JP3784511B2 - Multilayer film for thermoforming and thermoforming container - Google Patents

Description

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【発明の効果】
本発明の熱成形用フィルムあるいはシート等は、熱成形性が良好であり、ガスバリア性、力学特性に優れた熱成形容器を提供することができる。かかる熱成形容器は、外観が良好で、力学性能に優れ、優れたガスバリア性を保有するので、各種包装容器として優秀な性能を有している。[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a thermoforming multilayer film, sheet and the like excellent in gas barrier properties, thermoformability, mechanical properties and appearance, thermoforming containers formed by thermoforming them, and resin compositions used for them.
[0002]
[Prior art]
An ethylene-vinyl alcohol copolymer (EVOH) is suitably used as a material for packaging contents such as foods and pharmaceuticals where maintenance of quality is important. There are various forms of packaging containers using such EVOH, and among them, containers obtained by thermoforming a multilayer body having an EVOH layer are widely used, and they can be used as thin films or relatively thick sheets. It is also used as a thing.
[0003]
First, the prior art regarding a film-like thermoformed container will be described. For example, ham, sausage, red meat, processed meat, etc. need to protect the quality of meat until it is used by consumers. In particular, oxygen promotes the degradation of such meat quality, so it is most important to properly shield meat from oxygen for long periods of time in order to keep the meat fresh. And as a packaging form for that purpose, for example, a method of making a pouch etc. by making a film having improved strength and barrier properties by biaxial stretching into a multi-layer structure by lamination, or by heating and shrinking the stretched film once A method of closely contacting the contents with no gap is mentioned.
[0004]
2. Description of the Related Art In recent years, a packaging form in which a film is heated and filled with a three-dimensionally shaped film container with air or a plug, and its upper surface is sealed with a film has been actively used. The reason is that the state of the contents and the shape can be clearly communicated to the consumer by making the container shape suitable for the form of the contents. Another reason is that it is easy to provide a display unit for contents from the viewpoint of selling products that comply with the recently enforced PL Law. In addition, by adopting a uniform shape, it can be easily arranged on the store shelves.
[0005]
Polyvinylidene chloride is one of the materials with excellent oxygen permeation prevention performance used for thermoforming applications of such multilayer films, but from the viewpoint of environmental protection because it is a resin containing a halogen element. There is concern about its use as a packaging material. On the other hand, a multilayer film including a nylon layer is also used for this purpose from the viewpoint of oxygen permeation prevention performance and thermoformability. However, due to the recent demand for further extension of the shelf life of food, more excellent oxygen There is a demand for anti-permeation performance.
[0006]
EVOH is an example of a material that has excellent oxygen permeation-preventing performance and is less problematic from the viewpoint of environmental protection. However, the corner portion becomes extremely thin due to thermoforming, streaks, wrinkles, There is a drawback that impact resistance is lowered. Also, in the case of the shape of the container, for example, an extremely deep shape, the film may burst during thermoforming, or the intersection or corner of the side and bottom of the molded product may not exactly follow the mold. There are also problems. In particular, a thin film-like laminate is likely to cause such a problem as compared with a relatively thick sheet-like laminate, and is difficult to mold.
[0007]
Although no specific method has been reported as means for improving the thermoformability problem as described above, as an analogy means, a method of laminating nylon to the EVOH layer, and a method including nylon to EVOH are included. A method of blending various resins (US Pat. No. 4,079,850) has been reported, but the thermoformability in these cases is not satisfactory as compared with the case where nylon is used alone. In addition, when EVOH is blended with various resins such as nylon, gas barrier properties are deteriorated, heat stability during film formation is problematic, and transparency is lowered depending on the type and dispersion state of the resin. It also has the problem of
[0008]
Next, the prior art regarding a relatively thick sheet-like thermoformed container will be described. 2. Description of the Related Art In the field of food packaging, cups and trays that can be eaten and consumed as they are without being transferred to other containers after purchase of products at stores are actively used. Specific examples include containers for packaging jelly, pudding, yogurt, juice, and the like. Containers such as miso cups that can be used as storage containers without transferring their contents to other containers are also used.
[0009]
In general, thermoformed containers are used as these packaging materials. Thermoformed containers are required to have form stability and oxygen barrier properties in order to maintain the quality of the contents. A typical example of the resin used from the viewpoint of maintaining the form is a homopolymer of polypropylene (hereinafter sometimes abbreviated as “homopolypropylene”) having an excellent balance of rigidity and impact resistance. In order to prevent oxidative deterioration of the contents, EVOH having an excellent oxygen barrier property is generally used as a barrier layer.
[0010]
However, due to insufficient thermoformability of EVOH, cracks and wave patterns are generated on the side surfaces of the container, and a thermoformed container having an excellent appearance may not be obtained. In order to improve these thermoformability and impact resistance, various proposals such as a method of adding nylon to EVOH (US Pat. No. 4,079,850) have been made, but the thermoformability is not sufficient, and the gas barrier property is lowered. However, there is a problem in thermal stability at the time of film formation, or there is a problem in that the transparency is lowered depending on the type and dispersion state of the resin, and it has not been improved sufficiently.
[0011]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to provide a multilayer film for thermoforming, a sheet, etc. excellent in gas barrier properties, thermoformability, mechanical properties and appearance, and a thermoformed container formed by thermoforming them, and to them. The object is to provide a resin composition.
[0012]
[Means for Solving the Problems]
The above-mentioned object is that an ethylene- (meth) acrylic acid copolymer 40-1 having an ethylene content of 20-60 mol%, EVOH 60-99 wt% with a saponification degree of 90% or more, and a (meth) acrylic acid content 1-30 wt%. A resin composition layer comprising ethylene oxide (meth) acrylic acid copolymer particles dispersed in an EVOH matrix, the total thickness is 50 to 300 μm, and the resin composition layer thickness is 3 to 50 μm. Multi-layer film for thermoforming In the resin composition layer, the ethylene- (meth) acrylic acid copolymer particles are dispersed in a cylindrical shape extended in a uniaxial direction parallel to the film surface, and the surface is perpendicular to the uniaxial direction. The multilayer film for thermoforming having an average diameter of a particle cross section of 0.2 to 1.3 μm when cut by Is achieved by providing
[0013]
In particular, the multilayer film for thermoforming having a ratio (A) / (B) of MFR (A) of EVOH and MFR (B) of an ethylene- (meth) acrylic acid copolymer of 0.1 to 5.0 The This is preferably achieved by providing.
[0014]
A preferred embodiment of such a multilayer film for thermoforming includes an embodiment having a resin composition layer and a heat seal layer, and in particular, a polypropylene resin layer and / or a polyamide resin layer in addition to the resin composition layer and the heat seal layer. The aspect which has is mentioned as a suitable thing. Moreover, it is also suitable that the haze of such a multilayer film for thermoforming is 10% or less.
[0015]
The object of the present invention can also be achieved by providing a thermoformed container formed by thermoforming the above multilayer film. In particular, the total thickness of the container at the thickest part is T μm, and the thinnest is the thinnest. This is preferably achieved by providing a thermoformed container that satisfies the following formulas (1) to (3) where the total layer thickness in the portion is t μm and the drawing ratio of the container is S.
5S ≦ T / t ≦ 30S (1)
50 ≦ T ≦ 300 (2)
t ≧ 20 (3)
However, the squeezing ratio S of the container is a value represented by the following formula (4).
S = (depth of container) / (diameter of the largest circle inscribed in the opening of the container) (4)
[0016]
In particular, in the thinnest part of the container, the ethylene- (meth) acrylic acid copolymer particles dispersed in the EVOH matrix are elongated in a two-dimensional direction parallel to the film surface. A thermoformed container that is dispersed in shape and has an average thickness of a particle cross section when cut by a plane perpendicular to the film surface is 0.05 to 1.0 μm.
[0017]
Another object of the present invention is to provide ethylene- (meth) acrylic acid copolymer having an ethylene content of 20 to 60 mol%, EVOH having a saponification degree of 90% or more of 60 to 99% by weight and a (meth) acrylic acid content of 1 to 30% by weight. A multilayer structure for thermoforming comprising a resin composition layer comprising 40 to 1% by weight of a coalescence, in which ethylene- (meth) acrylic acid copolymer particles are dispersed in a matrix of EVOH When the ethylene- (meth) acrylic acid copolymer particles are dispersed in a cylindrical shape extended in a uniaxial direction parallel to the surface of the multilayer structure, and cut along a plane perpendicular to the uniaxial direction Multilayer structure for thermoforming having an average particle cross-sectional diameter of 0.2 to 1.3 μm It is also achieved by providing.
[0019]
The object of the present invention can also be achieved by providing a thermoformed container formed by thermoforming the above multilayer structure. In particular, the total thickness of the thickest portion of the container is T μm, This is suitably achieved by providing a thermoformed container that satisfies the following formulas (5) to (7), where the total layer thickness in the thin portion is t μm and the drawing ratio of the container is S.
