TWI439370B - Polyolefin-based resin laminated foam sheet - Google Patents

Description

Polyolefin-based resin laminated foam sheet Technical field

The present invention relates to a polyolefin-based resin laminated foam sheet in which an antistatic layer is laminated on at least one side of a polyolefin-based resin foamed layer, and more particularly to a polyolefin-based resin laminate having a high degree of antistatic property. Foam sheet.

Background technique

Conventionally, polyolefin-based resin foamed sheets have been widely used in various containers, shipping boxes, storage boxes, and the like. However, the polyolefin-based resin foam sheet is likely to be electrostatically charged and easily adhere to dust or dust. Therefore, when the polyolefin-based resin foam sheet is used in the field where static electricity is required, various antistatic agents are added, and antistatic properties are added and used.

The antistatic agent includes a low molecular type and a high molecular type, and the low molecular type includes a fatty acid monoglyceride or a sodium alkylbenzene sulfonate. However, these are manifested by an antistatic effect due to surface overflow of the sheet material, but There is a problem in the durability of the antistatic property, and there is a problem that the packaged object is contaminated.

In order to solve the above-mentioned problem of using a low-molecular-weight antistatic agent, for example, Patent Document 1 discloses a polyolefin-based resin laminated foam sheet, and the polyolefin-based resin laminated foam sheet has an outermost layer. A thermoplastic resin layer of a polymer type antistatic agent is added.

The polyolefin-based resin laminated foam sheet disclosed in the above-mentioned Patent Document 1 has sufficient antistatic properties required in a transport case or a general electronic component transfer tray. However, in the use of electronic parts packaging materials, etc. A higher level of antistatic performance is also required, leaving room for improvement in the stable appearance of high levels of antistatic properties.

On the other hand, in the foamed sheet for thermoforming, Patent Document 2 discloses an antistatic polypropylene-based resin laminated foamed sheet in which a polyolefin-based resin layer having an antistatic layer is laminated. When the foamed sheet is thermoformed, the antistatic property is lowered. In order to reduce the decrease in the antistatic property during thermoforming, the melting point of the polymer type antistatic agent is the melting point of the polypropylene resin containing the antistatic agent ± 20 The range of °C is laminated on the polypropylene resin foamed layer containing the antistatic agent. However, in the foamed sheet disclosed in Patent Document 2, the high level of antistatic performance desired in the above applications cannot be achieved.

Further, as a polymer type antistatic agent and an antistatic property, Patent Document 3 discloses an antistatic resin composition, and the antistatic resin composition is made of a polypropylene resin 20 to 60 by weight. %; and a polymer type antistatic agent comprising 40 to 80% by weight, and the polypropylene resin is a high molecular weight crystalline polypropylene polymer having an ultimate viscosity of 5 dl/g or more; and an ultimate viscosity of 3 dl/g. The low molecular weight polypropylene polymer is composed of the following, and the total viscosity of the whole is 3 to 10 dl/g. Further, a multilayer sheet made of a thermoplastic resin is disclosed, and the multilayer sheet of the thermoplastic resin is attached to the thermoplastic resin layer. Further, an antistatic layer composed of the antistatic resin composition is laminated.

In the ring-shaped mold, the melt of the antistatic resin composition containing a large amount of the polymer type antistatic agent disclosed in Patent Document 3 is co-extruded with the foamable resin melt, and the antistatic agent is contained. Resin layer forming surface When the production of the laminated foam sheet is attempted, voids or cracks are generated in the resin layer, and it is difficult to obtain a laminated foam sheet having a resin layer having a uniform thickness.

Advanced technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-136651

Patent Document 2: Japanese Patent Laid-Open No. 2006-35832

Patent Document 3: Japanese Patent Laid-Open Publication No. 2008-270431

Summary of invention

In view of the foregoing, it is a first object of the present invention to provide a polyolefin-based resin laminated foam sheet which exhibits a high degree of antistatic property, that is, electrostatic dissipability, which is almost uncharged or completely uncharged.

