JPWO2012105237A1 - Polyolefin resin laminated foam sheet - Google Patents

Abstract

The present invention is a laminated foam sheet laminated by at least one surface of a polyolefin-based resin foam layer by a coextrusion method using an annular die so that the antistatic layer becomes a surface layer, and the antistatic layer comprises: It consists of 25% by weight or more and less than 70% by weight of a thermoplastic resin and more than 30% by weight of a polymeric antistatic agent and 75% by weight or less (however, the total of both is 100% by weight). When the melt viscosity at a shear rate of 100 s-1 is 250 Pa · s or more, the amount of lamination of the antistatic layer is 5 g / m 2 or more per side of the foam layer, and 10 kV is applied to the surface of the antistatic layer for 30 seconds. A laminated foam sheet having an initial electrostatic voltage of 50 V or less, excellent static dissipating properties, and excellent thermoformability.

Description

  The present invention relates to a polyolefin resin laminated foam sheet in which an antistatic layer is laminated on at least one surface of a polyolefin resin foam layer, and more particularly to a polyolefin resin laminate foam sheet having high antistatic performance.

  Conventionally, polyolefin resin foam sheets are widely used in various containers, returnable boxes, storage boxes, and the like. However, the polyolefin-based resin foam sheet is easily charged with static electricity, and dust and dust are easily attached thereto. For this reason, when a polyolefin resin foam sheet is used in a field where countermeasures against static electricity are required, various antistatic agents are added to impart antistatic properties.

  There are two types of antistatic agents: low molecular type and high molecular type, and low molecular types include fatty acid monoglyceride and sodium alkylbenzene sulfonate. These are antistatic by bleeding out on the surface of the sheet. Although the effect is exhibited, there is a problem in the sustainability of the antistatic performance, and there is a problem of contaminating the package.

In order to solve the above problems caused by the low molecular weight antistatic agent, for example, Patent Document 1 proposes a polyolefin-based resin laminated foam sheet having a thermoplastic resin layer added with a high molecular weight antistatic agent as the outermost layer. Has been.
The polyolefin resin laminated foam sheet described in Patent Document 1 has sufficient antistatic performance required for a returnable box, a general electronic component transport tray, and the like. However, some electronic parts packaging materials and the like are required to have a higher level of antistatic performance, leaving room for improvement in terms of stably developing a high level of antistatic performance. .

  On the other hand, in the foamed sheet for thermoforming, Patent Document 2 shows a decrease in antistatic performance when thermoforming a polyolefin-based resin laminated foamed sheet having an antistatic layer, and the antistatic performance during thermoforming. In order to reduce the deterioration of the antistatic agent, the melting point of the polymer antistatic agent is in the range of the melting point of the polypropylene resin containing the antistatic agent ± 20 ° C., and the polypropylene resin foam layer containing the antistatic agent There has been proposed an antistatic polypropylene-based resin laminated foam sheet laminated on the substrate. However, even the foamed sheet described in Patent Document 2 could not achieve the high level of antistatic performance desired in the above-mentioned application.

  Patent Document 3 discloses that a high molecular weight crystalline polypropylene polymer having an intrinsic viscosity of 5 dl / g or more and an intrinsic viscosity of 3 dl / g or less are used to improve antistatic properties using a polymer type antistatic agent. An antistatic resin composition comprising a low molecular weight polypropylene polymer and 20 to 60% by weight of a polypropylene resin having a total intrinsic viscosity of 3 to 10 dl / g and a polymer type antistatic agent of 40 to 80% by weight. A multilayer sheet made of a thermoplastic resin in which an antistatic layer made of the antistatic resin composition is laminated on a thermoplastic resin layer is disclosed.

  The melt of the antistatic resin composition containing a large amount of the polymeric antistatic agent described in Patent Document 3 and the foamable resin melt are cyclic so that the resin layer containing the antistatic agent is on the surface. Attempts to produce a co-extruded laminated foam sheet with a die resulted in holes and cracks in the resin layer, making it difficult to obtain a laminated foam sheet having a resin layer with a uniform thickness.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-136651 Patent Document 2: Japanese Patent Application Laid-Open No. 2006-35832 Patent Document 3: Japanese Patent Application Laid-Open No. 2008-270431

  In view of the above situation, the first object of the present invention is to provide a polyolefin-based resin laminated foam sheet that exhibits high antistatic properties that are hardly charged or not charged at all, that is, exhibits static dissipating properties. To do.

  The second aspect of the present invention is a polyolefin-based resin laminated foam sheet that exhibits static dissipative properties for thermoforming, and the third aspect of the present invention is an electrostatic dissipative property formed by thermoforming a polyolefin-based resin laminated foam sheet. A polyolefin resin foam molded article is provided.

The gist of the present invention is as follows.
(1) A laminated foamed sheet laminated on at least one surface of a polyolefin-based resin foam layer by a co-extrusion method using an annular die so that the antistatic layer becomes a surface layer, It is composed of 25% by weight or more and less than 70% by weight of a plastic resin and more than 30% by weight and 75% by weight or less of a polymer type antistatic agent (however, the total of both is 100% by weight). When the melt viscosity at a shear rate of 100 s ⁻¹ is 250 Pa · s or more, the lamination amount of the antistatic layer is 5 g / m ² or more per side of the foam layer, and 10 kV is applied to the antistatic layer surface for 30 seconds. The polyolefin resin-laminated foam sheet is characterized by having an initial charged voltage of 50 V or less.

(2) The polyolefin according to (1) above, wherein the antistatic layer has a melt viscosity of 350 Pa · s or more at 190 ° C. and a shear rate of 100 s ⁻¹ and a melt elongation of 175 ° C. of 60 m / min or more. -Based resin laminated foam sheet.

(3) The ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction of the laminated foam sheet and the ratio of the average bubble diameter in the extrusion direction to the average bubble diameter in the thickness direction are both 1.0 to 2.0. The polyolefin resin laminated foam sheet as described in (2) above, wherein

(4) polyolefin-based resin foam layer, the polyolefin resin laminated foam according to the above (1), which is a foamed polypropylene resin layer of the apparent density 0.06g ^/ cm ³ ~0.6g ^/ cm 3 Sheet.

(5) The polyolefin resin laminated foam sheet as described in (4) above, wherein the heat shrinkage in the extrusion direction and the width direction at 190 ° C. of the laminated foam sheet is 2% or less.

  (6) A polyolefin resin foam molded article obtained by thermoforming the polyolefin resin laminated foam sheet according to (3).

  The present invention is a polyolefin-based resin laminate foam sheet obtained by a coextrusion method using a circular die and having an antistatic layer composed of a thermoplastic resin added with a polymeric antistatic agent as an outermost layer, The antistatic layer is a polyolefin-based resin laminated foam sheet that exhibits excellent electrostatic dissipative properties such that it is hardly charged or not charged at all. In the present invention, the polyolefin resin laminated foam sheet for thermoforming, in particular, has a beautiful surface without causing streaks or cracks on the surface of the laminated foam sheet, and exhibits excellent electrostatic dissipation. Excellent in properties.

  The polyolefin resin laminated foam sheet of the present invention (hereinafter sometimes referred to as a laminated foam sheet) is a polymer type antistatic agent on at least one surface of a polyolefin resin foam layer (hereinafter sometimes referred to as a foam layer). A laminated foam sheet in which a thermoplastic resin layer (hereinafter sometimes referred to as an antistatic layer) containing (hereinafter sometimes referred to as an antistatic agent) is laminated.

The laminated foam sheet of the present invention is a laminated foam sheet laminated on at least one surface of a polyolefin resin foam layer by a coextrusion method using an annular die so that the antistatic layer becomes a surface layer. The prevention layer comprises 25% by weight or more and less than 70% by weight of the thermoplastic resin and more than 30% by weight and 75% by weight or less of the polymeric antistatic agent (however, the total of both is 100% by weight). The melt viscosity of the antistatic layer at 190 ° C. and a shear rate of 100 s ⁻¹ is 250 Pa · s or more, the lamination amount of the antistatic layer is 5 g / m ² or more as the basis weight, and 10 kV is applied to the antistatic layer surface for 30 seconds. It is related with the polyolefin-type resin laminated foam sheet characterized by the initial charged voltage being 50 V or less.

The laminated foam sheet of the present invention has an excellent antistatic performance such that when an applied voltage of 10 kV is applied to the surface of the antistatic layer for 30 seconds using, for example, a static one meter, the recognized initial voltage is 50 V or less. Have. An initial charging voltage of 50 V or less indicates a category of antistatic property called electrostatic dissipative property that is hardly charged. The fact that it exhibits a category of antistatic properties called static dissipating properties has a higher level of antistatic function compared to conventional antistatic products that simply have anti-dust and dust adhesion performance. Specifically, it means that it also has excellent performance that can prevent damages to be packaged such as precision electronic parts due to static electricity. In the present invention, the initial charging voltage is preferably 40 V or less, and more preferably 30 V or less. It is particularly desirable that the initial voltage is as low as possible and is 0V. The laminated foam sheet of the present invention preferably has a surface resistivity of 1.0 × 10 ¹⁰ Ω or less, more preferably 1.0 × 10 ⁷ Ω to 5.0 × 10 ⁹ Ω on the surface of the antistatic layer.

