JP5686531B2 - Plastic film and molded container using the same - Google Patents

Description

  The present invention relates to a plastic sheet for a molded container that contains food, liquid food, and the like, and the molded container.

  More specifically, it absorbs dissolved oxygen in the contained material, has excellent sorption and adsorption performance of volatile by-products generated in the oxygen absorption reaction, and has a barrier property against oxygen entering from the outside, In addition, the present invention relates to a plastic sheet for a molded container that accommodates food, liquid food, and the like having heat resistance that can cope with high-pressure steam sterilization at 121 ° C. or higher and microwave heating, and the molded container.

  As a container for storing food, liquid food, and the like, conventionally, a molded container made of a composite material in which a metal foil and a resin are devised in Patent Document 1 or the like is used. While the container is excellent in heat resistance and hermetically sealed storage, the microwaves are concentrated on the metal part in the case of damage caused by the residue at the time of opening or microwave heating such as a microwave oven. It was regarded as a problem that an internal spark would occur.

  Further, since the dry lamination method using an organic solvent as a medium is used for the lamination in the prior application technique of Patent Document 1, the amount of eluate that cannot be ignored even though it is within the safety and health standards set for food containers and packaging. Can be.

  Furthermore, dissolution, mixing, suspending, stirring, cooking, pumping, etc. in the production and filling process of the contents involve air and remain in the contents at a concentration of 3 to 50 ppm as dissolved oxygen. When the contents contain turmeric, polyphenol, tannin, catechin, anthocyanin, carotenoid, flavonoid, rutin, etc. (curry, green tea, red wine, chestnut, straw, banana, buckwheat, etc.), the strong oxidation of dissolved oxygen It is known that discoloration, alteration, and quality degradation called browning occur.

  The reaction rate of oxidation is exponentially accelerated with temperature, that is, oxidative degradation is dramatically accelerated in the autoclave sterilization process. In order to prevent this, a method has been devised and implemented in which a container is filled with an inert gas, the container is filled while being replaced with an inert gas, or an antioxidant is added to the container. Yes. Filling and replacing with an inert gas is useful for suppressing oxidative degradation, but it cannot completely remove and replace dissolved oxygen.

  Antioxidants added to the contents include vitamin C (ascorbic acid), vitamin E (tocopherol), BHT (dibutylhydroxytoluene), BHA (butylhydroxyanisole), sodium erythorbate, sodium sulfite, sulfur dioxide, Coffee bean extract (chlorogenic acid), green tea extract (catechin), rosemary extract, etc. are mentioned, among them sulfite ion substances are frequently used due to high antioxidant effect, but it causes anaphylactic shock, etc. Ingestion into the human body was undesirable.

  From the above background, various inventions have been proposed in which the container itself is provided with an oxygen barrier property and an oxygen absorbing function.

  For example, in Patent Document 2, “polyamide or polyester or polyolefin layer”, “bonding layer”, “core layer of ethylene-vinyl alcohol copolymer”, “bonding layer”, “solution contact layer of polyolefin, in order from the outside. A five-layer structure in which "" is formed by a cast coextrusion method has been proposed.

  Further, in Patent Document 3, at least “oxygen barrier layer made of ethylene-vinyl alcohol copolymer”, “oxygen-absorbing gas barrier a layer”, “oxygen-absorbing gas barrier b layer”, “heat seal” in order from the outside. A multilayer structure in which a “resin layer” is formed by coextrusion has been proposed.

Japanese Utility Model Publication No. 5-49626 JP 2009-22553 A JP 2009-283565 A

  As described above, conventional containers for preventing oxidative deterioration of the contained material have elution due to the use of an organic solvent adhesive, anaphylactic shock due to the antioxidant added to the contained material, and the ability to absorb oxygen. Oxidation deterioration due to absence, lack of moisture resistance, whitening during high pressure steam sterilization, nasty smell during oxygen absorption reaction, and the like.

  In particular, the structure of Patent Document 2 has a problem that it has excellent enzyme barrier properties but does not have oxygen absorbing ability of the container itself.

