JP3169281B2 - Inner container for bag-in-box - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner container for a bag-in-box, and more particularly, to an inner container for a bag-in-box which is excellent in punching workability of a liquid inlet and maintains gas barrier properties for a long period of time. Is provided.

[0002]

2. Description of the Related Art In general, saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) is excellent in transparency, antistatic property, oil resistance, solvent resistance, gas barrier property, fragrance retention property and the like. However, it is a material having disadvantages such as low impact resistance, bending fatigue resistance, stretchability, thermoformability, and low gas barrier properties when absorbing moisture or water. For this reason, in the intended use of packaging materials, a gas barrier property, aroma retention property, and food discoloration prevention property are obtained by laminating films of low density polyethylene, polypropylene, nylon, polyester, etc. on both sides of an EVOH film. While maintaining the characteristics of EVOH, such as falling strength, thermoformability, moisture proof, etc., it is used for various packaging applications by compensating for the disadvantages of EVOH.

[0003] In recent years, bag-in-box containers have been used as packaging containers for transporting and storing liquids for beverages such as wine and juice, and liquids for photographic developers. This bag-in-box is
A flexible plastic packaging container provided with a liquid injection port is housed inside a cardboard box, and is frequently used as a means for transporting various liquids. The above-described EVOH laminate is also used as an inner container of the bag-in-box. Has been reached.

The required performance of the inner container at this time is as follows:
Since it is important to maintain excellent gas barrier properties against extremely severe bending fatigue at the time of transportation and the like, various attempts have been made, and linear low-density polyethylene layers / adhesive layers / EVOH layers / Laminate of adhesive / linear low-density polyethylene (hereinafter abbreviated as LLDPE) layer (JP-A-60-161146), LLDPE layer / adhesive layer / EVOH layer / adhesive layer / ethylene-vinyl acetate Laminated body of copolymer resin layer, biaxially oriented nylon layer, or biaxially oriented polypropylene (Japanese Patent Laid-Open No. 60-168649), surface layer / carboxylic acid-modified LLDPE / EVOH
A laminate of a layer / a carboxylic acid-modified LLDPE / surface layer (JP-A-60-24205) has been proposed.

[0005]

However, the laminated film using EVOH as an intermediate layer as described above has a high gas barrier that can withstand long-term storage and transportation, although the bending fatigue resistance is improved. Sex is still inadequate. The reason for this is that in manufacturing the inner container, it is necessary to make a liquid injection port in the inner container, and a punched hole is made in the laminated film. At this time, the EVOH layer has little flexibility because the EVOH layer has little flexibility. Cracks are generated, and the cracks grow due to stress during transportation or the like, which ultimately results in impaired gas barrier properties.

[0006]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the present inventors have found that (i) an ethylene content of 25 to 55 mol% and a vinyl acetate component of (Ii) EVOH having a saponification degree of 95 mol% or more;
A resin composition (A) comprising a mixture with a polyamide / polyether block copolymer was used as an intermediate layer, an adhesive layer was provided on both sides of the intermediate layer, and a surface layer was provided outside the adhesive layer. The inventor of the present invention has found that the inner container for a bag-in-box can maintain a good gas barrier property even during long-term transportation without any cracks during the production of the liquid inlet. Hereinafter, the present invention will be described in detail.

[0007] The EVOH (i) used in the present invention has an ethylene content of 25 to 55 mol%, preferably 28 to 48 mol%.
Mol%, the degree of saponification of the vinyl acetate component is 95 mol% or more,
It should preferably be at least 98 mol%.
If the ethylene content is less than 25 mol%, the oxygen barrier property at high humidity decreases, while if it exceeds 55 mol%, physical properties such as oxygen barrier property deteriorate. On the other hand, if the saponification degree is less than 95 mol%, the oxygen barrier property and the moisture resistance are reduced. Among these EVOHs, the intrinsic viscosity (measured at 30 ° C. as a 15% aqueous phenol solution) is 0.6 to 1.5 dl / g, preferably 0.7 to 1.5 dl / g.
1.9 dl / g is suitably used in terms of the mechanical strength of the molded product.

The EVOH is a small amount of α-olefins such as propylene, isobutene, α-octene, α-dodecene and α-octadecene, and unsaturated carboxylic acids as long as the properties such as transparency and gas barrier properties are not impaired. Alternatively, a comonomer such as a salt thereof, a partial alkyl ester, a complete alkyl ester, a nitrile, an amide, an anhydride, an unsaturated sulfonic acid or a salt thereof may be contained. Furthermore,
The polyamide / polyether block copolymer (ii) is obtained by condensing a polyether / diol block and a dicarboxylic acid type polyamide block, and is represented by the following chemical formula 1.

