JP6460989B2 - Thermoplastic resin sheet and its container - Google Patents

Description

  The present invention relates to a thermoplastic resin sheet and a container thereof.

  Polystyrene sheets are widely used for various packaging materials such as food containers, beverage containers, industrial containers (including various trays), and blister packs. Among these, food containers such as oil-based snack foods and dairy products need water vapor barrier properties. Styrenic resin layers are used as both outer layers, and an olefinic resin layer such as polypropylene is provided in the inside through an adhesive layer to provide water vapor barrier properties and suppress deterioration in quality due to moisture absorption of the contents and flavor. Patent Documents 1 to 4 describe multilayer resin sheets having a polyester resin layer as an inner layer in order to impart storage stability.

JP 2000-351186 A JP 2000-263729 A JP-A-11-138705 JP-A-11-58632

  In the multilayer resin sheet described above, it is necessary to provide an adhesive layer between the styrene resin layer and the water vapor barrier layer so as to be laminated. However, since the raw material for the adhesive layer is generally expensive, it is desirable not to provide an adhesive layer in order to achieve excellent versatility, and to achieve good water vapor barrier properties and interlayer adhesion with a styrene resin layer. On the other hand, a polyolefin resin is one of the highly versatile resins used for the water vapor barrier layer. However, since polyolefin resin has high toughness, multilayer sheets containing polyolefin resin are not suitable for food containers that require the ability to easily break at the notch introduction part such as a potion container (hereinafter referred to as notch cracking performance). It becomes difficult to apply.

  In order to solve this problem, the polyolefin resin layer is placed in the vicinity of the styrene resin layer near the notch forming surface of the sheet, and the notch is cut at the same time as the notch is cut, thereby ensuring the notch cracking performance. There is. However, there are various ways of entering the notch, a form in which the notch is linearly formed, and a form in which the notch is entered in a broken line form (this form has a form in which a part where the notch enters and a part where the notch does not enter coexist Etc.). When a notch is formed in a broken line shape, there is a region where the olefin-based resin layer is not completely cut off. Therefore, it is difficult to achieve good notch cracking with the above-described method. In order to solve this problem, there is a means for appropriately embrittlement of the olefin resin layer, but until now, it has been difficult to achieve both notch cracking performance, interlayer adhesion, practical strength, and water vapor barrier properties.

  The present invention has been made in view of the above circumstances, and provides a thermoplastic resin sheet having even better water vapor barrier properties while ensuring good moldability, practical strength, and sealing strength with a lid. With the goal. In addition, it can be manufactured at a lower cost than conventional multilayer sheets with a water vapor barrier resin layer disposed through an adhesive layer, and has excellent notch cracking performance that is compatible with various notch types. An object is to provide a thermoplastic resin sheet. Furthermore, it aims also at providing the container formed using the said thermoplastic resin sheet.

  That is, as a result of intensive research using various resins to solve the above problems, the present inventor used a mixed resin in which an olefin resin is dispersed and mixed in a styrene resin, and the mass of polystyrene contained in the styrene resin. When the average molecular weight is 270000 to 370000, sufficient interlayer adhesion can be achieved without interposing an adhesive layer of different types of resin, and it has excellent water vapor barrier properties and supports various notch types. The inventors have found that it is possible to obtain a thermoplastic resin sheet that realizes possible excellent notch cracking performance, and have completed the present invention.

  Therefore, according to this invention, it is a thermoplastic resin sheet containing the mixed resin layer which contains a styrene resin and an olefin resin as a resin component, Comprising: The styrene resin in the said thermoplastic resin sheet is 70-95 mass%. There is provided a thermoplastic resin sheet containing polystyrene having an olefin resin content of 30 to 5% by mass and a styrene resin of the mixed resin layer having a mass average molecular weight of 270000 to 370000.

