JPH0647878A - Easy peel multilayered film for polyethylenic packing material - Google Patents

Abstract

PURPOSE:To improve heat sealability, to enhance easy opening properties under a wide sealing condition and to obtain heat resistance, transparency, slip properties at the time of secondary processing and rigidity by constituting a multilayered laminate of a seal layer composed of an olefinic homopolymer or copolymer, an intermediate layer and an outer layer. CONSTITUTION:An ethylene homopolymer or an ethylene/alpha-olefin or vinyl monomer copolymer is used as a seal layer A and, as the crystalline propylene random copolymer used in an intermediate layer B, a propylene/ethylene or other alpha-olefin copolymer is used. The compsn. of the intermediate layer B consists of 20-80wt.% of a crystalline propylene random copolymer and 80-20wt.% of an ethylenic polymer and/or ethylene/alpha-olefin copolymer rubber. In an outer layer C, one same to the polyethylene or ethylene copolymer of the seal layer A is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-based multi-layer film, and particularly when the object to be heat-sealed is a polyethylene-based lid material or container, excellent sealing property and excellent easy-opening property. The present invention relates to an easy-peel multi-layer film for polyethylene-based packaging materials, which is capable of imparting (easy peel property) at the same time and is excellent in various physical properties and moldability as a film.

[0002]

2. Description of the Related Art As a performance required for a package, it is necessary to protect the contents in the manufacturing and distribution processes and to easily take out the contents during use. That is, it is required to have both contradictory functions of sealing property and easy opening property. Conventionally, a relatively flexible ethylene copolymer such as ethylene-vinyl acetate copolymer (EVA) or ethylene-ethyl acrylate copolymer (EEA) has been used as a means for imparting easy-opening property to a polyethylene-based packaging material by heat sealing. ), Ethylene-butene copolymer rubber (EBR), ethylene-propylene copolymer rubber (EPR) and other hot melt adhesives are laminated on the sealing side of the container or lid by a method such as coating, laminating and co-pressing. It is generally known to be used. However, such a packaging material develops easy-opening property by putting the above-mentioned resins in a semi-fused state at the time of heat sealing, but it is difficult to control this fused state, and delicate heat sealing conditions are required. The heat seal strength fluctuates greatly due to the difference in If the seal strength is set to a level that is low enough to be easily opened by human hands, the rate of defective seals will increase, and there is the disadvantage that the easy-open property must be sacrificed and the seal strength must be set to a high level. In addition, there are hot-melt adhesives that do not have a strong affinity with polyethylene to improve the easy-open property, but the seal strength, transparency, and slip properties are insufficient. In addition, it causes deterioration of appearance due to the fluffing of
It has a low heat resistance and is not suitable for food packaging that requires boil sterilization. In order to improve the easy-open property of a polyolefin wrapping material, a packaging material using a blended product of polyolefin as a seal layer has been developed. For example, a method for producing an easy peel film by coextruding a resin layer obtained by blending an olefin resin and a different resin capable of easy peeling and a processability improving resin has been proposed (JP-A-57-131556). However, the conventional packaging materials are not necessarily satisfactory in that they have both sealing heat resistance capable of boil sterilization treatment and easy peeling property at the peeling interface, although the easy opening property is improved.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention According to the present invention, a perfect seal can be obtained by heat sealing, and at the same time, a seal strength that can be easily opened by hand is stably shown under a wide range of sealing conditions. Aiming to provide a film that can impart excellent easy-opening properties to polyethylene-based lid materials or containers, and further, heat resistance such that boil sterilization can be performed after sealing, and excellent transparency. The object of the present invention is to provide a film having excellent moldability, which has slipperiness and rigidity suitable for handling during secondary processing such as transport and winding.

