JP2015009371A - Thermoplastic resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic resin sheet capable of enhancing tensile properties and suppressing necking.SOLUTION: There is provided a thermoplastic resin sheet 1 which comprises a plurality of polyolefin resin layers 11 and a plurality of ethylene-vinyl acetate copolymer resin layers 12. The polyolefin resin layers 11 are a polyolefin resin layer or a polypropylene resin layer. More than 40 layers of the plurality of polyolefin resin layers 11 and the plurality of ethylene-vinyl acetate copolymer resin layers 12 in total are laminated in the thickness direction.

Description

  The present invention relates to a thermoplastic resin sheet in which a plurality of thermoplastic resin layers are laminated.

  Thermoplastic resin sheets are used in various applications such as agricultural films and food packaging materials. In such an application, a plurality of thermoplastic resin layers may be laminated to form a thermoplastic resin sheet. A thermoplastic resin sheet in which a plurality of thermoplastic resin layers are laminated is disclosed in Patent Document 1 below.

  In the following Patent Document 1, four or more resin layers formed of a resin composition containing an ethylene-vinyl alcohol copolymer are laminated.

  In Patent Document 2 below, two or more types of layers having different Young's moduli are laminated. In Examples 1 and 2 of Patent Document 2, a thermoplastic resin sheet in which two layers A and B are laminated in a laminated structure of A / B / A is described as a multilayer interlayer film for laminated glass.

WO2011 / 125739A1 JP 2003-192402 A

  Agricultural films and food packaging materials are required to have high tensile properties. However, the thermoplastic resin sheet described in Patent Document 1 or 2 may have relatively low tensile properties. Further, necking may occur when a tensile stress is applied to the thermoplastic resin sheet.

  In recent years, from the viewpoint of reducing carbon dioxide emission, thermoplastic resin sheets used for various applications have been required to be thin while maintaining high tensile properties.

  An object of the present invention is to provide a thermoplastic resin sheet that can enhance tensile properties and suppress necking.

  According to a wide aspect of the present invention, it comprises a plurality of polyolefin resin layers and a plurality of ethylene-vinyl acetate copolymer resin layers, wherein the polyolefin resin layer is a polyethylene resin layer or a polypropylene resin layer, There is provided a thermoplastic resin sheet in which a polyolefin resin layer and a plurality of the ethylene-vinyl acetate copolymer resin layers in total are laminated in a thickness direction of 40 layers or more.

  In a specific aspect of the thermoplastic resin sheet according to the present invention, a plurality of the polyolefin resin layers and a plurality of the ethylene-vinyl acetate copolymer resin layers are alternately stacked in the thickness direction.

  In a specific aspect of the thermoplastic resin sheet according to the present invention, a ratio of 5% modulus at 23 ° C. of the polyolefin resin layer to 5% modulus at 23 ° C. of the ethylene-vinyl acetate copolymer resin layer is 3 or more.

  In a specific aspect of the thermoplastic resin sheet according to the present invention, the total content of the polyolefin resin layer is 50% by mass in 100% by mass of the total of the polyolefin resin layer and the ethylene-vinyl acetate copolymer resin layer. % To 80% by mass, and the total content of the ethylene-vinyl acetate copolymer resin layer is 20% to 50% by mass.

  In a specific aspect of the thermoplastic resin sheet according to the present invention, the polyolefin resin layer has six or more layers, and the ethylene-vinyl acetate copolymer resin layer has six or more layers.

  The thermoplastic resin sheet according to the present invention comprises a plurality of polyolefin resin layers and a plurality of ethylene-vinyl acetate copolymer resin layers, wherein the polyolefin resin layer is a polyethylene resin layer or a polypropylene resin layer, Since the polyolefin resin layer and the plurality of ethylene-vinyl acetate copolymer resin layers are laminated in a thickness direction of 40 or more layers, tensile properties can be enhanced and necking can be suppressed.

FIG. 1 is a cross-sectional view schematically showing a thermoplastic resin sheet according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a thermoplastic resin sheet according to the second embodiment of the present invention. FIG. 3 is a diagram showing stress strain curves (relationship between elongation (%) and stress (MPa)) of the thermoplastic resin sheets of Example 3, Comparative Example 1 and Comparative Example 2. FIG. 4 is a diagram showing stress-strain curves (relationship between elongation (%) and stress (MPa)) of the thermoplastic resin sheets of Example 8, Comparative Example 6, and Comparative Example 2. FIG. 5 is a diagram showing the shape of a No. 5 type test piece used for evaluation of the tensile test.