[0009]

[Formula 1] (Here, PA is a polyamide block, PE is a polyether block, and n is a positive integer.) As the polyamide block, nylon 6, nylon 1
0, nylon 6-6, nylon 11, nylon 12, nylon 6-10, nylon 6-12, nylon 6-1
0, nylon 6 / 6-6 copolymer, nylon 6-6 / 6
-10 copolymer, nylon 6-11, nylon 6-6 /
6-10 / 6 copolymer and the like.

As the polyether block, any polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polybutylene glycol and polytetramethylene glycol is used. The weight ratio of the polyamide block / polyether block is 80 / 20-
Those of about 20/80 are practical. In the present invention, the mixing ratio of (i) and (ii) is (i) / (ii) on a weight basis.
= 98/2 to 10/90, preferably 90/10 to 30
/ 70. (I) / (ii) is 98/2 or more
In this case, the obtained molded product is liable to generate pinholes and the like.
On the other hand, when the ratio is 10/90 or less, the oxygen barrier property is low and the practicability is poor. In addition, as the resin component of the intermediate layer of the present invention, in addition to the above (i) and (ii), a plasticizer (such as a polyhydric alcohol), a stabilizer, a surfactant, a crosslinkable substance (an epoxy compound, a polyvalent metal). Salts, inorganic or organic polybasic acids or their salts, etc.), fillers, coloring agents, fibers (glass fibers, carbon fibers, etc.) as reinforcing agents, etc. can be added in appropriate amounts.

Further, other thermoplastic resins may be blended in an appropriate amount. Examples of such thermoplastic resins include polyolefins (low / medium / high density polyethylene, isotactic polypropylene, ethylene-propylene copolymer, ethylene-propylene). A diene copolymer, ethylene and carbon number 4
The above copolymer with α-olefin, ethylene-vinyl acetate copolymer or a saponified product thereof having an ethylene content of 25
Mol% or less or 55 mol or more, ethylene-acrylate copolymer, ionomer, polybutene, polypentene, etc.) or modified polyolefin, polyamide such as nylon 6/6 obtained by graft-modifying these with an unsaturated carboxylic acid or a derivative thereof. -6 copolymer,
Polyvinyl chloride, polyvinylidene chloride, polyester,
Examples include polystyrene, polyacrylonitrile, polyacetal, and a melt-moldable polyvinyl alcohol-based resin.

The inner container for a bag-in-box according to the present invention comprises:
It comprises at least a five-layer laminate of a surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer, and the surface layer has a density of 0.86 to 0.95 g / cm ³ (20 ° C.) The ethylene-α-olefin copolymer is preferred. The density here is a value measured according to JIS K 6760 at 20 ° C. When the density is smaller than the above range,
The mechanical properties of the laminate are insufficient, or blocking occurs. On the contrary, when it is large, the bending fatigue resistance becomes insufficient, which is not preferable. The ethylene-α-olefin is a copolymer of ethylene and 18 or less carbon atoms such as butene-1, pentene-1,4-methylpentene-1, hexene-1, and octene-1. Among these, an ethylene-α-olefin copolymer using an α-olefin having 4 to 8 carbon atoms is preferably used.

Further, as the adhesive resin used for the adhesive layer, a density modified with an unsaturated carboxylic acid or an anhydride thereof is 0.86 to 0.95 g / cm ³ (measurement conditions are as described above. Ethylene-α-olefin copolymer) is preferable, and can be obtained by copolymerizing or graft-modifying the same resin as described in the above surface layer with an unsaturated carboxylic acid or an anhydride thereof. Of course, the modification includes a blend of an unmodified ethylene-α-olefin copolymer and an unsaturated carboxylic acid or an anhydride thereof. As unsaturated carboxylic acids or anhydrides thereof, maleic acid,
Maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride and the like can be mentioned, and among them, maleic anhydride is preferably used.

At this time, the amount of the unsaturated carboxylic acid or anhydride contained in the ethylene-α-olefin copolymer is preferably from 0.01 to 10% by weight, more preferably from 0.1 to 3% by weight. It is. If the content in the modified product is small, the adhesive strength between the intermediate layer and the surface layer is reduced. If the content is large, a crosslinking reaction is caused, and the moldability is deteriorated.
The thickness of each layer of the laminate of the surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer of the present invention is 10 to 10 respectively.
600μ / 2-50μ / 1-100μ / 2-50μ / 1
0 to 600 μm, preferably 30 to
200 μ / 5 to 10 μ / 5 to 30 μ / 5 to 10 μ / 30
~ 200μ.