[0004]

The present invention is directed to (A) a sealing layer made of polyethylene and / or an ethylene copolymer,
(B) Crystalline propylene random copolymer 20 to 80% by weight and ethylene polymer (excluding ethylene-α-olefin copolymer rubber) and / or ethylene-α-olefin copolymer rubber 80 to 20% by weight (however, And polyethylene-α-olefin copolymer rubber does not exceed 50% by weight), and a polyethylene-based package comprising a multi-layer structure comprising an intermediate layer composed of (C) and an outer layer composed of (C) polyethylene or polypropylene. Easy peelable multi-layer film for materials, a sealing layer comprising (A) polyethylene and / or ethylene copolymer, (B) 20 to 80% by weight of a crystalline propylene random copolymer and an ethylene polymer (however, ethylene- α-olefin copolymer rubber) and / or ethylene-α-olefin copolymer rubber 80 To 20% by weight (however, the ethylene-α-olefin copolymer rubber does not exceed 30% by weight) and a multilayer structure comprising a layer composed of a composition. It exists in the film.

Each layer of the film obtained by the above constitution of the present invention has (B) at each interface of the seal layer (A) -intermediate layer (B) and the intermediate layer (B) -outer layer (C).
Crystalline propylene random copolymer (RPP) in layer
Part, the polyethylene resin and / or the ethylene-α-olefin copolymer rubber (PE) part is partially adhered, so when a force for peeling off each layer is exerted, peeling occurs between any of the layers, Moreover, the force required therefor is determined by the adhesive force between layers, that is, the composition of the (B) layer. When this is used as a PE-based packaging material, the (A) layer can be completely fused with the sealing partner (PE), so the packaging material is completely sealed by heat sealing, but when opened, the film is used. Since it peels between the inner layers, it opens with a constant force, and by controlling this with the composition of the (B) layer, it is possible to obtain a stable easy-open property regardless of the sealing conditions. Moreover, since the layer that peels and remains on the other side is very thin, it does not break at the boundary line of the seal portion and cause no fuzz. Furthermore, the present invention uses polyethylene (PE) or polypropylene (PP) as the outer layer.
By making it relatively thick, the transparency and rigidity are excellent, and by using an appropriate polyethylene and / or ethylene copolymer (PE) for the seal layer, it is excellent in transparency and slip properties, and it is boiled and sterilized. It is characterized by having possible heat resistance. In particular, the structure in which the (B) intermediate layer PP / PE mixed layer, which has a very poor transparency alone, is sandwiched between the (A) seal layer and the (C) outer layer single layer is very transparent. It is important that the transparency of this film is PE or P
Compared to P single film. In addition, the moldability of the film, the secondary processability such as printing and lamination, and the handling of the container and the lid material using the same are as good as those of the normal unstretched PP film.

Examples of polyethylene and ethylene copolymers for the seal layer (A) of the multi-layer film in the present invention include ethylene homopolymers and copolymers of ethylene with α-olefin and vinyl monomers. These can be used alone or in combination of two or more. The density of these polyethylenes or ethylene copolymers is preferably 0.9
1 to 0.97 g / cm ³ , more preferably 0.91 to
0.94 g / cm ³ , melt index (JIS K
7210, load 2.16 kg, 190 ° C., hereinafter referred to as MI) is preferably 0.1 to 50 g / 10 minutes, more preferably 3 to 10 g to 10 minutes. Among these polyethylenes or ethylene copolymers, low density polyethylene (LDPE), linear low density polyethylene (LLDP)
E), medium / high density polyethylene (MDPE, HDP)
E), ethylene-vinyl acetate copolymer (EVA) and the like are preferable. LDPE or EV when low temperature sealability is required
The use of A is preferred. In this case, in order to further improve the low temperature sealability to the extent that no fluffing occurs, LD
PE or EVA may be further blended with an ethylene-butene copolymer (EBR). Blending with polypropylene (either homo PP or random PP) can suppress the occurrence of fluff, but it is necessary to keep the amount of the fluff (to about 20%) so as not to impair the transparency.

