JPH0523185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a flexible laminated packaging material whose high gas barrier properties do not deteriorate even under extremely severe bending fatigue.

B. Prior Art The function of flexible laminated packaging materials is basically the preservation of the packaged items, that is, the prevention of deterioration, and for this purpose, the packaging materials are particularly required to have transport vibration strength and bending fatigue resistance. In particular, so-called bag-in boxes or bag-in cartons (hereinafter collectively referred to as bag-in boxes) include a thin inner container made of foldable plastic and an outer cardboard box that is stackable, portable, and printable. When used as an inner container of a combination container), a high degree of this property is required. The packaging material is made by laminating various plastic films that take advantage of the characteristics of each material.
For example, the most common combination is a base film for maintaining mechanical strength and a heat-sealable material, and the material is selected depending on the requirements of the packaged item. In particular, for applications where the base film's barrier properties against oxygen and other gases are unsatisfactory, a barrier layer with even higher gas barrier properties may be provided on the base film.
A method is adopted in which a heat-sealable material is laminated with this barrier layer as an intermediate layer and a thermoplastic resin layer as at least one outer layer.

For example, the basic material of conventional bag-in-box inner containers always has a heat-sealed part.
Although it is mainly made of heat-sealable polyethylene, especially soft polyethylene, bag-in-boxes have physical strength due to their foldability and liquid content, as mentioned above.
In particular, transportation vibration strength and bending fatigue resistance are required, and for this reason, ethylene-vinyl acetate copolymer resin is more preferably used, as it has good stress crack resistance. Furthermore, as the required performance becomes more sophisticated, when gas barrier properties such as oxygen are required, the inner container is made of a combination of nylon film, Saran-coated nylon film, aluminum-deposited nylon film, aluminum-deposited polyester film, etc. It is starting to be put into practical use. In order to provide high gas barrier properties, saponified ethylene-vinyl acetate copolymer (hereinafter referred to as EVOH),
Polyvinylidene chloride, aluminum foil, etc. are used. However, although these have excellent gas barrier properties, their mechanical strength is generally low, and they are not particularly resistant to bending fatigue. Therefore, it is used by being laminated between a base material layer with excellent mechanical strength and a heat-sealable material, but when used as a component of a bag-in-box inner container, for example, pinholes, Even at the stage where no cracks or pinholes are created in the component,
Due to cracks, pinholes, etc. that occur in the barrier layer used as an intermediate layer, the barrier properties deteriorate, so it is difficult to resist severe bending fatigue.
No material has been found that is unable to maintain excellent gas barrier properties and is practically satisfactory. The behavior of laminated packaging materials whose barrier layers are layers mainly composed of polyvinylidene chloride resin, aluminum foil, vapor-deposited resin layers made of metal, etc. is shown in, for example, Japanese Patent Laid-Open No. 7477/1983. In other words, when the packaging material is actually used, the gas barrier properties after transportation and handling of the packaged package are not always satisfactory, and the practical shelf life after secondary distribution, which is the most necessary, is often betrayed. is due to damage to the barrier layer located in the middle layer. EVOH resin is the best material for the intermediate layer provided to improve gas barrier properties, and is preferably used as a barrier material for various multilayer films and containers with multilayer structures. This is because this resin not only has outstanding gas barrier properties, but also has excellent transparency, oil resistance, printability, moldability, etc., and has extremely advantageous properties such as not impairing the properties of the base resin. This is because it has However, in fields where bending fatigue resistance is particularly required,
There are no examples of EVOH resin being satisfactorily used as a barrier layer in laminated packaging materials. In particular, we have found a bag-in-box that satisfies this requirement by using EVOH resin in the inner container of a bag-in box that has gas barrier properties such as oxygen, which is strongly required to withstand bending fatigue due to transportation vibrations as mentioned above. One of the important issues was the development of flexible laminated packaging materials with excellent barrier properties and bending fatigue strength that can withstand transportation vibrations.

Furthermore, JP-A-50-86579 describes a package consisting of a polyolefin resin layer and an EVOH layer, in which an ethylene-acrylate copolymer is added to at least one layer to firmly adhere the two layers. Also, in Japanese Patent Application Laid-open No. 50-69162,
These publications describe a laminate in which a polyethylene layer or an ethylene-vinyl acetate copolymer layer is laminated on a layer containing EVOH and an ethylene-vinyl acetate copolymer, and the two are firmly adhered. The obtained packaging body has excellent bending fatigue resistance, and furthermore, it is possible to use it as a constituent material of a bag-in-box inner container.
There is no mention of the fact that a packaging material with excellent bending fatigue resistance can be obtained by particularly providing linear low-density polyethylene in the surface layers on both sides of the EVOH layer.

Furthermore, in Japanese Patent Application Laid-open No. 60-161146,
It is stated that a packaging material with excellent bending fatigue resistance can be obtained by providing linear low-density polyethylene layers on both sides of the EVOH layer. If it is too thick, the bending fatigue resistance will not be sufficient, and in order to achieve sufficiently good bending fatigue resistance, it is necessary to make the intermediate layer thinner.
Therefore, there was a problem that gas barrier properties were not sufficient.