  In addition, the multilayer structure of Patent Document 3 is excellent in enzyme barrier property and oxygen absorption property in a normal environment, but the outermost ethylene-vinyl alcohol copolymer is poor in moisture resistance, and is subjected to hot water treatment such as high-pressure steam sterilization. Whitening was not preferable in the medical container to be applied. Furthermore, there is a concern that a small amount of by-product generated in the oxygen absorption reaction of the b layer has volatility, and a strange odor is transferred to the contents.

An object of the present invention, the elution and due to the use of organic Solvent-based adhesive, lack of moisture resistance, whitening in high-pressure steam sterilization, odor during oxygen absorption reaction, no problem like, antioxidant It is an object of the present invention to provide a plastic sheet having an oxygen absorption function and a container using the same, which can achieve the prevention of oxidation of contained contents without using an agent.

The present invention has been made to solve the above problems,
It is an aspect of Claim 1.
A layer of a mixed composition comprising an ethylene-vinyl alcohol copolymer as a main component, a polyene polymer having an unsaturated double bond, and a transition metal salt as a subcomponent,
Fine powder of porous aluminosilicate, which is mainly composed of a copolymer of an α-olefin and an unsaturated monomer of unsaturated carboxylic acid or unsaturated dicarboxylic acid, provided adjacent to both surfaces of layer a. Mainly composed of b ₁ ^* layer and b ₂ ^* layer comprising a mixed composition containing -30% by weight as a minor component, and polypropylene provided adjacent to the outside of these b ₁ ^* layer and b ₂ ^* layer Ri Do from c ₁ layer and c ₂ layer that, the aluminosilicate has a hydrophobic aluminosilicates and hydrophilic aluminosilicates der Ru 5 layers of sheet a ^* one side of the melt film by co-extrusion, polypropylene plastic sheets and molded container using the same sheet B is characterized in that it is integrated by heat lamination composed mainly of
It is those that have achieved the more such a purpose to.

  According to the present invention, dissolved oxygen in the stored material is absorbed, and is excellent in sorption and adsorption of a volatile by-product generated in the oxygen absorption reaction, and has a barrier property for oxygen entering from the outside, and 121 It is possible to provide a plastic sheet for a molded container and a molded container for containing a heat-resistant food, liquid food, and the like that can cope with high-pressure steam sterilization at higher than or equal to ° C and microwave heating.

It is a fragmentary sectional view of an example of the plastic sheet of Claim 1 of this invention. It is a fragmentary sectional view of an example of the plastic sheet of Claim 2 of this invention.

The plastic sheet of the present invention basically comprises a mixed composition comprising an ethylene-vinyl alcohol copolymer as a main component, a polyene polymer having an unsaturated double bond, and a transition metal salt as an auxiliary component. a layer, b ₁ made of a resin composition mainly composed of a copolymer and polypropylene anhydride monomers adjacent to provided α- olefin and unsaturated carboxylic acids or unsaturated dicarboxylic acids on both sides of this layer a and sheet a that has been melt film layer and b ₂ layers by coextrusion, on one side thereof, a sheet in which the sheet B composed mainly of polypropylene are integrated by heat lamination, the b ₁ layer and / or b Either of the _two layers or the sheet B contains 0.5 to 30% by weight of a porous aluminosilicate fine powder.

  The a layer constituting the sheet A (hereinafter referred to as an oxygen absorbing layer) is composed of an ethylene-vinyl alcohol copolymer as a main component, a polyene polymer having an unsaturated double bond, and a transition metal salt as a subcomponent. It is a layer which consists of a mixed composition.

  The ethylene-vinyl alcohol copolymer is a main component, and the ethylene content is about 25 to 45 mol%, preferably about 27 to 44 mol%.

  The polyene polymer having an unsaturated double bond, which is an accessory component, is a polymer having hydrocarbon units having two or more double bonds as a unit. Preferred is a conjugated diene polymer, for example, polyisoprene which is a polymer of cis- or trans-1,4-isoprene which is a linear conjugated diene or a cyclized polyisoprene obtained by a pericyclic reaction of polyisoprene. Linear polymers and cyclic polymers, such as polyisoprene containing 1, polybutadiene which is a polymer of 1,3-butadiene which is a linear conjugated diene, and polybutadiene containing cyclized polybutadiene obtained by pericyclic reaction of polybutadiene Is mentioned. These may be a mixture thereof. The content of the polyene polymer is about 20 to 40% by weight, preferably about 25 to 35% by weight.