  Details of the present invention will be described below.

  The thermoplastic resin sheet according to the present invention is described as a plurality of polyolefin resin layers (hereinafter sometimes referred to as PO resin layers) and a plurality of ethylene-vinyl acetate copolymer resin layers (hereinafter referred to as EVA resin layers). May be included). In the thermoplastic resin sheet according to the present invention, the PO resin layer is a polyethylene resin layer (hereinafter sometimes referred to as a PE resin layer) or a polypropylene resin layer (hereinafter sometimes referred to as a PP resin layer). is there. In the thermoplastic resin sheet according to the present invention, the plurality of PO resin layers and the plurality of EVA resin layers are laminated in a thickness direction of 40 layers or more in total.

  Since the thermoplastic resin sheet according to the present invention has the above-described configuration, the tensile properties can be enhanced and necking can be suppressed. In particular, necking in a low temperature region of 30 ° C. or lower can be effectively suppressed.

  When the thermoplastic resin sheet has the same thickness, a total of 40 or more PO resin layers and EVA resin layers, which are PE resin layers or PP resin layers, are laminated with less than 40 layers. Compared with this, tensile properties can be improved and necking can be suppressed. Also, by laminating 40 or more PO resin layers and EVA resin layers that are PE resin layers or PP resin layers, compared to the case where only PE resin layers or PP resin layers are laminated in the same number of layers, necking can be performed. Can be suppressed. Furthermore, by laminating 40 or more layers of PE resin layers or PP resin layers and EVA resin layers, tensile properties can be enhanced as compared with the case where only EVA resin layers are laminated in the same number of layers.

  The material of the PO resin layer is a polyolefin resin. The material of the PE resin layer is a polyethylene resin. The material of the PP resin layer is a polypropylene resin. The material of the EVA resin layer is an ethylene-vinyl acetate copolymer resin.

  Examples of the polyethylene resin include homopolyethylene and copolymers of ethylene and other monomers (such as α-olefin). In the case of a copolymer of ethylene and another monomer, ethylene is used as a main component. For example, 50% by mass or more of ethylene is used in a total of 100% by mass of monomers for obtaining an ethylene-α-olefin copolymer. Preferably, 80 mass% or more is used. As for the said polyethylene resin, only 1 type may be used and 2 or more types may be used together.

  Examples of the polypropylene resin include homopolypropylene and copolymers of propylene and other monomers (such as α-olefin). In the case of a copolymer of propylene and another monomer, propylene is used as a main component. For example, propylene is used in an amount of 50% by mass or more in a total of 100% by mass of monomers for obtaining a propylene-α-olefin copolymer. Preferably, 80 mass% or more is used. As for the said polypropylene resin, only 1 type may be used and 2 or more types may be used together.

  The α-olefin is not particularly limited, and examples thereof include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene.

  The ethylene-vinyl acetate copolymer resin may be a non-crosslinked ethylene-vinyl acetate copolymer resin or a crosslinked ethylene-vinyl acetate copolymer resin. The ethylene-vinyl acetate copolymer resin includes ethylene-vinyl acetate modified resins such as saponified ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer resin is obtained by a known method.

  The vinyl acetate content of the ethylene-vinyl acetate copolymer resin is preferably 2% by mass or more, more preferably 10% by mass or more, preferably 50% by mass or less, more preferably 35% by mass or less. If the vinyl acetate content is not less than the above lower limit and not more than the above upper limit, the necking prevention effect is further improved. From the viewpoint of further improving the transparency of the thermoplastic resin sheet, the vinyl acetate content is preferably more than 28% by mass. The vinyl acetate content is measured according to JIS K 6730 “Testing method for ethylene / vinyl acetate resin”.

  From the viewpoint of further enhancing the tensile properties and further suppressing necking, the total content of the PO resin layer is preferably 40% by mass or more in the total 100% by mass of the PO resin layer and the EVA resin layer. More preferably, it is 50 mass% or more, More preferably, it is 60 mass% or more, Preferably it is 90 mass% or less, More preferably, it is 80 mass% or less, More preferably, it is 70 mass% or less. A method for adjusting the entire content of the PO resin layer in 100% by mass of the total of the PO resin layer and the EVA resin layer is not particularly limited, and examples thereof include the following methods. When the total content of the PO resin layer is increased, a larger amount of the composition for forming the PO resin layer is supplied to the composition for forming the EVA resin layer during the production of the thermoplastic resin sheet. A method of increasing the average thickness of the PO resin layer relative to the average thickness of the EVA resin layer, and a method of increasing the number of stacked PO resin layers relative to the number of stacked EVA resin layers. . On the other hand, when the total content of the PO resin layer is decreased, the composition for forming the PO resin layer is supplied to the composition for forming the EVA resin layer in a smaller amount. The average thickness of the PO resin layer may be made thinner than the average thickness of the EVA resin layer, or the number of stacked PO resin layers may be decreased with respect to the number of stacked EVA resin layers.

