient vacuum moldability. Problems such as a decrease in the uniformity of the thickness, a decrease in the strength and an adiabaticity occur, and as a result, only a container having a large surface roughness can be obtained.

[0007] By the way, in the food container, the contents are stored in a container using a foam, and then the opening of the container is closed by a lid member.
The adhesion between the lid member and the container must be worse,
The sealing property is not sufficient, and as a result, the contents are altered or deteriorated. Therefore, when the pressing force between the periphery of the container body opening and the lid member is increased in order to enhance the adhesiveness, the container body is broken, or the adhesive strength between the two becomes too high, and the lid member becomes difficult to peel off. However, there is a problem that the yield is lowered and the product cannot withstand actual production.

Accordingly, an object of the present invention is to provide a foamed container and a foamed container which are excellent in adhesiveness when a cover member is adhered to a container in view of the above-mentioned problems of the prior art. is there.

[0009]

The above object is achieved by the invention described in each claim. That is, the characteristic configuration of the foamed container body of the present invention is a polyolefin foamed container body capable of directly sealing the lid member around the opening, wherein at least the sealed portion around the opening has a non-foamed layer, The surface roughness of the non-foamed layer is Ra ≦ 4 μm and the thickness is 5 μm or more.

[0010] According to this configuration, since the container material itself does not have a risk of eluting environmental hormones or the like, the container material can be used for food containers without any trouble, and the periphery of the opening of the container body and the lid member can be used. Can maintain good adhesion,
There is no problem in the sealing performance, and the periphery of the opening of the container body can be easily attached to the lid member, so that the yield can be increased. In this case, the area around the opening is
It is used as a concept that includes not only a flange-shaped portion formed so as to surround the opening but also a simple edge.

As a result, it was possible to provide a practically excellent container having excellent food safety, excellent adhesiveness, and high productivity. The surface roughness of the non-foamed layer is Ra> 4.
If it is μm, the adhesion between the periphery of the opening of the container body and the lid member cannot be maintained satisfactorily, and there is a possibility that the sealing property may be impaired. The thickness of the non-foamed layer is 5 μm.
If it is less than this, the surface roughness of the inner foamed layer cannot be covered, which is not preferable.

The C3-C4 hydrocarbon content of the foamed container according to the present invention is preferably at most 10,000 ppm, more preferably at most 1,000 ppm, particularly preferably at most 100 ppm.

According to this configuration, when this foamed container is used for a food container, it is possible to reliably eliminate the adverse effect on the human body, which is convenient. In addition, such a foamed container body,
For example, it can be achieved by using carbon dioxide as a foaming agent when foaming a polyolefin resin.

The foamed container according to the present invention preferably has a non-foamed layer of long-chain branched polypropylene on the outermost surface.

According to this configuration, since the outermost surface of the container body to which the lid member is bonded is not foamed, the surface roughness is reduced, the adhesiveness and the sealability are further improved, and the non-foaming property is improved. Since the foam layer is formed of long-chain branched polypropylene, the strength can be maintained high, and even when the gas reaches the surface during foaming of the foam layer constituting the inner layer, it is possible to reliably prevent the foam from being broken in the surface layer, Even when different types of layers are laminated in the manufacturing process, the surface roughness can be reduced, which is convenient.

Further, a characteristic configuration of the foam container of the present invention is that the foam container has the foam container of any one of claims 1 to 3 and a lid member capable of sealing an opening of the foam container.

According to this configuration, it is possible to provide a practically excellent foamed container which is excellent in food safety and adhesiveness and has high productivity.

In the present invention, the term "foamed layer" refers to a layer having an expansion ratio exceeding 1.5 times, preferably a layer having an expansion ratio of 2.5 to 4.0 times. Also, "non-foamed layer"
"Means a layer having an expansion ratio of 1.0 to 1.5 times, preferably 1.0 to 1.1 times.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. In the present embodiment, the polyolefin foam container shown in FIG.
A container 1 for food using a polypropylene resin having the shape shown in FIG. After the container body 1 stores contents such as food therein, a lid member 20 made of paper or the like is attached to the edge portion 2 which is a sealing portion formed around the opening of the container body. Used as a foam container.