C. Problems to be Solved by the Invention Although EVOH film has the above-mentioned excellent properties, it has a major drawback in that it is significantly inferior in bending fatigue resistance compared to films made of thermoplastic resins such as polyethylene, polypropylene, nylon, and thermoplastic polyester. In a multi-layer flexible packaging material that is laminated with the bending fatigue resistant resin layer and uses an EVOH resin layer as an intermediate layer, the bending fatigue resistance of the packaging material is determined by the bending fatigue resistant thermoplastic layer. The bending fatigue resistance is significantly lower than that exhibited by the resin alone, and pinholes occur in laminated packaging materials with less bending fatigue. The present inventors have improved the bending fatigue resistance of the above-mentioned EVOH film and the laminated packaging material containing the EVOH layer as an intermediate layer without sacrificing its excellent gas barrier properties, and improved the bending fatigue resistance and gas barrier properties. In order to develop an excellent flexible laminated packaging material, we have carried out extensive studies and have completed the present invention.

D Means for Solving Problems The present invention has a thin film having gas barrier properties as an intermediate layer, surface layers on both sides of the intermediate layer, and at least one of the surface layers is made of thermoplastic resin that can be heat-sealed. In a laminated packaging material in which each layer is arranged with an adhesive resin layer interposed therebetween, the intermediate layer has (A) an ethylene component content of 20 to 55 mol% and a vinyl acetate component content of 90%.
% or more of saponified ethylene-vinyl acetate copolymer and (B) a polyethylene polymer with a density of 0.91 to 0.86 g/cm ³ are grafted with an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride to form an ethylenic 0.02 to 0.3 equivalent of periodic law a or a to the unsaturated carboxylic acid or the carboxylic acid anhydride component
A metal compound consisting of a group metal hydroxide or salt is blended, or the metal compound and (C) have a density of
The mixture must contain 0.91 to 0.86 g/cm ³ of polyethylene polymer, and the amounts of (A), (B), and (C) satisfy the following formulas () and () on a weight basis. The present invention provides a laminated packaging material with excellent bending fatigue resistance.

0.40≧(B)+(C)/(A)+(B)+(C)≧0.05 () 1.0≧(B)/(B)+(C)≧0.01 () E Effects of the invention Various materials The superiority or inferiority of the bending fatigue resistance of laminated materials made of various materials can be determined by determining the dependence of the decrease in gas barrier properties on the number of bends in an evaluation test conducted using a so-called GELBO flex tester, the number of times of bending before pinholes occur, etc. This can be determined from the data. The present inventors investigated the relationship between the number of bends and the number of pinholes, the number of bends leading to the formation of pinholes, the number of bends in the process leading to the formation of pinholes, and the barrier using a Gelbo Flex Tester for the laminated film having the above structure. We measured the relationship with gender. As a result, surprisingly, the middle class
Compared to EVOH alone, although the gas barrier property hardly deteriorates, the bending fatigue resistance improves dramatically, and the gas barrier property hardly deteriorates until pinholes are observed. I found it. Therefore, even when an article that is susceptible to deterioration is packaged with the packaging material of the present invention and then transported, no pinholes will occur, so deterioration of the quality of the packaged item can be prevented.

In the present invention, (B) an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride is grafted onto a polyethylene polymer having a density of 0.91 to 0.86 g/cm ³ , and the ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride component is Periodic table a of 0.02 to 0.3 equivalent to
Alternatively, a metal compound consisting of a hydroxide or salt of a group A metal is blended, or a mixture of the metal compound and (C) a polyethylene polymer having a density of 0.91 to 0.86 g/cm ³ is (A). Ethylene component content 20
Although the mechanism by which the flex fatigue resistance and moldability of saponified ethylene-vinyl acetate copolymer resins with ~55 mol% and saponification degree of 90% or more are so markedly improved is not fully clear, the (A) ethylene component A saponified ethylene-vinyl acetate copolymer resin with a content of 20 to 55 mol% and a degree of saponification of 90% or more and (B) with a density of 0.91 to
A resin obtained by grafting an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride onto a polyethylene polymer of 0.86 g/cm ³ or (C) with a density of 0.91 to 0.86 g/cm ³
A mixture of a polyethylene polymer and a grafted polyethylene polymer is mixed with a metal compound consisting of a metal hydroxide or salt in an amount of 0.02 to 0.3 equivalent to the grafted ethylenically unsaturated carboxylic acid or carboxylic acid anhydride component. As a result, rheological effects in the molten system, chemical effects of impurities, etc. combine in a complex manner, improving formability,
It is presumed that the morphological properties of the resulting laminate intermediate layer were in a state favorable for exhibiting bending fatigue resistance.

