JP6756226B2 - Multi-layer structure for ultra-high pressure treatment, packaging for ultra-high pressure treatment and its treatment method - Google Patents

Description

The present invention relates to a multi-layer structure for ultra-high pressure treatment, a package for ultra-high pressure treatment, and a method for treating a package for ultra-high pressure treatment.

In recent years, self-standing bags (also referred to as stand-up pouches), which are lighter than conventional bottles and cans and have excellent volume reduction after use, have become widespread as packaging containers for foods and the like. The film material constituting the stand-up pouch is required to have rigidity that allows it to stand on its own when the contents are filled and gas barrier properties from the viewpoint of preventing deterioration of the contents.

Further, in recent years, as a food for long-term storage, a food in which a pouch (packaging container) is filled with food and sterilized has attracted attention. As a method for sterilizing such pouch foods, a method for hot water treatment such as retort treatment and boil treatment, a method for irradiating radiation such as ultraviolet rays and gamma rays, and a method for high pressure treatment are known.

For example, in Patent Document 1, after storing and sealing the object to be treated in a packaging material in which a hydrophobic layer is laminated on at least one of an ethylene-vinyl acetate copolymer saponified layer, the hydrostatic pressure is 4000 kg / cm ² or less. A high-pressure sterilization method is disclosed, which comprises performing a high-pressure treatment under a condition where the temperature is 60 ° C. or lower and the water absorption rate of the packaging material is 2% by weight or less.

Further, Non-Patent Document 1 discloses a method of performing ultra-high pressure sterilization at a higher pressure in recent years in accordance with food safety requirements.

Japanese Unexamined Patent Publication No. 3-290175

Amparo Lopez-Rubio, Jose M. Lagaron, Pilar Hernandez-Munoz, Eva Almenar, Ramon Catala, Rafael Gavara, Melvin A. Pascall, Innovative Food Science and Emerging Technologies 6 (2005) 51-58

However, when the pouch food is treated with high pressure, the packaging material constituting the pouch may be partially whitened when the conventional pouch is subjected to the ultra-high pressure sterilization treatment of 100 MPa or more. In particular, this tendency is seen in stand-up pouches, and when the packaging material is whitened, the contents become difficult to see and the commercial value is lowered. Therefore, measures to prevent whitening have been desired.

Therefore, an object of the present invention is to provide a multilayer structure for ultra-high pressure treatment in which whitening does not occur even when sterilization treatment is performed under ultra-high pressure of 100 MPa or more. An object of the present invention is to provide an ultra-high pressure processing package having the ultra-high pressure processing multilayer structure and a processing method thereof.

When the present inventors examined the packaging material bleached by the prior art in detail, the bleaching occurred in the innermost layer of the packaging material, that is, the portion in contact with the contents and forming a gap inside the pouch. We found that it tends to occur. That is, it was found that whitening of the innermost layer of the packaging material is unlikely to occur at a location where it comes into contact with the liquid or solid content. As a result of diligent studies based on this finding, the present inventors have made the multilayer structure constituting the packaging such as a pouch flexible in a specific range so that the multilayer structure can be made of liquid, solid matter, etc. We have found that the area of contact with the contents can be increased and the area of contact with the voids inside the package can be reduced, and the present invention has been completed.

That is, the gist of the present invention is the following (1) to (6).
(1) A multi-layer structure used for processing under an ultra-high pressure of 100 MPa or more, and the upper yield point stress and the lower yield point stress in a tensile test with respect to the film flow direction (MD) at a test speed of 200 mm / min. Ratio: A multilayer structure for ultra-high pressure processing, characterized in that the upper yield point stress / lower yield point stress is 1.3 or less.
(2) At least, it has a base film (A), an ethylene-vinyl ester copolymer saponified product (C) layer and a heat seal resin (D) layer, and the base film (A) and the heat seal resin. The multilayer structure for ultra-high pressure treatment according to (1) above, wherein the ethylene-vinyl ester copolymer saponified product (C) layer is located between the layer (D) and the layer (D).
(3) The multilayer structure for ultra-high pressure treatment according to (2) above, wherein the heat-sealing resin (D) layer is made of a resin composition (d) containing a thermoplastic elastomer.
(4) The multilayer structure for ultra-high pressure treatment according to any one of (1) to (3) above, which has a thickness of 10 to 600 μm.
(5) An ultra-high pressure processing package having the ultra-high pressure processing multilayer structure according to any one of (1) to (4) above.
(6) A method for treating an ultra-high pressure processing package according to the above (5), which comprises treating the ultra-high pressure processing package at a pressure of 100 to 900 MPa.

The multi-layer structure for ultra-high pressure treatment of the present invention maintains an appropriate rigidity because the ratio of the upper yield point stress to the lower yield point stress is 1.3 or less as the value of the upper yield point stress / the lower yield point stress. It also has flexibility. Therefore, when the pouch is made, the opposing surfaces tend to overlap, so that the area in contact with the contents becomes large, and the contact area with the void inside the pouch becomes small. Therefore, even if the pouch is treated under an ultrahigh pressure of 100 MPa or more, whitening is unlikely to occur in the multilayer structure. Further, in the multi-layer structure for ultra-high pressure treatment of the present invention, when the pouch is formed, the voids in the pouch are not dispersed and easily gather in one place, so that the diffusion of bleaching can be suppressed.
Therefore, it can be suitably used as a packaging material for pouch foods subjected to ultra-high pressure sterilization treatment, and in particular, it can be suitably used for stand-up pouches in which bleaching is likely to occur.

FIG. 1 is a schematic cross-sectional view showing the configuration of an embodiment of the multilayer structure for ultra-high pressure treatment according to the present invention. FIG. 2 is an overall perspective view showing an example of the stand-up pouch of the present invention.

Hereinafter, the multi-layer structure for ultra-high pressure treatment of the present invention will be described in detail by taking a stand-up pouch as an example, but the multi-layer structure for ultra-high pressure treatment of the present invention is not limited to the form of the stand-up pouch.

In the present invention, the side that houses the contents of the stand-up pouch, that is, the sealant side is referred to as "inside", and the opposite side is referred to as "outside".
Further, in the following description, terms such as "top", "bottom", "left", and "right" are for convenience corresponding to the direction of the drawing.
In general, a "film" is a thin flat product whose thickness is extremely small compared to its length and width and whose maximum thickness is arbitrarily limited, and is usually supplied in the form of a roll. , "Sheet" refers to a thin, flat product whose thickness is generally small for its length and width (Japanese Industrial Standards JIS K6900). However, since the boundary between the sheet and the film is not clear and it is not necessary to distinguish between the two in the present invention, the term "film" shall include the "sheet", and the term "sheet" may be referred to as the "film". Shall include.

Further, in the present invention, the "stand-up pouch" means a packaging body having a body portion and a bottom portion provided in a direction perpendicular to the body portion and having rigidity capable of becoming self-supporting when filled with contents. It is a thing.

(Multi-layer structure for ultra-high pressure processing)
The multi-layer structure for ultra-high pressure treatment of the present invention (hereinafter, may be simply referred to as “multi-layer structure”) is a multi-layer structure used for processing under ultra-high pressure of 100 MPa or more, and has a test speed of 200 mm. The ratio of the upper yield point stress to the lower yield point stress in the tensile test with respect to the flow direction (MD) of the film at / min: The upper yield point stress / the lower yield point stress is 1.3 or less.