  In the above, in a preferred embodiment, the styrene resin of the mixed resin layer further includes high impact polystyrene and a styrene thermoplastic elastomer in addition to the polystyrene. In a preferred embodiment, the styrene resin of the mixed resin layer contains 10 to 70% by mass of the polystyrene, 5 to 70% by mass of high impact polystyrene, and 1 to 10% by mass of styrene heat as a resin component. And a plastic elastomer. In a preferred embodiment, the styrenic thermoplastic elastomer is a hydrogenated product of a copolymer of styrene and butadiene, a hydrogenated product of a copolymer of styrene and isoprene, or a hydrogenated product of a copolymer of styrene, butadiene and isoprene. Or at least one selected from the group consisting of styrene-vinylisoprene copolymers. In a preferred embodiment, the olefin resin is polypropylene.

  In one embodiment of the present invention, a styrene resin layer containing a styrene resin is laminated on the mixed resin layer.

  In the above, in a preferred embodiment, the styrene resin contained in the styrene resin layer is at least one resin selected from the group consisting of polystyrene, high impact polystyrene, and styrene-butadiene copolymer.

  In one embodiment of the present invention, an intermediate layer is interposed between the mixed resin layer and the styrene resin layer, and the intermediate layer includes polystyrene, high impact polystyrene, and a styrene thermoplastic elastomer, and an olefin resin. And the olefin-based resin in the intermediate layer is 3 to 15% by mass.

  In the above, in a preferred embodiment, the ratio of the thickness of the mixed resin layer, the intermediate layer, and the styrene resin layer (mixed resin layer / intermediate layer / styrene resin layer) is 50 to 90% / 5 to 25% / 5 to 25%. It is. In a preferred embodiment, the thickness of the sheet is 0.2 mm to 3 mm.

  According to the other aspect of this invention, the shaping | molding container formed by shape | molding said thermoplastic resin sheet is provided.

  By using the thermoplastic resin sheet of the present invention, it achieves good moldability, practical strength and sealing strength with the lid material without delamination, and also supports good water vapor barrier properties and various notch types It is possible to achieve both of the excellent notch crackability possible. Moreover, since the said characteristic is implement | achieved also in the container using the thermoplastic resin multilayer sheet of this invention, it can utilize suitably for the various uses which require water vapor | steam barrier property and notch crack property.

  The thermoplastic resin sheet according to the present invention essentially includes a mixed resin layer containing a styrene resin and an olefin resin, but whether or not to include another layer, includes any layer when including another layer. Various embodiments are taken. Hereinafter, various embodiments of the thermoplastic resin sheet will be described, and then the manufacture of the thermoplastic resin sheet and the container will be described, but if the specific description of one embodiment applies to other embodiments, The description is omitted in other embodiments.

[First embodiment]
The thermoplastic resin sheet according to the first embodiment of the present invention is a single-layer thermoplastic resin sheet composed of only a mixed resin layer containing a styrene resin and an olefin resin as resin components, and the thermoplastic resin sheet A thermoplastic resin sheet containing polystyrene having a styrene resin content of 70 to 95% by mass, an olefin resin content of 30 to 5% by mass, and a styrene resin of the mixed resin layer having a mass average molecular weight of 270000 to 370000. It is.

<Mixed resin layer>
The mixed resin layer is an important layer for imparting water vapor barrier properties to the sheet, and is basically formed from a resin mixture of a styrene resin and an olefin resin. The mixed resin layer may be a single layer or a multilayer.

  Styrene resins include polystyrene, poly α-methyl styrene, polyvinyl naphthalene, polyvinyl anthracene, high impact polystyrene, styrene and acrylate copolymers, styrene and methacrylate esters, styrene and butadiene. Copolymer or hydrogenated product thereof, copolymer of styrene and isoprene or hydrogenated product thereof, copolymer of styrene, butadiene and isoprene or hydrogenated product thereof, copolymer of styrene-vinylisoprene or hydrogenated product thereof And styrene-based thermoplastic elastomers.

  Of these, polystyrene, high impact polystyrene, and styrene thermoplastic elastomer are preferable.

  Examples of the olefin resin include low density polyethylene, high density polyethylene, linear low density polyethylene, homopolypropylene, random polypropylene, poly α-olefin, terpolymer (terpolymer) and the like. Although the use is not particularly limited, it is preferable to use homopolypropylene having an excellent balance of water vapor barrier properties, molding processability, rigidity, and the like.

