JP3169280B2 - 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 property 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. Therefore, in applications intended for packaging materials, gas barrier properties, aroma retention properties, and food discoloration prevention properties can be achieved by laminating films of low-density polyethylene, polypropylene, nylon, polyester, etc. on both sides of the EVOH film. It is used in various packaging applications while compensating for the drawbacks of EVOH, such as drop strength, thermoformability, and moisture resistance, while maintaining the characteristics of EVOH such as.

[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 which can withstand long-term storage and transportation, although its bending fatigue resistance is improved. Sex is still inadequate. The cause is that when manufacturing the inner container from the laminated film, it is necessary to make a liquid injection port in the inner container, and a punch hole is made in the laminated film.
At this time, since the EVOH layer has little flexibility, cracks occur in the EVOH layer, and the cracks grow due to stress during transportation or the like, which eventually results in impairing gas barrier properties.

[0006]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, (i) the EVOH contained 50 to 99.5% by weight, (ii) )
An ethylene copolymer having a density of 0.90 to 0.94 g / cm ³ is 0.4 to 50% by weight, and (iii) a graft reaction of an ethylenically unsaturated carboxylic acid or a derivative thereof to a polyolefin resin, and further a polyamide Is reacted at a rate of 0.1 to 15% by weight of E
The bag-in-box inner container in which the layer (A) of the VOH composition is used as an intermediate layer, an adhesive layer is provided on both sides of the intermediate layer, and a surface layer is provided outside the adhesive layer, The inventors have found that no cracks occur during the production of the inlet and that good gas barrier properties can be maintained even during long-term transportation, and the present invention has been completed. Hereinafter, the present invention will be described in detail.

The resin composition of the intermediate layer used in the present invention comprises the above (i), (ii) and (iii).
The OH used has an ethylene content of 20 to 60 mol%, preferably 25 to 55 mol%, and a saponification degree of 90 mol% or more, preferably 95 mol% or more. If the ethylene content is less than 20 mol%, the gas barrier property at high humidity decreases, while if it exceeds 60 mol%, sufficient gas barrier property cannot be obtained. If the saponification degree is less than 90 mol%,
Gas barrier properties and moisture resistance are reduced. Among such EVOHs, those having an intrinsic viscosity (measured in an aqueous solution containing 15% phenol at 30 ° C.) of 0.7 to 1.5 dl / g, preferably 0.8 to 1.3 dl / g, are mechanical. It is suitable in terms of strength and workability.

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. Also,
The ethylene copolymer (ii) is a low-density polyethylene or linear low-density polyethylene which is easily available as a commercial product, and further includes an ethylene-vinyl acetate copolymer, an ethylene-acrylate copolymer and the like. In any case, the density must be 0.90 to 0.94 g / cm ³ (20 ° C.) (value measured at 20 ° C. according to JIS K 6760). Medium-density polyethylene and high-density polyethylene other than such polyethylene are difficult to obtain the effects of the present invention.

[0009] Among (ii), the melt index (M
I) (210 ° C., load 2160 g) 0.3 to 60 g /
Those of about 10 minutes are frequently used. In the present invention, in order to make the compatibility between (i) and (ii) good, the combination of (iii) is essential. (Iii) is a graft polymer obtained by subjecting a polyolefin resin to a graft reaction with an ethylenically unsaturated carboxylic acid or a derivative thereof, and further reacting the carboxylic acid or a derivative thereof with a polyamide. The graft polymer is obtained by dissolving or suspending a polyolefin resin in an appropriate solvent, or activating a polyolefin resin chain with a peroxide or a diazo initiator in a molten state, and adding an ethylenically unsaturated carboxylic acid to the chain. It is produced by grafting an acid or a derivative thereof to obtain a polymer, and mixing the polymer and a polyamide in a molten state. In the case of such a reaction, Brabender, bath blender, single screw extruder,
A Weiner or Friedler type twin screw extruder or the like is used.

