JP2979663B2 - Packaging film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging film used for food packaging and the like. More specifically, the present invention relates to a stretched laminated film suitable for a packaging film excellent in cutability, transparency, heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkage and food safety.

[0002]

2. Description of the Related Art Conventionally, as a wrapping film used for food packaging, a film mainly composed of polyvinylidene chloride, polyethylene or polyvinyl chloride is known.

[0003]

However, polyvinylidene chloride-based films have a disadvantage that shrinkage upon heating is large, and polyethylene-based films come in contact with oily substances (for example, meat and tempura) and have high heat. In this case, there is a disadvantage that the film is melted, and there is a problem that the polyvinyl chloride-based film causes a whitening phenomenon when brought into contact with boiling hot water. On the other hand,
Aliphatic polyamide resins are known as heat-resistant resins for packaging films. Aliphatic polyamide resin has excellent heat resistance and mechanical strength,
Due to high hygroscopicity, it is difficult to maintain the original physical properties. In particular, copolymerized nylons such as nylon-6 and nylon-6 / 6,6, nylon-6 / 6,10 and the like are used in foods from the viewpoint of food safety because ε-caprolactam, which is a monomer component thereof, bleeds to the film surface. Limited use in packaging applications.

Further, such a wrapping film has the following problems in cutability (easiness of cutting).
That is, the wrapping film is usually stored in a case such as a paper tube, and the film is cut off to an appropriate length by applying the film to a cutting blade called a “saw blade” attached to the case. is there. As a "saw blade" used for cutting a film, a simple blade which is generally only punched into a saw-shaped 0.2 mm thick iron plate is used, and also supports this "saw blade". About the case,
A paper box made of coated cardboard of about 350 to 700 g / m ² is used, and the rigidity is extremely low. This kind of film is required to be easily cut according to the user's will even with such a simple cutting mechanism, but in reality, the case and the "saw blade" are only deformed. Instead, the film may be deformed, or cutting may occur at a position outside the “saw blade”. More specifically, when a conventional polyvinylidene chloride-based film is cut at the time of cutting, if a part of the film has a tear, the tear spreads and is not cut along the “saw blade” without being cut. Tends to cut. Further, the conventional polyethylene-based film requires a considerable tensile force at the time of cutting, so that not only the case is bent but also the film may be deformed.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to produce a packaging film in which the above-mentioned problems of the conventional wrapping film have been solved. The above-mentioned problems are solved by stretching a laminate of polypropylene-based resins in the film take-off direction, and the cut properties and transparency can be achieved without impairing the inherent properties (heat resistance and mechanical strength) of the polyamide resin. The present inventors have found that a packaging film excellent in heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkage property and food safety can be obtained.

That is, the gist of the present invention is to provide at least three layers of an outer layer, an intermediate layer and an inner layer, wherein the outer layer and the inner layer are (A) 100 parts by weight of a polypropylene resin, and (B) polybutene or polyisobutylene 3 to 30 parts. Parts by weight and (C)
Monoglyceride having an acyl group having 8 to 22 carbon atoms
The intermediate layer is made of a polypropylene resin composition consisting of 2 to 5 parts by weight, and the intermediate layer is formed by stretching the laminated film made of the aliphatic polyamide resin (D) in the drawing direction of the film at a stretching ratio of 2 to 2.
It is obtained by stretching at 4.5 times, the thickness of the whole film is 40 μm or less, and the thickness of the intermediate layer is in the range of 10 to 90% of the thickness of the whole film. To be used for packaging film.