Further, the present invention provides a polyolefin-based resin laminated foam sheet which exhibits electrostatic discharge for thermoforming, and a third aspect of the invention provides a polyolefin-based resin laminated foam sheet which is thermoformed. A polyolefin-based resin foam molded article exhibiting static electricity dissipation.

The present invention is based on the following contents.

(1) A polyolefin-based resin laminated foam sheet in which an antistatic layer is laminated on at least one side of a polyolefin-based resin foamed layer by a co-extrusion method using a ring-shaped mold to form a layer of a surface layer The foam sheet, the polyolefin resin laminated foam sheet, characterized in that the antistatic layer is made of a thermoplastic resin: 25% by weight or more and less than 70% by weight, and a polymer type antistatic agent: more than 30% by weight and 75 wt% or less (however, the total of the two is 100% by weight), and the antistatic layer has a melt viscosity of 250 Pa at 190 ° C and a shear rate of 100 s ^-1 . In the above, the amount of the antistatic layer to be laminated is 5 g/m ² or more of the average single-faced rice layer of the foamed layer, and the initial band voltage at the time of application of 10 kV for 30 seconds on the antistatic layer is 50 V or less.

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

(3) The polyolefin-based resin laminated foam sheet according to the above (2), wherein the ratio of the average bubble diameter in the width direction of the laminated foam sheet to the average bubble diameter in the thickness direction, and the average bubble diameter in the extrusion direction The ratio of the average bubble diameters with respect to the thickness direction is 1.0 to 2.0.

(4) The polyolefin-based resin laminated foam sheet according to the above (1), wherein the polyolefin-based resin foamed layer is a polypropylene-based resin having an apparent density of from 0.06 g/cm ³ to 0.6 g/cm ³ . Bubble layer.

(5) The polyolefin-based resin laminated foam sheet according to the above (4), wherein the laminated foam sheet has a heat shrinkage ratio in the extrusion direction and the width direction at 190 ° C of 2% or less.

Further, (6) a polyolefin-based resin foam molded article obtained by thermoforming a polyolefin-based resin laminated foam sheet according to the above (3).

The present invention relates to a polyolefin-based resin laminated foam sheet which is obtained by a co-extrusion method using a ring mold, and which has been added with a polymer type antistatic agent. Thermoplastic resin

The antistatic layer is formed as the outermost layer, and in addition, the antistatic layer exhibits excellent static electricity dissipation with little or no charge. Further, in the present invention, in particular, the polyolefin-based resin laminated foam sheet for thermoforming does not cause a line pattern or crack on the surface of the laminated foam sheet, and the surface is beautiful and exhibits excellent static electricity dissipation and heat. Formability is also excellent.

Form for implementing the invention

The polyolefin-based resin laminated foamed sheet of the present invention (hereinafter sometimes referred to as a laminated foamed sheet) is at least one of a polyolefin-based resin foamed layer (hereinafter sometimes referred to as a foamed layer). On the surface, a laminated foam sheet containing a thermoplastic resin layer (hereinafter sometimes referred to as an antistatic layer) of a polymer type antistatic agent (hereinafter sometimes referred to as an antistatic agent) is laminated.

The laminated foamed sheet of the present invention relates to a polyolefin-based resin laminated foamed sheet which is obtained by a co-extrusion method using a ring-shaped mold in a polyolefin-based resin foamed layer. The laminated antistatic layer is laminated on at least one side thereof to form a laminated foam sheet of the surface layer; wherein the antistatic layer is composed of a thermoplastic resin: 25% by weight or more and less than 70% by weight, and a polymer type antistatic agent: More than 30% by weight and 75% by weight or less (however, the total of the two is 100% by weight), and the antistatic layer has a melt viscosity of 250 Pa at 190 ° C and a shear rate of 100 s ^-1 . In the above, the amount of the antistatic layer is 5 g/m ² or more, and the initial band voltage at the time of application of 10 kV for 30 seconds on the antistatic layer is 50 V or less.