The degree of polymerization of the polyolefin resin used is from 350 to 45000, preferably from 500 to 1000.
A value of about 0 is selected. Melt index (MI)
(210 ° C., load 2160 g) as 0.1 to 50 g
About / 10 minutes is practical. The reaction ratio between the polyolefin-based resin and the ethylenically unsaturated carboxylic acid or its derivative is from 100 / 0.05 to 100/10, preferably from 100 / 0.5 to 100/3, by weight. 100 /
If it is less than 0.5, the effect of improving the compatibility will be insufficient, and 1
If it is more than 00/10, the viscosity at the time of molding becomes large, and the practicability is poor. The degree of polymerization of the polyamide is 80 to 1000,
Preferably about 100 to 500 is practical, and the reaction ratio is desirably 0.01 to 1 mol, preferably 0.05 to 0.9 mol per carboxyl group.

Examples of the polyolefin resin include LLDPE, low-density / high-density polyethylene, ionomer, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, and the like. In particular, LLDPE, low-density polyethylene, ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer are practically important. The ethylenically unsaturated carboxylic acid or a derivative thereof to be grafted to the trunk polymer is an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, or an anhydride or a half ester thereof. Etc.
The polyamide is produced by a known method such as polyaddition of lactam, polycondensation of aminocarboxylic acid, and polycondensation of diamine and dicarboxylic acid.

As the polyamide raw material, specifically,
Lactams such as ε-caprolactam, enantholactam, caprylactam, lauryl lactam, α-pyrrolidone, α-piperidone, 6-aminocaproic acid, 7-
Ω-amino acids such as aminoheptanoic acid, 9-aminononanoic acid, 11-aminoundecanoic acid, adipic acid, glutaric acid, pimelic acid, spearic acid, azelaic acid, sebacic acid, undecandionic acid, dodecadionic acid, hexadecadione Acid, hexadecenedionic acid, eicosandioic acid, eicosadienedioic acid, diglycolic acid,
Dibasic acids such as 2,2,4-trimethyladipic acid, xylylenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid and isophthalic acid, hexamethylenediamine, tetramethylenediamine, nonamethylenediamine, undecamethylene Diamines such as diamine, dodecamethylenediamine, 2,2,4 (or 2,4,4) -trimethylhexamethylenediamine, bis- (4,4′-aminocyclohexyl) methane, and meta-xylylenediamine Can be Monoamines such as laurylamine and oleylamine can also be used as appropriate for the purpose of controlling the molecular weight.

In the resin composition (A) for the intermediate layer according to the present invention, the mixing ratio of (i), (ii) and (iii) is such that (i) is 50 to 50%.
99.5% by weight, preferably 60-95% by weight, (ii)
Is 0.4 to 50% by weight, preferably 4.5 to 35, (ii)
i) must be between 0.1 and 15% by weight, preferably between 0.5 and 10% by weight. When (i) is 50% by weight or less or (ii) is 50% by weight or more, the oxygen barrier property is low. On the other hand, when (i) is 99.5% by weight or more or (ii) is 0.4% by weight or less, stretching is performed. Lacks in properties and flexibility, and tends to cause unevenness in film thickness. When (iii) is 0.1% by weight or less, the compatibility between (i) and (ii) becomes poor, and the effect of the present invention is hardly obtained. When it is 15% by weight or more, long-run moldability deteriorates, which is disadvantageous. is there.

Further, in the present invention, a plasticizer (polyhydric alcohol, etc.), a stabilizer, a surfactant, a crosslinkable substance (epoxy) may be added to the resin composition (A) as long as the effects of the present invention are not impaired. Compounds, polyvalent metal salts, inorganic or organic polybasic acids or salts thereof), fillers, coloring agents, fibers (glass fibers, carbon fibers, etc.) as reinforcing materials, hydrotalcite, etc., should be mixed in appropriate amounts. Can be. Also, various other thermoplastic resins may be blended in an appropriate amount. Examples of such other thermoplastic resins include polyolefins other than (ii), modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or derivatives thereof, and polyamides. , Polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, polycarbonate, and melt-moldable polyvinyl alcohol 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 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 the intermediate layer contains a specific polyolefin resin and a graft polymer.
Due to the use of OH, the laminate of the present invention using EVOH for the intermediate layer is not limited to the structure of the surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer. Surface layer / adhesive layer / intermediate layer (A) with additional layer outside
/ Adhesive layer / surface layer / adhesive layer / surface layer, surface layer / adhesive layer / surface layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer / adhesive layer / surface layer, etc. It is also possible to form a laminate of six or more layers. Furthermore, a surface layer using a nylon 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 / Adhesion It is also possible to form a laminate of an agent layer / nylon layer / adhesive layer / intermediate layer (A) / adhesive layer / surface layer, and the like. Nylon 6-66, nylon 12, amorphous nylon, or blends thereof.

