JPS6226313B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides an easy-peel product which is characterized in that when the sealing layer on one side to be sealed is a polypropylene layer, the other sealing layer has adhesive properties with the polypropylene layer, and can be easily opened while being sterilizable by boiling or retort. Regarding possible films. Currently, in the field of food packaging, boiling or retort sterilization is often used to protect the contents and extend shelf life. For this reason, care is taken to select packaging materials and seal strength to avoid pinholes or seal leakage during sterilization, but if the seal strength is too strong, the package cannot be opened easily and the contents are difficult to remove. For this reason, as a result of intensive research into packaging that can be sterilized by boiling or retort sterilization in the temperature range of about 80℃ to 130℃, and which can be easily opened, we found that the sealing layer on one side to be sealed is a polypropylene layer (PP). , the other seal layer has a melt flow of 8g/230°C.
Polypropylene 20-65% by weight and density less than 10 minutes
0.935 or higher high density polyethylene (HDPE) 35~
We were able to achieve this goal by using a film layer with a blend of 80% by weight. Conventionally, when the sealing layer on one side is a PP layer, a PP layer is also used as the other sealing layer in terms of sealing performance, but in this case, the sealing performance is of course sufficient and there is no problem with boiling or retort sterilization. However, due to the strong seal, a knife or scissors had to be used to open the package, which caused problems with the ease of opening, and it was not easy to peel. Therefore, even when the sealing layer is a PP layer, we conducted extensive research and considered whether it was possible to create a package that has good sealing performance, can withstand boiling or retort sterilization, and is also easy to peel. By configuring the system as described above, the purpose could be satisfied. Generally, the PP layer and the PE layer cannot be heat-sealed, but when the easy-peelable film of the present invention is used as a sealing layer, even if the film layer contains 80% by weight of HDPE, it can be heat-sealed with the PP layer. Alternatively, it has the characteristics of being able to be retort sterilized and easily peeled. There is a film that blends LDPE with 5 to 10% by weight PP in order to improve the cold resistance of PP, but this is only for the purpose of modifying the PP, and when this film is sealed with a PP film, it is easy to peel. This is completely different from the purpose of the present invention. Next, the easy-peelable film of the present invention will be described. Although the film of the present invention may be a single layer, it is generally a composite layer in which the easy-peelable film of the present invention is used as a sealing layer and other films are laminated thereon. Films are often used, for example, composite films laminated with nylon, polyester films, or PP films are often used to reduce deformation of the package. Regarding the selection criteria for obtaining the film of the present invention, firstly, the melt flow of PP is 8 g/
If it exceeds 10 minutes, the compatibility with PE becomes extremely poor and a good appearance cannot be obtained, and if the blend ratio of PP is less than 20%, the sealing strength with the PP on the side to be sealed becomes extremely small. It is not practical, and furthermore, when the blending ratio of PP exceeds 70%, there is no blending effect of PE and the sealing strength between PPs makes it impossible to peel easily. Next, the lower the density of PE blended with PP, the higher the blending ratio of PE must be. For example, for PE with a density of 0.925, good easy peelability can be obtained with a blending ratio of 50 to 80% by weight. However, the heat resistance of the seal layer was poor, and the seal part peeled off or the package was deformed during boiling or retort sterilization at temperatures above 80°C. PE with a density of 0.935 or higher can be sterilized by boiling or retort, but with a density of 0.94 or higher,
HDPE gives a more desirable result. As mentioned above, the sealing layer on the other side to be sealed is a PP layer, and a sealing temperature of 170 to 190°C is suitable. Next, Examples will be described.As seen in these examples, although the package has a heat sealing strength that does not cause the package to tear or seal to leak during boil or retort sterilization,
The packaging is easy to open. Example 1 PP with melt flow of 4g/10min at 230℃
and high-density PE with a density of 0.95 are blended in the ratio shown in Table 1, and the width is
A 50μ film was extruded using a 900mm T-die. This film was dry-laminated with a 12 μm polyester film to form a composite film, which was used as a lid material, and heat-sealed with a 0.5 mm thick PP sheet at a melt flow of 0.7 g/10 minutes. Seal temperature is 160℃, 180℃
Heat-sealing was carried out at three levels: and 200°C, sealing time was 3 seconds, and sealing pressure was 2 kg/cm ² . After this sample was immersed in hot water at 90°C for 30 minutes, the seal strength was measured and the results are shown in Table 2.

【table】

[Table] Example 2 Melt flow 0.7g/10min PP at 230℃
and PE having a density of 0.945 or 0.923 were blended in the ratios shown in Table 1, and a 0.6 mm sheet was extruded using a 120 mm L/D = 28 extruder using a T die with a width of 1500 mm. This sheet was vacuum formed into a cup with a diameter of 50mm and a depth of 30mm, and after filling with water, the polyester 12μ/
Hot plate sealing was performed over a 60φmm width of 5mm using a composite film made of CPP 50μ (sealing layer) as a lid material. The sealing conditions were the same as in Example 1. This sample was placed in a hot water bath at 90°C and a retort pot at 120°C for 30 minutes, and then the deformation of the cup and the seal strength were measured. The results are shown in Table-3 and Table-4.

【table】

【table】

Claims (1)

[Claims] 1 Melt flow of seal layer at 230℃ is 8
It consists of a film layer that is a blend of 20-65% by weight of polypropylene with a density of 0.935 g/10 minutes or less and 35-80% by weight of high-density polyethylene with a density of 0.935 or more, and can be sterilized by boiling or retort, and the seal layer can be easily peeled. A film featuring