The laminated foamed sheet of the present invention has excellent antistatic properties as follows: the initial band voltage seen when applied by an electrostatic discharge tester (STATIC HONESTMETER) on an antistatic layer for 30 seconds at 10 kV. It shows those below 50V. The initial band voltage of 50 V or less is an antistatic property in the category of electrostatic dissipating which shows almost no charging. Compared with the conventionally known as an antistatic product, it has only the ability to prevent adhesion of dust or dust, and it is shown that such an antistatic property in the category called electrostatic dissipative is a high-definition antistatic function. In other words, it also means that it can prevent the packaged object such as precision electronic parts from being damaged by static electricity. In the present invention, the initial band voltage is preferably 40 V or less, and more preferably 30 V or less. The lower the initial band voltage, the better, especially 0V. Further, the laminated foamed sheet of the present invention preferably has a surface resistivity of 1.0 × 10 ¹⁰ Ω or less and an electric field of 1.0 × 10 ⁷ Ω to 5.0 × 10 ⁹ Ω.

The thickness of the laminated foamed sheet of the present invention is preferably from 0.2 to 10 mm, and more preferably from 0.5 to 8 mm. When the thickness of the whole is less than 0.2 mm, the rigidity of the foamed sheet may be insufficient depending on the use. On the other hand, when the thickness of the whole is more than 10 mm, depending on the application, the bending workability of the hinge of the foamed sheet or the like may be reduced, and the formability of forming into a box or a container may be lowered. Further, the thickness of the laminated foam sheet was measured by a microscope at a time interval of 10 times at a thickness of a cross section perpendicular to the direction in which the foam sheet was perpendicular to the extrusion direction, and then the laminated foam sheet was measured from the photograph taken. The thickness is calculated, and the arithmetic mean of each measured value is made into the thickness of the laminated foam.

In the present invention, a method of laminating an antistatic layer having an antistatic property on a polyolefin resin foamed layer is a method of forming a foamable molten resin forming a foamed layer and containing an antistatic layer. The resin melt of the antistatic agent is co-extruded, and an antistatic layer is formed on the surface of the foamed layer. As the concentration of the polymer type antistatic agent in the antistatic layer is increased, in the lamination method using thermal lamination, the adhesion between the antistatic layer and the foam layer is lowered, and sufficient adhesion cannot be obtained. However, by laminating by the co-extrusion method, even if the polymer type antistatic agent in the antistatic layer has a high concentration, a sufficient adhesion can be obtained between the antistatic layer and the foam layer or other resin layer.

The laminated foamed sheet of the present invention is formed by a polyolefin-based resin foam layer forming extruder and an antistatic layer forming extruder, and a foamed layer is formed from each of the extruders to form a melt and an antistatic layer. a molten material, and in the merging mold, the molten material is laminated to form an antistatic layer to form a molten material, and a surface layer is formed on at least one side of the foamed layer, and is adjusted to a foaming temperature at which the foamed layer forms a melt. And forming a cylindrical foam by being extruded through an annular die at atmospheric pressure, and expanding the diameter of the cylindrical foam along a cylindrical cooling pipe (cooling mandrel) and The tubular foam or the like is cut into a sheet shape and pulled.

The present invention shows that the above-mentioned electrostatically dissipative laminated foam sheet is not simply obtained by blending a polymer type antistatic agent in an antistatic layer at a high concentration, and the antistatic agent is in the resin layer forming the antistatic layer. The antistatic agent is uniformly dispersed, and the antistatic agent is disposed in an antistatic layer in a state in which a continuous layer is formed by being dispersed in a strip shape, a stripe shape, or a mesh shape (hereinafter referred to as a mesh structure), thereby exhibiting electrostatic dissipating. effect. The mesh structure can be easily formed by applying a moderate orientation when forming the antistatic layer. When the moderate orientation is to be applied and the network structure is formed, it can be obtained by the two-dimensional extension in the width direction and the extrusion direction by using the co-extrusion method of the annular mode. Accordingly, the present invention employs a co-extrusion method using a ring mold.

