JP2020023055A - Laminated sheet, manufacturing method of laminated sheet, and molded body - Google Patents

Abstract

To provide a laminated sheet by which separation between two resin layers is not generated even though it contains a large amount of calcium carbonate, a method of manufacturing the laminated sheet, and a molded body formed by using the laminated sheet.SOLUTION: The laminated sheet includes two or more resin layers and formed by laminating a first resin layer, which contains at least polyolefin resin and heavy calcium carbonate in a mass ratio of 50:50 to 20:80, and a second resin layer, which contains at least polyolefin resin and heavy calcium carbonate in a mass ratio of 50:50 to 99:1. An average particle diameter of the heavy calcium carbonate contained in the first resin layer according to an air permeability method is 0.7 to 20.0 μm and a residue on a 45 μm sieve of heavy calcium carbonate obtained by using a standard sieve prescribed by the JISZ8801-1 is less than 0.1 mass%. The first resin layer and the second resin layer include a laminated structure formed by the co-extrusion.SELECTED DRAWING: None

Description

  The present invention relates to a laminated sheet in which two or more resin layers are laminated, a method for producing the same, and a molded article formed from the laminated sheet.

  2. Description of the Related Art Conventionally, a sheet is molded from a thermoplastic resin composition in which a polyolefin resin and an inorganic filler are mixed to obtain a synthetic paper (Patent Documents 1 to 7).

  For example, Patent Document 7 discloses a thermoplastic resin composition containing polyethylene, polypropylene as a thermoplastic resin, calcium carbonate and titanium dioxide as inorganic fillers at 3 parts by mass, 52 parts by mass, 44 parts by mass, and 1 part by mass, respectively. There has been proposed a laminated sheet obtained by co-extruding a thermoplastic resin composition containing 85 parts by mass of polypropylene and 15 parts by mass of calcium carbonate.

JP-B-46-40794 JP-A-56-11837 JP-A-56-141339 JP 2001-277449 A JP-A-2002-36470 JP-T-2007-506587 JP-A-2017-213889

  However, in order to improve the whiteness and opacity as synthetic paper, when trying to include more calcium carbonate in the laminated resin layer, in the laminating method, there is a possibility that peeling may occur due to variations in laminating conditions. However, even when the laminated sheet was produced by co-extrusion as an integral molding, a situation occurred in which peeling occurred between the two resin layers laminated during the manufacturing process or when the laminated sheet was used. In addition, the surface appearance (surface smoothness) of the laminated sheet also varied greatly, and was not satisfactory.

  The present invention has been made in view of the above circumstances, and does not cause separation between two resin layers even if it contains a large amount of calcium carbonate, and has excellent surface smoothness. It is an object of the present invention to provide a method and a molded article formed from the laminated sheet.

  The object of the present invention has been achieved by the following.

(1) A first resin layer containing at least a polyolefin resin and surface-treated heavy calcium carbonate at a mass ratio of 50:50 to 20:80, and at least a polyolefin resin and heavy calcium carbonate at 50:50. A laminated sheet of two or more resin layers, in which a second resin layer containing a mass ratio of ~ 99: 1 is laminated,
The average particle diameter of the heavy calcium carbonate contained in the first resin layer and the second resin layer is 0.7 to 20.0 μm by an air permeation method, and the heavy calcium carbonate is defined in JISZ8801-1. The 45 μm sieve residue from the standard sieve is less than 0.1% by weight;
The laminated sheet, wherein the first resin layer and the second resin layer have a laminated structure formed by co-extrusion.

(2) The laminated sheet according to (1), wherein the polyolefin resin is a polypropylene resin and / or a polyethylene resin.
(3) The laminated sheet according to (1) or (2), wherein the ratio of the thickness of the first resin layer to the thickness of the second resin layer is 50:50 to 95: 5.
(4) The laminated sheet according to any one of (1) to (3), wherein the first resin layer and / or the second resin layer is formed of a foamed layer.
(5) The method for producing a laminated sheet according to any one of the items 1 to 4, further comprising a co-extrusion step using a T-die method for laminating the first resin layer and the second resin layer. A method for manufacturing a laminated sheet.
(6) The method for producing a laminated sheet according to any one of the above (1) to (4), wherein the first resin layer and the second resin layer are laminated by a co-extrusion step by an inflation method for laminating the first resin layer and the second resin layer. Sheet manufacturing method.
(7) A molded article formed from the laminated sheet according to any one of (1) to (4).