The multilayer structure for ultra-high pressure treatment of the present invention has, as a preferred embodiment, at least a base film (A), an ethylene-vinyl ester-based copolymer saponified product (C) layer, and a heat-sealed resin (D). It has a layer, and the ethylene-vinyl ester copolymer saponified product (C) layer is located between the base film (A) and the heat-sealed resin (D) layer.
Each layer will be described below.

<Base film (A)>
Since the base film (A) in the present invention is a basic material constituting the multilayer structure of the present invention, it has excellent mechanical, physical, chemical and other strengths, and further has piercing resistance. It is preferable to use a resin film or sheet having excellent heat resistance, moisture resistance, pinhole resistance, transparency and the like.

Specifically, examples of the base film (A) include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide resins such as various nylon resins, polyaramid resins, polypropylene resins, and polyethylene resins. Films or sheets obtained from polycarbonate resins, polyacetal resins, fluororesins, other tough resins, etc. can be used, and among them, they are obtained from polyester resins because of their excellent dimensional stability and printability. The polyester resin film to be used is preferable.

As the resin film or sheet, any unstretched film, stretched film stretched in the uniaxial direction or biaxial direction, or the like can be used.

Further, the thickness of the base film (A) in the present invention may be any thickness that can be retained in terms of strength, puncture resistance, etc. If it is too thick, the cost tends to increase. If it is too thin, the strength, puncture resistance, etc. tend to decrease.
In the present invention, for the above reasons, the thickness of the base film (A) is preferably 3 to 100 μm, particularly preferably 10 to 50 μm.

Further, the base film (A) may be appropriately provided with a printing layer as needed. The printing layer is formed by an ink obtained by blending a solvent, a binder resin such as urethane-based, acrylic-based, nitrocellulose-based, or rubber-based, and various pigments, extender pigments and plasticizers, desiccants, stabilizers, and the like. It is a layer to be printed. Characters, patterns, etc. can be formed by this printing layer. As the printing method, for example, known printing methods such as offset printing, gravure printing, flexographic printing, silk screen printing, and inkjet printing can be used. Further, the adhesion of the printing layer can be improved by subjecting the surface of the base film (A) to a corona treatment or an ozone treatment as a pretreatment in advance. Usually, a printing layer is provided on the inner surface of the base film (A).

<Heat seal resin (D) layer>
The heat-sealed resin (D) layer used in the present invention is a layer that can be melted by heat and fused to each other. In particular, in the present invention, it is preferable that the resin composition (d) constituting the heat-sealed resin (D) layer contains a thermoplastic elastomer.

The thermoplastic elastomer acts as a soft component in the heat-sealed resin (D) layer, is useful for adjusting the range of the upper yield point stress / the lower yield point stress specified in the present invention, and is effective in suppressing whitening of the multilayer structure. When the multilayer structure of the present invention is used as a stand-up pouch, appropriate rigidity can be imparted and independence can be improved.

[Thermoplastic elastomer]
The thermoplastic elastomer referred to in the present invention is, for example, an olefin-based thermoplastic elastomer such as Thermolan manufactured by Mitsubishi Chemical Corporation, Tuffmer manufactured by Mitsui Chemicals Co., Ltd., Lavalon manufactured by Mitsubishi Chemical Corporation, or the like. Examples thereof include styrene-based thermoplastic elastomers such as Tough Tech, which is a trade name manufactured by Asahi Kasei Co., Ltd., and urethane-based thermoplastic elastomers such as Elastolan, which is a trade name manufactured by BASF. Among them, the olefin-based thermoplastic elastomer is preferable in that the suppression of whitening of the multilayer structure during the ultra-high pressure treatment is improved and the dispersibility in the resin composition (d) is excellent.
In particular, the olefin-based thermoplastic elastomer contains an olefin, which is an aliphatic hydrocarbon monomer containing a carbon-carbon double bond, as a main monomer, and is usually a polymer having a number average molecular weight of 10,000 or more, and the main chain has only a carbon bond. Refers to an aliphatic polymer composed of.

The olefin-based thermoplastic elastomer includes polyolefin (polyethylene, polypropylene, etc.) as a hard segment and aliphatic rubber (for example, ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), etc.) as a soft segment. It is an elastomer resin exhibiting thermoplasticity using the above, and examples thereof include those synthesized by a method of compounding polyolefin and aliphatic rubber (compound type) or a method of introducing aliphatic rubber at the time of olefin polymerization (reactor type). .. The compound type includes a simple blend product (non-crosslinked type) and a dynamically crosslinked product (two types, a fully crosslinked type and a partially crosslinked type).

The thermoplastic elastomer used in the present invention, from the viewpoint of transparency, density is preferably from 0.85~0.96g / cm ^3, more preferably 0.85~0.92g / cm ^3, 0. 85 to 0.90 g / cm ³ is more preferable. The density referred to in the present invention is a value measured in accordance with JIS K7112.

Further, the thermoplastic elastomer used in the present invention has good bending flexibility when the flexural modulus at 23 ° C. and 50% RH is preferably less than 150 MPa, more preferably less than 100 MPa, and particularly preferably less than 50 MPa. It is desirable in that it is. The flexural modulus referred to in the present invention is a value measured in accordance with JIS K7171.

In order to obtain a better accumulated fatigue absorption effect on the multilayer structure, heat having a density of 0.85 to 0.90 g / cm ³ and a flexural modulus of less than 50 MPa at 23 ° C. and 50% RH. It is preferable to use a plastic elastomer.

Furthermore, the glass transition temperature of the thermoplastic elastomer is usually −110 ° C. to 0 ° C., preferably −80 ° C. to −20 ° C., and more preferably −70 ° C. to −40 ° C. Since the glass transition temperature is in a temperature range much lower than room temperature and the crystallinity is low, the flexibility in a wide temperature range from low temperature to room temperature is very excellent. Here, the glass transition temperature means the temperature at which the amorphous portion of the thermoplastic elastomer transitions from the glass state to the rubber state, and is usually measured by a method conforming to JIS K7121 using a differential scanning calorimeter. be able to.

The melt flow rate (MFR) of the thermoplastic elastomer is usually 0.01 to 150 g / 10 minutes, preferably 0.1 to 50 g / 10 minutes under the conditions of 210 ° C. and a load of 2160 g. It is more preferably 1 to 25 g / 10 minutes, and even more preferably 2 to 10 g / 10 minutes.

The content of the thermoplastic elastomer is preferably 1 to 90% by mass, more preferably 3 to 70% by mass, and 5 to 50% by mass in the resin composition (d) constituting the heat seal resin (D) layer. % Is more preferable, and 10 to 40% by mass is particularly preferable. If the amount is too large, there is a high possibility that the thermoplastic elastomer component will elute toward the contents when the stand-up pouch is treated with ultra-high pressure, and if it is too small, the effect of improving the bag-drop resistance will not be exhibited. There is a tendency.
The bag resistance means, for example, when the stand-up pouch receives a momentary bending impact due to dropping, the multi-layer structure cracks, or in some cases, the multi-layer structure cracks, and the contents of the stand-up pouch. It refers to the property that things do not leak.

