JPH0911421A - Laminated body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give heat resistance and oil resistance to a laminated body by a structure wherein the laminated body is made respectively of a specified sealing layer, an adjacent layer, an intermediate layer and a base material layer from inside in the order named under the condition that the melt index of the sealing layer is larger by a specified value than that of the intermediate layer and the separation strength between the sealing layer and the adjacent layer is weaker than that between the adjacent layer and the intermediate layer and is of a specified separation strength value. SOLUTION: This laminated body consists from inside of at least four or more layers or a polypropylene sealing layer as the first layer, an adjacent layer made of a mixture of 20-90wt.% of polypropylene and 80-10wt.% of 4-methypentene-1 as the second layer, an intermediate layer made of polypropylene having the melt index of 0.5-30 as the third layer and a base material layer mainly made of polypropylene mixed with 0.01-1wt.% of a nucleating agent and having the melt index of 0.01-4 as the outermost layer. The melt index of the sealing layer 1.1 or more times as high as that of the intermediate layer and the ply separation strength between the sealing layer and the adjacent layer is set to be weaker than that between the adjacent layer and the intermediate layer and the separation strength is set to be 0.2-2.5kg/15mm under the pulling speed of 300mm/min.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a packaging field, in particular, a laminate which is preferably used in the production of containers, and a sealing property, an opening property, for accommodating and packaging foods, chemicals and the like produced using the same.
The present invention relates to an easily openable container having excellent transparency.

[0002]

2. Description of the Related Art There is an increasing number of containers in which foods are sealed in plastic containers, subjected to high temperature sterilization treatment, and stored and distributed.
In addition, there are cases where the product is heated by a microwave oven when it is used by the consumer, and when the content contains oil, the temperature of the content may become high. It has an excellent sealing property and an excellent opening property. As a container with excellent sealing and easy opening properties,
Rather than performing the peeling of the seal portion that is generally performed during use, a multi-layer container is used as the container, and the layers of the multi-layer container are used as the opening / peeling surface, and both the sealing property and the easy-open property are achieved. Have been proposed (Japanese Patent Application Laid-Open No. 50-375).
98, Japanese Patent Publication No. 5-63385, Japanese Patent Publication No. 5-
79587). However, in these containers, since the release layer is PE (polyethylene), the high temperature treatment condition is 120 ° C as the upper limit, and when the cooked food containing a large amount of oil is filled, the release layer shows swelling. However, there was a defect that the seal layer was broken due to the softening of the seal layer due to the high temperature. For the purpose of compensating for these drawbacks, a container having a layer structure in which the heat resistance is increased by using a polypropylene resin as the innermost layer as disclosed in Japanese Patent Publication No. 7-2409 is proposed. Although the heat resistance is improved as compared with the above, PE is still used as an intermediate layer in these constitutions in order to enable peeling, and although some improvement in heat resistance is recognized, sterilization at a higher temperature (ex 130 (° C), the intermediate layer is softened and melted, so that the laminate strength between the intermediate layer and the surface layer is rapidly reduced, peeling occurs during sterilization, and the sealing performance is impaired. In addition, the transparency that allows the contents to be seen through was difficult for fog to occur in the production of a laminate with a conventional polypropylene-based resin, but it is necessary to add a nucleating agent to polypropylene to minimize the crystal structure during lamination. Solved by. However, when the conventional seal layer and intermediate layer are made of polyethylene, the transparency of polyethylene is inferior, so that there is a drawback that the transparency is deteriorated when the laminate is formed.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is a laminate suitable for use in the production of an easily openable container having a heat seal layer and an opening and peeling layer separated from each other, the opening and peeling layer (sealing layer). The present invention provides a laminate having heat resistance, oil resistance, and transparency while ensuring the easy peelability.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a laminate used for producing an easily-openable container has a specific layer structure, It has been found that the above problems can be solved, and the present invention has been completed based on this finding. That is, the present invention
The seal layer (A) in which the first layer is polypropylene from the inside, and the second layer is 20 to 90% by weight of polypropylene and 4
Adjacent layer (B) consisting of a mixture of 80 to 10% by weight of methyl pentene 1 resin and the third layer are melt index (JIS
K6758) A middle layer (C) made of polypropylene of 0.5 to 30 and an outermost layer of 0.01% to 1% by weight of a nucleating material are blended, and polypropylene having a melt index of 0.01 to 4 is mainly used. Which has a base layer (D) to be used, the melt index of the seal layer (A) is 1.1 times or more the melt index of the intermediate layer (C), and the interlaminar peel strength between (A) and (B) is ( B) A laminate characterized by being weaker than the interlaminar peel strength between (C) and having a peel strength of 0.2 to 2.5 kg / 15 mm (pulling speed 300 mm / min) and comprising at least 4 layers or more. , Middle layer if necessary
(B) is obtained by adding 3 to 20 parts by weight of polyethylene or unsaturated carboxylic acid-modified polypropylene to 100 parts by weight of a mixture consisting of 20 to 90% by weight of polypropylene and 80 to 10% by weight of 4-methylpentene 1 resin. It is a laminated body which is a composition, and preferably the thickness of the innermost layer (A) is
It is a laminated body having a thickness of 1 to 100 μm or less.

