JPH0414195Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a heat-resistant container formed from a composite foamed plastic sheet consisting of a polystyrene foam sheet and a polypropylene foam sheet. [Prior Art] Conventionally, foamed plastic sheet containers made of a laminate of a rigid or semi-rigid foamed polystyrene sheet and a soft foamed polyethylene sheet are known (Japanese Utility Model Publication No. 48121/1983). However, such containers made of composite foamed plastic sheets have been unsatisfactory, having the drawbacks of poor heat resistance and moldability, as well as poor heat resistance and compression resistance at high temperatures. [Objective] The object of the present invention is to provide a heat-resistant container formed from a composite foamed plastic sheet that overcomes the above-mentioned drawbacks. [Configuration] According to the present invention, polystyrene foam sheet a
has a structure in which a polypropylene foam sheet b is laminated on at least one surface of the polypropylene foam sheet b, and in the relationship between the thickness B of the polypropylene foam sheet b and the thickness A of the polystyrene foam sheet a, 1 (mm) A heat-resistant container is provided which is formed by thermoforming a composite foamed plastic sheet where ≦A+B≦30 (mm) and 0.01≦B/A≦10. The heat-resistant container of the present invention will be explained with reference to the drawings. In FIGS. 3 and 4, 1 is a heat-resistant container, 2 is an adhesive, a is a polystyrene foam sheet, and b is a polypropylene foam sheet. That is, as shown in FIGS. 3 and 4, the heat-resistant container 1 of the present invention is a composite foam sheet in which a polystyrene foam sheet a and a polypropylene foam sheet b are laminated with an adhesive 2, which is formed into a desired shape by thermoforming. It is molded into. In this case, thermoforming methods include vacuum forming, in which the composite foamed plastic is heated and softened and pressed against a desired mold, and the air in the gap between the mold and the material is removed, and the material is brought into close contact with the mold under atmospheric pressure; Compressed air molding using compressed air at atmospheric pressure or higher or vacuum can be used. Note that although FIGS. 3 and 4 show a composite foam sheet in which a polypropylene foam sheet b is laminated on one side of a polystyrene foam sheet a as a raw material, the present invention is not limited to the following. The material is not limited to these materials, and a composite foamed plastic sheet such as that shown in FIG. 2, which is a polystyrene foamed sheet a and a polypropylene foamed sheet b laminated on both sides thereof, may be used as the raw material. Next, the composite foamed plastic sheet used for manufacturing the heat-resistant container of the present invention will be explained with reference to the drawings. In the drawings, a shows a polystyrene foam sheet and b shows a polypropylene foam sheet. Figure 1 shows an example in which a polypropylene foam sheet is laminated on one side of a polystyrene foam sheet, and Figure 2 shows an example of a polystyrene foam sheet laminated on one side. An example is shown in which polypropylene foam sheets are laminated on both sides. Polystyrene foam sheet a used in this invention
is polystyrene, polyα-methylstyrene, polyP-methylstyrene, styrene-butadiene copolymer, styrene-acrylonitrile copolymer,
Styrene-butadiene-acrylonitrile copolymer, styrene-acrylic acid copolymer, styrene-
A styrenic resin such as a maleic anhydride copolymer, a styrene-ethylene copolymer, or a mixture of two or more of these is foamed to a foaming ratio of 5 to 60.
2 times, preferably 10 to 40 times. In this case, the thickness of the polystyrene foam sheet is about 0.7 to 25 mm, preferably about 1.0 to 20 mm,
Closed cell foams are preferably used. Polypropylene foam sheet b, in addition to propylene homopolymers, propylene resins such as ethylene and propylene block copolymers, propylene and other olefin copolymers, or propylene resins blended with other polyolefin resins The material is used as a raw material, and it is foamed to increase the foaming ratio.
It is 20 to 120 times larger, preferably 30 to 100 times larger. In this case, as a propylene resin,
When using a propylene copolymer, the propylene content is at least 80 mol% or more, and other polyolefins such as polyethylene, ethylene-vinyl acetate copolymer, polybutene-1, etc. are blended with the propylene resin. If the proportion of propylene resin in the formulation is 60% by weight or more,
Preferably it is 75 to 95% by weight. The thickness of the polypropylene foam sheet is 0.3 to 5 mm, preferably 0.5 mm.
~3mm. To preferably produce the polypropylene foam sheet used in the present invention, an extruder is used to knead a volatile blowing agent into the melt of the propylene resin raw material under pressure, followed by extrusion foaming. In this case, examples of volatile blowing agents include Freon-11 (trichloromonofluoromethane), Freon-21 (dichloromonofluoromethane), Freon-113 (trichlorotrifluoroethane), n-pentane, n-hexane, Isohexane, n-heptane, isooctane, etc. are preferably used. The resin temperature during extrusion molding is usually set at 160°C or lower. In addition, 0.005 to 80% by weight of talc, calcium carbonate, calcium sulfite, silica, diatomaceous earth, etc. can be added to the propylene resin raw material as a cell nucleating agent or filler, if necessary.
