JP2009196368A - Propylene resin-foamed laminated flat plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a propylene resin-foamed laminated flat plate which has a high expanding rate, is used as a base stock of a box or the like, is lightweight and is excellent in processability. <P>SOLUTION: The propylene resin-foamed laminated flat plate 1 is obtained by integrally layering a surface layer 3 consisting of an unstretched propylene resin film on both sides of a core layer 2 consisting of a propylene resin-extruded foam body by using a coextrusion foaming method. The propylene resin-extruded foam body constituting the core layer has 0.045-0.30 g/cm<SP>3</SP>density and ≥50% closed cell ratio. The unstretched propylene resin film constituting the surface layer 3 has 60-300 g/m<SP>2</SP>basis weight. The density of the whole propylene resin-foamed laminated flat plate is 0.10-0.35 g/cm<SP>3</SP>. The propylene resin-foamed laminated flat plate satisfies expression (1): F≥2.5×10<SP>-3</SP>×Y-0.15 (wherein F (kgf) is the flexural strength of the propylene resin-foamed laminated flat plate, and Y (g/m<SP>2</SP>) is the basis weight of the propylene resin-foamed laminated flat plate). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polypropylene resin foam laminated flat plate that can be used as various core materials, partition materials, folded materials, boxing materials, and the like.

  2. Description of the Related Art Conventionally, a simple packaging box called a returnable box is used in a company or factory to transfer products and intermediate products from one department to another department or store them temporarily. Conventionally, corrugated cardboard boxes have been widely used as this kind of returnable boxes. However, the corrugated cardboard return boxes have a problem that paper dust comes out of the material and contaminates the product. Also, in confectionery factories, foods such as candy may be stored in boxes, but paper cardboard boxes are not water-resistant and cannot be washed, are unsanitary, and are used for a long time. There was a problem that it could not be used repeatedly.

If a synthetic resin is used as the material of the returnable box, the above-mentioned problem of the returnable box made of cardboard can be solved. As a synthetic resin material that has lightness and shape retention like paper cardboard and can be used in place of paper cardboard, for example, plastic cardboard or T-die is extruded and foamed. Examples thereof include a low-foamed propylene-based resin foam plate having a density of about 0.5 to 0.3 g / cm ³ (foaming ratio of about 2 to 3 times).

  Plastic cardboard is water resistant and can be washed. However, plastic corrugated cardboard, like paper corrugated cardboard, has a hollow structure in which a corrugated sheet material is interposed between a front surface material and a back surface material, so that water penetrates into the hollow portion of the corrugated cardboard when washed. It is not preferable because it remains. Also, plastic corrugated cardboard is made by interposing a non-foamed corrugated sheet material between the non-foamed surface material and the back material, so it is heavier than paper cardboard and has an edge that is more than paper cardboard. Furthermore, there is also a problem that the operator can easily cut his / her hand because it is hard and sharp.

  On the other hand, low-foamed propylene resin foam boards are also heavier than paper corrugated cardboard, and have a thick skin in the manufacturing process, so the rigidity, especially the 10% compressive strength, is too high, and the workability is poor. Inferior toughness, for example, when adopting a normal corrugated cardboard box form, when sealing the upper and / or lower surface of the cardboard box without using a gum tape, it is not possible to assemble the tongue pieces alternately was there. Further, a propylene-based resin foam sheet obtained by extrusion foaming from an annular die described in JP-A-4-363227 has a higher expansion ratio than the propylene-based resin foam plate obtained by extrusion foaming from a T die. However, there is a problem that the rigidity is insufficient and warping occurs, and the surface flatness is also insufficient.

On the other hand, the propylene-based resin plate-like foam described in JP-A-8-231745 has a density of 0.06 to 0.3 g / cm by making the bubbles in the inner layer portion of the foam into a specific shape. ³ and light weight, cushioning properties, but also has excellent punching workability, reduces the appearance and printability is inferior in surface smoothness, also it has a problem that rigidity is insufficient. On the other hand, a synthetic resin film having a tensile strength of 10 kg / mm ² or more is laminated on at least one side of a plate-like propylene-based resin foam having a density of 0.07 to 0.25 g / cm ³ proposed by the present applicant. The resulting propylene-based resin foam laminate ( Japanese Patent Laid-Open No. 10-748 ) has excellent physical properties such as excellent buffering and punching properties and relatively high rigidity. However, it is necessary to use a stretched film as a synthetic resin film having a tensile strength of 10 kg / mm ² or more laminated on the foam, which increases the cost and increases the production efficiency for laminating the stretched film or the like on the foam. As a result, the manufacturing cost is high.