The seal layer (A) of the present invention is made of polypropylene (hereinafter referred to as PP), and by using this PP, a laminate having heat resistance, oil resistance and transparency can be obtained. Further, the melt index (JISK6758) of PP used in (A) needs to be larger than 1.1 times that of PP used in (C). We found that the difference in PP melt index (hereinafter referred to as MI) controls delamination from the adjacent layer (B). That is, it was found that the two interlaminar peel strengths sandwiching (B) are influenced by the MI of PP adjacent to (B), and the interlaminar peel strength of the larger MI is smaller. In the case of the present invention, it is necessary to peel between (A) and (B), and if the MI of (A) is 1.1 times or more the MI of (C), the interlaminar peel strength between (A) and (B) Is smaller than the interlaminar peel strength between (B) and (C), which is suitable for easy opening.
Further, the thickness of (A) is preferably 5 to 100 μ, and 5 μ
If it becomes smaller, the sealing will be insufficient. On the contrary, if it becomes larger than 100 μ, the opening feeling may be impaired. As the PP to be used, various PPs of homo, block and random can be arbitrarily used as long as MI is 1.1 times or more of (C). Considering the sealing property with the lid and the moldability, PP10
It is also possible to blend 3 to 20 parts by weight of polyethylene with 0 parts by weight. In addition to polyethylene, blends of thermoplastic resins such as unsaturated carboxylic acid-modified polyolefin and ethylene vinyl acetate can also be used for heat release with the intermediate layer.
It is possible as long as the transparency is not impaired.

The intermediate layer (C) of the present invention is intended to control heat resistance and peel strength. Mainly polypropylene is used, and as its type, various polypropylenes such as homo, random, block and the like and mixtures thereof are used. Further, one of the purposes of the intermediate layer is to adjust the interlaminar peel strength with the adjacent layer (B), and it is necessary that the MI be 0.5 to 30. When the MI is 30 or more, it is difficult to adjust the interlaminar peel strength between (A) and (B) and between (B) and (C), and it is difficult to provide a difference in interlaminar peel strength. Further, when these conditions are satisfied, it is possible to blend an arbitrary thermoplastic resin such as polyethylene for the purpose of adjusting moldability and the like. The substrate layer (D) of the present invention is intended to maintain the strength, transparency, and moldability of the laminate. P used for (D)
There are various types of PP such as homo, random, and block, and a mixture thereof may be used, but from the viewpoint of transparency which is the purpose thereof, 0.01% by weight to 1% by weight of a nucleating agent is blended. To be done. As the nucleating agent to be blended, silica,
There are talc, dibenzylidene sorbitol, etc., and other ones can be used optionally. Further, petroleum resin can be used as a nucleating agent. This petroleum resin may be either alicyclic or aliphatic, and this effect is usually PP.
The crystal structure of is an α to β structure, whereas it is a smectic structure. Here, it is treated as a nucleating agent. Also, MI
If polypropylene having a ratio of 0.01 to 4 is used, any thermoplastic resin such as polyethylene can be blended in order to improve moldability and the like.

The adjacent layer of (B) of the present invention plays the most important role in the present invention, and this layer is mainly composed of a blend of polypropylene and 4-methylpentene-1 resin. The blending ratio is arbitrary, but 90 to 20% by weight as the amount of polypropylene and 80 to 10% by weight as the 4-methylpentene 1 resin are preferable, but the most preferable compounding ratio is 80 to 40% by weight as the amount of polypropylene. If the amount of polypropylene is 90% by weight or more, unsealing becomes difficult, while if it is 20% or less, the delamination strength becomes weak and delamination may occur. It is also possible to blend polyethylene in order to adjust the delicate delamination strength, but if the blending amount is too large, the target heat resistance may be impaired, and the blending amount is based on 100 parts by weight of polypropylene. Therefore, the upper limit is 20 parts by weight, and if the blending amount is small, the interlaminar peel strength cannot be adjusted. Therefore, the lower limit is preferably 3 parts by weight. Similarly, unsaturated carboxylic acid-modified polypropylene may be blended in order to adjust the delicate delamination strength, but with this blend too, if the blending amount is too large, the peeling strength is increased and the blending amount is small. 20 parts by weight or less 3
It is desirable that the amount is more than weight part.