  Examples of the secondary component transition metal salts are salts of iron, nickel, copper, manganese, cobalt, rhodium, titanium, chromium, vanadium, ruthenium and the like. The acid forming the salt is preferably an organic acid, particularly a monocarboxylic acid, and stearic acid, neodecanoic acid, and the like are preferable.

  Examples of preferred transition metal salts include cobalt stearate and cobalt neodecanoate. The content of the transition metal salt is about 50 to 500 ppm, preferably about 100 to 300 ppm.

  Polyene polymers and transition metal salts mixed with ethylene-vinyl alcohol copolymer as the main component generate alcohols, aldehydes, ketones, and carboxylic acids by the oxidative cleavage reaction of polyene polymers using transition metal salts as catalysts. While absorbing oxygen.

  The composition of the mixed composition in the layer a of the present invention preferably contains a conjugated diene component that absorbs 30 cc or more of oxygen per gram. The thickness of the a layer is 5 to 35%, preferably 10 to 30%, of the total thickness of the sheet finally obtained by heat bonding. If it is less than 5%, the oxygen absorption capacity becomes insufficient. On the other hand, if it exceeds 35%, not only is the oxygen absorption capacity excessive, but also the physical properties of the sheet and the container are impaired and the manufacturing cost is unnecessarily increased. Absent.

The b ₁ layer and the b ₂ layer arranged adjacent to both surfaces of the a layer are each composed mainly of a copolymer of an α-olefin and an unsaturated monomer of unsaturated carboxylic acid or unsaturated dicarboxylic acid and polypropylene. It is a layer of the resin composition.

  Examples of α-olefins include ethylene or propylene, and polyolefins, which are homopolymers or copolymers thereof, are made of a compound obtained from a transition metal compound and an organoaluminum compound (Ziegler catalyst: for example, silica) with a chromium compound (for example, , Chromium oxide), or by homopolymerizing or copolymerizing olefins using a catalyst system (Phillips catalyst) or a radical initiator (for example, organic peroxide).

  The unsaturated monomer of unsaturated carboxylic acid or unsaturated dicarboxylic acid used in the present invention has at least one double bond and contains at least one carboxylic group or anhydride (group) thereof. Examples of the compound include (meth) acrylic acid, maleic acid, phthalic acid, maleic anhydride, and phthalic anhydride.

The copolymer of an α-olefin and an unsaturated monomer of an unsaturated carboxylic acid or unsaturated dicarboxylic acid used as the main component of the b ₁ and b ₂ layers is specifically a graft copolymer of an unsaturated monomer to the polyolefin. Or a linear multi-component copolymer is pointed out. Graft copolymerization is obtained by supplying a mixture obtained by adding 0.01 to 20 parts by weight of an unsaturated monomer and 0.001 to 20 parts by weight of an organic peroxide to 100 parts by weight of a polyolefin, and melting and reacting the mixture. .

  When the blend of the unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride monomer is less than 0.01 parts by weight with respect to 100 parts by weight of polyolefin, the resulting copolymer and the a-layer ethylene-vinyl alcohol copolymer are bonded. Poor nature. On the other hand, when the amount exceeds 20 parts by weight, the unreacted or homopolymerized unsaturated compound remains considerably in the graft reaction because the graft reaction efficiency is lowered, and the physical properties inherent to the polyolefin are impaired.

  Representative examples of the organic peroxide used in the present invention include t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and di-t-butyl peroxide. It is done. Among the organic oxides, those having a half-life of 100 to 280 ° C. per minute are desirable, and those having a temperature of 120 to 230 ° C. are particularly preferable. These organic peroxides may be used alone or in combination of two or more.

  Moreover, if the blending ratio of the organic peroxide to 100 parts by weight of polyolefin is less than 0.001 part by weight, a satisfactory graft copolymer cannot be obtained. On the other hand, if it exceeds 20 parts by weight, the physical properties inherent to the polyolefin are impaired.