  Hereinafter, embodiments of the present invention will be described, but the present invention is not particularly limited thereto, and can be appropriately modified.

<Laminated sheet>
The laminated sheet of the present invention comprises a first resin layer containing at least a polyolefin resin and a surface-treated heavy calcium carbonate in a mass ratio of 50:50 to 20:80, and at least a polyolefin resin and a heavy calcium carbonate. A laminated sheet of two or more resin layers obtained by laminating a second resin layer containing a second resin layer having a mass ratio of 50:50 to 99: 1,
The average particle diameter of the heavy calcium carbonate contained in the first resin layer and the first resin layer is 0.7 to 20.0 μm by an air permeation method, and the heavy calcium carbonate is specified in JISZ8801-1. 45 μm sieve residue by standard sieve is less than 0.1% by mass,
The first resin layer and the second resin layer have a laminated structure formed by co-extrusion.
The laminated sheet of the present invention has excellent performance in adhesion, appearance, whiteness and opacity as compared with a laminated sheet obtained by lamination.

  The laminated sheet of the present invention can be applied to a laminated sheet having a first resin layer and a second resin layer, even if it has other layers. For example, the present invention can be applied to three or more layers such as a second resin layer / a first resin layer / a second resin layer, and a first resin layer / a second resin layer / a third resin layer.

  The laminated sheet of the present invention contains at least a polyolefin resin and heavy calcium carbonate subjected to a surface treatment, and the film thickness of the laminated sheet composed of these two materials is 80% or more of the film thickness of the entire laminated sheet. Is configured.

In the laminated sheet of the present invention, the whiteness is preferably 85 to 100%. If the whiteness is less than 85%, when color printing is performed on the surface, a visually recognizable color tone may change. The whiteness of the present invention is a value measured according to JIS P8148: 2001.
The opacity is preferably from 85 to 100%. If the opacity is less than 85%, it may be difficult to visually recognize the surface during printing. The opacity is a value measured according to JIS P8149.

≪Polyolefin resin≫
Examples of the polyolefin resin constituting the laminated sheet of the present invention include polyethylene resin (high-density, low-density, ultrahigh-molecular-weight), polypropylene resin, polycycloolefin resin, and a resin composed of a copolymer thereof, and the like. One or more types can be appropriately selected in consideration of the melting point and the elastic modulus. Those polymerized with a metallocene catalyst can also be used. Particularly, polyethylene resin and polypropylene resin are preferable.

  A mixture of a high-density polyethylene resin and a low-density polyethylene resin can also be used. The mixing ratio can be appropriately selected depending on the desired performance, but the high-density polyethylene resin: low-density polyethylene resin = 99: 1 to 20:80 (mass ratio) in view of the characteristic balance of the mixed resins. preferable.

Melt mass flow rate (MFR) is preferably 0.02 g / 10 min or more and 2.0 g / 10 min or less from the viewpoint of processability, and further favorable processing is performed in view of high filling of heavy calcium carbonate. It is more preferably from 0.1 g / 10 to 1.0 g / 10 minutes from the viewpoint of properties (measured according to JIS K7210). The MFR can be measured by a melt indexer at a load of 21.18 N, a temperature of 230 ° C. for a polypropylene resin (according to JIS K7210), and a temperature of 190 ° C. for a polyethylene resin (according to JIS K6730). The density (unit: g / cm ³ ) can be measured according to JIS K7112.

  In addition, a polypropylene resin having a long-chain branched structure can be mixed and used for smooth conveyance of the laminated sheet. Here, the polypropylene resin may be a copolymer as long as the polypropylene chain is 50 mol% or more.

  The polypropylene resin having a long-chain branched structure of the present invention is characterized in that the isotactic triad fraction (mm) measured by 13 C-NMR is 95% or more. For the measurement, see Macromolecules, Vol. 35, no. 10. Known measurement methods such as those described in 2002, pages 3839 to 3842 can be referred to.

