JPH1035720A - Packing laminated film having aliphatic polyamide resin as outermost layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packing multilayered film hard to generate melt fracture, excellent in label aptitude, surface glass, transparency and gas barrier properties and having proper flexibility. SOLUTION: The outermost layer is composed of aliphatic polyamide resin and an oxygen barrier layer is constituted of either one of a compsn. (1) consisting of 60-95wt.% of a saponified ethylene/vinyl acetate copolymer, 4-35wt.% of an ionomer of an ethylene/unsaturated carboxylic acid copolymer and 1-30wt.% of polyamide, a vinylidene chloride resin (2), a polyacrylonitrile or unsaturated nitrile resin (3) and an aromatic polyamide resin (4) and the innermost seal layer is composed of ultra-low density polyethylene and the saturated water absorbancy of the film constituting the outermost layer immersed in water at 23 deg.C is 5.0% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ultra low density polyethylene (V) having a specific aliphatic polyamide resin as an outermost layer.
The present invention relates to a laminated film for packaging having a layer made of LDPE) as an innermost layer (seal layer). The laminated film for packaging provided by the present invention is excellent in label suitability, surface gloss, transparency, gas barrier property and moldability, and has appropriate flexibility, and is suitable for packaging of articles, mainly livestock meat products, processed marine products. It is used for packaging of processed foods.

[0002]

BACKGROUND OF THE INVENTION There are many types of food packaging, but the properties required for the film used in each packaging are different. For example, a film for vacuum deep drawing packaging is required to have a close contact between the packaged object and the film. This is desirable in that the appearance of the packaged product can be clearly seen even when the packaged product is non-food, in that the film adheres closely to the shape of the packaged product. In the case of wrapped material such as meat that is liable to cause sap separation, sap separates into the gap between the film and the wrapped material, causing close contact with the film as it may impair the appearance or cause spoilage. (Adhesion) is desired. In addition, the packaged product must be clearly visible (transparency), the film must not be wrinkled during primary and secondary molding (moldability), and the packaged product itself must withstand abuse (pinhole resistance). Having a gloss on the surface of the package (surface gloss),
It is desired that a label can be easily applied to a package (label suitability) and that the contents can be stored for a long time (gas barrier property). Similar properties are not limited to deep drawing packaging, but also include pillow packaging,
It is similarly desired for pouches and the like.

Many proposals have hitherto been made to satisfy these demands. For example, in JP-A-7-1544, the outermost layer is a 12 nylon resin layer or a polyamide layer of a copolymer of 12 nylon and 6 nylon, the intermediate layer is a polyamide resin layer sandwiched between polyolefin adhesive resin layers, or A polyamide resin layer and an ethylene-vinyl acetate copolymer saponified layer sandwiched between polyolefin-based adhesive resin layers,
There is disclosed a co-extruded composite film for deep drawing in which a sealable resin layer is disposed on the innermost layer and the thickness of the outermost layer is 15% or less of the total thickness. Although this film satisfies many of the above demands, it tends to cause melt fracture as shown in Comparative Example 2 of the present invention having the same configuration as the specific example of the prior art. When such a melt fracture occurs, even if the degree is light, it causes uneven thickness, and when the film is wound up, or when the secondary molding is performed, wrinkles are generated, and the surface gloss is deteriorated. Bad appearance. In the worst case, there is a hole, and in any case, it is not usually a product.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer film for packaging which is less likely to cause melt fracture, is excellent in label suitability, surface gloss, transparency and gas barrier properties, and has appropriate flexibility. It is in.

[0005]

Means for Solving the Problems The present inventors have found that the gas barrier layer in the above prior art can solve the above problems in a specific resin composition, and have completed the present invention. Was.

That is, according to the present invention, the outermost layer is made of an aliphatic polyamide resin, and the oxygen barrier layer is
Any one of the constitutions of (4), that is, (1) saponified ethylene-vinyl acetate copolymer 60 to 95
(2) Consisting of vinylidene chloride-based resin (3) Consisting of polyacrylonitrile or unsaturated nitrile-based resin Or (4) an aromatic polyamide resin, wherein the innermost sealing layer is made of ultra-low density polyethylene, and the film constituting the outermost layer has a saturated water absorption of 5.0 after immersion in water at 23 ° C. % Or less in the laminated film for packaging. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The outermost layer used in the present invention is made of an aliphatic polyamide resin, and the film constituting the layer has a saturated water absorption of 5.0% or less after immersion in water at 23 ° C. 2.0% or less. In addition, the measurement of the saturated water absorption was performed according to ASTM D-570. In addition, the film thickness is kept as the thickness of the outermost layer film. This resin layer contributes to the improvement of label suitability and has excellent surface gloss. Further, when combined with another resin layer constituting the present invention, the transparency of the laminated film is also excellent.

