JP2017136741A - Multilayer sheet for draw molding, molding and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer sheet for draw molding which hardly causes poor molding and pinholes when draw-molded, and exhibits sufficient gas barrier properties even after molded.SOLUTION: There is provided a multilayer sheet for draw molding which has a base material 1 containing a thermoplastic resin, a sealant layer 5 containing a thermoplastic resin, and a gas barrier layer 4 that is provided between the base material 1 and the sealant layer 5 and contains a resin, where melting points of the thermoplastic resins of the base material 1 and the sealant layer 5 are a temperature higher than a glass transition temperature of the resin of the gas barrier layer 4 by 15°C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a stretch-molded multilayer sheet, a molded article, and a method for producing the same.

  Packaging materials used for packaging foods, non-foods (pharmaceuticals, electronic components, etc.) block the permeation of gases such as oxygen and water vapor in order to suppress the deterioration of the contents and maintain their functions and properties. It is required to have gas barrier properties. As a packaging material having a gas barrier property, a gas barrier sheet in which a gas barrier layer is provided on at least one surface of a base material is widely used.

  In Patent Document 1, when a non-stretched and single-layer sheet made of a heat-meltable fluororesin is heated and vacuum-formed or vacuum-pressure formed into a container shape, the heating temperature of the sheet is around the melting point of the heat-meltable fluororesin. Preferably, it is described that when the heating temperature is greatly deviated from the vicinity of the melting point, molding defects and pinholes occur.

JP 2009-214414 A

It is preferable that a sealant layer is provided on the sealing surface of the molding container in order to seal the opening with a lid material or the like after the contents are stored in the molding container.
However, according to the study by the present inventors, when a multilayer sheet in which a base material, a gas barrier layer, and a sealant layer are laminated in this order is stretch-molded by a vacuum molding machine or the like, the original gas barrier property may not be exhibited after molding. is there.

  The present invention has been made in view of the above circumstances, and a stretch-molded multilayer sheet that hardly causes molding defects and pinholes when stretch-molded, and that exhibits sufficient gas barrier properties even after molding, and It aims at providing the manufacturing method of the molded article and molded article using this.

The present invention has the following aspects.
<1> A base material containing a thermoplastic resin, a sealant layer containing a thermoplastic resin, and a gas barrier layer containing a resin provided between the base material and the sealant layer,
A multi-layer sheet for stretch molding, wherein the thermoplastic resin of each of the base material and the sealant layer has a glass transition temperature of the resin of the gas barrier layer + 15 ° C or higher.
<2> The multilayer sheet for stretch molding according to <1>, wherein the thermoplastic resin of the sealant layer has a melting point of the resin of the gas barrier layer + 30 ° C. or higher.
<3> The stretch-molded multilayer sheet according to <1> or <2>, wherein the thermoplastic resin of the base material has a melting point of the resin of the gas barrier layer + 30 ° C. or higher.
<4> The multilayer sheet for stretch molding according to any one of <1> to <3>, wherein the thermoplastic resin of the sealant layer is a polypropylene polymer.
<5> Any one of <1> to <4>, wherein the gas barrier layer includes a layer (A) containing a polycarboxylic acid polymer and a layer (B) containing a polyvalent metal component and a binder resin. A multilayer sheet for stretch molding as described in 1.
<6> The multilayer sheet for stretch molding according to <5>, wherein the glass transition temperature of the binder resin of the layer (B) is lower than the glass transition temperature of the polycarboxylic acid polymer of the layer (A).
<7> The multilayer sheet for stretch molding according to <5> or <6>, wherein the layer (A) further contains a plasticizer.
<8> A molded article using the stretch-molded multilayer sheet according to any one of <1> to <7>.
<9> The multilayer sheet for stretch molding according to any one of <1> to <7> is heated so as to have a glass transition temperature of the resin of the gas barrier layer + 15 ° C. or more and stretched to obtain a molded product. The manufacturing method of the molded article which has a process to obtain.

  According to the present invention, a multi-layer sheet for stretch molding that hardly forms defects and pinholes when stretch-molded and exhibits a sufficient gas barrier property even after molding, and a molded product and a molded product using the same. Can be provided.

It is a schematic cross section which shows the structure of the multilayer sheet for stretch molding of 1st embodiment of this invention. It is a top view which shows the molded product (round shape molding container) of 2nd embodiment of this invention. It is III-III sectional drawing of the molded article shown in FIG. It is a top view which shows the molded article (square shape molded container) of 3rd embodiment of this invention. It is VV sectional drawing of the molded article shown in FIG.

  Hereinafter, with reference to the drawings, embodiments of the multilayer sheet for stretch molding of the present invention (hereinafter also simply referred to as “multilayer sheet”), a molded product, and a manufacturing method thereof will be described in detail. However, the present invention is not limited to the embodiments described below, and modifications such as design changes can be added based on the knowledge of those skilled in the art, and embodiments to which such modifications are added are also possible. It is included in the scope of the present invention.

<First embodiment>
FIG. 1 is a schematic cross-sectional view showing a configuration of a multilayer sheet 10 according to the first embodiment of the present invention.
The multilayer sheet 10 includes a base material 1, a sealant layer 5, and a gas barrier layer 4 provided between the base material 1 and the sealant layer 5. That is, the base material 1, the gas barrier layer 4, and the sealant layer 5 are laminated in this order.
In the multilayer sheet 10, the base material 1 and the gas barrier layer 4 are directly laminated. The gas barrier layer 4 and the sealant layer 5 are laminated directly or via an adhesive layer (not shown).
The gas barrier layer 4 is formed by laminating a first layer 2 and a second layer 3 in order from the substrate 1 side.

In the multilayer sheet 10, the sealant layer 5 is disposed on the outermost layer on the content side of the multilayer sheet 10, and the substrate 1 is disposed on the outermost layer on the outer side of the multilayer sheet 10.
Here, the content side of the multilayer sheet 10 means that the multilayer sheet 10 is stretch-molded to form a molded product (for example, a molding container according to second to third embodiments described later), and the content is accommodated in the molded product and packaged. This means the side that comes into contact with the contents when the body is used. The outside means the side opposite to the contents side.

  Although the thickness of the multilayer sheet 10 before stretch molding is appropriately determined according to the thickness of the molded product, it is preferably 10 μm or more and 50 mm or less, and more preferably 10 μm or more and 1500 μm or less.

(Substrate 1)
The base material 1 contains a thermoplastic resin.
The kind of thermoplastic resin is not specifically limited, For example, a polyester-type polymer, a polyamide-type polymer, a polyolefin-type polymer etc. are mentioned.
Examples of the polyester polymer include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyε-caprolactone, polyhydroxybutyrate, polyhydroxyvalylate, and copolymers thereof. Examples of polyamide polymers include nylon 6, nylon 66, nylon 12, nylon 6,66 copolymer, nylon 6,12 copolymer, metaxylene adipamide / nylon 6 copolymer, and copolymers thereof. Is mentioned. Examples of the polyolefin polymer include low density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, poly-4-methylpentene, cyclic polyolefin, copolymers thereof, and acid-modified products thereof.
As the thermoplastic resin of the substrate 1, polyethylene terephthalate, polyamide polymer, cyclic olefin copolymer, polypropylene polymer, and the like are preferable from the viewpoint of stretch moldability.