  The laminated foam sheet of the present invention preferably has an overall thickness of 0.2 to 10 mm, and more preferably 0.5 to 8 mm. If the overall thickness is less than 0.2 mm, the rigidity of the foam sheet may be insufficient depending on the application. On the other hand, if the total thickness exceeds 10 mm, depending on the application, bending workability such as a hinge of a foamed sheet, and molding workability to a box, a container or the like may be deteriorated. The thickness of the laminated foamed sheet was measured at 10 points at equal intervals with a microscope in the cross-sectional thickness in the width direction perpendicular to the extrusion direction of the foamed sheet, and the thickness of the laminated foamed sheet was measured from the photograph taken. The arithmetic average value of each measured value is taken as the thickness of the laminated foam.

  In the present invention, as a method of laminating an antistatic layer having antistatic properties on a polyolefin resin foam layer, a resin melt containing a foamable molten resin that forms a foam layer and an antistatic agent that forms an antistatic layer is used. A method of coextruding the product and forming an antistatic layer on the surface of the foamed layer is employed. As the concentration of the polymeric antistatic agent in the antistatic layer increases, the adhesion method between the antistatic layer and the foamed layer decreases with the lamination method by thermal lamination, and sufficient adhesive force cannot be obtained. Although there is a possibility, by co-extrusion method, even if the polymer antistatic agent in the antistatic layer has a high concentration, it is sufficient between the antistatic layer and the foamed layer or other resin layers. Can provide a good adhesive strength.

  As will be described later, the laminated foam sheet of the present invention is produced by a polyolefin-based resin foam layer forming extruder and an antistatic layer forming extruder. These melts are laminated in a confluence die so that the antistatic layer forming melt forms a surface layer on at least one side of the foam layer, and adjusted to the foaming temperature of the foam layer forming melt. To form a cylindrical foam through an annular die under atmospheric pressure, extend the diameter of the cylindrical foam along the cylindrical cooling pipe (cooling mandrel), The tubular foam is cut out and taken up as a sheet.

  The above-mentioned laminated foamed sheet exhibiting static dissipative properties according to the present invention is not achieved simply by adding a high-concentration antistatic agent to the antistatic layer at a high concentration, and the antistatic agent forms the antistatic layer. The antistatic agent is disposed in the antistatic layer in a state where a continuous layer is formed by dispersing the antistatic agent in a band shape, stripe shape, or network shape (hereinafter referred to as a network structure). By doing so, the effect of dissipating static electricity is demonstrated. This network structure is easily formed by applying an appropriate orientation when forming the antistatic layer. In order to form a network structure by applying this appropriate orientation, it can be obtained by two-dimensionally stretching and orientation in the width direction and the extrusion direction by a coextrusion method using an annular die. The co-extrusion method used is adopted.

  In the laminated foam sheet of the present invention, the base resin constituting the foam layer is a polyolefin resin such as a polypropylene resin or a polyethylene resin. Polyolefin resin is rich in flexibility, excellent in physical strength such as tensile strength, chemical resistance, suitable for extrusion foaming, and suitable as a base resin constituting the laminated foam sheet of the present invention. is there. In the present invention, among the polyolefin resins, a polypropylene resin having excellent rigidity and heat resistance is preferably used.

  Examples of the polypropylene resin include a propylene homopolymer, or a copolymer of propylene and a copolymerizable component copolymerizable with propylene. Examples of the copolymerizable component copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1- Examples thereof include ethylene or α-olefins having 4 to 10 carbon atoms such as heptene and 3-methyl-1-hexene. The copolymer may be a random copolymer or a block copolymer, and the copolymer is not limited to a binary copolymer, and may be a ternary copolymer. These polypropylene resins can be used alone or in admixture of two or more. Among these polypropylene resins, propylene homopolymers and ethylene-propylene block copolymers having excellent rigidity are preferably used. When the above copolymer is used as a base resin, the copolymer component is preferably contained in the copolymer in a proportion of 25% by weight or less, particularly 15% by weight or less. The preferred lower limit of the copolymer component contained in the copolymer is 0.3% by weight.

  Among the above-mentioned polypropylene resins, the base resin suitable for extrusion foaming preferably contains a polypropylene resin having a higher melt tension compared to a general polypropylene resin, and in particular, a polypropylene resin having a high melt tension. A polypropylene resin containing 15 to 50% by weight of the resin in the base resin is preferable because it combines the production cost, recyclability, and extrusion foaming suitability of the laminated foam sheet of the present invention.

The polypropylene resin having a high melt tension is, for example, (1) a polypropylene having a branching index of less than 1 and a significant strain hardening elongation viscosity described in Japanese Patent No. 2521388 and Japanese Patent No. 3406372, ( 2) (a) The Z average molecular weight (Mz) is 1.0 × 10 ⁶ or more, or the ratio (Mz / Mw) of the Z average molecular weight (Mz) to the weight average molecular weight (Mw) is 3.0 or more. (B) and the equilibrium compliance Jo is 1.2 × 10 ⁻³ m ² / N or more, or the shear strain recovery Sr / S per unit stress is 5 m ² / N or more per second ( 3) A compound containing a radical polymerizable monomer such as styrene and a radical polymerization initiator or additive is melted at a temperature higher than the reaction temperature of the radical polymerization initiator when the polypropylene resin is melted. Modified polypropylene resin, or (4) modified polypropylene resin obtained a polypropylene resin and isoprene monomer and a radical polymerization initiator and melt-kneading the like by melt-kneading.

  Examples of the polyethylene-based resin include those in which a copolymer of ethylene homopolymer or a C3-C12 α-olefin copolymerizable with ethylene is contained in the base resin in an amount of 60% by weight or more. . Specific examples include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, and ethylene-vinyl acetate copolymer. It can be used by mixing.

  In the present invention, the polyolefin resin of the base resin constituting the foamed layer is a mixture of a polypropylene resin and a polyethylene resin, and, if necessary, a mixture of the polyolefin resin with another polymer. Can be used. Other polymers include, for example, ionomers; rubbers such as ethylene-propylene rubber and styrene-butadiene rubber; styrene-butylene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-butylene-styrene blocks. Copolymer hydrogenated products, styrene-isoprene-styrene block copolymer hydrogenated products, thermoplastic elastomers such as ethylene-octene block copolymer, ethylene-butylene block copolymer; butene resin; polyvinyl chloride, vinyl chloride Examples thereof include vinyl chloride resins such as vinyl acetate copolymers; styrene resins. When these other polymers are mixed, the mixing amount is preferably 40% by weight or less of the total weight of the base resin.

  As the foaming agent used in the present invention, an inorganic physical foaming agent, an organic physical foaming agent, a decomposable foaming agent, or the like can be used. Carbon dioxide, air, nitrogen, water, etc. can be used as the inorganic physical foaming agent. Examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, n-butane, i-butane, pentane and hexane, cyclic aliphatic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane, 1,1,1,1-tetra Fluoroethane, 1,1-difluoroethane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, and methylene chloride, and ethers such as dimethyl ether and methyl ethyl ether can be used. As the decomposable foaming agent, azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate, or the like can be used. These foaming agents can be appropriately mixed and used. In the present invention, it is preferable to use a physical foaming agent in order to obtain a foam sheet having a low apparent density, and the hydrocarbon or carbon dioxide is preferably used. In particular, carbon dioxide is more preferable because there is little change in physical properties due to the remaining amount of foaming agent in the laminated foam sheet.

  The amount of the foaming agent used is generally 0.2 to 5 parts by weight with respect to 100 parts by weight of the base resin, although it depends on the apparent density of the target laminated foam sheet.

  Various additives can be added to the base resin constituting the foamed layer in the present invention, if necessary. Additives include inorganic powders such as talc and silica, acidic salts of polycarboxylic acids, bubble regulators such as a reaction mixture of polycarboxylic acid and sodium carbonate or sodium bicarbonate, talc, silica, calcium carbonate, clay Inorganic fillers such as zeolite, alumina and barium sulfate (talc and silica also have a function as a bubble regulator), heat stabilizers, ultraviolet absorbers, antioxidants, colorants and the like. Moreover, you may mix | blend an antistatic agent and an antibacterial agent.

The apparent density of the foamed layer of the laminated foamed sheet in the present invention is 0.06 g / cm from the viewpoint of physical strength such as rigidity and compressive strength and light weight, and moldability when used for thermoforming. ^{3 ~0.6g} / cm ^3, further ^{0.08g / cm 3 ~0.5g / cm 3} , it is particularly preferably ^{0.09g / cm 3 ~0.4g / cm 3} .

  In the present invention, the closed cell ratio of the foamed layer of the laminated foamed sheet is preferably 60% or more, more preferably 80% or more, from the viewpoint of mechanical properties such as rigidity and compressive strength. In the present specification, the closed cell ratio S (%) of the foam layer is measured using an air comparison type hydrometer 930 type manufactured by Toshiba Beckman Co., Ltd. in accordance with Procedure C described in ASTM D2856-70. From the true volume of the laminated foam: Vx, it is calculated by the following formula (1).