  The polypropylene resin having a long-chain branched structure of the present invention has a melt flow rate (MFR) measured at a temperature of 230 ° C. and a load of 2.16 Kg of not less than 0.1 g / 10 min and not more than 100 g / 10 min from the viewpoint of processability. Preferably, there is. It is preferably 0.2 g / 10 min or more, more preferably 0.3 g / 10 min or more, from the viewpoint of further good workability in view of the fact that heavy calcium carbonate is highly filled.

  The polypropylene resin having a long-chain branched structure of the present invention may be contained in the range of 0.1 to 100% by mass of the whole polyolefin resin, and preferably 1 to 40% by mass in view of the property balance of the mixed resin. %.

≪Heavy calcium carbonate≫
The heavy calcium carbonate contained in the first and second resin layers of the present invention has an average particle size of 0.7 to 20.0 μm by a surface-treated air permeation method, and is defined in JISZ8801-1. Characterized in that the 45 μm sieve residue from the standard sieve is less than 0.1% by weight.

  By setting the average particle diameter in this range, it is possible to improve the adhesion and the surface smoothness of a laminated sheet having a laminated structure by co-extrusion. When the average particle diameter is less than 0.7 μm, it is difficult to obtain heavy calcium carbonate obtained by pulverizing limestone, and the risk of heavy calcium carbonate aggregating in the resin layer increases. If the average particle size is more than 20.0 μm, the surface smoothness may be reduced.

  In the present invention, heavy calcium carbonate having a 45 μm sieve residue based on a standard sieve specified in JISZ8801-1 of less than 0.1% by mass means that inhibition of surface smoothness due to the presence of excessive particles is suppressed. Is preferred.

≪Surface treatment≫
The heavy calcium carbonate of the present invention has been subjected to a surface treatment. By performing the surface treatment, it is possible to suppress aggregation in the resin layer, which is a concern when the heavy calcium carbonate is highly filled. Examples of the surface treatment agent include saturated fatty acids having 10 to 30 carbon atoms, unsaturated fatty acids, and salts thereof.

  More preferred are saturated fatty acids having 12 to 26 carbon atoms, unsaturated fatty acids and salts thereof. Specific examples of the saturated fatty acid include palmitic acid, stearic acid, lauric acid, myristic acid, alineic acid, behenic acid, lignoceric acid, serotinic acid, montanic acid, and melicic acid. Magnesium salts, calcium salts and the like can be mentioned. The surface treatment can be performed by a known conventional method.

≪Other thermoplastic resins, additives, etc.≫
Other thermoplastic resins compatible with the polyolefin resin may be added as long as the effects of the present invention are not impaired. Further, a colorant, a lubricant (such as calcium stearate), a coupling agent, a flow improver, a dispersant, an antioxidant, an ultraviolet absorber, a stabilizer, an antistatic agent, a foaming agent, and the like may be added as additives. Good. These may be blended in the kneading step or may be blended in the resin composition before the kneading step.

<< First and second resin layers >>
The first resin layer of the present invention contains at least a polyolefin resin and a surface-treated heavy calcium carbonate at a mass ratio of 50:50 to 20:80 from the viewpoint of achieving both good workability and whiteness. It is a resin layer to be formed. The polyolefin resin and the heavy calcium carbonate preferably have a mass ratio of 40:60 to 25:75 from the viewpoint of achieving both high filling of the heavy calcium carbonate and good workability.

  The second resin layer of the present invention contains at least a polyolefin resin and heavy calcium carbonate in a mass ratio of 50:50 to 99: 1. The weight ratio is preferably from 60:40 to 95: 5 from the viewpoint of balance between whiteness, opacity, surface smoothness, and adhesion.

  The amount of heavy calcium carbonate contained in each of the first resin layer and the second resin layer can be appropriately selected depending on the desired performance of the laminated sheet, but the laminated sheet imparts functions with other functional layers. In consideration of the possibility, in the case of a laminated sheet having three or more layers, the amount of heavy calcium carbonate contained in the resin layer located on the outside is preferably smaller than the amount contained in the resin layer located on the inside.

  The polyolefin resin used in the first resin layer and the second resin layer of the present invention may be the same or different. One or more types can be appropriately selected from the scope of the present invention depending on the desired performance required for the laminated sheet.