The melting point of the thermoplastic resin of the substrate 1 is preferably the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C. or more, and preferably the glass transition temperature of the resin of the gas barrier layer 4 + 30 ° C. or more. When the melting point of the thermoplastic resin of the base material 1 is lower than the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C., when the multilayer sheet 10 is stretched and heated to a temperature near the melting point of the thermoplastic resin of the base material 1 Moreover, since the stretchability of the gas barrier layer 4 is poor, the gas barrier layer 4 is cracked, and the original gas barrier property may not be exhibited after molding.
When the gas barrier layer 4 is composed of a plurality of layers and the glass transition temperatures of the resins of the respective layers are different, the melting point of the thermoplastic resin of the substrate 1 is the highest glass transition temperature + 15 ° C. or higher among the glass transition temperatures of the resins of the respective layers. It is preferable that the glass transition temperature of the resin in each layer is the highest glass transition temperature + 30 ° C. or higher.
The melting point of the thermoplastic resin is measured by differential scanning calorimetry (DSC). Detailed measurement conditions are as shown in Examples described later.

  The melting point of the thermoplastic resin of the substrate 1 preferably satisfies the above relationship with the glass transition temperature of the resin of the gas barrier layer 4 and is preferably 130 ° C. or higher and 300 ° C. or lower. When the melting point of the thermoplastic resin of the base material 1 is less than the lower limit of the above range, when the container formed from the multilayer sheet 10 is used for retort, the container may be deformed by heat due to retort treatment, and the upper limit of the above range is exceeded. When it exceeds, there exists a possibility that the moldability to a container may worsen.

The base material 1 may be comprised from the single layer, and may be comprised from the several layer. When it is composed of a plurality of layers, the thermoplastic resin contained in each layer may be the same or different as long as the melting point is the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C. or higher.
As the substrate 1, for example, the thermoplastic resin film can be used.
The substrate 1 may be stretched or unstretched.
From the viewpoint of adhesion to the gas barrier layer 4, the surface of the substrate 1 may be subjected to surface activation treatment such as corona treatment, flame treatment, and plasma treatment.

  The thickness of the base material 1 before stretch molding of the multilayer sheet 10 is preferably 10 μm or more and 50 mm or less, and more preferably 10 μm or more and 500 μm or less. If the thickness of the base material 1 is not less than the above lower limit value, there is no molding defect such as the occurrence of pinholes and the moldability is good. If the thickness of the base material 1 is less than or equal to the above upper limit value, when the heat sterilization treatment is performed after the multilayer sheet 10 is formed into a molded product, water vapor is generated from the outside of the molded product (base material 1 side) to the base material 1. The gas is supplied to the gas barrier layer 4 and the formation of an ionic bond between the carboxy group of the polycarboxylic acid polymer and the polyvalent metal ion as described later easily proceeds.

(Gas barrier layer)
The gas barrier layer 4 includes a first layer 2 and a second layer 3. The first layer 2 is a layer (A) containing a polycarboxylic acid polymer, and the second layer 3 is a layer (B) containing a polyvalent metal component and a binder resin.
When the gas barrier layer 4 is subjected to a heat sterilization treatment such as a retort treatment, for example, the carboxy group of the polycarboxylic acid polymer is a polyvalent metal ion derived from the polyvalent metal component contained in the second layer 3. An ionic bond is formed, and a stable gas barrier property is exhibited. Therefore, a molded article having the gas barrier layer 4 having the first layer 2 and the second layer 3 is suitable for retort use.

The glass transition temperature of the resin of the gas barrier layer 4 is not higher than the melting point of the thermoplastic resin of the base material 1 and the sealant layer 5 at −15 ° C. or less.
The “glass transition temperature of the resin of the gas barrier layer” is the glass transition temperature of the resin forming a continuous phase (matrix) in the gas barrier layer, and is measured by differential scanning calorimetry (DSC). Detailed measurement conditions are as shown in Examples described later.
The gas barrier layer 4 of the present embodiment is composed of a plurality of layers (the first layer 2 and the second layer 3). In this case, the resin of each of the plurality of layers (the polycarboxylic acid type of the first layer 2) The glass transition temperature of the polymer and the binder resin of the second layer 3) is a melting point of the thermoplastic resin of the base material 1 and the sealant layer 5 of −15 ° C. or lower.

[First layer (layer (A))]
The first layer 2 is a layer constituting the gas barrier layer 4 and contains a polycarboxylic acid polymer.
The polycarboxylic acid polymer is a general term for polymers having two or more carboxy groups in the molecule.
The polycarboxylic acid-based polymer is not particularly limited, and specific examples include acrylic acid or methacrylic acid homopolymers, copolymers of acrylic acid and methacrylic acid, acrylic acid and / or methacrylic acid, acrylic And copolymers with other ethylenically unsaturated carboxylic acids other than acid and methacrylic acid. Examples of other ethylenically unsaturated carboxylic acids include crotonic acid, vinyl lactic acid, maleic acid, fumaric acid, aconitic acid, itaconic acid, mesaconic acid, citraconic acid, and methylene malonic acid. A polycarboxylic acid type polymer may be used individually by 1 type, and may be used in combination of 2 or more type.

  As described above, the glass transition temperature of the polycarboxylic acid-based polymer is the melting point of the thermoplastic resin of each of the base material 1 and the sealant layer 5 -15 ° C. or less, and the glass transition temperature of the thermoplastic resin of each of the base material 1 and the sealant layer 5 is The melting point is preferably −30 ° C. or lower.

The number average molecular weight of the polycarboxylic acid polymer is not particularly limited. From the viewpoint of the formability of the first layer 2, the range is preferably 10,000 or more and 10,000,000 or less, and more preferably 5,000 or more and 1,000,000 or less.
The number average molecular weight of the polycarboxylic acid polymer is a value in terms of polystyrene determined by gel permeation chromatography (GPC).

  The polycarboxylic acid polymer as a raw material (polycarboxylic acid polymer before forming an ionic bond with the metal ion of the polyvalent metal component contained in the second layer 3) is a gas barrier property of the molded product, high-temperature steam. As long as the resistance to hot water is not impaired, a part of the carboxy group may be neutralized with a monovalent metal (such as an alkali metal) or ammonia.