The container of the present embodiment was manufactured by the method described below, and its physical properties were measured in order to compare with a comparative example. The following method was adopted as the measuring method.

(1) Surface Roughness The surface roughness of the container was measured by using a stylus-type roughness meter Surfcom570A manufactured by Tokyo Seimitsu Co., Ltd. First,
A sheet-shaped test piece of a predetermined shape is set, and a scan speed of 0.3 mm extends over an area of 1 cm from an arbitrary point in the test piece.
/ S measured the surface roughness (Ra). Surface roughness (Ra)
Is measured according to JIS B0601 center line average roughness (Ra)
The measurement was carried out according to the measurement method described above. This measurement was performed for three arbitrary points, and the average value was evaluated as Ra.

(2) Evaluation of Appearance The appearance of the foamed container was evaluated by visual observation, and those having high surface smoothness were evaluated as ○, and those having poor surface smoothness were evaluated as ×.

[0023]

EXAMPLE (Example) Thickness 1.8 mm, Foaming ratio 3.9
After heating the doubled expanded polypropylene sheet to a surface temperature of 150 ° C. using a far-infrared heater, the inner diameter is 150 mm and the depth is 39 mm as shown in FIG.
Was molded. The surface roughness was measured at three points on the edge 2 of the container 1. Average value Ra of three points on edge 2
Was 4.7 μm (measured value: 4.5 μm, 5.3)
μm, 4.2 μm).

The foamed polypropylene sheet used at this time is a multi-layer foamed polypropylene sheet having a non-foamed layer / foamed layer / non-foamed layer having two or three layers. The following resins were used for these foamed layers and non-foamed layers.

(1) Foamed layer Foamed layer constituent material: The polymer of the first stage has an intrinsic viscosity of 7.7.
A polypropylene polymer having an intrinsic viscosity of 1.9 dL / g was synthesized by dL / g, a continuous second stage polymerization, and 0.1 part by weight of calcium stearate was added to 100 parts by weight of the polymer powder. , Trade name Irganox 10
10 (manufactured by Ciba Specialty Chemicals) 0.
In addition, 05 parts by weight and 0.2 parts by weight of a trade name Sumilizer BHT (manufactured by Sumitomo Chemical Co., Ltd.) were added, mixed and melt-kneaded at 230 ° C. to obtain pellets having an MFR of 12 to obtain a foam layer constituent material.

(2) Non-foamed layer Polypropylene having a long chain branch, trade name PF814
(Montel: melting point 159.0 ° C, crystallization temperature 13)
0.1 ° C., MFR 2.2 g / 10 min). Using these resins, a foam sheet was produced by an extruder shown in FIG.

<Extrusion foaming test> 50 mmΦ twin screw extruder 3
And a 32 mmΦ single screw extruder 5 equipped with a 90 mmΦ circular die 7 was used. The raw material obtained by blending the propylene polymer used for the foamed layer with 1 PHR of a nucleating agent (Hydrocerol manufactured by Beilinger Ingelheim Chemicals Co., Ltd.) is charged into the hopper of the twin-screw extruder 3, and from the position where melting has proceeded. 1 PHR of carbon dioxide gas was injected at a high pressure, and the raw material and carbon dioxide gas were sufficiently kneaded and melted and sent to a die 7. The molten mixture to be a foamed layer and the molten resin to be a non-foamed layer fed by a single screw extruder 5 are extruded after lamination in a die, and cooled and blown up along a mandrel 9 installed immediately after. Thereafter, a slit was made in the cylindrical foamed sheet with a cutter 30, and the cylinder was opened to form a flat sheet 15, which was formed into two flat sheets by a roller 32 and was taken out by a take-up machine 11. In FIG. 2, reference numeral 6 denotes a supply pump for supplying carbon dioxide as a foaming agent. Also, a single-screw extruder and a twin-screw extruder are used, but the present invention is not limited to this, and another extruder may be used.