The adhesive layer and the surface layer of the laminate of the present invention may further include an antioxidant for improving moldability and physical properties.
A slip agent, hydrotalcites, an antistatic agent, a plasticizer, a colorant, and the like can be added as long as the effects of the present invention are not impaired. 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 laminated body obtained by dry laminating a film for an intermediate layer and a film for a surface layer formed by an inflation method or an extruding method via an adhesive layer or a laminated body obtained by laminating each layer by a coextrusion method or the like. As it is, or as a double or triple overlap as necessary, a hole for sealing the liquid inlet is punched out, and a sealing plug for the liquid inlet previously molded by injection molding is melted into the hole by a heat sealing method. To wear. 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 stopper of the liquid inlet is previously molded by injection molding and set in a mold, and is fused to a molding container during blow molding. Thereafter, the liquid inlet is opened.

[0020]

The inner container for a bag-in-box of the present invention uses an EVOH layer containing a specific polyolefin-based resin and a graft polymer in the intermediate layer, so that cracks occur in the punching step in the production of the inner container. An inner container for a bag-in-box excellent in gas barrier properties for a long period of time without generation is obtained.

[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. below,
(I), (ii), and (iii) each material was prepared. (I) EVOH (E-1 to 4) E-1; ethylene content 30 mol%, degree of saponification 99.5 mol%, MI (210 ° C., load 2160 g, the same applies hereinafter) 2
g / 10 min E-2; ethylene content 32 mol%, saponification degree 99.0 mol%, MI 4 g / 10 min E-3; ethylene content 40 mol%, saponification degree 99.2 mol%, MI 12 g / 10 min E-4; ethylene content 40 mol%, degree of saponification 96.0 mol%, MI 8 g / 10 min

(Ii) Polyolefin resin (P-1 to 3) P-1; polypropylene P-2; ethylene-propylene block copolymer having an ethylene content of 12 mol% P-3; ethylene having an ethylene content of 80 mol% 1-butene random copolymer (iii) graft polymer (G-1 to 3) G-1: 2 parts of maleic anhydride was grafted onto 100 parts of an ethylene-propylene block copolymer having an ethylene content of 12 mol%, and 6 parts of 6-nylon grafted polymer G-2; 100 parts of ethylene-propylene block copolymer having an ethylene content of 12 mol% was grafted with 2.5 parts of maleic anhydride, and 6-66-nylon 10 Part of the graft polymer G-3; 100 parts of an ethylene-1-butene random copolymer having an ethylene content of 80 mol% and anhydrous maleic anhydride 0.5 parts by grafting a graft polymer obtained by reacting further 12 nylon 5 parts (Note that grafting of maleic anhydride, the catalyst 2,5-dimethyl-2,5 (t-butylperoxy)
The reaction was carried out in an extruder using hexane. )

