JPH081880A - Laminated film - Google Patents

Abstract

(57) [Summary] [Problem] To provide a laminated film suitable for use as an adhesive packaging film excellent in cuttability, transparency, heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkability and the like. [Structure] Inner / outer layer is polypropylene resin, middle layer is 4
-A laminated film made of methyl-pentene resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film useful as a packaging film for food packaging and the like. Specifically, a laminate suitable for use as a packaging film excellent in cuttability, transparency, heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkage, food safety, and less generation of toxic gas during incineration. Regarding film.

[0002]

2. Description of the Related Art Heretofore, as a wrapping film used for packaging foods, a film containing polyvinylidene chloride, polyethylene or polyvinyl chloride as a main raw material has been known. Since these wrap films are often used for heating foods etc. in a microwave oven, it is of course that the adhesiveness is good, but shrinkage, melting, discoloration, etc. do not occur at high temperatures, that is, heat resistance. Is required to be excellent.

[0003]

However, the polyvinylidene chloride-based film has a disadvantage that it shrinks greatly when heated, and the polyethylene-based film is in contact with oily substances (for example, meat and tempura) and has high heat. In the case of the above, there is a drawback that the film is melted, and the polyvinyl chloride film has a problem that a whitening phenomenon occurs when it comes into contact with boiling hot water.

Further, such a wrapping film has the following problems in cuttability (easiness of cutting).
That is, the wrapping film is usually stored in a case such as a paper tube, and it is cut into an appropriate length by applying it to a cutting blade called a "saw blade" attached to the case. is there. As the "saw blade" used to cut the film, generally, a simple blade made by punching a 0.2 mm thick iron plate into a saw shape is used, and also supports this "saw blade". As for the case,
A paper box made of coated cardboard with a weight of about 350 to 700 g / m ² is used, and its rigidity is extremely low.

This type of film is required to be easily cut according to the intention of the user even by such a simple cutting mechanism, but in reality, the case and the "saw blade" are deformed. In addition to deformation, the film may be deformed or cutting may occur at a position outside the “saw blade”. More specifically, the conventional polyvinylidene chloride film has a tear in a part of the film at the time of cutting, and the tear spreads and is not cut along the "saw blade". It tends to be cut off. In addition, the conventional polyethylene-based film requires a considerable tensile force at the time of cutting, so that not only the case may be bent but the film may be deformed.
It is also desired from the environmental point of view that the generation of toxic gas is small during incineration after use and disposal.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors to produce a packaging film in which the above-mentioned problems of conventional wrapping films have been solved, both sides of 4-methyl-pentene resin have been investigated. By co-extruding a laminate of a polypropylene resin composition having a specific composition, the above-mentioned problems are solved, and the original properties (heat resistance and mechanical strength) of 4-methyl-pentene resin are not impaired. The present invention has been accomplished by finding that a packaging film excellent in cuttability, transparency, heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkage and food safety can be obtained.

That is, the gist of the present invention is that it has at least three layers of an outer layer, an intermediate layer, and an inner layer, the outer layer and the inner layer are made of polypropylene resin, and the intermediate layer is made of 4-methyl-pentene resin. Exists in the laminated film. The specific structure of the packaging film is as follows: 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 polypropylene resin, (B).
3 to 30 parts by weight of polybutene or polyisobutylene,
(C) 0.2 to 5 parts by weight of polyglycerin fatty acid ester and (D) acyl group having 2 to 6 carbon atoms and 8 to 2 carbon atoms
2. A laminated film composed of a polypropylene resin composition consisting of 0.2 to 5 parts by weight of an glyceride having an acyl group of 2 and the intermediate layer consisting of 4-methyl-pentene resin is formed in the longitudinal direction of the film only or in the longitudinal direction. A stretched film obtained by stretching in the transverse direction at a stretching ratio of 2 to 8 times,
The packaging film is characterized in that the thickness of the entire 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 entire film.