  The styrene resin used for the mixed resin layer of the thermoplastic resin sheet of the present invention contains polystyrene satisfying a mass average molecular weight of 270000 to 370000. If it is less than 270000, the fluidity will be too high, and the dispersibility / mixability of the olefin resin during mixing will decrease and the notch cracking property will deteriorate, which is not preferable. If it exceeds 370000, the fluidity is excessively lowered and the molding processability is deteriorated. A more preferable range is 280000-350,000.

  In the thermoplastic resin sheet of the present invention, the content ratio of the styrene resin in the entire sheet is preferably 70 to 95% by mass. If the content ratio of the styrene resin exceeds 95% by mass, the water vapor barrier property is deteriorated. If the content ratio of the styrene resin is less than 70% by mass, the notch cracking performance is deteriorated. A more preferable range of the content ratio of the styrenic resin is 75 to 92% by mass.

  In the thermoplastic resin sheet of the present invention, the content ratio of the olefin resin in the entire sheet is preferably 5 to 30% by mass. If the content ratio of the olefin resin is more than 30% by mass, the notch cracking property is deteriorated, and if the content ratio of the olefin resin is less than 5% by mass, the water vapor barrier property is deteriorated. A more preferable range of the content ratio of the olefin resin is 8 to 25% by mass.

  As a usage form of the styrenic resin used in the above-mentioned mixed resin layer, it is preferable that polystyrene, high impact polystyrene, and a thermoplastic elastomer are the main components, and more preferably 100% by mass of the styrene resin in the mixed resin layer. In this case, it is preferable to contain polystyrene, high impact polystyrene, and styrene thermoplastic elastomer while simultaneously satisfying the ranges of 10 to 70% by mass, 5 to 70% by mass, and 1 to 10% by mass, respectively. If the content ratio of the styrene-based thermoplastic elastomer is less than 1% by mass, the dispersibility of the olefin-based resin is lowered, leading to deterioration of notch cracking performance. If it exceeds 10% by mass, the sheet becomes too soft, which leads to deterioration of rigidity and notch cracking performance.

  The thermoplastic elastomer used in the thermoplastic resin sheet of the present invention is a hydrogenated styrene / butadiene copolymer or a hydrogenated styrene / isoprene copolymer for the purpose of improving the dispersibility of the olefin resin described above. And at least one selected from the group consisting of hydrogenated products of styrene, butadiene and isoprene copolymers, and styrene-vinylisoprene copolymers.

  Depending on the purpose and application of the mixed resin layer, in addition to additives such as antioxidants, ultraviolet absorbers, lubricants, etc., resin beads, silica beads, quartz beads, titanium oxide, talc, Fillers such as calcium carbonate and carbon black, pigments and the like can be added. Although the amount of addition is not particularly limited, it is preferably within 10% by mass with respect to 100% by mass of the mixed resin layer.

[Second Embodiment]
The thermoplastic resin sheet of the present invention can be used as a single-layer sheet composed only of the above-mentioned mixed resin layer. However, in order to achieve good sealing strength between the container using the sheet and the lid material. Thus, it is preferable to provide a styrene resin layer mainly composed of a styrene resin on both surfaces of the mixed resin layer.

  That is, the thermoplastic resin sheet according to the second embodiment of the present invention includes a mixed resin layer including a styrene resin and an olefin resin as resin components, and the styrene resin layer including the styrene resin is used as the mixed resin layer. A laminated thermoplastic resin sheet, wherein the styrene resin in the thermoplastic resin sheet is 70 to 95% by mass, the olefin resin is 30 to 5% by mass, and the styrene resin of the mixed resin layer It is a thermoplastic resin sheet containing polystyrene whose resin has a mass average molecular weight of 270000 to 370000.

<Styrene resin layer>
As the styrene resin used for the styrene resin layer, at least one kind of resin selected from the styrene resins that can be used for the above-mentioned mixed resin layer can be used in the same manner, and the molding processability, sheet Can be used as long as the appearance and notch cracking performance are not impaired. More preferably, it is at least one resin selected from polystyrene, high impact polystyrene, and a copolymer of styrene and butadiene, more preferably at least selected from polystyrene, high impact polystyrene, and a copolymer of styrene and butadiene. It is preferable to use after homogenizing one or more kinds of resins.