  From the viewpoint of further enhancing the tensile properties and further suppressing necking, the total content of the PO resin layer is preferably 50% by mass or more, preferably 90% by mass, out of the total 100% by mass of the thermoplastic resin sheet. It is as follows.

  From the viewpoint of further enhancing the tensile properties and further suppressing necking, the total content of the EVA resin layer is preferably 10% by mass or more in the total of 100% by mass of the PO resin layer and the EVA resin layer. More preferably, it is 20 mass% or more, More preferably, it is 30 mass% or more, Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less. The method for adjusting the total content of the EVA resin layer in 100% by mass of the total of the PO resin layer and the EVA resin layer is not particularly limited, and examples thereof include the following methods. When the total content of the EVA resin layer is increased, a larger amount of the composition for forming the EVA resin layer is supplied to the composition for forming the PO resin layer at the time of manufacturing the thermoplastic resin sheet. A method of increasing the average thickness of the EVA resin layer relative to the average thickness of the PO resin layer, and a method of increasing the number of stacked EVA resin layers relative to the number of stacked PO resin layers. . On the other hand, when the total content of the EVA resin layer is reduced, the composition for forming the EVA resin layer is supplied to the composition for forming the PO resin layer in a smaller amount. The average thickness of the EVA resin layer may be made thinner than the average thickness of the PO resin layer, or the number of stacked EVA resin layers may be decreased with respect to the number of stacked PO resin layers. From the viewpoint of further enhancing the tensile properties and further suppressing necking, the total content of the EVA resin layer is preferably 10% by mass or more, preferably 50% by mass, out of the total 100% by mass of the thermoplastic resin sheet. It is as follows.

  From the viewpoint of further enhancing tensile properties and further suppressing necking, the 5% modulus (EVA) at 23 ° C. of the EVA resin layer is preferably 1 MPa or more, more preferably 25 MPa or more, and preferably 50 MPa or less. . The 5% modulus (EVA) at 23 ° C. of the EVA resin layer can be increased by decreasing the vinyl acetate content of the ethylene-vinyl acetate copolymer resin used, and can be decreased by increasing the vinyl acetate content. . The 5% modulus (EVA) can be adjusted by changing the vinyl acetate content of the ethylene-vinyl acetate copolymer resin used. Specifically, the 5% modulus can be increased by decreasing the vinyl acetate content, and the 5% modulus can be decreased by increasing the vinyl acetate content.

  From the viewpoint of further enhancing the tensile properties and further suppressing necking, the ratio of 5% modulus (PO) at 23 ° C. of the PO resin layer to 5% modulus (EVA) at 23 ° C. of the EVA resin layer. (5% modulus (PO) / 5% modulus (EVA)) is preferably 1 or more, more preferably 3 or more, and preferably 20 or less. The 5% modulus (PO) can be adjusted by changing the crystallinity or density of the polyolefin used. Specifically, the 5% modulus can be increased by increasing the crystallinity, and the 5% modulus can be decreased by decreasing the crystallinity.

  Although 5% modulus is not specifically limited, For example, it measures by the following method. First, a thermoplastic resin sheet is cut out using a dumbbell cutter, and a No. 5 type test piece having the shape shown in FIG. 5 is prepared. The No. 5 type test piece has a marked line width of 6 mm and a distance between marked lines of 33 mm. Based on JIS K7127: 1999, the tensile test of the said test piece is performed on the conditions of a tensile speed of 500 mm / min and 23 degreeC using "Tensilon RTG-1310" by A & D as a tensile tester. As a result of the tensile test, 5% modulus is converted from the tensile stress when the measured strain is 5% according to JIS K7161: 1994.

