JP2003103724A - Pressure-sensitive adhesive laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wrapping film excellent in cutting properties, transparency and heat resistance and suitably used for packaging food to preserve the same or to heat the same in an electronic oven. SOLUTION: In the pressure-sensitive adhesive laminated film having at least a three-layered structure wherein surface layers each comprising a polyethylene resin layer are provided on both surfaces of a polyamide resin layer, the whole thickness of the film is not more than 40 μm and the thickness of the polyamide resin layer is 5-80% of the whole thickness of the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive laminated film used for food packaging and the like, and more specifically, it has excellent cuttability, transparency, adhesiveness, heat resistance, non-heat shrinkability and food safety. The present invention relates to an adhesive laminated film that can be suitably used as a household wrap film.

[0002]

2. Description of the Related Art Conventionally, as a household wrap film used by consumers for food packaging and the like, there is known a film mainly made of polyvinylidene chloride, polyethylene or polyvinyl chloride.

[0003]

However, when a polyvinylidene chloride film is heated in a microwave oven after packaging the food, the film shrinks so much that the food is deformed. When a film comes into contact with oil (such as meat or tempura) and becomes very hot, it has the drawback that the film will melt and open holes. There is a problem of causing a whitening phenomenon. Further, such a wrap film has the following problems in cuttability (easiness of cutting). That is, the wrap film is usually stored in a case such as a paper box,
The film is pulled against a cutting blade called a "saw blade" attached to this case to cut it into an appropriate length. 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, 350-70
A paper box made of coated cardboard of about 0 g / m ² is used,
The rigidity is extremely low.

The above-mentioned film is required to be easily cut by a consumer's manual operation even by a simple cutting mechanism, but in reality, the case and the "saw blade" are not always deformed. Instead, the film may be distorted 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. Further, the conventional polyethylene-based film may be bent or deformed because the film stretches or requires a tensile force when cut.

[0005]

Means for Solving the Problems The inventors of the present invention have made earnest studies to produce a packaging film capable of solving the above-mentioned problems of conventional wrap films, and as a result, a polyethylene resin layer was formed on both sides of the polyamide resin layer. By stretching the laminated film having a surface layer of, in the film taking direction,
The above problems are solved, and the cuttability, without impairing the original properties (heat resistance, mechanical properties) of the polyamide resin,
It has been found that a packaging film excellent in transparency, adhesiveness, heat resistance, non-heat shrinkage and food safety can be obtained.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The pressure-sensitive adhesive film of the present invention has a layer structure of at least three layers, and is composed of, for example, three layers of outer layer (surface layer) / intermediate layer / inner layer (surface layer). Examples of the polyethylene resin constituting the surface layer include a low density polyethylene resin, a linear low density polyethylene resin and a high density polyethylene resin, and a linear low density polyethylene resin is particularly preferably used. The linear low density polyethylene resin of the present invention,
It is a copolymer of ethylene and other α-olefin, and ethylene accounts for 40% or more, preferably 70% or more, and α
-Olefins having 3 to 12 carbon atoms. The α-olefin may be linear or branched and is, for example, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1,4-methylpentene-1,4-.
Methylhexene-1,4,4-dimethylpentene-1 and the like are used alone or in plural.

The linear low density polyethylene resin preferably has a density of 0.900 to 0.950 g /
cm ³ , particularly preferably in the range of 0.910 to 0.940, and the melt flow rate (MFR) is preferably 0.5 to 40 g / 10 minutes, particularly preferably 1 to 30.
The range of g / 10 minutes is preferable. Polyglycerin fatty acid ester is preferably added to the polyethylene resin of the surface layer in order to improve the tackiness. This polyglycerin fatty acid ester means that at least one of the hydroxyl groups of the condensation polymer of glycerin has 8 to 22 carbon atoms.
The higher fatty acid and other fatty acid esterified compounds. Here, the degree of polymerization of the glycerin condensation polymer is usually 2-1.
It is a condensation polymer of 0, preferably 2 to 6. Of 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. The higher fatty acid may be saturated or unsaturated as long as it has 8 to 22 carbon atoms, and is usually preferably 10 to 18 carbon atoms.