Hereinafter, the present invention will be described specifically. The stretched laminated film of the present invention is composed of at least three resin phases of an outer layer, an intermediate layer and an inner layer. The outer layer and the inner layer of the stretched laminated film are composed of (A) 100 parts by weight of a polypropylene resin, (B) 3 to 30 parts by weight of polybutene or polyisobutylene and (C) monoglyceride having an acyl group having 8 to 22 carbon atoms. It is a polypropylene resin composition comprising up to 5 parts by weight. The intermediate layer is (D) an aliphatic polyamide resin. The polypropylene resin which is the component (A) of the polypropylene resin composition is blended in a larger amount than the components (B) and (C), and is used as a base material of the composition. The polypropylene resin that can be used here may be a propylene homopolymer or a copolymer of propylene with a small amount of another copolymer component (eg, ethylene, butene, etc.). Examples of the propylene homopolymer include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene. Of these, isotactic polypropylene is preferable. Further, the copolymer of propylene and another copolymer component such as ethylene may be either a random copolymer or a block copolymer. The physical properties of the polypropylene resin as the component (A) may be appropriately selected according to various applications and conditions, but usually, the melt flow rate (MF)
R) 0.5 to 10 g / 10 min (measured at 230 ° C. under a load of 2.16 kg according to JIS K 6758) and a density of 0.89 to 0.91 g / cm ³ is preferable. Polybutene or polyisobutylene, which is the component (B) of the polypropylene resin composition, acts as a thickener and imparts excellent tackiness to the film. The blending amount of the polybutene or polyisobutylene is 3 to 30 parts by weight, preferably 5 to 20 parts by weight based on 100 parts by weight of the polypropylene resin as the component (A). If the amount is less than 3 parts by weight, sufficient tackiness will not be exhibited. If the amount exceeds 30 parts by weight, stickiness due to a large amount of bleeding will occur,
Further, heat resistance is undesirably reduced. The physical properties of the polybutene or polyisobutylene used here can be appropriately determined according to the blending amount, the type of the other components, the intended use of the composition, and the like, and there is no particular limitation. Those having a range of 400 to 3,000 are preferred.

The above-mentioned polypropylene resin composition (C)
The monoglyceride having an acyl group having 8 to 22 carbon atoms as a component increases the adhesiveness of a film when used in combination with polybutene or polyisobutylene as a component (B). The monoglyceride used in the component (C) is a compound in which one of three hydroxyl groups of glycerin is esterified with a higher fatty acid having 8 to 22 carbon atoms (hereinafter referred to as (C)
The components are simply referred to as "monoglycerides". ). The higher fatty acid may be saturated or unsaturated as long as it is a fatty acid having 8 to 22 carbon atoms. Usually, it is preferably a fatty acid having 10 to 18 carbon atoms. Specifically, for example, monolauryl glycerin, monopalmityl glycerin, monooleyl glycerin, monostearyl glycerin and the like can be mentioned. These monoglycerides may be used in combination of two or more. The amount of the monoglyceride is 0.2 to 5 parts by weight based on 100 parts by weight of the polypropylene resin as the component (A).
Parts by weight. If the amount is less than 0.2 parts by weight,
When the synergistic effect with polybutene or polyisobutylene as the component (B) does not occur, and when the amount exceeds 5 parts by weight, the film formability decreases, which is not preferable.

On the other hand, aliphatic polyamides constituting the intermediate layer of the packaging film of the present invention include nylon-6, nylon-6,6, nylon-6,10 and nylon-6.
6/6, 6 copolymer, nylon-6 / 6, 10 copolymer and the like can be exemplified. The packaging film of the present invention is obtained by first forming an unstretched laminated film in which the outer layer and the inner layer are made of the above-mentioned polypropylene resin composition and the intermediate layer is made of the above-mentioned aliphatic polyamide resin by an arbitrary laminating method. The film is formed by uniaxially stretching the film in the film take-up direction (longitudinal direction).

[0010] The production method (lamination method) of the unstretched laminated film includes a heat bonding method, an extrusion or dry lamination method,
Coextrusion and the like can be mentioned, and particularly preferred is molding by coextrusion. As the co-extrusion molding, a T-die molding method, an air-cooled or water-cooled inflation molding method is adopted, and among these, a T-die molding method or a water-cooled inflation molding method is preferable. That is, by quenching the melt-extruded resin by the above-mentioned molding method, a film having more excellent transparency can be obtained. The unstretched multilayer film obtained by the above co-extrusion molding is then uniaxially stretched in the film take-up direction (longitudinal direction) to a stretching ratio of 2 to 4.5 times, preferably 2.5 to 4 times. If the stretching ratio is less than 2 times, the cutability of the film is insufficient, and if it is more than 4.5 times, the stretchability decreases, and breakage or uneven stretching of the film is not preferred. The stretching treatment is performed by heating the unstretched film as it is or by slitting the film to a predetermined width, and stretching the film in the take-off direction, that is, the longitudinal direction by changing the peripheral speed of a stretching roll. The preheating temperature in the stretching treatment is usually [the melting point of the polypropylene-based resin −10.
° C], preferably in the range of 40 to 140 ° C.