  The average thickness of the PO resin layer and the average thickness of the EVA resin layer are each preferably 15 μm or less. The average thickness of the PO resin layer is the average thickness of all the PO resin layers included in the thermoplastic resin sheet. For example, when the thicknesses of all five PO resin layers included in the thermoplastic resin sheet are 4.8 μm, 5 μm, 5 μm, 5 μm, and 5 μm, the average thickness of the PO resin layer is 4.95 μm. . The average thickness of the EVA resin layer is an average of the thicknesses of the plurality of EVA resin layers included in the thermoplastic resin sheet. The average thickness can be measured, for example, by the following method. The obtained thermoplastic resin sheet is cut in the thickness direction with a size of 1 cm in length and 1 cm in width with an ultramicrotome (“EM-ULTRACUT · S” manufactured by Leica) to obtain a cross section of the thermoplastic resin sheet. The center part in the width direction of the cross section of the thermoplastic resin sheet is observed in a range of 20 μm × 20 μm using a digital microscope (“VHX-200” manufactured by Keyence Corporation). By moving the visual field in the thickness direction, images of all layers are taken, and an enlarged image of the cross section is obtained. From the enlarged image of the cross section, the thickness of the central portion in the width direction of each layer is measured using the measurement function attached to the digital microscope. The average value of the thickness of the center part in the width direction of each layer of the obtained PO resin layer is obtained, and is defined as the average thickness of the PO resin layer in the thermoplastic resin sheet. The average value of the thickness of the center part of the width direction of each layer (20 layers) of the obtained EVA resin layer is calculated | required, and it is set as the average thickness of the EVA resin layer in a thermoplastic resin sheet.

  The thermoplastic resin sheet according to the present invention may be a laminate having only the PO resin layer and the EVA resin layer, a laminate of the PO resin layer and the EVA resin layer, Other layers laminated on the outer surface may be included.

  In the thermoplastic resin sheet according to the present invention, it is preferable that a total of 160 or more layers of the PO resin layer and the EVA resin layer are laminated. In this case, the tensile properties of the thermoplastic resin sheet are further enhanced, and necking is further suppressed. When the total thickness of the PO resin layer and the EVA resin layer is 160 or more when the thickness of the thermoplastic resin sheet is the same, the PO resin layer and the EVA resin layer Compared with the case where the total number of laminated layers is 159 layers or less, the tensile properties of the thermoplastic resin sheet are further enhanced, and necking is further suppressed. In the thermoplastic resin sheet according to the present invention, it is more preferable that the PO resin layer and the EVA resin layer are laminated in a total of 320 layers or more.

  The upper limit of the total number of laminated layers of the PO resin layer and the EVA resin layer is not particularly limited. Since the transparency of the thermoplastic resin sheet is further improved, the total number of laminated layers of the PO resin layer and the EVA resin layer is preferably 20000 layers or less, more preferably 5000 layers or less, and even more preferably 1000 layers. It is as follows.

  The number of laminations of the PO resin layer in the thermoplastic resin sheet and the number of laminations of the EVA resin layer in the thermoplastic resin sheet are each preferably 5 or more, more preferably 10 or more, still more preferably 20 or more, Particularly preferred is 80 layers or more, and most preferred is 160 layers or more. The upper limit of the number of laminations of the PO resin layer and the upper limit of the number of laminations of the EVA resin layer can be appropriately changed in consideration of the thickness of the thermoplastic resin sheet, and are not particularly limited. The number of laminations of the PO resin layer in the thermoplastic resin sheet and the number of laminations of the EVA resin layer in the thermoplastic resin sheet are each preferably 10,000 layers or less, more preferably 2500 layers or less, and even more preferably 500 layers or less. is there. The thermoplastic resin sheet preferably has 6 or more PO resin layers and 6 or more EVA resin layers.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  In FIG. 1, the thermoplastic resin sheet which concerns on the 1st Embodiment of this invention is typically shown with sectional drawing.

  A thermoplastic resin sheet 1 shown in FIG. 1 includes a plurality of PO resin layers 11 (polyolefin resin layer, first layer) and a plurality of EVA resin layers 12 (ethylene-vinyl acetate copolymer resin layer, second layer). Is a laminate 2 in which and are laminated. The laminate 2 is configured by laminating a plurality of PO resin layers 11 and a plurality of EVA resin layers 12 in total at least 40 layers. Specifically, the laminate 2 is configured by laminating about 20 PO resin layers 11 and about 20 EVA resin layers 12.

