JP3173746B2 - 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, and as a result, have found that the ethylene content is 15 to 50 mol% and the saponification of the vinyl acetate component. 70 to 98% by weight of EVOH having a degree of 95 mol% or more, containing substantially no free isocyanate group in the molecule and containing 10 to 50% by weight of a urethane bond represented by Chemical formula 1,

Embedded image And the melt viscosity at a temperature of 200 ° C. is 1.0 × 10 ² to
5 × 10 ⁴ poise polyurethane elastomer 30-2
The resin composition (A) obtained by melting and mixing the weight% at 180 to 250 ° C. 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.

The EVOH used in the present invention has an ethylene content of 15 to 50 mol%, preferably 25 to 48 mol%,
A vinyl acetate component having a saponification degree of 95 mol% or more, preferably 98 mol% or more, is usually used. If the ethylene content is less than 15 mol%, the oxygen barrier property at high humidity decreases, while if it exceeds 50 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 such EVOHs, the intrinsic viscosity (measured at 30 ° C. as a 15% aqueous phenol solution) is 0.7 to 1.5 dl / g, preferably 0.8 to 1.3 d.
1 / 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. Further, the polyurethane elastomer to be mixed with the EVOH contains substantially no free isocyanate group in the molecule and contains 10 to 50% by weight of a urethane bond represented by Chemical formula 1,

Embedded image And the melt viscosity at a temperature of 200 ° C. is 1.0 × 10 ² to
Limited to 5 × 10 ⁴ poise.

When a polyurethane elastomer containing a free isocyanate group is used, a flow mark,
Weld marks tend to be generated to impair the appearance of the molded article. If the urethane bond ratio is less than 10%, EVO
The compatibility with H is inferior. On the other hand, if it exceeds 50%, the impact resistance is not sufficiently improved, which is not preferable. Further, when the melt viscosity is out of the above range, there is a problem that compatibility with EVOH is poor and an effect of improving impact resistance cannot be expected. However, there is no difference in effect if the amount of free isocyanate groups is as small as about 1% or less. The melt viscosity can be adjusted by adding a chain extender or changing the molecular weight of the polyol component. As the chain extender, glycol, diamine and the like are generally used, and 1,4-butylene glycol, P-xylene glycol and the like are preferable.

[0010] Such polyurethane elastomers
(B) A compound obtained by a normal urethane reaction of a polyisocyanate compound and a (b) polyol component,
Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, Lysine diisocyanate, modified diisocyanate thereof, bifunctional isocyanate such as hydrogenated diisocyanate, and a buret type polyisocyanate compound obtained by reacting each diisocyanate compound with water;
Examples include trifunctional isocyanate compounds such as 2,6-diisocyanate hexanoate and multimers obtained by isocyanurating each of the above-mentioned diisocyanate compounds, and these may be used alone or in combination of two or more. .

(B) The polyol component includes ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol,
Tetraethylene glycol, dipropylene glycol,
1,4-butanediol, 1,6-hexanediol,
Neopentyl glycol, cyclohexane dimethanol, hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, polycaprolactone, trimethylolethane, trimethylolpropane,
Polytrimethylolpropane, pentaerythritol,
Examples include polypentaerythritol, sorbitol, mannitol, glycerin, polyglycerin and the like.
Further, as the polyester polyol, the above-mentioned reaction product of the polyhydric alcohol and the polybasic acid is used, and the hydroxyl value is 60 to 600 KOH
mg / g is used.

Examples of the polybasic acid include maleic anhydride, maleic acid, fumaric acid, itaconic anhydride, itaconic acid, phthalic anhydride, phthalic acid, terephthalic acid, isophthalic acid, heptic acid, adipic acid and tetrahydrophthalic anhydride. Used. Among such polyurethane elastomers, urethane compounds of polyethers such as polyethylene glycol and polypropylene glycol, and urethane compounds of polyester polyols of adipic acid, azelaic acid, ethylene glycol and alkylene oxide can be suitably used in practical use.

The EVOH and the polyurethane elastomer are mixed at a ratio of 70:30 to 98: 2 by weight. If the ratio of the polyurethane elastomer is too large, the hardness and rigidity of the molded product are reduced. It is inappropriate. These two components are heated and melt-mixed at a temperature of 180 to 250 ° C., but the means is not particularly limited, and any known melt-mixing molding method using a usual extruder, injection molding machine or the like is employed. Is done. Further, as the resin component of the intermediate layer of the present invention, the above EVOH
Plasticizers (polyhydric alcohols, etc.), stabilizers, surfactants, crosslinkable substances (epoxy compounds, polyvalent metal salts, inorganic or organic polybasic acids or their salts, etc.), fillers, Fibers (glass fibers, carbon fibers, etc.) as coloring agents and reinforcing agents can be blended 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 copolymers with α-olefins, ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers, ionomers, polybutenes, polypentenes) or modifications obtained by graft-modifying these with unsaturated carboxylic acids or derivatives thereof Polyolefin, polyamide, for example, nylon 6/66 copolymer, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyacetal, melt-moldable polyvinyl alcohol-based resin, and the like.