In the laminated foam sheet of the present invention, a polyolefin resin such as a polypropylene resin or a polyethylene resin is used as the base resin constituting the foam layer. The polyolefin resin is rich in flexibility, has excellent physical strength such as tensile strength, and has chemical resistance, and has an adhesiveness to be extruded, and is suitable as a base resin constituting the laminated foam sheet of the present invention. . In the present invention, in the polyolefin resin, a polypropylene resin excellent in rigidity or heat resistance is preferably used.

The polypropylene-based resin may, for example, be a propylene single polymer or a copolymer of propylene and a copolymerizable component copolymerizable with propylene. For example, the copolymerizable component copolymerizable with propylene can be exemplified by ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-di Ethylene or methyl 4-butene, 3-methyl-1-hexene or the like, or an alkylene group having 4 to 10 carbon atoms. Further, 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 terpolymer. Further, these polypropylene resins may be used alone or in combination of two or more. Among these polypropylene resins, a propylene individual polymer or an ethylene-propylene block copolymer excellent in rigidity is preferably used. When the copolymer is used as the base resin, the copolymer component is preferably contained in the copolymer in an amount of 25% by weight or less, particularly preferably 15% by weight or less. Moreover, the ideal lower limit of the copolymerization component contained in the copolymer is 0.3% by weight.

In the polypropylene-based resin, the base resin suitable for extrusion foaming is preferably a polypropylene-based resin having a high melt tension compared to a general polypropylene-based resin, and particularly the base resin contains the melt tension. High gathering The polypropylene resin of 15 to 50% by weight of the propylene resin is preferable because it has the manufacturing cost, the cycle property, and the suitability of the foaming of the laminated foam sheet of the present invention.

For example, the above-mentioned polypropylene-based resin having a high melt tension can be exemplified by, for example, Japanese Patent No. 2521388 or Japanese Patent No. 3,406,372 (1) having a branching index of less than 1 and significant strain hardening stretching. Viscosity of polypropylene; (2) (a) Z average molecular weight (Mz) is 1.0 × 10 ⁶ or more, or ratio of Z average molecular weight (Mz) to weight average molecular weight (Mw) (Mz / Mw) is 3.0 or more, ( b) and the balance compliance Jo is 1.2 × 10 ^-3 m ² /N or more, or the average unit stress recoverable shear strain Sr / S is 5 m ² /N or more per second; (3) polypropylene resin melting And a blend of a radically polymerizable monomer such as styrene and a radical polymerization initiator or an additive is melted and kneaded at a reaction temperature of the radical polymerization initiator, thereby modifying the polypropylene system. Or a modified polypropylene resin obtained by melt-kneading a polypropylene resin, an isobutylene monomer, and a radical polymerization initiator.

The polyethylene-based resin may, for example, be a single polymer of ethylene or a copolymer composed of ethylene and a copolymerizable α-olefin having 3 to 12 carbon atoms, and may be contained in the base resin in an amount of 60% by weight or more. Specifically, it is high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, ethylene-vinyl acetate copolymer, etc., and can be used. One type or two or more types may be mixed.