The polycarboxylic acid polymer as a raw material (polycarboxylic acid polymer before forming an ionic bond with the metal ion of the polyvalent metal component contained in the second layer 3) is a gas barrier property of the molded product, high-temperature steam. From the viewpoint of stability to hot water, when it is formed into a film alone, the oxygen permeability coefficient measured under dry conditions (30 ° C., relative humidity 0%) is 1000 cm ³ (STP) · μm / preferably ^(m 2 · day · MPa) or ^{less, 500cm 3 (STP) · μm} / more preferably (m 2 · day · MPa) or ^{less, 100cm 3 (STP) · μm} / (m 2 · Day · MPa) or less is particularly preferable.

The oxygen permeability coefficient here can be determined by the following method, for example.
A polycarboxylic acid polymer is dissolved in a solvent such as water to prepare a 10% by mass solution. Next, the prepared solution is coated and dried on a plastic substrate using a bar coater to produce a coating film on which a polycarboxylic acid polymer layer having a thickness of 1 μm is formed. About the obtained coating film, the oxygen permeability in 30 degreeC and 0% of relative humidity is measured. Here, any plastic film whose oxygen permeability is known is used as the substrate. And if the oxygen permeability of the obtained coating film is 1/10 or less with respect to the oxygen permeability of the plastic film used alone as the base material, the measured value of the oxygen permeability is almost polycarboxylic acid. This can be regarded as the oxygen permeability of the single polymer layer alone. Further, since the obtained value is the oxygen permeability of the polycarboxylic acid polymer layer having a thickness of 1 μm, the value can be converted to an oxygen permeability coefficient by multiplying the value by 1 μm.

The first layer 2 preferably further includes a plasticizer.
The plasticizer is added to increase the stretchability of the first layer 2. Specifically, by adding a plasticizer to the polycarboxylic acid polymer, the glass transition temperature of the polycarboxylic acid polymer in the first layer 2 is lowered, and the polymer can be stretched at a lower temperature condition. it can.

Examples of the plasticizer include glycerin and its polymer, glycols and the like. Specific examples thereof include glycerin, polyglycerin, ethylene glycol, trimethylene glycol, propylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polyethylene oxide and the like. . These plasticizers may be used alone or in combination of two or more.
Among these, as the plasticizer, glycerin, polyglycerin, ethylene glycol, polyethylene glycol, and the like are preferable from the viewpoint of stretch moldability of the multilayer sheet 10 and gas barrier properties of the obtained molded product.

  In the first layer 2, the mass ratio of the polycarboxylic acid polymer to the plasticizer (polycarboxylic acid polymer / plasticizer) is preferably in the range of 95/5 to 80/20. More preferably, it is in the range of 95/5 to 85/15. If content of the said plasticizer is more than the lower limit of the said range, the drawability of the 1st layer 2 will be more excellent. If the content of the plasticizer exceeds the upper limit of the above range, the proportion of the polycarboxylic acid polymer that contributes to the gas barrier properties is relatively reduced, which may result in insufficient gas barrier properties.

  The first layer 2 may further contain other components other than the polycarboxylic acid polymer and the plasticizer as necessary. Examples of other components include silane coupling agents.

  The thickness of the first layer 2 before stretch molding of the multilayer sheet 10 is preferably 0.01 μm or more and 20 μm or less, more preferably 0.05 μm or more and 10 μm or less, in terms of oxygen gas barrier properties. It is particularly preferably 0.1 μm or more and 5 μm or less. When the thickness of the first layer 2 is less than the lower limit of the above range, film formation tends to be difficult, and when the thickness of the first layer 2 exceeds the upper limit of the above range, the productivity is poor. Tend.

[Second layer 3]
The second layer 3 includes a polyvalent metal component and a binder resin.
The polyvalent metal component is used to ionically bond with the carboxy group of the polycarboxylic acid polymer contained in the first layer 2 to improve the gas barrier property. The binder resin is used for improving the film formability of the second layer 3.

Examples of the polyvalent metal component include a single polyvalent metal atom and a polyvalent metal compound.
The polyvalent metal is a metal having a metal ion valence of 2 or more, such as alkaline earth metals such as beryllium, magnesium, calcium, titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper, zinc, etc. A transition metal, aluminum, etc. are mentioned. From the viewpoint of gas barrier properties of molded articles, resistance to high-temperature steam and hot water, and productivity, the polyvalent metal is preferably a divalent metal having a metal ion valence of 2.

  Specific examples of the polyvalent metal compound include oxides, hydroxides, carbonates, organic acid salts and inorganic acid salts of the polyvalent metals, ammonium complexes and secondary to quaternary amine complexes of the polyvalent metals, and complexes thereof. And carbonates and organic acid salts thereof, alkyl alkoxides of polyvalent metals, and the like. Organic salts include acetate, oxalate, citrate, lactate, phosphate, phosphite, hypophosphite, stearate, monoethylenically unsaturated carboxylate, etc. It is done. Examples of inorganic acid salts include chlorides, sulfates and nitrates.

The form of the polyvalent metal component is not particularly limited. From the viewpoint of the transparency of the multilayer sheet 10, the polyvalent metal component is preferably granular and has a smaller particle size. Moreover, when preparing the coating liquid for manufacturing the multilayer sheet 10 so that it may mention later, a polyvalent metal compound is granular also from the viewpoint of obtaining the efficiency at the time of preparation, and obtaining a more uniform coating liquid, The particle size Is preferably smaller.
The average particle size of the granular polyvalent metal component is preferably 5 μm or less, more preferably 1 μm or less, and particularly preferably 0.1 μm or less.

  As the binder resin, a thermoplastic resin, a thermosetting resin, or the like, and a resin that is used for a paint can be preferably used. Specific examples of the binder resin include acrylic resins, urethane resins, polyester resins, epoxy resins, and vinyl resins, and polyester resins are particularly preferable.

As described above, the glass transition temperature of the binder resin is the melting point of the thermoplastic resin of each of the base material 1 and the sealant layer 5 -15 ° C. or less, and the melting point of the thermoplastic resin of each of the base material 1 and the sealant layer 5 -30 ° C. The following is preferred.
The glass transition temperature of the binder resin satisfies the above relationship between the melting points of the thermoplastic resins of the base material 1 and the sealant layer 5, and is based on the glass transition temperature of the polycarboxylic acid polymer of the first layer 2. Is preferably low. Since the second layer 3 contains a polyvalent metal component, cracks and the like are likely to occur during stretch molding. The stretchability of the second layer 3 is improved by making the glass transition temperature of the binder resin lower than the glass transition temperature of the polycarboxylic acid polymer.

  In the second layer 3, the mass ratio between the polyvalent metal component and the binder resin (polyvalent metal compound / binder resin) is preferably in the range of 35/65 to 92/8, More preferably, it is in the range of 50 to 90/10, and particularly preferably in the range of 60/40 to 90/10. If the content of the polyvalent metal component is less than the lower limit of the above range, the resulting molded article tends to have insufficient gas barrier properties. If the content of the polyvalent metal component exceeds the upper limit of the above range, molding is performed. It tends to be poor.

The second layer 3 may further contain an isocyanate compound as a curing agent.
The second layer 3 may further contain other components other than the polyvalent metal component, the binder resin, and the isocyanate compound as necessary. Examples of other components include an anti-blocking agent.