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. Conversely, when it is large, the bending fatigue resistance becomes insufficient, which is not preferable. Further, ethylene-α-olefin refers to ethylene and butene-1, pentene-1,4-
It is a copolymer having 18 or less carbon atoms, such as 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 follows. 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.

The amount of the unsaturated carboxylic acid or anhydride contained in the ethylene-α-olefin copolymer at this time is preferably 0.01 to 10% by weight, more preferably 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 a specific E
Due to the use of the VOH / polyolefin-based resin melt-mixed composition, the laminate of the present invention using the EVOH for the intermediate layer comprises a surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer. Not only the structure but also a layer is provided 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 /
It is also possible to form a laminate of six or more layers such as an adhesive layer / intermediate layer (A) / adhesive layer / surface layer / 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 / Adhesive layer / Surface layer, Surface layer / Adhesive layer / Nylon layer / Adhesive layer / Intermediate layer (A) / Adhesive layer / Surface layer, etc. It is also possible to make a laminate of the following. In this case, as the resin of the nylon layer used, nylon 6, nylon 6 / 6-6,
Nylon 12, amorphous nylon, or a blend thereof.

Further, an antioxidant, a slip agent, hydrotalcites, an antistatic agent, a plasticizer, a coloring agent, etc. may be added to the surface layer and the adhesive layer of the laminate of the present invention in order to improve 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 flat film method, a laminate obtained by dry laminating via an adhesive layer or a laminate obtained by laminating each layer by a co-extrusion method or the like. The hole for attaching the sealing plug of the liquid injection port is punched out as it is, or when it is superimposed double or triple as necessary, and the sealing plug of the liquid injection port previously formed by injection molding is heat-sealed in the hole. To fuse. At this time, the laminate and another laminate that has not been subjected to the punching process are combined and heat-sealed in four directions to form a bag-in-box 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.

[0020]

The inner container for a bag-in-box according to the present invention is an EVO containing a specific polyurethane elastomer in the intermediate layer.
Since the H layer is used, an inner container for a bag-in-box excellent in gas barrier properties for a long period of time without cracks can be obtained in the punching step at the time of manufacturing the inner container.

[0021]

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. Production of Resin for Intermediate Layer (A) A polyurethane elastomer obtained by reacting 80 parts of EVOH having an ethylene content of 30 mol% and a saponification degree of 97.0 mol% with a polyethylene glycol-polypropylene glycol copolymer and hexamethylene diisocyanate ( 20 parts of a urethane bond (18.3%, melt viscosity at 200 ° C. is 5 × 10 ³ poise) were melt-mixed at 210 ° C. to obtain a resin for intermediate layer (A-1). Similarly, the following intermediate layer resins (A-2 to 10) were produced.

A-2: Obtained by reacting 90 parts of EVOH having an ethylene content of 45 mol% and a saponification degree of 99.5 mol% with a polyethylene glycol-polypropylene glycol copolymer and diphenylmethane-4,4'-diisocyanate. Polyurethane elastomer (urethane bond 1
8.3%, melt viscosity at 200 ° C. is 5 × 10 ³ poise), and 10 parts are melt-mixed. A-3; ethylene content 45 mol%, saponification degree 99.2
Polyurethane elastomer obtained by reacting 75 parts by mole of EVOH (75 parts by mole), a polyester polyol of adipic acid and propylene glycol, and hexamethylene diisocyanate (urethane bond 21.0%, melt viscosity at 200 ° C. is 1.0 × 10 ⁴ poise, 25 parts of free isocyanate group (0.2%) melt-mixed at 240 ° C.

A-4: A product obtained by increasing the degree of polymerization of the polyethylene glycol-polypropylene glycol copolymer in the production of (A-1) so that the urethane bond of the polyurethane elastomer is 3.0%. A-5: A product in which the amount of hexamethylene diisocyanate charged in the production of (A-1) was increased to make the urethane bond of the polyurethane elastomer 60%. A-6: A polyurethane elastomer having a melt viscosity of 5 × 10 poise by adding a small amount of water during the production of (A-1). A-7: The reaction time was increased in the production of (A-1), and the melt viscosity of the polyurethane elastomer was 6 × 10 ⁴
Poise. A-8: The one in (A-1), wherein the mixing ratio of EVOH and polyurethane elastomer was 60/40. A-9: The one in (A-1), wherein the mixed melting temperature of EVOH and the polyurethane elastomer was 280 ° C.

