JP2000190939A - Expanded polypropylene laminated container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold an expanded polypropylene laminated container from a laminated body wherein an expanded polypropylene resin layer is provided as a barrier to prevent impurities such as additives or unreacted substances from being eluted from an expanded polystyrene wall layer. SOLUTION: An expanded polypropylene sheet material 2 having heat resistance and oil resistance is superposed on an expanded polystyrene sheet material 4 having high heat insulating properties to form a composite expanded sheet material, which material is set in a container forming device so that the expanded polypropylene sheet of the composite sheet material forms an inside layer and is then pressed into a food container to prevent residual substances such as dimer or trimer from being eluted from the expanded polystyrene layer into foods by using a layer 2, as a barrier, which serves as an innermost layer of high safety.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the molding of a heat-insulating and heat-resistant food container made of expanded polystyrene resin, and more particularly to the dissolution of impurities such as additives and unreacted substances from a foamed polystyrene wall layer. The present invention relates to the molding of a foamed polypropylene laminated container comprising a laminate provided with a foamed polypropylene resin layer as a barrier layer for preventing the occurrence of cracks.

[0002]

2. Description of the Related Art Conventionally, various types of styrofoam containers formed by foaming polystyrene have been well known as heat insulating containers. These containers have been widely used because they are lightweight and have excellent heat insulating properties. Was. by the way,
In recent years, along with changes in lifestyle and eating habits, the spread of instant foods such as coffee and instant noodles at home, and cooked or semi-cooked at food departments such as department stores and supermarkets As various foods are sold, and the food service industry such as fast food restaurants floods, consumers can safely hold hot and cold foods and drinks, and so on. Inexpensive and lightweight expanded polystyrene has come to be used in large quantities as a disposable container for storing food.

[0003] It is widely known that polystyrene resins used for molding the above-mentioned disposable food containers are generally produced by polymerizing styrene monomers by a solution polymerization method or a suspension polymerization method. There are various isomers in the styrene monomer obtained, and these raw material styrene monomers do not always completely polymerize to form a polymer, and some of them may be in the form of dimer or trimer. Some styrene dimers and styrene trimers have remained in the polymer, albeit slightly, but these are easily changed by light or peroxide, and some people are concerned that they are harmful to living organisms. .

A commercially available container containing the above-described food is molded using the polystyrene resin produced as described above. The general molding method is as follows. Such a molding method is used. A raw material obtained by adding an appropriate foaming agent and an antioxidant to an unfoamed polystyrene resin is mixed and pressed into a molding die having a predetermined container shape, heated and foamed, and molded into a predetermined shape. Alternatively, after extruding into a sheet and forming it into a foamed sheet, the foamed sheet is heat-softened in a pressure forming apparatus and then formed into a predetermined shape by pressure forming or other pressure forming means. And integrally forming the foam container 8 as shown in FIG. (JP-A-57-17
No. 12, JP-A-57-131528, etc.)

Further, as shown in FIG. 5, a polystyrene resin 9c obtained by adding a foaming agent and an antioxidant to a sheet material 9a serving as a base material of paper or other containers and forming an adhesive layer 9b on one surface thereof and mixing them. Are laminated and formed into a sheet-like foamable polystyrene laminate, and the sheet-like polystyrene laminate is cut into a desired shape of a container, and then molded into a predetermined shape by a container molding device. Then, a method of forming the container 9 by heating and foaming is used.
(Japanese Patent Publication Nos. 56-47056 and 57-21467,
No. 58-44475, etc.)

[0006] In the foamed polyethylene container molded by the above method, ice cream, coffee,
Alternatively, instant noodles, cooked foods, and many other foods are stored and are widely marketed widely, but recently, social problems have arisen in that the styrene monomer remaining in the styrene polymer Dimer or 3
Styrene dimer or styrene trimer composed of a monomer, or nonylphenol used as an antioxidant. If these dimers, nonylphenols, etc. are taken into the human body, they may become harmful substances in the human body, or if they flow into the natural world such as rivers and seawater, they may cause abnormalities in organisms such as fish and shellfish. Concerns have been raised that it may be a causative substance.