F. More detailed description of the invention The present invention will be described in more detail below. (A) EVOH used as the intermediate layer in the present invention has an ethylene component content of 20 to 55 mol%, preferably 25 to 50 mol%, and a saponification degree of the vinyl acetate component of 90% or more. When the content of the ethylene component is less than 20 mol%, the molding temperature becomes close to the decomposition temperature, making molding difficult. If the content of the ethylene component exceeds 55 mol %, the gas barrier properties will be lowered and the gas barrier properties of the packaging material will be unsatisfactory, which is not preferable. Furthermore, if the degree of saponification of the vinyl acetate component is less than 90%, although the bending fatigue resistance is improved, the barrier properties are decreased, which is not preferable. This EVOH
The melt index (MI) measured by ASTM D-1238 at 190°C is between 0.1 and 25 g/10 minutes, preferably between 0.3 and 20 g/10 minutes. Furthermore, third components such as EVOH treated with boron compounds such as boric acid and sand, silicon-containing olefinic unsaturated monomers, α-olefin, and N-vinylpyrrolidone are copolymerized with ethylene and vinyl acetate, and then saponified. The modified EVOH obtained by the process can also be used as long as it can be melt-molded and does not impair the effects of the present invention, such as barrier properties and bending fatigue resistance.

The most important feature of the present invention is that a polyethylene polymer having a density of 0.91 to 0.86 g/cm ³ is used as the base for the resin component (B). If the density exceeds 0.91 g/cm ³ , the bending fatigue resistance, which is an effect of the present invention, will not be sufficient. A polyethylene polymer having a density of less than 0.86 g/cm ³ is not suitable because it does not pass through the manufacturing process sufficiently and cannot be stably supplied industrially. In order to more suitably enjoy the effects of the present invention, it is preferable to use a polyethylene polymer having a density of 0.905 to 0.87 g/cm ³ as the base. The reason for this is not necessarily clear, but it may be related to the crystallinity of the resin used as the base for component (B), but the density of the part where crystallinity is not controlled is 0.92g/ A copolymer with a density of 0.93 to 0.97 g/cm ³ is obtained by using a polyethylene polymer with a density of 0.93 to 0.97 g/cm ³ or by controlling the crystallinity by copolymerizing vinyl acetate, ethyl acrylate, etc. with ethylene. In such a case, the effects of the present invention cannot be enjoyed, and it is truly surprising that it is difficult to arrive at the present invention by analogy with the prior art. Although there are no restrictions on the method for producing such a polyethylene polymer, for example, there is a method in which ethylene and α-olefin are copolymerized at a polymerization temperature of 10 to 80° C. using a Ziegler type catalyst. As the α-olefin, those having 3 to 8 carbon atoms are used, such as propylene, butene-1, hexane-1, 4-methylpentene-1, octene-1, etc.
There is a first prize. Furthermore, various dienes such as butadiene, 1,4-hexadiene, 1,5-hexadiene, vinylnorbornene, ethylidene norbornene, and dicyclopentadiene can be added as a third monomer for copolymerization. In addition, commercially available products include, for example, Tafmer A-4085, which is marketed by Mitsui Petrochemicals, and Tafmer A
-4090, Tafmar P-0180, Tafmer P-0480 and other flexible resins DFDA-1137NT7, which are marketed by Nippon Unicar Co., Ltd.
Examples include DFDA−1138NT.

In the production of component (B), the ethylenically unsaturated carboxylic acid or carboxylic acid anhydride used in the graft polymerization includes maleic acid, acrylic acid,
Examples include ethylenically unsaturated carboxylic acids and carboxylic acid anhydrides such as itaconic acid, crotonic acid, maleic anhydride, and itaconic anhydride, among which maleic anhydride is preferred. When maleic anhydride is used, it can be co-grafted simultaneously with comonomers such as ethylene, styrene, vinyl acetate, vinyl ether, etc. The amount of grafting may be 0.001 to 6% by weight, but 0.01 to 5% by weight improves bending fatigue resistance,
It is more suitable in terms of impact resistance, uniform mixability, and moldability.

There are no particular limitations on the method of graft polymerization, but it is possible to add an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride to the ethylene-acrylic ester copolymer, dibenzoyl peroxide, dibutyl peroxide, dicumyl peroxide, t- Organic peroxides such as butyl perbenzoate, t-butyl hydroperoxide, and cumene hydroperoxide are allowed to coexist, and a heating reaction is performed to form a chemical bond between the two. The reaction can be carried out, for example, with benzene, toluene, xylene, chlorobenzene, t-
It can be carried out at a temperature of 100 to 240°C in the presence or absence of a solvent such as butylbenzene or cumene, but it can be carried out in the presence of a solvent such as toluene or xylene.
It is more preferable to carry out the process at 110 to 200°C because a uniform product can be obtained.