  The thickness of the second layer 3 before stretch molding of the multilayer sheet 10 is preferably 0.05 μm or more and 50 μm or less, and preferably 0.1 μm or more and 10 μm or less in terms of stretch moldability and gas barrier properties. More preferably, it is particularly preferably 0.2 μm or more and 5 μm or less. When the thickness of the second layer 3 is less than the lower limit of the above range, the gas barrier property of the obtained molded product tends to be insufficient, and when the thickness of the second layer 3 exceeds the upper limit of the above range. Formability tends to be poor.

(Sealant layer)
The sealant layer 5 is a layer provided on the surface of the gas barrier layer 4 in accordance with purposes such as imparting abrasion resistance, glossiness, imparting heat sealability, imparting strength, and moisture resistance to the multilayer sheet 10.

The sealant layer 5 includes a thermoplastic resin.
The thermoplastic resin in the sealant layer 5 can be appropriately determined in consideration of heat sealability and stretch moldability, and examples thereof include a polyester polymer, a polyamide polymer, and a polyolefin polymer. Specific examples of these polymers are the same as those mentioned for the substrate 1.
The thermoplastic resin of the sealant layer 5 is preferably a polypropylene polymer from the viewpoint of heat sealability, stretch moldability, and heat resistance.

The melting point of the thermoplastic resin of the sealant layer 5 is preferably the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C. or more, and preferably the glass transition temperature of the resin of the gas barrier layer 4 + 30 ° C. or more. When the melting point of the thermoplastic resin of the sealant layer 5 is lower than the glass transition temperature + 15 ° C. of the resin of the gas barrier layer 4, the multilayer sheet 10 is stretch-molded by heating to a temperature near the melting point of the thermoplastic resin of the sealant layer 5. Moreover, since the stretchability of the gas barrier layer 4 is poor, the gas barrier layer 4 is cracked, and the original gas barrier property may not be exhibited after molding.
When the gas barrier layer 4 is composed of a plurality of layers and the glass transition temperature of the resin of each layer is different, the melting point of the thermoplastic resin of the sealant layer 5 is the highest glass transition temperature + 15 ° C. or more among the glass transition temperatures of the resin of each layer. It is preferable that the glass transition temperature of the resin in each layer is the highest glass transition temperature + 30 ° C. or higher.

  The melting point of the thermoplastic resin of the sealant layer 5 preferably satisfies the above relationship with the glass transition temperature of the resin of the gas barrier layer 4 and is preferably 130 ° C. or higher and 200 ° C. or lower. When the melting point of the thermoplastic resin of the sealant layer 5 is less than the lower limit of the above range, when a container molded from the multilayer sheet 10 is used for retort application, the container may be deformed by heat due to retort treatment, and the upper limit of the above range is exceeded. When it exceeds, there exists a possibility that the moldability to a container may worsen.

The melting point of the thermoplastic resin of the sealant layer 5 and the melting point of the thermoplastic resin of the substrate 1 may be the same or different.
When the multilayer sheet 10 is heated at an arbitrary heating temperature and stretch-molded, the heating time until reaching the melting point of the thermoplastic resin of the sealant layer 5 varies depending on the thickness of the sealant layer 5 if the heating temperature is the same. . Specifically, the thicker the sealant layer 5, the longer the heating time. Therefore, when the thickness of the sealant layer 5 is thicker than the thickness of the base material 1, the melting point of the thermoplastic resin of the sealant layer 5 is preferably lower than the melting point of the thermoplastic resin of the base material 1.

The sealant layer 5 may be composed of a single layer or may be composed of a plurality of layers. When it is composed of a plurality of layers, the thermoplastic resin contained in each layer may be the same or different as long as the melting point thereof is the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C. or higher.
As the sealant layer 5, for example, the thermoplastic resin film can be used.
The sealant layer 5 may be stretched or unstretched.

  The thickness of the sealant layer 5 before stretch molding of the multilayer sheet 10 is appropriately determined according to the thickness of the molded product, but is preferably 1 μm or more and 2000 μm or less, more preferably 5 μm or more and 1500 μm or less. It is particularly preferably 10 μm or more and 1000 μm or less. As described above, when the multilayer sheet 10 is heated at an arbitrary heating temperature and stretch-molded, the heating time required to reach the melting point of the thermoplastic resin of the sealant layer 5 varies depending on the thickness of the sealant layer 5. When the thickness of the base material 1 is constant, if the appropriate heating time for stretching changes depending on the thickness of the sealant layer 5, the heat transferred from the base material 1 side to the gas barrier layer 4 also changes, and the stretchability of the gas barrier layer 4 changes. Will also change. When the thickness of the sealant layer 5 is not more than the above upper limit value, the gas barrier property is good. If the thickness of the sealant layer 5 is not less than the above lower limit value, there is no molding defect such as the occurrence of pinholes and the moldability is good.

(Multilayer sheet manufacturing method)
As a manufacturing method of the multilayer sheet 10, the manufacturing method which has the following processes ((alpha) 1), ((alpha) 2), and ((alpha) 3) is mentioned, for example.
(Α1) A step of forming a first layer 2 by applying a first coating liquid containing a polycarboxylic acid-based polymer and a liquid medium to one side of the substrate 1 and drying it,
(Α2) a step of coating the surface of the first layer 2 with a second coating liquid containing a polyvalent metal component, a binder resin and a liquid medium, and forming the second layer 3 by drying;
(Α3) A step of laminating the sealant layer 5 on the surface of the second layer 3.

[Step (α1)]
The liquid medium of the first coating liquid is preferably one that dissolves a polycarboxylic acid polymer, and examples thereof include water, a mixed solvent of water and an organic solvent, and the like. Water is preferable in terms of solubility and cost of the polycarboxylic acid polymer.
The first coating liquid preferably further contains a plasticizer. The preferable range of the mass ratio of the polycarboxylic acid polymer and the plasticizer in the first coating liquid is the same as the preferable range of the mass ratio of the polycarboxylic acid polymer and the plasticizer in the first layer 2. is there.
The first coating liquid may further contain other components other than the polycarboxylic acid polymer and the plasticizer. Other components are the same as the other components in the first layer 2.

The first coating liquid can be prepared by mixing each component.
An example of a method for preparing the first coating liquid will be described. First, for example, polyacrylic acid having a number average molecular weight of 200,000 is diluted with distilled water to prepare a 5% by mass aqueous solution of polyacrylic acid. Glycerol is mixed with the obtained polyacrylic acid aqueous solution so that polyacrylic acid / glycerin is 90/10 by mass ratio (solid content ratio), and the first coating liquid (polyacrylic acid / glycerin mixture). Aqueous solution) is prepared.