  As a result of intensive studies to solve the above problems, the present inventors have found that a core layer made of a propylene resin foam and a surface layer made of a propylene resin film or a low propylene resin foam are laminated and integrated. When producing a resin-based resin-laminated laminated flat plate, a cylindrical foam in which the core layer and the surface layer are laminated and integrated is obtained by coextrusion to obtain a cylindrical foam, and then the cylindrical foam is cut open to form a plate Later, when a method of heat treatment at a specific temperature and taking up with a roll or the like is adopted, rigidity, surface smoothness, printability, and appearance can be achieved while being lightweight, without laminating a film having a high tensile strength such as a stretched film. The present inventors have found that a propylene-based resin foam laminated flat plate having excellent buffering properties and excellent punching properties can be obtained, and the present invention has been completed.

The propylene-based resin foam laminated flat plate of the present invention is
A propylene-based resin foam laminated flat plate in which a surface layer made of an unstretched propylene-based resin film is laminated and integrated on both surfaces of a core layer made of a propylene-based resin extruded foam,
The foam laminated flat plate is obtained by coextrusion and foaming of the propylene resin foamable melt constituting the core layer and the propylene resin non-foamable melt constituting both surface layers to laminate the core layer and the surface layer together. Formed by the laminating method
The foamed laminated flat plate has a density of 0.045 to 0.30 g / cm ³ of a propylene-based resin extruded foam constituting the core layer and a closed cell ratio of 50% or more . The basis weight of the resin film layer is 60 to 300 g / m ² , the density of the entire foamed laminated flat plate is 0.10 to 0.35 g / cm ³ , and the overall thickness is 2 to 10 mm.
And with a center line average roughness of the surface of the foam laminate flat is 5μm or less, the bending strength of the foamed laminate flat: the F (kgf), the basis weight of foam stacked flat: between Y (g / m ²⁾ A propylene-based resin foam laminated flat plate characterized by the following formula (1):
F ≧ 2.5 × 10 ⁻³ × Y−0.15 (1)

The propylene-based resin foam laminated flat plate of the present invention is between the tensile strength of the unstretched propylene-based resin film constituting the surface layer: E (kgf / cm) and the basis weight of the film: X (g / m ² ). In addition, it is preferable that the following expression (2) holds.
E <0.07X (2)

Further, the propylene-based resin foam laminated flat plate of the present invention preferably has a propylene-based resin constituting the surface layer containing 5 to 30% by weight of an inorganic filler.

As described above, the propylene-based resin foam laminated flat plate of the present invention has a density of the propylene-based resin extruded foam constituting the core layer of 0.045 to 0.30 g / cm ³ and a closed cell ratio of 50% or more. The density of the entire foamed laminated flat plate is 0.10 to 0.35 g / cm ³ , the overall thickness is 2 to 10 mm, and the basis weight of the unstretched propylene-based resin film layer constituting the surface layer is 60 to 300 g / In the case of m ² , the center line average roughness of the surface on which the surface layer is laminated is 5 μm or less, the bending strength of the foam laminated flat plate: F (kgf), and the basis weight of the foam laminated flat plate : Y (g / m ² ) has the advantage of being excellent in rigidity, secondary workability, light weight, printability, and cleanability by the relationship expressed by the above formula (1).

The unstretched propylene resin film that make up the surface layer is warpage are laminated to both surfaces of the core layer becomes no good flat.

It is a conceptual diagram which shows the structure of the propylene-type resin foaming laminated flat plate of this invention.

FIG. 1 shows an example of a propylene-based resin foam laminated flat plate 1 according to the present invention. The foam laminated flat plate 1 has a surface layer 3 made of an unstretched propylene resin film on both surfaces of a core layer 2 made of a propylene-based resin foam. Has a structure in which these are laminated and integrated. Surface layer 3 is laminated on both sides in order to obtain a higher rigidity than is laminated only on one side of the core layer 2.

In the present invention, the foamed laminated flat plate 1 is prepared by supplying the propylene-based resin foamable melt and the propylene-based resin non-foamable melt to the annular coextrusion die at the tip of the extruder, the cylindrical foam obtained by extrusion from die annular coextrusion cut open in the extrusion direction Ru can be produced by co-extrusion, such that the plate-like. In addition, in order to obtain the foamed laminated flat plate 1 having the surface layer 3 on both surfaces of the core layer 2 as shown in FIG. 1, the annular co-polymer is formed so that the non-foamed layer is formed on both surfaces of the foamed layer of the cylindrical foam. The propylene-based resin foamable melt and the propylene-based resin non-foamable melt may be joined together by an extrusion die.