At least one of the first resin layer and the second resin layer of the present invention is preferably a foamed layer from the viewpoint of weight reduction.
As the foaming agent, any of a foaming gas such as butane and isobutane, and a pyrolytic foaming agent can be used. The amount can be appropriately adjusted depending on the degree of foaming in the range of 0.01 to 5% by mass based on the polyolefin resin.

  The film thickness of the laminated sheet of the present invention is 25 to 450 μm as a whole, and preferably 25 to 200 μm from the viewpoint of handleability.

  The thickness of each of the first resin layer and the second resin layer of the present invention is practically preferably 1 to 200 μm, and when the ratio is 50:50 to 95: 5. The effect of the adhesion of the invention is remarkable. Further, the ratio is preferably 50:50 to 80:20 in view of the balance between the layers of coextrusion.

  In the present invention, any combination of the first resin layer and the second resin layer can be appropriately applied as a laminated sheet. For example, the first / second, first / second / first, first / second / second / first, second / first / second, first / second / third, second / First / third, etc. Here, the third resin layer represents a layer other than the first resin layer and the second resin layer.

  In order to further add the paper feeling of the laminated sheet of the present invention, a layer of a propylene-based resin containing 8 to 55% by mass of inorganic fine powder is provided between the first resin layer and the second resin layer. It can be preferably formed as an intermediate layer. Further, the intermediate layer may contain a small amount of a low-melting-point resin such as a propylene-based copolymer, a high-density polyethylene, a polystyrene, or an ethylene-vinyl acetate copolymer in order to improve the stretchability.

<Production method of laminated sheet>
The laminated sheet of the present invention is characterized in that the first resin layer and the second resin layer are co-extruded and laminated. It is preferable to apply a multilayer T-die system using a feed block and a multi-manifold, and an extrusion inflation system using a plurality of annular dies, since the effect of the present invention is great.

  For a process such as kneading before co-extrusion from a T-die, an ordinary method can be used. For example, the polyolefin resin and the heavy calcium carbonate may be kneaded and melted before being put into the molding machine from the hopper, or the polyolefin resin and the heavy calcium carbonate may be kneaded and melted simultaneously with the molding with the molding machine. . In the melt kneading, from the viewpoint of uniformly dispersing the polyolefin resin and the heavy calcium carbonate, kneading is preferably performed by applying a high shear stress, and for example, kneading is preferably performed using a biaxial kneader.

  In the production method of the present invention, the mixture of the polyolefin resin and the heavy calcium carbonate may be in the form of pellets, and may not be in the form of pellets. Instead, for example, pellets such as cylinders, spheres, and elliptical spheres may be formed.

  The size of the pellet may be appropriately set according to the shape. For example, in the case of a spherical pellet, the diameter may be 1 to 10 mm. In the case of an elliptical spherical pellet, the aspect ratio may be 0.1 to 1.0, and the aspect ratio may be 1 to 10 mm. In the case of cylindrical pellets, the diameter may be in the range of 1 to 10 mm, and the length may be in the range of 1 to 10 mm. These shapes may be formed into pellets after the kneading step described later. The shape of the pellet may be formed according to a conventional method.

  Molding may be performed by a direct method of continuously performing a kneading step and a sheet-forming step. For example, a T-die type twin-screw extruder or a method using an inflation device may be used. Good.

<< T-die method >>
As the T-die molding machine in the present invention, a known multi-manifold die, feed block, static mixer, or the like can be used. In order to efficiently obtain the configuration of the present invention, it is preferable to use a feed block having 11 or more fine slits.

  By using such a feed block, the size of the apparatus does not become extremely large, so that high-precision lamination is possible even when there are few foreign substances due to thermal degradation and the number of laminations is extremely large. In addition, the lamination accuracy in the width direction is significantly improved as compared with the prior art. Further, in this device, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, an arbitrary layer thickness can be achieved.

  The laminated sheet discharged from the die is extruded onto a cooling body such as a casting drum and solidified by cooling to obtain a casting film. At this time, it is preferable that the discharged sheet is brought into close contact with the cooling body and rapidly cooled and solidified by electrostatic force using a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode.

  Further, as a method of bringing the discharged sheet into close contact with the cooling body, a method of blowing air from a slit-like, spot-like, or planar device, and a method using a nip roll are also preferable.