Examples of the crystalline propylene random copolymer used to form the intermediate layer (B) of the multilayer film in the present invention include propylene and ethylene or other α-olefins such as 1-butene, 1-pentene, and 1-butene.
-Hexene, 4-methyl-1-pentene, 1-octene and the like copolymers. Of these, a crystalline propylene-ethylene random copolymer is preferable. These copolymers have a melt flow rate (JIS K7210, load 2.16 kg, 2
30 ° C, hereinafter referred to as MFR) is preferably 0.3 to 60
g / 10 minutes, more preferably 5 to 15 g / 10 minutes. As the ethylene-based polymer, the same polyethylene or ethylene copolymer (excluding ethylene-α-olefin copolymer rubber) as the above-mentioned seal layer (A) can be used. Further, ethylene-α-olefin copolymer rubber includes ethylene, propylene,
1-butene, 1-hexene, 4-methyl-1-pentene and other copolymer rubbers with one or more monoolefins (typically ethylene-propylene copolymer rubbers and ethylene-1-butene copolymer rubbers). The above monoolefin and dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene,
Copolymer rubbers with non-conjugated diolephins such as ethylidene norbornene are also included. The Mooney viscosity of the above copolymer rubber is preferably ML _{1 + 8 at} 127 ° C., 5 to 300, and the ethylene or propylene content is 35 to 85% by weight.
The composition ratio of the composition constituting the intermediate layer (B) is such that the crystalline propylene random copolymer is 20 to 80% by weight, the ethylene-based polymer (excluding ethylene-α-olefin copolymer rubber) and / or ethylene- The amount of the α-olefin copolymer rubber is 80 to 20% by weight (however, the ethylene-α-olefin copolymer rubber does not exceed 50% by weight).
A preferred compounding example is 30 to 70% by weight of a crystalline propylene random copolymer, 70 to 30% by weight of an ethylene polymer, and an ethylene-α-olefin copolymer rubber (particularly E
BR) 0 to 40% by weight. If the amount of the crystalline propylene random copolymer exceeds 80% by weight, the ease of opening as a packaging material becomes large, but the sealing property is deteriorated, which is not preferable. Further, when the amount of the ethylene polymer and / or the ethylene-α-olefin copolymer rubber exceeds 80% by weight, especially when the outer layer (C) is polyethylene, the sealing property as a packaging material is good, but the easy-opening property is easy. Is reduced. On the other hand, when the outer layer (C) is polypropylene, the packaging material has good openability, but the sealing property is deteriorated.
Further, when the ethylene-α-olefin copolymer rubber exceeds 50% by weight, the heat resistance is lowered, which is not preferable. In the present invention, the blending of the ethylene-α-olefin copolymer rubber having an affinity for both the crystalline propylene random copolymer and the ethylene-based polymer is useful for ensuring high seal strength. A multilayer film using such a composition as an intermediate layer is easy to delaminate when used as a packaging material, and has a smooth peeling surface, and the delamination strength can be adjusted by adjusting the blending ratio. it can.

Outer layer (C) of the multilayer film according to the present invention
As the polyethylene used for constituting the above, the same polyethylene or ethylene copolymer as the above-mentioned seal layer (A) can be used. The polypropylene may be random PP as exemplified above,
Isotactic propylene homopolymer with MFR
Is preferably 0.3 to 60 g / 10 min of homopolypropylene. The homopolypropylene layer (C) has high rigidity and enables thin molding of the intermediate layer and the seal layer when used as an outer layer of the multilayer film, and also allows the multilayer film to have an appropriate rigidity.

In the present invention, the outer layer (C) is omitted,
(A) A seal layer made of polyethylene and / or ethylene copolymer, (B) 20 to 80% by weight of a crystalline propylene random copolymer, 80 to 20% by weight of an ethylene polymer and / or ethylene-α-olefin copolymer rubber. %, And may have a multilayer structure with a layer made of a composition of However, the ethylene-α-olefin copolymer rubber does not exceed 30% by weight. Such (A) layer and (B)
When it is composed of layers, the high-density polyethylene or linear low-density polyethylene is preferable as the ethylene polymer of the layer (B).