  For convenience of illustration, the total number of laminated layers of the PO resin layer 11 and the EVA resin layer 12 is about 40 layers. For example, the total number of laminated layers of the PO resin layer 11 and the EVA resin layer 12 is 160 layers or more. It may be. The PO resin layer 11 and the EVA resin layer 12 are laminated in the thickness direction of the thermoplastic resin sheet 1 and the laminate 2. The composition of the plurality of PO resin layers 11 may be the same or different. The compositions of the plurality of PO resin layers 11 are preferably the same. The composition of the plurality of EVA resin layers 12 may be the same or different. The composition of the plurality of EVA resin layers 12 is preferably the same.

  In the thermoplastic resin sheet 1, the PO resin layers 11 and the EVA resin layers 12 are alternately laminated in the thickness direction. The thermoplastic resin sheet 1 has a portion in which a PO resin layer 11 is sandwiched between EVA resin layers 12. The thermoplastic resin sheet 1 has a portion in which an EVA resin layer 12 is sandwiched between PO resin layers 11. From the viewpoint of further enhancing the tensile properties and further suppressing necking, it is preferable that the PO resin layer and the EVA resin layer are alternately laminated in the thickness direction. However, the PO resin layer and the EVA resin layer may be randomly stacked in the thickness direction. Further, the thermoplastic resin sheet may have, for example, a partially laminated structure of ... / PO resin layer / EVA resin layer / PO resin layer / EVA resin layer /.../ PO resin layer / PO resin layer. It may have a partial laminated structure of / EVA resin layer / ... or a partial laminated structure of ... / EVA resin layer / EVA resin layer / PO resin layer /.

  The thicknesses of the plurality of PO resin layers 11 are the same. The thicknesses of the plurality of PO resin layers may be the same or different. The plurality of EVA resin layers 12 have the same thickness. The thickness of the plurality of EVA resin layers may be the same or different. The PO resin layer 11 and the EVA resin layer 12 have different thicknesses. The thickness of the PO resin layer 11 is thinner than the thickness of the EVA resin layer 12. The thickness of the PO resin layer and the thickness of the EVA resin layer may be the same or different.

  In FIG. 2, the thermoplastic resin sheet which concerns on the 2nd Embodiment of this invention is typically shown with sectional drawing.

  A thermoplastic resin sheet 41 shown in FIG. 2 is formed on the laminate 2 shown in FIG. 1, the third layer 42 laminated on the first surface 2 a of the laminate 2, and the second surface 2 b of the laminate 2. And a stacked fourth layer 43. Each of the third layer 42 and the fourth layer 43 is a surface layer. The composition of the third layer 42 and the fourth layer 43 may be the same or different. One third layer 42 may be stacked only on the first surface 2a of the stacked body 2, and the fourth layer 43 may not be stacked on the second surface 2b. The two layers of the third layer 42 and the fourth layer 43 are preferably laminated one by one on the first surface 2a and the second surface 2b of the laminate 2.

  From the viewpoint of easily producing a thermoplastic resin sheet, from the viewpoint of further enhancing tensile properties and further suppressing necking, the average thicknesses of the PO resin layer and the EVA resin layer are each preferably 5 nm or more, more preferably It is 50 nm or more, preferably 6.0 μm or less, more preferably 4.8 μm or less, still more preferably 1.5 μm or less, and most preferably 1.0 μm or less. The thickness of the thinnest first layer is preferably 5 nm or more, more preferably 50 nm or more. The thickness of the thickest first layer is preferably 6.0 μm or less, more preferably 4.8 μm or less.

  The total thickness of the PO resin layer and the EVA resin layer (thickness of the laminate) is preferably 50 μm or more, more preferably 240 μm or more, still more preferably 320 μm or more, preferably 3000 μm or less, more preferably 1500 μm or less. is there. When the total thickness of the PO resin layer and the EVA resin layer is not less than the above lower limit, the tensile properties are further enhanced, and necking is further suppressed. When the total thickness of the PO resin layer and the EVA resin layer is not more than the above upper limit, the transparency of the thermoplastic resin sheet is further enhanced.

  The thickness of the thermoplastic resin sheet is preferably 50 μm or more, more preferably 250 μm or more, preferably 3000 μm or less, more preferably 1500 μm or less. When the thickness of the thermoplastic resin sheet is not less than the above lower limit, the tensile properties are further enhanced and necking is further suppressed. When the thickness of the thermoplastic resin sheet is not more than the above upper limit, the transparency of the thermoplastic resin sheet is further increased.

  The PO resin layer, the EVA resin layer, the third layer, and the fourth layer may each include an ultraviolet absorber, an antioxidant, a light stabilizer, a flame retardant, an antistatic agent, a pigment, Additives such as dyes, moisture-proofing agents, optical brighteners and infrared absorbers may be included.