  The laminated sheet of the present invention, when forming a casting film, utilizing the peripheral speed difference of a group of rolls such as a casting drum, at a temperature higher than the glass transition temperature of the polyolefin resin by at least 10 ° C. Although it can be appropriately selected depending on the whiteness and physical properties, it is preferably stretched 1.1 to 3.0 times in view of whiteness, opacity, adhesion, and surface appearance.

≪Horizontal stretching≫
The laminated sheet manufactured by the T-die method of the present invention preferably further has a step of laterally stretching the formed sheet by a tenter. When the sheet after molding is subjected to transverse stretching, the density of the sheet is further reduced, and good whiteness can be obtained. The stretching ratio is 1.01 to 10.0 times, and can be appropriately selected depending on whiteness and physical properties. However, in view of whiteness, opacity, adhesion, and surface appearance, the stretching ratio is 1.1 to 3.0 times. It is preferable to keep it.

≪Inflation method≫
The inflation method of the present invention is preferably an air-cooled inflation method, in which the above-mentioned pellets are melted by an extruder with an annular die, extruded into a tube, and air supplied from a blower or the like is supplied from an air-cooled ring to a molten tube. This is a method in which after cooling and solidifying by spraying, the sheet is folded by a pinch roll through a guide plate, and is taken out by a take-up machine.

  As a molding machine, a cooling ring, a blower, a guide plate, a pinch roll, a film take-off machine, and the like which can be used in this molding method, widely available devices can be used.

  The conditions for forming the film by the air-cooled inflation method are not particularly limited, but the die diameter is usually φ50 mm to φ500 mm, the die lip width is usually 0.8 mm to 4.0 mm, the blow ratio is 1.5 to 5, The temperature is usually 170 to 250 ° C, preferably 170 to 220 ° C from the viewpoint of processability, the molding speed is usually 5 to 100 m / min, and preferably 10 to 50 m / min from the viewpoint of molding stability.

  For the laminated sheet of two or more layers of the present invention, an inflation method having a plurality of extruders and a co-extruded multilayer annular die, preferably a method used for an air-cooled inflation method is applied.

  In a preferred embodiment of the laminated sheet having two or more layers of the present invention, for example, a polypropylene resin or a polyethylene resin composition constituting the first resin layer and a polypropylene resin or the polyethylene resin composition constituting the second resin layer are both used. It is melted by a multiple extruder with an extruded multilayer annular die, extruded into a tube shape, and air supplied from a blower or the like is blown from an air cooling ring to a melting tube to be cooled and solidified, and then folded by a pinch roll via a guide plate. It is a method of picking up with a pick-up machine.

  A molding machine, a cooling ring, a blower, a guide plate, a pinch roll, a film take-up machine and the like which can be used at this time may be a device widely used in a market, and a special device is not required. The conditions for forming the film by the air-cooled inflation method are not particularly limited, but the die diameter is usually φ50 mm to φ500 mm, the die lip width is usually 0.8 mm to 4.0 mm, the blow ratio is 1.5 to 5, and the molding is performed. The temperature is usually 170 to 250 ° C., preferably 170 to 220 ° C. from the viewpoint of processability, the molding speed is usually 5 to 100 m / min, and preferably 10 to 50 m / min from the viewpoint of molding stability.

  In the air-cooled inflation method, a tubular film can be formed by air cooling from the outside and / or the inside. In addition, any method such as an upward method, a horizontal method, or a downward method can be adopted as a blow film forming method of a tube film. It is suitable for a polypropylene resin composition for forming a film.

  Examples of the inflation method other than the air-cooled inflation method include a water-cooled inflation method and a tubular biaxial stretching method, and a film can be produced by applying these methods.

  For stretching, sequential biaxial stretching using a tenter, simultaneous biaxial stretching, and simultaneous biaxial stretching using a double inflation device can be used as appropriate.

≪Bending process≫
In the present invention, in addition to the above-described steps, a step of bringing a laminated sheet as an object into contact with a solid object in a direction perpendicular to the crystal orientation axis while moving the object in the MD direction to generate a bent state May be included. As this method, for example, a known method described in WO2015 / 060271 can be adopted.