As the resin component other than the thermoplastic elastomer in the resin composition (d), a conventionally known resin having a heat-sealing property (heat-sealing resin) can be used. For example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-propylene copolymer, methyl. One type of resin such as penten polymer, polyolefin resin such as polyethylene or polypropylene, and acid-modified polyolefin resin obtained by modifying these polyolefin resins with acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, or other unsaturated carboxylic acids. Examples thereof include resins made of or more.
Above all, it is preferable to add a polyolefin resin from the viewpoint of improving the suppression of whitening of the multilayer structure during ultra-high pressure treatment and imparting sufficient independence to the stand-up pouch, and above all, linear low density. Dense polyethylene (LLDPE) or polypropylene is preferable, and polypropylene is particularly preferable from the viewpoint of suppressing elution after ultra-high pressure treatment.

The content of the polyolefin-based resin is preferably 10 to 99% by mass, more preferably 30 to 97% by mass, still more preferably 50 to 95% by mass, and particularly preferably 60 in the resin composition (d). ~ 90% by mass. If the amount is too large, the effect of improving the bag-drop resistance tends not to be exhibited, and if it is too small, the thermoplastic elastomer component may elute toward the contents when the stand-up pouch is subjected to ultra-high pressure treatment. It tends to be more sexual.

In the multilayer structure of the present invention, the content concentration of the thermoplastic elastomer in the heat-sealed resin (D) layer is such that the surface layer on the opposite side to the substrate film (A) side is the substrate in the thickness direction of the multilayer structure. The concentration is preferably lower than that of the surface layer on the film (A) side.
By setting the concentration of the thermoplastic elastomer in the heat-sealed resin (D) layer to be higher on the base film (A) side, it is possible to suppress the seepage of the thermoplastic elastomer into the contents when the pouch is formed. can do.

As a method for changing the content concentration of the thermoplastic elastomer in the heat-sealed resin (D) layer in the thickness direction, for example, a plurality of resin compositions (d) having different contents of the thermoplastic elastomer are prepared. A method of forming the heat-sealed resin (D) layer so that the resin composition (d) having a higher content of the thermoplastic elastomer is located on the base film (A) side can be mentioned. When the heat-sealing resin (D) layer is formed of three or more kinds of resin compositions (d), the thermoplastic elastomer in the resin composition (d) forming the surface layer on the base film (A) side is used. If the concentration is higher than the concentration of the thermoplastic elastomer in the resin composition (d) forming the surface layer opposite to the base film (A), the concentration of the thermoplastic elastomer in the intermediate layer is the base. It may be higher or lower than the concentration of the surface layer on the material film (A) side.

As described above, the heat-sealing resin (D) layer in the present invention can be composed of a single layer or multiple layers. A multilayer structure is preferable from the viewpoint that the content concentration of the thermoplastic elastomer in the heat-sealed resin (D) layer can be easily adjusted.

In this way, the content concentration of the thermoplastic elastomer in the heat-sealed resin (D) layer is changed in the thickness direction of the multilayer structure by using the layer composed of the plurality of resin compositions (d) having different thermoplastic elastomer concentrations. In this case, all the layers made of the resin composition (d) containing the thermoplastic elastomer are regarded as the heat-sealed resin (D) layer. In this case, the content of the thermoplastic elastomer of the resin composition (d) and the content of the resin component other than the thermoplastic elastomer in the heat-sealed resin (D) layer are determined by multiplying the concentration of each layer by the thickness ratio of each layer. Adopt the added value.

In the present invention, the difference between the concentration of the surface layer on the base film (A) side and the concentration of the surface layer on the opposite side to the base film (A) side of the thermoplastic elastomer in the heat seal resin (D) layer is 3 It is preferably 5% by mass or more, more preferably 5 to 90% by mass, further preferably 8 to 50% by mass, and particularly preferably 8 to 20% by mass. When the difference between the concentration of the surface layer on the base film (A) side of the thermoplastic elastomer and the concentration of the surface layer on the opposite side to the base film (A) side is within the above range, the base of the heat-sealing resin (D) layer. The development of impact resistance to the thermoplastic elastomer existing on the material film (A) side and the above-mentioned thermoplastic elastomer component to the contents on the side opposite to the base film (A) side of the heat seal resin (D) layer. There is a tendency that the effect of preventing exudation can be compatible with each other.

The concentration of the thermoplastic elastomer in the surface layer of the heat-sealed resin (D) layer opposite to the base film (A) side is 1 to 50% by mass, preferably 3 to 50% by mass in the resin composition (d). It is 30% by mass, particularly preferably 5 to 20% by mass. The side of the heat-sealing resin (D) layer opposite to the base film (A) side comes into contact with the inside, that is, the contents when the stand-up pouch is formed using the multilayer structure of the present invention. Therefore, if the content of the thermoplastic elastomer in the resin composition (d) becomes too large, there is a concern that the resin composition may seep into the contents in the ultra-high pressure treatment. preferable.

As the heat-sealing resin (D) layer in the present invention, the film of the resin composition (d), a coating film thereof, or the like can be used.

When there are a plurality of heat-sealing resin (D) layers, the total thickness of the heat-sealing resin (D) layer is, for example, 3 to 200 μm, preferably 10 to 110 μm, and 20 to 90 μm. More preferred. If the thickness is too thin, the sealing strength of the sealing portion tends to decrease, and if it is too thick, the rigidity tends to increase, and the opening property when filling the stand-up pouch with food or the like tends to decrease.

<Ethylene-vinyl ester copolymer saponified product (C) layer>
The ethylene-vinyl ester-based copolymer saponified product (C) layer is a layer mainly responsible for gas barrier properties.
The ethylene-vinyl ester-based copolymer saponified product (C) layer may be composed of an ethylene-vinyl ester-based copolymer saponified product (EVOH), and an EVOH resin composition containing any component other than EVOH. It may be a layer made of things.

EVOH is a resin usually obtained by saponifying a copolymer (ethylene-vinyl ester-based copolymer) of ethylene and a vinyl ester-based monomer, and is a water-insoluble thermoplastic resin. The polymerization method can also be carried out by using any known polymerization method, for example, solution polymerization, suspension polymerization or emulsion polymerization, but in general, solution polymerization using a lower alcohol such as methanol as a solvent is used. The obtained ethylene-vinyl ester copolymer can also be saponified by a known method. The EVOH produced in this manner is mainly composed of ethylene-derived structural units and vinyl alcohol structural units, and contains a small amount of vinyl ester structural units remaining without being saponified.

As the vinyl ester-based monomer, vinyl acetate is typically used because it is easily available on the market and has good impurity treatment efficiency during production. Examples of other vinyl ester-based monomers include vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versaticate and the like. Examples thereof include an aliphatic vinyl ester and an aromatic vinyl ester such as vinyl benzoate. Usually, an aliphatic vinyl ester having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms is used. Can be done. These are usually used alone, but a plurality of types may be used at the same time if necessary.

The ethylene content in EVOH is a value measured based on ISO 14663, preferably 20 to 60 mol%, more preferably 25 to 50 mol%, and particularly preferably 25 to 35 mol%. If the content is too low, the gas barrier property and melt moldability under high humidity tend to decrease, and if it is too high, the gas barrier property tends to decrease.