(Equation 1)
S (%) = (Vx−W / ρ) × 100 / (Va−W / ρ) (1)
However, in the above formula, Vx is the true volume (cm ³ ) measured by the above method, the volume of the resin constituting the laminated foam sheet used for the measurement, and the closed cells in the laminated foam sheet used for the measurement This corresponds to the sum of the total volume of bubbles in the part. In addition, Va, W, and ρ in the above formula are as follows.
Va: Apparent volume (cm ³ ) of the laminated foamed sheet calculated from the outer dimensions of the laminated foamed sheet used for the measurement
W: Total weight (g) of the laminated foam sheet used for measurement
ρ: Density of resin constituting the laminated foamed sheet (g / cm ³ )
A plurality of sheets are cut from the laminated foam sheet so that the length and width are 2.5 cm and the height are 4 cm, respectively, and a plurality of sheets are combined so that the apparent volume is closest to 25 cm ³ and used as a test piece. The density ρ of the resin constituting the laminated foamed sheet can be determined from the sample obtained by removing bubbles from the laminated foamed sheet by heat pressing.

The polymer type antistatic agent used in the present invention has a number average molecular weight of at least 300 or more, preferably 300 to 300,000, more preferably 600 to 150,000, and a surface resistivity of less than 1 × 10 ¹⁰ Ω. A resin, more preferably a resin smaller than a resin smaller than 1 × 10 ⁸ Ω. The polymer antistatic agent may be an inorganic salt or a low molecular weight organic protonate such as LiClO ₄ , LiCF ₃ SO ₃ , NaClO ₄ , LiBF ₄ , NaBF ₄ , KBF ₄ , KClO ₄ , KPF ₃ SO ₃ , Ca (ClO ₄ ) ₂ , Mg (ClO ₄ ) ₂ , Zn (ClO ₄ ) _{2 and the} like may be contained. The upper limit of the number average molecular weight of the polymer antistatic agent is about 500,000.

  The number average molecular weight is a number average molecular weight (polystyrene conversion value) converted using a calibration curve obtained from polystyrene having a known molecular weight using gel permeation chromatography.

  Specific examples of the polymer antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyether, polyester amide, polyether ester amide, and an ionomer such as an ethylene-methacrylic acid copolymer. Among one or a mixture of two or more selected from quaternary ammonium salts such as a coalescence, or a copolymer of two or more, and a copolymer thereof with another resin such as polypropylene, etc. Examples include resins having polar groups in the molecular chain and capable of complexing or solvating inorganic salts or low molecular weight organic protonic acid salts. May be. The upper limit of the melting point of the polymer antistatic agent is approximately 270 ° C., and the lower limit is approximately 70 ° C., preferably 80 to 230 ° C., more preferably 80 to 200 ° C. By selecting an antistatic agent having a melting point within the above range, it is relatively easy to form a good network structure while maintaining the basic physical properties of the base resin to which the antistatic agent is added. It becomes.

  Further, the crystallization temperature of the polymer antistatic agent is preferably Tc + 40 ° C. or lower based on the crystallization temperature (Tc) of the base resin constituting the polyolefin resin foam sheet. The lower limit of the crystallization temperature of the antistatic agent is approximately 60 ° C. By selecting an antistatic agent having a crystallization temperature within the above range, an antistatic agent having an excellent antistatic effect can be obtained, and particularly in appearance when the laminated foam sheet of the present invention is obtained by a coextrusion method. An excellent one is obtained.

  In the present invention, the measurement method of the melting point and the crystallization temperature of the resin constituting the antistatic agent or the resin layer is a value determined by heat flux differential scanning calorimetry (DSC) in accordance with JIS K7121-1987. Details of the measurement conditions are as follows.

  The melting point is JIS K7121-1987. A melting peak is obtained by heating the test piece whose condition was adjusted according to the condition of condition adjustment (2) of the test piece (however, the cooling rate is 10 ° C./min) at 10 ° C./min. The temperature at the top of the obtained melting peak is taken as the melting point. When two or more melting peaks appear, the temperature at the top of the melting peak on the highest temperature side is taken as the melting point.

  The crystallization temperature is JIS K7121-1987. Under the condition of condition adjustment (2) of the test piece, the temperature at the top of the exothermic peak obtained by raising the temperature at a heating rate of 10 ° C./min and lowering the temperature at a cooling rate of 10 ° C./min is the crystallization temperature And When two or more exothermic peaks appear, the temperature at the apex of the highest exothermic peak is defined as the crystallization temperature.

  Among the polymer antistatic agents used in the present invention, those mainly comprising polyether ester amide and polyether are preferred. These antistatic agents can exhibit an excellent antistatic effect without being greatly influenced by the ratio of the melt flow rate of the base resin of the antistatic layer to the melt flow rate of the antistatic agent. Furthermore, in order to improve the compatibility of the antistatic layer with the base resin in these antistatic agents and to suppress the deterioration of physical properties due to the addition of an antistatic effect and an antistatic agent, an antistatic layer is added. It is preferable to use a polymer obtained by mixing or copolymerizing an antistatic agent with a polymer excellent in compatibility with the constituting thermoplastic resin.

  The main component means that the polyether ester amide and the polyether component are contained in a proportion of 50% by weight or more, preferably 75% by weight or more, and more preferably 85% by weight or more. By using these antistatic agents to form a network structure or the like by a method described later, an antistatic layer exhibiting electrostatic dissipative properties can be formed.

  The polyether ester amide is obtained by a polymerization reaction of the polyamide (1) exemplified below and an alkylene oxide adduct (2) of bisphenols. The polyamide (1) is (a) a lactam ring-opening polymer, (b) a polycondensate of an aminocarboxylic acid, or (c) a polycondensate of a dicarboxylic acid and a diamine. Examples of the lactam of (a) include caprolactam, enantolactam, laurolactam, undecaractam and the like. Examples of the aminocarboxylic acid (b) include ω-aminocaproic acid, ω-aminoenanthic acid, ω-aminocaprylic acid, ω-aminopergonic acid, ω-aminocapric acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Etc. Examples of the dicarboxylic acid (c) include adipic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, isophthalic acid, and the diamines include hexamethylenediamine, heptamethylenediamine, octamethylenediamine, decamethylene. Examples include diamines.

  Two or more of those exemplified as the amide-forming monomer may be used. Among these, caprolactam, 12-aminododecanoic acid, adipic acid and hexamethylenediamine are preferable, and caprolactam is particularly preferable.

  As the bisphenols of the alkylene oxide adduct (2) of the bisphenols, bisphenol A (= 4,4′-dihydroxydiphenyl-2,2-propane), bisphenol F (= 4,4′-dihydroxydiphenylmethane), bisphenol S (= 4,4′-dihydroxydiphenylsulfone), 4,4′-dihydroxydiphenyl-2,2-butane and the like are mentioned, and among these, bisphenol A is particularly preferable.

  Examples of the alkylene oxide of the bisphenol alkylene oxide adduct (2) include ethylene oxide, propylene oxide, 1,2- or 1,4-butylene oxide, and a mixture of two or more of these. Of these, ethylene oxide is preferred.

  Examples of the polyether include (a) an oxyalkylene ether obtained by addition reaction of an alkylene oxide to a phenol / divinylbenzene addition polymer, (b) polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, Diglycidyl ethers such as alkylene oxide adducts of bisphenols, and hexyl, n-octyl, 2-ethylhexyl, nonyl, decyl, dodecyl, tetradecyl, octadecyl, oleyl, etc., and preferably have 6 to 22 carbon atoms. An amine compound having an aliphatic hydrocarbon group, and alkyl sulfates such as dimethyl sulfate and diethyl sulfate; alkyl carbonates such as dimethyl carbonate and diethyl carbonate; trimethyl phosphate and alkylbenzyl chlora Cationic antistatic agent consisting of a reaction product with quaternizing agents such as various phosphates or halides such as halide, benzyl chloride, alkyl chloride, and alkyl bromide, and having two or more quaternary ammonium bases in the molecule Agents and the like.

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide. Among these, ethylene oxide and a copolymer of ethylene oxide and propylene oxide are preferable. The added mole number of alkylene oxide is usually 1 to 500, preferably 20 to 300, and the oxyalkylene content in the oxyalkylene ether is 10 to 95% by weight, preferably 20 to 90% by weight, more preferably 30 to 30%. 80% by weight.

  Examples of the bisphenols include bisphenol A (= 4,4′-dihydroxydiphenyl-2,2-propane), bisphenol F (= 4,4′-dihydroxydiphenylmethane), and bisphenol S (= 4,4′-dihydroxydiphenylsulfone). ), And alkylene oxide adducts such as 4,4′-dihydroxydiphenyl-2,2-butane.

  Particularly preferred among the diglycidyl ethers are glycidyl ethers of polyoxyethylene glycol, diglycidyl ethers of ethylene oxide adducts of bisphenols, and mixtures thereof.

  Particularly preferred among the above amine compounds is N-alkyl (C 1-18) diethanolamine. Particularly preferred among the quaternizing agents are dimethyl sulfate and diethyl sulfate.

  The above-mentioned polyether ester amide or polyether has the same antistatic effect and the same kind as the thermoplastic resin constituting the antistatic layer in order to suppress deterioration of physical properties due to the addition of an antistatic agent. Alternatively, it is more preferable that a polymer having excellent compatibility, in particular, a polymer having a number average molecular weight of 800 to 25000 is mixed or copolymerized. Polyamides used here include polyamides and copolyamides derived from diamines and dicarboxylic acids and / or aminocarboxylic acids or the corresponding lactams.

  Specifically, polyamide 4, polyamide 6, polyamide 6/6, 6/10, 6/9, 6/12, 4/6, 12/12, polyamide 11, polyamide 12, m-xylylenediamine and adipic acid A polyamide obtained by adding an elastomer as needed from hexamethylenediamine and isophthalic acid and / or terephthalic acid, and a copolymer of the polyamide and the polymer, ionomer or elastomer. Examples thereof include block copolymers of polyamide and polyethylene glycol, polypropylene glycol or polytetramethylene glycol, and polyamides or copolyamides modified with ethylene-propylene rubber (EPDM) or ABS. The content of these polyamides is 50% by weight or less, preferably 25% by weight or less, and more preferably 25% by weight or less.