Examples of metal compounds consisting of metal hydroxides or salts of Group A or Group A of the Periodic Table include sodium carbonate, lithium carbonate, magnesium carbonate, sodium acetate, sodium hydroxide, calcium hydroxide, magnesium hydroxide, potassium hydroxide, etc. Among them, metal compounds of group a of the periodic table, such as sodium carbonate, sodium acetate, potassium hydroxide, and sodium hydroxide, are preferably used. Among them, sodium hydroxide is particularly preferably used. If the amount of the metal compound is less than 0.02 equivalent, the entire molded product will have a wavy pattern or unevenness, making it impossible to obtain an industrially useful molded product such as the one of the present invention. If more than 0.3 equivalents are blended, the polyethylene polymer grafted with ethylenically unsaturated carboxylic acid or carboxylic acid anhydride and has a density of 0.91 to 0.86 g/cm ³ will be affected by periodic rule a or a.
Modified copolymers blended with metal compounds consisting of group metal hydroxides or salts are undesirable because they become colored or have poor fluidity, making them unsuitable as molding materials.

In carrying out the present invention, component (C) is not necessarily required, but can be used as long as it satisfies the following formula () on a weight basis. If the value of formula () is less than 0.01, the effect of improving bending fatigue resistance is not significant, and the effects of the present invention cannot be enjoyed. In terms of performance, it can be used satisfactorily as long as it satisfies formula (), but in terms of manufacturing cost, etc.
The value of the formula is often used between 0.01 and 0.4. At this time, the density used for the raw material for component (B) is 0.91~
The polyethylene polymer with a density of 0.86 g/cm ³ and the polyethylene polymer with a density of 0.91 to 0.86 g/cm ³ used for component (C) may be the same, but even if they are different types, Alternatively, it may be a mixture.

1.0≧(B)/(B)+(C)≧0.01 () The density of (B) constituting the intermediate layer of the present invention is 0.91 to 0.86
g/cm ³ of an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride to a polyethylene polymer, and grafting 0.02 to 0.3 equivalents of periodic law a to the ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride component. Or a modified copolymer blended with a metal compound consisting of a hydroxide or salt of a Group A metal, or a mixture of (C) a polyethylene polymer with a density of 0.91 to 0.86 g/cm ³ and the modified copolymer (B). The blending amount of each component of the composition and (A) EVOH with an ethylene content of 20 to 55 mol% and a saponification degree of 90% or more must satisfy the following formula () on a weight basis for bending fatigue resistance and gas barrier properties. This is particularly important in terms of impact resistance and balance with mechanical properties.

0.40≧(B)+(C)/(A)+(B)+(C)≧0.05 () If the value of the formula () is less than 0.05, no improvement is seen in the bending fatigue resistance, which is not preferable. Moreover, when it exceeds 0.40, various physical properties such as gas barrier properties are deteriorated, which is not preferable.

There are no particular restrictions on the blending method used in the present invention to obtain the mixed composition of component (A) and components (B) and (C). A method may be arbitrarily selected in which the components () are premixed into pellets and blended into a portion of the component (A) in advance. (A) used in the present invention,
Other additives commonly used in other thermoplastic resins can be added to the mixed compositions of (B), (B)+(C), and (A)+(B)+(C). Examples of such additives include antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, and fillers, and these may be blended within a range that does not impede the effects of the present invention. be able to. Specific examples of additives include the following. Antioxidant: 2,
5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis-(6-t-butylphenol, 2,2'methylene-bis(4-methyl- 6-tert-butylphenol, tetrakis-[methylene-3-(3',5'-di-
t-Butyl-4'-hydroxyphenyl)propionate]methane, octadecyl-3-(3',5-
di-t-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis-(6-t-butylphenol), and the like. Ultraviolet absorber: Ethyl-2-
Cyano-3,3-diphenyl acrylate, 2-
(2'-hydroxy-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-
3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-hydroxy-4-
Methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, etc. Plasticizers: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate esters, etc. Antistatic agents: pentaerythritol monostearate, sorbitan monopalmitate, sulfated oleic acid, polyethylene oxide, carbo wax, etc. Lubricants: ethylene bisstearamide, butyl stearate, etc. Coloring agents: carbon black, phthalocyanine, quinacridone, indoline, azo pigments, titanium oxide, red iron oxide, etc. Filler: glass fiber, asbestos, mica,
Ballast night etc.

The means for blending each component to obtain the composition used in the present invention is not particularly limited, but examples thereof include a ribbon blender, high-speed mixer, kneader, mixing roll, Banbury mixer, extruder, and the like.

Next, it consists of a mixed composition of EVOH as described above,
The surface layers on both sides of the intermediate layer having gas barrier properties will be described. The best material for this surface layer is linear low-density polyethylene, and when this is used on both sides, the bending fatigue resistance is significantly improved. Furthermore, at least one of the surface layers must be made of a heat-sealable thermoplastic resin.