(Method for producing thermoplastic resin sheet)
The method for producing the thermoplastic resin sheet according to the present invention is not particularly limited. Examples of the method for producing a thermoplastic resin sheet according to the present invention include a wet lamination method, a dry lamination method, an extrusion coating method, a multilayer melt extrusion method, a hot melt lamination method, and a heat lamination method.

  The thermoplastic resin sheet according to the present invention is obtained by a multilayer melt extrusion molding method because a thermoplastic resin sheet that is easier to manufacture and has higher tensile properties and is less prone to necking is obtained. Is preferred. Examples of the multilayer melt extrusion method include a multi-manifold method and a feed block method.

  From the viewpoint of easily producing a thermoplastic resin sheet, and from the viewpoint of further enhancing tensile properties and further suppressing necking, the method for producing a thermoplastic resin sheet according to the present invention includes the PO resin layer and the EVA resin layer. It is preferable to provide the process of shape | molding a laminated body with these by the multilayer melt extrusion molding method. From the viewpoint of easily producing a thermoplastic resin sheet, and from the viewpoint of further improving tensile properties and further suppressing necking, it is preferable to form the laminate by a multi-manifold method or a feed block method. Further, in the method for producing a thermoplastic resin sheet according to the present invention, the third layer is laminated only on the first surface of the laminate, or the third layer and the fourth layer are combined. It is preferable to include a step of laminating one layer at a time on the first surface of the laminate and a second surface opposite to the first surface.

  In addition, the thermoplastic resin sheet according to the present invention can be used as a packaging material, an agricultural film, and the like. Examples of the packaging material include food packaging materials.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

Example 1
In order to form a PO resin layer, a polyethylene resin (“Novatech LD YF30” manufactured by Nippon Polyethylene Co., Ltd., density 0.920 g / cm ³ ) was supplied to the main extruder. Moreover, in order to form an EVA resin layer, an ethylene-vinyl acetate copolymer resin (“Evaflex EV460” manufactured by Mitsui DuPont Chemical Co., vinyl acetate content 19% by mass) was supplied to the sub-extruder. A multi-layer feed block was attached to the tip of the main extruder and the sub-extruder. Of the total amount of extrusion of the PO resin layer and EVA resin layer per unit time (hereinafter sometimes referred to as extrusion amount) of 100% by mass, the extrusion amount of the PO resin layer is 70% by mass, A thermoplastic resin having a thickness of 800 μm is formed by setting the extrusion amount to 30% by mass and alternately laminating a total of 40 layers of PO resin layers extruded from the main extruder and EVA resin layers extruded from the sub-extruder. A sheet was obtained. In the total 100% by mass of the obtained thermoplastic resin sheet (in the total 100% by mass of the PO resin layer and the EVA resin layer), the content of the PO resin layer is 70% by mass, and the content of the EVA resin layer is 30% by mass. It was the same ratio as the extrusion amount of the PO resin layer and the extrusion amount of the EVA resin layer.

(Examples 2 to 5)
The extrusion amount of the PO resin layer and the EVA resin layer in the total 100 mass% of the thickness of the thermoplastic resin sheet, the number of laminations of the PO resin layer, the number of laminations of the EVA resin layer, and the extrusion amount of the PO resin layer and the EVA resin layer A thermoplastic resin sheet was obtained in the same manner as in Example 1 except that the extrusion amount was set as shown in Table 1 below. Further, in the total 100% by mass of the obtained thermoplastic resin sheet (in the total 100% by mass of the PO resin layer and the EVA resin layer), the content of the PO resin layer and the content of the EVA resin layer are the PO resin layer. The amount of extrusion was the same as the amount of extrusion of the EVA resin layer.

(Comparative Example 1)
In order to form the PO resin layer in the extruder, a polyethylene resin (“Novatech LD YF30” manufactured by Nippon Polyethylene Co., Ltd.) was supplied to obtain a single-layer thermoplastic resin sheet having a thickness of 800 μm.

(Comparative Example 2)
In order to form an EVA resin layer in an extruder, an ethylene-vinyl acetate copolymer resin (“Evaflex EV460” manufactured by Mitsui DuPont Chemical Co., Ltd.) is supplied, and a single-layer thermoplastic resin sheet having a thickness of 800 μm is obtained. Obtained.