When producing the propylene-based resin foam laminated flat plate 1 of the present invention, the tubular foam is cut along the extrusion direction to form a foam laminated plate. Thereafter, both the front and back surfaces of the foam laminated plate are provided with the surface layer 3. It is possible to employ a method of heating to a temperature higher than that of the propylene-based resin to be constituted (heat deformation temperature -20 ° C) and taking it up with a roll or the like. The above-mentioned “after” means that the foamed laminated board may be heated online, or the foamed laminated board may be wound up into a roll once, and then the roll may be unwound and heated later. . In addition, when both the surface layers 3 of the core layer 2 and / or the multilayer surface layer 3 have different thermal deformation temperatures of the base resin of each surface layer 3, the higher thermal deformation temperature is used as a reference (thermal deformation temperature − 20 ° C) or higher. The temperature at which the front and back surfaces of the foam laminate are heated is preferably 120 to 165 ° C, more preferably 123 to 155 ° C. Examples of the method for heating the foam laminate include a method using radiant heating with a far infrared ray, near infrared ray or the like using a heating furnace, and a method using contact heating with a hot roll. Note that heating above the (heat deformation temperature -20 ° C.) of the propylene-based resin constituting the surface layer 3 means that the foamed laminate immediately after coming out of the heating means is heated by heating means such as a heating furnace. It means that the surface temperature of the surface layer 3 is obtained by temperature measurement with infrared rays without delay, and the temperature is (heat distortion temperature−20 ° C.) or higher. The heat distortion temperature is a temperature measured according to JIS K7207 (bending stress 4.6 kgf / cm ² ). In addition, when the propylene-type resin containing an inorganic filler is used for the surface layer 3, let the heat deformation temperature of the propylene-type resin containing the inorganic filler be a heat deformation temperature.
Moreover, since the upper limit of the heating temperature on both the front and back surfaces of the foam laminate is a value that varies depending on the heat resistance of the propylene-based resin constituting the foam laminate, the range in which the surface state of the foam laminate does not deteriorate, It is adjusted below the melting point of the propylene-based resin constituting both the front and back surfaces of the foam laminate.

  As described above, both surfaces of the foamed laminate formed by cutting and opening the cylindrical foam obtained by the coextrusion method are heated to a temperature higher than that of the propylene-based resin forming the surface layer (thermal deformation temperature −20 ° C.). By adopting the take-up method, it is possible to eliminate the wave generated at both ends in the width direction of the foamed laminate and the winding of the laminate, and the mechanical strength and surface smoothness of the laminate are further improved. It becomes good. In addition, as a method of heating and taking out the foamed laminated board, after heating the laminated board with a heating furnace, a method of taking up with a roll or a conveyor, a method of simultaneously heating and taking up with a hot roll, etc. A wide variety of combinations are possible. In particular, it is preferable in terms of surface smoothness and the like to adopt a roll that can be heated or can press the surface of the heated foamed laminate as a take-up means.

  When obtaining the foamed laminated flat plate 1 having the structure shown in FIG. 1 in which the surface layers 3 are provided on both the front and back surfaces of the core layer 2, both sides of the foamed laminated plate obtained by cutting the cylindrical foam along the extrusion direction are heated. In the process, the heating temperature of the surface on the side that is located outside (outer peripheral surface side) of the cylindrical foam is higher than the (thermal deformation temperature −20 ° C.) of the propylene-based resin forming the surface layer 3. Is preferably 5 ° C. or more higher than the heating temperature of the surface located on the inner side (inner peripheral surface side) of the cylindrical foam. In particular, both surfaces of the foamed laminate having the surface layer 3 laminated on both surfaces of the core layer 2 are set to a temperature equal to or higher than the (thermal deformation temperature−20 ° C.) of the resin constituting the surface layer 3 and as described above, By providing a heating temperature difference of 5 ° C. or more and heating, the residual strain on the front and back surfaces of the foamed plate can be relaxed in a well-balanced manner, so that a flat plate with good appearance can be obtained.

  The base resin of the core layer 2 in the propylene-based resin foam laminated flat plate 1 includes a non-crosslinked propylene homopolymer, a propylene block copolymer which is a copolymer of propylene and another olefin, and a propylene random copolymer. Examples include coalescence. Examples of the olefin constituting the propylene-based copolymer include ethylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 4-methyl-1-pentene, 3-methyl-1-hexene and the like can be mentioned. Two or more of these may be copolymerized with propylene. The olefin content in the propylene-based copolymer is preferably 0.5 to 30% by weight, particularly 1 to 10% by weight. Furthermore, 3 to 20% by weight of a rubber component such as ethylene-propylene rubber can be mixed with the base resin.

  In addition, inorganic pigments such as chromate, ferrocyanide, sulfide, phosphate, carbon and silicate, organic pigments such as azo, phthalocyanine, quinacridone and dioxazine and other dyes are used as the base resin. 0.01 to 5% by weight of a colorant comprising 0.1 to 2 of an antistatic agent such as glycerin fatty acid ester, sorbitan fatty acid ester, N, N-bis (hydroxyethyl) -N-alkylamine, and alkylsulfonic acid. % By weight, 0.01-2% by weight of hindered amine light stabilizer, benzotriazole ultraviolet absorber, phenolic antioxidant, phosphorus antioxidant, etc., carbon black, silver powder, nickel powder, graphite, 1-20% by weight of conductivity imparting agents such as aluminum flakes, flame retardants, bubble regulators, fluidity improvers, thermal stabilizers, inorganic fillers, etc. It is preferable to appropriately blended according to necessity.

