JPH07119288B2 - Method for producing easily tearable film and laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The thermoplastic film and laminate of the present invention have high heat-sealing strength, excellent mechanical strength, and are easy to tear in one direction, Alternatively, the present invention relates to a method for manufacturing a laminated body.

<Conventional technology and problems> Packaging requires basic functions such as protection of contents, easiness of handling, and transmission of product information. Recently, these basic functions have been taken as a matter of course for consumers. There is a strong demand for packaging materials to have the function of convenience in use.

From this point of view, there is a strong demand for packaging materials that are easy to open particularly in food packaging and pharmaceutical packaging, and various packaging materials and packaging forms have been developed.

In the fields of food packaging and pharmaceutical packaging, they are roughly classified into pouch packaging and easy packaging depending on the form. Pouch packaging is a bag-like packaging material that is filled with contents and then sealed. Generally, a heat-sealable thermoplastic resin phase such as polyethylene or polypropylene is laminated on a printed base film. It is formed by heat-sealing thermoplastic resins. Container packaging is, as typified by jelly and pudding containers, filled with contents in cups, trays and the like obtained by injection molding, vacuum molding, etc., and heat-sealed with a lid material having a heat-sealing layer. Among them, in container packaging, since the heat sealing layer of the lid material can be freely selected for the container material, it is relatively easy to control the heat sealing strength, so easy opening (peelable) can be provided. , Has been put to practical use in many applications.

On the other hand, in the pouch packaging, as described above, the same kind of thermoplastic resin is used to be heat-sealed, so that they are completely fused. Therefore, in order to impart peelability in pouch packaging, it is possible to use a resin layer with a low cohesive force to cause cohesive failure at the time of opening, or to reduce the resin thickness and reduce the heat seal strength from the beginning. However, these methods can be used only when the contents are lightweight, and the contents are heavy, those that move inside the package and the impact is applied to the seal part, liquids, gas-filled packages, etc. are easy to break. It cannot be used. For this reason, it is common to tear and open the pouch packaging, and in order to make it easier, a notch called a V cut is put in the heat-sealed portion of the pouch packaging to facilitate tearing. However, linear low-density polyethylene (LLDPE), which has recently been increasingly used as a heat-sealing layer for packaging materials, has higher mechanical strength (tensile strength, elongation, tear strength, etc.) than conventional low-density polyethylene (LDPE). ) Is excellent and the heat seal strength is high, so it is preferable in terms of the protective function of the contents, but it is inferior in opening ability and sometimes tearing and opening ability, and in fact it can only be opened and closed with scissors or knife, and improvement is desired. Was there.

<Means for Solving Problems> The present invention solves the problem of poor tear openability in conventional pouch packaging using LLDPE as a heat-sealing layer as described above, and is incompatible with LLDPE. When the thermoplastic resin is hot melt extruded to form a film, it is arranged in a fiber form in the film forming direction,
This has been solved by finding that the tearability of the obtained film in the film forming direction is greatly improved.

That is, the solubility coefficient with LLDPE (A) is 9.0 or more,
Polyvinyl chloride, a thermoplastic resin that is incompatible with LLDPE,
A resin (B) selected from polyethylene terephthalate, a saponified product of ethylene-vinyl acetate copolymer, nylon, and polyvinyl alcohol is blended at a ratio of A: B = 99: 1 to 80:20, and hot melt extrusion is performed to form a film. It is a method for producing a film that is easily tearable.

Furthermore, a uniaxially or biaxially stretched plastic film,
Polyvinyl chloride, polyethylene terephthalate, ethylene-acetic acid, which is a thermoplastic resin incompatible with LLDPE (A) and LLDPE with a melting coefficient of 9.0 or more, on a base film made of paper, aluminum foil, or a laminate of these. A resin (B) selected from saponified vinyl copolymer, nylon, and polyvinyl alcohol is blended at a ratio of A: B = 99: 1 to 80:20, and a thermoplastic film extruded by hot melt is laminated to facilitate tearing. It is a method for manufacturing a laminated body.

LLDPE used in the present invention is a copolymer of α-olefins such as ethylene, butene-1, 4 methyl pentene-1 and octene-1, and is produced by a medium-low pressure polymerization method, and is similar to high density polyethylene (HDPE). Has a linear molecular structure. However, its density is almost the same as that of low-density polyethylene (LDPE) due to the short chain branching by α-olefin.
It is 0.920 to 0.940 g / m ² .