Further, in addition to the four layers (A) to (D), any resin can be laminated outside the (D) layer or between the (C) layer and the (D) layer. As the resin to be laminated, polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT),
Polypropylene (PP), vinylidene chloride resin (PVD
C), ethylene vinyl alcohol copolymer (EVO
H), polypropylene filled with inorganic material, and the like. Also (D)
The outer layer and between the (B) layer and the (C) layer are not limited to a single layer but may be arbitrarily selected such as a multilayer. In this case, unsaturated carboxylic acid-modified polypropylene is preferable as the adhesive layer (AD). That is, the outside of the (D) layer or the (C) layer and the (D) layer
The layers added between the layers are PP / AD / EVOH / A
D / PP, PP / AD / PVDC / AD / PP, etc. can be arbitrarily selected. Other than that, not only plastic but also metal layers such as aluminum foil and steel foil can be used. In particular, when it is necessary to improve the oxygen gas barrier property of the laminate, an ethylene vinyl alcohol copolymer is used by being laminated on the outside of the (D) layer or between the (C) layer and the (D) layer. The ethylene polymerization ratio is 20
Those having a content of up to 50% by weight are optionally used according to the purpose.
Further, when the ethylene vinyl alcohol copolymer is used between the (C) layer and the (D) layer, considering the moldability, the same type of PP as the (C) layer or another PP is provided after the (C) layer. When it is used through the PP of the kind, the moldability is improved. The layer structure of the present invention can be obtained by coextrusion, laminating or the like using the above resin. As the laminating process, any method such as extrusion laminating, coextrusion laminating, dry laminating or thermal laminating can be used. That is, the layer structure is A / B / C / AD / EVO
It is preferable that the number of layers is H / AD / D.

[0009]

The most important point of the present invention is to blend the adjacent layer (B) of polypropylene with 4 methylpentene 1 resin. The melting point of polypropylene is usually about 150 ° C. for random PP and about 160 ° C. for homo PP. On the other hand, the melting point of 4-methylpentene 1 is about 240 ° C. By blending these, it has a heat resistance of 15 ° C or higher as compared with the conventional intermediate layer mainly composed of polyethylene,
Even if the temperature of the contents becomes high (for example, 140 ° C. or higher) during sterilization, the intermediate layer does not soften or melt. For example, the melting point of HDPE (high density polyethylene), which has the highest heat resistance as compared with the case of conventional PE, is around 135 ° C. When the temperature exceeds 120 ° C, the softening progresses rapidly, and the interlayer peel strength between the seal layer and the intermediate layer is 1.
Even if the width was 0 to 1.5 kg / 15 mm, it was 125 ° C.
Peeling strength is 0-0.2kg if you experience the heat of
/ 15mm and it will fall sharply. Therefore, 125 ℃
In the above sterilization at high temperature, if the pressure change during sterilization causes the lid material to swell even a little, the seal layer and the intermediate layer are easily peeled off, and the state as a sealed container cannot be maintained. Becomes On the other hand, according to the present invention, when the intermediate layer is used, the heat resistance of the intermediate layer itself is excellent even at a high temperature treatment of 130 ° C. or higher, so that the above-mentioned form does not occur, and stable high temperature treatment becomes possible. . Further, when a blend of polypropylene and 4-methylpentene-1 resin is laminated, easy peeling property is exhibited. The strength depends on the blending ratio. For example, when the mixing ratio is 50 to 90% by weight of polypropylene, the interlayer adhesion strength is in the range of easy peeling strength of 0.5 to 2.5 kg / 15 kg. . Therefore, the peeling of the seal layer can be easily performed.

The laminate of the present invention is molded and used as a container, and is sealed with a lid material. The lid is opened between the (A) layer and the (B) layer and must be easily opened. I won't.
Therefore, the delamination strength between (A) and (B) is 0.2-2.5kg.
/ 15 mm (pulling speed 300 mm / min), and in order to perform peeling smoothly at this time (C)
It is also necessary to take the delamination strength between (D) into consideration.
When the delamination strength between (B) and (C) is smaller than the delamination strength between (A) and (B), delamination may occur between (B) and (C), and unsealing is not stable. Therefore, to easily open the package, the interlaminar peel strength between (A) and (B) should be (B).
It is necessary to make it smaller than the interlaminar peel strength between (C).
Therefore, the strength can be adjusted by changing the MI of PP used in (A) and (C). That is, the MI of the PP of (A) is set to 1.
The present invention has found that this relationship is established by making the ratio 1 or more. Therefore, the seal layer of the lid material and the seal layer (A) must be firmly adhered to each other. Normally, the material of the seal layer of the lid material is the same as or the same as the material of the seal layer (A). It Further, in order to improve the opening property, the thickness of (A) is preferably in the range of 5 to 100 μm. If it is less than 5μ, the sealing performance is impaired, and conversely 1
If it is at least 00 μ, the unsealing property may be impaired.