The degree of saponification of the vinyl ester component in EVOH is a value measured based on JIS K6726 (however, EVOH is a solution uniformly dissolved in a water / methanol solvent), and is preferably 90 to 100 mol%. It is more preferably 95 to 100 mol%, and particularly preferably 99 to 100 mol%. If the degree of saponification is too low, the gas barrier property, thermal stability, moisture resistance and the like tend to decrease.

The melt flow rate (MFR) (MFR) of EVOH (210 ° C., load 2,160 g) is preferably 0.5 to 100 g / 10 minutes, more preferably 1 to 50 g / 10 minutes, and particularly preferably 3 to 3. 35 g / 10 minutes. If the MFR is too large, the film-forming property tends to be deteriorated, and if it is too small, the melt viscosity tends to be too high and melt extrusion becomes difficult.

The EVOH used in the present invention may further contain a structural unit derived from the comonomer shown below, in addition to an ethylene structural unit and a vinyl alcohol structural unit (including an unsaken vinyl ester structural unit). .. Examples of the comonomer include α-olefins such as propylene, isobutene, α-octene, α-dodecene, and α-octadecene; 3-butene-1-ol, 4-pentene-1-ol, 3-butene-1, Hydroxy group-containing α-olefins such as 2-diols and esterified products thereof, hydroxy group-containing α-olefin derivatives such as acylated products; unsaturated carboxylic acids or salts thereof, partially alkyl esters, fully alkyl esters, nitriles, amides or anhydrous Substances; unsaturated sulfonic acids or salts thereof; vinyl silane compounds; vinyl chloride; styrene and the like.

Further, "post-denatured" EVOH-based resins such as urethanization, acetalization, cyanoethylation, and oxyalkyleneization can also be used.

Among the above-mentioned modified products, EVOH in which a primary hydroxyl group is introduced into the side chain by copolymerization is preferable in that it improves secondary moldability such as stretching treatment and vacuum / pneumatic molding, and among them, 1,2-. EVOH having a diol structure in the side chain is preferable.

The EVOH used in the present invention includes compounding agents generally blended with EVOH, for example, heat stabilizers, antioxidants, antistatic agents, colorants, ultraviolet absorbers, as long as the effects of the present invention are not impaired. Lubricants, plasticizers, light stabilizers, surfactants, antibacterial agents, desiccants, antiblocking agents, flame retardants, cross-linking agents, hardeners, foaming agents, crystal nucleating agents, antifogging agents, biodegradation additives, silanes A coupling agent, an oxygen absorber, or the like may be contained.

The heat stabilizer includes organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, and behenic acid, or organic acids thereof for the purpose of improving various physical properties such as thermal stability during melt molding. Alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts, etc.; or inorganic acids such as sulfuric acid, sulfite, carbonic acid, phosphoric acid, boric acid, etc., or these Examples thereof include alkali metal salts (sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc salts and the like.

Further, the EVOH used in the present invention may be a mixture with other EVOHs different from each other, and such other EVOHs have different ethylene content, different degree of saponification, and melt flow rate (MFR). ) (210 ° C., load 2,160 g) are different, other copolymerization components are different, and the amount of modification is different (for example, the content of 1,2-diol structural unit is different). it can.

Further, in the case of producing a packaging material for a package to be sterilized by ultra-high pressure treatment, the ethylene-vinyl ester-based copolymer saponified product (C) layer shall be composed of an EVOH resin composition containing a polyamide-based resin. Is preferable. In the polyamide resin, the amide bond can form a network structure by interacting with the hydroxyl group and / or ester group of EVOH, which can prevent the elution of EVOH during the ultrahigh pressure treatment.
As the polyamide resin, known ones can be used. For example, the same polyamide resin (B) as described below can be used. The content of the polyamide resin in the ethylene-vinyl ester copolymer saponified product (C) layer is, for example, preferably 1 to 40% by mass, more preferably 5 to 35% by mass.

The thickness of the ethylene-vinyl ester copolymer saponified product (C) layer is, for example, 1 to 30 μm, preferably 3 to 28 μm, and even more preferably 5 to 25 μm.

<Polyamide resin (B) layer>
In the present invention, it is preferable to provide the polyamide resin (B) layer from the viewpoint of enhancing the effect of the present invention and further improving the gas barrier property and the bag drop resistance.

As the polyamide-based resin constituting the polyamide-based resin (B) layer used in the present invention, a known polyamide-based resin can be used. Specifically, for example, polycapramid (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), polyundecane amide (nylon 11), polylauryl lactam (nylon 12). ) And the like. Examples of the copolymerized polyamide resin include polyethylenediamine adipamide (nylon 26), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), and polyhexamethylene sebacamide. (Nylon 610), Polyhexamethylene dodecamide (Nylon 612), Polyoctamethylene adipamide (Nylon 86), Polydecamethylene adipamide (Nylon 108), Caprolactam / Lauryl lactam copolymer (Nylon 6/12) , Caprolactam / ω-aminononanoic acid copolymer (nylon 6/9), caprolactam / hexamethylene diammonide adipate copolymer (nylon 6/66), lauryl lactam / hexamethylene diammonium adipate copolymer (nylon 12/66) ), Ethylenediamine adipamide / hexamethylene diammonide adipate copolymer (nylon 26/66), caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium sevacate copolymer (nylon 66/610), ethylene ammonium adipate / An aliphatic copolymer polyamide such as hexamethylene diammonium adipate / hexamethylene diammonium sevacate copolymer (nylon 6/66/610), polyhexamethylene isophthalamide, polyhexamethylene terephthalamide, polymethaxylylene adipamide. , Hexamethylene isophthalamide / terephthalamide copolymer, aromatic copolymer polyamide such as poly-p-phenylene terephthalamide, poly-p-phenylene 3-4'diphenyl ether terephthalamide, amorphous polyamide, above-mentioned polyamide Examples thereof include a carboxyl group such as methylenebenzylamine and metaxylene diamine, and a terminally modified polyamide whose terminal is modified with an amino group. A copolymerized polyamide resin is preferable, and an aliphatic copolymerized polyamide is particularly preferable, in that the effect of the present invention can be obtained more efficiently.

The thickness of the polyamide resin (B) layer in the present invention is preferably 1 to 100 μm, more preferably 1 to 80 μm, still more preferably 5 to 60 μm, and particularly preferably 10 to 40 μm. The polyamide resin (B) layer may be either a single layer or a plurality of layers, and in the case of a plurality of layers, the total thickness of the polyamide resin (B) layers in the multilayer structure is within the above range. All you need is.
If the thickness of the polyamide resin (B) layer is too thin, the recovery speed of the gas barrier property after ultra-high pressure treatment tends to be slow, and if it is too thick, the thickness of the entire stand-up pouch will be thickened as a result. As a result, the rigidity tends to increase, and the openness when the stand-up pouch is actually filled with food or the like tends to decrease.

<Other resin layers>
The multilayer structure for ultra-high pressure treatment of the present invention includes the above-mentioned base film (A), polyamide resin (B) layer, ethylene-vinyl ester copolymer saponified product (C) layer, and heat-sealed resin (D). In addition to the layer, another resin layer may be further provided, and the position where the other resin layer is laminated is arbitrary.