The heat setting temperature after the stretching is preferably higher than the preheating temperature, and is preferably as high as possible in order to prevent wrinkling of the film and to improve the lateral strength. Melting point -10 ° C] or lower, preferably in the range of 80 to 150 ° C. When the preheating and heat setting temperature is higher than [the melting point of the polypropylene-based resin −10 ° C.], the film is melt-adhered to the stretching roll, and if the preheating temperature is lower than 40 ° C.,
Unsatisfactory preheating of the aliphatic polyamide resin makes stretching difficult and film breakage occurs, which is not desirable.

The thickness of the packaging film of the present invention is 4
The thickness is 0 μm or less, preferably 2 to 30 μm, more preferably 5 to 20 μm, and the thickness of the intermediate layer is 10 to 90% of the thickness of the entire film. When the thickness of the film is larger than 40 μm, the tear strength at the time of cutting the film becomes too large, which is not suitable for use as a wrap film. If the thickness of the intermediate layer is less than 10% of the total thickness, the inherent heat resistance and mechanical strength of the polyamide resin cannot be maintained, and the physical properties of the uniaxially stretched polypropylene film become dominant. It is easy to tear. The thickness of the intermediate layer is preferably at least 15% of the total thickness. On the other hand, if it is larger than 90%, the thickness of the polypropylene layer becomes small, and it becomes difficult to uniformly cover the intermediate layer by co-extrusion. The thickness of the intermediate layer is 80 of the total thickness.
% Is preferred.

The layer structure of the stretched laminated film of the present invention is essentially composed of at least three resin layers of outer layer / intermediate layer / inner layer, but other layers may be used without departing from the gist of the present invention. It is possible to add four resin layers to form a structure having four or more layers. Such a structure having four or more layers includes, for example, a structure having an adhesive layer or the like between an outer layer and an intermediate layer, or an inner layer and an intermediate layer, or a structure further provided with a resin layer outside the outer layer or inside the inner layer. Can be considered. Further, by adding an appropriate adhesive component to each layer, it is conceivable to prevent separation between the layers without providing an adhesive layer and keeping the three-layer structure.

[0014]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples unless it exceeds the gist thereof.
The measurement in the examples was performed by the following method.

(1) Moisture permeability Measured at 40 ° C. and 90% RH in accordance with JIS Z 0208. The result is expressed in g · mm / m ² · 24 hr. (2) Transparency (haze value) Measured with a haze meter according to JIS K 6714. The results are expressed in%. (3) Heat resistance temperature Upper and lower sides of a strip film sample 30 mm wide and 14 cm long
Put paper on 5mm and lower 10g weight. The maximum ambient temperature that could not be cut in one hour was measured at 10 ° C intervals.

(4) Heat Shrinkage Rate A film having a diameter of 10 mm is formed by a punching jig, immersed in an aluminum pan filled with silicone oil, and placed on a hot plate at 140 ° C. Although the temperature of the hot plate temporarily drops because heat is taken by the aluminum pan, a sample is taken out 45 seconds after the temperature reaches 140 ° C., and the size change is measured. The results are expressed in%.

(5) Cutability The film was wound around a core tube, housed in a wrap film case, subjected to a cutting test with a saw blade, and evaluated on a four-point scale (good, normal, slightly poor, poor). As a standard for evaluation, the cut level of a commercially available wrap film was evaluated as normal.

(6) Adhesive strength Two films are superimposed lightly, and 25
Pressing three times with a linear pressure of 0.3 kg / cm using a roll with a diameter of 150 mm and a roll of 150 mm in width. Was measured under the conditions shown in Table 1 with a tensile tester.