As the polyglycerin fatty acid ester,
For example, diglycerin monolaurate, diglycerin monooleate, diglycerin monostearate, diglycerin dioleate, diglycerin trioleate and the like can be mentioned. Of course, two or more kinds of these polyglycerin fatty acid esters may be used in combination. The blending amount of this polyglycerin fatty acid ester is polyethylene resin 100.
0.2 to 10 parts by weight, preferably 0.5
~ 6 parts by weight. If the blending amount is less than 0.2 parts by weight, the tackiness is not sufficiently improved. On the contrary, if the blending amount exceeds 10 parts by weight, a large amount of bleeding causes stickiness and odor, and gel is frequently generated, which is not preferable.

On the other hand, examples of the polyamide resin constituting the intermediate layer of the present invention include aromatic polyamide resins, aliphatic polyamide resins, and mixtures thereof. The heat resistance and barrier properties required for wrap films, and raw materials From the viewpoint of cost, an aliphatic polyamide resin is usually used. For example, hexamethylenediamine, decamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, 1,3- or 1,4-bis (aminomethyl) cyclohexane, bis (p-aminocyclohexylmethane), m- or p-xylylenediene. Polycondensation of aliphatic, alicyclic and aromatic diamines such as amines with adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid and other aliphatic, alicyclic and aromatic dicarboxylic acids Polyamide obtained by ε
-A polyamide obtained by condensation of aminocarboxylic acids such as aminocaproic acid and 11-aminoundecanoic acid, ε
Examples thereof include polyamides obtained from lactams such as caprolactam and ε-laurolactam, and copolyamides thereof. Specifically, nylon-6, nylon-
6,6, nylon-6,10, nylon-9, nylon-11, nylon-12, nylon-6 / 6,6, nylon-6,6 / 6,10, nylon-6 / 11 and the like. From the viewpoint of moldability, the melting point is 170 to 280.
A temperature of ℃, preferably 190 to 250 ℃ is suitable. In the present invention, nylon-6, nylon-6,6 and nylon-6 / 6,6 are particularly preferably used.

An adhesive resin layer is provided to prevent the polyamide resin layer and the polyethylene resin layer from being separated from each other.
It is preferable to have a layered structure. As the adhesive resin, a commonly used acid-modified polyolefin resin or the like is used. The method for producing the pressure-sensitive adhesive film of the present invention is, for example, coextrusion molding of the above-mentioned polyethylene resin, polyamide resin, and adhesive resin into a layer structure of 5 layers of 3 types, for example (polyethylene resin / adhesive resin / polyamide resin / A multilayer film of (adhesive resin / polyethylene resin) is molded, and then the film is uniaxially stretched in its take-up direction (longitudinal direction).

As the above coextrusion molding, a T-die molding method or a water-cooled inflation molding method is preferable. That is, by rapidly cooling the melt-extruded resin by the above-mentioned molding method, a film having more excellent transparency can be easily obtained as compared with the air-cooled inflation molding method which is usually used. The unstretched multilayer film obtained by the coextrusion molding is then uniaxially stretched in the film-drawing direction (longitudinal direction) at a stretch ratio of 1.5 to 5 times, preferably 1.7 to 4 times. If the draw ratio is less than 1.5 times, the cuttability of the film is insufficient, and if it is more than 5 times, the drawability is lowered and breakage or uneven drawing of the film may occur, which is not preferable. The stretching treatment is performed by, for example, a method of heating the unstretched film as it is or slitting it into a predetermined width and stretching the film in the take-up direction, that is, the longitudinal direction by changing the peripheral speed of a stretching roll. The preheating temperature for the stretching treatment is usually not higher than the melting point of the polyethylene resin, preferably 40 to 120 ° C.