The properties of LLDPE, especially the mechanical strength, depend on the α
Depending on the type of olefin, α-olefins are roughly divided into those with C ₄ and those with C _{6 to} C ₈ , and LLDPE copolymerized with C _{6 to} C ₈ α olefins has a higher tensile strength, elongation, and tearing. Since the strength is high, the film strength is excellent, but the tearing and unsealing property is inferior, and conversely the effect of the present invention is great.

Next, a thermoplastic resin that is incompatible with LLDPE used in the present invention will be described.

If the cross section of the obtained LLDPE film is observed microscopically, L
LDPE and incompatible thermoplastic resin have a sea-island structure, and LLDPE that does not have such a structure is incompatible thermoplastic resin, such as evaporation energy method, Hildepland method, method to determine from molecular structure, etc. A solubility coefficient of 9.0 or higher is recommended.

The solubility coefficient of LLDPE is about 8.0, for example, low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer or the like with a solubility coefficient 9.0 or less of a thermoplastic resin blending does not cause the expected phase separation in the present invention, The effect of improving the tearability cannot be obtained.

On the other hand, a thermoplastic resin having a solubility coefficient (SP value below) of 9.0 or more, that is, polyvinyl chloride (SP value 9.6), polyethylene terephthalate (SP value 10.7), saponified ethylene-vinyl acetate copolymer (SP value) 10.8), nylon (SP
Value 13.6), polyvinyl alcohol (SP value 23.4), etc. are LL
It is incompatible with DPE, phase-separated, and melt-extruded to form a fibrous array.

Among these thermoplastic resins that are incompatible with LLDPE, saponified ethylene-vinyl acetate copolymer with an ethylene content of 5 to 25% and a saponification degree of 70 to 90%, and a saponification degree of 70 to 90%, average Polyvinyl alcohol having a degree of polymerization of 500 to 1000 formed a particularly preferable fibrous arrangement and was excellent in tearability.

In the present invention, in order to improve the tearability of LLDPE, and not to impair the heat sealability and film forming processability in practical use, LLDPE
The compounding incompatibility of (A) and the thermoplastic resin (B) incompatible with LLDPE is set to A: B = 99: 1 to 80:20, preferably A: B.
= 99: 1 to 90:10. When the compounding ratio of LLDPE and the incompatible thermoplastic resin is 1% or less, the effect of improving tearability is low, and when it is 20% or more, the high heat seal strength and hot heat sealability (hot tack) inherent to LLDPE are obtained. In addition, streak-like thickness unevenness occurs in extrusion film formation, and stable film formation becomes difficult.

The method for producing a tearable thermoplastic film of the present invention is
The T-die extrusion film-forming method or the inflation extrusion film-forming method can be used similarly to the production of a general thermoplastic film.
That is, the mixture of LLDPE and LLDPE and incompatible thermoplastic resin is supplied to the extruder, by melt-kneading in the extruder, in LLDPE, the incompatible thermoplastic resin is dispersed, the film from the slit. A film is obtained by extruding into a strip and cooling. In this case, widening the slit spacing at which the resin is extruded increases the stretching effect in the molten state from being extruded until it is cooled and solidified, and the thermoplastic resin that is incompatible with LLDPE is arranged in the extrusion film-forming direction. This is the preferred method in the present invention because it is easy to do.

<Function> As described above, when the thermoplastic resin that is incompatible with LLDPE is formed in a fibrous shape in the film-forming direction during hot melt extrusion film formation, tearing in that direction becomes easy. That is, the obtained LLDPE
Microscopically observing the cross section of the film, LLDPE and the incompatible thermoplastic resin have a sea-island structure.

The present invention will be described below with reference to examples.

<Example-1> Ultzex 2 manufactured by Mitsui Petrochemical Industry Co., Ltd. as LLDPE
080C (density 0.920, melt flow rate 7g / 10min), LLDP
As a thermoplastic resin incompatible with E, ethylene content 15
%, Saponification degree of ethylene-vinyl acetate copolymer (EVOH) having a saponification degree of 80% and T
Five types of thermoplastic films having a thickness of 50 μm were obtained by the die extrusion film forming method.

Elmendorf tear strength of the resulting thermoplastic film,
The heat seal strength and the film forming processability were evaluated and the results shown in Table 1 were obtained.

From the results shown in Table-1, the obtained film was easy to tear in the film forming flow direction in proportion to the blending amount of the incompatible ethylene vinyl acetate copolymer with LLDPE, and in the Elmendorf tear strength measurement, the horizontal direction was measured. It is clear that the strength of the is reduced. In addition, the heat seal strength and extrusion film forming processability when blended with a saponified ethylene vinyl acetate copolymer that is incompatible with LLDPE in this way, the original performance of LLDPE is practically used when the blending amount is 10% or less. It did not lower. When 20% was added, the heat seal strength was lowered and some uneven thickness was observed during the film forming process, which is considered to be the limit compounding ratio. Further, when 30% was blended, stable film forming process was difficult, and the heat seal strength was greatly reduced, so that it could not be used.