Coloring agents, antioxidants, antistatic agents, etc. can also be blended. The composite foam plastic sheet used in the present invention has a total thickness of 1.0 to 30 mm, preferably 1.5 to 23 mm. If the thickness of the entire sheet is smaller than the above range, the heat insulation properties and shape retention properties will be poor, while if it is larger than the above range, problems such as deterioration of secondary formability such as heat processing will occur, which is not preferable. Further, in the present invention, the thickness ratio B/A of the polypropylene foam sheet b and the polystyrene foam sheet a is 0.01 to 10, preferably 0.025 to 3.
stipulated within the range of If the thickness ratio B/A of the foamed sheet is smaller than this range, the composite foamed plastic sheet will have poor heat resistance, poor thermoformability, and poor heat insulation and compression properties at high temperatures. On the other hand, if it exceeds the above range, it is not preferable because it causes problems such as poor secondary formability such as heat processing. In addition, when a plurality of layers of polypropylene foam sheet b and polystyrene foam sheet a are present in the composite plastic sheet, the above-mentioned thickness B or A shall be the sum of the respective thicknesses. The polystyrene foam sheet a and the polypropylene foam sheet b can be joined using an adhesive. In this case, as the adhesive, for example, in addition to ethylene-vinyl acetate copolymer resin, various conventional adhesives are used, including water-soluble adhesives based on acrylic-nitrile copolymer resin. It is preferable to use In addition, the joining of polystyrene foam sheet and polypropylene foam sheet,
It can also be carried out using a molten resin such as an ethylene-vinyl acetate copolymer resin or a mixture of polystyrene and polypropylene. [Effects] The heat-resistant container made by thermoforming the composite foamed plastic sheet of the present invention has overall higher heat resistance than the container obtained from the conventional composite foamed sheet made of a polyethylene foamed sheet and a polystyrene foamed sheet. Furthermore, since molding can be carried out at high temperatures, the manufacturability has been significantly improved. Furthermore, the product of the present invention has improved heat resistance and compression resistance at high temperatures (temperatures of 100 to 120°C). Therefore, the heat-resistant container made of the composite foamed plastic sheet of the present invention utilizes its cushioning properties to
It can be effectively used as a container for mechanical parts, electronic parts, etc. In addition, containers formed with a polypropylene foam sheet layer arranged on the inner surface,
It can be used as a heat-resistant food container with oil resistance, and is also suitable as a container for cooking food in a microwave oven. Example A heat-resistant container was prepared by thermoforming a laminate of polystyrene foam sheet a and polypropylene foam sheet b having the sheet thickness ratio shown in Table 1, and its thermoformability and high-temperature compressive strength were tested using the following test method. Examined. The results are shown in Table 1. [Thermoformability] The surface of the polyprolene foam of the composite sheet was heated to 130℃,
The surface of the polystyrene foam was heated to a temperature of 105°C and molded into a rectangular container with a projected area of 200 cm ² and a depth of 2 cm, and the molded state was observed. [Heat resistance] Prepare a small insulated box with one opening, install a heater inside, and cover the opening with the composite sheet shown in Table 1 (on the polypropylene foam side).
After setting the inside of the small box to 120°C using a heater and leaving it for 30 minutes, the sheet was observed. [High temperature compressibility] A load (30 kg) consisting of a 5 cm diameter cylindrical iron body heated to a temperature of 120°C was placed on the composite sheet shown in Table 1 (with the polypropylene foam on top), and
After leaving it for a few minutes, the load was removed and the thickness before and after the load was applied was measured. 0.7≦H……○ 0.7＞H……× However, H=
Thickness of the sheet after removing the load (mm) / Thickness of the sheet before applying the load (mm) [Shape retention] The composite sheet shown in Table 1 was (same as the one listed in the column),
After filling the container with water to the 8th minute mark, pinching the top edge at two points and lifting the container, the deformation of the container was observed. ○...No particular change ×...The container was greatly deformed and water spilled out. 【table】

*: Use polyethylene foam sheet (c) instead of polypropylene foam sheet

[Brief explanation of the drawing]

Figure 1 shows an example in which a polypropylene foam sheet is laminated on one side of the polystyrene foam sheet used in the present invention, and Figure 2 shows an example in which polypropylene foam sheets are laminated on both sides of the polystyrene foam sheet used in the present invention. shows. FIG. 3 is an explanatory view of a typical heat-resistant container according to the present invention, and FIG. 4 is a sectional view taken along the line -- in FIG. 3. a...Polystyrene foam sheet, b...Polypropylene foam sheet, 1...Heat-resistant container, 2
……glue.

Claims (1)

[Claims for Utility Model Registration] It has a structure in which a polypropylene foam sheet b is laminated on at least one side of a polystyrene foam sheet a, and the thickness B of the polypropylene foam sheet b and the polystyrene foam sheet a A heat-resistant container made by thermoforming a composite foamed plastic sheet whose thickness A satisfies the following: 1 (mm)≦A+B≦30 (mm) and 0.01≦B/A≦10.