S ≦ T / t ≦ 20S (5)
300 <T ≦ 3000 (6)
t ≧ 100 (7)
However, the squeezing ratio S of the container is a value represented by the following formula (4).
S = (depth of container) / (diameter of the largest circle inscribed in the opening of the container) (4)
[0020]
Furthermore, the object of the present invention is an ethylene- (meth) acrylic acid copolymer 40 having an ethylene content of 20 to 60 mol%, EVOH having a saponification degree of 90% or more of 60 to 99% by weight and a (meth) acrylic acid content of 1 to 30% by weight. ~ 1% by weight in EVOH matrix With an average particle size of 0.3 to 1.5 μm It is also achieved by providing a resin composition in which ethylene- (meth) acrylic acid copolymer particles are dispersed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The EVOH of the present invention can be obtained by saponifying a copolymer composed of ethylene and vinyl ester using an alkali catalyst or the like.
A typical vinyl ester is vinyl acetate, but other fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can also be used.
[0023]
The ethylene content of EVOH in the present invention is 20 to 60 mol%, preferably 25 to 50 mol%, more preferably 25 to 45 mol%. Here, when EVOH is composed of a blend of two or more types of EVOH having different ethylene contents, the average value calculated from the blending weight ratio is taken as the ethylene content.
When the ethylene content is less than 20 mol%, the gas barrier property under high humidity is lowered and the melt moldability is also deteriorated. If it exceeds 60 mol%, sufficient gas barrier properties cannot be obtained.
[0024]
Further, the saponification degree of the vinyl ester component of EVOH of the present invention is 90% or more, preferably 95% or more, and more preferably 98% or more. Here, when EVOH is composed of a blend of two or more types of EVOH having different saponification degrees, the average value calculated from the blending weight ratio is defined as the saponification degree.
When the degree of saponification is less than 90 mol%, not only the gas barrier property at high humidity is lowered, but also the thermal stability of EVOH is deteriorated, and a gel tends to be generated in the molded product.
[0025]
Further, EVOH can be copolymerized with a small amount of other monomers as long as the object of the present invention is not impaired. Examples of monomers that can be copolymerized include α-olefins such as propylene, butene, isobutene, 4-methylpentene-1, hexene, octene, unsaturated carboxylic acids such as itaconic acid, methacrylic acid, acrylic acid, and maleic anhydride. Examples thereof include acids, salts thereof, partial or complete esters thereof, nitriles thereof, amides thereof, anhydrides thereof, vinylsilane compounds such as vinyltrimethoxysilane, unsaturated sulfonic acids, salts thereof, alkylthiols, and vinylpyrrolidone.
[0026]
In particular, when EVOH contains 0.0002 to 0.2 mol% of a vinylsilane compound as a copolymerization component, the consistency of the melt viscosity with the base resin during coextrusion is improved, and a homogeneous coextruded multilayer film In addition, it is possible to improve the dispersibility when EVOHs are used for blending, and is effective in improving moldability and the like. Here, examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, and γ-methacryloxypropylmethoxysilane. Of these, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.
[0027]
The phosphorus compound concentration in the EVOH of the present invention is preferably in the range of 1 to 200 ppm, preferably 2 to 150 ppm, and most preferably 5 to 100 ppm in terms of phosphorus element weight from the viewpoint of film forming property and thermal stability. .
[0028]
Furthermore, the addition of alkali metal ions such as sodium ions, potassium ions and lithium ions in an amount of 10 to 500 ppm relative to EVOH in terms of metal weight is also effective for improving the interlaminar adhesion and compatibility. It is. Examples of alkali metal compounds include monovalent metal aliphatic carboxylates, aromatic carboxylates, phosphates, metal complexes, and the like. Specific examples include sodium acetate, potassium acetate, sodium phosphate, and phosphoric acid. Examples thereof include lithium, sodium stearate, potassium stearate, ethylenediaminetetraacetic acid sodium salt, and preferably sodium acetate, potassium acetate, and sodium phosphate.
[0029]
The preferred melt flow rate (MFR) (value measured at 210 ° C. under a load of 2160 g) of EVOH used in the present invention is preferably 0.1 to 50 g / 10 min, and most preferably 0.5 to 20 g. / 10 minutes. Here, when EVOH consists of a blend of two or more types of EVOH having different melt flow rates, the average value calculated from the blend weight ratio is taken as the melt flow rate.
[0030]
As the EVOH used in the present invention, it is preferable to blend two or more types of EVOH having different ethylene contents and / or saponification degrees.
In particular, EVOH comprises a mixture of two types of EVOH (a) and (b) having different ethylene contents, wherein (a) has an ethylene content of 20 to 45 mol% and (b) has an ethylene content of 45 to 65 mol%. It is favorable that the difference in ethylene content between (a) and (b) is 8 mol% or more and the blending weight ratio {(a) / (b)} is 2/1 to 50/1. It is preferable for achieving both gas barrier properties and thermoformability.
[0031]
At this time, the ethylene content of EVOH (a) is preferably 20 to 45 mol%. More preferably, it is 25-42 mol%, More preferably, it is 30-40 mol%. When the ethylene content of EVOH (a) is less than 20 mol%, the thermoformability is deteriorated, and when it exceeds 45 mol%, the gas barrier property is lowered.
[0032]
Moreover, it is preferable that the ethylene content of EVOH (b) is 45-65 mol%. More preferably, it is 47-62 mol%, More preferably, it is 50-60 mol%. When the ethylene content of EVOH (b) is within such a range, the thermoformability is sufficiently improved.
[0033]
Furthermore, the difference in ethylene content between EVOH (a) and (b) is preferably 8 mol% or more. More preferably, it is 12 mol% or more, and more preferably 15 mol% or more. When the difference in the ethylene content of EVOH (a) is less than 8 mol%, the effect of improving thermoformability is small.
[0034]
The blending weight ratio {(a) / (b)} of EVOH (a) and (b) is preferably 2/1 to 50/1. More preferably, it is 3/1 to 40/1, and more preferably 4/1 to 30/1. When the blending weight ratio is less than 2/1, the gas barrier property is lowered, and when it exceeds 50/1, the effect of improving the thermoformability is small.
[0035]
The ethylene- (meth) acrylic acid copolymer used in the present invention refers to a polymer having ethylene as a main component and copolymerized with acrylic acid or methacrylic acid. The present invention does not include so-called ionomers in which the carboxyl group in the copolymer is present in the form of a metal salt such as sodium or zinc. The reason why the object of the present invention is not achieved when such an ionomer is used is as shown in Comparative Examples described later, although the reason is not clear.
[0036]
The (meth) acrylic acid content in the ethylene- (meth) acrylic acid copolymer is 1 to 30% by weight, preferably 2 to 25% by weight, and more preferably 3 to 20% by weight. When the (meth) acrylic acid content is less than 1% by weight, the dispersion of the resin particles becomes poor and the thermoformability deteriorates. On the other hand, if it exceeds 30% by weight, the thermal stability becomes poor.
[0037]
Moreover, the suitable melt flow rate (MFR) (210 degreeC, the value measured under a 2160-g load) of the ethylene- (meth) acrylic acid copolymer used for this invention is 0.1-80 g / 10min suitably. Optimally, it is 0.5 to 50 g / 10 min. In the present invention, the ethylene- (meth) acrylic acid copolymer may be used by blending two or more ethylene- (meth) acrylic acid copolymers having different (meth) acrylic acid contents and / or MFR. it can.
[0038]
The EVOH content in the resin composition of the present invention is 60 to 99% by weight, preferably 70 to 97% by weight, more preferably 80 to 95% by weight. The content of the ethylene- (meth) acrylic acid copolymer is 1 to 40% by weight, preferably 3 to 30% by weight, and more preferably 5 to 20% by weight.
When the blending ratio of the ethylene- (meth) acrylic acid copolymer is less than 1% by weight, excellent thermoformability cannot be obtained, and the intersection of the side surface portion and the bottom surface portion of the thermoformed container or the corner portion is not obtained. The wall thickness becomes too thin, and the impact resistance of the molded product decreases. Further, when the blending ratio of the ethylene- (meth) acrylic acid copolymer is more than 40% by weight, the gas barrier property is remarkably lowered, and the molding shrinkage rate of the resulting thermoformed container is large, which is not suitable for actual use. .
[0039]
In the resin composition of the present invention, ethylene- (meth) acrylic acid copolymer particles are dispersed in an EVOH matrix. By having such a dispersed form, good gas barrier properties, thermoformability, and mechanical properties can be retained. When EVOH is dispersed in an ethylene- (meth) acrylic acid copolymer matrix or when both resins are continuously connected, the gas barrier property is remarkably lowered.