The coating method of the first coating liquid is not particularly limited, and for example, a gravure roll coater, a reverse roll coater, a dip coater, a die coater, a Mayer bar, a method of applying with a brush, spraying, etc. Examples thereof include a method and a method including an immersion method.
As drying conditions of the coated first coating liquid, a drying time of about 1 second to about 5 minutes is preferable at a drying temperature of 60 to 120 ° C.

[Step (α2)]
The preferable range of the mass ratio between the polyvalent metal component and the binder resin in the second coating liquid is the same as the preferable range of the mass ratio between the polyvalent metal component and the binder resin in the second layer 3.
The liquid medium of the second coating liquid is preferably one in which a polyvalent metal component is dispersed, and examples thereof include ethyl acetate, methyl ethyl ketone, and toluene.
The second coating liquid preferably further contains an isocyanate compound as a curing agent.
The second coating liquid may further contain other components other than the polyvalent metal component, the binder resin, and the isocyanate compound. Other components are the same as the other components in the second layer 3.

The second coating liquid can be prepared by mixing each component. When the second coating liquid contains an isocyanate compound, prepare a mixed dispersion of a polyvalent metal component, a binder resin and a liquid medium, and add the isocyanate compound to the mixed dispersion to prepare a second coating liquid. It is preferable to do.
An example of a method for preparing the second coating solution will be described. First, a mixed dispersion (solvent: ethyl acetate) of zinc oxide particles and polyester resin is prepared, and if necessary, 100 to 15 parts by mass of this mixed dispersion is mixed with 0 to 15 parts by mass of an isocyanate compound, A second coating solution is prepared.

It does not specifically limit as a coating method of a 2nd coating liquid, For example, the method similar to the coating method of a 1st coating liquid is mentioned.
As drying conditions of the coated second coating liquid, a drying time of about 1 second to about 5 minutes is preferable at a drying temperature of 60 to 120 ° C.

[Step (α3)]
The method for laminating the sealant layer 5 on the surface of the second layer 3 is not particularly limited, and a known method can be used as appropriate. Examples thereof include a dry laminating method, an extrusion laminating method, and a hot melt laminating method. Can be mentioned.
When laminating the sealant layer 5 on the surface of the second layer 3, an adhesive may be used as necessary. For example, the sealant layer 5 can be adhered to the surface of the second layer 3 by dry lamination using an adhesive. When an adhesive is used, an adhesive layer is formed between the second layer 3 and the sealant layer 5. Examples of the adhesive include known adhesives such as acrylic, polyester, ethylene-vinyl acetate, polyurethane, vinyl chloride-vinyl acetate, and chlorinated polypropylene.
When the second layer 3 and the sealant layer 5 are laminated via an adhesive layer, the glass transition temperature of the adhesive layer is the same as the glass transition temperature of the resin of the gas barrier layer 4. The melting point is preferably −15 ° C. or lower.

  The multilayer sheet 10 can be produced by the above method. However, the manufacturing method of the multilayer sheet 10 is not limited to the above method. For example, the second coating liquid is applied to the sealant layer 5 and dried to form the second layer 3, and the surface of the first layer 2 is applied to the surface of the second layer 3 and dried. The first layer 2 may be formed, and the substrate 1 may be laminated on the surface of the first layer 2.

(Use)
The multilayer sheet 10 is used for stretch molding. In the present specification and claims, the term “stretch molding” refers to molding that involves stretching a multilayer sheet.
The multilayer sheet 10 is formed into a molded product by stretch molding. For example, the multilayer sheet 10 is heated to a temperature equal to or higher than the glass transition temperature of the resin of the gas barrier layer 4, and the multilayer sheet 10 is stretched and molded into an arbitrary shape in this state to obtain a molded product. Such a molded article includes a multilayer sheet 10 that is at least partially stretched. Examples of molded products include molded containers and bags.

(Function and effect)
In the multilayer sheet 10, since the melting points of the thermoplastic resins of the base material 1 and the sealant layer 5 are not less than the glass transition temperature of the resin of the gas barrier layer 4 provided therebetween + 15 ° C., the base material 1 When the multilayer sheet 10 is heated to a temperature near the melting point of the thermoplastic resin of each of the sealant layers 5, the temperature of the gas barrier layer 4 becomes higher than the glass transition temperature. Therefore, molding defects and pinholes are less likely to occur when stretched after heating. Further, the gas barrier layer 4 is hardly cracked during stretching, and gas barrier properties can be exhibited even after molding.

<Second embodiment>
FIG. 2 is a top view showing a molded container 11 (molded product) according to the second embodiment of the present invention, and FIG. 3 is a sectional view of the molded container 11 taken along the line III-III. In the embodiment described below, the same reference numerals are given to the components corresponding to the previous embodiment, and the detailed description thereof is omitted.
The molded container 11 of the present embodiment includes a container body 12 that is round when viewed from above.

  The container main body 12 includes a circular bottom 12a, a peripheral wall 12b that rises from the periphery of the bottom 12a, and a flange 12c that extends substantially horizontally from the outer peripheral surface of the upper edge of the peripheral wall 12b. The peripheral wall 12b is formed in an inverted truncated cone shape whose outer diameter gradually increases toward the upper edge.

In the container main body 12, an opening is formed by the upper edge of the peripheral wall portion 12b, and a region surrounded by the bottom portion 12a and the peripheral wall portion 12b is an accommodating portion for accommodating contents.
But not the container opening with a diameter of the body 12 ^{(W 1)} particularly limited, for example, is preferably 20mm or more 300mm or less.
The depth of the accommodating portion of the container body 12 is ^{(D 1)} is not particularly limited, for example, is preferably 20mm or more than 100mm.

The container body 12 uses the multilayer sheet 10. That is, the multilayer sheet 10 is formed by stretching.
In the container body 12, the multilayer sheet 10 is arranged with the base material 1 side facing the outside of the container body 12 and the sealant layer 5 side facing the inside of the container body 12. Therefore, the upper surface of the flange portion 12 c is composed of the sealant layer 5. Thus, after the contents are accommodated in the accommodating portion, the opening portion is covered with a lid member or the like, and the opening portion can be sealed by heat sealing.

(Method for manufacturing molded container)
The molded container 11 (container body 12) can be produced by stretching the multilayer sheet 10.
As a method for producing the molded container 11, the multilayer sheet 10 is heated so as to have a glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C. or higher (hereinafter also referred to as “stretch molding temperature”) to form a container shape. A production method having a step of drawing to obtain a molded container is preferred.
If the stretch molding temperature is lower than the glass transition temperature of the resin of the gas barrier layer 4 + 15 ° C., the stretchability of the gas barrier layer 4 is poor. is there.
When the melting point of the thermoplastic resin of each of the base material 1 and the sealant layer 5 is equal to or higher than the glass transition temperature of the resin of the gas barrier layer 4 + 30 ° C., the stretch molding temperature is equal to or higher than the glass transition temperature of the resin of the gas barrier layer 4 + 30 ° C. Preferably there is.