  Such a mixture is put into an ordinary extruder, melted and kneaded therein, and a graft reaction proceeds, whereby a graft-modified product is obtained. At this time, the extruder used may be either a non-vented type or a vented type, but from the viewpoint of removing unreacted or homopolymerized unsaturated compounds and decomposition products of organic peroxides, a vented type extruder is used. Is desirable. Further, the kneading temperature is 180 to 250 ° C., and it is preferably 190 to 230 ° C., although it varies depending on the type of polyolefin, unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride monomer and organic peroxide used. The residence time in the extruder is 60 seconds or longer, and particularly 90 seconds or longer is preferable. When the kneading temperature is less than 180 ° C., the graft reaction is not performed well. On the other hand, when the temperature exceeds 250 ° C., some of the polyolefin deteriorates, and depending on the unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride monomer, the boiling point is exceeded and thermal deterioration occurs. Further, if the residence time in the extruder is less than 60 seconds, a satisfactory graft reaction cannot be performed.

Copolymers of α-olefin and unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride are commercially available and can be used. The mixing ratio of the copolymer of the α-olefin and the unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride in the b ₁ , b ₂ layer resin composition is preferably 30 to 70% by weight. The mixing ratio of the copolymer in the resin composition is preferably 30 to 70% by weight.

Polypropylene may be mixed in the b ₁ and b ₂ layers. The polypropylene refers to a homopolymer, a block copolymer, or a random copolymer. The comonomer in the copolymer is ethylene or the like. These polypropylenes are commercially available and can be used. As a physical property, it is preferable to use a material having an MFR at 230 ° C. within a range of 0.50 to 2.00 g / 10 min suitable for sheet film formation. The mixing ratio of the copolymer and the polypropylene in the b ₁ and b ₂ layer resin composition is preferably 30:70 to 100: 0 by weight.

The ratio η _{(polypropylene)} / η _{(copolymer )} of the melt viscosity at the same temperature between the copolymer mixed as the main component with the b ₁ and b ₂ layers and polypropylene is preferably 2.0 or more. . If it is less than 2.0, both tend to be uniformly dispersed, and the polar group present at the interface with the ethylene-vinyl alcohol copolymer of the a layer is diluted and sufficient adhesion is not exhibited.

The resin composition of the b ₁ layer and the b ₂ layer may be different as long as they are within the above range, but may be the same unless there is a special purpose.

b ₁ layer and _{b 2} layers each thickness about 10~50μm of, preferably about 10 to 30 [mu] m, the proportion in the final heat bonded combined total thickness of the sheet obtained, about 0.5% to 10% Preferably, it is about 1 to 5%. The thickness of b ₁ layer and b ₂ layers may be different, may be the same unless otherwise purposes.

In the embodiment of claim 1 of the present invention, b ₁ ^* layer and b ₂ ^* adjacent to the outer layer a layer composed mainly of polypropylene. This is to prevent water vapor from entering the a layer during autoclave sterilization and hydrolyzing the ethylene-vinyl alcohol copolymer. Polypropylene refers to a commercially available homopolymer, block copolymer, or random copolymer, and a material having an MFR at 230 ° C. in the range of 0.50 to 2.00 g / 10 min suitable for sheet film formation may be used. preferable.

5 layers comprising c ₁ , b ₁ , a, b ₂ and c ₂ in which the a layer in the aspect of claim 1 and b ₁ and b ₂ layers on both sides thereof, and c layers adjacent to both b layers are arranged. The sheet A is obtained by melt film formation by an inflation coextrusion method that does not use an organic solvent-based adhesive. Sheet A is formed into a cylindrical 5-layer by using a 5-type 5-layer inflation coextrusion film forming machine equipped with 5 extruders or a 3-type 5-layer inflation co-extrusion film forming machine equipped with 3 extruders. A film is formed while folding the sheet, and both ends are cut off to obtain a sheet-like sheet.