The present invention will be specifically described below. The laminated film of the present invention is composed of at least three resin layers of an outer layer (outer surface layer), an intermediate layer and an inner layer (inner surface layer). The outer and inner layers of the laminated film are (A) 100 parts by weight of polypropylene resin, (B) 3 to 30 parts by weight of polybutene or polyisobutylene, (C) 0.2 to 5 parts by weight of polyglycerin fatty acid ester, and (D) carbon. Number 2
A polypropylene resin composition comprising 0.2 to 5 parts by weight of a glyceride having an acyl group of 6 and an acyl group of 8 to 22 carbon atoms. The intermediate layer is 4-methyl-pentene resin.

(A) of the polypropylene resin composition
The polypropylene resin as a component is blended in a larger amount than the components (B), (C) and (D), 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 and a small amount of another copolymerization component (for example, ethylene, butene, etc.). Examples of the propylene homopolymer include isotactic polypropylene, syndiotactic polypropylene, and atactic polypropylene. Among them, isotactic polypropylene is preferable. Further, the copolymer of propylene and another copolymerization component such as ethylene may be either a random copolymer or a block copolymer. The physical properties of the polypropylene resin, which is the component (A), may be appropriately selected according to various applications and conditions, but usually the melt flow rate (MFR) is 0.5 to 2
0g / 10min (according to JIS K6758, 230
Value measured at 2.degree. C. under a load of 2.16 kg), density 0.89 to
It is preferably 0.91 g / cm ³ .

(B) of the polypropylene resin composition
The component polybutene or polyisobutylene acts as a thickening agent, imparts excellent tackiness to the film, and is suitable when used as a packaging film. The compounding amount of this polybutene or polyisobutylene is 3 to 30 parts by weight, preferably 5 to 20 parts by weight, relative to 100 parts by weight of the polypropylene resin as the component (A). If the blending amount is less than 3 parts by weight, sufficient tackiness is not exhibited, and conversely, if it exceeds 30 parts by weight, a large amount of bleeding causes stickiness and heat resistance is lowered, which is not preferable. In addition,
The physical properties of the polybutene or polyisobutylene used here can be appropriately determined depending on the blending amount, the types of other components, the intended use of the composition, etc., and therefore, there is no particular limitation, but usually a number average molecular weight of 400 to The range of 3000 is preferable.

(C) of the polypropylene resin composition
The polyglycerin fatty acid ester, which is a component, increases the tackiness of the film when used in combination with the component (B), polybutene or polyisobutylene. Further, antifogging property is also developed. The polyglycerin fatty acid ester is a compound in which at least one of the hydroxyl groups of the glycerol condensation polymer is esterified with a higher fatty acid having 8 to 22 carbon atoms. Here, the glycerin condensation polymer is a condensation polymer having a degree of polymerization of usually 2 to 10, preferably 2 to 6. Among the hydroxyl groups of the glycerin condensation polymer, the number of esterified hydroxyl groups is 1 or more, preferably 1 or more and 70% or less of the number of hydroxyl groups, more preferably 1 or more and 60% of the number of hydroxyl groups. It is the following. Higher fatty acids have 8 to 8 carbon atoms
The fatty acid of 22 may be saturated or unsaturated, and is usually a fatty acid having 10 to 18 carbon atoms. As the polyglycerin fatty acid ester, for example, diglycerin monolaurate, diglycerin monopalmitate,
Examples thereof include diglycerin monooleate, diglycerin monostearate, diglycerin dioleate, triglycerin monooleate and the like.

Of course, two or more kinds of these polyglycerin fatty acid esters may be used in combination. The amount of the polyglycerin fatty acid ester blended is 0.2 to 5 parts by weight with respect to 100 parts by weight of the polypropylene resin as the component (A). If the blending amount is less than 0.2 parts by weight, the synergistic effect with the polybutene or polyisobutylene as the component (B) does not occur. Conversely, if it exceeds 5 parts by weight, a large amount of bleeding causes stickiness and odor, and However, gel is often generated, which is not preferable.

As the component (D), a glyceride having an acyl group having 2 to 6 carbon atoms and an acyl group having 8 to 22 carbon atoms, one of the three hydroxyl groups of glycerin has 2 to 2 carbon atoms.
6 lower fatty acids, the other one must be esterified with a higher fatty acid having 8 to 22 carbon atoms, and the other one is still a hydroxyl group or has 2 to 2 carbon atoms. 6 A diacetin compound or a triacetin compound esterified with a lower fatty acid or a higher fatty acid having 8 to 22 carbon atoms (hereinafter referred to as “mixed glyceride”). The acyl groups of the triacetin compound may of course all be different.
The higher fatty acid may be saturated or unsaturated as long as it is a fatty acid having 8 to 22 carbon atoms, and is usually a fatty acid having 10 to 18 carbon atoms. The lower fatty acid may be any one having 2 to 6 carbon atoms.