Specific examples of the aliphatic polyamide resin constituting the outermost layer include polyhexamethylene sebacamide (nylon-6,10), polyundecaneamide (nylon-11), and polylauryl lactam (nylon-1).
2) and the like.

The outermost layer becomes the packaging surface when the film is used for packaging. A label is attached to this surface to produce a product, and an adhesive is applied to the back side of the label. Usually, acrylic pressure-sensitive adhesives are used as pressure-sensitive adhesives for labels for food packaging. Polycapramide (nylon-6), polyhexamethylene adipamide (nylon-
6,6) and caprolactam / hexamethylenediammonium adipate copolymer (nylon-6 / 6,6), any of which is used for the outermost layer, the label after labeling is easily peeled off after boiling. However, the use of an aliphatic polyamide resin having a saturated water absorption of 5.0% or less makes it difficult for the label to peel off. Further, when these polyamides are used, the surface gloss of the package is further improved. Of these polyamides, nylon-11 and nylon-12 are particularly preferred.

The oxygen barrier layer has any one of the following constitutions (1) to (4): (1) saponified ethylene-vinyl acetate copolymer 60 to 95;
(2) Consisting of vinylidene chloride-based resin (3) Consisting of polyacrylonitrile or unsaturated nitrile-based resin Or (4) an aromatic polyamide resin.

Of these, (1) is particularly preferably used. The saponified ethylene-vinyl acetate copolymer used in (1) is 60 to 95% by weight in the oxygen barrier layer,
Preferably 70-95% by weight, even more preferably 80%
~ 95% by weight is used. If it exceeds 95% by weight, melt behavior is poor and melt fracture is likely to occur depending on the resin composition to be laminated, and if it is less than 60% by weight, the oxygen barrier property is undesirably reduced.

In the oxygen barrier layer, the ionomer of the ethylene-unsaturated carboxylic acid copolymer used in (1) is 4 to 35% by weight, preferably 5 to 25% by weight, and more preferably 5 to 15% by weight. It is. If it is less than 4% by weight, melt fracture tends to occur, and if it exceeds 35% by weight, the oxygen barrier property is reduced.

Further, the polyamide used in (1) makes the mixture of the saponified ethylene-vinyl acetate copolymer and the ionomer uniform and contributes to transparency. If no polyamide is contained, the transparency is poor, and if it is too large, gelation occurs and the transparency deteriorates. Accordingly, the polyamide is present in the gas barrier layer in an amount of 1 to 30% by weight, preferably 1 to 25% by weight, and more preferably 1 to 20% by weight.

The saponified ethylene-vinyl acetate copolymer used in (1) usually has an ethylene content of 20 to 60.
Mol% and a saponification degree of 60 mol% or more are preferable, and more preferably, an ethylene content is 30 to 55 mol% and a saponification degree is 70 mol%.
Mol% or more, more preferably 40 to 50 mol% of ethylene content and 80 to 100 mol% of saponification degree.

In the ionomer of the ethylene-unsaturated carboxylic acid copolymer used in (1), the unsaturated carboxylic acid is 4 to 15 mol%, preferably 5 to 12 mol%,
Particularly, 6 to 10 mol% is suitably used. If the amount is less than 4 mol%, the transparency is reduced. If the amount exceeds 15 mol%, the strength of the film is reduced.

Further, the ionomer may be a terpolymer. In the case of a terpolymer, it is preferable to use another copolymerizable monomer in an amount of 12 mol% or less, preferably 8 mol% or less, in addition to the above-mentioned copolymer monomer. These copolymers are obtained by radical polymerization at high temperature and high pressure.

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, and maleic anhydride. Among them, acrylic acid and methacrylic acid are preferably used.

Other copolymerizable monomers include vinyl esters such as vinyl acetate and vinyl propionate, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, isobutyl methacrylate, and maleic acid. Examples include unsaturated carboxylic acid esters such as diethyl and carbon monoxide.

The metal ions of the ionomer are ions of alkali metals such as lithium, sodium and potassium, alkaline earth metals such as calcium and magnesium, and ions of zinc and the like. Among them, zinc ion is particularly preferred. The degree of ionization is in the range of 5 to 100%, preferably 10 to 90%, and more preferably 30 to 70%.