The linear low density polyethylene used in the present invention is a linear low density polyethylene having substantially no long chain branches. In general, a quantitative measure of the number of long chain branches G = [η] _b / [η] _l ([η] _b is the intrinsic viscosity of the branched polyethylene, [η] _l is the linear polyethylene with the same molecular weight as the branched polyethylene. (intrinsic viscosity) is approximately 1 (generally in the range of 0.9 to 1,
(often close to 1), and the density is 0.910~
It is of 0.945. Note that the G value of conventional high-pressure low-density polyethylene is 0.1 to 0.6. The method for producing linear low density polyethylene is not particularly limited. An example of a typical manufacturing method is 7 to 45Kg/cm ²
pressure (usually for high-pressure low-density polyethylene)
2000 to 3000 Kg/cm ² ), at a temperature of 75 to 100°C (120 to 250°C in the case of high-pressure low density polyethylene), using a chromium-based catalyst or Ziegler catalyst, with a carbon number of 3 or more, preferably 4 or more, More preferably 5
~10 α-olefins, such as propylene, butene-1, 4-methyl-1-pentene, hexene-1
1. There is a method of copolymerizing ethylene using α-olefin such as octene-1 as a random copolymerization component. As the polymerization method, a liquid phase method or a gas phase method is used.

The effects of the present invention are deeply related to the number of carbon atoms in the α-olefin, the heat of fusion of the linear low-density polyethylene determined by thermal analysis using a differential scanning calorimeter, and the Young's modulus. It is as follows. Linear low-density polyethylene is preferably used in the present invention, but it has a heat of fusion of 25 cal/g or less, preferably 25 to 5 cal/g, or a Young's modulus at 20°C of 22 Kg/mm ² or less, preferably is 22~3Kg/
mm ² , more preferably 22 to 5 Kg/mm ² , the effect of the present invention is more remarkable, especially when both are in the above range. Those whose heat of fusion and Young's modulus are in the above-mentioned range vary somewhat depending on the polymerization method and polymerization conditions, but in other words, the content of the α-olefin, which is a copolymer component, is about 2 mol% or more, Preferably about 2-7 mol%
It is often obtained in the area of For linear low density polyethylene whose copolymerization component is butene-1, the heat of fusion is 15 cal/g or less, or 20°C
The effect of the present invention is more remarkable when the Young's modulus is 12 Kg/mm ² or less, and especially when both are in the above range, the effect can be most significantly enjoyed. The low-density polyethylene having the heat of fusion and Young's modulus in the above range is often obtained in a range where the butene-1 content is about 4 mol % or more. If the content is too large, other physical properties of the polyethylene become unsatisfactory, which is not preferable, and the content is preferably several mol% at most, for example 7 mol%. Further, as described above, the effects of the present invention can be enjoyed with linear low-density polyethylene whose heat of fusion and/or Young's modulus are in the specific range, but especially with α-olefins having 5 or more carbon atoms, for example, 5 to 10 carbon atoms. This effect can be enjoyed more markedly with the polyethylene containing as a copolymerization component. In this case, for the same reason as mentioned above, the content of the α-olefin is preferably 2 to 7 mol%, more specifically 2 to 6 mol%, and the heat of fusion is the same as the α-olefin content. etc., but especially the heat of fusion is
It is preferably 25 to 5 cal/g, and the Young's modulus is 22 Kg/mm ² or less, preferably 22 to 3 Kg/mm ² , and more preferably 22 to 5 Kg/mm ² . Among these olefins, the effect of the present invention is more remarkable, and linear low-density polyethylene containing 4-methyl-1-pentene as a copolymerization component, which is easily obtained industrially, is one of the most suitable. . In the case of conventional high-pressure low-density polyethylene, the effects of the present invention cannot be enjoyed even if the heat of fusion and/or Young's modulus as determined by thermal analysis using a differential scanning calorimeter are in the above range.

In the present invention, as described above, the best material for the surface layers on both sides of the intermediate layer is linear low-density polyethylene, but other heat-sealable thermoplastic resins (at least on one side) may be used. However, a heat-sealable resin can also be used for the other surfaces. In addition to the above-mentioned linear low-density polyethylene, heat-sealable thermoplastic resins include high-pressure low-density polyethylene, low-pressure high-density polyethylene, polypropylene, various polyamide resins such as nylon, polyester resins, and ethylene resins.
Examples include vinyl acetate copolymer resin. Examples of resins that cannot be heat-sealed include stretched resins such as biaxially stretched polypropylene and nylon.

The melt viscosity of the resin used for the surface layer can be selected as appropriate, but in particular when obtaining the laminate by coextrusion, the melt viscosity of the resin used for the surface layer may be selected from the viewpoint of the composition of the intermediate layer used and the melt viscosity consistency with the adhesive resin. It is more preferable to select and use those having similar melt viscosity. The MI of the surface layer measured at 190°C according to ASTM-D-1238 is 0.1 to 20g/10min, preferably 0.2
~10g/10min.