  Further, the five-layer sheet A is formed into a cylindrical sheet composed of three layers a, b, and c by a three-kind three-layer inflation co-extrusion film forming machine equipped with three extruders. The inner layers (a layers) of the folded cylindrical sheet can be bonded together by thermocompression bonding to obtain a 5-layer sheet composed of c, b, a, b, and c.

  It is preferable that the sheet A of the present invention has the latter method in which the thickness of the sheet A can be made into five layers by rolling to make the thickness uniform, improve the adhesion strength between layers, and improve the gas barrier property by increasing the crystallinity.

  The plastic sheet which has the oxygen absorption function which is the aspect of Claim 1 is obtained by integrating the single side | surface adjacent to the said sheet | seat A, and the sheet | seat B which has a polypropylene as a main component by heat bonding. The heat bonding is preferably a heat laminating method in which the heat-bonding is continuously passed between press rolls heated to 180 to 250 ° C.

FIG. 1 shows a layer structure of an example of a plastic sheet according to the first aspect.
Next, a plastic sheet according to the second aspect will be described.

The b ₁ and b ₂ layers adjacent to both sides of the a layer are a mixed composition mainly composed of a copolymer of an α-olefin and an unsaturated monomer of unsaturated carboxylic acid or unsaturated dicarboxylic acid and polypropylene or polypropylene. It is. The preferred copolymer and polypropylene used in the b ₁ and b ₂ layers are the same as those described in the embodiment of claim 1.

Above a layer and 3-layer sheet A consisting of b ₁ · a · b ₂ where we arranged b _1, b ₂ layers on both sides thereof is by melt film by an inflation co-extrusion method that does not use organic solvent-based adhesive can get. Sheet A is formed into a cylindrical three-layer by a three-kind three-layer inflation coextrusion film forming machine equipped with three extruders or by a two-kind three-layer inflation co-extrusion film forming machine equipped with two extruders. A film is formed while folding the sheet, and both ends are cut off to obtain a sheet-like sheet.

  Further, the three-layer sheet A was formed into a cylindrical sheet composed of two layers a and b by a two-type two-layer inflation co-extrusion film forming machine equipped with two extruders, and was folded during or after the process. By bonding the inner layers (a layer) of the cylindrical sheet by thermocompression bonding, a three-layer sheet consisting of b, a and b can be obtained.

  The sheet A of the present invention is preferably the latter method in which the two layers are rolled and formed into three layers to make the thickness uniform, improve the adhesion strength between layers, and improve the gas barrier property by increasing the crystallinity.

The sheet B is mainly composed of polypropylene. Polypropylene may be a homopolymer, a block polymer, or a random polymer. Comonomers in the case of copolymers are ethylene and the like. This polypropylene may be the same as or different from the b ₁ and b ₂ layers.

  Examples of other components that can be included in the sheet B include low-density polyethylene, and the content is 20% by weight or less, for example, 3 to 10% by weight. The thickness of the sheet B is about 300 to 1500 μm, and is about 50 to 85%, preferably about 60 to 75% of the total thickness of the final sheet.

  A plastic sheet is obtained by integrating one side adjacent to the sheet A and a sheet B mainly composed of polypropylene by heat bonding. The heat bonding is preferably a heat laminating method in which the pressure bonding rolls heated to 180 to 200 ° C. are continuously passed.

  The final thickness of the plastic sheet obtained by laminating the sheet A and the sheet B is about 400 to 1800 μm, preferably about 800 to 1300 μm.

Plastic sheet of the present invention, b ₁ layer above, b ₂ layers, at least one of the sheet B, and fine powder of the aluminosilicate is mixed 0.5-30 wt% with pores in the crystals. The aluminosilicate can adsorb or sorb alcohols, aldehydes, ketones and carboxylic acids generated by the oxygen absorption reaction of the a layer. Moreover, aluminosilicate is excellent in hygroscopicity, and can suppress the water intrusion to the a layer in the high-pressure steam sterilization process. Furthermore, the aluminosilicate fine powder can improve the transparency of the b ₁ and b ₂ layers as a crystal nucleating agent during film formation.

  The aluminosilicate that adsorbs or sorbs alcohol, aldehyde, ketone, and carboxylic acid is a hydrophobic salt with an increased ratio of silicic acid, and the pore diameter of the aluminosilicate is preferably 0.5 nm or less.