Examples of the glycerides of the present invention include, for example, diacetylmonolaurylglycerin, diacetylmonopalmitylglycerin, diacetylmonooleylglycerin, monoacetyldilaurylglycerin, monoacetylmonopalmitylglycerin, monoacetyldioleylglycerin, monoacetyl. Monolauryl glycerin, monoacetyl monooleyl glycerin, dipropionyl monolauryl glycerin, dicaproyl monolauryl glycerin, dicaproyl monopalmityl glycerin, monoacetyl monocapryl glycerin, monoacetyl monobrassyl glycerin, monopropionyl monobrassyl glycerin , Monoacetyl monoerucyl glycerin and the like. Particularly, diacetyl monolauryl glycerin and diacetyl monooleyl glycerin are preferable.

Of course, two or more kinds of these mixed glycerides may be used in combination. The film molded from the polypropylene resin composition containing the glyceride of the present invention has good adhesiveness and can easily adhere to an object without pressure bonding. At the same time, the peeling property between the films is also improved, and the film can be easily fed out during use.

The blending amount of the glyceride of the present invention is 0. 100 parts by weight with respect to 100 parts by weight of the polyolefin resin which is the component (A).
It is 2 to 5 parts by weight, preferably 1 to 5 parts by weight. If the blending amount is less than 0.2 parts by weight, the effect of imparting tackiness is not sufficient, and conversely if the blending amount exceeds 5 parts by weight, the resulting film becomes sticky or significantly slips, resulting in deterioration of workability.

The 4-methyl-pentene resin is a polymer whose main component is 4-methyl-1-pentene, and is, for example,
Homopolymer of 4-methyl-1-pentene, 4-methyl-
1-Pentene and α-other than 4-methyl-1-pentene
Examples thereof include copolymers with olefins. 4-methyl-1
Examples of the α-olefin other than pentene include ethylene, propylene, 1-butene, 1-heptene, 1-
Hexene, 1-octene, 1-decene, 1-dodecene,
C2-C20 alpha-olefins, such as 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc. are mentioned, These alpha-olefins are independent in 2 or more types in 4-methyl-pentene resin. May be included. When the 4-methyl-pentene resin contains these α-olefins, the content thereof is usually about 1 to 10% by weight.

The melting point of these 4-methyl-pentene resins is 220 to 240 ° C., and the melt flow rate (JIS
According to 6758, the value measured at 250 ° C. under a load of 2.16 kg) is usually 0.5 to 30 g / 10 minutes, preferably 5.0 to 20 g / 10 minutes. 0.5 g / 10
If it is less than minutes, the melt viscosity is high and the extrudability is poor, and if the melt flow rate (MFR) is more than 30 g / 10 minutes, the melt viscosity is low and the film moldability is poor.

As the coextrusion molding, a T-die molding method, an air-cooling type or a water-cooling type inflation molding method is adopted, and among these, the T-die molding method or the water-cooling type inflation molding method is preferable. By extruding the melt-extruded resin by the above-mentioned molding method and then rapidly cooling, a film having more excellent transparency can be obtained. The unstretched laminated film obtained by the above coextrusion molding is then uniaxially or biaxially stretched at a stretching ratio of 2 to 8 times, preferably 3 to 5 times. If the stretching ratio is less than 2 times, the cuttability of the film is insufficient, and if it is more than 8 times, the stretching property is deteriorated and breakage or uneven stretching of the film may occur, which is not desirable. In the stretching treatment, the unstretched film is heated as it is or slit into a predetermined width and heated. For example, in the case of a uniaxial film, the peripheral speed of a stretching roll is changed to stretch the film in the take-up direction, that is, the longitudinal direction. In the case of the axis, the stretching is performed in the transverse direction by a tenter stretching method. The preheating temperature in the stretching treatment is usually not higher than the melting point of the polypropylene resin, preferably 70 to 160 ° C.