Polyamides used in (1) include polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), and polylauryl lactam (nylon). -12), polyethylene diamine adipamide (nylon-2,6), polytetramethylene adipamide (nylon-4,6), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene sebaca Amide (nylon-6,10), polyhexamethylene dodecamide (nylon-6,12), polyoctamethylene adipamide (nylon-8,6), polydecamethylene adipamide (nylon-10,8), Alternatively, caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / ω-amino Phosphate copolymer (nylon 6 /
9), caprolactam / hexamethylene diammonium adipate copolymer (nylon-6 / 6,6), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon-12 / 6,6), hexamethylene diammonium adipate Polymer (nylon-2,6
/ 6,6), caprolactam / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon-6,6 / 6,10), ethylenediammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium Sebacate copolymer (nylon-6 / 6,6 / 6,1
0), polymethaxylylene adipamide (MXD6), hexamethylene terephthalamide / hexamethylene isophthalamide copolymer (nylon 6I-6T) and the like. Among these polyamides, those having a melting point of 240 ° C. or lower, particularly 230 ° C. or lower, as determined by DSC are preferably used.

Regarding the composition of the polyamide and the ionomer used in (1), the product name is “Himilan A”
M7926 "is commercially available from Mitsui Dupont Polychemicals, Inc.

The oxygen barrier layer may be made of (2) a layer made of vinylidene chloride resin, (3) a layer made of polyacrylonitrile or unsaturated nitrile resin, or (4) a layer made of aromatic polyamide resin. Is also good. The unsaturated nitrile-based resin includes a hynitrile-based copolymer resin containing 50% by weight or more of unsaturated nitrile. Examples of the aromatic polyamide resin include polymethaxylylene adipamide (MXD6) and hexamethylene terephthalamide / hexamethylene isophthalamide copolymer (nylon 6I-6T).

In the laminated film for packaging of the present invention, an intermediate layer may be provided between the outermost layer and the innermost layer in addition to the oxygen barrier layer. This layer is not required for applications where the strength is not particularly required for the laminate. Examples of the resin used for the intermediate layer include a polyamide resin, a polyolefin resin, and a recycled resin. Among them, a polyamide resin is preferably used.

The innermost layer is made of VLDPE. This layer has a function as a sealing layer. The VLDPE used in the present invention has a density of 0.87 to 0.920 g / cm ^3.
In, ethylene as a main component, propylene as a sub-component,
Butene-1, pentene-1,4-methylpentene-1,
Α- up to 10 carbon atoms such as hexene-1 and octene-1
Copolymers with olefins are included. It can be used irrespective of one produced by a Ziegler catalyst or one produced by a metallocene catalyst. Further, a mixture of the above resins may be used. VLDPE is preferably used because it has good sealing properties, hot tack properties, and transparency.

These VLDPEs are preferably selected from those having a crystal melting point of 86 ° C. or higher, more preferably in the range of 90 to 125 ° C. in consideration of the function as a seal layer. In addition, a mixed resin of a resin having a low melting point and a resin having a higher melting point for adjusting the sealing temperature range may be used.

The innermost layer may contain an anti-blocking agent, a lubricant and the like. Powders such as silicon oxide, calcium carbonate, and magnesium oxide are preferably used as the anti-blocking agent, and oleic amide, palmitic amide, erucic amide, and stearic amide-based lubricant are preferably used as the lubricant. The amount of these additives is 0.02 to 0.8% by weight, preferably 0.2 to 0.6% by weight of these antiblocking agents in the innermost layer, and 5 × 10
^Over 3 to 0.2 wt%, preferably it is desirable to include in the range of 5 × 10 ^over from 2 to 0.15 wt%. A method of adding a masterbatch containing these antiblocking agents and lubricants is suitably used. When VLDPE used for the seal layer has a large tackiness, it is desirable to use an anti-blocking agent and a lubricant for the purpose of preventing troubles due to stickiness when winding the film.

Another intermediate layer made of polyolefin may be provided on the outermost layer side adjacent to the innermost layer. This intermediate layer becomes another strength-imparting layer. The resin used as the polyolefin in this layer is not limited as long as the transparency of the film is not impaired. It may be of the same type as the innermost layer VLDPE or may be of a different type. For example, polyethylene, polypropylene, copolymers of propylene and other α-olefins, LLDPE, VLDP
E, ethylene-vinyl acetate copolymer and the like.
In addition, the anti-blocking agent and the lubricant added to the innermost layer may be dissipated in the molding process and the effect may not be remarkably exhibited. Therefore, these additives are added to the intermediate layer, and transferred to the innermost layer. The effect may be maintained. Of the above resins, VLDPE is preferably used.

