JPH1086305A - Composite sheet for electromagnetic wave cooking container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite sheet used suitably for a container for cooking or heating contents by an electromagnetic wave cooking implement such as a microwave oven with excellent heat resistance and transparency. SOLUTION: The composite sheet for electromagnetic wave cooking contrainer comprises a polyethylene terephthalate resin layer A, a polycarbonate resin layer B, an enzyme barrier layer C, a heat sealing layer D, and an acid modified polyolefin layer E in such a manner that total thickness of the layers A and B is in a range of twice to eight times as large as total thickness of the layers C, D and E, and a thickness ratio of the layer A to the layer B is in a range of A:B=(2.5:1) to (1:2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sheet excellent in heat resistance, transparency and the like which can be suitably used for a container for cooking or heating contents with an electromagnetic cooker such as a microwave oven.

[0002]

2. Description of the Related Art A thick container made of a polyester resin having excellent heat resistance is used as a container for cooking or heating the contents by an electromagnetic wave used in an electromagnetic wave cooker such as a microwave oven. However, there is a problem in that the content is usually white, inferior in transparency, and the contents are difficult to see.

[0003] In place of the polyester resin,
Containers formed by processing a polypropylene resin simple sheet or a composite sheet consisting of a polypropylene resin sheet and another resin sheet are also used, but as above, they have excellent heat resistance, but their contents are poor in transparency and poor. There was a problem that it was hardly visible.

[0004]

DISCLOSURE OF THE INVENTION The present invention has found a composite sheet for an electromagnetic wave cooking container which can solve the above-mentioned problems. The gist of the present invention is to provide a polyethylene terephthalate resin layer (A layer) and a polycarbonate resin. Layer (B
Layer), oxygen barrier layer (C layer), heat seal layer (D
Layer) and an acid-modified polyolefin resin layer (E layer), wherein the total thickness of (A + B) is 2 of the total thickness of (C + D + E).
For an electromagnetic wave cooking container, wherein the thickness ratio of the A layer and the B layer is in the range of (2.5: 1) to (1: 2). In the composite sheet.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyethylene terephthalate resin layer (A layer) and the polycarbonate resin layer (B layer) used in the present invention are for imparting rigidity. The polyethylene terephthalate resin of the A layer has an intrinsic viscosity (IV) of 0.6 to 0. .8 can be suitably used. The polycarbonate resin of the layer B preferably has a molecular weight of 25,000 or less, and if it exceeds 25,000, the molding temperature tends to be high and moldability tends to be poor.

For the oxygen barrier layer (C layer), a saponified ethylene vinyl acetate copolymer or a polyamide resin having excellent oxygen barrier properties can be used, and a single layer or a plurality of layers may be used. As the saponified layer and the plurality of layers, a layer configuration of (a saponified ethylene vinyl acetate copolymer layer / a polyamide resin layer) and a layer structure of a (a polyamide resin layer / a saponified ethylene vinyl acetate copolymer layer / a polyamide resin layer) are preferable. Can be used.

The plural layers (polyamide resin layer / saponified ethylene vinyl acetate copolymer layer / polyamide resin layer) prevent surface roughness which is likely to occur between the saponified ethylene vinyl acetate copolymer and the adhesive resin, and prevent interlayer damage. Adhesive strength can be increased.

Examples of the polyamide resin for the C layer include ordinary nylon 6, nylon 66, nylon 6/66, nylon 6T / 6I, etc., and nylon 6/66 which is easily coextruded with a saponified ethylene vinyl acetate copolymer. Can be preferably used.

For the heat seal layer (D layer), a normal polyolefin resin can be used, but it is preferable to use a polypropylene homopolymer having a melt index (according to MI JIS K7210) of 1.50 or less. At a draw forming temperature of about 140 ° C. to 150 ° C., there is an advantage that it is easy to prevent a decrease in the transparency of a molded product due to being taken into a hot plate.

The acid-modified polyolefin layer (E layer) is a polyolefin resin grafted with at least one monomer selected from unsaturated carboxylic acids or derivatives thereof, and is provided between any of the layers A to C. Thus, the layers can be firmly bonded.