As the resin constituting the other resin layer, known ones can be used. Specific examples of such resins include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide resins such as various nylon resins, polyaramid resins, polypropylene resins, polyethylene resins, and polycarbonate resins. Resins, polyacetal resins, fluororesins and the like can be used.

The thickness of the other resin layer is preferably 1 to 100 μm, more preferably 5 to 90 μm, and particularly preferably 10 to 80 μm per layer.

<Adhesive resin layer>
The adhesive resin layer is provided to increase the adhesive strength of each layer. If the adhesive resin layers are not properly arranged, each layer tends to peel off with a slight force, making it unbearable for use as a stand-up pouch. The adhesive resin layer is provided at an arbitrary position.

A known adhesive resin can be used as the adhesive resin constituting the adhesive resin layer. Typical examples of the adhesive resin include a modified polyolefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof to a polyolefin resin by an addition reaction, a graft reaction, or the like. Can be done. For example, maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymer, maleic anhydride graft-modified ethylene-ethylacrylate copolymer, maleic anhydride graft. A modified ethylene-vinyl acetate copolymer, a maleic anhydride-modified polycyclic olefin resin, a maleic anhydride graft-modified polyolefin resin, and the like, and one or a mixture of two or more selected from these can be used.

The thickness of the adhesive resin layer is preferably 1 to 30 μm, more preferably 2 to 20 μm, and particularly preferably 3 to 10 μm per layer.

<Layer structure>
In a preferred embodiment of the multilayer structure of the present invention, the multilayer structure 10 has a base film (A) 1 and a heat-sealing resin (D) layer 4 as shown in FIG. ) 1 and the ethylene-vinyl ester-based copolymer saponified product (C) layer 3 are provided between the layer (D) 4.

As a specific layer structure, for example:
Base film (A) / polyamide resin (B) layer / EVOH (C) layer / polyamide resin (B) layer / heat seal resin (D) layer,
Base film (A) / polyamide resin (B) layer / EVOH (C) layer / polyamide resin (B) layer / EVOH (C) layer / heat seal resin (D) layer,
Base film (A) / Polyamide resin (B) layer / EVOH (C) layer / Polyamide resin (B) layer / EVOH (C) layer / Polyamide resin (B) layer / Heat seal resin (D) layer And so on. The adhesive resin layer can be arbitrarily provided in the above layer structure.

<Layer thickness>
In the present invention, the total thickness of the multilayer structure including the base film (A) is preferably 10 to 600 μm, more preferably 50 to 300 μm, still more preferably 70 to 280 μm, and particularly preferably 80 to 260 μm. If the total thickness is too thin, there is a tendency that the rigidity for maintaining independence cannot be obtained. On the other hand, if it is too thick, the rigidity tends to be too large, and the openness when actually filling the stand-up pouch with food or the like tends to decrease. The openness in the present invention refers to a characteristic that can be easily opened to a gas such as air blown to the mouth of a packaging bag when filling an object to be packaged, and can be used for automatic packaging.

Further, in the present invention, the thickness of the laminated body of each layer (hereinafter, also referred to as “multilayer material”) excluding the base film (A) cannot be unequivocally determined depending on the intended use, packaging form, required physical properties, and the like. , 5 to 500 μm, more preferably 10 to 300 μm, more preferably 20 to 180 μm, and particularly preferably 50 to 140 μm.

<Manufacturing method of multilayer structure>
Examples of the multilayer structure of the present invention include a method in which an ethylene-vinyl ester copolymer saponified product (C) layer and a heat-sealed resin (D) layer are sequentially laminated on a base film (A). Further, when laminating layers other than the above, a method of sequentially laminating each layer on the base film (A) so as to have a desired layer structure can be mentioned. Another example is a method in which a multilayer material is prepared in advance and the base film (A) and the multilayer material are laminated. Further, there is also a method in which the multilayer material is divided into a plurality of laminated bodies and the plurality of multilayer materials are sequentially laminated on the base film (A). From the viewpoint of reducing the cost required for laminating, a method of laminating the base film (A) having one laminating number and the multilayer material is preferable.

The multilayer material in the present invention can be produced by a melt forming method, a wet lamination method, a dry lamination method, a solvent-free lamination method, an extrusion lamination method, a coextrusion lamination method, an inflation method or the like. Above all, the melt molding method is preferable from the viewpoint of the environment that no solvent is used and the cost that laminating does not need to be performed in a separate process. As such a melt molding method, a known method can be adopted. For example, extrusion molding methods (T-die extrusion, tubular film extrusion, blow molding, melt spinning, profile extrusion, etc.), injection molding methods and the like can be mentioned. The melt molding temperature is usually appropriately selected from the range of 150 to 300 ° C.

Subsequently, a method of laminating the base film (A) and the multilayer material will be described.
As a method of laminating the base film (A) and the multilayer material, a laminating method used when manufacturing a normal packaging material, for example, a wet lamination method, a dry lamination method, a solvent-free lamination method, or an extrusion lamination method. , Coextrusion lamination method, inflation method, etc.
Therefore, in the present invention, when the above-mentioned lamination is performed, for example, the surface of the substrate to be laminated may be optionally subjected to pretreatment such as corona treatment, ozone treatment, and frame treatment, if necessary. it can.
Further, in the above, when extrusion lamination is performed, for example, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ionomer resin, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylate copolymer. Acid-modified polyolefin resin obtained by modifying a polyolefin resin such as coalescence, ethylene-propylene copolymer, methylpentene polymer, polyethylene or polypropylene with unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid and others. Etc. can be used as a resin for melt extrusion laminating.

At that time, for example, isocyanate-based, polyethyleneimine-based, or other anchor coating agent can be arbitrarily used as the adhesive aid.

Further, in the present invention, when dry laminating, for example, a solvent type, an aqueous type, an emulsion type or the like in which vinyl type, acrylic type, polyurethane type, polyamide type, polyester type, epoxy type and the like are the main components of the vehicle are laminated. An adhesive or the like can be used.

It should be noted that a plurality of types of base film (A) and a multilayer material (for example, base film (A) / base film (A) / multilayer material) can be configured. Further, a base film (A) / multilayer material / base film (A) can be configured. The base film (A) can be laminated in the same manner as described above.

<Upper yield point stress / Lower yield point stress>
The multilayer structure of the present invention has a ratio of the upper yield point stress to the lower yield point stress in a tensile test with respect to the film flow direction (MD) at a test speed of 200 mm / min, which is measured by the following measurement method: upper yield point. It is characterized in that the value of stress / yield point stress is 1.3 or less.
Measurement method: A multi-layer structure for ultra-high pressure treatment cut into strips with a width of 15 mm with the film flow direction in the vertical direction, and humidity-controlled (completely humidity-controlled) for 24 hours or more in an environment of 23 ° C. and 50% RH. Is used as a sample. Film flow direction (MD) in a tensile test (sample width 15 mm, distance between gauge points 50 mm, tensile speed 200 mm / min) using a tensile tester (“Autograph AGS-H” (trade name) manufactured by Shimadzu Corporation). The upper yield point stress, which is the maximum stress during elastic deformation in the stress (MPa) -strain (%) curve of, is obtained, and the lower yield point stress, which is the lowest stress during plastic deformation, is obtained. Calculate the point stress.