(Comparative Examples 3-5)
The extrusion amount of the PO resin layer and the EVA resin layer in the total 100 mass% of the thickness of the thermoplastic resin sheet, the number of laminations of the PO resin layer, the number of laminations of the EVA resin layer, and the extrusion amount of the PO resin layer and the EVA resin layer A thermoplastic resin sheet was obtained in the same manner as in Example 1 except that the extrusion amount was set as shown in Table 1 below. Further, in the total 100% by mass of the obtained thermoplastic resin sheet (in the total 100% by mass of the PO resin layer and the EVA resin layer), the content of the PO resin layer and the content of the EVA resin layer are the PO resin layer. The amount of extrusion was the same as the amount of extrusion of the EVA resin layer.

(Examples 6 to 10)
The material of the PO resin layer supplied to the main extruder was changed to a polyethylene resin (“Novatec LD LE520H” manufactured by Nippon Polyethylene Co., Ltd., density 0.923 g / cm ³ ), the thickness of the thermoplastic resin sheet, the PO resin layer Table 2 below shows the amount of extrusion of the PO resin layer and the amount of extrusion of the EVA resin layer in the total of 100% by mass of the number of laminations, the number of EVA resin layers, and the amount of extrusion of the PO resin layer and the EVA resin layer. A thermoplastic resin sheet was obtained in the same manner as in Example 1 except that the settings were made as shown. Further, in the total 100% by mass of the obtained thermoplastic resin sheet (in the total 100% by mass of the PO resin layer and the EVA resin layer), the content of the PO resin layer and the content of the EVA resin layer are the PO resin layer. The amount of extrusion was the same as the amount of extrusion of the EVA resin layer.

(Comparative Example 6)
In order to form a PO resin layer in the extruder, a polyethylene resin (“Novatech LD LE520H” manufactured by Nippon Polyethylene Co., Ltd.) was supplied to obtain a single-layer thermoplastic resin sheet having a thickness of 800 μm.

(Comparative Examples 7-9)
The material of the PO resin layer supplied to the main extruder was changed to polyethylene resin ("Novatech LD LE520H" manufactured by Nippon Polyethylene Co., Ltd.), and the thickness of the thermoplastic resin sheet, the number of laminated PO resin layers, the EVA resin layer Except that the number of laminations, the extrusion amount of the PO resin layer and the extrusion amount of the EVA resin layer in the total 100 mass% of the extrusion amount of the PO resin layer and the EVA resin layer were set as shown in Table 2 below. A thermoplastic resin sheet was obtained in the same manner as in Example 1. Further, in the total 100% by mass of the obtained thermoplastic resin sheet (in the total 100% by mass of the PO resin layer and the EVA resin layer), the content of the PO resin layer and the content of the EVA resin layer are the PO resin layer. The amount of extrusion was the same as the amount of extrusion of the EVA resin layer.

(Evaluation)
(1) Tensile test 5% modulus was evaluated as an evaluation item of tensile properties. A thermoplastic resin sheet obtained using a dumbbell cutter was cut out to prepare a No. 5 test piece having the shape shown in FIG. The No. 5 type test piece has a marked line width of 6 mm and a distance between marked lines of 33 mm. Based on JIS K7127: 1999, the tensile test of the said test piece was done on conditions of a tensile speed of 500 mm / min and 23 degreeC using "Tensilon RTG-1310" by A & D as a tensile tester. As a result of the tensile test, 5% modulus was converted from the tensile stress at the time when the measured strain was 5% according to JIS K7161: 1994.

  In addition, by evaluating the test pieces of the thermoplastic resin sheets obtained in Comparative Examples 1, 2, and 6, the 5% modulus of the PO resin layer and the 5% modulus of the EVA resin layer in the examples were measured.

(2) Necking test The stress strain curve with respect to the test piece of a thermoplastic resin sheet was investigated by said (1) tensile test, and the amount of necking with respect to the test piece was calculated | required. The stress value (S1) at the initial maximum stress point and the subsequent stress value (S2) at the minimum stress were recorded to determine the necking (%). Necking (%) was defined as the formula: 100 × (S1-S2) / S1, and the necking test was judged and evaluated according to the following criteria.

[Necking test criteria]
○: Necking (%) is less than 3% ×: Necking (%) is 3% or more

(3) Transparency Using a haze meter (“TC-HIII PDK” manufactured by Tokyo Denshoku Co., Ltd.), the haze value of the obtained thermoplastic resin sheet is measured according to JIS K7105: 1999, and the transparency is measured. Judgment was made according to the following criteria. In applications where transparency is required, or from the viewpoint of improving the appearance, the haze is preferably 50% or less, more preferably 10% or less.