Considering the case where a person eats food in a container made of expanded polystyrene, soft drinks such as water and juice, yogurt, ice cream,
When eating at low temperatures such as salads, even if there are residual substances such as dimers and trimers in the expanded polystyrene layer of the container, there is no danger that these will elute from the container, but the food will remain in the container for a long period of time. Or put in
You may be concerned that eating a large number in a short period of time will cause some harm to your body, but if you eat common sense amounts within the normal net expiration date, You don't need to worry about it.

However, when a high-temperature liquid such as coffee, soup, or instant noodles is poured into a container and eaten, or when frozen foods or cooked foods are eaten by heating the whole container with a microwave oven, etc. Although it is not a long time, the container is exposed to high temperature, and the dimer or trimer in the expanded polystyrene layer moves violently and it becomes very easy to elute, so the dimer etc in the polystyrene layer easily into the food solution Would not be expected to be eluting at all. Therefore, in the case of eating food after putting the food in a container and exposing it to a high-temperature state, it is thought that impurities such as dimers in the expanded polystyrene may be dissolved and introduced into the human body. Must prevent these substances from being eluted into the food,
It is necessary to remove anxiety.

[0009]

SUMMARY OF THE INVENTION A food container having excellent heat resistance, oil resistance and heat insulation properties is formed using a composite sheet material in which expanded polypropylene is laminated on expanded polystyrene, and unpolymerized resin remaining in the expanded polystyrene. An object of the present invention is to provide a safe food container provided with a shielding layer for preventing a substance such as a dimer, a trimer or an additive substance from being dissolved in a food.

[0010]

According to the present invention, a heat-resistant and oil-resistant foamed polypropylene sheet molded using a polypropylene resin is laminated on a heat-insulating foamed polystyrene sheet molded using a polystyrene resin. A dimer remaining in the expanded polystyrene layer is formed by molding a composite foamed sheet material, press-molding the composite sheet material with a container molding apparatus so that the expanded polypropylene sheet becomes an inner layer, and forming the composite sheet material into a food container. A foamed polypropylene layer is formed by providing a foamed polypropylene layer that blocks the dissolution of impurities such as trimmers and trimmers and other substances harmful to the human body into food.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a polystyrene resin and a polypropylene resin mixed and adjusted with a foaming agent are supplied to a co-extrusion molding machine, respectively, and extruded into a sheet shape through a T-die to form a foamed polystyrene sheet 4 and a foamed foam. The polypropylene sheet 2 is laminated and foamed into a composite foamed sheet material 5.

Subsequently, the composite foamed sheet material 5 thus formed is cut into a predetermined size and supplied to a container forming apparatus 7, which is heated and softened to an appropriate moldable temperature. Foamed polypropylene layer 2 on the surface inside the container
After setting the sheet material in the molding dies 7a and 7b so as to position the container, pressure molding is performed so that the outer shape of the container becomes a cup-shaped container.
Then, the container 1 whose inner wall is constituted by the foamed polypropylene layer 2 is formed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention of the present application will be described below with reference to the drawings based on one optimal embodiment. As shown in FIG. 1, the composite foamed polypropylene laminated container 1 of the present invention suitable for packaging food is formed in a cup shape, and the wall structure is formed by a foamed polypropylene layer 2. It has a structure in which an outer wall composed of a foamed polystyrene layer 4 is laminated on an inner side wall with an intermediate adhesive layer 3 interposed therebetween, and dimers and other impurities are eluted from the foamed polystyrene layer 4 into the container. Polypropylene layer 2
Has a structure to shut off.

In order to actually form a foamed polypropylene laminated container having the above structure, first, an endothermic decomposition type chemical foaming agent (master batch type) is added to a dried polystyrene resin pellet in an amount of 0.5 to 2.0% by weight. And
While mixing and preparing the expanded polystyrene raw material,
An endothermic decomposition type chemical foaming agent (master batch type) is added to the dried polypropylene resin pellets in an amount of 0.5 to 3.0% by weight, and the mixture is adjusted to prepare a foamed polypropylene raw material.