The propylene-based resin preferably has a drawdown property of 60 m / min or less, particularly 30 m / min or less. When the drawdown property exceeds 60 m / min, a corrugate is likely to occur when an attempt is made to obtain a foam having a density of 0.045 to 0.30 g / cm ³ by extrusion foaming, and the surface tends to have many surface irregularities. The drawdown property of the propylene-based resin can be adjusted by the number and length of long chain branches. In general, as the number of long chain branches increases and the branch length increases, the drawdown property tends to decrease.

  A propylene resin having a drawdown property of 60 m / min or less is a low-temperature decomposition type (decomposition temperature is lower than a normal crystalline linear propylene resin containing an atactic component and / or an isotactic component that is not crystallized. Add a peroxide from room temperature to about 120 ° C. and heat to 120 ° C. or less to bond atactic or / and non-crystallized isotactic components as branched chains to the main chain of the propylene resin. It is obtained by the method.

  Examples of the low-temperature decomposition type peroxide include di (s-butyl) peroxydicarbonate, bis (2-ethoxy) peroxydicarbonate, dicyclohexylperoxydicarbonate, di-n-propylperoxydicarbonate, di- Examples thereof include n-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-amyl peroxyneodecanoate, t-butyl peroxypivalate and the like.

  The drawdown property of the propylene-based resin is such that a melted 230 ° C. resin is injected from a melt indexer nozzle (port diameter 2.095 mm, length 8 mm) with a piston pressing speed of 10 mm / min. It is the winding speed when the string-like resin is cut when it is extruded into a string shape and the winding speed of the winding roll is gradually increased to wind up. The propylene resin constituting the foam is preferably one having a melt tension of 10 g or more. Melt tension was determined by applying a 230 ° C. resin from a melt indexer nozzle (2.095 mm in diameter, 8 mm in length) to a piston pressing speed of 10 mm / min. The value is detected by the load cell connected to the movable pulley that is first applied to the extruded string-like resin, and the load cell is detected by gradually increasing the winding speed of the string-like resin. The value when the value is stable.

  In the present invention, the propylene-based resin foam is preferably a non-crosslinked one based on a propylene-based resin that mainly satisfies the conditions of the drawdown property and the melt tension. Non-crosslinked foams are preferred because they are excellent in recyclability and productivity. In the present invention, the term “non-crosslinked” includes those that have been finely crosslinked to improve melting characteristics. Specifically, even a gel fraction of less than 5% by weight is included in the non-crosslinking range referred to in the present invention. The gel fraction was extracted in boiling xylene for 15 hours, filtered through a 75 μm mesh screen of JIS Z8801 (1995), and the insoluble matter was dried under reduced pressure for 24 hours to obtain the remaining amount of extraction (g). The percentage of the remaining resin extraction (g) with respect to the weight (g) before extraction is obtained.

  The above-mentioned propylene-based resin can be used as a base material resin of a foam by mixing other resins as necessary, but it is preferable that the drawdown property of the mixture does not exceed 60 m / min. Examples of resins that can be mixed and used include propylene resins having a drawdown property exceeding 60 m / min, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene- Examples include polyethylene resins such as butene copolymers and ethylene-maleic anhydride copolymers, polybutene resins, polyvinyl chloride, polyvinyl chloride resins such as vinyl chloride-vinyl acetate copolymers, and polystyrene resins. .

  As the propylene-based resin constituting the surface layer 3 laminated on the core layer 2 made of the propylene-based resin foam, the above-described propylene-based resin having drawdown property and melt tension may be used. From the aspect, it is preferable to use other propylene-based resins. Moreover, in order to make the foamed laminated flat plate of the present invention more excellent in rigidity and surface smoothness, it is preferable to contain 5 to 30% by weight of an inorganic filler in the propylene-based resin constituting the surface layer 3. When the surface layer is a multilayer, it is preferable in terms of surface smoothness that the base resin constituting the outermost layer contains an inorganic filler. Examples of the inorganic filler include talc, magnesium carbonate, calcium carbonate, magnesium sulfate, silica, clay, zeolite, alumina, and magnesium hydroxide.

Further, the base resin constituting the surface layer 3 is made of inorganic pigments such as chromate, ferrocyanide, sulfide, phosphate, carbon, silicate, azo, phthalocyanine, quinacridone, dioxazine, etc. 0.01 to 5% by weight of a colorant comprising an organic pigment or other dye, an antistatic agent such as glycerin fatty acid ester, sorbitan fatty acid ester, N, N-bis (hydroxyethyl) -N-alkylamine, alkylsulfonic acid 0.1-2% by weight, hindered amine light stabilizers, benzotriazole ultraviolet absorbers, phenolic antioxidants, phosphoric antioxidants, etc. 0.01-2% by weight, carbon black, silver powder 1-20% by weight of conductivity imparting agents such as nickel powder, graphite, aluminum flakes, etc., flame retardants, bubble regulators, fluidity improvers, thermal stability It is preferable to appropriately blended as required and the like.
Alternatively, a film in which indium oxide is formed as the conductive surface layer can be used.
The surface layer 3 is not limited to a single layer, and may be made of a multilayer polypropylene resin in which a polypropylene resin or the like containing an inorganic filler such as talc is laminated.

