JPH02293138A - Laminate - Google Patents

Abstract

PURPOSE:To improve the heat resistance, rigidity and gas barrier properties of a laminate by laminating a gas barrier layer composed of a saponified ethylene/vinyl acetate copolymer or a polyvinylidene chloride resin to a high crystalline polypropylene layer having a specific composition. CONSTITUTION:A laminate consisting of a high crystalline polypropylene (HCPP) mixed with 1 - 20wt.% of polyethylene and at least one gas barrier layer com posed of a saponified ethylene/vinyl acetate copolymer (EVOH) or a polyvinylidene chloride resin (PVDC) is formed. Concretely, the laminate consisting of a layer A(HCPP), a layer B(adhesive layer), a layer C(gas barrier layer), B and A is formed by respectively melting molding materials by different extruders and guiding the same to a coextrusion die. The obtained laminate has heat resistance, rigidity and gas barrier properties and is easy in heat mold ing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a laminate that has excellent heat resistance, rigidity, impact resistance, oxygen gas barrier properties, and moldability, and can withstand severe high-temperature retort sterilization. be. [Prior Art] Research into laminating so-called synthetic resin molded products, particularly molded products such as films and bottle-shaped containers, has been conducted since ancient times. The purpose of this is to utilize m layers of various synthetic resins to utilize the strengths of each resin and compensate for the weaknesses of each resin.
Specifically, heat resistance, water vapor barrier properties, gas barrier properties,
Improvements include oil resistance, chemical resistance, mechanical strength, rigidity, heat sealability, and economic efficiency. Conventionally, polypropylene (hereinafter abbreviated as PP) has been used for food packaging such as containers compatible with retort sterilization and containers compatible with microwave ovens.
laminates containing gas barrier layers and gas barrier layers are widely used. However, there were problems such as the container becoming deformed during high-temperature retort sterilization at temperatures exceeding 110°C or when used in a microwave oven. In addition, PP filled with inorganic substances such as talc and miryoku are used as microwave oven containers for retorts to improve heat resistance and rigidity, but the odor of inorganic surface treatment agents and stabilizers is There were problems such as transfer to content foods. On the one hand, highly crystalline PP with improved intramolecular stereoregularity
As a result, the general properties of conventional PP are not impaired, and it has heat resistance and rigidity that can withstand high-temperature retort sterilization treatment and microwave ovens, and because it does not use inorganic fillers, it is possible to eliminate the odor of surface treatment agents and stabilizers. However, when forming this laminate into a container, there are problems such as some corners cannot be formed, it cannot be pressed deeply, and the impact resistance, especially at low temperatures, is slightly lower than that of general grade PP. It had not been done. [Problems to be Solved by the Invention] In view of the current state of packaging materials for retort sterilization, microwave ovens, and packaging materials, it is an object of the present invention to provide heat resistance, rigidity, force barrier properties, and surface treatment. In order to provide a laminate that is free from the odor of additives and stabilizers and that can be easily thermoformed, we have conducted various studies, and as a result, we have arrived at the laminate of the present invention. [Means for Solving the Problems] The present invention includes at least one highly crystalline PP layer and a gas barrier layer, the PP layer is mixed with 1 to 2 wt% polyethylene, and the gas barrier layer is made of ethylene vinyl acetate. Saponified copolymer (hereinafter abbreviated as EVOH) or
This is a laminate characterized by being made of polyvinylidene chloride (hereinafter abbreviated as PVDC) resin.

The PP layer used in the present invention has a crystallinity of 60 to 70% after sheeting, which has improved intramolecular stereoregularity in order to maintain heat resistance and rigidity without impairing the general characteristics of PP.
It is a highly crystalline PP (hereinafter abbreviated as HCPP) that has a high formability and impact resistance, and is not limited to high density or low density, and is mixed with 1 to 20 wt% of polyethylene (hereinafter abbreviated as PE). This is what I did. In addition, HCPP at this time is preferably homogeneous in order to further improve heat resistance. The gas barrier layer is preferably made of commercially available EVOH having an ethylene content of 20 to 60%, which has excellent gas barrier properties, or commercially available PVDC (either vinyl chloride type or acrylate type copolymerization resistant).

At this time, the adhesive strength is increased by interposing an adhesive layer between the HCPP layer and the gas barrier layer, and in particular, maleic anhydride-modified PP is preferably used for the EVOH layer, and maleic acid-modified ethylene propylene copolymer is preferably used for PVDC. It is not particularly limited to these.

As a method for producing the laminated sheet of the present invention, a coextrusion method is used which provides good interlayer adhesive strength during lamination, but a dry lamination method or an extrusion lamination method may also be used.