In the present invention, the polyolefin-based resin constituting the base resin of the foam layer may be a mixture of a polypropylene-based resin and a polyethylene-based resin, and a polymer blended with the polyolefin-based resin as needed. Example Further, other polymers may, for example, be ionic polymers; rubbers such as ethylene-propylene rubber and styrene-butadiene rubber; styrene-butene-styrene block copolymers, styrene-isoprene- Styrene block copolymer, styrene-butylene-styrene block copolymer hydride, styrene-isoprene-styrene block copolymer hydride, ethylene-octene block copolymerization, ethylene- A thermoplastic elastomer such as a butene block copolymerization; a butylene resin; a vinyl chloride resin such as polyvinyl chloride or a vinyl chloride-vinyl acetate copolymer; or a styrene resin. When these other polymers are mixed, the mixing amount thereof is preferably 40% by weight or less based on 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. As the inorganic physical foaming agent, carbon dioxide, air, nitrogen, water, or the like can be used. As the organic physical foaming agent, an aliphatic hydrocarbon such as propane, n-butane, i-butane, pentane or hexane; a cyclic aliphatic hydrocarbon such as cyclobutane, cyclopentane or cyclohexane; a halogenated hydrocarbon such as 1,1,1-tetrafluoroethane, 1,1-difluoroethane, methyl chloride, ethyl chloride or dichloromethane; an ether such as dimethyl ether or methyl ethyl ether. Further, as the decomposable foaming agent, azodimethylamine, dinitrosopentamethylenetetramine, azobisisobutyronitrile, sodium bicarbonate or the like can be used. These foaming agents can also be used as appropriate. Further, in the present invention, it is preferred to use a physical foaming agent for producing a foam having a low apparent density, and it is preferred to use the aforementioned hydrocarbon or carbon dioxide. In particular, carbon dioxide is more preferable because the physical properties of the foaming agent remaining in the laminated foam sheet are less changed.

The foaming agent is used in an amount according to the apparent density of the target laminated foam sheet, however, it is approximately 0.2 to 5 by weight with respect to 100 parts by weight of the base resin. Share.

In the base resin constituting the foam layer in the present invention, various additives may be added as needed. The additive may, for example, be an inorganic powder such as talc or cerium oxide or an acid salt of a polyvalent carboxylic acid, a bubble adjusting agent such as a reaction mixture of a polyvalent carboxylic acid and sodium carbonate or sodium bicarbonate, talc, cerium oxide, calcium carbonate, or the like. Inorganic fillers such as clay, zeolite, alumina, barium sulfate, etc. (talc, cerium oxide also functions as a bubble regulator), thermal stabilizers, ultraviolet absorbers, antioxidants, colorants, and the like. Further, an antistatic agent or an antibacterial agent may be blended.

The apparent density of the foamed layer of the laminated foam sheet in the present invention is preferably from the viewpoint of physical strength and lightness such as rigidity or compressive strength, and the use of the moldability in the case of thermoforming. 0.06 g/cm ³ to 0.6 g/cm ³ , and more preferably 0.08 g/cm ³ to 0.5 g/cm ³ , particularly preferably 0.09 g/cm ³ to 0.4 g/cm ³ .

The foamed layer of the laminated foam sheet of the present invention preferably has an independent cell ratio of 60% or more, and 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 foamed layer is determined from the procedure C disclosed in ASTM D2856-70 using an air comparative hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. The actual volume of the laminated foam: Vx is calculated by the following formula (1).

[Math 1]

S(%)=(Vx-W/ρ)×100/(Va-W/ρ)...(1)

However, in the above formula, Vx is the actual volume (cm ³ ) measured by the above-described measuring method, and corresponds to the volume of the resin constituting the laminated foam sheet used in the measurement and the laminated foam sheet used in the measurement. The sum of the total volumes of the bubbles in the closed bubble portion. In addition, Va, W, and ρ in the above formula are as follows.

Va: Apparent volume (cm ³ ) of the laminated foam sheet calculated from the size of the laminated foam sheet used for the measurement W: Total weight (g) of the laminated foam sheet used in the measurement: constituting laminated foam The density of the resin of the sheet (g/cm ³ )

Further, a plurality of sheets were cut from the laminated foam sheets, and the length and the width were respectively 2.5 cm and the height was 4 cm, and a plurality of sheets were combined to make the apparent volume closest to 25 cm ³ to be used as a test piece. Further, the density ρ of the resin constituting the laminated foam sheet can be defoamed from the laminated foam sheet by hot pressing, and the density can be obtained from the obtained sample.