As the most preferred specific example of the present invention, the case where the surface layer made of the non-foamed propylene resin film is laminated on the core layer made of the propylene resin foam has been described as above. The surface layer has a density of 0.3 g / Even if it is a propylene resin low foam exceeding cm ³ , preferably a propylene resin low foam of 0.45 g / cm ³ or more, the intended object in the present invention can be achieved. In the present invention, the surface layer is composed of a propylene-based resin film or a low-foamed propylene resin film. Therefore, unless a special additive is added, the density of the propylene-based resin itself as the base material is the density of the surface layer. The upper limit of.
A surface layer made of a low foam can be obtained by coextrusion with a resin constituting the core layer by appropriately adding a heat decomposable foaming agent such as azodicarbonamide, a volatile foaming agent or the like to the base resin. it can.

The propylene-based resin foam laminated flat plate 1 of the present invention has a density of the propylene-based resin extruded foam constituting the core layer 2 of 0.045 to 0.30 g / cm ³ and a closed cell ratio of 50% or more . The basis weight of the unstretched propylene-based resin film layer constituting 3 is in the range of 60 to 300 g / m ² , the density of the entire foamed laminated flat plate 1 is 0.10 to 0.35 g / cm ³ , and the total thickness is 2 to 10 mm. Although it is in
Further, the center line average roughness of the surface of the foamed laminated flat plate is 5 μm or less, and the bending strength of the foamed laminated flat plate 1: F (kgf) and the basis weight of the foamed laminated flat plate 1: Y (g / m ² ) The following F ≧ 2.5 × 10 ⁻³ × Y−0.15 (1)
It is necessary that the relationship

In the foam laminate flat plate 1 of the present invention, to be insufficient in rigidity when the density of the core layer 2 is less than 0.045 g / cm ^2, light weight if the density exceeds 0.30 g / cm ³ , Secondary workability and buffering properties are insufficient. The density of the core layer 2 is particularly preferably 0.07 to 0.18 g / cm ^{3 in} terms of moldability, light weight, and workability. Further, when the density of the foam laminated flat plate 1 is less than 0.10 g / cm ³ , the rigidity is insufficient, and when it exceeds 0.35 g / cm ³ , the lightness, the secondary workability, and the buffering property are reduced. It will be insufficient. Further, when the thickness of the foam laminate 1 is less than 2 mm, the rigidity is insufficient, and when it exceeds 10 mm, the secondary workability is insufficient.

Value of the center line average roughness Te present invention odor is determined by a center line average roughness measurement of JIS B0601. Incidentally, foamed center line average roughness of the laminate plate 1 of the present invention is assumed to be measured for the surface layer 3 which is laminated to the core layer 2, the measured value of each surface because it has a surface layer 3 on both sides in the present invention Must satisfy the specified value.

  In addition, the density of the propylene-type resin extrusion foam which comprises the core layer 2 of the foaming laminated flat plate 1, and the basic weight of the unstretched propylene-type resin film which comprises the surface layer 3 can be measured as follows.

  First, the total basis weight of the foamed laminated flat plate 1 is determined from a sample obtained by cutting the foamed laminated flat plate 1 into a square of 10 cm in length and 10 cm in width at an arbitrary position. Then, the cut surface in the thickness direction of the foamed laminated flat plate 1 is magnified with a microscope to measure the thickness of any 10 points of the core layer 2 and the surface layer 3, and the average value of the measured values is the core layer 2 and the surface layer. The basis weight of the surface layer 3 is determined from the raw material density of the propylene-based resin constituting the surface layer 3 and the thickness of the surface layer 3. Further, a value obtained by subtracting the basis weight of the surface layer 3 from the total basis weight of the foamed laminated flat plate 1 can be obtained as the basis weight of the core layer 2.

If the basis weight of the unstretched propylene resin film constituting the front surface layer 3 is 60~300g / m ^2, the center line average roughness of the surface the surface layer 3 as described above is that is laminated 5μm or less, Preferably, it is 3 μm or less, and the formula (1) needs to be established between the bending strength of the foamed laminated flat plate 1: F (kgf) and the basis weight of the foamed laminated flat plate 1: Y (g / m ² ). is there. If the basis weight of the film is less than 60 g / m ² , the rigidity may be insufficient. On the other hand, if the basis weight of the film exceeds 300 g / m ² , secondary workability and light weight There is a bug. In addition, when the relationship between the bending strength and the basis weight does not satisfy the formula (1), an improvement effect in terms of rigidity cannot be expected. In addition, the effect similar to the case of the flat plate which laminated | stacked the above-mentioned low basic weight film is acquired by limiting centerline average roughness.