[0040]
The ratio of the melt flow rate (MFR) (measured at 210 ° C. under a load of 2160 g) of EVOH and ethylene- (meth) acrylic acid copolymer used in the present invention is EVOH MFR (A) and ethylene- (meta ) The ratio (A) / (B) of MFR (B) of the acrylic acid copolymer is preferably 0.1 to 5.0, more preferably 0.15 to 3.0, and most preferably 0. .2 to 2.0. By combining resins having an MFR ratio in such a range, the resin can be dispersed well and the object of the present invention can be achieved.
[0041]
The resin composition of the present invention contains hydrotalcite compounds, hindered phenols, hindered amine heat stabilizers, higher aliphatic carboxylic acids in order to enhance the effects of the present invention and improve melt stability and the like. It is preferable to add 0.01 to 1% by weight of one or more metal salts (for example, calcium stearate, magnesium stearate, etc.) to the resin composition.
[0042]
Moreover, various additives can also be mix | blended with the resin composition of this invention as needed. Examples of such additives include antioxidants, plasticizers, heat stabilizers, UV absorbers, antistatic agents, lubricants, colorants, fillers, or other polymer compounds, It can blend in the range which does not inhibit the effect of this invention. Specific examples of the additive include the following.
[0043]
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), octadecyl-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate, 4,4'-thiobis- (6- t-butylphenol) and the like.
[0044]
UV absorber: ethylene-2-cyano-3,3′-diphenyl acrylate, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-5′-methylphenyl) benzo Triazole, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-t-butyl-5′-methylphenyl) 5-chlorobenzotriazole, 2-hydroxy- 4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, and the like.
[0045]
Plasticizer: dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, phosphate ester, etc.
Antistatic agents: pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, carbowax and the like.
Lubricant: ethylene bisstearamide, butyl stearate, etc.
Colorant: Carbon black, phthalocyanine, quinacridone, indoline, azo pigment, Bengala, etc.
Filler: glass fiber, asbestos, ballastite, calcium silicate, etc.
[0046]
Also, many other polymer compounds can be blended to such an extent that the effects of the present invention are not inhibited.
[0047]
Here, the resin composition of the present invention has an average particle size of 0.3 to 1.5 μm in an EVOH matrix. , Preferably 0.3 to 1.0 μm Of ethylene- (meth) acrylic acid copolymer particles are dispersed Ru . By having such a dispersed form, good gas barrier properties, thermoformability, mechanical properties and transparency can be obtained. When the average particle diameter is larger than 1.5 μm, non-uniform dispersion in the composition is likely to occur, and problems occur during thermoforming, and gas barrier properties are likely to be reduced. Moreover, when an average particle diameter is 0.3 micrometer or less, the effect of containing a dispersed particle is not utilized for the thermoformability of a composition, and it is difficult to obtain favorable thermoformability.
[0048]
Such a dispersed form is mainly observed in the state of pellets as raw materials for films or sheets. The observation can be performed by observing the fractured surface with a scanning electron microscope, observing a thin piece with a transmission electron microscope, or the like. The contours of these photographs obtained by electron microscope observation and the like were specified by image processing, and the particle size of each particle was determined from the average value of the major axis and minor axis of the identified particle outline. The simple average of the particle diameters of the particles thus obtained was defined as the dispersed particle diameter. At this time, in order to eliminate the difference in particle diameter depending on the observation direction, the average value of the particles obtained by observation from three directions perpendicular to each other was adopted.
[0049]
In order to obtain such a dispersed form, the kneading operation in the present invention is important. As a kneading machine for obtaining a composition having a high degree of dispersion, a continuous kneading machine such as a continuous intensive mixer and a kneading type twin-screw extruder (same direction or different direction) is optimal. Batch type kneaders such as intensive mixers and pressure kneaders can also be used. Further, as another continuous kneading apparatus, one using a rotating disk having a grinding mechanism such as a stone mill, for example, a KCK kneading extruder manufactured by KCK Co., Ltd. can be used. Among those commonly used as a kneading machine, a single screw extruder provided with a kneading part (Dalmage, CTM, etc.), or a simple kneading machine such as a Brabender mixer can be given.
[0050]
Among these, the most preferable one for the purpose of the present invention is a continuous intensive mixer. Commercially available models include FCM manufactured by Farrel, CIM manufactured by Nippon Steel Works, Ltd., KCM, LCM, or ACM manufactured by Kobe Steel Corporation. In practice, it is preferable to employ an apparatus for simultaneously carrying out kneading and extrusion pelletization having a single screw extruder under these kneaders. In addition, a twin-screw kneading extruder having a kneading disk or a kneading rotor, for example, TEX manufactured by Nippon Steel, ZSK manufactured by Werner & Pfleiderer, TEM manufactured by Toshiba Machine Co., Ltd., PCM manufactured by Ikekai Tekko Co., Ltd. Etc. are also used for the purpose of kneading in the present invention.
[0051]
In using these continuous kneaders, the shape of the rotor and disk plays an important role. In particular, the gap (chip clearance) between the mixing chamber and the rotor chip or disk chip is important. If the gap is too narrow or too wide, the composition having good dispersibility of the present invention cannot be obtained. The optimum tip clearance is 1 to 5 mm.
[0052]
In order to obtain a composition having good dispersibility of the present invention, it is best to knead at a specific energy of the kneader of 0.1 kWh / kg or more, preferably 0.2 to 0.8 kWh / kg. It has been found.
The specific energy is obtained by dividing the energy (power consumption; kW) used for kneading by the kneading amount (kg) per hour, and its unit is kWh / kg. In order to obtain the composition of the present invention, it is necessary to knead at a specific energy higher than that employed in normal kneading. To obtain a specific energy of 0.1 kWh / kg or more, simply kneading machine It is not sufficient to increase the number of rotations, and it is preferable to cool the composition being kneaded with a jacket or the like to lower the temperature and increase the viscosity. It is difficult to obtain the target composition of the present invention by kneading with the viscosity lowered. Therefore, it is effective that the kneading temperature is in the range of the melting point of EVOH to the melting point + 40 ° C. at the discharge resin temperature at the outlet of the kneading section.
[0053]
The rotation speed of the rotor of the kneader is 100 to 1200 rpm, preferably 150 to 1000 rpm, and more preferably 200 to 800 rpm. The kneader chamber inner diameter (D) is 30 mm or more, preferably 50 to 400 mm. The ratio L / D to the chamber length (L) of the kneader is preferably 4-30. One kneader may be used, or two or more kneaders may be connected and used.
[0054]
The longer the kneading time, the better results can be obtained, but in terms of EVOH thermal deterioration or economic efficiency, it is 10 to 600 seconds, preferably 15 to 200 seconds, and most preferably 15 to 150 seconds. .
[0055]
The resin composition obtained as described above is useful as a multilayer structure for thermoforming.
The thermoforming as used in the present invention means that a film or sheet is heated and softened and then molded into a mold shape. As a molding method, vacuum or compressed air is used, and if necessary, a plug is further formed into a mold shape (straight method, drape method, air slip method, snapback method, plug assist method, etc.) or press molding. The method etc. are mentioned. Various molding conditions such as the molding temperature, the degree of vacuum, the pressure of compressed air, or the molding speed are appropriately set depending on the plug shape, mold shape, properties of the raw material film or sheet, and the like.
[0056]
The molding temperature is not particularly limited as long as the resin is softened enough to be molded, but the preferred temperature range varies depending on the raw material film or sheet.
For example, when a film is thermoformed, it is not heated so high that the film dissolves due to heating or the unevenness of the metal surface of the heater plate is transferred to the film. Specifically, the film temperature is 50 to 120 ° C, preferably 60 to 110 ° C, more preferably 70 to 100 ° C.
On the other hand, when a sheet having a thickness larger than that of the film is thermoformed, the sheet may be formed even at a higher temperature than that of the film, and the forming is performed in a temperature range of 130 to 180 ° C.
[0057]
The thermoformed container of the present invention is a container formed by thermoforming into a three-dimensional shape in which a recess is formed in the plane of a film or sheet. The shape of the recess is determined in accordance with the shape of the contents. In particular, as the depth of the recess is deeper and the shape of the recess is not smooth, the normal EVOH laminate is more likely to have thickness unevenness. Since it becomes extremely thin, the improvement effect by this invention is large. When the thermoformed container is formed from a film, the draw ratio (S) is preferably 0.2 or more, more preferably 0.3 or more, and even more preferably 0.4 or more. The effect of the present invention is more effectively exhibited. When the thermoformed container is formed by forming a sheet thicker than the film, the drawing ratio (S) is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 0. When the ratio is 8 or more, the effect of the present invention is more effectively exhibited.
[0058]
Here, the aperture ratio (S) refers to a value represented by the following formula (4).