Example 1 Using a three-type, five-layer coextrusion apparatus, the intermediate layer was made of EVOH
(E-1) 90 parts, polyolefin resin (P-1) 5
Part (A-1) and both outer layers of the resin composition containing 5 parts by weight of the polymer (G-1) and 5.0 parts by weight of the graft polymer (G-1) at a melt index of 5.0 g / 10 minutes (210 ° C., load 2160
g), an ethylene-1-butene random copolymer LLDP having a density of 0.890 g / cc and an ethylene content of 90 mol%
E (B-1), LLDPE (B-1) having a MI of 3.0 between the intermediate layer and both outer layers and a maleic anhydride content of 0.5%
An adhesive resin layer (C-1) consisting of:
1) / (C-1) / (A-1) / (C-1) / (B-
1) A five-layer co-extruded laminated film having a constitution of 35 μ / 10 μ / 10 μ / 10 μ / 35 μ was obtained under the following co-extrusion 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; 220 discharge amount: 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 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 permeation amount (cc / cc) of the inner container before and after the test
The air / bag / day) was examined under the conditions of 20 ° C. and 65% RH using an oxygen permeation meter (OX-TRAN 10/50) manufactured by Modern Control.

Examples 2 to 4 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 and 2 Using the intermediate layer, the adhesive layer, and the surface layer shown in Table 1, an inner container was produced 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 0.10 / 0.15 Example 2 A-1 B-2 C-2 No abnormality 0.10 / 0.12 Example 3 A-2 B-3 C-3 No abnormality 0.16 / 0.20 Example 4 A-3 B-4 C-3 No abnormality 0.22 / 0.30 Comparative Example 1 A-4 B-1 C-1 * 0.1 / 30.0 Comparative Example 2 A-5 B-2 C-2 Cracking 0.31 / 13.0

1) Each constituent resin is as follows. A-1; a resin composition comprising 90 parts of EVOH (E-1), 5 parts of a polyolefin resin (P-1) and 5 parts of a graft polymer (G-1) A-2; EVOH (E-2) 60 parts, polyolefin-based resin (P-2) 25 parts and graft polymer (G-2) 1
Resin composition containing 5 parts A-3; 75 parts EVOH (E-3), 20 parts polyolefin resin (P-3), and graft polymer (G-3) 5
A-4; only the above (E-1) A-5; only the above (E-4)

B-1: MI 5.0 g / 10 min, density 0.
890 g / cm ³ , ethylene-1-butene random copolymer having an ethylene content of 90 mol% B-2; MI 8.0 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 1.6 g / 10 min, density 0.864 g / c
m ³ , ethylene-propylene copolymer B-4 having an ethylene content of 80 mol%; MI 4.0 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. * Liquid leakage was observed around the liquid inlet.

[0030]

The inner container for a bag-in-box of the present invention uses an EVOH layer containing a specific polyolefin resin and a graft polymer for the intermediate layer. An inner container for a bag-in-box having excellent gas barrier properties without cracks can be obtained, and can withstand the impact of long-time transportation or the like, and is extremely useful.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-161146 (JP, A) JP-A-60-168649 (JP, A) JP-A-60-242054 (JP, A) JP-A-4- 164943 (JP, A) JP-A-3-227339 (JP, A) JP-A-3-227345 (JP, A) JP-A-4-1644941 (JP, A) JP-A-3-227344 (JP, A) JP-A-3-227347 (JP, A) JP-A-3-227346 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B65D 77/00-77/40 B32B 1/00 -35/00

Claims (3)

(57) [Claims] (1) 50 to 99.5% by weight of saponified ethylene-vinyl acetate copolymer; (ii) density of 0.90
0.4 to 50% by weight of an ethylene copolymer of about 0.94 g / cm ³ (20 ° C.), (iii) a graft reaction of an ethylenically unsaturated carboxylic acid or a derivative thereof to a polyolefin resin, and further polyamide (A) of a saponified ethylene-vinyl acetate copolymer composition in which the graft polymer obtained by the reaction of
As an intermediate layer, an adhesive layer is provided on both sides of the intermediate layer, and a surface layer is further provided outside the adhesive layer. 2. The surface layer has a density of 0.86 to 0.95 g /
The inner container for a bag-in-box according to claim 1, comprising an ethylene-α-olefin copolymer having a cm ³ (20 ° C). 3. An adhesive layer having a density of 0.86 to 0.95 g / cm ³ modified with an unsaturated carboxylic acid or an anhydride thereof.
The inner container for a bag-in-box according to claim 1, comprising an ethylene-α-olefin copolymer (20 ° C).