[0011]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Table 1
Table 3 shows the constituent resins and layer thicknesses of the laminate structures of Examples and Comparative Examples, and Tables 2 and 4 show Examples and Comparative Examples of these laminates (A) and (B) before and after heating. Laminating strength of (B) and (C) before and after heating,
Proper sterilization of containers made from each laminate, internal pressure resistance,
Shows heat resistance and openability. These laminates were laminated by a coextrusion method in which they were kneaded and extruded by separate extruders and introduced into a multi-layer die.

The resins used in the examples and comparative examples are as follows. -PP1: polypropylene (homo) MI = 0.
5 · PP2: polypropylene (random) MI = 2.
0 · PP3: polypropylene (homo) MI = 1.
5 * PP4: polypropylene (homo) MI = 3.
0-PP5: Polypropylene (homo) MI = 20-PP6: Polypropylene (random) MI = 35-PP7: Polypropylene (random) MI = 32-PP8: Polypropylene (block) MI = 2.
0-AD: carboxylic anhydride-modified polypropylene-EVOH: ethylene vinyl alcohol copolymer-MP: 4-methylpentene 1-HDPE: high-density polyethylene-modified PP: carboxylic acid-modified polypropylene-Z: nucleating agent dibenzylidene sorbitol

The evaluations in the examples and comparative examples were carried out by the following methods. Laminate strength before heating: The laminate strength between (A) and (B) and between (B) and (C) of the laminate is measured. Pulling speed
300 mm / min. (Peeling by 180 degrees) -Lamination strength after heating: The laminate is left under a dry heat condition of 135 degrees for 1 hour and then the laminate strength between (A) and (B) and between (B) and (C) of the laminate. Measure. Pulling speed 300 mm / min. (Peeling by 180 degrees) ・ Suitable sterilization (bag breaking rate): Using the laminates of Examples and Comparative Examples, caliber 65 mmφ, height 25 mm, capacity 70 cc
The round-shaped container was prepared by vacuum forming. 9 water in the container
It was filled with 0% and was sealed by a heat seal method with a lid film having a four-layered structure of PET / aluminum foil / PET / PP and a thickness of 100 μm. After that, sterilization was performed in hot water of 130 ° C. under pressure at n = 10, and after the sterilization was completed, the presence or absence of water leakage was counted by visual inspection. The number of water leaks in the numerator and the number of tests in the denominator. -Internal pressure resistance: After evaluation of sterilization suitability, for those without water leakage after sterilization, compressed air was injected from the lid material side so as not to leak, and the pressure when the sealing was released was measured. -Opening property: A container used for proper sterilization was subjected to the same sterilization treatment, and then an opening test was conducted by a female monitor. The peelability of the release layer was poor at the time of opening, and a whisker-like thing was generated, or a thing which could not be opened smoothly was regarded as a defect. -Transparency: The internal haze was measured according to ASTM D-1003, and those having an internal haze of 10% or less were regarded as good. Moldability: Using the commercially available continuous molding machine, using the 640 mm wide laminate of Examples and Comparative Examples, 63 round containers having a diameter of 65 mmφ, a height of 25 mm and a capacity of 70 cc were molded. It was The temperature range in which a molded product having a uniform wall thickness was obtained was 15 ° C or higher, and the temperature range of less than 15 ° C was poor.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

[0018]

INDUSTRIAL APPLICABILITY The laminate of the present invention can stably control the easy-opening property and sealing property after high temperature treatment. In addition, the easy-open container obtained from this laminate has excellent sealing and opening properties, and its practical value is great.

Claims (3)

[Claims] 1. A sealing layer (A) in which the first layer is polypropylene from the inside, and the second layer is an adjacent layer (B) made of a mixture of 20 to 90% by weight of polypropylene and 80 to 10% by weight of 4-methylpentene-1 resin. An intermediate layer (C) in which the third layer is made of polypropylene having a melt index of 0.5 to 30,
The outermost layer has a base material layer (D) mainly composed of polypropylene having a melt index of 0.01 to 4 in which 0.01% by weight to 1% by weight of a nucleating material is mixed, and the melt of the seal layer (A). The index is 1.1 times or more the melt index of the intermediate layer (C), the interlayer peel strength between (A) and (B) is weaker than the interlayer peel strength between (B) and (C), and the peel strength is 0. .2 to 2.5 kg / 15 mm (pulling speed 300 m
m / min) and is composed of at least 4 layers. 2. The intermediate layer (B) is polypropylene 20-9.
2. A composition comprising 3 to 20 parts by weight of polyethylene or an unsaturated carboxylic acid-modified polypropylene added to 100 parts by weight of a mixture consisting of 0% by weight and 80 to 10% by weight of 4-methylpentene 1 resin. Stack of. 3. The laminate according to claim 1, wherein the innermost layer (A) has a thickness of 5 to 100 μm.