  Styrene resin layers are used in addition to antioxidants, ultraviolet absorbers, lubricants, and other additives, resin beads, silica beads, quartz beads, titanium oxide, talc, as long as practical properties are not impaired, depending on the purpose and application. Fillers such as calcium carbonate and carbon black, pigments and the like can be added. Although the amount of addition is not particularly limited, it is preferably within 10% by mass with respect to 100% by mass of the styrene resin layer.

[Third embodiment]
When a styrene resin layer mainly composed of a styrene resin is used, an intermediate layer can be provided between the mixed resin layer and the styrene resin layer for the purpose of improving interlayer adhesion with the mixed resin layer. Both the styrene resin and olefin resin used for the intermediate layer can be used in the same manner as the styrene resin and olefin resin that can be used for the mixed resin layer described above, and the moldability, sheet appearance, strength, Can be used as long as rigidity and notch cracking performance are not impaired.

  That is, the thermoplastic resin sheet according to the third embodiment of the present invention includes a mixed resin layer including a styrene resin and an olefin resin as resin components, and the styrene resin layer including the styrene resin is used as the mixed resin layer. A thermoplastic resin sheet comprising an intermediate layer including a styrene resin and an olefin resin interposed between a mixed resin layer and a styrene resin layer, wherein the styrene resin in the thermoplastic resin sheet is It is a thermoplastic resin sheet containing 70 to 95% by mass, olefinic resin is 30 to 5% by mass, and the styrene resin of the mixed resin layer is polystyrene having a mass average molecular weight of 270000 to 370000.

<Intermediate layer>
The content ratio of the olefin resin used in the intermediate layer is preferably 3 to 15% by mass with respect to 100% by mass of the intermediate layer. If it is less than 3% by mass, the interlayer adhesion between the intermediate layer and the mixed resin layer is lowered, and if it exceeds 15% by mass, the interlayer adhesion between the intermediate layer and the styrene resin layer is lowered.

In the third embodiment, the ratio of the thicknesses of the mixed resin layer, the intermediate layer, and the styrene resin layer (mixed resin layer / intermediate layer / styrene resin layer) depends on the total thickness of the sheet, but is 50 to 90% / 5 It is preferable that it is -25% / 5-25%. If the thickness of the mixed resin layer is less than 50%, water vapor barrier properties and notch cracking properties are not sufficiently obtained. If the thickness exceeds 90%, the intermediate layer and the styrene resin layer become too thin, and the sheet appearance due to melt fracture or the like. This is not preferable because it tends to cause defects. The ratio of the thickness of the mixed resin layer, the intermediate layer, and the styrene resin layer is more preferably 50 to 86% / 7 to 25% / 7 to 25%, and still more preferably 54 to 86% / 7 to 23% / 7.
~ 23%.

  In addition to additives such as antioxidants, UV absorbers, and lubricants, the intermediate layer has resin beads, silica beads, quartz beads, titanium oxide, talc, carbonic acid as long as practical properties are not impaired, depending on the purpose and application. Fillers such as calcium and carbon black, pigments and the like can be added. Although the amount of addition is not particularly limited, it is preferably within 10% by mass relative to 100% by mass of the intermediate layer.

[Thermoplastic resin sheet]
The thermoplastic resin sheet of the present invention is produced by a T-die film forming method in which a molten resin is extruded into various sheets using an extruder, an inflation film forming method (tubular method) in which a resin is extruded from an annular die, and a calender. It can be suitably manufactured by various sheet manufacturing methods such as a membrane method. Furthermore, the above-mentioned sheet can be subjected to longitudinal stretching (stretching in the production direction) and transverse stretching (stretching in the direction orthogonal to longitudinal stretching) using a roll speed difference, a tenter stretching machine, etc., as necessary. It is. The suitable thickness of the thermoplastic resin sheet of this invention is 0.2 mm-3 mm, More preferably, it is 0.2 mm-2 mm. If it is less than 0.2 mm, sufficient water vapor barrier properties and rigidity cannot be obtained, and if it exceeds 3 mm, molding processability during container molding such as vacuum molding is deteriorated, which is not preferable.