  In the present invention, the antistatic layer comprises 25% by weight or more and less than 70% by weight of the thermoplastic resin constituting the antistatic layer and more than 30% by weight and 75% by weight or less (the total of both is 100% by weight). . When the addition amount of the antistatic agent is 30% by weight or less, the intended electrostatic dissipation cannot be obtained. When the additive is added at a high concentration exceeding 75% by weight, the formation of the antistatic layer itself becomes difficult and the network structure of the antistatic agent cannot be formed. Absent. From such a viewpoint, the antistatic agent is preferably 33% by weight to 70% by weight, and particularly preferably 35% by weight to 65% by weight.

  Examples of the thermoplastic resin include a polyolefin-based resin, a styrene-based resin, or a mixture thereof as a base resin constituting the foam layer. Among them, it is preferable to use a polyolefin-based resin and further a polypropylene-based resin.

  In the present invention, the antistatic agent in the antistatic layer containing the polymer type antistatic agent is used at a high concentration in order to obtain electrostatic dissipative properties. On the other hand, the polymer antistatic agent has a problem that the melt viscosity is relatively low, and when the antistatic layer containing the polymer antistatic agent is formed by coextrusion, the addition of the polymer antistatic agent is performed. When the amount is large, the viscosity of the resin melt forming the antistatic layer decreases, it becomes difficult to maintain the pressure in the die during coextrusion, and it is difficult to develop good electrostatic dissipation. Further, streak cracks that are non-uniform stripe patterns in the extrusion direction of the obtained sheet may occur. This streak crack may lead to a decrease in static dissipative properties when used as a laminated foam sheet for thermoforming.

Therefore, in the present invention, the blending amount of the thermoplastic resin and the polymer type antistatic agent is adjusted, and at that time, the melt property of the mixture of the thermoplastic resin and the polymer type antistatic agent may be within a specific range. is important. That is, the antistatic layer has a melt viscosity at 190 ° C. and a shear rate of 100 s ⁻¹ of 250 Pa · s or more, and preferably 350 Pa · s or more. If the melt viscosity is 250 Pa · s or higher and the foamed layer is laminated with a specific basis weight, the desired antistatic performance with an initial voltage of 50 V or lower can be obtained. When the melt viscosity is less than 250 Pa · s, the melt viscosity of the antistatic layer-forming molten resin in the die is too low, and the intended electrostatic dissipation may not be obtained. The upper limit of the melt viscosity is about 1200 Pa · s. When the melt viscosity is high, it becomes difficult to obtain a laminated foamed sheet by coextrusion. Therefore, the melt viscosity is preferably 400 to 1000 Pa · s, more preferably 450 to 800 Pa · s.

The melt viscosity of the antistatic layer and the thermoplastic resin and polymer type antistatic agent for forming the antistatic layer should be measured using a measuring device such as Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Can do. Specifically, a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice with a nozzle diameter of 1.0 mm and a length of 10 mm were used. The cylinder and the orifice were set at a temperature of 190 ° C., and about 15 g of a measurement sample was placed in the cylinder. The melted resin is extruded from the orifice into a string shape at a shear rate of 100 sec ⁻¹ and the melt viscosity at that time is measured.

  When measuring the melt viscosity of the antistatic layer, the antistatic layer is completely cut out from the laminated foam sheet and used as a measurement sample, or only the antistatic layer is extruded under the same conditions as in the production of the laminated foam sheet. Can be used as a measurement sample.

  Further, the antistatic layer preferably has a melt elongation at 175 ° C. of 60 m / min or more, more preferably 65 m / min or more, and particularly preferably 70 m / min or more. The upper limit is about 180 m / min. When the value of the melt elongation of the antistatic layer is within the above range, the antistatic layer is stretched satisfactorily during the production by the coextrusion method of the laminated foamed sheet, so that the antistatic layer of the laminated foamed sheet has innumerable holes. It does not occur and exhibits a good appearance. In addition, when the laminated foam sheet in which innumerable holes are formed in the antistatic layer is thermoformed into a shape of a container or the like, there is a possibility that the obtained molded body has insufficient electrostatic dissipation.

  The melt elongation can be measured, for example, using a measuring apparatus such as Capillograph 1D manufactured by Toyo Seiki Seisakusho. Specifically, a cylinder with a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice with a nozzle diameter of 2.095 mm and a length of 8.0 mm were used, the set temperature of the cylinder and the orifice was 175 ° C., and about 15 g of a measurement sample was measured. Put it in the cylinder and let it stand for 5 minutes, then push the molten resin into a string from the orifice at a piston lowering speed of 10 mm / min, put this string on a pulley with a diameter of 45 mm, and take up the speed in 4 minutes. While increasing the take-up speed at a constant speed increase rate from 0 m / min to 200 m / min, the take-up speed immediately before the take-up roller pulls the string-like object and breaks the string-like object is defined as melt elongation. This measurement is performed on 10 measurement samples sampled from 10 arbitrary locations, and the arithmetic average value thereof is taken as the melt elongation in the present invention.

  In addition, the melt elongation measurement sample is prepared in the same manner as the melt viscosity measurement by completely separating the antistatic layer from the laminated foamed sheet and using it as the measurement sample, or under the same conditions as in the production of the laminated foamed sheet. It is only necessary to extrude and use as a measurement sample.

  In addition, in order to avoid the occurrence of the above-described streak cracks in the laminated foam sheet, a thermoplastic resin having a lower melt flow rate (MFR) than a thermoplastic resin conventionally used in a resin layer for coextrusion foam molding is selected. Is preferred. For example, when a polypropylene resin is selected as the resin other than the polymer antistatic agent constituting the antistatic layer, the MFR is 0.3 to 14 g / 10 minutes, further 0.6 to 12 g / 10 minutes, In particular, a polypropylene resin of 1.0 to 8 g / 10 min is preferably used.

In the antistatic layer of the laminated foam sheet of the present invention, it is necessary to make the antistatic agent present in a high concentration in the antistatic layer having a specific basis weight described later in order to exhibit electrostatic dissipative properties. Since the antistatic layer is required to have a specific melt viscosity as described above, a high viscosity thermoplastic resin is used as the thermoplastic resin constituting the antistatic layer. Further, when the laminated foam sheet is thermoformed into the shape of a container or the like, the antistatic layer needs to have a specific melt elongation in order to exhibit electrostatic dissipative properties in the obtained molded body. Is done. Therefore, kneading failure between a relatively low viscosity polymer type antistatic agent and a high viscosity thermoplastic resin is likely to occur, and it is difficult to obtain a stable melt elongation. It is preferable to sufficiently knead the agent and the thermoplastic resin. Stable melt elongation can be obtained by taking measures such as pre-compounding using a twin screw extruder. From this point of view, it is preferable that the melt elongation values of all 10 points obtained in the measurement of the melt elongation are within ± 20% of the arithmetic average value, more preferably within ± 15%, particularly preferably. Within ± 10%. If the variation exceeds ± 20%, even if the average value satisfies the above-described range, there is a possibility that perforation or the like may occur. Therefore, in order to obtain the above-described melt property antistatic layer, it is a preferable aspect not only to select materials but also to sufficiently knead.

In the present invention, the basis weight of the antistatic layer containing the antistatic agent is required to be 5 g / m ² or more per one side of the foamed layer. When the basis weight is less than 5 g / m ² , electrostatic dissipative properties cannot be obtained even if a polymer type antistatic agent is used at a high concentration. In order to achieve this electrostatic dissipation, that is, an initial charging voltage of 50 V or less, the type of the polymer antistatic agent and the concentration in the antistatic layer, the melt viscosity of the mixture of the thermoplastic resin and the polymer antistatic agent In addition, the basis weight of the antistatic layer is closely related, among which the thicker the layer is, the thicker it is, the easier it is to exhibit electrostatic dissipative properties. Can obtain electrostatic dissipative property even if it is relatively low within the above-mentioned range, but the effect is almost unchanged even if the amount of lamination is increased. Therefore, the upper limit is approximately 80 g / m ² per side. Degree. On the other hand, when the laminated amount is large, when the laminated foamed sheet is thermoformed, there is a possibility that the heat balance necessary for the thermal deformation of the foamed layer and the resin layer is too different and thermoforming becomes difficult. Therefore, stable electrostatic dissipative properties, to obtain a thermal formability, the amount laminate is preferably basis weight per one side was 10~70g / ^{m 2,} more preferably from 20 to 60 g / ^{m 2.}

  In addition, the antistatic layer can have one or more additives such as antibacterial agents and elastomers added to the base resin constituting the antistatic layer, and the laminated foam sheet of the present invention has more functionality. It can be. Examples of the antibacterial agent include those in which a metal (ion) having antibacterial activity such as silver, copper, and zinc is supported on a carrier, for example, an inorganic agent such as silver zeolite, copper zeolite, silver-supported zirconium phosphate, silver-supported silica gel , Antibacterial agents using oxide photocatalysts typified by anatase type titanium oxide, benzalkonium chloride, polyoxyethylene trialkylammonium chloride, polyhexamethylene biguanide hydrochloride, 3- (trimethoxysilyl) propyldimethyloctadecyl chloride Examples include organic chemicals such as ammonium. Moreover, the same thermoplastic elastomer as that used for the foam layer can be used as the elastomer added to the antistatic layer. The addition of this elastomer can add buffering properties to the antistatic layer.