The laminated packaging material of the present invention requires that each layer be arranged with an adhesive resin layer interposed therebetween,
It must not cause gelation during the bending fatigue resistance test using the Gelbo Flex Tester. When delamination occurs, no improvement in the bending fatigue resistance of the intermediate layer is observed, and the decrease in barrier properties due to damage to the intermediate layer causes pinholes to appear in the laminated film. Since this is already recognized at the stage where it is not possible to enjoy the effects of the present invention. The adhesive resin used in the present invention is not particularly limited as long as it does not cause delamination in the practical stage, but adhesive resins with high flexibility are more suitable, especially In combination with adhesion to the surface layer such as linear low-density polyethylene and the intermediate layer made of the EVOH mixed composition, chemically adding ethylenically unsaturated carboxylic acid or its anhydride to the olefinic polymer ( Modified olefinic polymers containing carboxyl groups obtained by bonding (for example, by addition reaction or grafting reaction) are suitable. Here, olefin polymers include polyethylene (low pressure, medium pressure, high pressure), linear low density polyethylene,
Polyolefins such as polypropylene and polybutene, copolymers of olefins and comonomers (vinyl esters, unsaturated carboxylic acid esters, etc.) that can be copolymerized with the olefins, such as ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers It means merging.

Next, regarding the thickness of each layer of the laminated packaging material of the present invention, if each layer of the surface layer is too thin, for example, 10μ or less, other physical properties such as strength will deteriorate, so The thickness is preferably 20μ or more, and more preferably 20μ or more. Furthermore, if the thickness increases too much, the effect of the present invention will be diminished, so each layer of the surface layer should have a thickness of 60 μm.
It is more preferable to use it below. In particular, the inner container components of bag-in boxes usually have a thickness of 25 to 60 μm.
It can be selected from the thickness range according to the internal capacity and used suitably. If the thickness of the thin film having gas barrier properties in the intermediate layer exceeds 40 μm, the bending fatigue resistance will decrease and the effects of the present invention will be diminished, which is not preferable. In order to fully enjoy the effects of the present invention, the thickness of the intermediate layer is preferably 40μ or less, more preferably 35μ or less. The thickness of each adhesive resin layer is 2
It is preferably ~10μ.

The laminated packaging material of the present invention can be obtained by known methods such as coextrusion, extrusion lamination, and dry lamination, with coextrusion being preferred.
Furthermore, when forming a film by coextrusion, it is effective to use an air slit during film formation. Here, the term "air slit" refers to an operation in which air is blown into a slit shape to bring the molten resin film discharged from the die onto the cast roll into close contact with the cast roll and to enhance the cooling effect. In addition, the bag-in-box inner container using the laminated packaging material can be produced by heat-sealing the laminated film and attaching a cap, or by vacuum forming the laminated sheet into a container and gluing the cap to it. Alternatively, the multi-layer parison with the laminated structure is melt-extruded, sandwiched between molds with a cap inserted, and molded with compressed air, and the heat of the parison and air pressure are used to heat the main body and the cap. It can be obtained by a known method such as a blow molding method using adhesion.

In addition, in the present invention, it is an object of the present invention to further provide other layers (resin layers, etc.) to the laminated material in which the EVOH-based mixed composition is used as an intermediate layer and linear low-density polyethylene layers are provided on both sides. is free as long as it is not obstructed.

The laminated packaging material of the present invention obtained in this way can contain aqueous mixtures or water-containing substances, particularly liquid or water-containing foods, such as alcohols such as wine and liquor,
Suitable as a container material for transporting soybean oil. That is, a bag (equipped with a cap for putting in and taking out the filling liquid) is made using the laminated packaging material,
After filling the above-mentioned liquid food into this bag, the bag is sealed and stacked inside a bag-in box to form a so-called bag-in box. When transporting this bag, the material of the bag (inner container) Since certain laminated packaging materials have excellent bending resistance, cracks do not occur, and therefore leakage of liquid foods can be prevented, and deterioration of the quality of liquid foods due to the intrusion of oxygen can be prevented.

Hereinafter, the present invention will be explained in more detail using examples, but the present invention is not limited to these examples in any way. The testing and evaluation methods in Examples and Comparative Examples are as follows.

Melt Index (MI) In accordance with ASTM D-1238, this shows the resin flow rate for 10 minutes when a load of 2160 g is applied using a melt indexer. The measurement temperature is 190℃.

Bending fatigue test Using a Gerbo Flex Tester (manufactured by Rigaku Kogyo Co., Ltd.), a 12 inch x 8 inch sample piece was shaped into a cylinder with a diameter of 3.5 inches, gripped at both ends, and an initial grip interval of 7 inches, max. The grip distance during bending is 1 inch, the first 3.5 inches of the stroke is a twist of 440 degrees, and the next 2.5 inches are straight and horizontal movements. Repeated reciprocating motion at a rate of 40 times/minute at 20 degrees Celsius. ,
It is carried out under conditions of relative humidity of 65%.

Measurement of oxygen gas permeation The measurement was carried out using OX-TRAN100 manufactured by Modern Control under conditions of 20°C and 65% relative humidity. The samples after each stage of the bending fatigue test were made into a 12 inch x 8 inch plane, and measurements were taken at the center of the plane.

Young's modulus 20℃, relative humidity according to ASTM D-882-67
It was carried out under 65% conditions.