  The hygroscopic aluminosilicate is a hydrophilic salt in which the ratio of silicic acid is reduced, and the pore diameter of the aluminosilicate is preferably 0.5 nm or less. Moreover, it is preferable that the particle size of the above-mentioned aluminosilicate fine powder has a center particle size distribution of 3 to 10 μm. This aluminosilicate is a kind of zeolite and can be selected from commercially available zeolites.

  Since the ring-opening polymer of the cyclic olefin monomer or the hydrogenated product of the ring-opening polymer or the addition polymer of the cyclic olefin monomer is excellent in moisture-proof property, it can suppress moisture intrusion into the layer a in the high-pressure steam sterilization process. It is preferable to add to layer b and / or sheet B.

The cyclic olefin monomer is not particularly limited, and examples thereof include norbornene monomers and monocyclic cyclic olefin monomers. The norbornene-based monomer is a monomer having a unit derived from a norbornene structure in the monomer structure, and specifically includes, for example, bicyclo [2.2.1] hept-2-ene (commonly used norbornene), tricyclo [4. 3.0.1 ^2,5 ] deca-3,7-diene (common name dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (conventional Names methanotetrahydrofluorene) and tetracyclo [4.4.0.1 ^2,5 . 1 ^7,10 ] dodec-3-ene (common name: tetracyclododecene) and the like. Further, these norbornene monomers may have a hydrocarbon group having 1 to 3 carbon atoms. Specific examples of the monocyclic olefin monomer include cyclohexene, cycloheptene, and cyclooctene. These cyclic olefin monomers can be used alone or in combination of two or more.

  The ring-opening polymer of a cyclic olefin monomer is obtained by polymerizing a cyclic olefin monomer by a metathesis reaction in the presence of a known ring-opening polymerization catalyst, and is disclosed, for example, in JP-A-2008-18063. . The hydrogenated product of the ring-opened polymer of the cyclic olefin monomer is obtained by hydrogenating the ring-opened polymer with a known hydrogenation catalyst.

  Moreover, as another monomer which can be addition-copolymerized with a cyclic olefin monomer, C2-C20 alpha olefins, such as ethylene, propylene, 1-butene, 1-hexene, are mentioned, for example. These α-olefins can be used alone or in combination of two or more.

  The addition (co) polymer of the cyclic olefin monomer can be obtained by polymerization using a known catalyst comprising a titanium, zirconium compound and an organoaluminum compound. Among those commercially available as cyclic polyolefins, examples of the addition (co) polymers of cyclic olefin monomers include Apel (registered trademark) manufactured by Mitsui Chemicals, Inc., TOPAS (registered trademark) manufactured by TICONA, and the like. Examples of the hydrogenated product of the ring-opening polymer include ZEONOR (registered trademark) and ZEONEX (registered trademark) manufactured by Nippon Zeon Co., Ltd.

The cyclic polyolefin preferably has a glass transition temperature (hereinafter sometimes referred to as Tg) of 70 ° C to 180 ° C, more preferably 100 to 140 ° C. When Tg is less than 70 ° C., the heat resistance is lowered and may not be suitable for high-pressure steam sterilization. On the other hand, when Tg exceeds 140 ° C., the film forming property and the heat bonding property of the multilayer body may be deteriorated. Here, the glass transition temperature is JIS
It is a value measured with a differential scanning calorimeter (hereinafter referred to as DSC) in accordance with K 7121, and is a value described in a manufacturer's catalog and technical data.

  The Tg of the cyclic polyolefin can be arbitrarily adjusted by a method of mixing a plurality of types of cyclic polyolefins having good compatibility at an appropriate ratio. The degree of compatibility of the mixture of cyclic polyolefins can be determined by measuring the Tg of the mixture by DSC. In the case of a mixture with good compatibility, only one Tg is observed, whereas when the compatibility is not good, a plurality of Tg is observed. It is preferable that the mixture has good compatibility because heat resistance that can withstand the target high-pressure steam sterilization temperature and film-forming properties can be achieved.