[Transparency criteria]
A: Transparent (thickness 800 μm: haze 50% or less)
B: Opaque (thickness 800 μm: haze exceeds 50%)
Details and evaluation results of Examples and Comparative Examples are shown in Tables 1 and 2 below. In Tables 1 and 2 below, “YF30” indicates “Novatech LD YF30” manufactured by Nippon Polyethylene, “EV460” indicates “Evaflex EV460” manufactured by Mitsui DuPont Chemical, and “LE520H” indicates polyethylene. Resin ("Novatec LD LE520H" manufactured by Nippon Polyethylene Co., Ltd.) is shown. Further, the 5% modulus ratio is a ratio of 5% modulus (PO) of the PO resin layer at 23 ° C. to 5% modulus (EVA) of the EVA resin layer at 23 ° C. (5% modulus (PO) / 5% modulus (EVA)). The 5% modulus indicates the 5% modulus at 23 ° C. of the thermoplastic resin sheet.

  FIG. 3 shows the stress strain curves (relationship between elongation (%) and stress (MPa)) of the thermoplastic resin sheets of Example 3, Comparative Example 1 and Comparative Example 2. In the thermoplastic resin sheet of Example 3, necking was suppressed after the yield point, and it was a stress-strain curve without flat portions and irregularities. The thermoplastic resin sheet of Comparative Example 1 yielded a stress-strain curve that yielded at around 8 MPa and had flat portions and uneven portions by necking up to a strain of 350%.

  FIG. 4 shows stress strain curves (relationship between elongation (%) and stress (MPa)) of the thermoplastic resin sheets of Example 8, Comparative Example 6, and Comparative Example 2. In the thermoplastic resin sheet of Example 8, necking was suppressed after the yield point, and it was a stress-strain curve without flat portions and irregularities. The thermoplastic resin sheet of Comparative Example 6 yielded a stress-strain curve that yielded at around 10 MPa and had flat portions and uneven portions by necking up to 450% strain. The thermoplastic resin sheet of Comparative Example 2 did not yield.

  The thermoplastic resin sheets of Examples 1 to 10 confirmed that necking was suppressed as compared with the thermoplastic resin sheets of Comparative Example 1 and Comparative Examples 3 to 9. Moreover, it was confirmed that the thermoplastic resin sheets of Examples 1 to 10 were improved in tensile properties as compared with the thermoplastic resin sheet of Comparative Example 2.

  In addition, although the specific Example using a polyethylene resin was shown as a material of PO resin layer, even when a polypropylene resin was used, it confirmed that the same excellent evaluation result as a polyethylene resin was obtained.

DESCRIPTION OF SYMBOLS 1 ... Thermoplastic resin sheet 2 ... Laminated body 2a ... 1st surface 2b ... 2nd surface 11 ... PO resin layer (polyolefin resin layer)
12 ... EVA resin layer (ethylene-vinyl acetate copolymer resin layer)
41 ... thermoplastic resin sheet 42 ... third layer 42a ... outer surface 43 ... fourth layer 43a ... outer surface

Claims (5)

It comprises a plurality of polyolefin resin layers and a plurality of ethylene-vinyl acetate copolymer resin layers,
The polyolefin resin layer is a polyethylene resin layer or a polypropylene resin layer,
A thermoplastic resin sheet in which a plurality of the polyolefin resin layers and a plurality of the ethylene-vinyl acetate copolymer resin layers are laminated in a total thickness of 40 or more.   The thermoplastic resin sheet according to claim 1, wherein a plurality of the polyolefin resin layers and a plurality of the ethylene-vinyl acetate copolymer resin layers are alternately laminated in the thickness direction.   The thermoplastic resin according to claim 1 or 2, wherein a ratio of 5% modulus at 23 ° C of the polyolefin resin layer is 3 or more to 5% modulus at 23 ° C of the ethylene-vinyl acetate copolymer resin layer. Resin sheet.   In 100 mass% of the total of the polyolefin resin layer and the ethylene-vinyl acetate copolymer resin layer, the total content of the polyolefin resin layer is from 50 mass% to 80 mass%, and the ethylene-acetic acid The thermoplastic resin sheet according to any one of claims 1 to 3, wherein the entire content of the vinyl copolymer resin layer is 20% by mass or more and 50% by mass or less.   The thermoplastic resin sheet according to any one of claims 1 to 4, wherein the thermoplastic resin sheet has six or more polyolefin resin layers and six or more ethylene-vinyl acetate copolymer resin layers.

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