Here, in the composite film of the present invention, the total thickness of (A + B) is 2 times the total thickness of (C + D + E).
It is necessary to be in the range of times to eight times. If it is less than twice, rigidity can be imparted to the composite film, and if it exceeds eight times, there is a problem that the punching property of the film is poor.

Further, regarding the thickness ratio between the layer A and the layer B,
Layer: Layer B = (2.5: 1) to (1: 2). If the thickness of layer A exceeds 2.5 times the thickness of layer B, it may be caused by heating in a microwave oven or the like. If the container is easily deformed by heat and the thickness of the layer B exceeds twice the thickness of the layer A,
This is because it becomes difficult to form the container by deep drawing.

Hereinafter, the present invention will be described in detail with reference to examples.

[0014]

EXAMPLES Example 1 A layer of polyethylene terephthalate resin (PET: intrinsic viscosity (IV) 0.78, thickness 150 μm)
m), polycarbonate (PC: thickness 150μ) in layer B
m), saponified ethylene-vinyl acetate copolymer (EVOH: ethylene content: 44 mol%, thickness: 10 μm)
m), acid-modified polyolefin resin (thickness 10 μm)
m), and a polypropylene homopolymer (PP: MI
= 1.40, thickness 30 µm) and a composite sheet having the following layer constitution was formed by a co-extrusion method. PET / PC / AD / EVOH / AD / PP 150 μm / 150 μm / 10 μm / 10 μm / 10 μm / 30 μm A + B / (C + D + E) = 5 A: B = 1: 1

(Example 2) A composite sheet having the same contents as in Example 1 and the thickness of each layer described below was formed by co-extrusion. PET / PC / AD / EVOH / AD / PP (MI 1.20) 200 μm / 100 μm / 7 μm / 10 μm / 7 μm / 26 μm A + B / (C + D + E) = 6 A: B = 2: 1

Example 3 A composite sheet having the same contents as in Example 1 and the thickness of each layer as described in Example 1 was formed by co-extrusion. PET / PC / AD / EVOH / AD / PP (MI 1.20) 170 μm / 80 μm / 10 μm / 10 μm / 7 μm / 23 μm A + B / (C + D + E) = 5 A: B = 2.1: 1

(Example 4) A composite sheet having the same contents as in Example 1 and the thickness of each layer described below was formed by co-extrusion. PET / PC / AD / EVOH / AD / PP (MI 1.20) 100 μm / 180 μm / 10 μm / 10 μm / 10 μm / 30 μm A + B / (C + D + E) = 4.7 A: B = 1: 1.8

(Example 5) The C layer was formed of (polyamide resin layer /
(EVOH layer / polyamide resin layer), wherein the polyamide resin (Ny) is 6-66 with 66% nylon component.
A composite sheet having the same contents as in Example 1 except that it is made of nylon and having the following layer thicknesses was formed by a co-extrusion method. PET / PC / AD / Ny / EVOH / Ny / AD / PP 150 μm / 150 μm / 5 μm / 5 μm / 10 μm / 5 μm / 5 μm / 30 μm A + B / (C + D + E) = 5 A: B = 1: 1

Example 6 A composite sheet having the same contents as in Example 5 and the thickness of each layer described below was formed by coextrusion. PET / PC / AD / Ny / EVOH / Ny / AD / PP 100 μm / 180 μm / 5 μm / 5 μm / 10 μm / 5 μm / 5 μm / 50 μm A + B / (C + D + E) = 3.5 A: B = 1: 1. 8

(Comparative Example 1) The MI of the PP of the D layer is 1.50.
A composite sheet having the same contents as in Example 5 except that the thickness of each layer was the same as in Example 5, and the thickness of each layer was as follows, was formed by co-extrusion. PET / PC / AD / Ny / EVOH / Ny / AD / PP 250 μm / 50 μm / 10 μm / 5 μm / 10 μm / 5 μm / 7 μm / 30 μm A + B / (C + D + E) = 4.5 A: B = 5: 1

