JPS63191843A - Stock sheet of packaging material - Google Patents

Abstract

PURPOSE:To form a stock sheet of packaging materials, having a large expansion ratio and nonoriented open cells and being good in strength, hygroscopicity, water permeability and air permeability, by mixing a thermoplastic synthetic resin such as polystyrene with a kaolin clay mineral and kneading, with heating, the mixture together with, optionally, a blowing agent and forming the mixture into a sheet. CONSTITUTION:A thermoplastic synthetic resin such as polystyrene is mixed with 5-50wt.% kaolin clay mineral of a particle diameter of 2-8mu, and this mixture as such or together with a suitable blowing agent is kneaded with heating, and molded into a sheet. Examples of said blowing agents include flon gases, pentane and LP gases.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a foamed plastic fabric that has excellent properties mainly as a packaging material. Appropriate heat-pressing can achieve exceptional results especially in the transportation and long-term preservation of fruits and fresh vegetables (hereinafter referred to as "fruits and vegetables").

[Conventional technology and its problems]

Generally, the fruits and vegetables mentioned above generate ethylene gas from themselves during transportation or storage, so if this is not removed,
It is known that ripening progresses quickly and the freshness rapidly decreases.

On the other hand, when transporting and storing these fruits and vegetables, it is common to use cold storage as a means to maintain freshness, but in this case, fruits and vegetables that are taken out of the refrigerator and repacked in other packaging materials, Since dew condensation occurs on the surface, the packaging material is required to have sufficiently high water absorption or hygroscopicity in addition to the above-mentioned ethylene gas removal function.

Conventionally, waste paper, cardboard, etc., as well as closed-cell foamed plastic sheets or molded materials thereof, have been widely used as packaging materials for fruits and vegetables of this kind, mainly for the purpose of cushioning the fruit and vegetables.

However, the former has good water absorption but lacks breathability.
The surface becomes wet, the humidity inside the storage compartment becomes high, and stuffiness is likely to occur, and the cost is high.Also, the latter has no water absorption or hygroscopicity, and due to the above-mentioned reasons, it may cause a decrease in the freshness of fruits and vegetables. The problem was found to be that it accelerated corruption.

[Means for solving problems]

In view of these circumstances, the present inventors have diligently conducted experiments and research, and have found that when kaolin clay minerals, such as sericite, are heated under certain conditions, their own adsorbed water or It was discovered that adding water causes significant volumetric expansion, and focusing on this point, the material was used as an expandable filler for thermoplastic synthetic resins such as polystyrene.
~50% (weight ratio = below), and either by heating and kneading as it is, or by forming it into a sheet using a blowing agent such as liquefied gas, such as chlorofluorocarbon gas, pentane, or LP gas. We succeeded in obtaining a raw material sufficient to satisfy the above-mentioned conditions required for packaging materials.

[For production]

During the heating and kneading process, the original fabric of the present invention has a foaming rate that is approximately twice as high as that of a foamed sheet using a conventional foaming agent alone, and at the same time, the molecules form a substantially spherical shape. and each of those bubbles communicates with each other,
It becomes a non-oriented open-cell sheet, which has extremely good properties in terms of strength, water absorption or water permeability, and air permeability.

〔Example〕

Hereinafter, the structure of the present invention will be explained in more detail according to first and second embodiments.

(First example) Polystyrene (pellets) 87% by weight, particle size 2-5
10% micron sericite and 5% water are put into a normal screw type extruder, mixed and pressurized in a cylinder with a hot atmosphere of around 160℃, and injected from the nozzle.
．． 0CII X 34. A sheet-like original fabric having a thickness of 1.0 cm and a thickness of 1.0 cm was obtained.

In this case, in order to make the mixing state of the art materials uniform, it is preferable to minimize the difference in apparent specific gravity between the two materials, and it is optional to add an appropriate amount of pigment as necessary.

On the other hand, the present inventors prepared an original fabric of the same size as the sheet-like original fabric of the present invention described above by mixing a small amount of talc into polystyrene according to the conventional manufacturing method and using an appropriate liquefied gas as a blowing agent. When compared with the obtained one, it was found that the foaming ratio of the polystyrene in the original fabric of the present invention was 35 times,
It was only 20 times that of the comparative example.

In addition, in order to compare the preservation performance of the fruit "kiwi" using the above two original fabrics as raw materials, each of the above original fabrics was heated appropriately, and a number of sections (a) in which kiwi was shaped on the side thereof were prepared. ] Mouth
(c) Molding a packaging material 1 in which concave areas are formed close to each other, and each section (a), (b), (c), and
Kiwis 2 that had been stored in a cold storage for 10 hours were stored in one container, and the upper surface of each container was covered and sealed with a same material material 3. As for the storage state of the above-mentioned kiwis after a week had passed since they were stored in this way, there was almost no deterioration in freshness using the packaging material of the present invention, but in the case of the comparative example, especially the portions that were in contact with packaging material 1. It was confirmed that the epidermis had softened and rot had penetrated into the interior.

(Second Example) Polystyrene (pellets) 90% by weight, particle size 5-8
Using CFC gas as a foaming agent, 10% micron sericite was heated, kneaded, and extruded using the same screw type extruder as in the previous example. Ocm, thickness 1. O
A sheet-like original fabric of mm was obtained.

The expansion ratio of polystyrene in this case was 40 times.

Then, when a packaging material with the same specifications as above was formed using this original fabric and the storage condition of the kiwi fruit was observed, good results were obtained, which seemed to be better than the previous example.

In addition, in the present invention, the particle size of sericite, etc. is set to 2 to 8 microns in consideration of miscibility with the main synthetic resin, and the addition amount is set to 5 to 50%. This is because when the content is less than 5%, the foaming properties and water absorption properties are insufficient, and even when the content is more than 50%, no significant improvement effect was observed.

〔Effect of the invention〕

The original fabric of the packaging material according to the present invention has good pressurization properties and does not lose its shape even when absorbed by water or moisture, so it has a high cushioning effect. Because it does not peel between layers and has sufficient burst resistance,
Compared to conventional packaging materials, it can significantly reduce damage during transportation and storage, especially for soft fruits and vegetables.

In addition, each of the bubbles in the original fabric has a so-called open cell property in which they communicate with each other at their contact points, but the entire cell retains relatively rigidity and has excellent shape retention, and has excellent water permeability and moisture absorption. In addition, it has good air permeability, and can be expected to have a sufficient effect of removing ethylene gas, etc., which can reduce the freshness of fruits and vegetables, and has excellent properties as a variety of packaging materials.

Furthermore, the raw fabric of the present invention has a lower manufacturing cost than conventional foamed raw fabrics of this type, and is not only suitable as a packaging material for upper fruits and vegetables, but also can be used for other packaging materials by utilizing its characteristics. It can be expected to have a wide range of uses, not only as a material, but also as a building material or construction material.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of the packaging material of the present invention, showing a state in which fruits and vegetables are stored. In addition, in the figure, 1... packaging material, 2... kiwi, 3... original fabric. Patent applicant Dowa Koei Co., Ltd. Agent Patent attorney Kazuo Ohara 1...Packaging material 2...Kiwi 3...Original fabric

Claims (1)

[Claims] 1. Particle size 2 for thermoplastic synthetic resins such as polystyrene
A packaging material containing 5 to 50% (weight ratio) of kaolene-based clay minerals of ~8 microns, heated and kneaded as is or in combination with an appropriate foaming agent, and formed into a sheet. original fabric.