The raw resin thus adjusted is supplied to a co-extrusion molding machine, melted and kneaded, and then foamed into a sheet by co-extrusion through a T-type die (coat hanger type). An adhesive layer is extruded between a polystyrene sheet and a foamed polypropylene sheet and laminated, or a foamed polystyrene sheet and a foamed polypropylene sheet are separately extruded and foamed to form an adhesive between the foamed polystyrene sheet and the foamed polypropylene sheet. To form a composite foamed sheet material 5.

As shown in FIG. 3, the above-mentioned composite foamed sheet material 5 is supplied to a container forming apparatus 7 provided with pressure forming and other forming means, and is formed into a predetermined form which can be formed by infrared or other heating means. After being heated to the temperature, the foamed polypropylene layer 4 is transferred to a molding die and set so that the foamed polypropylene layer 4 is located inside the container, and the end of the sheet material 5 is appropriately held by a well-known clamp mechanism 6. The sheet material is pressed and deformed into a female mold by a male mold to form a container 1 having a predetermined shape.

Since the foamed polystyrene container of the present invention thus formed has a foamed polypropylene layer on the inner side wall in which food is stored, hot water is poured into the container, or the container is heated by a microwave oven or the like. Even so, the polypropylene layer 2 blocks elution of impurities such as dimers in the polystyrene layer, which are considered to adversely affect the human body, into the container.

Example 1 (A) Preparation of Resin Raw Material for Expanded Polystyrene A polystyrene resin pellet (GPPS, manufactured by Mitsubishi Chemical Corporation) dried to a predetermined moisture content was subjected to an endothermic decomposition type foaming agent (manufactured by Boehringer: 1.0 wt% of CF40S (master batch type), and the mixture is mixed and adjusted by a well-known stirring and mixing device such as a tumbler. (Note) CF40S: granulated by mixing 60% polystyrene resin with 40% foaming component based on sodium bicarbonate and citric acid. (B) Adjustment of resin raw material for foamed polypropylene To a polypropylene resin pellet (B761QD manufactured by Mitsui Petrochemical Co., Ltd.) dried to a predetermined moisture content, an endothermic foaming agent (CF20E master batch type manufactured by Boehringer) was added to 1.0. % By weight and mixed and adjusted by a well-known stirring and mixing device such as a tumbler. (Note) CF
20E: 20% foaming component based on sodium bicarbonate and citric acid mixed with 80% low density polyethylene resin and granulated.

(C) Forming of Foam Sheet The foam sheet was extruded and foamed by a co-extrusion molding apparatus as described below. Using an extruder having a screw diameter of 90 mm, the raw material (A) was melted and kneaded, and then extruded through a T-die having a width of 800 mm and foamed to form a foamed polystyrene sheet. (The extrusion conditions at this time are: cylinder temperature of 160
~ 200 ° C and the die temperature was maintained at 160-200 ° C. ) Using an extruder with a screw diameter of 65 mm, the above raw material (B)
Was melted and kneaded, and then extruded through a T-die having a width of 800 mm and foamed to form a foamed polystyrene sheet.
(The extrusion conditions at this time are as follows.
° C, and the die temperature was maintained at 170-200 ° C. )

The raw material resin adjusted as described above is supplied to a raw material supply hopper of each extruder of the co-extrusion molding apparatus, melted and kneaded, then co-extruded through a T-type die and foamed into a sheet. Simultaneously with the molding, as shown in FIG. 2, the adhesive layer 3 is extruded between the expanded polystyrene sheet 4 and the expanded polypropylene sheet 2 and laminated to form a composite foam sheet material 5.

As shown in FIG. 3, the composite foamed sheet material 5 formed as described above is cut into an appropriate size and supplied to the container forming apparatus 7, where it is heated by a heating unit composed of far infrared rays. After being heated to a moldable predetermined temperature, it is transferred to a pressure molding section and set in a molding die so that the expanded polypropylene layer 2 is located inside the container. After holding the end, the sheet material is pressed and deformed into the female mold 7b by the male mold 7a to form a cup-shaped predetermined container.