When the value of the upper yield point stress / the lower yield point stress is 1.3 or less, the innermost layers tend to overlap each other when the pouch is formed while maintaining an appropriate rigidity, so that the area in contact with the contents is in contact with the contents. Will increase, and whitening will be suppressed even if ultra-high pressure treatment is performed. Further, even if the multilayer structure having the upper yield point stress / lower yield point stress value of 1.3 or less is the innermost layer portion that does not come into contact with the contents and forms a gap when it is made into a pouch. Since the voids do not disperse and tend to gather in a part, whitening is unlikely to occur.
When the value of the upper yield point stress / the lower yield point stress exceeds 1.3, appropriate rigidity is not imparted, the independence is impaired, and the whitening suppressing effect may not be achieved .

To adjust the value of the upper yield point stress / lower yield point stress, (1) mix an appropriate amount of thermoplastic elastomer in each layer; (2) adjust the thickness of each layer to be thin; (3) very flexible. Laminating resin layers; (4) Dividing a highly rigid resin layer (for example, polyamide layer, EVOH resin layer) (providing in multiple layers), etc., but self-supporting and mechanical strength (seal) The method (1) is preferable from the viewpoints of strength, piercing strength, abrasion resistance, etc.), prevention of elution of resin components, ease of film formation, and the like. Above all, the value of the upper yield point stress / the lower yield point stress can be adjusted by adjusting the amount of the thermoplastic elastomer in the heat seal resin (D) layer. Separately from this, the value of the upper yield point stress / the lower yield point stress can be adjusted by adding the thermoplastic elastomer to the base film (A). In this case, the proportion of the thermoplastic elastomer in the base film (A) is, for example, 1 to 30% by mass, preferably 5 to 25% by mass.

(Packaging body)
The multilayer structure of the present invention can be used as various known packages for ultra-high pressure treatment, and can be suitably used as a stand-up pouch as described above.

(Stand-up pouch)
The stand-up pouch in the present invention is formed by the above-mentioned multilayer structure of the present invention. The stand-up pouch has a body portion and a bottom portion provided in a direction perpendicular to the body portion, and has rigidity that allows it to stand on its own when filled with the contents.

<Structure of stand-up pouch>
FIG. 2 is an overall perspective view showing an example of the stand-up pouch of the present invention. The stand-up pouch 5 of the present invention is composed of two front and back body sheets 6 and 6 and a bottom sheet 7. The body sheet 6 and the bottom sheet 7 are flexible sheets, and are obtained by cutting the multilayer structure of the present invention into a desired size. The multilayer structure of the present invention is arranged so that the multilayer material side is located inside, that is, the base film (A) 1 side is located outside.
The bottom sheet 7 is inserted between the lower parts of the two body sheets 6 and 6 in a folded state, and the lower edge of the body sheets 6 and 6 and the peripheral edge of the bottom sheet 7 are sealed to form the bottom. The seal portion 8 is formed, and the side seal portions 9 are formed by sealing the left and right edges of the stacked body sheets 6 and 6. As a result, the bottom sheet 7 expands to become a stand-up pouch with the contents filled.

In the present invention, with the upper portion of the stand-up pouch 5 open, the contents such as desired food and drink are filled through the opening. Next, the upper opening is heat-sealed to form a top-sealed portion or the like to produce a packaged semi-finished product, and then the packaged semi-finished product is subjected to ultra-high pressure treatment to produce products having various forms. It is something that can be done.

The stand-up pouch in the present invention can be provided with a joint at an arbitrary position or can be given a design.
The dimensions of the stand-up pouch are the dimensions of the multilayer structure portion that does not include the joints and the like. For example, the width W is 50 to 1000 mm, preferably 100 to 500 mm, particularly preferably 100 to 200 mm, and the height H is 50. It is ~ 1000 mm, preferably 100 to 500 mm, particularly preferably 150 to 300 mm, and the bottom depth D is 10 to 500 mm, preferably 20 to 300 mm, particularly preferably 30 to 100 mm. The ratio (H / W) of the height H to the width W is, for example, 0.2 to 5, preferably 1 to 3, particularly preferably greater than 1 and 1.5 or less. Within such a range, the visibility and display efficiency of the stand-up pouch tend to be improved. The dimensions can be made into desired dimensions by adjusting the sizes of the body sheet 6 and the bottom sheet 7 constituting the stand-up pouch. In order to make the pouch self-supporting, the bottom sheet is inserted in a folded state, but in the self-supporting state of the pouch, the bottom sheet is opened from the folded state. Although the sheet 7 itself is rectangular, the bottom sheet 7 is formed into a substantially elliptical shape by adjusting the heat seal portion in order to make the depth D of the bottom of the stand-up pouch within the above range, and the bottom sheet 7 is formed. As for the substantially elliptical size, the major axis is the same size as the width of the body sheet 6, and the minor axis is preferably 10 to 500 mm, preferably 20 to 300 mm, particularly preferably 30 to 100 mm. Such a minor diameter is usually 1 to 1.5 times the bottom depth D.

Next, a specific manufacturing method of the stand-up pouch in the present invention will be described.

<Manufacturing method of stand-up pouch>
If desired, gravure printing or the like is performed on one side of the base film (A) using a gravure ink using a urethane resin as a binder, and a multilayer material is applied to the printed side of the base film (A), for example, dry laminating. It is bonded by the dry laminating method via an adhesive for printing. In this case, the adhesive is applied to the entire surface of the printed surface and adhered to form a multilayer structure. The formed multilayer structure becomes a base film (A) / printing layer / multilayer material.

Next, in order to form the stand-up pouch, the multilayer structure of the present invention is slit to a predetermined width to form a body sheet and a bottom sheet. As shown in FIG. 2, the two body sheets 6 and 6 are stacked so that the multilayer material sides face each other, and the bottom sheet 7 is sandwiched between the lower portions of the two body sheets 6 and 6 to form the bottom sheet. The left and right sides are sealed, the bottom seal portion 8 and the left and right side seal portions 9 are formed, respectively, and the top portion, that is, the stand-up pouch 5 having an open upper portion is formed. At this time, a plurality of gap portions formed of unsealed portions surrounded by the sealed portions in the longitudinal direction are formed in at least one side seal portion 9.

Next, air is press-fitted into the gap. A method of forming an air-sealed portion will be briefly described. A press-fitting hole for press-fitting air is formed at the longitudinal end of the formed gap. The press-fitting hole may be a hole that penetrates the body sheet 6. In order to press-fit air from the press-fit hole, another press-fit nozzle is brought into contact with the press-fit hole, and while air is press-fitted into the gap, when the target amount of air is reached, the air is sealed at a position shifted from the press-fit hole and filled with air. Form a part. Then, the press-fit hole is sealed. That is, the press-fitting hole is closed by the heat seal layer to form an air-sealed portion.

Next, the stand-up pouch 5 of the present invention is formed by expanding the bottom sheet of the packaging bag having an open top, filling the contents, and then sealing the top to form and seal the top seal. Is formed. Further, although the air-filled portion is formed in one side seal portion 9, it may be formed in both side seal portions 9. By forming the air-filled portions in both side seal portions 9, the independence can be further improved.