The aluminosilicate and the ring-opening polymer (including hydrogenated products and addition polymers) (hereinafter also referred to as “adsorption composition”) may be used in any of b ₁ layer, b ₂ layer, and sheet B. Can also be added, and may be added to all of them. The amount contained in these layers and sheets is about 0.5 to 30% by weight of aluminosilicate, preferably 1 to 20% by weight. When a ring-opening polymer (including a hydrogen compound and an addition polymer) is also added, the amount is about 5 to 20% by weight, preferably about 3 to 10% by weight. The above weight% is based on the total weight of these layers and sheets, and when the b ₁ layer, b ₂ layer, and sheet B contain the adsorbing composition, the aforementioned wt% is the amount of the adsorbing composition. It becomes the weight% of the remaining part excluding the weight.

In the plastic sheet of the present invention, in FIG. 1 the basic structure of a case of adding an adsorption composition b ₁ layer and b ₂ layers, 2 the basic configuration of a case of adding an adsorption composition into a sheet B.

  A method for producing the molded container of the present invention using the plastic sheet of the above embodiment will be described.

  The plastic sheet is softened by heating to a temperature just below the melting point of polypropylene of 140 to 160 ° C., inserted into a mold in a solid state, and then subjected to true solid-phase pressure molding to provide the oxygen absorption function of the present invention. Is obtained.

The present invention will be described more specifically with reference to examples.
The following resins were used.
PP: Polypropylene, made by Sun Allomer, “PB370A”
Density = 0.90 g / cm ³ , MFR = 1.3 g / 10 min AD: maleic anhydride grafted polypropylene,
ZELAS “MC721AP” manufactured by Mitsubishi Chemical
Density = 0.90 g / cm ³ , MFR = 3.5 g / 10 min COC: Cyclic polyolefin, manufactured by Mitsui Chemicals, Appel “APL6013T”
Density = 1.04 g / cm ³ , MFR = 15 g / 10 min,
Glass transition temperature = 125 ° C
ASi-1: Hydrophobic aluminosilicate, Union Showa, molecular sieve
“ABSENTS”, average particle size = 3 to 6 μm,
ASi-2: hydrophilic aluminosilicate, Union Showa, molecular sieve
“3A”, average particle size = 10 μm,
ACT: Oxygen-absorbing resin, ethylene-vinyl alcohol copolymer, manufactured by Kuraray,
100 parts by weight of Eval "L171B" melt-kneaded at 200 ° C with 10 parts by weight of poly-1,3-dioxepin as a polyene polymer and 0.03 parts by weight of cobalt stearate as a transition metal salt.
Density = 1.19 g / cm ³ , MFR = 4.0 g / 10 min,
Melting peak temperature = 180 ° C
EVOH: Ethylene-vinyl alcohol copolymer, Kuraray, Eval
“L171B”,
Density = 1.18 g / cm ³ , MFR = 4.2 g / 10 min,
Melting peak temperature = 183 ° C

The film formation of the three-layer sheet was performed under the following conditions using a two-kind three-layer air-cooled inflation film forming machine.
Outer / middle layer: Screw extruder with an outer diameter of 40 mm and a compression ratio of 2.7 (extrusion temperature 210 ° C.)
Inner layer: Screw extruder with an outer diameter of 65 mm and a compression ratio of 1.4 (extrusion temperature 240 ° C.)
Die: Outer diameter 200mm, Lip distance 3mm, Temperature 240 ℃
Blow ratio: 0.6
Film forming speed 13m / min

  The three-kind five-layer sheet corresponding to the sheet A according to claim 1 was produced by passing between the bonding rolls heated to a temperature of 240 ° C. at a speed of 10 m / min while keeping the three-layer sheet in a cylindrical shape. .

Film formation of the single layer sheet used for heat bonding was performed under the following conditions by operating only the inner layer extruder of the air-cooled inflation film forming machine.
Inner layer: Screw extruder with an outer diameter of 65 mm and a compression ratio of 1.4 (extrusion temperature 210 ° C.)
Die: Outer diameter 200mm, Lip distance 3mm, Temperature 240 ℃
Blow ratio: 0.6
Film forming speed 13m / min

  The heat bonding of a three-layer sheet or a five-layer sheet and a single-layer sheet is performed by passing two sheets superimposed between a metal roll heated to 200 ° C. and a rubber support roll installed at a gap of 1 mm. Four or six-layer sheets were used.