An adhesive layer may be provided to further increase the adhesion between the layers. By providing an adhesive layer on both sides of the oxygen barrier layer, the pinhole resistance of the entire film can be improved. As the resin used for the adhesive layer, a thermoplastic polymer having a low softening temperature, an unsaturated carboxylic acid-modified product of these resins or a metal-modified acid-modified product thereof, and a mixture containing these are preferable.
For example, ethylene-vinyl acetate copolymer, ethylene and ethyl acrylate copolymer, and olefin copolymer modified with maleic acid, acrylic acid, methacrylic acid, itaconic acid or anhydride thereof, thermoplastic polyurethane elastomer, Blend resins including one or more of these are used. Among these, maleic acid-modified polyolefins, such as maleic acid-modified LLDP
E, ethylene-vinyl acetate copolymer and the like are preferably used.

The thickness of the laminate is not particularly limited, but when used as a film for deep drawing, the total thickness of the layer is preferably 100 to 250 μm, more preferably 120 to 250 μm.
２５０250 μm. The thickness of the outermost layer is 10 to 40 μm,
Further, 10 to 35 μm is desirable. The thickness of the innermost layer is preferably 10 to 80 μm, more preferably 15 to 80 μm.
m is desirable. The thickness of each layer may be appropriately selected according to the packaging object.

In the production of the laminated film, various additives, stabilizers and the like may be added to each resin layer, if necessary, as long as the desired properties are not impaired. The additives can be blended by a known method. Each resin is melt-kneaded in a different extruder, and is melt-molded by T-die coextrusion or circular die coextrusion. The laminated film of the present invention may be stretched or unstretched. The stretched film is stretched by a known method such as a T-die stretching method and an inflation method. When it is not stretched, a melt having a laminated structure is usually formed at a resin temperature of 200 to 250 ° C. by T-die coextrusion. Next, a method of setting a draft ratio so that the melt has a specified thickness, rapidly cooling the same on a chill roll usually at 40 to 60 ° C., and drafting to obtain an unstretched multilayer film is preferably used. When the laminated film is used for deep drawing, it is preferable to use a film having the above thickness range. In this case, the film is used such that the innermost layer of the film is in contact with the object to be packaged.

[0031]

The present invention will be described below in detail with reference to examples. Evaluation of the obtained film was performed by the following method. 1. Gloss Measured according to ASTM D523. 2. Transparency (Haze) Measured according to ASTM D1003. 3. Flexibility (Young's modulus) Measured according to ASTM D882. 4. Saturated water absorption Measured according to ASTM D570. However, the thickness of the film was measured with the thickness of the outermost film.

5. Label aptitude Using a label using an acrylic pressure-sensitive adhesive, the peel strength of a label labeled under the following conditions was measured. The peel strength was measured by 180 ° peeling at 5 ° C. and a peel speed of 200 mm / min. a) After the film filled with baked pig was immersed in water at a temperature of 5 ° C. for 30 minutes, the label was immersed in water, and the label was stuck on the outermost surface of the film by hand. Immediately after the application, the peel strength was measured. b) The film of the present invention filled with baked pork is heated at 98 ° C. for 30 minutes.
After immersion in boiling water, the film is taken out, the water droplets on the outermost film surface are wiped off, and the film is placed in an atmosphere of 5 ° C.
Next, the film was returned to the air at 23 ° C., and a label was stuck on the outermost layer surface while water droplets were condensed on the film surface. Immediately after the application, the peel strength was measured. This condition is similar to the labeling process after the sterilization of the boil actually performed by the user. c) A label was attached to the outermost layer of the film left at room temperature. Immediately after the application, the peel strength was measured.

6. Presence or absence of melt fracture The film was rapidly cooled on a chill roll, and was evaluated for the presence or absence of ripples on the surface of the film before being drafted and wound.