The stretch molding temperature is preferably _Tm or the vicinity thereof.
Here, when the thicknesses of the base material 1 and the sealant layer 5 are different, T _m indicates the melting point of the thermoplastic resin having the larger thickness among the base material 1 and the sealant layer 5. When the thickness of the layer 5 is the same, the higher melting point of the melting points of the thermoplastic resins of the base material 1 and the sealant layer 5 is shown. For example, if the thickness of the sealant layer 5 is thicker than the substrate 1, the melting point of the thermoplastic resin of the sealant layer 5 is T _m.
When the melting point of the thermoplastic resin of the base material 1 is T _m and the base material 1 is composed of a plurality of layers, the thermoplasticity of each layer is such that the layer having the highest melting point is stretched. The highest melting point among the melting points of the resin is defined as _Tm .
When the melting point of the thermoplastic resin of the sealant layer 5 is _Tm and the sealant layer 5 is composed of a plurality of layers, the thermoplasticity of each layer is set so that the layer having the highest melting point is stretched. The highest melting point among the melting points of the resin is defined as _Tm .
If the stretch molding temperature is too low or too high with respect to _Tm , molding defects may occur in which the dimensions of the resulting molded container deviate from the target dimensions, or pinholes may occur in the base material 1 or the sealant layer 5 during stretching. There is.

Stretch molding is preferably performed at an area magnification of 1.5 to 20 times, more preferably performed at an area magnification of 1.5 to 15 times, and performed at an area magnification of 1.5 to 10 times. Is particularly preferred.
The area magnification indicates the ratio of the surface area of the container excluding the flange portion to the area of the opening.

As an example of the stretch molding method of the multilayer sheet 10, there is a method in which the multilayer sheet 10 is heat-softened using a vacuum molding machine and vacuum molded. Specifically, the multilayer sheet 10 is heated and softened for about 5 to 30 seconds in a heating furnace set to 400 to 500 ° C. The stretch molding temperature can be adjusted by the heating temperature and heating time at this time. Immediately after heating, the multilayer sheet 10 is placed on a mold (resin mold or metal mold) having an arbitrary shape, and air between the multilayer sheet 10 and the mold is sucked to bring the multilayer sheet 10 into close contact with the mold, Cool and mold into mold shape.
However, the stretch molding method is not limited to this. The molding machine is not limited to a vacuum molding machine, and a pressure forming machine, a melt molding machine, or the like may be used. Further, if necessary, a known molding method such as a method of molding into a mold shape that further uses a plug (straight method, drape method, air slip method, snapback method, plug assist method) or the like can be used.

  The molded container 11 (container body 12) obtained as described above can be subjected to a heat sterilization treatment. By applying heat sterilization treatment, the polyvalent metal ions in the second layer 3 are moved to the first layer 2, and ions are present between the polyvalent metal ions and the carboxy group of the polycarboxylic acid polymer. Bonds can be formed. Thereby, the outstanding gas barrier property can be expressed.

The heat sterilization treatment is a treatment that is exposed to a high-temperature and high-humidity atmosphere or hot water. Specific examples of such heat sterilization treatment include boil treatment, retort treatment, sterilization treatment used for aseptic packaged rice, and the like.
The treatment temperature for the heat sterilization treatment is preferably 80 ° C. or higher, more preferably 90 ° C. or higher.
Furthermore, when the heat sterilization treatment is a treatment in which the molded container is exposed to an atmosphere of high temperature and high humidity, the relative humidity of the atmosphere is preferably 90% or more.

The heat sterilization treatment may be performed before the contents are stored in the molded container 11, or may be performed after the contents are stored and the opening is sealed with a lid as necessary. When performing after accommodating the contents, the heat sterilization treatment can also serve as the heat sterilization treatment of the contents.
Specific examples of contents requiring heat sterilization include, for example, seasoned foods (curry, stew, etc.), cooked foods for microwave ovens (baby food, cooked rice, ladymeal, etc.), soups, desserts, pets Foods (especially wet type), processed agricultural and livestock products, and the like can be mentioned.
The molded container 11 can be suitably used as a food packaging container as mentioned in the above example.
The lid member preferably has a sealant layer on the surface (sealing surface) that contacts the molded container 11, and the sealant layer contains the same kind of thermoplastic resin as the thermoplastic resin of the sealant layer 5 of the molded container 11. . For example, if the thermoplastic resin of the sealant layer 5 of the molding container 11 is a polypropylene polymer, the thermoplastic resin of the sealant layer of the lid is also preferably a polypropylene polymer. The shape of the lid member is not particularly limited, and may be a sheet shape or a three-dimensional shape.

<Third embodiment>
FIG. 4 is a top view showing a molded container 21 (molded product) according to the third embodiment of the present invention, and FIG. 4 is a VV cross-sectional view of the molded container 21.
The molded container 21 of the present embodiment includes a container body 22 having a substantially square shape when viewed from above.

  The container body 22 extends substantially horizontally from a substantially rectangular bottom 22a with rounded corners, a peripheral wall 22b rising from the periphery of the bottom 22a, and an outer peripheral surface of the upper edge of the peripheral 22b. And a flange portion 22c. The peripheral wall portion 22b is formed in an inverted quadrangular frustum shape whose outer diameter gradually increases toward the upper edge.

In the container main body 22, an opening is formed by the upper edge of the peripheral wall portion 22 b, and a region surrounded by the bottom portion 22 a and the peripheral wall portion 22 b is a storage portion that stores the contents.
The length (W ² ) of one side of the opening of the container body 22 is not particularly limited, but is preferably 20 mm or more and 300 mm or less, for example.
The depth of the accommodating portion of the container body 22 is ^{(D 2)} is not particularly limited, for example, is preferably 20mm or more than 100mm.

The container main body 22 uses the multilayer sheet 10.
In the container body 22, the multilayer sheet 10 is disposed with the base material 1 side facing the outside of the container body 22 and the sealant layer 5 side facing the inside of the container body 22. Therefore, the upper surface of the flange portion 22 c is constituted by the sealant layer 5. Thus, after the contents are accommodated in the accommodating portion, the opening portion is covered with a lid member or the like, and the opening portion can be sealed by heat sealing.

  The molded container 21 can be manufactured in the same manner as the molded container 11 of the second embodiment except that the mold is changed.

  As described above, the multilayer sheet, the molded container, and the manufacturing method thereof of the present invention have been described by showing the first to third embodiments, but the present invention is not limited to these embodiments. Each configuration in the above embodiment, a combination thereof, and the like are examples, and the addition, omission, replacement, and other modifications of the configuration can be made without departing from the spirit of the present invention.