  In the present invention, a long solid object such as a rod, a plate or a beam is conveyed on the surface of a laminated sheet (hereinafter sometimes simply referred to as a sheet) before or after stretching. It is preferable to provide a process of pressing the sheet so as to cross the direction (machine direction, MD direction) and bending the sheet. At that time, at the contact portion of the solid object with the sheet, in a state where the sheet is bent and bent, it is possible to apply a stress by moving the object and the sheet relative to each other to reduce the whiteness. It is preferable from the viewpoint of increasing.

  In the present invention, the bending treatment may be performed at least once on the front surface or the back surface of the sheet. The bending treatment can be performed on only one of the front and back surfaces of the sheet, or on both surfaces. From the viewpoint of preventing warpage, it is preferable to perform the bending treatment on both sides of the sheet.

  In the bending treatment of the present invention, only one of the solid objects may be used, but two or more solid objects may be used at the same time.

<Molded body>
By processing the laminated sheet of the present invention, a molded article such as a wrapping paper, a carrying bag, a container, a protective cap, a tray, a film, a sheet, a shopping bag, a binding string, a hanger, or the like can be obtained.

  The following laminated sheets were prepared and evaluated for adhesion, surface appearance (smoothness), whiteness and opacity. The evaluation was performed in an atmosphere of 23 ° C. and 55% RH unless otherwise specified. In the table, "OP" is a polyolefin resin, "HCC" is heavy calcium carbonate, "treatment" is the presence or absence of surface treatment of heavy calcium carbonate, "particle size" is an average particle size of μm, "Residue" represents 45% sieve residue%, and "Amount%" represents mass% when the total of the polyolefin resin and heavy calcium carbonate is 100% by mass.

(Examples 1 to 10, Comparative Examples 1 to 9)
A resin composition was prepared by mixing a polypropylene resin (density 0.91 g / cm ³ , MFR 0.50 g / 10 min, abbreviated as PP in the table) and heavy calcium carbonate so as to have a mass% shown in the table. , Magnesium stearate (Rikemar AS-003 manufactured by Riken Vitamin Co., Ltd.) is blended with 1% by mass of the resin composition and mixed using an HTM50 type counter-rotating twin-screw extruder (manufactured by CTC). And kneaded to prepare raw material pellets.

Thereafter, the strands were extruded from a die at 210 ° C. through a 150 mm L / D = 10 strainer manufactured by Katsu Seisakusho maintained at 210 ° C., cooled with water, and cut to prepare pellets for each sample.
The pellets produced in this manner were melt-extruded using a screw extruder, and each layer was co-extruded from a feed block type T-die, and then quenched on a cooling roll to obtain a multilayer sheet having a thickness of about 0.30 mm. The sheet was heated at 110 ° C. and stretched 1.5 times in the film flow direction (longitudinal direction).

The 1.5-fold stretched sheet was heated at 160 ° C. and stretched 2-fold in a direction (horizontal direction) perpendicular to the flow direction, and taken up by a film sheet take-up machine FT3W20 manufactured by Toyo Seiki Co., Ltd. to obtain a sample of a laminated sheet. . The content and film thickness of the whiteness were determined so as to be at a practical level.
The samples thus prepared were evaluated for adhesion, surface smoothness, whiteness and opacity as described below.

In Example 9, high-density polyethylene resin (density 0.96 g / cm ³ , MFR 0.30 g / 10 min, abbreviated as HDPE in the table) was used instead of polypropylene resin. 0.96 g / cm ³ , MFR 0.30 g / 10 min, abbreviated as HDPE in the table) and low density polyethylene resin (density 0.92 g / cm ³ , MFR 2.0 g / 10 min, abbreviated as LLDPE in the table) 60: A sample mixed at a mass ratio of 40 was also prepared.

In Example 11, a pellet and a 1% by mass baking soda-based chemical blowing agent (decomposition temperature: 155 ° C., generated gas amount: 230 ml / 5 g) were added to the pellet, and co-extruded at 195 ° C. to produce a laminated sheet.
As a reference comparative example, a cast film in which the first resin layer is stretched in the longitudinal direction is prepared, and then a resin composition for forming the second resin layer is melt-kneaded by another extruder and laminated at 200 ° C. (lamination). Then, a sample stretched in the lateral direction was prepared.