The thermoplastic resin sheet of the present invention preferably does not peel practically, and more preferably has interlaminar adhesion that does not easily peel off even if an intentional peeling operation is attempted. A preferable range of the tensile elastic modulus of the thermoplastic resin sheet of the present invention is 1400 MPa or more and less than 2000 MPa. If it is less than 1400 MPa, the rigidity is excessively reduced, and problems such as the molded container being easily crushed easily occur. When the pressure is 2000 MPa or more, the strength is excessively lowered, and problems such as the molded container being easily damaged are likely to occur. A preferable range of the tensile elongation of the thermoplastic resin sheet of the present invention is 50% or more and less than 150%. If it is less than 50%, the strength is excessively lowered, and problems such as the molded container being easily damaged are likely to occur. If it is 150% or more, the rigidity is excessively decreased, and problems such as the molded container being easily crushed are likely to occur, and the notch cracking performance is also deteriorated. A preferable range of the DuPont impact strength of the thermoplastic resin sheet of the present invention is 1.0 J or more. If it is less than 1.0 J, the impact resistance is excessively lowered, and problems such as the molded container being easily damaged are likely to occur. The preferable range of the water vapor transmission rate of the thermoplastic resin sheet of the present invention is less than 6.0 g / m ² · day, and more preferably less than 4.0 g / m ² · day. If it is 6.0 g / m ² · day or more, water vapor permeates excessively, and the moisture content of the component contained in the container using the sheet becomes remarkable, which is not preferable. A preferable range of the sealing strength of the lid material for the thermoplastic resin sheet of the present invention is 3.0N or more and less than 4.0N. If it is less than 3.0 N, it is not preferable because the sealed lid is easily peeled off from the container using the sheet. If it is 4.0 N or more, it is not preferable because the sealed lid is difficult to peel off from the container using the sheet. The notch cracking performance of the thermoplastic resin sheet of the present invention is that the sheet breaks with one folding at the notch portion when the notch is in a solid line and when the notch is in a broken line. Things are preferable.

[Molded container]
The thermoplastic resin sheet of the present invention can be formed into various containers by known thermoforming methods such as vacuum forming, pressure forming, vacuum / pressure forming, press forming, hot plate forming, and the like. The container using the thermoplastic resin sheet of the present invention can be suitably used for various containers such as food containers, beverage containers, pharmaceutical containers, and daily necessities containers.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

  The raw materials used in the examples are summarized below.

[polystyrene]
・ Toyostyrene Co., Ltd. “Toyostyrene HRM18” (mass average molecular weight: 290000)
・ Toyostyrene Co., Ltd. “Toyostyrene HRM23” (mass average molecular weight: 340000)
・ Toyostyrene Co., Ltd. “Toyostyrene G200C” (mass average molecular weight: 260000)
・ Toyostyrene Co., Ltd. “Toyostyrene HRM48N” (mass average molecular weight: 380000)
・ Toyostyrene Co., Ltd. “Toyostyrene HRM40” (mass average molecular weight: 360000)
[High impact polystyrene]
・ Toyostyrene Co., Ltd. “Toyostyrene E640N”
・ Toyostyrene Co., Ltd. "Toyostyrene H850N"
[Styrenic thermoplastic elastomer]
・ “Tuftec P2000 (hydrogenated product of styrene and butadiene copolymer)” manufactured by Asahi Kasei Chemicals Corporation
・ "TR2000 (copolymer of styrene and butadiene)" manufactured by JSR Corporation
・ Kuraray Co., Ltd. “Hibler 7350 (hydrogenated product of styrene and isoprene copolymer)”
・ Kuraray Co., Ltd. “Septon S2104 (hydrogenated product of styrene and isoprene copolymer)”

<Example 1 (Configuration of First Embodiment)>
A thermoplastic resin sheet having a mixed resin layer was obtained using a coat hanger type T die (width 550 mm) by a feed block method using a φ65 mm single screw extruder.

Here, as the mixed resin layer, a mixture of H850N, HRM23, P2000, and F107DJ in a pellet state was used.
<Example 2 (Configuration of Second Embodiment)>
Using a 65 mm single screw extruder and 40 mm single screw extruder, and using a coat block hanger type T die (width 550 mm) by a feed block method, and having a layer structure of styrene resin layer / mixed resin layer / styrene resin layer A thermoplastic resin sheet was obtained.