The stand-up pouch formed in this way improves independence, and even if the contents are used and the contents are reduced, the side seal is not broken or the packaging bag is not deformed due to the crushing of the waist. On the other hand, since it can be bent between the air-sealed portion and the air-filled portion, the volume of the packaging bag can be reduced and stored. Further, even when the bag is discarded after use, the volume of the packaging bag can be reduced by bending and folding between the air-sealed portion and the air-filled portion.
The stand-up pouch in the present invention can be obtained by using the multi-layer structure for ultra-high pressure treatment of the present invention in at least one part of the body sheet and the bottom sheet. The stand-up pouch made of the multilayer structure of the present invention, which uses the multilayer structure of the present invention for all of the body sheet and the bottom sheet, is most preferable in that the effect of the present invention can be obtained more effectively.

<Contents of stand-up pouch>
The contents to be filled and packaged in the packaging bag constituting the stand-up pouch according to the present invention include, for example, cooked foods, marine products, frozen foods, simmered foods, rice cakes, liquid soups, seasonings, drinking water, and the like. Various foods and drinks, specifically, liquid foods such as curry, stew, soup, meat sauce, hamburger, meatballs, sardines, oden, porridge, jelly-like foods, seasonings, water, etc. Food and drink can be mentioned.

When the multilayer structure of the present invention is used as a stand-up pouch, even if a gas is mixed in when the contents are sealed and a head space is generated in the stand-up pouch, the upper yield point stress / descending yield point of the multilayer structure Since the stress value is 1.3 or less, the area of contact between the liquid or solid and the innermost layer is the maximum, that is, the area of the innermost layer in contact with the void inside the stand-up pouch is the smallest, and the ultrahigh pressure Whitening due to treatment can be sufficiently suppressed.
In particular, in the present invention, when the content contains a liquid, the effect of the present invention tends to be obtained more effectively.

<Ultra high pressure treatment>
The ultra-high pressure treatment package having the multilayer structure of the present invention is subjected to ultra-high pressure treatment. Here, the ultra-high pressure treatment referred to in the present invention is a sterilization treatment performed under ultra-high pressure conditions using water as a medium, for example.
Compared with the general retort sterilization treatment, the ultra-high pressure treatment has the advantage that the color, aroma and nutrients of the contents are not impaired because the treatment can be performed under ultra-high pressure and low temperature conditions. ..

The pressure used in the ultra-high pressure treatment is usually 100 MPa or more, preferably 100 to 900 MPa, more preferably 200 to 800 MPa, and particularly preferably 500 to 700 MPa.

The temperature adopted in the ultra-high pressure treatment is usually -20 to 60 ° C, preferably -10 to 40 ° C, and particularly preferably 0 to 30 ° C.

In the above description, the multilayer structure of the present invention has been described as a stand-up pouch, but the multilayer structure of the present invention may be used as a packaging body having a shape such as a pouch, a tray, or a cup that is not self-supporting. Can be done.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the description of Examples as long as the gist of the present invention is not exceeded.
In the example, "part" means a mass reference.

<Calculation method of upper yield point stress / lower yield point stress>
The multilayer structure was cut into strips having a width of 15 mm with the film flow direction in the vertical direction, and the sample was subjected to humidity control (complete humidity control state) for 24 hours or more in an environment of 23 ° C. and 50% RH. Using "Autograph AGS-H" (trade name) manufactured by Shimadzu Corporation, the sample is sandwiched with a distance between gauge points of 50 mm, and a tensile test is performed in the MD direction at a test speed of 200 mm / min. The upper yield point stress, which is the maximum stress during elastic deformation in the stress (MPa) -strain (%) curve, is obtained, and the lower yield point stress, which is the minimum stress during plastic deformation, is obtained, and the upper yield point stress / lower The yield point stress was calculated.

<Whitening test during ultra-high pressure treatment>
The stand-up pouch was pressure-treated with an ultra-high pressure sterilizer (“Wave6000” (trade name) manufactured by Hyperbaric) under the following conditions.
Condition 1: Treatment pressure: 600 MPa, Treatment temperature: 17 ° C., Treatment time: 10 minutes Condition 2: Treatment pressure: 600 MPa, Treatment temperature: 7 ° C., Treatment time: 5 minutes Whitening occurs in the head space above the pouch after ultra-high pressure treatment. The presence or absence of was visually evaluated. The evaluation criteria are as follows.
〔Evaluation criteria〕
Whitening "None": Whitening could not be confirmed visually.
Whitening is "slightly present": Whitening was visually confirmed in a narrow area.
Whitening was "significantly present": Clear whitening was visually confirmed over a wide area.

(Example 1)
[Constituent material of multilayer structure]
-Base film (A): Stretched polyethylene terephthalate film (PET) ("Grade: FE2001A" manufactured by Futamura Chemical Co., Ltd., thickness: 12 μm)
-Polyamide resin (B): Nylon 6-66 (DSM "Novamid", grade: 2430J)
Ethylene-vinyl ester copolymer saponified product (EVOH) (C): Ethylene content: 29.4 mol%, saponification degree: 99.7 mol%, MFR: 5.2 g / 10 minutes (230 ° C., EVOH with a load of 2160 g)
-Heat seal resin (D): A mixture of polyolefin resin and thermoplastic elastomer
Polyolefin resin: Polypropylene ("Novatec PP" manufactured by Japan Polypropylene Corporation, grade: BC6DRF)
Thermoplastic elastomer: Ethylene-butene random copolymer (“Toughmer” manufactured by Mitsui Chemicals, Inc., grade: A4085S, density 0.89 g / cm ³ , flexural modulus 30 MPa, MFR (210 ° C, 2160 g load): 5.2 g / 10min)
-Adhesive resin: Polypropylene adhesive resin ("Modic" manufactured by Mitsubishi Chemical Corporation, grade: P553A)

(Content of thermoplastic elastomer)
Heat seal resin (D) layer 1: 20 parts by mass of thermoplastic elastomer was added to 80 parts by mass of polyolefin resin.
Heat-sealed resin (D) layer 2: 10 parts by mass of thermoplastic elastomer was added to 90 parts by mass of polyolefin resin.

(Method of adding thermoplastic elastomer)
At the time of film formation by the T-die method, a predetermined amount of thermoplastic elastomer was added to the polyolefin resin by dry blending in advance.

[Manufacturing of multilayer structure]
First, a multilayer material was produced, and the transparent multilayer structure (1) was produced by laminating the multilayer material and the base film (A).

(Manufacturing of multilayer material)
A film is formed by the T-die method, and the polyamide resin (B) layer (10 μm) / EVOH (C) layer (20 μm) / polyamide resin (B) layer (10 μm) / adhesive resin layer (5 μm) / heat seal resin A multilayer material of (D) layer 1 (45 μm) / heat-sealed resin (D) layer 2 (10 μm) was obtained.

(Lamination of multilayer material and base film)
The base film (A) and the multilayer material obtained above are combined with an adhesive for dry laminating (main agent: "TM-242A" manufactured by Toyo Morton Co., Ltd., curing agent: "CAT-RT37L" manufactured by Toyo Morton Co., Ltd., the above main agent: A multilayer structure was prepared by dry laminating with the above curing agent: ethyl acetate = 17: 1.5: 19.2).
Laminating conditions: Laminated in an environment of 20 ° C and aged at 40 ° C for 48 hours.