<Adhesion test>
Two scratches reaching the second resin layer at an angle of 45 ° to the second resin layer at a 45 ° angle are attached to the surface of the first resin layer at two intervals of 5 cm, and a cellophane adhesive tape specified in JIS Z1522 is pressed thereon. After that, the tape is rapidly peeled at an angle of about 45 °. At this time, the area of the first resin layer which is peeled off together with the tape is compared with the area to which the tape is adhered, and evaluated according to the following five grades. If it is 3 or more, it is a practically usable level without any problem of peeling of the first resin layer.
5: Area of resin layer to be peeled No peeling (level that can be used without peeling)
4: Area of resin layer to be peeled 15% or less (level that can be used without peeling)
3: The area of the resin layer to be peeled is more than 15% and 30% or less (a level that can be used without peeling)
2: The area of the resin layer to be peeled is more than 30% and 50% or less (the level at which the peeling slightly occurs).
1: Area of resin layer to be peeled exceeds 50% (level at which peeling is extremely difficult)

<Surface smoothness>
The surface appearance was evaluated by surface smoothness. The surface condition of both surfaces of the sheet corresponding to an area of 1 square meter was visually and tactilely observed, and a portion having the worst surface condition was evaluated according to the following criteria.
〇: No unevenness △: Slight unevenness (no problem in actual use)
X: Those with remarkable unevenness (level causing trouble during printing)

<Whiteness>
It was measured according to JIS P8148: 2001.
<Opacity>
The opacity of the sheet was measured by the paper and paperboard specified in JIS P8149, the opacity test method (paper backing), and the diffuse illumination method. In addition, the measuring method of the optical system conformed to JIS Z8722.
When the numerical value of the opacity was 85 or more, good visibility was obtained.

  Tables 1 and 2 show that the laminated sheet of the present invention has good adhesion and surface appearance.

(Examples 12 and 13)
In the same manner as in Example 1, pellets of the resin composition for lamination were produced. The pellets were vacuum dried at a temperature of 90 ° C. for 5 hours using a rotary drum type vacuum dryer. These pellets are supplied to independent single screw extruders having a cylinder temperature of 200 ° C. and a screw diameter of 60 mm, respectively. The maximum diameter is 100 mm, the lip clearance is 1.0 mm, and the temperature is set at 190 ° C. With a blow rate of 2.7 at a bubble rate of 23.6 m / min, a blow rate of 2.7 times in the direction perpendicular to the take-up direction and 2.2 times in the take-off direction. At the same time, the sheet was extruded upward, air-cooled by a cooling ring, and wound through a 1.5-horizontal stretching step similar to that of Example 1 while folding by a nip roll above the die to produce a laminated sheet for evaluation. The same adhesion test, surface smoothness, whiteness and opacity as in Example 1 were evaluated.

Table 3 shows that the laminated sheet of the present invention has good adhesion, surface smoothness, whiteness and opacity.

Claims (7)

A first resin layer containing at least a polyolefin resin and surface-treated heavy calcium carbonate at a mass ratio of 50:50 to 20:80, and at least a polyolefin resin and heavy calcium carbonate at 50:50 to 99: A laminated sheet of two or more resin layers obtained by laminating a second resin layer containing at a mass ratio of 1 or more,
The average particle diameter of the heavy calcium carbonate contained in the first resin layer and the second resin layer is 0.7 to 20.0 μm by an air permeation method, and the heavy calcium carbonate is specified in JISZ8801-1. The 45 μm sieve residue from the standard sieve is less than 0.1% by weight;
The laminated sheet, wherein the first resin layer and the second resin layer have a laminated structure formed by co-extrusion.   The laminated sheet according to claim 1, wherein the polyolefin resin is a polypropylene resin and / or a polyethylene resin.   3. The laminated sheet according to claim 1, wherein the ratio of the thickness of the first resin layer to the thickness of the second resin layer is 50:50 to 95: 5. 4.   The laminated sheet according to any one of claims 1 to 3, wherein the first resin layer and / or the second resin layer comprises a foam layer.   The method for producing a laminated sheet according to any one of claims 1 to 4, further comprising a co-extrusion step using a T-die method for laminating the first resin layer and the second resin layer. Manufacturing method.   The method for producing a laminated sheet according to any one of claims 1 to 4, wherein a laminated sheet having a co-extrusion step by an inflation method for laminating the first resin layer and the second resin layer. Production method.   A molded article formed from the laminated sheet according to any one of claims 1 to 4.