(Comparative Example 2) The MI of the PP of the D layer is 1.60.
A composite sheet having the same contents as in Example 1 except that the thickness of each layer was the same as that of Example 1 and the thickness of each layer was as follows, was formed by coextrusion. PET / PC / AD / EVOH / AD / PP 70 μm / 230 μm / 10 μm / 10 μm / 7 μm / 23 μm A + B / (C + D + E) = 6 A: B = 1: 3.29

Comparative Example 3 A composite sheet having the same contents as in Example 5 except that the PP of the D layer was replaced with a PP-PE random copolymer having an MI of 1.10. A film was formed by a co-extrusion method. PET / PC / AD / Ny / EVOH / Ny / AD / PP-PE 100 μm / 100 μm / 10 μm / 15 μm / 30 μm / 15 μm / 10 μm / 70 μm A + B / (C + D + E) = 1.33 A: B = 1: 1

Using the composite sheet having the above-described contents, the results of evaluation of "moldability", "transparency", "heat resistance", "adhesive strength" and "film forming property" are shown in Table 1. The evaluation method is as follows.

[Evaluation Method] Formability Perform deep drawing test using FX6300 manufactured by Omori Machinery Co., Ltd. ・ Molding die: For gas pack (120 mm long × 160 mm wide)
X Depth 25 mm)-Molding heating method: Normal heating (heating from the sealing surface)-Heating time: 10 seconds-Molding time: 3 seconds When molding under the above conditions, moldable at molding temperature of 155 ° C or less (○ ) At 155 ° C. (×) where sufficient molding was not possible.

2. Transparency The haze at the bottom was measured using the molded article of the above item 1. The haze was within 8% (○), the haze exceeded 8% and within 10% (△), and the haze exceeded 10% (×).

3. Heat resistance The molded article of the above 1 was placed in a gear oven at 120 ° C. for 60 seconds, and the degree of deformation of the molded article was visually evaluated. No deformation was observed (○), slight deformation was observed (△), and significant deformation was observed (x).

4. Adhesive strength Ten samples of adhesive strength measurement (15 mm width) were arbitrarily collected from the raw sheet, and a tensile tester (tensile speed: 200 mm /
) Was used to measure the interlayer adhesion strength between EVOH / AD or Ny / AD.

5. Film-forming properties When co-extruded with a die (T die), it was confirmed whether or not each resin spread over the effective width. ◎: Each layer is fully developed, and is stably developed even when the thickness of each layer is changed. ○: Developed △: Developed but is almost at the limit of effective width ×: Not expanded

[Table 1]

From Table 1, it can be seen that Examples 1 to 6 have good moldability, transparency, heat resistance, adhesive strength and film forming properties. On the other hand, it can be seen that Comparative Example 1 in which the thickness of the A layer is too thick is inferior in heat resistance, and Comparative Example 2 in which the thickness of the B layer is thick is inferior in moldability. Further, it can be seen that Comparative Example 3 in which the total thickness of (A + B) is less than twice the total thickness of (C + D + E) is inferior in transparency.

[0030]

As described above, the composite sheet of the present invention is excellent in heat resistance, transparency and the like, and can be suitably used for a container for cooking or heating contents using an electromagnetic cooker such as a microwave oven.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Masahiro Takasaka 5-8, Mitsuya-cho, Nagahama-shi, Shiga Prefecture

Claims (2)

[Claims] 1. A polyethylene terephthalate resin layer (A)
Layer), a polycarbonate resin layer (B layer), an oxygen barrier layer (C layer), a heat seal layer (D layer), and an acid-modified polyolefin resin layer (E layer), and the total thickness of (A + B) is the sum of (C + D + E) The thickness is in the range of 2 to 8 times the thickness and the thickness ratio of the A layer and the B layer is A layer: B layer = (2.5:
A composite sheet for an electromagnetic wave cooking container, which is in the range of 1) to (1: 2). 2. An oxygen barrier layer (C layer) comprising a saponified ethylene vinyl acetate copolymer layer, a polyamide resin layer / a saponified ethylene vinyl acetate copolymer layer, and a polyamide resin layer / ethylene vinyl acetate saponified layer. Saponified polymer layer /
The composite sheet according to claim 1, wherein the composite sheet is selected from the group consisting of a polyamide resin layer).