JPH0911420A - Laminated body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give heat resistance and oil resistance to the laminated body by a structure wherein the melt index, degree of crystallinity and thickness of a sealing layer are set to be specified values and, at the same time, the specified relationship are present between them and, further, the ply separation strength between the sealing layer and the adjacent layer is set to be specified in a laminated body having four or more layers or made respectively of a specified sealing layer, an adjacent layer, an intermediate layer and a base material layer from inside in the order named. 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 and a polypropylene base material layer as the outermost layer. The melt index (a) (g/10min) of the sealing layer is set to be 0.3-30, its degree of crystallinity (b) (%) is set to be 30-70 and its thickness (t) (μm) is set to be 3-100 and these are set to satisfy the formula: t=(0.03-0.10)×a×(b-20). Further, the separation strength between the sealing layer and the adjacent layer is set to be 0.2-2.5kg/15 min under the pulling speed of 300mm/min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging field, in particular, a laminated body which is preferably used in the production of containers, and a low temperature sealing property and a sealing property for accommodating and packaging foods, chemicals and the like produced using the same. , An easily openable container having excellent openability.

[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.

[0003]

An object of the present invention is to provide a laminate which is suitable for use in the production of an easily openable container having a heat seal layer and an opening / peeling layer separately, and which has a low temperature seal of 180 ° C. or lower. The object of the present invention is to provide a laminate having heat resistance and oil resistance, which is possible and ensures the easy peeling property of the unsealing peeling layer.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a laminate used for manufacturing an easily-openable container has a specific layer structure. It has been found that the above problems can be solved by specifying the relationship between the thickness of the resin layer constituting the inner layer and its melt index and crystallinity, and the present invention has been completed based on this finding. That is, according to the present invention, 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. At least 4 having an intermediate layer (C) in which the third layer is made of polypropylene and a base material layer (D) in which the outermost layer is made of polypropylene
In a laminate of more than one layer, the melt index a (g / 10 minutes) of the polypropylene resin of the seal layer (A) is 0.
3 to 30, crystallinity b (%) is 30 to 70, thickness t (μ
m) is 3 to 100, and t = (0.03 to 0.10) ×
Lamination characterized by ax (b-20) and an interlaminar peel strength between (A) and (B) of 0.2 to 2.5 kg / 15 mm (pulling speed 300 mm / min). A seal layer (A) in which the first layer is polypropylene from the inside, and the second layer is a mixture of 20 to 90% by weight of polypropylene and 80 to 10% by weight of 4-methylpentene 1 resin.
Adjacent layer (B) made of a composition obtained by adding 3 to 20 parts by weight of polyethylene or unsaturated carboxylic acid-modified polypropylene to 0 part by weight, an intermediate layer (C) in which the third layer is made of polypropylene, and an outermost layer. In a laminate of at least 4 layers having a base layer (D) made of polypropylene, the melt index a (g / 10 min) of the polypropylene resin of the seal layer (A) is 0.3 to 30, and the crystallinity is b
(%) Is 30 to 70, thickness t (μm) is 3 to 100, and t = (0.03 to 0.10) × a × (b-20), and (A) and (B) Peel strength between layers is 0.2
~ 2.5kg / 15mm (Pulling speed 300mm /
Min) is a laminated body.

The seal layer of (A) of the present invention is made of polypropylene. By using polypropylene,
A laminate having heat resistance and oil resistance can be obtained. As the polypropylene to be used, various PPs of homo, block and random can be used. It is also possible to blend 3 to 20 parts by weight of polyethylene with 100 parts by weight of polypropylene in consideration of sealing property with the lid and moldability. In addition to polyethylene, blending of a thermoplastic resin such as unsaturated carboxylic acid-modified polyolefin or ethylene vinyl acetate is also possible within a range that does not impair the heat-resistant peeling property with the intermediate layer. However, at this time, the thickness t (μm) of the seal layer (A) is 3 to 100 μm, and it is necessary that the following equation is established in relation to the melt index a and the crystallinity b. That is, t = (0.03
.About.0.10) .times.a.times. (B-20), where melt index a (g / 10 min) is 0.3 to 30, and crystallinity b.
(%) Is 30 to 70. At this time, when t is less than the numerical value in this range, the sealing property is affected, and when t is more than the numerical value in this range, the sealing property is good, but the release layer (A) cannot be cut well, It will be unsealed.

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 90 to 60% by weight as the amount of polypropylene. 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, in order to adjust the delicate delamination strength, an unsaturated carboxylic acid-modified polypropylene may be blended.
If the blending amount is too large, the peeling strength may be enhanced, and if the blending amount is too small, the interlaminar peeling strength may be lost, so 20 parts by weight or less and 3 parts by weight or more are desirable.

Polypropylene is used for the intermediate layer (C) and the base material layer (D) of the present invention for the purpose of maintaining the strength, heat resistance and moldability of the laminate.
Various polypropylenes such as random and block are used. In addition, the base material layer occupies a large proportion of the thickness of the laminate and may affect the moldability and the like. Therefore, in order to improve the moldability, any thermoplastic resin layer such as polyethylene may be blended. Is also good. In particular, when it is necessary to improve the oxygen gas barrier property of the laminate, an ethylene vinyl alcohol copolymer (EVOH) is used by being laminated on the outside of the (C) layer, and the ethylene polymerization ratio is 20 to 50.
The thing of the weight% is arbitrarily used according to the purpose. In that case, unsaturated carboxylic acid-modified polypropylene is preferred as the adhesive layer. The layer structure of the present invention uses the above resin,
It can be obtained by coextrusion or laminating. As the laminating process, any method such as extrusion laminating, coextrusion laminating, dry laminating or thermal laminating can be used. The laminate of the present invention includes PP / [PP + MP] / PP / AD / EVO
A seven-layer structure of H / AD / PP is preferable.