[0019]

[Table 1]

Examples 1 to 3 and Comparative Examples 1 to 7 As the polypropylene resin (A), propylene was used.
Ethylene random copolymer (MFR = 9.0, density 0.
89; manufactured by Mitsubishi Chemical Corporation, trade name: Mitsubishi Polypro 6
500J) as the component (B), polybutene (average molecular weight: 780; Nissan Polybutene 5SH, manufactured by NOF Corporation)
Using monolauryl glycerin as the component (C), the blending amounts of the respective components were adjusted to the amounts shown in Table 2 and mixed in a blender. After that, using a twin screw extruder having a diameter of 30 mm, 220
It pelletized on extrusion conditions of ° C, and manufactured a polypropylene resin composition.

Next, the above-mentioned polypropylene-based resin composition was introduced into an extruder having a diameter of 50 mm using a 450 mm wide, two-layer, three-layer coextrusion T-die molding machine, and nylon (D) was used as an aliphatic polyamide of the component (D). 6 / 6,6 copolymer (manufactured by Mitsubishi Kasei Corporation, trade name Novamid 2030; Novamit is a registered trademark) was charged into an extruder having a diameter of 40 mm in an amount shown in Table 2, and simultaneously extruded at a die temperature of 270 ° C. A film was formed under the conditions of a chill roll temperature of 250 ° C. and a take-up speed of 20 m / min, and was composed of an outer layer (polypropylene resin composition) / intermediate layer (nylon-6 / 6,6) / inner layer (polypropylene resin composition). A seed three-layer film was obtained. Then, the film was roll-stretched to have a preheating temperature of 50 ° C and a heat setting temperature of 1
The film was uniaxially stretched at 10 ° C. at a magnification shown in Table 2 to obtain a multilayer film having a film thickness of 10 μm. The moisture permeability, transparency, heat resistance temperature, heat shrinkage, cutability and adhesive strength of the obtained film were measured. Table 3 shows the results.

[0022]

[Table 2]

[0023]

[Table 3]

In Comparative Example 2, streaks occurred due to excessive addition of monoglyceride to the raw film, and a good film was not obtained. In Comparative Example 5, breakage occurred during stretching, and sampling was impossible. The physical properties of the film could not be evaluated. In addition, the cut property of Comparative Example 6 was slightly poor because the film was slightly stretched, making it difficult to cut, and the cut property poor in Comparative Example 7 was caused by longitudinal tearing.

[0025]

The packaging film of the present invention is excellent in cutability, transparency, heat resistance, adhesiveness, water vapor barrier property and non-heat shrinkage, and is a raw material monomer of nylon-6 and its copolymerized nylon. -Since bleeding of caprolactam on the film surface is suppressed by laminating a polypropylene resin, food safety is also excellent. Therefore, the present packaging film is particularly suitable for a stretch film for food packaging, a wrap film, and the like.

In terms of practicality when used as a stretch film or a wrap film, the values measured in the examples are such that the adhesive strength is a shear peel strength of 0.40.
kg / cm ² or more, preferably 180 ° C. peel strength is 4.0 g / 50 mm or less.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification code FI B29L 9:00 (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 1/00-35/00 B65D 65/00 -65/46 B29C 55/00-55/30

Claims (1)

(57) [Claims] The present invention has at least three layers, an outer layer, an intermediate layer and an inner layer, wherein the outer layer and the inner layer are (A) 100 parts by weight of a polypropylene resin, (B) 3 to 30 parts by weight of polybutene or polyisobutylene, and (C) A) a polypropylene resin composition comprising 0.2 to 5 parts by weight of a monoglyceride having an acyl group having 8 to 22 carbon atoms, wherein the intermediate layer comprises (D)
It is obtained by stretching a laminated film made of an aliphatic polyamide resin in a drawing direction of the film at a stretching ratio of 2 to 4.5 times, and has a total film thickness of 40 μm or less, and The thickness is 1 of the total thickness of the film
A packaging film having a range of 0 to 90%.