S = (depth of container) / (diameter of the largest circle inscribed in the opening of the container) (4)
That is, the drawing ratio (S) is obtained by dividing the depth value of the deepest portion of the container by the diameter of the largest inscribed circle that touches the shape of the recess (opening) formed in the plane of the film or sheet. It is a thing. For example, when the shape of the recess is a circle, the diameter is the same. When the shape is an ellipse, the short diameter is used. When the shape is a rectangle, the length of the short side is the diameter of the maximum inscribed circle.
[0059]
When thermoforming thin films, it is often impossible to form deep drawing ratios or corners are torn, as compared to thermoforming thick sheets. Therefore, a film including the resin composition layer of the present invention is particularly suitable. Moreover, in the packaging container formed by thermoforming from a film, the film of the structure of this invention is suitable also from the point that transparency is also required so that the contents can be seen well.
[0060]
The multilayer film for thermoforming as used in the present invention refers to a film that includes the above-mentioned resin composition layer and is subjected to thermoforming. The multilayer structure for thermoforming has a total thickness of 50 to 300 μm, preferably 80 to 250 μm, and a resin composition layer thickness of 3 to 50 μm, preferably 5 to 40 μm. When the total thickness exceeds 300 μm, the weight of the container becomes larger than necessary, which is not preferable from the viewpoint of cost. Also, if the total thickness is less than 50 μm, the thickness of the recesses becomes too thin when molded, the mechanical strength is low and it is easy to break, and pinholes are likely to occur in the resin composition layer at that part, so the contents are sufficient Can not be protected. Further, when the thickness of the resin composition layer exceeds 50 μm, the cost increases and the moldability deteriorates, which is not preferable. Conversely, when the thickness of the resin composition layer is 3 μm or less, it is not preferable because pinholes are easily generated in the resin composition layer when it is molded.
[0061]
The dispersion state of each resin in the resin composition layer of the thermoforming multilayer film is such that the ethylene- (meth) acrylic acid copolymer particles dispersed in the EVOH matrix are drawn in a uniaxial direction parallel to the film surface. Dispersed in an elongated cylindrical shape Ru . Here, the uniaxial direction is the film extrusion direction. At this time, the average diameter of the particle cross section when cut along a plane perpendicular to the uniaxial direction is 0.2 to 1.3 μm. R More preferably, the thickness is 0.3 to 1.0 μm. When the average diameter of the particle cross section is larger than 1.3 μm, non-uniform dispersion in the composition is likely to occur, causing problems during thermoforming and lowering the gas barrier property. Moreover, when the average diameter of a particle | grain cross section is less than 0.2 micrometer, the effect of containing a dispersed particle is not utilized for the thermoformability of a composition, and favorable thermoformability is not obtained.
[0062]
The following procedure is shown as a method for measuring the average diameter of the particle cross-section in the present invention. First, a fracture surface of a sample on a plane perpendicular to the film extrusion direction is photographed by observation with a scanning electron microscope or a transmission electron microscope. Subsequently, the photograph obtained by observation with an electron microscope or the like is used to specify the outline by image processing, and the average value of the major axis and minor axis of the identified particle outline is used as the diameter of the particle. The simple average value of the diameter was determined as the average diameter of the particle cross section.
[0063]
The layer structure of the multilayer film for thermoforming of the present invention is not particularly limited, but it is preferable to have a heat seal layer from the viewpoint that the contents can be easily sealed, and to have a polyamide layer and / or a polypropylene layer. Is preferable from the viewpoint of the mechanical performance and thermoformability of the film. A thermoforming film having such a heat seal layer and a polyamide layer or both a heat seal layer and a polypropylene layer is particularly preferred. Further, an adhesive layer may be provided between these layers. Moreover, each said layer may be divided | segmented and arrange | positioned not only in one layer but in several layers in the film.
[0064]
The resin used for the heat seal layer is not particularly limited, but a resin having a melting point or softening point lower than the melting point of the EVOH resin used in the resin composition layer is preferable, and a polyolefin resin is particularly preferable. Examples of the polyolefin resin used include homopolymers such as high-density or low-density polyethylene, polypropylene, and polybutene-1, and ethylene, propylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene. Examples thereof include copolymers of α-olefins selected from the above, or copolymers of α-olefins and other copolymer components. Examples of copolymer components other than these α-olefins include vinyl compounds such as diolefin, N-vinylcarbazole, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, acrylonitrile, vinyl ether, maleic acid, acrylic acid, methacrylic acid, and ethacryl. Examples thereof include unsaturated carboxylic acids such as acid, fumaric acid and itaconic acid, esters thereof and acid anhydrides thereof, or those having a hydroxyl group or an epoxy group added thereto. For example, various copolymers such as a copolymer of a graftable monomer and a polyolefin, an ionomer resin which is a reaction product of an α-olefin / α, β-unsaturated carboxylic acid copolymer and an ionic metal compound, etc. It can also be used. Among these, low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) are preferable. These polyolefin resins can be used alone or in combination of two or more.
[0065]
When the polyamide resin layer is used, the thermoformability is improved as compared with a film composed only of the resin composition layer and the heat seal layer. The polyamide resin used for the polyamide resin layer is not particularly limited. For example, polycaproamide (nylon-6), polyundecanamide (nylon-11), polylauryllactam (nylon-12), polyhexamethylene Homopolymers such as adipamide (nylon-6,6), polyhexamethylene sebacamide (nylon-6,12), caprolactam / lauryl lactam copolymer (nylon-6 / 12), caprolactam / aminoundecanoic acid Copolymer (nylon-6 / 11), caprolactam / ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylene diammonium adipate copolymer (nylon-6 / 6,6), caprolactam / Hexamethylene diammonium adipate / hexamethylene Such copolymers ammonium sebacate copolymer (nylon-6 / 6,6 / 6,12), and the like. These polyamide resins can be used alone or in combination of two or more. A heat seal layer in addition to the polyamide resin layer is preferable from the viewpoint that the contents can be easily sealed, and a multilayer film for thermoforming having both a heat seal layer and a polyamide resin layer is preferable.
[0066]
In addition, when a polypropylene resin layer is used, the effect of improving thermoformability is not as good as that of a polyamide resin layer, but the moisture resistance of the film is improved, the mechanical performance is improved, and the resin cost is low. Compared to the case of using a resin, it has an advantageous aspect. The polypropylene resin may be syndiotactic polypropylene in addition to isotactic polypropylene, and a small amount of copolymerization may be applied. It is preferable to have a heat seal layer in addition to the polypropylene resin layer from the viewpoint that the contents can be easily sealed, and a multilayer film for thermoforming having both a heat seal layer and a polypropylene resin layer is preferable.
[0067]
Further, the haze of the thermoformable film of the present invention is preferably 10% or less. When the haze exceeds 10%, there is a problem that the contents cannot be clearly seen from the outside when the packaging material as the final product is formed. The measuring method of haze followed ASTM D1003-61.
[0068]
A specific configuration example of the multilayer film for thermoforming according to the present invention is expressed as EVOH (EVOH composition), PA (nylon), AD (adhesive), PP (polypropylene), and S (heat seal layer). AD / EVOH / AD / S, PP / AD / EVOH / AD / S, EVOH / AD / PA / AD / S, EVOH / AD / PP / AD / S, PA / AD / EVOH / AD / PA / AD / S, PP / AD / PA / AD / EVOH / AD / S, PP / AD / PA / AD / EVOH / AD / PA / AD / S, etc. are indicated as suitable. However, the layer structure of the multilayer film for thermoforming of the present invention is not limited to the above layer structure example. For example, other resin layers such as polyester and polystyrene may be added to the above configuration examples.
[0069]
The method for obtaining the multilayer film for thermoforming of the present invention is not particularly limited, but is a molding method practiced in the field of general polyolefins, for example, T-die molding, inflation molding, coextrusion molding, dry drying. Laminate molding or the like can be employed, and coextrusion molding is particularly suitable. Further, as a combination of these molding methods, a film having a structure such as (LLDPE / AD / EVOH / AD / LLDPE) is produced by coextrusion molding, and then dry lamination molding with PP or PA is performed (PP or PA / AD / A method of obtaining a film having a structure such as LLDPE / AD / EVOH / AD / S) can also be employed.
[0070]
When the obtained thermoformed container is formed by molding the above-mentioned multilayer film for thermoforming, the total thickness of the thickest part of the container (the same part as the film thickness before forming) is T μm, It is preferable that the following equation is satisfied by using the total thickness of the thin portion at t μm and the above-described drawing ratio S of the container.
5S ≦ T / t ≦ 30S (1)
50 ≦ T ≦ 300 (2)
t ≧ 20 (3)
Here, the expressions (1), (2), and (3) are more preferably each.