The most important feature of the present invention is that the intermediate layer contains an EVOH containing a polyamide / polyether block copolymer.
And the laminate of the present invention using the EVOH for the intermediate layer has a surface layer / adhesive layer / intermediate layer (A)
Not only the constitution of the adhesive layer / surface layer but also a further layer outside the surface layer to form a surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer / adhesive layer / surface layer , Surface layer / adhesive layer /
Surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer /
It is also possible to form a laminate of six or more layers such as an adhesive layer / surface layer. Further, using a nylon layer, a surface layer / adhesive layer / nylon layer / intermediate layer (A) / adhesive layer / surface layer, surface layer / adhesive layer / nylon layer / intermediate layer (A) / nylon layer / It is also possible to form a laminate of an adhesive layer / surface layer, a surface layer / adhesive layer / nylon layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer, etc. As the resin of the nylon layer to be used, nylon 6, nylon 6/6
-6, nylon 12, amorphous nylon, or blends thereof.

The surface layer and the adhesive layer of the laminate of the present invention may have an antioxidant, a slip agent, a hydrotalcite, an antistatic agent, a plasticizer, a coloring agent, etc. for improving the moldability. Can be added in a range that does not impair the effects of the present invention. The inner container for a bag-in-box of the present invention can be manufactured mainly by a heat sealing method and a blow molding method. In the heat sealing method, a film for the intermediate layer and a film for the surface layer formed by the inflation method or the extrusion method is laminated by dry laminating through an adhesive layer or a laminate obtained by laminating each layer by a coextrusion method or the like. As it is, or as necessary, double or triple overlapping, punch out a hole for attaching a liquid stopper to the liquid inlet, and seal the liquid inlet to the hole by heat sealing in advance. Let it fuse. At this time, the laminated body and another laminated body which has not been subjected to the punching process are combined and heat-sealed in four directions to obtain a bag-in-box or other inner container. In the blow molding method, the cylindrical laminated body extruded from an extruder is molded by clamping with a die. The sealing plug of the liquid inlet is previously molded by injection molding, set in a mold, and fused with a molding container during blow molding. Thereafter, the liquid inlet is opened.

[0017]

The inner container for a bag-in-box of the present invention uses an EVOH layer containing a polyamide / polyether block copolymer for the intermediate layer, so that cracks are generated in the punching step at the time of manufacturing the inner container. Thus, a bag-in-box inner container having excellent long-term gas barrier properties can be obtained.

[0018]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” mean on a weight basis unless otherwise specified. Example 1 Using a three-type five-layer coextrusion apparatus, the intermediate layer was made of EVOH (ethylene content: 36 mol%, degree of saponification: 99.3 mol%).
Part, a resin composition layer (A-1) containing 30 parts of a nylon 6 / polytetramethylene glycol block copolymer (block copolymerization ratio 70/30), and both outer layers were 2.5 g / MI (melt index). 10 minutes (190 ° C, load 2
160 g), a density of 0.890 g / cm ³ , an ethylene-1-butene random copolymer LLDPE (B-1) having an ethylene content of 90 mol%, and an anhydride having an MI of 3.0 between the intermediate layer and both outer layers. LLDPE with 0.5% maleic acid content
(B-1) / (C-1) / (A-1) / (C-1) / comprising the adhesive resin layer (C-1) comprising (B-1).
(B-1) is 35μ / 10μ / 10μ / 10μ / 35μ
Was obtained under the following coextrusion molding conditions.

Co-extrusion molding conditions : Extruder (A): 30 mmф, screw; full flight type, L / D; 28 Temperature condition (° C.): supply section; 180, compression section; 200, measuring section; : 1.5 kg / hr Extruder (B): 30 mmф, screw; full flight type, L / D; 26 temperature condition (° C): supply section; 160, compression section; 200, measuring section; 220 discharge amount: 3 0.0 kg / hr Extruder (C): 40 mmф, screw; full flight type, L / D; 24 Temperature condition (° C.): supply part; 200, compression part; 210, measuring part; 210 discharge amount: 10.0 kg / Hr Feed block temperature: 220 ° C Die temperature: 220 ° C

The obtained laminated film (500 mm × 70
0 mm) were stacked, and a hole (diameter: 43 mm) for liquid injection was made by a punching machine. Next, a laminated film without holes (500 mm × 700 mm laminated) was superposed on the laminated film and heat-sealed on all sides to produce a bag-in-box inner container. At that time, a high-density polyethylene sealing stopper was attached to the hole for liquid injection and heat-sealed around and tightly fixed. Next, place the inner container in a cardboard box, and put water therein for about 18 hours.
A running transport test of about 2000 km in liters was conducted. After the test, the state of the laminated film around the sealing stopper of the inner container was visually observed with an SEM (electron microscope, 500 times). The oxygen permeability of the inner container before and after the test (cc /
The air / bag / day) was examined under the conditions of 20 ° C. and 65% RH using an oxygen permeability meter (OX-TRAN 10/50) manufactured by Modern Control.