〔Example〕

This will be explained below using an example. The following various molding materials were melted using different extruders and introduced into a coextrusion die to form a laminar flow as shown in the figure. Example l A (350μ) /B (25μ) /C (50μ)
/B (25g)/A (350μ), total 800μ A: Homo HCPP such that crystallinity becomes 65% after sheeting with MI-0.5: 80 parts by weight, M+-0.5, density 0.955 (7) High-density PE: 20 parts by weight Blended product B: Maleic anhydride PP C: EVOH with an ethylene content of 32% Example 2 The A layer (PP layer) of Example 1 was combined with a M+-0.5 sheet. High-density PE with M+-0.5 and density 0.955: 5 to 495 parts by weight of homogeneous HCPP that has a crystallinity of 65% after heating.
Part by weight Laminated body replaced with blended material.

Example 3 A (350μ)/B(25μ)/C(50μ)/B(
25μ〆A (350μ), total 800μ A: M+=0.5 homogeneous HCPP with crystallinity of 65% after sheeting: 80 parts by weight with M+=0.5
, density 0. 9 5 5 high density PE: 20 parts by weight blend B = Maleic anhydride modified PP C: EVOH with ethylene content of 32% D: Homo PP with MI-0.5 Example 4 A layer of Example 3 ( PP layer) to MI-0. Birch homo HCPP with crystallinity of 65% after sheeting of 5.
M[=0.5, density 0.5 parts by weight] 9 5 5 high-density PE: 5 parts by weight Laminated body replaced with a blended product.

Example 5 A (350μ)/B(25μ)/C(50μ)/B(
25μ)/A (350μ), total 800μ A: Homogenous HCPP with MI=0.5 and crystallinity of 65% after sheeting: Ml-0.5 in 80 parts by weight
, density 0. 9 5 5 high-density PE: 20 parts by weight blend B: Maleic acid-modified ethylene propylene copolymer C: Commercially available acrylate copolymer PVDC Comparative Example I A (350 μ) / B (25 μ') / C ( 50μ)
/B (25μVA (350μ), total 800μ A: homogeneous PP with M+=0.5 B: maleic anhydride modified PP C: EVOH with 32% ethylene content Comparative Example 2 A layer (PP layer) of Comparative Example 1 , commercially available Mr-0.
A laminate in which the homo-PP of No. 5 was replaced with 40 wt% talc. Comparative Example 3 A laminate in which the A layer (PP layer) of Comparative Example 1 was replaced with homogeneous HCPP such that the crystallinity of the sheeting layer with MI=0.5 was 65%.

Comparative Example 4 The A layer (PP layer) of Comparative Example 1 was made of homogeneous HCPP with a crystallinity of 65% after sheeting with Ml-0.5: 75
M I-0. 5. Density 0. 9 5 5
The laminate was replaced with a blend of 15 parts by weight of high-density PE.

Comparative example 5 A (350μ)/B (25μ)/C (50μ)/B(
25 μ)/A (350 μ), total 800 μ A: Homo PP with MI-0.5 B: Maleic acid-modified ethylene propylene copolymer C: Commercially available acrylate copolymer PVDC Comparative Example 6 with Ml-0.5 Birch homo HCPP with a crystallinity of 65% after sheeting: 80 parts by weight, M I - 0.5,
Density 0. A monolayer of 800μ of a blend of 20 parts by weight of high-density PE of 955. Table 1 shows the results of the following experiments performed on the laminate obtained above.
It is shown in - Gas barrier properties were measured at 20°C and 65% RH using an oxtran machine manufactured by Mocon. - Rigidity was measured using an Orenzen bending stiffness measurement method in accordance with ASTM-D747-6. - Impact resistance was measured using the Dipon impact measurement method (according to JIS-K671B) at 23°C, 0°C, and -20°C.・For moldability and heat resistance (retort suitability), the obtained laminate was placed in a vacuum-pressure forming machine at a sheet temperature of 150"C.
, aperture ratio approximately 172, upper diameter 65mφ x lower diameter 60-φX
A molded product was obtained by thermoforming in a 30mH round cup-shaped mold and was used for experiments. Formability was evaluated based on uneven thickness after thermoforming and whether some corners could be formed sharply. Regarding heat resistance (retort suitability), fill the molded container with 70% water, complete with all-sealant material, and heat up to 130°C
After 30 minutes of retort processing, the molded product was evaluated for dents and other deformations. 4.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the laminate of the present invention.

Claims (1)

[Claims] (1) A laminate characterized by containing at least one highly crystalline polypropylene layer mixed with 1 to 20 wt% polyethylene and a gas barrier layer of saponified ethylene vinyl acetate copolymer or polyvinylidene chloride resin. body.