Then, the container 1 thus formed is
It is used to store and pack food inside, or to be used immediately after putting food in it. It is common to cook after cooking. Then, the case where the hot water is put in the container of the present invention described above and left standing for 10 minutes with stirring, and the case where the food is put in the container and heated with a microwave oven, the dimer and nonylphenol such as dimer are put in the container. An examination was made to determine whether or not the impurity was eluted, but no impurity was detected in the container, which was considered to be present in the expanded polystyrene layer.

Example 2 1.5% by weight of an endothermic foaming agent (CF40S, Boehringer Co.) was added to dried polystyrene resin pellets (GPPS, manufactured by Mitsubishi Chemical Corporation), and the mixture was stirred and mixed. Adjust the resin raw material. Dried polypropylene resin pellets (Mitsui Petrochemical Co .: B
76QD) and an endothermic foaming agent (Boehringer: C
F20E) is added in an amount of 1.5% by weight, and mixed and stirred to prepare a foamed polypropylene resin raw material.

The raw material resin adjusted as described above is supplied to the raw material supply hopper of the extruder of the co-extrusion molding device, melted and kneaded, and extruded into a sheet shape through a T-die as in Example 1. At the same time as foam molding, an adhesive layer is extruded and laminated between the foamed polystyrene sheet layer and the foamed polypropylene sheet layer to form a composite foamed sheet material.

The composite foamed sheet material thus formed is supplied to a pressure molding device and heated to a predetermined temperature at which it can be molded by far-infrared rays in the same manner as in Example 1. Then, the sheet material was set in a forming die so as to be inside, and the end of the sheet material was clamped. Then, the sheet material was pressed and deformed into a female mold by a male mold to form a tray-shaped deep dish container. .

In the same manner as in Example 1, the tray-shaped container in which boiling water was placed in the container and the food in which the food was placed in the container were heated with a microwave oven, and there were concerns about dimer, nonylphenol, and the like. An examination was made to determine whether or not any impurities were eluted, but no elution of impurities in the expanded polystyrene layer was detected in the container.

From this, the present invention constitutes a foamed polystyrene laminated container in which the outer wall of the container is formed of a foamed polystyrene layer, and the inner wall of the container is formed of a foamed polypropylene layer via an adhesive layer. This indicates that the polypropylene layer can block elution into the container even when the container is placed in a heated state and impurities in the expanded polystyrene layer are easily eluted.

In addition, as for the foamed polystyrene resin raw material and the foamed polypropylene resin raw material used in the present invention, the extrusion molding test was conducted by changing the mixing ratio of the resin pellet and the foaming agent in various ways. I got it. (A) For polystyrene resin pellets, use a
5 to 2.0% by weight (b) For polypropylene resin pellets, a resin material prepared by adding 0.5 to 3.0% by weight of a foaming agent is used to prepare a foamed sheet laminate having predetermined closed cells. Coextrusion molding or laminate molding is sufficiently possible.

Further, a composite sheet material having various laminated structures is formed using a foamed polystyrene (PS) sheet and a foamed polypropylene (PP) sheet which are extruded and foamed using the raw material resin prepared as described above, and When a container was molded using the composite sheet material and tested, it was found that a laminated structure having the following combination could be used. Furthermore, depending on the contents to be stored, ethylene vinyl alcohol (EVOH)
When packaging is performed using a container formed from a composite sheet material provided with layers and laminated, the permeation of oxygen is suppressed, and thus the container is suitable for long-term storage. (Outside) foamed PS layer / adhesive layer / foamed PP layer (inside) (outside) foamed PP layer / adhesive layer / foamed PS layer / adhesive layer / foamed PP layer (inside) (outside) foamed PS layer / adhesive layer / foamed PP layer / non-foamed PP
Layer (inside) (outside) Foamed PS layer / adhesive layer / EVOH layer / adhesive layer / foamed PP layer (inside)