Example 1 A multilayer film having a seven-layer structure was formed using the following six kinds of resin materials. (1) Outermost layer: nylon-11 (using "RILSAN BESN OTL" sold by Toray Industries, Ltd., density 1.04 g / cm ³ ) Relative viscosity 2.75, melting point 186
° C). (2) Oxygen barrier layer: saponified ethylene-vinyl acetate copolymer (manufactured by Nippon Synthetic Chemical Co., Ltd .; Soarnol A4412)
B, density 1.14 g / cm ³ , MFR 12.0 g / 10
Min. [210 ° C.], melting point 164 ° C., ethylene content 44 mol%) and a composition of an ionomer and a polyamide having a composition ratio (weight) of 7: 3 (Mitsui DuPont Polychemical Co., Ltd.)
"Himilan AM7926" density 1.0g / c
m ³ , MFR 9.01 g / 10 min [230 ° C.], melting point 8
1 ° C, 198 ° C) in a 90:10 weight ratio. (3) Adhesive layer: Maleic acid-modified LLDPE (manufactured by Mitsui Petrochemical Co., Ltd .; "Admer", density 0.904 g / cm)
³ , MFR 9.5 g / 10 min [190 ° C], melting point 104
° C, 123 ° C). (4) Intermediate layer 1: Nylon-6 / 6,6 (Toray Industries, Inc.)
"Amilan CM6001XF" density 1.13 g / c
m ³ , relative viscosity 3.2, melting point 195 ° C, copolymerization (weight)
Specific nylon-6: nylon 6,6 = 85:15). (5) Intermediate layer 2: ethylene-1-octene copolymer (manufactured by The Dow Chemical Company; VLDPE, “AF
FINITY FW1650 ", density 0.902g / c
m ³ , MFR 3.0 g / 10 min [190 ° C.], melting point 98
° C). (6) Innermost layer: The same VLDPE as that of the intermediate layer 2 was used in which 0.4% by weight of silicon oxide was added as an antiblocking agent and 0.1% by weight of erucic acid amide was added as a lubricant.

Using the six extruders, the above six resin materials are separately melt-kneaded, and the outermost layer / adhesive layer / oxygen barrier layer / intermediate layer 1 is formed at a resin temperature of 230 ° C. by co-extrusion using a T-die.
A melt having a seven-layer structure of / adhesive layer / middle layer 2 / innermost layer was formed. Then, a draft ratio was set so that the melt had a specified thickness, rapidly cooled on a chill roll at 40 ° C., and drafted to obtain an unstretched multilayer film. The thickness of the obtained multilayer film is 20 μ / 10 μ / 15 μ /
40 μ / 10 μ / 90 μ / 15 μ was a total of 200 μm. The obtained results are shown in Table 1 together with the outline of the constitution of the oxygen barrier layer.

(Example 2) A seven-layer laminated film was obtained in the same manner as in Example 1 except that only the following outermost layers were used. The obtained results are shown in Table 1 together with the outline of the constitution of the oxygen barrier layer. Outermost layer: Nylon-12 (manufactured by Ube Industries, Ltd .; “Ube Nylon 3030XA”, density 1.02 g / cm ³ , relative viscosity 2.85, melting point 180 ° C.).

(Comparative Example) The procedure of Example 2 was repeated, except that the gas barrier layer of Example 2 was changed to only the ethylene-vinyl acetate copolymer used in Example 2. The obtained results are shown in Table 1 together with the outline of the constitution of the oxygen barrier layer.

[0038]

[Table 1]

[0039]

The laminated film of the present invention uses a specific aliphatic polyamide for the outermost layer and a specific ethylene-vinyl acetate copolymer composition for the gas barrier layer so that melt fracture hardly occurs. ,
It has excellent suitability for labels, surface gloss, transparency, and gas barrier properties, and has appropriate flexibility.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication B65D 1/09 B65D 1/00 B (72) Inventor Takashi Sato Tadashi, Tamari-mura, Tamari-mura, Niibari-gun, Ibaraki 18-13 Kureha Chemical Industry Co., Ltd. Resin Processing Technology Center

Claims (6)

[Claims] The outermost layer is made of an aliphatic polyamide resin, and the oxygen barrier layer has any one of the following constitutions (1) to (4): (1) a saponified ethylene-vinyl acetate copolymer 60 to 60; 95
% By weight, 4 to 35% by weight of an ionomer of an ethylene-unsaturated carboxylic acid copolymer and 1 to 30% by weight of a polyamide (2) A vinylidene chloride resin (3) A polyacrylonitrile or unsaturated nitrile resin Or (4) a film composed of an aromatic polyamide resin, the innermost seal layer is composed of ultra-low density polyethylene, and the film constituting the outermost layer has a saturated water absorption after immersion in water at 23 ° C. of 5. 0% or less of the laminated film for packaging. 2. An oxygen barrier layer comprising 60 to 95% by weight of a saponified ethylene-vinyl acetate copolymer, 4 to 35% by weight of an ionomer of an ethylene-unsaturated carboxylic acid copolymer, and 1 to 30% by weight of a polyamide. Item 4. The laminated film for packaging according to Item 1. 3. The outermost aliphatic polyamide resin is at least one selected from the group consisting of nylon-11, nylon-12 and nylon-6,10.
The laminated film for packaging according to 1. 4. The laminated film for packaging according to claim 1, which is for deep drawing. 5. The laminated film for packaging according to claim 1, which is for pillow packaging. 6. The laminated film for packaging according to claim 1, which is used for pouches.