  In the laminated foam sheet of the present invention, a resin layer (intermediate layer) containing no antistatic agent can be formed between the antistatic layer containing the antistatic agent and the foamed layer as desired. In this case, as a layer structure, the antistatic layer is formed so as to be located in the outermost layer of the laminated sheet. As the base resin for forming the resin layer not containing the antistatic agent, the same resin as the base resin constituting the foamed layer or the antistatic layer is used. In order to impart impact resistance, the base resin High density polyethylene may be selected as the resin, or a base resin containing a thermoplastic elastomer may be used. The resin constituting the resin layer, the antistatic layer, and the foamed layer is preferably a resin that exhibits sufficient thermal adhesiveness, and is inexpensive and can be laminated with a foamed layer or an antistatic layer. In order to obtain the resin layer, it is possible to use a resin layer containing the same kind of recycled raw material as the base resin of the foam layer.

When a plurality of resin layers comprising an antistatic layer and at least one resin layer (intermediate layer) are formed on at least one surface of the foam layer, the range of the total basis weight of the plurality of resin layers is the one surface of the foam layer. It is desirable to laminate at a basis weight of 20 to 250 g / m ² . If the total basis weight is too large, the closed cell ratio of the foamed layer tends to decrease, and the rigidity of the sheet may decrease. Therefore, as a lamination amount range in the case of forming a plurality of resin layers, the basis weight per side of the foamed layer is 20 to 250 g / m ² , further 30 to 210 g / m ² , particularly 40 to 180 g / m ^2. preferable.

The resin layer (intermediate layer) located between the foam layer and the antistatic layer may be foamed or non-foamed, and when foamed, the apparent density is 0.3 g / cm ³ or more, that is, low Foaming is preferred. Moreover, the thing containing a large amount of inorganic fillers may be sufficient. The laminated foam sheet of the present invention has a layer structure in which an antistatic layer containing an antistatic agent is laminated on one side, preferably both sides of the foamed layer, one side of the foamed layer, or both sides of the antistatic layer and the antistatic agent And the like in which a plurality of resin layers composed of a total of two or more of other resin layers not containing bismuth are laminated. A laminated foam sheet having a resin layer (intermediate layer) between the foam layer and the antistatic layer can improve mechanical strength such as rigidity.

  The laminated foam sheet of the present invention is suitable for use as a thermoforming sheet. The thermoforming in the present invention includes heating the laminated foamed sheet and flattening it in addition to heating the laminated foamed sheet and forming it into the shape of a container or the like using a mold.

  When the laminated foam sheet of the present invention is used as a thermoforming sheet, the ratio of the average cell diameter in the width direction to the average cell diameter in the thickness direction of the laminate foam sheet (average cell diameter in the width direction / average in the thickness direction). The ratio of the average bubble diameter in the extrusion direction to the average bubble in the thickness direction (average bubble diameter in the extrusion direction / average bubble diameter in the thickness direction) is preferably 1.0 to 2.0, More preferably, it is 1.1-1.8, Most preferably, it is 1.2-1.6. When the ratio of the average cell diameter is 1.0 to 2.0, the deformation of the molded product after thermoforming is suppressed with little distortion of the sheet.

  In the present specification, the ratio of the average bubble diameter is determined as follows. First, a vertical section in the width direction of the foam sheet is magnified with a microscope or the like. Based on the obtained image, measure the bubble diameter in the width direction and the thickness direction for all the bubbles present in the foam layer on the image, and calculate the average bubble diameter in the width direction by arithmetically averaging the measured bubble diameters, respectively. Then, the average bubble diameter in the thickness direction is obtained, and the average bubble diameter in the width direction is divided by the average bubble diameter in the thickness direction to obtain the ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction. Similarly, the average bubble diameter in the extrusion direction and the average bubble diameter in the thickness direction are obtained based on an image obtained by magnifying a vertical section of the foam sheet in the extrusion direction with a microscope or the like. By dividing by the average bubble diameter, the ratio of the average bubble diameter in the extrusion direction to the average bubble diameter in the thickness direction is obtained.

  In addition, when the foamed layer of the laminated foamed sheet of the present invention is composed of a polypropylene resin foamed layer, the heat shrinkage ratio of the laminated foamed sheet after heating at 190 ° C. for 120 seconds is 0.1 in both the extrusion direction and the width direction. ˜2% or less, more preferably 0.1 to 1.5%, and particularly preferably 0.1 to 1.0%. In the case of a laminated foam sheet having a heat shrinkage rate exceeding the above specific range, it is not possible to obtain a good molded product due to poor mold releasability and poor dimensionality during thermoforming with a mold. There is also a risk that the production efficiency will also deteriorate. On the other hand, when flattening, warping is likely to occur, and it may be difficult to obtain a good flat plate.

  In the present specification, the heat shrinkage rate in the extrusion direction of the laminated foam sheet is obtained by subtracting the post-heating dimension in the extrusion direction of the laminated foam sheet from the pre-heating dimension in the extrusion direction of the laminated foam sheet. It is a value (%) obtained by dividing by the dimension before heating in the extrusion direction and multiplying by 100. The heat shrinkage in the width direction perpendicular to the extrusion direction of the laminated foam sheet is obtained by subtracting the post-heat dimension in the width direction of the laminated foam sheet from the pre-heat dimension in the width direction of the laminated foam sheet. It is a value (%) obtained by dividing by 100 the dimension before heating in the width direction and multiplying by 100.

Apparent density of the laminated foam sheet of the present ^{invention, 0.06g / m 3 ~0.6g / m} 3, more preferably ^{0.07g / cm 3 ~0.45g / cm 3} , in particular 0.10 g / ^cm 3 ~ It is preferably 0.3 g / cm ³ . When the apparent density of the laminated foamed sheet is within the above range, it has excellent physical properties such as rigidity and compressive strength and light weight, and exhibits excellent thermoformability as a laminated foamed sheet for thermoforming. It becomes.

The manufacturing method of the polyolefin-type resin laminated foam sheet of this invention is demonstrated.
First, in the laminated foam sheet of the present invention, a polymer type antistatic agent of more than 30% by weight and 75% by weight or less is used for the antistatic layer, so that the antistatic layer forming composition has a uniform antistatic property. It is necessary to maintain the film forming property for forming the layer and to ensure that the obtained antistatic layer exhibits sufficient electrostatic dissipation. For this reason, it is important to select the polyolefin resin and antistatic layer of the foam layer constituting the laminated foam sheet of the present invention so as to satisfy the specific requirements described so far. In addition, sufficient kneading of the composition forming the antistatic layer is an important factor in obtaining a laminated foam sheet for thermoforming. If the composition for forming the antistatic layer is not sufficiently kneaded, the surface appearance of the resulting laminated foam sheet is reduced, but there is a risk of perforations and streak cracks. The molded product obtained by thermoforming such a laminated foam sheet may deteriorate the antistatic property of the antistatic layer and may not exhibit static dissipative properties.

  In addition, as a standard of the kneading | mixing degree of the composition which forms an antistatic layer, it becomes a standard whether the kneaded material is in the range of the specific melt viscosity and melt elongation mentioned above. As a means for sufficient kneading, use an extruder having a long L / D, for example, a L / D of 30 or more, or a screw equipped with a unimelt or a dull mage for increasing the degree of kneading. Is useful. Moreover, it is also possible to make up for insufficient kneading by performing pre-compounding using a twin screw extruder.

  The laminated foam sheet of the present invention is a polyolefin resin that prepares a first extruder for forming a foam layer and a second extruder for forming an antistatic layer, and forms the foam layer on the first extruder. If necessary, add other additives, melt and knead them under heating, and press the foaming agent into the melt-kneaded product from the foaming agent inlet provided in the extruder and knead Thus, a foamable resin melt containing a foaming agent is prepared. On the other hand, a thermoplastic resin for forming an antistatic layer and an antistatic agent are melt-kneaded under heating in a second extruder to prepare a melt for forming an antistatic layer. When laminating a resin layer as an intermediate layer in addition to the antistatic layer, the base resin is melt-kneaded under heating with an extruder for forming a resin layer with a third extruder, for forming the resin layer. Prepare the melt. The foamable resin melt and the antistatic layer forming melt, the foamable resin melt, the antistatic layer forming melt, and the resin layer forming melt are provided downstream of the extruder. In the die, for example, the antistatic layer forming melt is the outermost layer, such as antistatic layer / foamed layer / antistatic layer or antistatic layer / resin layer / foamed layer / resin layer / antistatic layer. Laminated, adjusted to the foaming temperature of the foamed layer-forming resin melt, and extruded through an annular die under atmospheric pressure to form a cylindrical foam. Next, a conventionally known method, for example, the cylindrical foam is expanded along the cylindrical cooling device (cooling mandrel) to increase the diameter of the cylindrical foam, and the cylindrical foam is cut open to form a sheet. A laminated foam sheet is obtained by the method described above.