G Examples Example 1 Tafmer A-4085 (density 0.88 g/cm ³ , MI (190
℃, 2160g) is 3.6g/10 minutes of polyethylene resin,
(manufactured by Mitsui Petrochemical Co., Ltd.) and 1.8 parts by weight of maleic anhydride were dissolved in 648 parts by weight of purified toluene and kept at 180°C. A purified toluene solution containing 25 parts by weight of maleic anhydride dissolved in this solution under stirring.
180 parts by weight were added continuously over 2.0 hours. At the same time, 100 parts by weight of a purified toluene solution containing 4.0 parts by weight of cumene hydroperoxide was continuously added over 2.0 hours. Post-reaction was continued for 30 minutes even after the addition was completed. After cooling, the reaction solution was poured into a large amount of acetone to precipitate a polymer. The obtained polymer was purified by reprecipitation using purified toluene as a solvent and acetone as a non-solvent. This product contains 1.5% by weight of maleic anhydride component, and the MI is
It was 2.0g/10 minutes.

20 g of an aqueous solution containing a predetermined amount of sodium hydroxide (NaOH) was added uniformly to 100 parts by weight of the polymer thus obtained, and after partially drying, it was melted using a vented extruder while expelling volatiles under reduced pressure. The mixture was kneaded and pelletized to obtain a modified copolymer (B).

20 parts by weight of the modified copolymer (B) obtained above was dry blended with the above Tafmer A-4085 (C), and then melt-kneaded into pellets using an extruder to form a resin blend composition (B) + (C). I got it.

On the other hand, the ethylene content was 31 mol%, and the degree of saponification was
99.5%, MI 1.4g/10min EVOH as component (A),
An intermediate layer with a thickness of 20μ consisting of a mixed composition of 80 parts by weight of component (A) and 20 parts by weight of (B) + (C) obtained above, and 4 layers each having a thickness of 35μ on both sides of the intermediate layer. -Methyl-1-pentene as a copolymer component, containing 3.2 mol% of the copolymer component, and having a surface layer made of linear low-density polyethylene (LLDPE) with an MI of 2.1 g/10 minutes, with a thickness between each layer. Three extruders, three extruders, It was obtained by a coextrusion method using a multilayer die head for five layers. The composition used for the intermediate layer was pellets that had been mixed in advance using an extruder. The obtained laminated film was subjected to a bending fatigue test and the amount of oxygen gas permeated at each stage up to the generation of pinholes in the laminated film was measured. During the bending fatigue test process up to the occurrence of pinholes, there was almost no change in the amount of oxygen permeation. Further, the occurrence of pinholes was not observed until 7,500 cycles had passed in the bending fatigue test, and after 7,600 cycles, when the test piece was inspected for the presence of pinholes, it was found that one pinhole had already occurred. Furthermore, no delamination between the layers was observed. In addition, as a result of separately obtaining the LLDPE film and measuring the Young's modulus, it was found that it was 13
It was Kg/ ^mm2 .

Example 2 Modified copolymer used as component (B) of intermediate layer
The same procedure as in Example 1 was conducted except that the amount of NaOH added was 0.05 equivalent. It was not noticed until after 6,500 cycles of the bending fatigue test, and after 6,900 cycles, when the pinhole was inspected, it was found that one pinhole had already occurred.

Comparative Example 1 A laminated film was obtained in the same manner as in Example 1 except that NaOH was not added. Many bump-like irregularities were observed in the obtained laminated film. A bending fatigue test was conducted on the laminated film. For the sample selected from a location where no lumpy irregularities were observed, no pinholes were observed until 6,500 reciprocations, and one pinhole appeared after 6,600 reciprocations. However, in the sample with bump-like unevenness, one pinhole had already occurred after 200 reciprocations. Only 20% of the samples had no lumpy irregularities and were of low industrial value.

Comparative Example 2 The same procedure as Example 1 was carried out except that 0.6 equivalents of NaOH was added. Although this modified copolymer was colored brown, a laminated film was obtained. The obtained laminated film had many brownish bumpy irregularities and was of low industrial value.

Example 3 A laminated film was obtained in the same manner as in Example 1 except that the modified copolymer (B) was used instead of the blend composition of (B) + (C) in Example 1. Bending fatigue test 7000
It was not noticed until after 7,200 reciprocations had passed, and when the pinhole was inspected, it was found that one pinhole had already occurred.

Example 4 A laminated film having the structure D/Ad/E/Ad/F/Ad/G was obtained using coextrusion equipment having a multilayer die head for three types and seven layers. Each layer consists of each resin and layer thickness shown below.

E, F: Flex resin DFDA-1138NT (density 0.90g/cm ³ , MI (190
℃, 2160g) is 0.4g/10 minutes, manufactured by Nippon Unicar)
A _{modified copolymer} ( B) was obtained.