Examples 2-3 Using the intermediate layer, adhesive layer and surface layer shown in Table 1, an inner container was prepared and evaluated in the same manner as in Example 1. Comparative Example 1 In Example 1, the intermediate layer was provided with an ethylene content of 28 mol%,
Except for changing to EVOH having a saponification degree of 99.5 mol%, a laminated film of five layers was obtained in the same manner as in Example 1, and an inner container was produced and evaluated. Table 1 shows the evaluation results of the examples and the comparative examples.

[0022]

[Table 1] Layer structure ¹⁾ Evaluation items Intermediate layer Surface layer Adhesive layer SEM observation Oxygen permeability ²⁾ Example 1 A-1 B-1 C-1 No abnormality 0.20 / 0.21 Example 2 A-2 B-2 C-2 No abnormality 0.10 / 0.15 Example 3 A-3 B-3 C-3 No abnormality 1.20 / 1.20 Comparative example 1 A-4 B-1 C-1 Crack generation 0.08 / 200 <

1) Each constituent resin is as follows. A-1: 70 parts of EVOH having an ethylene content of 36 mol% and a saponification degree of 99.3 mol%, and a nylon 6 / polytetramethylene glycol block copolymer (block copolymerization ratio: 70)
A-30; 80 parts of EVOH having an ethylene content of 28 mol% and a saponification degree of 98.9 mol% and a nylon 66 / polypropylene glycol block copolymer (block copolymerization ratio 60/30).
40) 20 parts of A-3; 50 parts of EVOH having an ethylene content of 36 mol% and a saponification degree of 99.4 mol%, and a nylon 11 / polyethylene glycol block copolymer (block copolymerization ratio: 40/6)
0) Incorporation of 50 parts A-4; only EVOH having an ethylene content of 28 mol% and a saponification degree of 99.5 mol%

B-1: MI 2.5 g / 10 min, density 0.
890 g / cm ³ , ethylene-1-butene random copolymer having an ethylene content of 90 mol% B-2; MI 4.0 g / 10 min, density 0.872 g / c
m ³ , ethylene-1-butene random copolymer having an ethylene content of 82 mol% B-3; MI 0.8 g / 10 min, density 0.864 g / c
m ³ , an ethylene-propylene copolymer C-1 having an ethylene content of 80 mol%; a product obtained by grafting 0.5% of maleic anhydride onto the above B-1. C-2: 90 parts of B-1 blended with 10 parts of the above B-2 grafted with 2.5% maleic anhydride. C-3: Maleic anhydride grafted to B-3 above at 3%. 2) Oxygen permeability is represented by values before and after the test.

[0025]

The inner container for a bag-in-box according to the present invention uses an EVOH layer containing a polyamide / polyether block copolymer for the intermediate layer. Thus, an inner container for a bag-in-box excellent in gas barrier properties can be obtained without generation of a gas barrier property, and can withstand the impact of long-time transportation or the like, which is extremely useful.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B65D 77/00-77/40

Claims (4)

(57) [Claims] 1. A saponified ethylene-vinyl acetate copolymer having an ethylene content of 25 to 55 mol% and a degree of saponification of a vinyl acetate component of 95 mol% or more, and (ii) a polyamide / polyether block copolymer. A resin composition (A) composed of a mixture with the coalescing agent, an intermediate layer, an adhesive layer provided on both sides of the intermediate layer, and a surface layer provided outside the adhesive layer; Box inner container. 2. The weight ratio of (i) and (ii) is (i) /
2. The bag-in-box inner container according to claim 1, wherein (ii) = 98/2 to 10/90. 3. The surface layer has a density of 0.86 to 0.95 g / c.
The inner container for a bag-in-box according to claim 1, comprising an ethylene-α-olefin copolymer having m ³ (20 ° C). 4. An adhesive layer modified with an unsaturated carboxylic acid or an anhydride thereof at a density of 0.86 to 0.95 g / cm.
^{3. The} inner container for a bag-in-box according to claim 1, comprising an ethylene-α-olefin copolymer of ³ (20 ° C.).