FIG. 3 shows a cross-sectional shape of a circular die suitable for carrying out the present invention, which is used in the manufacturing apparatus shown in FIG. The die used in this example is a circular die. The die 7 has resin flow paths 23a and 23b forming a foamed layer and resin flow paths 24, 24a, 24b, 24c and 24d forming a non-foamed layer.

The head 21 of the first extruder 3 is connected to the end of the die 7 in the direction of the resin flow path on the source flow side, and the head 22 of the second extruder 5 is connected to the end of the die 7 on the source flow side. Head 21
The molten resin that forms the foamed layer supplied from the above first enters the channel 23a and is sent toward the die exit. On the way, it is branched by passing through the path P and sent to the flow path 23b.

On the other hand, the molten resin forming the non-foamed layer is the second resin.
It is supplied from the head 22 of the extruder 5 and
a, 24b, and supplied so as to adhere to both surfaces of the flow path 23b so as to cover both surfaces of the foam layer, and are multi-layered at 25a. The molten resin supplied to the flow paths 24a and 24b passes through a divided flow path (not shown) similar to the path P so as to cover both surfaces of the foam layer of the flow path 23a.
4c and 24d, and are multi-layered at 25b.

The molten resin having a cylindrical shape having a three-layer structure at 25 a and 25 b is extruded from a die outlet 26.
By opening to the atmospheric pressure, the carbon dioxide gas in the resin constituting the foam layer expands, and bubbles are formed to form a foam layer.

(Comparative Example) Both the foamed layer and the non-foamed layer were made of polypropylene (melting point: 159.0 ° C, crystallization temperature: 130.1 ° C,
A container was molded in the same manner as in Example except that a foamed polypropylene sheet was obtained using MFR (2.2 g / 10 min).

The surface roughness of the three edge portions of this container was measured in the same manner as in the example. Average value R at three edges
a was 7.1 μm (measured values: 5.7 μm, 7.1)
μm, 8.6 μm).

Table 1 shows the evaluation results of the above Examples and Comparative Examples.

[0035]

[Table 1] As can be seen from Table 1, the container according to the present example had good smoothness of the external surface, whereas the container according to the comparative example had a poor external appearance. The texture of the container of this example when held by hand was extremely excellent.

[Other Embodiments] (1) In the above embodiment, an example was shown in which a multilayer foamed polypropylene sheet having a two-layered three-layer structure of a non-foamed layer / foamed layer / non-foamed layer was used. The invention is not limited to this, and may be a multi-layer, multi-layer foamed polypropylene sheet. For example, it may have a five-layer structure of a non-foamed layer / foamed layer / gas barrier resin layer / foamed layer / non-foamed layer, or a non-foamed layer / foamed layer / non-foamed layer / non-foamed layer / foamed layer / non-foamed layer It may have a six-layer structure of a foamed layer, and a gas barrier resin layer (preferably disposed on the inner surface side of the container body) in which a gas barrier resin layer is disposed on at least one surface.
It may have a seven-layer structure of a non-foamed layer / foamed layer / non-foamed layer / non-foamed layer / foamed layer / non-foamed layer. Further, a non-foamed layer / foamed layer / Non-foamed layer /
7 of gas barrier resin layer / non-foamed layer / foamed layer / non-foamed layer
It may have a layered structure. Here, the non-foamed layer may be a layer having a non-foamed structure, and may or may not have a gas barrier property in terms of function. Naturally, these multilayer foam sheets can be manufactured by a method similar to that described above.

(2) The gas barrier resin layer is not particularly limited, but specific examples include the following.