The structure of the obtained multilayer structure (1) is PET (12 μm) / polyamide resin (B) layer (10 μm) / EVOH (C) layer (20 μm) / polyamide resin (B) layer (10 μm) / adhesion. The resin layer (5 μm) / heat-sealed resin (D) layer 1 (45 μm) / heat-sealed resin (D) layer 2 (10 μm). The total thickness of the obtained multilayer structure was 112 μm.
The content of the thermoplastic elastomer in the resin composition (d) constituting the surface layer on the side opposite to the base film (A) side in the entire heat-sealed resin (D) layer of the multilayer structure is 10% by mass. The content of the thermoplastic elastomer in the resin composition (d) constituting the surface layer on the base film (A) side was 20% by mass. The concentration of the thermoplastic elastomer of the resin composition (d) in the entire heat-sealed resin (D) layer of the multilayer structure is 18.2% by mass as the value obtained by multiplying the concentration of each layer by the thickness ratio of each layer. Met.

[Making a stand-up pouch]
Using the obtained multilayer structure (1), a stand-up pouch container (width 140 mm × height 180 mm × bottom minor diameter 60 mm, bottom depth 58 mm) was prepared. Put 300cc of water in the obtained pouch container, provide a head space so that the pouch contains 3% or more (specifically 5%) of the content, heat seal the upper side, and make a stand-up pouch. Made.

(Example 2)
Using the multilayer structure (1) prepared in Example 1, a stand-up pouch container (width 140 mm × height 180 mm × bottom minor diameter 60 mm, bottom depth 58 mm) was prepared. 300 cc of water was put into the obtained pouch container, the head space was reduced so that air was not contained in the pouch (less than 3% of the content), and the upper side was heat-sealed to prepare a stand-up pouch. ..

(Comparative Example 1)
[Constituent material of multilayer structure]
-Base film (A): Stretched polyethylene terephthalate film (manufactured by Futamura Chemical Co., Ltd., grade: FE2001A, thickness: 12 μm)
-Polyamide resin (B): Nylon 6 ("UBE nylon" manufactured by Ube Industries, Ltd., grade: 1020B)
-EVOH (C): Ethylene content: 29.4 mol%, saponification degree: 99.7 mol%, MFR: 5.2 g / 10 minutes (230 ° C., load 2160 g) EVOH
-Heat seal resin (D): Polypropylene ("Novatec PP" manufactured by Japan Polypropylene Corporation, grade: BC6DRF)
-Adhesive resin: Polypropylene adhesive resin ("Modic" manufactured by Mitsubishi Chemical Corporation, grade: P614V)

[Manufacturing of multilayer structure]
First, a multilayer material was produced, and the multilayer material and the base film (A) were laminated to produce a transparent multilayer structure (2).

(Manufacturing of multilayer material)
A film is formed by the T-die method, and the polyamide resin (B) layer (10 μm) / EVOH (C) layer (20 μm) / polyamide resin (B) layer (10 μm) / adhesive resin layer (5 μm) / heat seal resin A multilayer material of layer (D) (55 μm) was obtained.

(Lamination of multilayer material and base film)
The base film (A) and the multilayer material obtained above are combined with an adhesive for dry laminating (main agent: "TM-242A" manufactured by Toyo Morton Co., Ltd., curing agent: "CAT-RT37L" manufactured by Toyo Morton Co., Ltd., the above main agent: A multilayer structure was prepared by dry laminating with the above curing agent: ethyl acetate = 17: 1.5: 19.2).
Laminating conditions: Laminated in an environment of 20 ° C and aged at 40 ° C for 48 hours.

The structure of the obtained multilayer structure (2) is PET (12 μm) / polyamide resin (B) layer (10 μm) / EVOH (C) layer (20 μm) / polyamide resin (B) layer (10 μm) / adhesion. The resin layer (5 μm) / heat-sealed resin (D) layer (55 μm). The total thickness of the obtained multilayer structure was 112 μm.

[Making a stand-up pouch]
Using the obtained multilayer structure (2), a stand-up pouch container (width 140 mm × height 180 mm × bottom minor diameter 60 mm, bottom depth 58 mm) was prepared. Put 300cc of water in the obtained pouch container, provide a head space so that the pouch contains 3% or more (specifically 5%) of the content, heat seal the upper side, and make a stand-up pouch. Made.

(Comparative Example 2)
Using the multilayer structure (2) prepared in Comparative Example 1, a stand-up pouch container (width 140 mm × height 180 mm × bottom minor diameter 60 mm, bottom depth 58 mm) was prepared. 300 cc of water was put into the obtained pouch container, the head space was reduced so that air was not contained in the pouch (less than 3% of the content), and the upper side was heat-sealed to prepare a stand-up pouch. ..

The upper yield point stress / lower yield point stress was calculated for the multilayer structures produced in Examples 1 and 2 and Comparative Examples 1 and 2, and the stand-up pouch was subjected to a whitening test during ultra-high pressure treatment.
The results are shown in Table 1.

In the conventional multilayer structure (2), whitening occurred in proportion to the size of the head space in Comparative Example 1 and Comparative Example 2 in the case where the head space caused by the gas was present. The haze value of the bleached portion was 66%, and the haze value of the unbleached portion was 61%. The haze value of the unwhitened portion was the same as the haze value of the multilayer structure not subjected to the ultra-high pressure treatment.

On the other hand, in the multilayer structure (1) having the specific flexibility of the present invention, when Example 1 and Example 2 are compared, in Example 1, although the head space is larger than that in Example 2, whitening occurs. Did not occur, and whitening did not occur similarly when the head space was small.
From the above results, the effectiveness of the present invention is clear.

1 Base film (A)
3 Ethylene-vinyl ester copolymer saponified product (C) layer (EVOH (C) layer)
4 Heat seal resin (D) layer 5 Stand-up pouch 6 Body sheet 7 Bottom sheet 8 Bottom seal 9 Side seal 10 Multi-layer structure for ultra-high pressure treatment

Claims (6)

A multi-layer structure for ultra-high pressure processing used for processing under ultra-high pressure of 100 MPa or more.
It has a base film (A), an ethylene-vinyl ester copolymer saponified product (C) layer and a heat seal resin (D) layer, and the base film (A) and the heat seal resin (D) layer The ethylene-vinyl ester copolymer saponified product (C) layer is located between the two.
The multilayer structure for ultra-high pressure treatment further has a polyamide resin (B) layer and an adhesive resin layer.
Ratio of upper yield point stress to lower yield point stress in tensile test with respect to film flow direction (MD) at test speed of 200 mm / min: upper yield point stress / lower yield point stress is 1.3 or less and greater than 1. A multi-layer structure for ultra-high pressure processing. The multilayer structure for ultra-high pressure treatment according to claim 1, wherein the upper yield point stress / lower yield point stress is 1.2 to 1.3 . The multilayer structure for ultra-high pressure treatment according to claim 2, wherein the heat-sealing resin (D) layer is made of a resin composition (d) containing a thermoplastic elastomer. The multilayer structure for ultra-high pressure treatment according to any one of claims 1 to 3, wherein the thickness is 10 to 600 μm. An ultra-high pressure processing package having the ultra-high pressure processing multilayer structure according to any one of claims 1 to 4. A method for treating an ultra-high pressure processing package according to claim 5, wherein the ultra-high pressure processing package is processed at a pressure of 100 to 900 MPa.

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