The polymer type antistatic agent used in the present invention has an average molecular weight of at least 300 or more, more preferably 300 to 300,000, more preferably 600 to 150,000, and a resin having a surface resistivity of less than 1 × 10 ¹⁰ Ω. More preferably, it is a resin of less than 1 × 10 ⁸ Ω. Further, the polymeric antistatic agent may also contain an inorganic salt or a low molecular weight organic protonic acid salt 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. Further, the upper limit of the number average molecular weight of the polymer type antistatic agent is about 500,000.

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

Specifically, the polymer type antistatic agent may be, for example, selected from the group consisting of polyethylene oxide, polypropylene oxide, polyethylene glycol, polyether, polyester decylamine, polyether ester decylamine, and ethylene-methacrylic acid. One of a quaternary ammonium salt such as a copolymer or the like, or a quaternary ammonium salt such as a polyethylene glycol methacrylate polymer; or a mixture of two or more kinds; or a copolymer of two or more kinds; a copolymer of another resin such as polypropylene, or the like, having a polar group in a molecular chain, and an inorganic salt or a low molecular weight organic protonic acid salt can be formed into a complex or a solvated resin, or an inorganic salt or an inorganic salt or The organic protonate or the like forms a complex or a solvent. Further, the upper limit of the melting point of the polymer type 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 the melting point of the antistatic agent within the above range, the basic physical properties of the base resin to which the antistatic agent is added can be maintained, and the above-mentioned network structure can be formed relatively easily.

In addition, the crystallization temperature of the polymer type antistatic agent is preferably Tc + 40 ° C or less based on the crystallization temperature (Tc) of the base resin constituting the polyolefin resin foam sheet. Further, the lower limit of the crystallization temperature of the antistatic agent is approximately 60 °C. When the crystallization temperature of the antistatic agent is selected to be within the above range, an antistatic effect can be obtained, and in particular, when the laminated foam sheet of the present invention is obtained by a co-extrusion method, a special appearance can be obtained. Excellent.

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

The melting point system has been adjusted by JIS K7121-1987, 3. The state of the test piece The condition of the section (2) (however, the cooling rate was 10 ° C / min.) The test piece in which the test piece was adjusted in state was heated at 10 ° C / min to obtain a melting peak. The peak temperature of the obtained melting peak is set as the melting point. Further, when two or more melting peaks occur, the peak temperature of the melting peak on the highest temperature side is set to the melting point.

The crystallization temperature is based on JIS K7121-1987, 3. Condition adjustment (2) of the test piece, and the temperature is raised at a temperature increase rate of 10 ° C / minute, and then the temperature is lowered at a cooling rate of 10 ° C / minute, and the obtained temperature is obtained. The apex temperature of the peak of the heat generation is the crystallization temperature. Further, when two or more peaks of heat generation occur, the apex temperature of the peak of the heat generation on the highest temperature side is set as the crystallization temperature.

Among the polymer type antistatic agents used in the present invention, a polyether ester decylamine or a polyether is particularly preferred as a main component. These antistatic agents do not significantly increase the ratio of the melt flow rate of the base resin of the antistatic layer to the melt flow rate of the antistatic agent, and exhibit an excellent antistatic effect. Furthermore, in order to improve the compatibility with the base resin of the antistatic layer, and to suppress the deterioration of the physical properties due to the excellent antistatic effect and the addition of the antistatic agent, the antistatic agents are preferably used in an antistatic agent or The polymer is copolymerized with a polymer excellent in compatibility with a thermoplastic resin constituting the antistatic layer.

Further, the above-mentioned main component means that the polyether ester decylamine and the polyether component are contained in an amount of 50% by weight or more, preferably 75% by weight or more, and more preferably 85% by weight or more. By using such an antistatic agent, a network structure or the like can be formed by a method described later, whereby an antistatic layer exhibiting electrostatic discharge properties can be formed.