In the method for producing a multilayer film of the present invention, if a film having the above-mentioned structure is finally obtained,
The molding method may be any known one, but in order to make the best use of the features of the present invention, a well-known method for molding a multilayer film, such as a coextrusion T-die method or a coextrusion water-cooled inflation method, A molding method having excellent physical property balance (transparency, rigidity, etc.) and film thickness uniformity is preferable.

The thickness of the multilayer film of the present invention is not particularly limited, but the intermediate layer (B) comprising the composition has a thickness of 2 to 10.
It is preferably set to μ. Further, it is preferable that the sealing layer (A) also has the same thickness of 2 to 10 μm. Furthermore, the outer layer (C)
The thickness is preferably relatively thicker than these, and is 10 μm or more, preferably 15 to 40 μm. By adjusting the thickness ratio of each layer of the multilayer film, the peel strength, transparency, waist strength and the like can be adjusted.

The multi-layer film of the present invention can be used alone, but it may be used by laminating it with another plastic film or a metal foil. Any layer or all layers constituting the above-mentioned multilayer film, if necessary, known additives, for example, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents,
Anti-fog agents, anti-blocking agents, lubricants, the agents, pigments, dyes and the like can be added.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples. Na
The% in the examples is based on weight, and the test method is as follows.
It is Ri. (1) Haze (%): ASTM D1003 (however,
It is the value of the multilayer film before dry laminating described below. ) (2) Dynamic friction coefficient; ASTM D1003 (Seal surface
It is the value of each other. ) (3) 1% tensile modulus (kgf / cm² ); ASTM
D1003 (However, the multilayer film before dry lamination described below
It is the value of the film. ) (4) Heat resistance: Seal layer of multi-layer film is LDPE container
Boiled (90 ° C hot water)
Heat for 30 minutes), leakage of contents, low peel strength
Below, it was observed whether or not the peeling appearance deteriorated. O is good, △ is
Slightly good, X shows bad. (5) Appearance of peeling interface: Bristles at the interface after the above peel strength measurement
The appearance such as feathers was observed. O indicates good, △ indicates slightly good
You (6) Peel strength of heat-sealed area: Multi-layer film seal
200μ LDPE sheet on the layer side at a predetermined temperature, surface pressure
Force 2.0 kg / cm² Heat seal for 1.5 seconds at
Cut a 15 mm wide test piece from the laminated material and pull it
The speed (peeling speed) is 500 mm / min and the heat-sealed part is 9
0 The strength is shown when peeled at an angle of degrees. In addition, good
The heat-seal strength, which indicates easy peeling, is usually 100.
0g / 15mm or less, with this value as a reference
The heat seal strength obtained above is plotted in FIG.
Evaluate the stability of seal strength from the heat seal curve
did. O is good, Δ is slightly good, and X is bad.

Example 1 As the sealing layer A of the multilayer film, low density polyethylene LDPE (density = 0.923 g / cm ³ , MI = 6.0) was used.
g / 10 minutes, hereinafter referred to as LDPE), and as the intermediate layer B, the LDPE and the crystalline propylene-ethylene random copolymer (ethylene content 3.6%, MFR = 9.
0 g / 10 minutes, hereinafter referred to as PP random) at a ratio shown in Table 1, was further used as an outer layer C for homopolypropylene (MFR = 9.0 g / 10 minutes, hereinafter referred to as homo P
P) was supplied to a black box type co-extrusion device of the T-die method and co-extruded at a temperature of 240 ° C. to obtain a three-layer film of each thickness as shown in Table 1.
Each of the obtained three-layer films was dry-laminated with a 30 μ stretched polypropylene film (OPP) by a dry laminating (hereinafter simply referred to as dry laminating) method, and the results were evaluated. The results are shown in Table 1. Also, in FIG.
The measurement results of the heat seal (H / S) temperature and the H / S strength are shown in a graph. As is clear from the results in Table 1 and FIG. 1, the haze value is small, the transparency is excellent, the dynamic friction coefficient is small, the slip is good, the value of the 1% tensile elastic modulus is large, the rigidity is excellent, and it is easily peeled by hand. The possible sealing strength was obtained at a wide sealing temperature, the peeling interface was clean, and the heat resistance was good.