6S ≦ T / t ≦ 20S (1 ′)
80 ≦ T ≦ 250 (2 ′)
t ≧ 25 (3 ′)
And more preferably
7S ≦ T / t ≦ 15S (1 ″)
90 ≦ T ≦ 200 (2 ”)
t ≧ 30 (3 ″)
It is.
[0071]
When the value of T / t is less than 5S, the container is shaped so that it does not require the configuration of the present invention, and the container is easily formed. When the value of T / t exceeds 30S, the container is Therefore, the container is not a preferable shape. Further, when the total thickness (T) in the thickest part exceeds 300 μm, the weight of the container becomes unnecessarily large, which is not preferable from the viewpoint of cost. Further, when the total thickness (T) in the thickest portion is less than 50 μm, the thickness of the concave portion becomes too thin at the time of molding, the mechanical strength is low, and the resin composition layer in that portion is easily broken. As a result, pinholes are easily generated, and the contents cannot be sufficiently protected. Moreover, it is not preferable for the same reason that the total thickness (t) in the thinnest portion is less than 20 μm.
[0072]
In the thermoforming container comprising the above-mentioned multilayer film for thermoforming, the dispersion form of each resin in the resin composition layer in the thinnest part is ethylene- (meta) dispersed in the EVOH matrix. The acrylic acid copolymer particles are dispersed in a thin plate-like shape stretched in a two-dimensional direction parallel to the film surface, and the average thickness of the cross section of the particles when cut in a plane perpendicular to the film surface is 0. It is desirable that it is 05-1.0 micrometer, More preferably, it is 0.06-0.5 micrometer. When the average thickness is 0.05 μm or less, or exceeds 1.0 μm, tearing may occur in the thermoforming process.
[0073]
The average thickness of the particle cross section is measured as follows. First, the thickness is measured over the entire thermoformed container, and the thinnest part is specified. The thickness is observed by scanning electron microscope observation of the fracture surface of the sample on the vertical plane of the film or transmission electron microscope observation of the thin piece. Subsequently, the outline of the photograph obtained by observation with an electron microscope or the like was specified by image processing, and a simple average value of the thickness of the specified particle outline was defined as the average thickness.
[0074]
Various thermoformed containers formed from the film as described above are used in various applications. Among these, the superiority of using the resin composition of the present invention that is excellent in gas barrier properties is greatly exhibited when used as various packaging containers. It is particularly suitable as a packaging container such as food, pharmaceuticals, agricultural chemicals, etc. whose quality is likely to deteriorate due to the presence of oxygen, such as a container for meat.
[0075]
In addition, the use form of the resin composition of the present invention that is excellent in gas barrier properties, thermoformability, mechanical properties and transparency is not limited to the above-mentioned thermoform film, and is a thermoform sheet having a larger thickness than the film. In some cases, a sufficient effect can be obtained even in a multilayer structure including the.
[0076]
The laminated structure of such a multilayer structure is not particularly limited. The resin used by laminating with the resin composition layer includes polyolefin resin, polystyrene resin, polyamide resin, saturated polyester resin (polyethylene terephthalate, etc.), polycarbonate resin, polyvinyl chloride resin, and polyvinylidene chloride. Examples thereof include thermoplastic resins such as resins, which can be appropriately selected depending on the application. This is because, by laminating with such a resin, gas barrier properties under high humidity, strength, and the like can be improved as compared with the case of using a single resin composition layer.
Preferable resins include polypropylene (PP), polystyrene (PS), polyester (PES) and the like, and examples of preferred layer structures include PP / AD / EVOH / AD / PP, PS / AD / EVOH / AD. / PS, PES / AD / EVOH / AD / PES, etc. are exemplified, but not limited thereto.
In addition, a recovery composition (regrind) layer containing EVOH, an ethylene- (meth) acrylic acid copolymer, an adhesive resin, or the like can also be used as the thermoplastic resin.
[0077]
The layer structure of the multilayer structure for thermoforming of the present invention is not particularly limited except that it has the above-mentioned resin composition layer and a layer made of a thermoplastic resin, but it has adhesiveness to the inner and outer layers of the resin composition layer. A structure having a layer made of a thermoplastic resin, especially a polyolefin, through a resin layer is particularly preferable.
This is because by covering both sides of the resin composition layer with polyolefin, it is possible to prevent a decrease in gas barrier properties due to moisture absorption of the resin composition layer, and it is possible to ensure good adhesion between both layers by the adhesive resin layer.
[0078]
The resin used for the adhesive resin layer is not particularly limited, but polyurethane-based, polyester-based one-component or two-component curable adhesive, unsaturated carboxylic acid or anhydride thereof (maleic anhydride, etc.) ) Are copolymerized or graft-modified into olefin polymers or copolymers (carboxylic acid-modified polyolefin resin). By providing such an adhesive resin layer, a thermoformed container excellent in interlayer adhesion can be obtained.
[0079]
Among these, it is more preferable that the adhesive resin is a carboxylic acid-modified polyolefin resin from the viewpoint of adhesiveness with a resin composition layer or copolymerized polypropylene containing EVOH, or compatibility during scrap recovery. Examples of such carboxylic acid-modified polyethylene resins include polyethylene {low density polyethylene (LDPE), linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE)}, polypropylene, copolymer polypropylene, ethylene-vinyl acetate. Examples thereof include a copolymer, an ethylene- (meth) acrylic acid ester (methyl ester or ethyl ester) copolymer, etc., which have been modified with a carboxylic acid.
[0080]
The method for obtaining the multilayer structure for thermoforming according to the present invention is not particularly limited, but a forming method practiced in the field of general polyolefin, for example, T-die molding, inflation molding, coextrusion molding, Dry laminate molding or the like can be employed, and coextrusion molding is particularly suitable.
[0081]
The molding temperature at the time of thermoforming the obtained multilayer structure is not particularly limited as long as the resin is softened enough to be molded, but the suitable temperature range depends on the raw material sheet. Different.
For example, when thermoforming a sheet, it is not so high that the sheet melts due to heating or the unevenness of the metal surface of the heater plate is transferred to the film, while it is so low that shaping is not sufficient. Specifically, the sheet temperature is 130 to 180 ° C, preferably 135 to 160 ° C, more preferably 135 to 155 ° C.
[0082]
The preferred shape of the molded container when thermoforming a multilayer structure as described above, particularly a sheet-like multilayer structure, or when thermoforming a multilayer structure having a layer made of copolymerized polypropylene or polystyrene is as follows. It is. That is, the total layer thickness in the thickest part (the same part as the multilayer structure thickness before molding) of the obtained thermoformed container is Tμm, the total layer thickness in the thinnest part is tμm, It is preferable that the following expression is satisfied using the aperture ratio S.
S ≦ T / t ≦ 20S (5)
300 <T ≦ 3000 (6)
t ≧ 100 (7)
Here, the expressions (5), (6), and (7) are more preferably respectively.
1.5S ≦ T / t ≦ 15S (5 ′)
500 ≦ T ≦ 2000 (6 ′)
t ≧ 200 (7 ′)
And more preferably
2S ≦ T / t ≦ 10S (5 ″)
800 ≦ T ≦ 1500 (6 ″)
t ≧ 300 (7 ″)
It is.
[0083]
When the value of T / t is less than S, the container is shaped so as not to require the configuration of the present invention, and is easily formed. When the value of T / t exceeds 20S, the container Therefore, the container is not a preferable shape. Further, when the total thickness (T) in the thickest part exceeds 3000 μm, the weight of the container becomes unnecessarily large, which is not preferable from the viewpoint of cost and is difficult to mold. If the total thickness (T) in the thickest part is less than 300 μm, the thickness of the molded container becomes too thin and the rigidity is insufficient. In addition, it is not preferable for the same reason that the total thickness (t) in the thinnest portion is less than 100 μm.
[0084]
Various thermoformed containers formed from the sheet as described above are used for various applications. Among these, the superiority of using the resin composition of the present invention that is excellent in gas barrier properties is greatly exhibited when used as various packaging containers. Particularly suitable for packaging containers such as foods, pharmaceuticals, agricultural chemicals and the like whose quality is likely to deteriorate due to the presence of oxygen, such as cups for pudding, jelly, miso and the like.
[0085]
【Example】
The following examples further illustrate the present invention.
Examples of the present invention include examples in which a multilayer film is thermoformed (Examples 1 to 25, Comparative Examples 1 to 11) and examples in which a multilayer sheet is thermoformed (Examples 26 to 28, Comparative Examples 12 and 13). Two examples were carried out. Each will be described in turn below.
[0086]
First, an example in which a container is prepared by thermoforming a multilayer film will be described.
Evaluation of the resin composition pellets, thermoforming films, and thermoforming containers obtained in the examples was performed according to the following methods.