  In the present invention, the bending strength of the foamed laminated flat plate 1 conforms to JIS K7203, the test piece width is 25 mm, the test piece thickness is the total thickness of the foamed laminated flat plate, the fulcrum distance is 50 mm, and the test speed is 10 mm / min. Measure the bending strength in the extrusion direction and width direction of the flat plate with the arithmetic average value as the bending strength, find the bending strength of the front and back surfaces of the flat plate, The bending strength of the plate.

The density of the propylene-based resin foam constituting the core layer 2 is 0.045 to 0.30 g / cm ³ and the closed cell ratio is 50% or more , and the density of the entire foamed laminated flat plate 1 is 0.10 to 0. .35 g / cm ³ , the total thickness is 2 to 10 mm, and the basis weight of the unstretched propylene-based resin film constituting the surface layer 3 is 60 to 300 g / m ² , and the center of the surface of the foamed laminated flat plate Foam in which the relationship of the above equation (1) is established between the line average roughness of 5 μm or less, the bending strength of the foamed laminated flat plate 1: F (kgf) and the basis weight of the foamed laminated flat plate 1: Y (g / m ² ). laminating the flat plate 1 are obtained by co-extrusion, the case of producing by co-extrusion method can be laminated surface layer 3 at the same time on both sides of the plate, also are obtained found to have a sufficient thickness.

In the foamed laminate plate 1 of the present invention, propylene-based resin foam constituting the core layer 2 is closed cell ratio of 50% or more, and particularly preferably 65% or more. When the closed cell ratio of the propylene-based resin foam constituting the core layer 2 is 50% or more, the rigidity and toughness of the core layer 2 are improved, and thus the physical properties such as the rigidity of the obtained foamed laminated flat plate are improved. A propylene-based resin foam having a closed cell ratio of 50% or more can be easily obtained by the above-described coextrusion method. Incidentally, it closed cell ratio of the foam, in compliance with ASTM D2856 by using an air comparison type specific gravity meter, was determined by the following equation (3).

Closed cell ratio (%) =
{[Vx−Va (ρf / ρs)] / [Va−Va (ρf / ρs)]} × 100 (3)
However, in the above (3), Vx is the actual volume of the foam sample (the volume of the resin constituting the foam samples, the sum of the bubbles the entire volume of the closed cells portion of the foam sample) (cm ^3), Va is the apparent foam sample volume ^(cm 3), ρf is the apparent density of the foam sample (g / ^cm 3), ρs is the density of the resin (g / cm ^3).

In addition, the foamed laminated flat plate 1 of the present invention preferably has a 10% compressive strength of less than 10 kg / cm ² in terms of buffering properties. The 10% compressive strength is 50 mm in length, 50 mm in width, and a test piece prepared by laminating so as to have a thickness of about 25 mm is measured with a universal testing machine (Orientec Co., Ltd .: Tensilon, etc.) 10 mm / min. And 10% compression, and the stress value at that time is adopted.

In the present invention, the term “non-stretched” of the unstretched propylene-based resin film constituting the surface layer 3 is used for differentiating the film constituting the surface layer 3 and the stretched film in the present invention. is there. As one index of “non-stretched” in the present invention, the basis weight of the film is between X (g / m ² ) and the tensile strength of the film: E (kgf / cm) (2) A film that satisfies the formula is preferred.
E <0.07X (2)

Between the basis weight and the tensile strength of the non-stretched propylene resin film constituting the surface layer 3, to ensure that the (2) equation of relationship is satisfied, by co-extrusion, by forming the surface layer 3 good. The tensile strength of the film was determined by measuring a test piece of 50 mm long × 10 mm wide × film thickness using a tensile tester between chucks of 30 mm and a tensile speed of 200 mm / min. The breaking strength was determined in the extrusion direction and the width direction, and the arithmetic average value of the breaking strength in the extrusion direction and the width direction of the film was taken as the tensile strength of the film.