[0008]

The most important point of the present invention is that the adjoining layer (B) is blended with polypropylene and 4-methylpentene-1 resin, the thickness (t) of the sealing layer (A) and the PP of the sealing layer (A). The MI (a) and the crystallinity (b) have a close relationship with the easy-open property, and by limiting these to a certain range, further easier open property can be obtained. The melting point of polypropylene is usually about 150 with random PP.
℃, about 170 ℃ in homo PP. On the other hand, the melting point of 4-methylpentene 1 is about 240 ° C. By blending these, the intermediate layer has a heat resistance of 15 ° C or higher as compared with the conventional intermediate layer mainly composed of polyethylene, and the intermediate layer is high even when the temperature of the contents becomes high (for example, 140 ° C or higher) during sterilization. Does not soften and 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. 120
When the temperature exceeds 120 ° C, softening progresses rapidly, and the interlaminar peel strength between the seal layer and the intermediate layer is 1.0 to 1.5 kg / 1 at 120 ° C or lower.
Even if it had a width of 5 mm, the peel strength sharply dropped to 0 to 0.2 kg / 15 mm when it was exposed to heat of 125 ° C. even temporarily. For this reason, in sterilization at a high temperature of 125 ° C or higher, if the lid material swells even if the pressure change during sterilization is small, the seal layer and the intermediate layer are easily peeled off, and a form as a sealed container is obtained. It becomes a state where it cannot be stopped. On the other hand, according to the present invention, when the intermediate layer is used,
Even with the above high temperature treatment, the heat resistance of the intermediate layer itself is excellent, 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 blend ratio, but for example, the mixing ratio is 50 to 90 by weight of polypropylene.
In the range of 10% by weight, the interlayer adhesive strength is 0.5 to 2.5 kg /
The range of easy peel strength is 15 kg. Therefore, the peeling of the seal layer can be easily performed.

If the thickness t (μm) of the layer (A) is too large, breakage at the time of opening is impaired, and if it is too thin, the sealing property is impaired. Therefore, t is preferably in the range of 3 to 100 μm. Further, the range of t is influenced by the type of PP used for the (A) layer. In other words, the MI of PP is large and PP
If the degree of crystallinity is high, it becomes brittle and easily breaks, and PP
If the MI is low and the crystallinity of PP is low, it becomes tough and difficult to break. If it breaks easily, the hermeticity may be impaired, and the melt index a (g / 10 min) of PP of the (A) layer is 0.3 to 30, and the crystallinity b.
The (%) is preferably 30 to 70, and it is necessary to reduce the thickness within a range that does not affect easy opening. The present inventors have tested various PPs and found that the easy opening property and the sealing property can be compatible when t, a, and b have the following relationship. t = (0.03 to 0.10) × a × (b-20) The laminate of the present invention is molded and used as a container, and is sealed with a lid material, but the lid is opened by the (A) layer and the (B) layer. Made between and must be easy to open. Therefore (A)
Delamination strength between (B) is 0.2-2.5kg / 15mm
(The pulling rate is 300 mm / min), and therefore the sealing layer of the lid material and the sealing layer (A) must be firmly adhered to each other. Normally, the material of the sealing layer of the lid material is a seal. The same or the same material as the material of the layer (A) is used.

[0010]

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
In addition, Table 3 shows the constituent resins and layer thicknesses of the laminate structures of Examples and Comparative Examples, the thickness of PP of the innermost layer: t (μm), M
I: a (g / 10 min), and crystallinity: b (%), and Table 2 and Table 4 were prepared using the laminate strength of the laminates of Examples and Comparative Examples before and after heating, using each laminate. Shows proper sterilization of containers, resistance to internal pressure, 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: 3.0-PP2: polypropylene (homo) MI: 1.5-PP3: polypropylene (homo) MI: 0.5-AD: carboxylic anhydride modified polypropylene-EVOH: ethylene vinyl alcohol Copolymer-MP: 4-methylpentene 1-HDPE: High-density polyethylene

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) of the laminate is measured. Pulling speed 300 mm / min. (Peeling by 180 degrees) -Laminate 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) of the laminate is measured. 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: The container used for 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.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

[0017]

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 (2)

[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. In the laminate of at least four layers having a middle layer (C) in which the third layer is made of polypropylene and a base material layer (D) in which the outermost layer is made of polypropylene, the melt index a of the polypropylene resin of the seal layer (A) is (G / 10 minutes) is 0.3 to 30, crystallinity b
(%) Is 30 to 70, thickness t (μm) is 3 to 100, and t = (0.03 to 0.10) × a × (b-20), and (A) and (B) Peel strength between layers is 0.2
~ 2.5kg / 15mm (Pulling speed 300mm /
Min)). 2. A sealing layer (A) in which the first layer is polypropylene from the inside, and the second layer is polyethylene based on 100 parts by weight of a mixture of 20 to 90% by weight of polypropylene and 80 to 10% by weight of 4-methylpentene-1 resin. Alternatively, an adjacent layer (B) made of a composition obtained by adding 3 to 20 parts by weight of an unsaturated carboxylic acid-modified polypropylene, an intermediate layer (C) made of polypropylene as the third layer, and a base material layer made of polypropylene as the outermost layer. In the laminate having at least four layers having (D), the melt index a (g / 10 min) of the polypropylene resin of the seal layer (A) is 0.3 to 30, and the crystallinity b (%) is 30 to 30. 70, thickness t (μm) is 3 to 100
, And t = (0.03 to 0.10) × a × (b−20), and the delamination strength between (A) and (B) is 0.2 to 2.5 kg / 15 mm (tensile strength). Speed 300m
m / min).