[0087]
・ Average particle size of dispersed particles in resin composition pellets
The pellet was broken at a plane perpendicular to one direction of the resin flow direction and two directions perpendicular thereto, and the vicinity of the center of the fracture surface was observed with a scanning electron microscope, and a photograph was taken at a magnification of 1000 to 10000 times. When observing the dispersed particles, if it is difficult to observe due to the type of compounded resin, the pellet fracture surface is smoothed with a microtome as necessary, or the dispersed particles are dissolved with xylene, etc. The method of observing was adopted. Next, the contour of the obtained dispersed particles in the photograph is specified using an image measurement tool system ASPECT manufactured by Keio Electronics Co., Ltd., and the particle size of each particle is determined from the average value of the major axis and minor axis of the identified particle outline. Asked. Dispersed particles in the same area range photographed at the same magnification from three directions were measured, and at that time, the number of dispersed particles measured in each direction was 30 or more. The average value of all the particle sizes thus obtained was defined as the average particle size.
[0088]
・ Average diameter of particle cross section of dispersed particles in multilayer film for thermoforming
The fracture surface of the sample on the plane perpendicular to the film extrusion direction was observed with a scanning electron microscope, and photographs were taken at a magnification of 3000 to 20000 times. The profile of the dispersed particles in the obtained photograph is identified using the image measurement tool system ASPECT manufactured by KIO Electronics Co., Ltd., and the average value of the major axis and minor axis of the identified particle outline is the particle diameter, The average value of the diameter values of the obtained particles was determined as the average diameter of the particle cross section. The number of dispersed particles to be measured was set to 30 or more. In addition, for the fracture surface of the sample, a microtome or dissolution technique was used as necessary in the same manner as in the previous pellet.
・ Haze
A part of the thermoformed film was cut out and coated with silicon oil, and the haze value was measured according to ASTM D1003-61 using HR-100 manufactured by Murakami Color Research Laboratory.
[0089]
-Corner thickness (corner thickness) measurement
The four corners of the thermoformed container were measured with a thickness meter, and the thickness of the thinnest part of each corner was measured.
[0090]
・ Average thickness of dispersed particles in the thinnest part of a thermoforming container
Cut out the thinnest vertical film of the four corners above, embed it in an epoxy resin, create an ultrathin section with a microtome, and then stain with ruthenium oxide vapor at room temperature for 1 day. And observed with a transmission electron microscope, and photographed with a magnification of 10,000 to 30,000 times. The outline of the obtained photograph was specified using an image measurement tool system ASPECT manufactured by Keio Electronics Co., Ltd., and the average thickness of the specified particle outline was defined as the average thickness. Moreover, the thing with small average thickness was used for the image processing using the enlarged copy figure by a precision copying machine as needed.
[0091]
・ Mold shrinkage
A strip-shaped (30 mm wide) test piece perpendicular to the mold vertical side and passing through the center of the bottom was cut out from the thermoformed container, and the molding shrinkage rate was determined from the length (mm) of the cut out test piece with respect to the mold shape.
Mold shrinkage [%] = [{(50 × 2 + 110) − (length of test piece)} / (50 × 2 + 110)] × 100
A large molding shrinkage indicates that the moldability for the mold shape is poor.
・ Molded product appearance
The determination was made visually by paying attention to streaks, wrinkles, unevenness, etc. in a thermoformed container. (Good): A>B>C> D: (Evil)
[0092]
・ Oxygen transmission rate
After the bottom of the thermoformed container is cut out and the humidity is adjusted to 20 ° C.-85% RH, the oxygen permeation amount (ml) of the laminated film at the bottom is measured with a barrier measuring device (OX-TRAN-10 / 50A, manufactured by Modern Control). / M ² · Day · atm) was measured.
[0093]
・ Drop test
500 cc of water was put into a molded product (formed with a rectangular parallelepiped mold having a length of 130 mm, a width of 110 mm, and a depth of 50 mm), and a low density polyethylene film (thickness: 100 μm) was heat-welded on the upper surface. The container was dropped on the concrete, and the height at which the container was destroyed (water inside the container leaked) was determined. The fracture height was determined by using the test result of n = 30 and using the calculation method shown in the JIS test method (“8. Calculation” part of K7211) to determine the 50% fracture height.
[0094]
Example 1
EVOH containing sodium acetate at 65 ppm in terms of sodium element weight and phosphorus compound in the form of phosphate as 100 ppm by weight per phosphorus atom {ethylene content 32 mol%, saponification degree 99.6%, MFR = 3.1 g / 10 minutes (210 ° C., 2160 g load)} 90% by weight, ethylene-methacrylic acid copolymer (hereinafter abbreviated as EMAA) {methacrylic acid (MAA) content: 9% by weight, Mitsui DuPont Chemical “Nucrel 0903HC, MFR = 5.7 g / 10 min (210 ° C., 2160 g load)} 10% by weight, and then 30 mmφ twin screw extruder with a kneading disk (Nippon Steel Works TEX30: L / D = 30) Set the cylinder temperature to 190 ° C at the bottom of the feed and 210 ° C near the kneading section and nozzle. Rotational speed of the over the 610Rpm, a motor rotation speed 250rpm feeders were melt-kneaded and pelletized. Resin pressure inside the cylinder at an extrusion amount of this time is 1 hour per 20kg is 20kg / cm ² Met. The specific energy at this time was 0.6 kWh / kg.
[0095]
The obtained pellet is used as a resin composition layer, and linear low density polyethylene (LLDPE) {MFR = 2.1 g / 10 min (210 ° C., 2160 g load), Mitsui Petrochemical's “Ultzex 3520L”} is heat sealed. As a layer, maleic anhydride-modified polyethylene {MFR = 3.3 g / 10 min (210 ° C., 2160 g load), Mitsui Petrochemical's “Admer SF600”} as an adhesive (AD) layer, and nylon 6 (PA-6) ) {MFR = 7.2 g / 10 min (230 ° C, 2160 g load), "UBE Nylon 1022B" manufactured by Ube Industries, Ltd.} is used as a polyamide layer, 3 types and 5 layers in a co-extruder equipped with a T-die A film for thermoforming having an overall thickness of 130 μm was obtained (PA-6 / AD / resin composition layer / AD / LLDPE = 20 μ / 5 μ / 20 μ / 5 μ / 80 μ).
[0096]
The film for thermoforming thus obtained was heated for 1.5 seconds at a heater plate temperature of 100 ° C. with a thermoforming machine (R530 manufactured by Mulchback Co., Ltd.) to a film temperature of about 85 ° C. 130 mm, horizontal: 110 mm, depth: 50 mm rectangular parallelepiped shape, drawing ratio S = 0.45) and compressed air (atmospheric pressure 5 kgf / cm) ² ) Was used to obtain a thermoformed container. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0097]
Comparative Example 1
In Example 1, a sample was prepared and tested in the same manner as in Example 1 except that the same EVOH resin as that used in Example 1 was used alone instead of the resin composition layer. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0098]
Examples 2 and 3 and Comparative Example 2
The same EVOH and EMAA as used in Example 1 were used, and the mixing ratio was EVOH 95% by weight, EMAA 5% by weight (Example 2), EVOH 80% by weight, EMAA 20% by weight (Example 3), EVOH 50% by weight, EMAA50. A sample was prepared and tested in the same manner as in Example 1 except that the weight was changed to% by weight (Comparative Example 2). The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0099]
Examples 4 and 5
EVOH used in Example 1 has different ethylene contents EVOH {ethylene content 27 mol%, saponification degree 99.6%, MFR = 3.9 g / 10 min (210 ° C., 2160 g load)} (Example 4), {Ethylene content 44 mol%, saponification degree 99.7%, MFR = 3.5 g / 10 min (210 ° C., 2160 g load)} (Example 5) Fabricated and tested. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0100]
Examples 6-9
A sample was prepared and tested in the same manner as in Example 1 except that two types of EVOH blended in the proportions shown below were used instead of 90% by weight of EVOH used in Example 1. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
Example 6;
85 parts by weight of EVOH having an ethylene content of 32 mol%, a saponification degree of 99.6%, and MFR = 3.1 g / 10 min (210 ° C., 2160 g load)
5 parts by weight of EVOH having an ethylene content of 51 mol%, a saponification degree of 96%, MFR = 15.1 g / 10 min (210 ° C., 2160 g load)
Example 7;
85 parts by weight of EVOH having an ethylene content of 38 mol%, a saponification degree of 99.7%, MFR = 3.8 g / 10 min (210 ° C., 2160 g load)
5 parts by weight of EVOH having an ethylene content of 51 mol%, a saponification degree of 96%, MFR = 15.1 g / 10 min (210 ° C., 2160 g load)
Example 8;
85 parts by weight of EVOH having an ethylene content of 38 mol%, a saponification degree of 99.7%, MFR = 3.8 g / 10 min (210 ° C., 2160 g load)
5 parts by weight of EVOH having an ethylene content of 44 mol%, a saponification degree of 99.7%, MFR = 3.5 g / 10 min (210 ° C., 2160 g load)
Example 9;
50 parts by weight of EVOH having an ethylene content of 32 mol%, a saponification degree of 99.6%, and MFR = 3.1 g / 10 min (210 ° C., 2160 g load)
40 parts by weight of EVOH having an ethylene content of 51 mol%, a saponification degree of 96%, MFR = 15.1 g / 10 min (210 ° C., 2160 g load)
[0101]
Examples 10-12, Comparative Examples 3-7
Instead of EMAA {methacrylic acid content: 9% by weight, Mitsui DuPont Chemical "Nucrel 0903HC, MFR = 5.7 g / 10 min (210 ° C., 2160 g load)} used in Example 1, the following resin was used. A sample was prepared and tested in the same manner as in Example 1. Table 1 and Table 2 summarize the evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container.