The heat setting temperature after stretching is preferably higher than the preheating temperature, and is preferably as high as possible in order to prevent wrinkles of the film and improve lateral strength. Desirably 80-12
It is preferable to carry out in the range of 0 ° C. When the preheating and heat setting temperatures are higher than the melting point of the polyethylene resin, the film melts and adheres to the stretching roll, and the preheating temperature is 40 ° C.
If it is less than the above range, it is difficult to stretch the film due to insufficient preheating, and film breakage occurs, which is not preferable.

The thickness of the adhesive laminated film of the present invention is 40 μm or less, preferably 2 to 30 μm, more preferably 5 to 20 μm, and the thickness of the intermediate layer is 5 to 80% of the total thickness. Must be in the range. If the thickness of the film exceeds 40 μm, the tear strength at the time of cutting the film becomes too large, which is unsuitable for use as a wrap film. If the thickness of the intermediate layer is less than 5% of the total thickness, the original heat resistance and mechanical strength of the polyamide resin cannot be maintained, and the physical properties of the uniaxially stretched polyethylene film become dominant, so tear in the stretching direction. It will be easier. The thickness of the intermediate layer is preferably 10% or more of the total thickness. On the other hand, if it exceeds 80%, the thickness of the polyethylene layer becomes thin, and it becomes difficult to uniformly cover the intermediate layer by coextrusion molding. The thickness of the intermediate layer is 7 of the total thickness.
It is preferably 0% or less.

[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 the gist thereof is exceeded. The measurements in the examples were carried out by the following methods.

(1) Transparency Measured using a transparency measuring instrument manufactured by Murakami Color Research Laboratory Co., Ltd. Three kinds of measured values, MAX value, MIN value, and AVE value, are obtained, but the MAX value corresponding to the visual feeling is displayed.

(2) A heat-resistant temperature width of 30 mm and a length of 140 mm of a strip-shaped film test piece was placed on a sheet of paper 25 mm above and below, a weight of 10 g was lowered, and the maximum atmospheric temperature that could not be cut in one hour was measured in steps of 10 ° C.

(3) A film having a diameter of 10 mm was made into a sample with a heat shrinkage punching jig,
This was dipped in an aluminum pan containing silicone oil, and this aluminum pan was placed on a hot plate at 140 ° C. The temperature of the hot plate drops once because the heat is taken away by the aluminum pan.
A sample was taken out after a second and its size change was measured.

(4) The cuttable film was wound on a paper tube, housed in a case for wrapping film, and subjected to a cutting test with a saw blade, and evaluated according to four levels (good, normal, somewhat poor, and poor). In addition,
As a standard for evaluation, the cut level of the commercially available wrap film was evaluated as normal.

(5) Adhesive strength is lightened and two films are superposed, and the two films are placed on top of each other.
A linear pressure of 0.3 kg / with a roll of 5 mmφ and a width of 150 mm
cm ² three times pressurized with the case of shear peeling the two films within 5 minutes, the force of the Instron-type tensile testing machine required when peeling angle of 180 degrees (Orientec Co. "UTM-4L ]) Was measured. The conditions are shown in Table 1.

[0020]

[Table 1]

(6) Tensile elongation at break The tensile elongation at break was measured by a tensile tester ("UTM-4L" manufactured by Orientec Co., Ltd.) according to JIS K 7127.