Here, what mixed E640N, HRM18, P2000, and F107DJ in the pellet state fully was used for the mixed resin layer, and HRM23 and E640N were used for the styrene resin layer.
<Examples 3 to 8 (Configuration of Third Embodiment)>
Using a φ65mm single screw extruder and two φ40mm single screw extruders, using a coat-hanger type T die (width 550mm) by feed block method, styrene resin layer / intermediate layer / mixed resin layer / intermediate layer / A thermoplastic resin sheet having a layer structure of a styrene resin layer was obtained. Tables 1 and 2 summarize the characteristics such as the raw material blending ratio, layer ratio, and thickness of each layer of the thermoplastic resin sheet.

  Here, the mixed resin layer is a mixture of H850N or E640N, HRM23, HRM18 or HRM40, # 7350, P2000 or S2104 and F107DJ in a pellet state, and the intermediate layer is H850N or E640N, HRM23, HRM18 or G200C, # 7350, P2000 or S2104, and F107DJ were sufficiently mixed in a pellet state, and HRM18 or G200C and H850N or E640N and 730L were used for the styrene resin layer.

<Comparative Examples 1-6>
A thermoplastic resin sheet was prepared with reference to the production method of the example. Table 3 and Table 4 summarize structural characteristics such as the raw material blending ratio, layer ratio, and thickness of each layer in each sheet.

[Measurement of mass average molecular weight]
The molecular weight of polystyrene was measured with the following GPC measuring apparatus and conditions.
Device name: High-speed GPC device HLC-8220 (manufactured by Tosoh Corporation)
Column: 3 PL gel MIXED-B in series Temperature: 40 ° C
Detection: differential refractive index solvent: tetrahydrofuran concentration: 2 wt%
Calibration curve: prepared using standard polystyrene (manufactured by PL), and the mass average molecular weight was measured in terms of polystyrene.

[Evaluation of interlayer adhesion]
The intentional peeling operation of the sheet was performed, and the superiority or inferiority was determined according to the following criteria.
Good: Does not peel easily.
Yes: The presence of a peeling interface suggesting a layer interface is recognized, but peeling does not propagate over a wide area.
Defect: Delamination extends over a wide area.

[Measurement of tensile modulus and tensile elongation]
For the tensile modulus and tensile elongation, Toyo Seiki's Strograph VE1D is used for each of the sheet production direction (hereinafter abbreviated as MD) and the direction orthogonal to the production direction (hereinafter abbreviated as TD). Then, according to JIS K7127, it was measured at a tensile speed of 5 mm / min.

[DuPont impact strength]
The DuPont impact strength was measured according to ASTM D2794, using a DuPont impact machine manufactured by Toyo Seiki Co., Ltd., using a hitting core having a tip radius of 7.9 mm.

[Measurement of water vapor transmission rate]
The water vapor transmission rate was measured under the conditions of a temperature of 40 ° C. and a humidity of 90% in accordance with JIS K7129 using an L80-5000 type water vapor transmission meter manufactured by System Instruments. The measured values were judged as superior or inferior according to the following criteria.

Good: Water vapor permeability is less than 4.0 [g / m ² · day].
Good: Water vapor transmission rate is 4.0 [g / m ² · day] or more and less than 6.0 [g / m ² · day].
Poor: Water vapor transmission rate is 6.0 [g / m ² · day] or more.

[Evaluation of sealability]
A commercially available lid material for portion milk was used, and the lid material was heat-sealed to the sheet at a seal temperature of 225 ° C. and a seal pressure (gauge pressure) of 3.6 MPa using a seal iron (steel width 1.0 mm). The sealed sample is an average when the peeling load (peeling strength) is stable by using a Strograph VE1D manufactured by Toyo Seiki Co., Ltd., in a 23 ° C. environment, at a tensile rate of 200 mm / min, and in a 180 ° direction. The value was taken as the measured value. The measured values were judged as superior or inferior according to the following criteria.