  The laminated foam sheet having the antistatic layer containing the polymer type antistatic agent of the present invention at a high concentration in the outermost layer is produced by a coextrusion method using a ring die, but the polymer type antistatic agent is produced at a high concentration. By using the agent, when a laminated foam sheet is obtained by coextrusion using a circular die, the resistance between the cylindrical foam and the cooling mandrel surface increases, and the appearance of the resulting laminated foam sheet decreases. Heat shrinkage, particularly shrinkage value in the extrusion direction. Laminated foam sheets with large thermal shrinkage, for example, when a mold such as a container is obtained by a thermoforming machine, the shrinkage ratio of the laminated foam sheet is large, and after forming with a mold, it adheres to the mold and is released. Is not easily performed, and the molding cycle time is significantly increased, resulting in poor production efficiency and a poor product. Further, even in the process of making a flat plate by heating and straightening the laminated foam sheet obtained through the cylindrical cooling mandrel (flattening), the foam sheet remains strained and a good flat plate cannot be produced. It should be noted that this phenomenon is small if the polymer type antistatic agent concentration at a normal antistatic level, for example, the antistatic agent concentration in the antistatic layer is 30% by weight or less, but the antistatic agent concentration is 30% by weight The above phenomenon appears remarkably when exceeding. It was speculated that this is because the polymer type antistatic agent contains a large amount of high metal adhesion.

  The above problem is that the resistance of the cylindrical foam and the surface of the cooling mandrel is lowered by coating the surface of the cylindrical cooling mandrel with polytetrafluoroethylene (PTFE) or a metal and PTFE and coating the surface. Can be eliminated or reduced. The laminated foam sheet can also be designed by making the diameter of the cooling pipe rear side (exit side of the cylindrical foam) smaller than the diameter of the cooling pipe front side (introducing side of the cylindrical foam) and providing a taper. The generation of distortion can be eliminated and reduced.

  By adopting such means, in the method for producing a laminated foamed sheet by coextrusion using an annular die, a laminated foamed sheet having an excellent appearance can be obtained even when a polymer antistatic agent is used at a high concentration. Can be obtained. Furthermore, it is possible to reduce unnecessarily distortion of the laminated foam sheet, which is a problem when used for thermoforming, etc., to adjust the heat shrinkability of the laminated foam sheet, and to use it as a thermoforming sheet. Even within the above-mentioned range of the appropriate shrinkage rate. Thereby, the polyolefin resin laminated foam sheet for thermoforming which is excellent in moldability as well as electrostatic dissipation can be obtained.

  The present invention will be described more specifically with reference to examples. The physical properties of Examples and Comparative Examples were evaluated by the following methods.

[Melt flow rate (MFR)]
The melt flow rate was measured at a test temperature of 190 ° C. and a load of 21.18 N in accordance with the method A of JIS K7210-1999 for polyethylene resins. Moreover, about the polypropylene resin and other resin, based on A method of JISK7210-1999, it measured by the test temperature of 230 degreeC, and the load of 21.18N.

[Melt viscosity]
The melt viscosity was measured using a Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. according to the method described above. In measuring the melt viscosity of the raw material, the raw material pellet was used as it was as a measurement sample. When measuring the melt viscosity of the antistatic layer, a measurement sample was prepared by extruding only the antistatic layer in the same manner as in the production conditions of the laminated foam sheet.

[Melting elongation]
The melt elongation was measured using a capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. according to the above method. The measurement sample was prepared by extruding only the antistatic layer in the same manner as the production conditions of the laminated foam sheet.

[Ratio of average bubble diameter (bubble flatness)]
The ratio of the average cell diameter in the width direction (TD) to the average cell diameter in the thickness direction (VD) of the laminate foam sheet was determined as follows. First, the foam sheet cross section in the direction perpendicular to the extrusion direction is magnified 100 times with a microscope, and all bubbles present in the enlarged image (excluding those in which the bubbles are cut off in the middle) are targeted. The bubble diameter in the width direction and the bubble diameter in the thickness direction of each bubble were measured, and the measured values were arithmetically averaged to obtain the average bubble diameter in the width direction and the average bubble diameter in the thickness direction. This measurement is performed on five cross sections at equal intervals in the width direction of the laminated foam sheet, and the average cell diameter in the width direction and the average cell diameter in the thickness direction obtained for each cross section are respectively arithmetically averaged. The average cell diameter in the width direction of the laminated foam sheet and the average cell diameter in the thickness direction are obtained, and the average cell diameter in the width direction is divided by the average cell diameter in the thickness direction (average cell diameter in the width direction / thickness direction). Average bubble diameter). Similarly, the extrusion direction (MD) average cell diameter and the thickness direction (VD) average cell diameter of the laminated foam sheet are determined from five cross sections in the extrusion direction at equal intervals in the width direction of the laminated foam sheet, and the average of the extrusion direction is obtained. It was obtained by dividing the bubble diameter by the average bubble diameter in the thickness direction, (average bubble diameter in the extrusion direction / average bubble diameter in the thickness direction).

[Heating shrinkage]
The heat shrinkage rate of the laminated foam sheet was measured as follows. Three test pieces of 200 mm in the extrusion direction and 10 mm in the width direction are cut out from the laminated foam sheet at equal intervals in the width direction of the sheet, and these test pieces are placed on a metal tray covered with talc and placed in an oven at 190 ° C. Heated for 120 seconds. After heating, the dimensions of the foamed sheet after heating in the extrusion direction were measured, the heat shrinkage rate of each test piece was determined according to the following formula (2), and the arithmetic average value thereof was taken as the heat shrinkage rate in the extrusion direction. Moreover, also about the width direction, the test piece of the extrusion direction 10mm x width direction 200mm was cut out from the lamination foam sheet at equal intervals in the width direction of the sheet | seat, and the heat shrinkage rate of the width direction was calculated | required similarly.

(Equation 2)
Heat shrinkage rate (%) = {length of test piece before heating (200 mm) −length of test piece after heating} / length of test piece before heating (200 mm) × 100 (2)

[Initial voltage]
Measurement of the initial charged voltage of the laminated foamed sheet was performed in accordance with JIS L1094-1980 using STATIC HONESTETER made by Sisid Electric Co., Ltd. Specifically, five test pieces (40 mm × 40 mm) are cut out at equal intervals in the width direction perpendicular to the extrusion direction of the foam sheet, the test pieces are attached to the mounting frame of the measuring instrument, and the turntable is rotated. After applying (+) 10 kV for 30 seconds, the application was stopped, and the average value of the remaining charged voltage when the application was stopped was defined as the initial charged voltage.

[Surface resistivity]
The measurement of the surface resistivity of the laminated foam sheet was performed according to JIS K6911-2006. Specifically, three test pieces (length 100 mm × width 100 mm) were cut out at equal intervals in the width direction perpendicular to the extrusion direction of the foam sheet, and the test pieces were placed in an atmosphere of 23 ° C. and humidity 50% for 24 hours. After leaving, it measured using the resistance measuring device (made by HIOKI), and made the average value of the measured value the surface resistivity.

[appearance]
The appearance of the laminated foam sheet was evaluated according to the following criteria.
A: The antistatic layer is uniformly laminated.
○: The antistatic layer is laminated almost uniformly.
(Triangle | delta): The streaky pattern or the hole which becomes a problem at the time of thermoforming is seen in an antistatic layer.

Examples 1-5, 7, 9, 10, 14, 15, Comparative Examples 1, 3-5
A tandem extruder consisting of two extruders with an inner diameter of 90 mm and an inner diameter of 120 mm is used as an extruder for producing a polypropylene resin foam layer of a laminated foam sheet, and an extruder with an inner diameter of 40 mm is used as an extruder for producing an antistatic layer. An annular die having a diameter of 100 mm was used for laminating and coextruding a polypropylene resin foam layer and an antistatic layer using a machine.

  First, in order to form a polypropylene-based resin foam layer, a foam regulator (Nippon Boehringer Ingelheim Co., Ltd.) was added to 100 parts by weight of a polypropylene-based resin (manufactured by Nippon Polypro Co., Ltd., grade: FB3312) (indicated as PP7). 0.5 parts by weight of PO217K, sodium bicarbonate and sodium citrate), supplied to the raw material inlet of an extruder with an inner diameter of 90 mm, heated and kneaded, and a molten resin mixture prepared at about 200 ° C. Carbon dioxide as a foaming agent was injected into the molten resin mixture so as to be 0.4 parts by weight with respect to 100 parts by weight of the polypropylene resin, and then the inner diameter was 120 mm connected to the downstream side of the 90 mm extruder. And an expandable molten resin mixture was obtained at a discharge rate of 98 kg / hr.

  On the other hand, using the polymer type antistatic agent shown in Table 2 as the antistatic agent and the polypropylene resin shown in Table 1, the resin composition constituting the antistatic layer shown in Table 3 was extruded with an inner diameter of 40 mm. The mixture was supplied to a machine, melted and kneaded under heating, and an antistatic molten resin was obtained at a discharge rate of 14 kg / hr.

Each obtained foamable molten resin mixture and antistatic molten resin are fed into a merging die and merged, laminated so that the antistatic molten resin becomes both outer layers, co-extruded from an annular die, and antistatic from the outside Two types and three layers of cylindrical laminated foams were laminated in the order of layer / polypropylene resin foam layer / antistatic layer. Extruding the extruded cylindrical laminated foam along the cylindrical cooling pipe (diameter: 212mm, blow-up ratio: 2.12) whose slipperiness has been improved by about 2 times by blasting the anodized surface The target laminated foam sheet was obtained by cutting in the direction. The apparent density of the foamed layer is 0.27 g / cm ³ and the thickness is 2.0 mm, the thickness of the entire laminated foam sheet is 2.1 mm, the basis weight is 640 g / m ² , the apparent density is 0.31 g / cm ³ and the sheet width. It was 650 mm. Table 4 shows the physical properties of the laminated foam sheet.