Example 1 Using a 450 mm width three-kind five-layer coextrusion T-die molding machine, Table 2
The resin shown in 3 is simultaneously extruded from three extruders at a die temperature of 260 ° C., a chill roll temperature of 20 ° C. and a take-up speed of 20 m /
A three-kind, five-layer film (thickness) consisting of an outer layer (polyethylene resin) / adhesive layer (modified resin) / intermediate layer (nylon-6) / adhesive layer (modified resin) / inner layer (polyethylene resin) 30 μm, layer ratio 3: 1: 2: 1: 3). The resin composition for the inner and outer layers was prepared by mixing the components shown in Table 2 in a blender at the ratios shown in Table 2 and then pelletizing the mixture using a twin-screw extruder having a diameter of 30 mm under extrusion conditions of 200 ° C. Prepared. Then, the film was stretched by a roll stretching machine at a preheating temperature of 90 ° C and a heat setting temperature of 110 ° C by 3.0 times in the machine direction. The evaluation results of the obtained film are shown in Table 3.

[0023]

[Table 2]

Example 2 The same contents as in Example 1 were used except that the raw fabric molding was water-cooled inflation molding. The results are shown in Table 3. In addition, the original fabric forming condition is a die diameter of 75 m.
mφ, die temperature 250 ° C., blow-up ratio 1.8, take-up speed 15 m / min, folding width 210 mm, thickness 30 μm
Was formed into a film.

Comparative Examples 1 to 4 In Example 1, the film thickness and layer ratio shown in Table 3
The procedure was the same except that the stretching ratio was changed. The results are shown in Table 3.

[0026]

[Table 3]

[0027]

The film of the present invention is used for various packaging applications such as food packaging applications. In particular, the film of the present invention can be preferably used as a wrap film because the outer layer and the inner layer constituting both surface layers have good adhesiveness.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 77:00 B29K 77:00 B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Kazuaki Kanda 5-8 Mitsuya-cho, Nagahama-shi, Shiga Mitsubishi Plastics Co., Ltd. Nagahama Factory (72) Inventor Hideki Sasaki 5-8 Mitsuya-cho, Nagahama-shi, Shiga Mitsubishi Plastics Co., Ltd. F-term (reference) 3E086 AD13 BA04 BA15 BA33 BB41 BB68 BB90 CA01 4F100 AK01D AK01E AK04B AK04C AK41B AK41C AK46A AK48A AK63B AK63C AL05B AL05C BA03 BA04 BA05 BA06 BA10B BA10C BA15 EH20 EJ37 GB15 GB23 JA03 JA20 JA20A JJ03 JK02 JK06 JK08 JL11D JL11E JL13 JN01 YY00 YY00A YY00B YY00C 4F210 AA03 AA08 AA29 AE10 AF16 AG01 AG03 QA03 QC02 QG01 QG15 QG18

Claims (7)

[Claims] 1. A film having at least three layers having a surface layer of a polyethylene resin layer is coextruded on both sides of a polyamide resin layer, and then stretched at a draw ratio of 1.5 to 5 times in a film taking direction. A tacky laminated film obtained by the method, wherein the total thickness of the film is 40 μm.
Below, and the thickness of the said polyamide resin layer is 5 to 80% of the thickness of the whole film, The adhesive laminated film characterized by the above-mentioned. 2. The adhesive laminated film according to claim 1, wherein the surface layer is a linear low density polyethylene resin. 3. The adhesive composition according to claim 1, wherein the surface layer is a resin composition obtained by adding 0.2 to 10 parts by weight of polyglycerin fatty acid ester to 100 parts by weight of polyethylene resin. Laminated film. 4. The adhesive laminated film according to claim 1, wherein the polyamide resin is an aliphatic polyamide resin. 5. The pressure-sensitive adhesive laminated film according to claim 1, wherein an adhesive resin layer is interposed between the polyamide resin layer and the polyethylene resin layer. 6. A tensile elongation at break of 200% or less in a direction parallel to the take-up direction and an elongation at break of 80 in a vertical direction.
% Or more, and the ratio (parallel / vertical) of the tensile elongation at break in the direction parallel to the take-up direction and the direction perpendicular to the take-up direction is 0.7 or less. Adhesive laminated film of. 7. The pressure-sensitive adhesive laminated film according to claim 1, which is a household wrap film.