Example 10: EMAA {Methacrylic acid content: 4 wt%, Mitsui DuPont Chemical "Nucleel AN4214C", MFR = 12.2 g / 10 min (210 ° C., 2160 g load)}
Example 11: EMAA {Methacrylic acid content; 12 wt%, Mitsui DuPont Chemical "Nucrel 1207C", MFR = 13.4 g / 10 min (210 ° C, 2160 g load)}
Example 12; ethylene-acrylic acid copolymer (hereinafter abbreviated as EAA) {acrylic acid (AA) content: 9.0 wt%, Dow Chemical "Primacol 1430, MFR = 8.7 g / 10 min (210 ℃, 2160g load)}
Comparative Example 3; Ethylene-methyl methacrylate copolymer {Methyl methacrylic acid (MMA) content: 18% by weight, Sumitomo Chemical "Aclift WH303, MFR = 12.1 g / 10 min (210 ° C, 2160 g load)}
Comparative Example 4; Maleic anhydride-modified polyethylene {MFR = 3.6 g / 10 min (210 ° C., 2160 g load), “Admer NF500” manufactured by Mitsui Petrochemical Co., Ltd.}
Comparative Example 5: Ionomer {Mitsui DuPont Chemical "High Milan 1652, MFR = 7.6 g / 10 min (210 ° C, 2160 g load)}
Comparative Example 6; LDPE {Millason B324, MFR = 3.4 g / 10 min (210 ° C., 2160 g load)} manufactured by Mitsui Petrochemical Co., Ltd.}
Comparative Example 7; Nylon {Nylon 6 (PA-6) {MFR = 7.2 g / 10 min (230 ° C., 2160 g load), manufactured by Ube Industries “UBE Nylon 1022B”}}
[0102]
Examples 13-16
A sample was prepared and tested in the same manner as in Example 1 except that the following EVOH and ethylene- (meth) acrylic acid copolymer were used in combination. At this time, the ratio MFR (A) / MFR (B) was adjusted by changing the MFR of EVOH to be used and the ethylene- (meth) acrylic acid copolymer. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
Example 13
EVOH {ethylene content 32 mol%, saponification degree 99.6%, MFR = 1.2 g / 10 min (210 ° C., 2160 g load)}, EMAA {methacrylic acid content: 9 wt%, Mitsui DuPont Chemical “Nucrel NC0908HG ”, MFR = 15.3 g / 10 min (210 ° C., 2160 g load)}
Example 14
EVOH {ethylene content 32 mol%, saponification degree 99.6%, MFR = 33.0 g / 10 min (210 ° C, 2160 g load)}, EMAA {methacrylic acid content: 9 wt%, Mitsui DuPont Chemical "Nucleel 0903HC , MFR = 5.7 g / 10 min (210 ° C., 2160 g load)}
Example 15
EVOH {ethylene content 32 mol%, saponification degree 99.6%, MFR = 1.2 g / 10 min (210 ° C, 2160 g load)}, EAA {acrylic acid content: 9 wt%, Dow Chemical "Primacol 3440 ”, MFR = 18.0 g / 10 min (210 ° C., 2160 g load)}
Example 16
EVOH {ethylene content 32 mol%, saponification degree 99.6%, MFR = 33.0 g / 10 min (210 ° C., 2160 g load)}, EAA {acrylic acid content: 9 wt%, Dow Chemical “Primacol 1420” ”, MFR = 5.6 g / 10 min (210 ° C., 2160 g load)}
[0103]
Example 17
In Example 1, instead of using a twin screw extruder, EVOH and EMAA are melt kneaded using a single screw extruder (Placo GT-40-A: L / D = 26, using a full flight type screw). The temperature is set to 190 ° C. at the lower part of the feed, and 210 ° C. near the kneading part and the nozzle. The rotation speed of the rotor of the extruder is 1500 rpm, and the mixture is melt-kneaded and pelletized. Resin pressure inside the cylinder is 8kg / cm ² Thus, a sample was prepared and tested in the same manner as in Example 1 except that the specific energy at this time was 0.1 kWh / Kg. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0104]
Example 18
A sample was prepared and tested in the same manner as in Example 17 except that the screw was changed from a full flight type screw to a screw having a kneading part at the tip. At this time, the resin pressure inside the cylinder is 10 kg / cm. ² The specific energy at this time was 0.15 kWh / Kg. The evaluation results of the obtained resin composition pellets, thermoforming film, and thermoforming container are summarized in Tables 1 and 2.
[0105]
Examples 19 to 21, Comparative Examples 8 and 9
In Example 1, the layer constitution at the time of producing the multilayer constitution film was changed to (LLDPE / AD / resin composition layer / AD / PP = 80 μ / 5 μ / 20 μ / 5 μ / 30 μ), and the following resins were respectively used as the resin composition layers. Alternatively, a sample was prepared and tested in the same manner as in Example 1 except that the resin composition was used. The evaluation results of the obtained thermoforming film and thermoforming container are summarized in Tables 3 and 4.
Example 19: same resin composition as in Example 1
Example 20; same resin composition as in Example 6
Example 21; same resin composition as in Example 12
Comparative Example 8; same resin composition as Comparative Example 3
Comparative Example 9: EVOH same as Comparative Example 1
[0106]
Examples 22 and 23, Comparative Example 10
In Example 1, the layer constitution at the time of producing the multilayer constitution film was changed to (LLDPE / AD / resin composition layer = 80 μ / 5 μ / 20 μ), and the following resin or resin composition was used as the resin composition layer, respectively. In the same manner as in Example 1, a sample was prepared and tested. The evaluation results of the obtained thermoforming film and thermoforming container are summarized in Tables 3 and 4.
Example 22; same resin composition as in Example 1
Example 23: same resin composition as in Example 6
Comparative Example 10; EVOH same as Comparative Example 1
[0107]
Examples 24 and 25, Comparative Example 11
In Example 1, the layer constitution at the time of producing the multilayer constitution film was changed to (LLDPE / AD / resin composition layer / AD / LLDPE = 40 μ / 5 μ / 20 μ / 5 μ / 40 μ), and the following resins were respectively used as resin composition layers. Alternatively, a sample was prepared and tested in the same manner as in Example 1 except that the resin composition was used. The evaluation results of the obtained thermoforming film and thermoforming container are summarized in Tables 3 and 4.
Example 24; same resin composition as in Example 1
Example 25; same resin composition as in Example 6
Comparative Example 11; EVOH same as Comparative Example 1
[0108]
Next, an example in which a container is prepared by thermoforming a multilayer sheet will be described.
Evaluation of the thermoforming multilayer structure and thermoforming container obtained in the examples was performed according to the following method.
[0109]
・ Average diameter of cross section of dispersed particles in multilayer structure for thermoforming
The fracture surface of the sample on the surface perpendicular to the extrusion direction of the multilayer structure was observed with a scanning electron microscope, and photographs were taken at a magnification of 3000 to 20000 times. When observing the dispersed particles, if it is difficult to observe due to the type of compounded resin, the pellet fracture surface is smoothed with a microtome as necessary, or the dispersed particles are dissolved with xylene, etc. The method of observing was adopted. The profile of the dispersed particles in the obtained photograph is identified using the image measurement tool system ASPECT manufactured by KIO Electronics Co., Ltd., and the average value of the major axis and minor axis of the identified particle outline is the particle diameter, The average value of the diameter values of the obtained particles was determined as the average diameter of the particle cross section. The number of dispersed particles to be measured was set to 30 or more.
[0110]
・ Haze
A part of the multilayer structure for thermoforming was cut out, coated with silicon oil, and the haze value was measured according to ASTM D1003-61 using HR-100 manufactured by Murakami Color Research Laboratory.