  For example, the gas barrier layer in the multilayer sheet of the present invention is not limited to the gas barrier layer 4 shown in the first embodiment. For example, in addition to the multilayer structure including the layer (A) and the layer (B) such as the gas barrier layer 4, a single layer or multilayer structure including a layer made of ethylene / vinyl alcohol copolymer resin (EVOH), polyvinylidene chloride It may be a single layer or a multilayer structure including the layers to be formed. In these, a multilayer structure provided with a layer (A) and a layer (B) is preferable. With such a multi-layer gas barrier layer, the polyvalent metal ions in the second layer 3 migrate to the first layer 2 by heat sterilization treatment such as retort treatment, and ion bonds with the carboxy groups of the polycarboxylic acid polymer. Excellent gas barrier properties are exhibited. Therefore, the molded container obtained is suitable for use in retort applications. Since EVOH is a polymer containing a highly hydrophilic group with high hydrophilicity in the molecule, there is a problem that when a molded container is used for retort, the gas barrier property under high humidity decreases due to hydrophilicity. is there.

  When a gas barrier layer is a multilayer structure provided with a layer (A) and a layer (B), the layer structure is layer (A) in order from the base material side like the gas barrier layer 4 shown in 1st embodiment. ) And the layer (B) are laminated (layer (A) / layer (B)). In addition to layer (A) / layer (B), layer (B) / layer (A), layer (A) / layer (B) / layer (A), layer (B) / layer (A) / layer (B Or the like.

  In the multilayer structure including the layer (A) and the layer (B), the layer (A) and the layer (B) may not be adjacent to each other. The layer (A) and the layer (A) are easy to produce an ionic bond between the carboxy group of the polycarboxylic acid polymer contained in the layer (A) and the polyvalent metal ion derived from the polyvalent metal component contained in the layer (B). It is preferable that the layer (B) contains at least one layer structural unit adjacent to the layer (B). A layer structure including at least one layer structural unit in which layer (A), layer (B), and layer (A) are adjacent or layer (B), layer (A), and layer (B) are adjacent to each other preferable.

  The multilayer sheet of the present invention may further have a gas barrier layer (hereinafter also referred to as an outer gas barrier layer) on the surface of the base material on the sealant layer side. Examples of the outer gas barrier layer are the same as those described above.

In the multilayer sheet of the present invention, the substrate and the gas barrier layer may be laminated via an adhesive layer or an anchor coat layer. Thereby, the adhesiveness between a base material and a gas barrier layer improves. Examples of the adhesive layer or anchor coat layer include those containing the same component as the resin contained in the second layer 3.
When the adhesive layer or the anchor coat layer is provided, the glass transition temperature of the adhesive layer or the anchor coat layer may be the melting point of each of the base material and the sealant layer of −15 ° C. or lower, similarly to the glass transition temperature of the resin of the gas barrier layer. preferable.

The molded product of the present invention is not limited to the molded container shown in the second and third embodiments. For example, the shape of the molded container in a top view of the container body may be a shape other than the round shape or the square shape as described above. The cross-sectional shape may be a line-symmetric shape as described above or an asymmetric shape. Further, the molded container may be a form in which two or more containers are connected in addition to a form made of a single container (container main bodies 12, 22) such as the molded containers 11 and 21. When two or more containers are connected, the shape and size of each container may be the same or different.
The molded product of the present invention may be a molded product other than a molded container. Examples of the molded product other than the molded container include bags such as pouches. A spout may be attached to the bag.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples.
In this example, DSC was performed under the following measurement conditions. All the data were values at the second cycle.

(DSC measurement conditions)
"CPP, PET"
Temperature range: 20-300 ° C,
Temperature rising rate: 10 ° C / min,
Number of cycles: 2 cycles.
"First layer"
Temperature range: 20-200 ° C.
Temperature rising rate: 10 ° C / min,
Number of cycles: 2 cycles.
"Second layer"
Temperature range: -20 to 100 ° C,
Temperature rising rate: 10 ° C / min,
Number of cycles: 2 cycles.

Example 1
4.5 parts by mass of polyacrylic acid (hereinafter abbreviated as “PAA”) as a polycarboxylic acid polymer, 0.5 parts by mass of glycerin as a plasticizer, and 95 parts by mass of distilled water as a liquid medium are mixed. A coating liquid (1-1) was prepared.
An unstretched polyethylene terephthalate film having a melting point of 205 ° C. and a thickness of 25 μm is prepared as the substrate 1, and the coating solution (1-1) is applied to the surface of the unstretched polyethylene terephthalate film with a bar coater and dried with a dryer. A first layer 2 having a thickness of about 1.0 μm was formed. At this time, the glass transition temperature of the resin of the first layer 2 was 110 ° C.

Next, 7 parts by mass of zinc oxide particles as a polyvalent metal component, 3 parts by mass of a polyester resin as a binder resin, and 90 parts by mass of ethyl acetate as a liquid medium are mixed, and polyisocyanate is added to the obtained mixed dispersion. A coating liquid (1-2) was prepared by mixing 5 parts by mass of a system curing agent.
The coating liquid (1-2) was applied to the surface of the first layer 2 with a bar coater and dried at 70 ° C. for 30 seconds with a drier to form the second layer 3 having a thickness of about 1.2 μm. At this time, the glass transition temperature of the resin of the second layer 3 was 15 ° C.

  Next, unstretched polypropylene having a melting point of 168 ° C. and a thickness of 600 μm as the sealant layer 5 is formed on the surface of the second layer 3 with a small desktop laminator manufactured by Tester Sangyo Co., Ltd. via a polyurethane adhesive. A CPP) sheet was adhered by a dry laminating method to produce a multilayer sheet. As the polyurethane-based adhesive, a two-component curable adhesive, Takelac A525 (main agent) / Takenate A52 (hardener) manufactured by Mitsui Chemicals, Inc. was used. The obtained multilayer sheet was aged at 40 ° C. for 4 days after the sealant layer 5 was bonded.

  The obtained multilayer sheet was heated and stretch-molded using a vacuum / pneumatic molding machine manufactured by Yanagishita Giken Co., Ltd., thereby producing a molded container having the configuration shown in FIGS. The set temperature in the heating furnace is set to 450 ° C., the sheet heating time is set to 15.5 seconds at which the sheet temperature is 168 ° C. which is the melting point of the CPP of the sealant layer, and the diameter of the opening of the forming container is φ78 mm. The depth was 25 mm.

(Example 2)
A coating liquid (2-1) was prepared by mixing 5 parts by weight of PAA as a polycarboxylic acid polymer and 95 parts by weight of distilled water as a liquid medium.
An unstretched polyethylene terephthalate film having a melting point of 205 ° C. and a thickness of 25 μm is prepared as the substrate 1, and the coating solution (2-1) is applied to the surface of the unstretched polyethylene terephthalate film with a bar coater and dried with a dryer. A first layer 2 having a thickness of about 1.0 μm was formed. At this time, the glass transition temperature of the resin of the first layer 2 was 125 ° C.
Thereafter, formation of the second layer 3, adhesion of the sealant layer 5 to the surface of the second layer 3, and stretching of the obtained multilayer sheet are performed in the same manner as in Example 1, so that the molded container of Example 2 is obtained. Was made.