As described above, according to the invention of the present application, it is feared that lamination of heat-insulating expanded polystyrene and heat-resistant expanded polypropylene may cause harm in the expanded polystyrene acting as an environmental hormone. Can be blocked by a foamed polypropylene layer so that the impurities do not elute into the container. Further, by providing a non-foamed polypropylene layer or an ethylene vinyl alcohol layer in addition to the foamed polystyrene layer and the foamed polypropylene layer, the strength can be increased and the permeation of oxygen can be blocked. Further, for the intermediate layer laminated between the inner layer and the outer layer, a sheet material made of recycled polystyrene resin or polypropylene resin can be used.

[0030]

The foamed polystyrene composite sheet material for forming the container of the present invention is formed by laminating foamed polystyrene and foamed polypropylene foamed with an endothermic foaming agent, and is therefore composed of a foamed sheet having closed cells. Further, since the container molded using the composite sheet material is configured such that the expanded polypropylene layer serves as the inner wall of the container, even if the container is placed in a heated state, impurities in the expanded polystyrene layer can be reduced. The diffusion is blocked by the foamed polypropylene layer, and there is no risk that the impurities that may be harmful to the human body may dissolve into the container, so that the consumer is not unnecessarily anxious.

Further, since the container of the present invention is molded from a laminate in which a foamed polystyrene layer is provided with a foamed polypropylene layer having oil resistance and heat resistance, the container has a higher oil resistance and a lower resistance than a container composed of a foamed polystyrene single layer. Heat resistance can be improved, and heat insulation can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a laminated container provided with a foamed polypropylene layer of the present invention.

FIG. 2 is a sheet material for forming the foamed polypropylene laminated container of the present invention.

FIG. 3 is a view showing a forming process of the laminated container of the present invention;
(A) is each sectional view which shows just before shaping | molding, (b) is each sectional drawing which shows just after shaping | molding.

FIG. 4 is a cross-sectional view showing a conventional general foamed polystyrene container.

FIG. 5 is a sectional view showing a conventional foamed polystyrene laminated container.

[Explanation of symbols]

 1. 1. Laminated container of the present invention 2. Foamed polypropylene layer Intermediate adhesive layer 4. 4. Expanded polystyrene layer 5. A laminated sheet material for forming the laminated container of the present invention. Clamp 7. Pressure molding device 7a. Upper mold 7b. Lower mold 8. 8. Expanded polystyrene container Expanded polystyrene laminated container

Continued on the front page (72) Inventor Tomoyuki Ishihara 310 Minorudai, Matsudo-shi, Chiba F-term in Yoshino Kogyosho Chiba Plant (reference) 3E033 AA08 AA10 BA16 BA22 BB04 BB08 CA07 CA08 CA09 FA02 GA02 4F204 AA11 AA13 AA19 AG03 FA01 FB01 FB22 FF01 FG04 FG08

Claims (6)

[Claims] 1. A food container comprising a foamed resin in which a foamed polystyrene layer excellent in heat insulation and a foamed polypropylene layer rich in heat resistance are laminated, wherein the foamed polypropylene layer is laminated inside the foamed polystyrene layer. A foamed polypropylene laminated container comprising a wall. 2. The food container according to claim 1, wherein a non-foamed polypropylene layer is further laminated on an inner surface of the foamed polypropylene layer forming an inner layer to form a container wall. Foamed polypropylene laminated container. 3. The foam according to claim 1, wherein the food container has a container wall formed by further laminating a foamed polypropylene layer on an outer surface of the foamed polystyrene layer forming an outer layer. Polypropylene laminated container. 4. The food container is characterized in that a container wall is formed by laminating an intermediate layer made of ethylene vinyl alcohol resin between an inner layer of expanded polypropylene layer and an outer layer of expanded polystyrene layer. The foamed polypropylene laminated container according to claim 1. 5. The foamed polypropylene laminated container according to claim 1, wherein the food container is formed in a cup shape. 6. The foamed polypropylene laminated container according to claim 1, wherein the food container is formed in a tray shape.