・ Oxygen transmission rate
A part of the multilayer structure for thermoforming was cut out and the humidity was adjusted to 20 ° C. to 85% RH, and then the oxygen transmission rate was measured with a barrier measuring device (OX-TRAN-10 / 50A, manufactured by Modern Control). . The amount of oxygen permeation here is the amount of oxygen permeation measured in a multilayer structure (unit: ml / m ² · Day · atm) converted to oxygen permeation amount per 20 μm of gas barrier resin layer (ml · 20 μm / m ² (Day / atm). Note that the oxygen permeation amount of the inner and outer layers and the adhesive resin layer was much larger than that of the gas barrier resin layer, and was calculated after being ignored.
[0111]
-Thermoformed container appearance
The appearance of cups molded at a sheet heating temperature of 150 ° C (vertical: 130 mm, horizontal: 110 mm, depth: molded with a rectangular parallelepiped mold of 50 mm) was visually observed, and the formability and the occurrence of cracks And the occurrence of wave pattern was evaluated. The evaluation criteria for the formability here is to visually determine whether the corners (intersection lines of the side surface and the bottom surface) are accurately formed, and to evaluate all samples in four stages (good: A>B>C> D: Evil). As for the occurrence of cracks, the state of occurrence of a crack of about 2 mm in length occurring near the bottom of the side surface is visually judged, and all evaluation samples are classified into four stages according to the conspicuousness of the occurrence state (good: A>B>C> D: Evil). As for the occurrence of the wave pattern, the wavy appearance unevenness generated mainly on the side surface of the cup is visually judged, and all evaluation samples are classified into four stages according to the conspicuousness (good: A>B>C> D: bad). Classified.
The thickness of the thinnest part was determined by measuring the thinnest part in the vicinity of the intersection of the bottom and side surfaces of the molded product.
[0112]
・ Drop test
200 cc of water was put into the molded cup, and the same cup was turned down and heat-welded. The container was dropped on the concrete, and the height at which the container was destroyed (water inside the container leaked) was determined. The fracture height was determined as a 50% fracture height using the calculation method shown in the JIS test method (“8. Calculation” part of K7211) using the test result of n = 30.
[0113]
Example 26
The pellet obtained in Example 1 was used as the resin composition layer, and homopolypropylene {Grand polymer “J103”, MFR = 3.0 g / 10 min (230 ° C., 2160 g load), Vicat softening point 155 ° C.} was used as the inner and outer layers. , A maleic anhydride modified polypropylene {"Admer QF500" manufactured by Mitsui Petrochemical Co., Ltd., MFR = 5.3 g / 10 min (230 ° C., 2160 g load)} is used as an adhesive (AD) layer, and a T-type die is provided. A thermoforming sheet having a total thickness of 1000 μm was obtained with three types and five layers (coPP / AD / resin composition layer / AD / coPP = 400 μ / 50 μ / 100 μ / 50 μ / 400 μ) using a co-extruder. The cross-sectional diameter of the dispersed particles in the composition layer of the obtained sheet, the haze value of the sheet, and the oxygen permeability of the sheet were measured.
[0114]
The sheet thus obtained was thermoformed into a cup shape (die shape 70φ × 70 mm, drawing ratio S = 1.0) by using a thermoforming machine (manufactured by Asano Seisakusho) (pressure air: 5 kg / cm). ² , Plug: 45φ × 65 mm, syntax foam, plug temperature: 150 ° C., mold temperature: 70 ° C. was used). The appearance of the molded cup was visually evaluated.
The thickness of the thinnest part was determined by measuring the thinnest part in the vicinity of the intersection between the bottom and side of the molded product. Further, water was put into the obtained container and subjected to a drop test.
The evaluation results of these thermoforming sheets and thermoforming containers are summarized in Table 5.
[0115]
Examples 27 and 28, Comparative Example 12
A sample was prepared and tested in the same manner as in Example 26 except that the following resin compositions were used instead of the resin composition used in Example 26. The evaluation results of the obtained sheet and thermoformed container are summarized in Table 5.
Example 27; Resin composition used in Example 12
Example 28; resin composition used in Example 6
Comparative Example 12: Resin composition used in Comparative Example 3
Comparative Example 13: EVOH resin used in Comparative Example 1 alone
[0116]
[Table 1]

[0117]
[Table 2]

[0118]
[Table 3]

[0119]
[Table 4]

[0120]
[Table 5]

[0121]
【The invention's effect】
The thermoforming film or sheet of the present invention has a good thermoforming property, and can provide a thermoforming container excellent in gas barrier properties and mechanical properties. Such a thermoformed container has an excellent appearance as various packaging containers because it has a good appearance, excellent mechanical performance, and excellent gas barrier properties.

Claims (13)

Ethylene- (meth) acrylic acid copolymer having an ethylene content of 20 to 60 mol%, an ethylene-vinyl alcohol copolymer having a saponification degree of 90% or more and 60 to 99% by weight and a (meth) acrylic acid content of 1 to 30% by weight 40 to 1% by weight, comprising a resin composition layer in which ethylene- (meth) acrylic acid copolymer particles are dispersed in an ethylene-vinyl alcohol copolymer matrix, and the total thickness is 50 to 300 μm It is a multilayer film for thermoforming having a resin composition layer thickness of 3 to 50 μm . In the resin composition layer, a circle in which ethylene- (meth) acrylic acid copolymer particles are stretched in a uniaxial direction parallel to the film surface A multilayer film for thermoforming, which is dispersed in a columnar shape and has an average particle cross-sectional diameter of 0.2 to 1.3 μm when cut along a plane perpendicular to the uniaxial direction.   The ratio (A) / (B) of the MFR (A) of the ethylene-vinyl alcohol copolymer and the MFR (B) of the ethylene- (meth) acrylic acid copolymer is 0.1 to 5.0. The multilayer film for thermoforming as described. The multilayer film for thermoforming according to claim 1 or 2 , further comprising a heat seal layer. The multilayer film for thermoforming according to claim 3 , further comprising a polypropylene resin layer and / or a polyamide resin layer in addition to the heat seal layer. The multilayer film for thermoforming according to any one of claims 1 to 4 , wherein the haze is 10% or less. A thermoformed container formed by thermoforming the multilayer film according to any one of claims 1 to 5 . When the total layer thickness in the thickest part of the container is T μm, the total layer thickness in the thinnest part is t μm, and the drawing ratio of the container is S, the following formulas (1) to (3) are satisfied. The thermoformed container according to claim 6 .
5S ≦ T / t ≦ 30S (1)
50 ≦ T ≦ 300 (2)
t ≧ 20 (3)
However, the squeezing ratio S of the container is a value represented by the following formula (4).
S = (depth of container) / (diameter of the largest circle inscribed in the opening of the container) (4) In the thinnest part of the container, ethylene- (meth) acrylic acid copolymer particles dispersed in an ethylene-vinyl alcohol copolymer matrix are stretched in a two-dimensional direction parallel to the film surface. The thermoformed container according to claim 6 or 7 , wherein the particles are dispersed in a thin plate shape and have an average thickness of a particle cross section of 0.05 to 1.0 µm when cut along a plane perpendicular to the film surface. Ethylene- (meth) acrylic acid copolymer having an ethylene content of 20 to 60 mol%, an ethylene-vinyl alcohol copolymer having a saponification degree of 90% or more and 60 to 99% by weight and a (meth) acrylic acid content of 1 to 30% by weight A multilayer structure for thermoforming comprising 40 to 1% by weight and having a resin composition layer in which ethylene- (meth) acrylic acid copolymer particles are dispersed in an ethylene-vinyl alcohol copolymer matrix ; Particle cross section when ethylene- (meth) acrylic acid copolymer particles are dispersed in a cylindrical shape extended in a uniaxial direction parallel to the multilayer structure surface, and cut along a plane perpendicular to the uniaxial direction A multilayer structure for thermoforming having an average diameter of 0.2 to 1.3 μm. A thermoformed container formed by thermoforming the multilayer structure according to claim 9 . When the total layer thickness in the thickest part of the container is T μm, the total layer thickness in the thinnest part is t μm, and the drawing ratio of the container is S, the following formulas (5) to (7) are satisfied. The thermoformed container according to claim 10 .
S ≦ T / t ≦ 20S (5)
300 <T ≦ 3000 (6)
t ≧ 100 (7)
However, the squeezing ratio S of the container is a value represented by the following formula (4).
S = (depth of container) / (diameter of the largest circle inscribed in the opening of the container) (4) Ethylene- (meth) acrylic acid copolymer having an ethylene content of 20 to 60 mol%, an ethylene-vinyl alcohol copolymer having a saponification degree of 90% or more and 60 to 99% by weight and a (meth) acrylic acid content of 1 to 30% by weight A resin composition comprising 40 to 1% by weight, wherein ethylene- (meth) acrylic acid copolymer particles having an average particle size of 0.3 to 1.5 μm are dispersed in an ethylene-vinyl alcohol copolymer matrix. . A resin composition for thermoforming comprising the resin composition according to claim 12 .