Example 1 Using a three-type, five-layer co-extrusion apparatus, the intermediate layer was made of the above (A-
The layer of 1) and both outer layers are MI (melt index) 2.5
g / 10 minutes (190 ° C, load 2160g), density 0.8
An ethylene-1-butene random copolymer LLDPE (B-1) having 90 g / cm ³ and an ethylene content of 90 mol%,
The adhesive layer between the intermediate layer and both outer layers was 3.0 g / 10 MI of (B-1) in which 0.5% of maleic anhydride was grafted.
Min (190 ° C., load 2160 g) modified LLDPE (C
(B-1) / (C-1) / (A-1)
/ (C-1) / (B-1) is 35 μ / 10 μ / 10 μ /
A five-layer coextruded laminated film having a constitution of 10 μ / 35 μ 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; 5 kg / hr Extruder (B): 30 mmф, screw; full flight type, L / D; 26 Temperature condition (° C.): supply unit: 160, compression unit; 200, measuring unit; 220 Discharge amount: 3.0 kg / hr Extruder (C): 40 mmф, screw; full flight type, L / D; 24 Temperature condition (° C.): supply section; 200, compression section; 210, measuring section; 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 and 3 Using the intermediate layer, the adhesive layer and the surface layer shown in Table 1, an inner container was prepared and evaluated in the same manner as in Example 1. Comparative Examples 1 to 7 Using the intermediate layer, the adhesive layer, and the surface layer shown in Table 1, an inner container was prepared and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results of the examples and the comparative examples.

[0027]

[Table 1] Lamination 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 0.08 / 0.08 Example 2 A-2 B-2 C-2 No abnormality 0.11 / 0.15 Example 3 A-3 B-3 C-3 No abnormality 0.30 / 0.30 Comparative example 1 A-4 B-1 C-1 Cracking 2.00 / 200 <Comparative Example 2 A-5 B-1 C-1 Cracking 0.10 / 200 <Comparative Example 3 A-6 B-1 C-1 〃 0.08 / 200 < Comparative Example 4 A-7 B-1 C-1 〃 0.13 / 200 <Comparative Example 5 A-8 B-1 C-1 No abnormality 130/130 Comparative Example 6 A-9 B-1 C-1 ** Comparative Example 7 A-10 B-1 C-1 Crack generation 0.08 / 200 <

1) Each constituent resin is as follows. A-1; the above (A-1) A-2; the above (A-2) A-3; the above (A-3) A-4; the above (A-4) A-5; (A-5) A-6; the above (A-6) A-7; the above (A-7) A-8; the above (A-8) A-9; the above (A-9) A -10; ethylene content of 30 mol%, saponification degree of 9
7.0 mol% EVOH only.

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 , ethylene-propylene copolymer B-4 having an ethylene content of 80 mol%; MI 2.0 g / 10 min, density 0.920 g / c
m ³ , an ethylene-4-methylpentene-1 copolymer having an ethylene content of 97 mol% C-1; 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. * During the production of the laminate, a large amount of gel was generated, and molding of the laminate was impossible.

[0030]

The inner container for a bag-in-box according to the present invention uses an EVOH layer containing a specific polyurethane elastomer for the intermediate layer, so that cracks are generated in the punching step at the time of manufacturing the inner container. Thus, an inner container for a bag-in-box having excellent gas barrier properties can be obtained, and can withstand the impact of long-time transportation or the like, and is extremely useful.

Claims (3)

(57) [Claims] 1. Ethylene having an ethylene content of 15 to 50 mol% and a saponification degree of a vinyl acetate component of 95 mol% or more.
70 to 98% by weight of a saponified vinyl acetate copolymer, containing substantially no free isocyanate group in the molecule.
Containing 10 to 50% by weight of a urethane bond represented by the following formula: And the melt viscosity at a temperature of 200 ° C. is 1.0 × 10 ² to
5 × 10 ⁴ poise polyurethane elastomer 30-2
The resin composition (A) obtained by melting and mixing the weight% at 180 to 250 ° C. 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. An inner container for a bag-in-box. 2. 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). 3. An adhesive layer modified with an unsaturated carboxylic acid or its anhydride 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.).