Saponified polyvinyl esters such as polyvinyl alcohol; saponified ethylene-vinyl ester copolymers such as ethylene-vinyl alcohol copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polyhydroxybenzoic acid Resin; nylon-6, nylon-
6,6-meta-xylenediamine-adipic acid condensation polymer,
Polymethylmethacrylimide, diethylenetriamine-
Polyamide resins such as adipic acid copolymers and salts thereof;
Aramid resins; acrylic resins such as polymethyl methacrylate, polyacrylic acid, sodium polyacrylate, poly-2-hydroxyethyl acrylate, poly-2-hydroxyethyl methacrylate, polyacrylamide, ethylene-acrylic acid copolymers and salts thereof Resins; halogen-containing resins such as polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, and polytetrafluoroethylene; polycarbonate resins, polysulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene ether resins, polyphenylene oxide resins, Engineering plastic resins such as polyarylene sulfide resin, polymethylene oxide resin, and polyacetal resin. Further, a so-called modified resin obtained by graft-modifying, cross-linking or modifying the molecular chain terminal of these resins can also be used.

(3) A non-stretched non-foamed thermoplastic resin layer, for example, a non-stretched non-foamed polypropylene layer (so-called CPP)
Layer) is disposed as the innermost layer of the container, and the layer constitutes a non-foamed layer at least in the sealed portion around the entrance opening, which is also a preferred embodiment of the present invention. Specifically, for example, a layer configuration of a non-stretched non-foamed polypropylene layer / adhesive resin layer / gas barrier resin layer / adhesive resin layer / non-foam layer / foam layer / non-foam layer in order from the inner surface side of the container body A container body having a layer structure of a non-stretched non-foamed polypropylene layer / adhesive resin layer / gas barrier resin layer / adhesive resin layer / non-stretched non-foamed polypropylene layer / non-foamed layer / foamed layer / non-foamed layer; Non-stretched non-foamed polypropylene layer /
Container body with a layer structure of adhesive resin layer / gas barrier resin layer / adhesive resin layer / non-foam layer / foam layer / non-foam layer / non-foam layer / foam layer / non-foam layer / unstretched non-foam polypropylene layer / Adhesive resin layer / gas barrier resin layer / adhesive resin layer / unstretched non-foamed polypropylene layer / non-foamed layer / foamed layer /
A container having a layer structure of non-foaming layer / non-foaming layer / foaming layer / non-foaming layer is preferable.

Further, the non-stretched non-foamed thermoplastic resin layer may be disposed in the middle of the laminated structure of the container. Specifically, for example, in order from the inner surface side of the container body, a non-foamed layer / foamed layer / non-foamed layer / unstretched non-foamed polypropylene layer / adhesive resin layer / gas barrier resin layer / adhesive resin layer / non-foamed Layer / foamed layer / non-foamed layer, or non-foamed layer / foamed layer / non-foamed layer / unstretched non-foamed polypropylene layer / adhesive resin layer / gas barrier resin layer / adhesive resin layer /
A container having a layer structure of a non-stretched non-foamed polypropylene layer / non-foamed layer / foamed layer / non-foamed layer is preferable.

These container bodies can be manufactured by preparing a laminated sheet having a layer structure corresponding to the container body by a method similar to the above, and forming the laminated sheet into a desired container shape by vacuum molding or the like.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a foam container of the present invention.

FIG. 2 is a schematic configuration diagram of a foam sheet manufacturing apparatus for manufacturing the foam container body of the present invention.

FIG. 3 is a sectional view of a circular die which is a main part of the manufacturing apparatus of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Foam container 2 Sealing part 20 Lid member

Claims (4)

[Claims] 1. A polyolefin foam container capable of sealing a lid member directly around an opening, wherein at least the sealing portion around the opening has a non-foamed layer, and the surface roughness of the non-foamed layer is Is Ra ≦ 4 μm and the thickness is 5
A foam container having a thickness of at least μm. 2. The hydrocarbon content of C3 to C4 is 100.
The foamed container according to claim 1, wherein the content is not more than 00 ppm. 3. The foamed container according to claim 1, which has a non-foamed layer of long-chain branched polypropylene on the outermost surface. 4. A foam container comprising: the foam container according to claim 1; and a lid member capable of sealing an opening of the foam container.