<Example-2> As in Example-1, as LLDPE, Mitsui Petrochemical Industry Co., Ltd. Ultzex 2080C, as a thermoplastic resin incompatible with LLDPE, nylon 66 (manufactured by Ube Industries, Ltd., 2020
B) was blended at a blending ratio of LLDPE / nylon 66 = 90/10, and a film having a thickness of 40 μ was obtained by a T-die extrusion film forming method. Also, a 40 μ LLDPE film was obtained by the same method. After subjecting one side of these films to corona discharge treatment, they were dry-laminated with a biaxially stretched polyester film (Lumirror P-11, 12μ manufactured by Toray Industries, Inc.) using a two-component reactive urethane adhesive to obtain a laminate. It was The Elmendorf tear strength and heat seal strength of these two types of laminates were measured and shown in the table.
The results are shown in 2.

Further, the obtained two kinds of laminates were heat-sealed into bags, and a V-cut was put in a part of the sealed portion. When the tear-opening property was evaluated, it was difficult to open the LLDPE because the LLDPE did not tear and stretched even in the tear from the V-cut portion in the laminate using the LLDPE alone as the heat-sealing layer. On the other hand, in the case of using LLDPE / nylon 66 as the heat-sealing layer, when tearing in the direction perpendicular to the film-forming direction, tearing from the V-cut part is the same as when using LLDPE alone. However, it was difficult to open the film, but when tearing parallel to the film-forming direction during film-forming, it could be easily torn by hand even without V-cut.

<Example-3> Stamilex 1046 manufactured by Idemitsu Petrochemical Co., Ltd. as LLDPE
(Density 0.925, melt flow rate 4g / 10 minutes), polyvinyl alcohol with a saponification degree of 78.5 to 81.5 mol% and an average degree of polymerization of 600 as a thermoplastic resin incompatible with LLDPE (Nippon Gosei Kagaku Co., Ltd., Gohsenol) KL-05) (PVA) with the compounding ratios shown in Table-3, by T-die extrusion film forming method.
After preparing a thermoplastic film of 30μ, a uniaxially stretched polypropylene film (20μ) /
A base film made of aluminum foil (9μ) was dry laminated to obtain a laminate. The Elmendorf tear strength and heat seal strength of these laminates were measured and are shown in Table 3.

When polyvinyl alcohol is used as a thermoplastic resin that is incompatible with LLDPE, the effect of improving the tearability is large even in a condition where the blending amount is small, and when a uniaxially stretched film that is easy to tear in the film-forming direction is used as the base film, Due to the effect, the tear-opening property is further improved.

<Effects of the Invention> (1) According to the present invention, it is possible to impart unidirectional tearability to LLDPE, which was conventionally considered to have large mechanical strength and poor tearability, and when used for pouch packaging. Can greatly improve the tearing and opening properties and enhance the functionality of the packaging material.

(2) Since the film and the laminate obtained by the present invention substantially retain the mechanical strength and the heat sealability other than the tearability, the protective function is not deteriorated when used as a packaging material.

(3) The film and the laminate of the present invention can be easily formed by a film structure device which has been generally used in the past, so that the cost and the application range are wide.

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Claims (2)

[Claims] 1. A thermoplastic resin having a solubility coefficient of 9.0 or more with linear low-density polyethylene (A) and incompatible with linear low-density polyethylene, such as polyvinyl chloride, polyethylene terephthalate, and ethylene-vinyl acetate. A resin (B) selected from saponified copolymer, nylon and polyvinyl alcohol is blended at a ratio of A: B = 99: 1 to 80:20, and hot melt extruded to form a film which is easy to tear. Manufacturing method. 2. A uniaxially or biaxially stretched plastic film,
Linear low-density polyethylene (A) and solubility coefficient on a base film made of paper, aluminum foil, or a laminate of these.
A resin (B) selected from polyvinyl chloride, polyethylene terephthalate, saponified ethylene-vinyl acetate copolymer, nylon, polyvinyl alcohol, which is a thermoplastic resin incompatible with linear low-density polyethylene of 9.0 or more :
A method for producing a laminate which is easy to tear, characterized in that the thermoplastic film is blended in a proportion of B = 99: 1 to 80:20 and is extruded by hot melt.