Good: The maximum peel strength is 3.0 [N] or more and less than 4.0 [N].
Defect: Out of the above “good” range

[Evaluation of notch cracking performance]
(1) A square sample piece with an MD length of 2 cm and a TD length of 2 cm is taken from the sheet, and a notch having a depth of 50% of the sheet thickness is put in a solid line on the diagonal (diagonal) of the sample piece with a cutter blade. After that, it was bent to the opposite side to the notched surface, and the notch cracking performance was judged according to the following criteria.
(2) A square sample piece having an MD length of 2 cm and a TD length of 2 cm is taken from the sheet, and a notch having a depth of 50% of the sheet thickness is put in a dotted line on the diagonal line (diagonal) of the sample piece with a cutter blade. After that, it was bent to the opposite side to the notched surface, and the notch cracking performance was judged according to the following criteria.

Good: The sample piece breaks at the notch by the first folding.
Defect: The sample piece does not break at the notch portion after the first bending.

  Tables 1 to 4 summarize the measurement results of the tensile modulus, tensile elongation, DuPont impact strength, water vapor barrier property, sealing property, and notch cracking performance of the aforementioned sheet.

  From the results of Tables 1 to 4, by using the thermoplastic resin sheet of the present invention, while having excellent strength and rigidity, good water vapor barrier properties, sealing properties with lid materials, interlayer adhesion properties, various Notch cracking performance that can also be applied to the notch type can be realized, and it can be suitably used for various containers that require water vapor barrier properties such as portion containers.

  The thermoplastic resin sheet of the present invention can be used for various packaging materials such as food containers, beverage containers, industrial containers (including various trays), and in particular, water vapor barrier properties such as oil-based snack foods and dairy products. It can be suitably used for food containers that require notch cracking properties.

Claims (9)

A thermoplastic resin sheet including a mixed resin layer containing a styrene resin and an olefin resin as resin components, wherein the styrene resin in the thermoplastic resin sheet is 70 to 95% by mass, and the olefin resin is 30. a 5% by weight, seen containing polystyrene styrene-based resin of the mixed resin layer is a weight average molecular weight from 270,000 to 370,000, formed by laminating a styrene resin layer containing a styrene-based resin in the mixed resin layer, a mixed resin An intermediate layer is interposed between the layer and the styrene resin layer, the intermediate layer further including a styrene resin including polystyrene, high impact polystyrene, and a styrene thermoplastic elastomer, and an olefin resin, and the olefin of the intermediate layer A thermoplastic resin sheet having a resin content of 3 to 15% by mass .   The thermoplastic resin sheet according to claim 1, wherein the styrene resin of the mixed resin layer further includes high impact polystyrene and a styrene thermoplastic elastomer in addition to the polystyrene.   The styrene resin of the mixed resin layer includes 10 to 70% by mass of the polystyrene, 5 to 70% by mass of high impact polystyrene, and 1 to 10% by mass of a styrene thermoplastic elastomer as a resin component. 2. The thermoplastic resin sheet according to 2.   The styrenic thermoplastic elastomer is a hydrogenated product of a copolymer of styrene and butadiene, a hydrogenated product of a copolymer of styrene and isoprene, a hydrogenated product of a copolymer of styrene, butadiene and isoprene, or a styrene-vinylisoprene. The thermoplastic resin sheet according to claim 2 or 3, wherein the thermoplastic resin sheet is at least one selected from the group consisting of copolymers.   The thermoplastic resin sheet according to any one of claims 1 to 4, wherein the olefin resin is polypropylene. Styrene resin contained in the styrene resin layer, a polystyrene, high impact polystyrene, styrene - according to any one of claims 1 to 5 is at least one or more resins selected from the group consisting of butadiene copolymer Thermoplastic resin sheet. The ratio of the thickness of the mixed resin layer / intermediate layer / styrene resin layer (mixed resin layer / intermediate layer / styrene resin layer) is 50 to 90% / 5 to 25% / 5 to 25% . The thermoplastic resin sheet according to any one of the above. The thermoplastic resin sheet according to any one of claims 1 to 7 , wherein the sheet has a thickness of 0.2 mm to 3 mm. A molded container formed by molding the thermoplastic resin sheet according to any one of claims 1 to 8 .