  The foamed laminated flat plate 1 of the present invention is excellent in surface rigidity, appearance, lightness, workability, cleanability, toughness, and sufficient rigidity depending on the basis weight of the surface layer, and is particularly suitable as a material for a returnable box. However, it is not limited to use as a material for returnable boxes, but can also be used as a core material for bags, bags, school bags, etc. Can be used. For example, a holder portion for storing a pen or the like can be formed by thermoforming and used as a bag or a partition plate in a bag. Further, a resin layer other than polypropylene resin, an aluminum foil layer, or the like can be further laminated and bonded to the foamed laminated flat plate 1.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
Examples 1 to 3
As a propylene resin for constituting the core layer, a propylene homopolymer (PF814) manufactured by Montel is used, and as a propylene resin for constituting the surface layer, a propylene resin having a heat distortion temperature shown in Table 1 is used. It was. In the extruder, a mixture of isobutane and normal butane (weight ratio 1: 2) in the amount shown in Table 2 was added to the propylene resin constituting the core layer to form a foamable melt, while the others The non-foamable melt composed of the propylene-based resin containing talc shown in Table 1 is formed in the propylene-based resin constituting the surface layer in the extruder, and the non-foamable melt is laminated on both sides of the foamable melt. As described above, after the two are merged inside the co-extrusion annular die, the laminated foam is obtained by extruding the annular die into a tubular shape to form a tubular foam, and then cutting the tubular foam along the extrusion direction. Both sides were heated in a heating furnace and taken up with a roll. The surface temperature of the laminated foamed flat plate immediately after coming out of the heating furnace was measured with a far-infrared thermometer attached to the outlet of the heating furnace, and this temperature is shown in Table 2 as the heating temperature of the laminated foam surface. . Thus, the laminated foam flat plate which has a surface layer on both surfaces of a core layer was obtained. Table 2 shows the properties of the obtained laminated foamed flat plate.

※１：筒状発泡体の外側に位置していた側の面
※２：筒状発泡体の内側に位置していた側の面
※３：発泡平板表面の中心線平均粗さ（μｍ）

* 1: Surface on the outside of the cylindrical foam
* 2: Surface on the inner side of the cylindrical foam * 3: Center line average roughness (μm) on the surface of the foam plate

Comparative Example 1
The same resin as in Example 3 was used as a propylene-based resin for constituting the core layer and the surface layer. In the extruder, by adding the same blowing agent as in Example 1 in an amount shown in Table 2 in propylene resin constituting the core layer to form a foamable melt was extruded from the circular die into a cylindrical shape. In another extruder, the non-foamable melt is formed by melting the propylene-based resin for constituting the surface layer containing talc shown in Table 1, and the extruded foamed cylindrical foam is cut open. One side of the foam was extruded from a T-die and laminated, then both sides of the laminated foam were heated in a heating furnace and taken up with a roll. In this way, a laminated foamed flat plate having a surface layer on one side of the core layer was obtained. Table 2 shows the properties of the obtained laminated foamed flat plate.

Comparative Example 2
A propylene homopolymer (PF814) manufactured by Montel Co., Ltd. was used as the propylene-based resin for constituting the core layer, and the amount shown in Table 2 in the propylene-based resin constituting the core layer in the extruder was the same as in Example 1. A foaming melt was obtained by adding a foaming agent, extruded from a circular die into a cylindrical shape, and then cut into a sheet-like polypropylene resin foam, which was wound into a roll. Next, the roll-shaped foam was heated and stretched to obtain a foamed flat plate. In Comparative Example 2 , no film was laminated on the foamed flat plate.
Table 2 shows the properties and the like of the obtained foamed flat plate.

Comparative Example 3
As a propylene-based resin for constituting the core layer, a propylene homopolymer (PF814) manufactured by Montel Co., Ltd. was used, and the amount of propylene-based resin constituting the core layer in the extruder was the same as in Example 1 in the amount shown in Table 2. The foaming material was added to obtain a foamable melt, extruded from a circular die into a cylindrical shape, and then cut open to obtain a foamed sheet. Table 2 shows the properties and the like of the obtained foamed sheet.

Example 4-5
As the propylene resin for constituting the core layer, the propylene resin SD632 manufactured by Montel was used, and as the propylene resin for constituting the surface layer, the propylene resin having the heat distortion temperature shown in Table 3 was used. A laminated foamed flat plate was obtained in the same manner as in Examples 1 to 3 except that the additives A and B shown below were added to the constituent resins in the amounts shown in Table 4 . Table 4 shows properties of the obtained laminated foamed flat plate.

添加剤Ａ：着色剤；フタロシアニンブルー３０重量％マスターバッチ
添加剤Ｂ：帯電防止剤；グリセリンモノステアレートとジエタノールアミンとの重量比（１：１）混合物の１５重量％マスターバッチ

Additive A: Colorant; phthalocyanine blue 30% by weight masterbatch additive B: Antistatic agent; 15% by weight masterbatch of glycerin monostearate to diethanolamine mixture (1: 1)

In Example 4 , even if the core layer foam was not colored, a cleanly colored laminated foamed flat plate was obtained only by adding a colorant to the surface layer. Accordingly, the amount of colorant used can be reduced, and the cost can be reduced. Further, the adverse effect on the foaming by the colorant is eliminated.
The laminated foamed flat plate obtained in Example 5 was stored in a constant temperature and humidity chamber at 23 ° C. and 50% RH, and the surface specific resistance of the laminated foamed flat plate was measured using TR8601 type HIGH MEGOHM METER (manufactured by Takeda Riken Kogyo). However, it was 5 × 10 ¹¹ Ω after 1 week and 7 × 10 ¹¹ Ω after 2 months. Accordingly, a laminated foamed flat plate that has been subjected to antistatic treatment can be obtained simply by putting the antistatic agent into the surface layer, so that the amount of antistatic agent used can be reduced, the cost can be reduced, and foaming by the antistatic agent can be achieved. There is no adverse effect.