Example 6
A laminated foam sheet was obtained in the same manner as in Example 1 except that the discharge amount of the antistatic molten resin was 3.5 kg / hr so that the lamination amount of the antistatic layer was 10 g / m ² . The thickness of the entire laminated foam sheet was 2.0 mm, the basis weight was 580 g / m ² , and the apparent density was 0.29 g / cm ³ . Table 4 shows the physical properties of the laminated foam sheet.

Example 8
A laminated foamed sheet was obtained in the same manner as in Example 1 except that the discharge amount of the antistatic molten resin was changed to 52.5 kg / hr so that the lamination amount of the antistatic layer was 150 g / m ² . The thickness of the entire laminated foam sheet was 2.3 mm, the basis weight was 860 g / m ² , and the apparent density was 0.38 g / cm ³ . Table 4 shows the physical properties of the laminated foam sheet.

Comparative Example 2
A laminated foam sheet was obtained in the same manner as in Example 1 except that the discharge amount of the antistatic molten resin was 0.7 kg / hr so that the lamination amount of the antistatic layer was 2 g / m ² . The thickness of the entire laminated foam sheet was 2.0 mm, the basis weight was 564 g / m ² , and the apparent density was 0.28 g / cm ³ . Table 4 shows the physical properties of the laminated foam sheet.

Example 13
A laminated foam sheet in the same manner as in Example 1 except that a cylindrical cooling device (diameter: 212 mm, blow-up ratio: 2.47) having an alumite surface not subjected to surface treatment was used, using an annular die having a diameter of 86 mm. Got. The thickness of the laminated foam sheet was 2.1 mm, the basis weight was 640 g / m ² , and the apparent density was 0.31 g / cm ³ . The sliding property in the cylindrical cooling pipe was worse than that in the case of surface treatment, and the sheet was stretched in the extrusion direction, and the sheet width was 624 mm. Table 4 shows the physical properties of the laminated foam sheet.

Examples 11 and 12
A tandem extruder consisting of two extruders with an inner diameter of 90 mm and an inner diameter of 120 mm is used as an extruder for producing a polypropylene resin foam layer of a laminated foam sheet, and an extruder with an inner diameter of 40 mm is used as an extruder for producing an antistatic layer. In order to provide a resin layer as an intermediate layer between the antistatic layer and the foam layer, an extruder with an inner diameter of 50 mm is used to laminate the polypropylene resin foam layer, the intermediate layer, and the antistatic layer. An annular die having a diameter of 100 mm was used for coextrusion.

  First, in order to form a polypropylene-based resin foam layer, a foam regulator (Nippon Boehringer Ingelheim Co., Ltd.) was added to 100 parts by weight of a polypropylene-based resin (manufactured by Nippon Polypro Co., Ltd., grade: FB3312) (indicated as PP7). 0.75 parts by weight of company-made PO217K, sodium bicarbonate, sodium citrate) is fed into a raw material inlet of an extruder with an inner diameter of 90 mm, heated and kneaded, and a molten resin mixture prepared at about 200 ° C. Carbon dioxide as a foaming agent was injected into the molten resin mixture so as to be 0.4 parts by weight with respect to 100 parts by weight of the polypropylene resin, and then the inner diameter was 120 mm connected to the downstream side of the 90 mm extruder. And an expandable molten resin mixture was obtained at a discharge rate of 98 kg / hr.

  On the other hand, a polypropylene-based resin (manufactured by Nippon Polypro Co., Ltd., grade: BC3RA) (indicated as PP4) is supplied to an extruder having an inner diameter of 50 mm, melt-kneaded, and the molten resin for the intermediate layer is discharged at a discharge rate of 28 kg / hr. Obtained.

  Further, using the polymer type antistatic agent shown in Table 2 as the antistatic agent and the polypropylene resin shown in Table 1, the resin composition constituting the antistatic layer shown in Table 3 was extruded with an inner diameter of 40 mm. Then, the mixture was melt-kneaded to obtain an antistatic molten resin at a discharge rate of 14 kg / hr.

Each of the obtained foamable molten resin mixture, intermediate layer molten resin, and antistatic molten resin is fed into a merging die and merged, and laminated so that the antistatic molten resin becomes both outer layers, and is shared from the annular die. Extrusion was performed to form a three-layer, five-layer cylindrical laminated foam in which the antistatic layer / intermediate layer / polypropylene resin foam layer / intermediate layer / antistatic layer were laminated in this order from the outside. The extruded cylindrical laminated foam is cut open in the extrusion direction while being drawn along the cylindrical cooling pipe (diameter: 212 mm, blow-up ratio: 2.12) subjected to the above-mentioned surface treatment in order to improve sliding. A laminated foam sheet was obtained. The thickness of the entire laminated foam sheet was 4.0 mm, the basis weight was 800 g / m ² , and the apparent density was 0.20 g / cm ³ . Table 5 shows the physical properties of the laminated foam sheet.

Example 16
A laminated foamed sheet was obtained in the same manner as in Example 11 except that a cylindrical cooling device (diameter 212 mm, blow-up ratio 2.47) having an anodized surface not subjected to surface treatment was used using an annular die having a diameter of 86 mm. Obtained. The thickness of the entire laminated foam sheet was 4.0 mm, the basis weight was 800 g / m ² , and the apparent density was 0.20 g / cm ³ . Table 5 shows the physical properties of the laminated foam sheet.

Examples 17 and 18
A tandem extruder consisting of two extruders with an inner diameter of 90 mm and an inner diameter of 120 mm is used as an extruder for producing a polyethylene-based resin foam layer of a laminated foam sheet, and an extruder with an inner diameter of 40 mm is used as an extruder for producing an antistatic layer. An annular die having a diameter of 100 mm was used for laminating and coextruding a polyethylene resin foam layer and an antistatic layer using a machine.

  First, in order to form a polyethylene-based resin foamed layer, a bubble regulator (Nippon Boehringer Ingelheim) was added to 100 parts by weight of a polyethylene-based resin (manufactured by Dow Chemical Japan Co., Ltd., grade: NUC8321) (denoted as LD1). 0.5 parts by weight of PO217K, sodium bicarbonate and sodium citrate blended by Co., Ltd., is supplied to the raw material inlet of an extruder with an inner diameter of 90 mm, heated and kneaded, and a molten resin prepared at about 200 ° C. An inner diameter connected to the downstream side of the 90 mm extruder by press-fitting carbon dioxide as a foaming agent into the molten resin mixture so as to be 0.4 parts by weight with respect to 100 parts by weight of the polyethylene resin. The foamed molten resin mixture was obtained by feeding to an extruder of 120 mm and a discharge rate of 98 kg / hr.

  On the other hand, using the polymer type antistatic agent shown in Table 2 as the antistatic agent and the polyethylene resin shown in Table 6, the resin composition constituting the antistatic layer shown in Table 7 was extruded with an inner diameter of 40 mm. The mixture was supplied to a machine, melted and kneaded under heating, and an antistatic molten resin was obtained at a discharge rate of 14 kg / hr.

Each obtained foamable molten resin mixture and antistatic molten resin are fed into a merging die and merged, laminated so that the antistatic molten resin becomes both outer layers, co-extruded from an annular die, and antistatic from the outside Two types and three layers of cylindrical laminated foams were laminated in the order of layer / polyethylene resin foam layer / antistatic layer. Extruding the extruded cylindrical laminated foam along the cylindrical cooling pipe (diameter: 212mm, blow-up ratio: 2.12) whose slipperiness has been improved by about 2 times by blasting the anodized surface The target laminated foam sheet was obtained by cutting in the direction. The apparent density of the foam layer is 0.31 g / cm ³ and the thickness is 2.0 mm, the thickness of the entire laminated foam sheet is 2.1 mm, the basis weight is 610 g / m ² , the apparent density is 0.29 g / cm ³ and the sheet width. It was 650 mm. Table 8 shows the physical properties of the laminated foam sheet.

Example 19
Except for using a polyethylene resin (manufactured by Nippon Polyethylene Co., Ltd., grade: HJ560W (denoted as HD2) and a mixed resin having a weight ratio of 6: 4) to form a polyethylene resin foam layer. A laminated foam sheet was obtained in the same manner as in Example 17. The apparent density of the foam layer is 0.31 g / cm ³ and the thickness is 2.0 mm, the thickness of the entire laminated foam sheet is 2.1 mm, the basis weight is 610 g / m ² , the apparent density is 0.29 g / cm ³ and the sheet width. It was 650 mm. Table 8 shows the physical properties of the laminated foam sheet.

Example 20
A tandem extruder consisting of two extruders with an inner diameter of 90 mm and an inner diameter of 120 mm is used as an extruder for producing a polyethylene-based resin foam layer of a laminated foam sheet, and an extruder with an inner diameter of 40 mm is used as an extruder for producing an antistatic layer. In order to provide a resin layer as an intermediate layer between the antistatic layer and the foamed layer, an extruder with an inner diameter of 50 mm is used to laminate the polyethylene resin foamed layer, the intermediate layer, and the antistatic layer. An annular die having a diameter of 140 mm was used for coextrusion.