Example 2 The intermediate layer B of the multilayer film was replaced by L
DPE, PP random, ethylene-butene-1 copolymer rubber (ethylene content 3.6%, MFR = 9.0 g
/ 10 minutes, hereinafter referred to as EBR) was mixed in the proportions shown in Table 1 to obtain a multilayer film or a dry lami film in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1 and FIG. As is clear from the results shown in Table 1 and FIG. 1, the same good results as in Example 1 were obtained, and the addition of EBR was a heat seal strength of 100 showing good easy peeling.
It can be seen that the sealing strength can be further improved at 0 g / 15 mm or less.

In Examples 3 and 1, high density polyethylene (density: 0.95) was used instead of LDPE of the intermediate layer B.
5 g / cm ³ , MI; 12 g / 10 min, hereinafter referred to as HDPE), except that a two-layer film having no outer layer C was used, a multilayer film was obtained in the same manner, and the evaluation was conducted in the same manner. 1 and FIG.

Multilayer films were obtained in the same manner as in Examples 4 and 3 except that EBR was added to the intermediate layer B.
Evaluation was performed in the same manner, and the results are shown in Table 1 and FIG.

Comparative Example 1 The OPP film (30 μm thick) used in Example 1 above was
About 20μ thick LDPE coating,
Evaluation was performed in the same manner as in Example 1, and the results are shown in Table 1 and FIG.

Comparative Example 2 In Comparative Example 1, the LDPE coating was replaced by an ethylene-vinyl acetate copolymer (ethylene content 3.6).
%, MFR = 9.0 g / 10 min, hereinafter referred to as EVA) was coated in the same manner as in Comparative Example 1 except that the coating was performed in a thickness of 20 μm. The results are shown in Table 1 and FIG.

Comparative Example 3 Evaluation was made in the same manner as in Example 1 except that the multilayer film (30 μm thick) of LDPE 60% and butene-140% was used, and the results are shown in Table 1 and FIG. It was As is clear from the results shown in Table 1 and FIG. 1, the comparative product has a large haze value, has a problem with transparency, and may have a problem with slip property. There were problems with heat resistance, sealing property, easy opening property, and peeling interface.

[0021]

[Table 1]

[0022]

As described above, according to the present invention, excellent sealing can be achieved by heat sealing, and at the same time, a sealing strength that can be easily opened by hand is stably exhibited under a wide range of sealing conditions. Openability can be obtained, and further, heat resistance such that boil sterilization can be performed after sealing, excellent transparency, and slip property suitable for handling during secondary processing such as transportation and winding. It was possible to obtain a film having both rigidity and excellent moldability.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the present invention.

[Explanation of symbols]

 1 Comparative Example 1 2 Comparative Example 2 3 Examples 2, 4 4 Comparative Example 3 5 Examples 1, 3 Numerical values other than the above indicate numerical values.

Claims (2)

[Claims] 1. A sealing layer comprising (A) a polyethylene and / or an ethylene copolymer, (B) 20 to 80% by weight of a crystalline propylene random copolymer and an ethylene polymer (however, an ethylene-α-olefin copolymer. (Excluding rubber) and / or ethylene-α-olefin copolymer rubber 80 to
20% by weight (however, ethylene-α-olefin copolymer rubber 50 does not exceed 50% by weight), and a multilayer structure comprising an intermediate layer made of a composition and (C) an outer layer made of polyethylene or polypropylene. Easy peel multi-layer film for polyethylene packaging materials. 2. A sealing layer comprising (A) a polyethylene and / or an ethylene copolymer, (B) 20 to 80% by weight of a crystalline propylene random copolymer, and an ethylene-based polymer (however, an ethylene-α-olefin copolymer. (Excluding rubber) and / or ethylene-α-olefin copolymer rubber 80 to
20% by weight (however, ethylene-α-olefin copolymer rubber does not exceed 30% by weight) and a multilayer structure with a layer composed of a composition, and an easy peelable multilayer film for polyethylene packaging material. .