Example 6
As a propylene resin for constituting a core layer, a propylene homopolymer PF814 made by Montel and a propylene resin SD632 made by Montel (weight ratio 1: 1) are used, and a propylene based for making a surface layer A laminated foamed flat plate as in Examples 1 to 3 , except that a propylene-based resin having a heat distortion temperature shown in Table 3 was used as the resin, and the amount of the additive C shown below was added to the resin constituting the surface layer as shown in Table 4. Got. Table 4 shows properties of the obtained laminated foamed flat plate.
Additive C: Weathering agent; Sanol LS770, hindered amine light stabilizer (bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate) manufactured by Sankyo

The laminated foamed flat plate obtained in Example 6 and a comparative laminated foamed flat plate having the same basis weight, density and thickness as in Example 6 except that no weathering agent was added as a comparison were subjected to a weathering tester (Shimadzu Xenon) under the conditions shown below. The tester was placed in a tester XW150 (manufactured by Shimadzu Corporation) for 10 days, and the decrease in tensile strength was measured.
Conditions: 40 ° C., 50% RH, water injection for 12 minutes during 60 minutes irradiation, lamp range 2 (10 times acceleration)
Sample size: 45 (width direction) x 130 (extrusion direction) mm
The tensile strength was measured according to JISK6767 using a dumbbell-shaped test piece at a tensile speed of 500 mm / min. As a result, the tensile strength after the weathering test of the laminated foamed flat plate to which the weathering agent of Example 6 was added was 46 kgf / cm ² , and the strength retention rate against the laminated foamed flat plate not put into the weathering test machine was 82%. .
On the other hand, the tensile strength after the weathering test of the comparative laminated foamed flat plate was 24 kgf / cm ² , and the strength retention rate against the laminated foamed flat plate that could not be put in the weathering test machine was 43%. Therefore, it is possible to obtain a laminated foamed flat plate having excellent weather resistance simply by adding the weathering agent to the surface layer, so that the amount of weathering agent used can be reduced, the cost can be reduced, and the adverse effect on foaming by the weathering agent can be reduced. Disappear.

※１：筒状発泡体の外側に位置していた側の面
※２：筒状発泡体の内側に位置していた側の面

* 1: Surface on the outer side of the cylindrical foam * 2: Surface on the inner side of the cylindrical foam

In addition, the measurement of the center line average roughness is performed in the extrusion direction and the width direction on each measurement surface of the laminated foamed flat plate or the foamed flat plate, and the arithmetic average value of the center line average roughness in the extrusion direction and the width direction is measured. The center line average roughness.
Moreover, the measurement of the heating temperature of the foam surface was measured using THRMO-HUNTER MODEL PT-3LF made from OPTEX.

1 Propylene-based resin foam laminated flat plate 2 Core layer 3 Surface layer

Claims (3)

A propylene-based resin foam laminated flat plate in which a surface layer made of an unstretched propylene-based resin film is laminated and integrated on both surfaces of a core layer made of a propylene-based resin extruded foam,
The foam laminated flat plate is obtained by coextrusion and foaming of the propylene resin foamable melt constituting the core layer and the propylene resin non-foamable melt constituting both surface layers to laminate the core layer and the surface layer together. Formed by the laminating method
The foamed laminated flat plate has a density of 0.045 to 0.30 g / cm ³ of a propylene-based resin extruded foam constituting the core layer and a closed cell ratio of 50% or more . The basis weight of the resin film layer is 60 to 300 g / m ² , the density of the entire foamed laminated flat plate is 0.10 to 0.35 g / cm ³ , and the overall thickness is 2 to 10 mm.
And with a center line average roughness of the surface of the foam laminate flat is 5μm or less, the bending strength of the foamed laminate flat: the F (kgf), the basis weight of foam stacked flat: between Y (g / m ²⁾ A propylene-based resin foam laminated flat plate characterized by the following formula (1):
F ≧ 2.5 × 10 ⁻³ × Y−0.15 (1) The following equation (2) holds between the tensile strength of the unstretched propylene-based resin film constituting the surface layer: E (kgf / cm) and the basis weight of the film: X (g / m ² ). The propylene-based resin foam laminated flat plate according to claim 1, wherein
E <0.07X (2) The propylene-based resin foam laminated flat plate according to claim 1 or 2 , wherein the propylene-based resin constituting the surface layer contains 5 to 30% by weight of an inorganic filler.

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