  First, in order to form a polyethylene-based resin foam layer, an air bubble regulator (Nippon Boehringer Ingelheim Co., Ltd., PO217K, sodium bicarbonate, sodium citrate combination) is added to 100 parts by weight of a polyethylene-based resin (LD1). 75 parts by weight are blended, supplied to the raw material inlet of an extruder with an inner diameter of 90 mm, heated and kneaded to obtain a molten resin mixture prepared at about 200 ° C., and butane as a blowing agent in the molten resin mixture. It is press-fitted so as to be 2.45 parts by weight with respect to 100 parts by weight, and then supplied to an extruder having an inner diameter of 120 mm connected to the downstream side of the 90 mm extruder, and is foamable at a discharge rate of 100 kg / hr. A molten resin mixture was obtained.

  On the other hand, a polyethylene-based resin (mixed resin having a weight ratio of LD1 and HD2 of 3: 7) was supplied to an extruder having an inner diameter of 50 mm and melt-kneaded to obtain a molten resin for an intermediate layer at a discharge rate of 15 kg / hr.

  Further, using the polymer type antistatic agent shown in Table 2 as the antistatic agent and the polyethylene resin shown in Table 6, the resin composition constituting the antistatic layer shown in Table 7 was extruded with an inner diameter of 40 mm. Then, the mixture was melt-kneaded to obtain an antistatic molten resin at a discharge rate of 18 kg / hr.

Each of the obtained foamable molten resin mixture, intermediate layer molten resin, and antistatic molten resin is fed into a merging die and merged, and laminated so that the antistatic molten resin becomes both outer layers, and is shared from the annular die. Extruded to form a three-layer, five-layer cylindrical laminated foam laminated in the order of antistatic layer / intermediate layer / polyethylene resin foam layer / intermediate layer / antistatic layer from the outside. The extruded cylindrical laminated foam is cut open in the extrusion direction while being taken along the cylindrical cooling pipe (diameter 350 mm, blow-up ratio 2.5) subjected to the above-mentioned surface treatment to improve sliding. A laminated foam sheet was obtained. The thickness of the entire laminated foam sheet was 3.0 mm, the basis weight was 600 g / m ² , and the apparent density was 0.20 g / cm ³ . Table 9 shows the physical properties of the laminated foam sheet.

Example 21
A tandem extruder consisting of two extruders with an inner diameter of 90 mm and an inner diameter of 120 mm is used as an extruder for producing a polyethylene-based resin foam layer of a laminated foam sheet, and an extruder with an inner diameter of 40 mm is used as an extruder for producing an antistatic layer. In order to provide a resin layer as an intermediate layer between the antistatic layer and the foam layer, an extruder with an inner diameter of 65 mm is used to laminate the polyethylene resin foam layer, the intermediate layer, and the antistatic layer. An annular die with a diameter of 180 mm was used for coextrusion.

  First, in order to form a polyethylene-based resin foam layer, a cell regulator (manufactured by Nippon Boehringer Ingelheim Co., Ltd.) with respect to 100 parts by weight of a polyethylene-based resin (mixed resin of HD2 and LD1 in a weight ratio of 6: 4) 217 parts by weight of PO217K, sodium bicarbonate, and sodium citrate), which is supplied to the raw material inlet of an extruder with an inner diameter of 90 mm, heated and kneaded to obtain a molten resin mixture prepared at about 200 ° C., Butane as a foaming agent is injected into the molten resin mixture in an amount of 1.3 parts by weight with respect to 100 parts by weight of the polyethylene resin, and then into an extruder having an inner diameter of 120 mm connected to the downstream side of the 90 mm extruder. Then, a foamable molten resin mixture was obtained at a discharge rate of 100 kg / hr.

  On the other hand, a polyethylene-based resin (mixed resin having a weight ratio of LD1 and HD2 of 3: 7) was supplied to an extruder having an inner diameter of 65 mm and melt-kneaded to obtain a molten resin for an intermediate layer at a discharge rate of 38 kg / hr.

  Further, using the polymer type antistatic agent shown in Table 2 as the antistatic agent and the polyethylene resin shown in Table 6, the resin composition constituting the antistatic layer shown in Table 7 was extruded with an inner diameter of 40 mm. The mixture was supplied to a machine, melted and kneaded to obtain an antistatic molten resin at a discharge rate of 11 kg / hr.

Each of the obtained foamable molten resin mixture, intermediate layer molten resin, and antistatic molten resin is fed into a merging die and merged, and laminated so that the antistatic molten resin becomes both outer layers, and is shared from the annular die. Extruded to form a three-layer, five-layer cylindrical laminated foam laminated in the order of antistatic layer / intermediate layer / polyethylene resin foam layer / intermediate layer / antistatic layer from the outside. The extruded cylindrical laminated foam is cut open in the extrusion direction while being drawn along the cylindrical cooling pipe (diameter 350 mm, blow-up ratio 1.9) subjected to the above-mentioned surface treatment in order to improve sliding. A laminated foam sheet was obtained. The thickness of the entire laminated foam sheet was 4.0 mm, the basis weight was 1100 g / m ² , and the apparent density was 0.28 g / cm ³ . Table 9 shows the physical properties of the laminated foam sheet.

[Evaluation of thermoformability 1 (Evaluation of formability and releasability during thermoforming)]
The laminated foam sheets obtained in Examples 1 to 10, 13, 17 to 19 and Comparative Examples 3 and 5 were subjected to a single vacuum forming machine (manufactured by Asano Laboratory Co., Ltd .: FSK type) with outer dimensions of 340 mm × 240 mm, depth. Using a 43-mm component tray mold, thermoforming was performed to obtain a tray-shaped molded body. In the laminated foam sheets of Examples 1 to 10, 17 to 19, and Comparative Examples 3 and 5, molded bodies having the same shape as the mold are obtained, and there is no elongation unevenness. The mold release from the mold was good. The laminated foam sheet of Example 13 had a large resistance when the molded body was released from the mold, and the shape of the molded body collapsed when released, and the releasability was insufficient.

[Thermoformability evaluation 2 (evaluation of warpage of plate-like foam)]
The laminated foam sheets obtained in Example 11, Example 12, Example 16, Example 20, and Example 21 were placed in a heating furnace at 250 ° C. (however, in Examples 20 and 21, they were placed in a heating furnace at 200 ° C. ) To obtain a plate-like laminated foam by heating from both sides of the sheet. The warpage of the obtained plate-like foam was measured, and the thermoformability of the laminated foam sheet was evaluated according to the following criteria. It can be seen that the less the warp, the better the laminated foam sheet is in thermoformability. In addition, the measurement of the curvature of the foam was performed as follows. A square sample having a size of 500 mm × 500 mm was cut out from the vicinity of the center of the plate-like foam. The cut sample was placed on a horizontal table, and the distance from the lower surface of the sample to the upper surface of the table on which the sample was placed was measured at four points at the center of each side of the square. Next, the sample was turned over and the same measurement was performed. The largest numerical value L (mm) was adopted among the measurement results of a total of 8 points, and the warpage (%) of the plate-like foam was calculated by the following equation (3).

(Equation 3)
Warpage (%) = L (mm) / (Length of one side of square (500 mm)) × 100 (3)
In the laminated foam sheets of Example 11, Example 12, Example 20, and Example 21, the warpage was 1% or less, but in the laminated foam sheet of Example 16, the warp exceeded 1%. .

The polyolefin-based resin laminated foam sheet of the present invention exhibits excellent electrostatic dissipation such that it is hardly charged or not charged at all, has a beautiful surface, and excellent thermoformability. Compared to what is called dust and dust adhesion prevention performance, it shows a high level of antistatic function, and is useful as a thermoforming sheet for electronic parts, especially packages such as precision electronic parts. is there.

Claims (6)

A laminated foamed sheet laminated on at least one surface of a polyolefin-based resin foam layer by a coextrusion method using an annular die so that the antistatic layer becomes a surface layer, and the antistatic layer comprises a thermoplastic resin 25 The polymer type antistatic agent exceeds 30% by weight and exceeds 75% by weight (however, the total of both is 100% by weight). The antistatic layer has a temperature of 190 ° C. and a shear rate of 100 s. The initial band when the melt viscosity at ^-1 is 250 Pa · s or more, the amount of lamination of the antistatic layer is 5 g / m ² or more per side of the foam layer, and 10 kV is applied to the surface of the antistatic layer for 30 seconds. A polyolefin-based resin laminated foam sheet having a voltage of 50 V or less. 2. The polyolefin-based resin laminate foam according to claim 1, wherein the antistatic layer has a melt viscosity of 350 Pa · s or more at 190 ° C. and a shear rate of 100 s ⁻¹ and a melt elongation at 175 ° C. of 60 m / min or more. Sheet.   The ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction of the laminated foam sheet and the ratio of the average bubble diameter in the extrusion direction to the average bubble diameter in the thickness direction are both 1.0 to 2.0. The polyolefin-based resin laminated foam sheet according to claim 2. Polyolefin-based resin foam layer, the polyolefin resin laminated foam sheet as claimed in claim 1, characterized in that the foamed polypropylene resin layer of the apparent density ^{0.06g / cm 3 ~0.6g / cm 3} .   The polyolefin resin laminated foam sheet according to claim 4, wherein the heat shrinkage in the extrusion direction and the width direction at 190 ° C of the laminated foam sheet is 2% or less.   A polyolefin resin foam molded article obtained by thermoforming the polyolefin resin laminated foam sheet according to claim 3.