The heat setting temperature after stretching is higher than the preheating temperature, and it is desirable to set the temperature as high as possible in order to prevent wrinkles of the film and shrinkage at high temperature. Usually, the melting point of the polypropylene resin is lower than the melting point, preferably 80 to 160 ° C.

When the preheating and heat setting temperatures are higher than the melting point of the polypropylene resin, the film melts and adheres to the drawing roll, and when the preheating temperature is lower than 70 ° C., the 4-methyl-pentene resin is insufficient in preheating. Becomes difficult to stretch,
This is not desirable because it causes film breakage. The thickness of the laminated film of the present invention is 40 μm or less, preferably 2 to 3 when used as a packaging film having tackiness.
0 μm, more preferably 5 to 20 μm,
Further, the thickness of the intermediate layer is 10 to the thickness of the entire film.
It is in the range of 90%, preferably 15 to 50%. When the thickness of the laminated 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 (adhesive packaging film).

If the thickness of the intermediate layer is less than 10% of the total thickness, the original heat resistance, mechanical strength, etc. of the 4-methyl-pentene resin cannot be maintained. On the other hand, if it is more than 90%, the thickness of the polypropylene resin layer becomes too thin, and it becomes difficult to uniformly cover the intermediate layer by coextrusion molding.
The thickness of the intermediate layer is preferably 80% or less of the total thickness.

The layered structure of the laminated film of the present invention is essentially composed of at least three resin layers of outer layer / intermediate layer / inner layer, but within the scope of the gist of the present invention, other layers can be used. A resin layer may be added to form a structure of four or more layers. Examples of such a structure having four or more layers include a structure having an adhesive layer or the like between the outer layer and the intermediate layer, or the inner layer and the intermediate layer. As the adhesive layer, a modified polyolefin obtained by grafting an unsaturated carboxylic acid on a polyolefin is used. Further, by adding an appropriate adhesive component to each layer, it is possible to prevent peeling between the layers with the three-layer structure without providing the adhesive layer.

[0024]

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 as long as the gist thereof is not exceeded.
The measurements in the examples were carried out by the following methods. (1) Transparency (haze value) Based on JIS K 6714, it was measured with a haze meter. The measurement results are expressed in%. (2) Heat resistance temperature Paper is placed on the top and bottom 25 mm of a strip-shaped film sample piece having a width of 30 mm and a length of 14 cm, and a weight of 10 g is lowered. The maximum atmospheric temperature that could not be cut in one hour was measured in steps of 10 ° C. (Refer to the description of Tokyo Metropolitan Ordinance No. 1072, "Quality indication of wrap film").

(3) Heat shrinkage rate A film having a diameter of 10 mm was made into a sample by a punching jig,
Dip this in an aluminum pan containing silicone oil,
This aluminum pan is placed on a 140 ° C. hot plate.
Although the temperature of the hot plate once drops because the aluminum pan draws heat, the sample is taken out 45 seconds after the temperature reaches 140 ° C. and the change in size is measured. The measurement result is expressed in%. (4) Cutability The film was wound on a core tube, housed in a wrap film case, and subjected to a cutting test with a saw blade, and evaluated by four levels (good, normal, somewhat poor, and poor). As a standard for evaluation, the cut level of a commercially available wrap film was evaluated as normal.

(5) Adhesive strength Lightly stack two films and lay them on top of each other for 25
Linear pressure 0.3kg / c with roll of mmφ and width of 150mm
The force required for shearing and peeling the two films within 5 minutes and for peeling in the direction of 180 ° C. was measured under the conditions shown in Table 1 with an Instron type tensile tester. It is desirable that the shear peel strength is large and the 180 ° peel strength is small.

[0027]

[Table 1]

(6) Water vapor permeability: Measured in accordance with JIS Z 0208 under the conditions of 40 ° C. and 90% RH. The measurement results are expressed in units of gr / m ² · 24 hr.