(Example 3)
A multilayer sheet was produced in the same manner as in Example 1 except that a CPP sheet having a melting point of 168 ° C. and a thickness of 400 μm was used as the sealant layer 5.
The obtained multilayer sheet was stretched under the same conditions as in Example 1, with the sheet heating time set to 11.5 seconds at 168 ° C., which is the melting point of the CPP of the sealant layer, and the temperature set in the heating furnace and the stretch molding dimensions. The molded container of Example 3 was produced by molding.

(Comparative Example 1)
A multilayer sheet was produced in the same manner as in Example 1 except that a linear low density polyethylene (LLDPE) sheet having a melting point of 120 ° C. and a thickness of 600 μm was used as the sealant layer 5.
The obtained multilayer sheet was set to 9.0 seconds at which the sheet temperature was 120 ° C., which is the melting point of the LLDPE of the sealant layer, and the set temperature in the heating furnace and the stretch molding dimensions were the same as in Example 1. The molded container of Comparative Example 1 was produced by stretching under conditions.

(Comparative Example 2)
Using the vacuum / compressed air forming machine manufactured by Yanagishita Giken Co., Ltd. for the multilayer sheet obtained in Comparative Example 1, the sheet heating time was set to 15.5 seconds in Example 1, the heating furnace set temperature and The stretch-molded dimension was stretch-molded under the same conditions as in Example 1 to produce a molded container of Comparative Example 2.

(Evaluation 1: Stretch formability evaluation)
The molded containers obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were evaluated for the presence or absence of molding defects (whether molding according to the specified dimensions was possible) and the presence or absence of pinholes. These results are shown in Table 1.
Further, the glass transition temperature of the resin of the gas barrier layer (first layer, second layer) in Examples 1 to 3 and Comparative Examples 1 and 2, the melting point and thickness of the thermoplastic resin of each of the sealant layer and the substrate, Table 1 shows the sheet heating time and sheet temperature (set value) of the stretch molding performed in each example.

As shown in Table 1, the melting points of the thermoplastic resins of the base material and the sealant layer are not less than the glass transition temperature of the gas barrier layer resin (glass transition temperature of the resin of the first layer) + 15 ° C., and this glass transition temperature + 15 In Examples 1 to 3, which were stretch-molded at a temperature equal to or higher than ° C., molding according to the specified dimensions was possible, and no pinholes were observed.
Although the melting point of the thermoplastic resin of each of the base material and the sealant layer is lower than the glass transition temperature of the gas barrier layer resin + 15 ° C., in Comparative Example 1 stretch-molded at a temperature of the glass transition temperature + 15 ° C. or higher, as specified. No pinhole was found.
On the other hand, in Comparative Example 2 in which the melting point of the thermoplastic resin of each of the base material and the sealant layer is lower than the glass transition temperature of the resin of the gas barrier layer + 15 ° C. and stretched at the same stretch molding temperature as in Examples 1 to 3, Defects and pinholes occurred.

(Evaluation 2: Gas barrier property evaluation)
In Evaluation 1, the oxygen permeability before and after the retorting treatment of the molded containers produced in Examples 1 to 3 and Comparative Example 1 that were able to be stretch-molded without molding defects or pinholes, and the multilayer sheet before being formed into a molded container by stretch molding The oxygen permeability after the retort treatment of the (unstretched sheet) was measured, and the gas barrier properties were evaluated.
The retort process performed the retort process (shower type) for 30 minutes at the temperature of 120 degreeC using the retort processing machine (Corporation | KK Nisaka Manufacturing Co., Ltd .: RCS-600).
For the molded container, an oxygen transmission rate was measured using an oxygen permeation tester (OXTRAN 2/20, manufactured by Modern Control) with the atmosphere inside the molded container at a temperature of 23 ° C. and a relative humidity of 50%.
As for the oxygen permeability of the unstretched sheet, the oxygen permeability was measured when the atmosphere was 30 ° C. and the relative humidity was 70%.
The measured value obtained in the molded container is converted using the oxygen concentration in the atmosphere (20%) and the surface area of the molded container (0.0018 m ² ), and the oxygen concentration is 100% and the oxygen at the surface area of 1 m ² . The value of permeability [unit: cm ³ (STP) / (m ² · day · MPa)] was calculated. The results are shown in Table 2.

  As shown in Table 2, Examples 1 to 3 and Comparative Example 1 showed no significant difference in the gas barrier properties of the unstretched sheet, but a large difference was observed in the oxygen permeability of the molded container after retorting. It was. In Example 1, it is a low numerical value showing a high gas barrier property, and Examples 2 and 3 are also numerical values showing a sufficiently high gas barrier property, although they are inferior to Example 1, and originally in the container shape after stretching. The gas barrier property was exhibited. On the other hand, the molding container of Comparative Example 1 in which the melting point of the thermoplastic resin of each of the base material and the sealant layer is lower than the glass transition temperature of the gas barrier layer resin (the glass transition temperature of the resin of the first layer) + 15 ° C. has a gas barrier property. The result was greatly impaired.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... 1st layer 3 ... 2nd layer 4 ... Gas barrier layer 5 ... Sealant layer 10 ... Multilayer sheet 11 ... Molded container (molded article)
12 ... Container body 21 ... Molded container (molded product)
22 ... Container body

Claims (9)

A base material containing a thermoplastic resin, a sealant layer containing a thermoplastic resin, and a gas barrier layer containing a resin provided between the base material and the sealant layer,
A multi-layer sheet for stretch molding, wherein the thermoplastic resin of each of the base material and the sealant layer has a glass transition temperature of the resin of the gas barrier layer + 15 ° C or higher.   2. The multilayer sheet for stretch molding according to claim 1, wherein a melting point of the thermoplastic resin of the sealant layer is a glass transition temperature of the resin of the gas barrier layer + 30 ° C. or more.   The multilayer sheet for stretch molding according to claim 1 or 2, wherein a melting point of the thermoplastic resin of the base material is a glass transition temperature of the resin of the gas barrier layer + 30 ° C or higher.   The multilayer sheet for stretch molding according to any one of claims 1 to 3, wherein the thermoplastic resin of the sealant layer is a polypropylene polymer.   The said gas barrier layer is provided with the layer (A) containing a polycarboxylic acid-type polymer, and the layer (B) containing a polyvalent metal component and binder resin, It is any one of Claims 1-4. Multi-layer sheet for stretch molding.   The multilayer sheet for stretch molding according to claim 5, wherein a glass transition temperature of the binder resin of the layer (B) is lower than a glass transition temperature of the polycarboxylic acid polymer of the layer (A).   The multilayer sheet for stretch molding according to claim 5 or 6, wherein the layer (A) further contains a plasticizer.   A molded article using the multilayer sheet for stretch molding according to any one of claims 1 to 7.   A step of heating the multilayer sheet for stretch molding according to any one of claims 1 to 7 so as to have a glass transition temperature of the resin of the gas barrier layer + 15 ° C or higher and stretching to obtain a molded product. A method for producing a molded product.

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