Tafmer P-0180 (density 0.88 g/cm ³ , MI4.5, manufactured by Mitsui Petrochemicals) was used as the (C) component resin. A layer with a thickness of 12μ consisting of a blend composition of A:B:C=90:5:5 using EVOH with an ethylene content of 38 mol% and a saponification degree of 99.4% as component (A) D, G: 4-methyl-1 - 40 μ thick LLDPE layer containing 4.1 mol% of pentene as copolymerization component, melt index 2.3 g/10 min, heat of fusion 15 cal/g by DSC Ad: 33 wt% vinyl acetate content, maleic anhydride modification The adhesive resin layer was made of a modified ethylene-vinyl acetate copolymer having a concentration of 0.2% by weight, and the layer thickness was 6 μm. A bending fatigue test was conducted in accordance with Example 1. No pinholes were observed even after 6,000 cycles of the bending fatigue test, and after 6,300 reciprocations, an inspection for the presence of pinholes revealed that one pinhole had already occurred. Furthermore, no delamination between the layers was observed. In addition, as a result of separately obtaining the LLDPE film and measuring the Young's modulus, it was 7.5Kg/mm ²
It was hot.

Comparative Example 3 A laminated film was obtained in the same manner as in Example 4 except that 0.005 equivalent of potassium carbonate was added. Bumpy unevenness was observed in the obtained laminated film. A bending fatigue test was conducted on the laminated film.
5500 samples were selected where no lumpy irregularities were observed.
No pinholes were observed until the round trip, and one pinhole appeared after 5,700 round trips. However, in the sample with bump-like unevenness, pinholes were already generated after 300 reciprocations. Only 25% of the samples had no lumpy irregularities and were of low industrial value.

Comparative Example 4 The same procedure as Example 4 was carried out except that 1.0 equivalent of potassium carbonate was added. This modified copolymer had extremely poor fluidity and no laminated film could be obtained.

Claims (1)

[Claims] 1. A thin film having gas barrier properties is used as an intermediate layer, a surface layer is provided on both sides of the intermediate layer, at least one of the surface layers is made of a heat-sealable thermoplastic resin layer, and each layer is made of a heat-sealable thermoplastic resin layer. In a laminated packaging material arranged through an adhesive resin layer, the intermediate layer has (A) an ethylene content
Ethylene-vinyl acetate copolymer in which 20 to 55 mol% and 95% or more of the vinyl acetate component has been saponified and (B) a polyethylene polymer with a density of 0.91 to 0.86 g/ ^cm3 , ethylenically unsaturated carboxylic acid or The carboxylic acid anhydride is grafted to the ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride component to
0.3 equivalent of a metal compound consisting of a hydroxide or salt of a metal of Group A or Group A of the Periodic Table is blended, or the metal compound and (C) have a density of 0.91 to 0.86 g/
cm ³ of polyethylene polymer, and (A), (B)
The blending amount of (C) and (C) is based on the following formula (),
A laminated packaging material with excellent bending fatigue resistance, characterized by being a mixture that satisfies formula (). 0.40≧(B)+(C)/(A)+(B)+(C)≧0.05 () 1.0≧(B)/(B)+(C)≧0.01 () 2 Ethylenically unsaturated carboxylic acid or The laminated packaging material according to claim 1, wherein the carboxylic acid anhydride is maleic anhydride. 3. The laminated packaging material according to claim 1 or 2, wherein the metal compound is a metal compound consisting of a hydroxide or salt of a Group A metal of the periodic table. 4. The laminated packaging material according to any one of claims 1 to 3, wherein the metal compound is sodium hydroxide. 5. The laminated packaging material according to any one of claims 1 to 4, wherein the adhesive resin layer has a thickness of 1 to 20 μm. 6. The laminated packaging material according to any one of claims 1 to 5, wherein at least one of the surface layers is made of linear low-density polyethylene. 7 α in which at least one of the surface layers has 4 or more carbon atoms
- The laminated packaging material according to claim 6, which is linear low-density polyethylene containing olefin as a copolymerization component and having a heat of fusion of 25 cal/g or less based on thermal analysis using a differential scanning calorimeter. 8. Claim 6, wherein the linear low-density polyethylene is linear low-density polyethylene that contains butene-1 as a copolymer component and has a heat of fusion of 25 cal/g or less based on thermal analysis using a differential scanning calorimeter. The laminated packaging material described in Section. 9. Claim No. 9, wherein the linear low-density polyethylene is a linear low-density polyethylene that contains 4-methylpentene as a copolymerization component and has a heat of fusion of 25 cal/g or less based on thermal analysis using a differential scanning calorimeter. Laminated packaging material according to item 6. 10. The laminated packaging material according to any one of claims 6 to 9, wherein the linear low-density polyethylene has a Young's modulus of 12 Kg/cm ² or less at 20°C. 11. The laminated packaging material according to any one of claims 1 to 10, wherein one of the surface layers is a heat-sealable thermoplastic resin. 12. The laminated packaging material according to claim 11, wherein the heat-sealable thermoplastic resin is an ethylene-vinyl acetate copolymer containing 7% by weight or more of a vinyl acetate component. 13. The laminated packaging material according to claim 12, wherein the laminated packaging material is a constituent material of a packaging container in which the packaging filler is an aqueous mixture or a water-containing substance. 14. The laminated packaging material according to claim 13, wherein the packaging material is a component of a bag-in-box inner container.