Examples 1 to 3 and Comparative Examples 1 to 7 Propylene was used as the polypropylene resin of component (A).
Ethylene random copolymer (MFR: 9.0 (230
℃), density: 0.89; Mitsubishi Kasei Co., Ltd., trade name,
Mitsubishi Polypro 6500J) as component (B), polybutene (average molecular weight 580; manufactured by NOF CORPORATION, trade name Nissan Polybutene 015SH), and component (C) as diglycerin monooleate (manufactured by Riken Vitamin Co., Ltd.)
Diacetylmonolauryl glycerin (manufactured by Riken Vitamin Co., Ltd.) was used as the component (D), and the blending amounts of the respective components were mixed in a blender with the amounts shown in Table 2. Then, using a twin-screw extruder having a diameter of 30 mm, the mixture was pelletized under extrusion conditions of 220 ° C. to produce a polypropylene resin composition.

Next, using a 450 mm wide three-kind five-layer coextrusion T-die molding machine, the above polypropylene resin composition was extruded with a No. 50 mm diameter extruder. 1, 4-methyl-pentene resin (copolymer of 4-methyl-1-pentene and 1-decene, component (B), MFR: 15 (250
C.), melting point: 235.degree. C.), extruder No. 40 mm in diameter 40 mm.
2, and a modified polyolefin resin (adhesive polyolefin resin manufactured by Mitsubishi Kasei Co., Ltd., trade name Novatec-AP006T) having a diameter of 40 mm was used. Put in 3. This is simultaneously extruded at a die temperature of 270 ° C.,
A chill roll temperature of 30 ° C. and a take-up speed of 20 m / min were used to form a film, and an outer layer (polypropylene resin composition) / adhesive layer (adhesive resin) / intermediate layer (4-methyl-pentene resin)
A three-kind five-layer film consisting of / adhesive layer (adhesive resin) / inner layer (polypropylene resin composition) was obtained. The adhesive resin was used to prevent delamination between the polypropylene resin composition layer and the 4-methyl-pentene resin layer.

Then, the film is preheated at a temperature of 90 ° C. in the longitudinal direction and a heat setting temperature of 120 ° C. and a preheating temperature of 13 in the transverse direction.
Longitudinal uniaxial stretching or biaxial stretching was performed at 0 ° C. and a heat setting temperature of 150 ° C. at a magnification shown in Table 2 to obtain a stretched laminated film having a film thickness of 10 μm. The transparency, heat resistant temperature, heat shrinkage ratio, cuttability and adhesive strength of the obtained laminated film were measured. The results are shown in Table 3.

In Comparative Example 2, streaks due to excessive addition of the component (C) (diglycerin monooleate) were generated in the raw film, and a good film was not obtained. In Comparative Example 5, stretching was performed. It was not possible to evaluate the physical properties of the film because breakage occurred and sampling was impossible. Further, the comparatively poor cuttability of Comparative Example 6 is because it was difficult to cut because the film stretched a little.

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

The packaging film of the present invention is excellent in cuttability, transparency, heat resistance, adhesiveness, water vapor barrier property, non-heat shrinkability and food safety. In addition, there is little generation of toxic gas when incinerated. Therefore, the present packaging film is particularly suitable as a wrap film for food packaging.

Claims (5)

[Claims] 1. At least an outer layer, an intermediate layer and an inner layer 3
A laminated film having a layer, wherein the outer layer and the inner layer are made of polypropylene resin and the intermediate layer is made of 4-methyl-pentene resin. 2. A film obtained by coextrusion molding an outer layer and an inner layer made of a polypropylene resin and an intermediate layer made of a 4-methyl-pentene resin, wherein the film has a total thickness of 40 μm or less and an intermediate layer. The laminated film according to claim 1, wherein the layer thickness is 10 to 90% of the total film thickness. 3. The outer layer and the inner layer are (A) 100 parts by weight of polypropylene resin, (B) 3 to 30 parts by weight of polybutene or polyisobutylene, (C) 0.2 to 5 parts by weight of polyglycerin fatty acid ester and (D). ) Carbon number 2-6
The laminated film according to claim 1 or 2, which comprises 0.2 to 5 parts by weight of a glyceride having an acyl group and an acyl group having 8 to 22 carbon atoms. 4. The laminated film is stretched uniaxially or biaxially at a stretch ratio of 2 to 8.
The laminated film according to any one of 1. 5. The laminated film according to claim 1, wherein the laminated film is a packaging film.