<Preparation of evaluation specimen using 4-layer or 6-layer sheet / Measurement of dissolved oxygen concentration>
・ Two sheets of the same type are heat-sealed at a temperature of 240 ° C., a pressure of 0.2 MPa, and a time of 1.0 second with the single-layer sheet side as the inner surface, to produce a three-sided heat-sealed bag with an inner size of 100 × 100 mm.

・ Fix the sensor chip for measuring dissolved oxygen concentration on the inner surface of the three-sided bag with a special adhesive.
・ Gently move distilled water with a dissolved oxygen concentration of 7.0 to 7.5 ppm into a glass container with a lid connected to a vacuum pump in a constant temperature room at 23 ° C.
-The sealed glass container was placed in an ultrasonic cleaning tank and deaerated by a vacuum pump while applying ultrasonic waves for 10 minutes to prepare distilled water having a dissolved oxygen concentration of 4.8 to 6.3 ppm.
-Gently transfer 100 ml of the prepared distilled water to the above-mentioned three-way heat-sealing bag, and immediately seal it with heat-sealing in a fully-filled state.
・ Samples should be autoclaved at 121 ° C for 25 minutes.
・ Leave all specimens in a constant temperature and humidity chamber of 40 ° C. × 70% RH.
-Remove the specimen left for 14 days, and lower the specimen to 23 ° C in a constant temperature room at 23 ° C.
-Measure the dissolved oxygen concentration in the bag by detecting the sensor chip of the specimen with a non-destructive oxygen concentration meter (Fibox-3 type, manufactured by Sanyo Trading Co., Ltd.).

<Measurement of odor>
-Open the sample bag where the dissolved oxygen concentration is measured.
-The stored distilled water is immediately transferred to a clean glass container with a lid, and sensory odor and taste are determined in the following three stages.
A: Tasteless odorless,
B: Slight smell and taste
C: The table shows the obtained results that give a considerable odor and taste.

  The plastic sheet of the present invention is excellent in oxygen absorbing ability, moisture proofing, dehumidifying ability, and absorbing ability of off-flavor components, and can be widely used as containers for foods, liquid foods and the like.

  * Represents that it contains an adsorbent composition.

Claims (4)

A layer of a polyene polymer having an ethylene-vinyl alcohol copolymer as a main component and an unsaturated double bond; a layer of a mixed composition having a transition metal salt as a subcomponent; and an α-olefin adjacent to both sides of the layer a And an unsaturated carboxylic acid or unsaturated dicarboxylic acid anhydride monomer as a main component and a porous aluminosilicate fine powder of 0.5 to 30% by weight as a minor component. b ₁ ^* layer and _b ^{2 *} layers, and _{c 1} layer and _{c 2} layer composed mainly of polypropylene which is provided adjacent to the outside of these _b ^{1 *} layer and _b ^{2 *} layers, Tona is, the aluminosilicate, the sheet a ^* one side of the melt film by coextrusion hydrophobic aluminosilicates and hydrophilic aluminosilicates Ru der five layers,
A plastic sheet having an oxygen-absorbing function, wherein the sheet B mainly composed of polypropylene is integrated by heat bonding. At least one of the b ₁ ^* layer or the b ₂ ^* layer further contains 5 to 20% by weight of a ring-opened polymer of a cyclic olefin monomer, a hydrogenated product of the ring-opened polymer, or an addition polymer of a cyclic olefin monomer. Item 1. A plastic sheet according to Item 1. a layer absorbs 30cc more oxygen per 1g, claim 1 or 2 SL placing a plastic sheet having an oxygen absorbing function of, characterized in that 5 to 35% of the total thickness. Heat pressing a plastic sheet according to below the crystallization temperature of the polypropylene to any one of claims 1 to 3 containers having an oxygen absorbing function, wherein the inserted formed in the left mold in the solid state.

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