The polyether ester amide is a polyamine (1) and a bisphenol exemplified by the following examples. The polymerization reaction of the alkylene oxide adduct (2). The polyamine (1) is a polycondensate of (a) a decylamine ring-opening polymer, (b) an amino carboxylic acid polycondensate or (c) a dicarboxylic acid and a diamine. The guanamine in (a) may, for example, be caprolactam, heptanoin, laurylamine or eleven indoleamine. The aminocarboxylic acid of the above (b) may, for example, be ω-aminohexanoic acid, ω-aminoheptanoic acid, ω-aminooctanoic acid, ω-amino decanoic acid, ω-amino decanoic acid, 11-amine Undecanoic acid, 12-aminododecanoic acid, and the like. Examples of the dicarboxylic acid of the above (c) include adipic acid, sebacic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, isodecanoic acid and the like. Further, the diamine may be, for example, six. Methylenediamine, heptaethylenediamine, octanediamine, decanediamine, and the like.

Two or more kinds of the above-described guanamine forming monomers can be used. Among these, preferred are caprolactam, 12-aminododecanoic acid, adipic acid, and hexamethylenediamine, and particularly preferred is caprolactam.

The bisphenols of the bisphenol-based alkylene oxide adduct (2) may, for example, be bisphenol A (=4,4'-dihydroxydiphenyl-2,2-propane) or bisphenol F (= 4,4'-dihydroxydiphenylmethane), bisphenol S (=4,4'-dihydroxydiphenyl hydrazine), 4,4'-dihydroxydiphenyl-2,2-butane, etc. Among them, bisphenol A is particularly desirable.

Further, examples of the alkylene oxide of the bisphenol-based alkylene oxide adduct (2) include ethylene oxide, propylene oxide, 1,2- or 1,4-butylene oxide, and two or more of them. mixture. Among these, ethylene oxide is preferred.

The foregoing polyether can be exemplified by: (a) by alkylating oxygen to phenols. An alkylene oxide obtained by addition reaction in a divinylbenzene addition polymer; (b) an alkylene oxide belonging to polyoxyethylene glycol, polyoxypropylene diol, polyoxybutylene diol, bisphenol a di-epoxypropyl ether of an adduct or the like, and having a hexyl group, an n-octyl group, a 2-ethylhexyl group, a fluorenyl group, a fluorenyl group, a dodecyl group, a tetradecyl group, an octadecyl group, an oleyl group The carbon number of the base or the like is preferably from 1 to 22, more preferably an aliphatic hydrocarbon compound having 6 to 22 carbon atoms, and an alkyl sulfate such as dimethyl sulfate or diethyl sulfate; dimethyl carbonate; Tertiary alkyl carbonates such as diethyl carbonate; various phosphates or halides such as trimethyl phosphate, alkylbenzyl chloride, benzyl chloride, alkyl chloride, alkyl bromide, etc. A cationic antistatic agent composed of a compound having two or more quaternary ammonium salt groups in a molecule.

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

Examples of the bisphenols include bisphenol A (=4,4'-dihydroxydiphenyl-2,2-propane), bisphenol F (=4,4'-dihydroxydiphenylmethane), bisphenol An alkylene oxide adduct of S (=4,4'-dihydroxydiphenylhydrazine), 4,4'-dihydroxydiphenyl-2,2-butane or the like.

Among the above diglycidyl ethers, particularly preferred are epoxidized propyl ethers of polyoxyethylene diols, diglycidyl ethers of ethylene oxide adducts of bisphenols, and mixtures thereof.

Among the foregoing amine compounds, N-alkyl (carbon number 1 to 18) diethanolamine is particularly desirable. Further, among the above-mentioned quaternizing agents, dimethyl sulfate and diethyl sulfate are particularly preferable.

In the polyether ester guanamine or polyether, in order to suppress the physical property degradation caused by the excellent antistatic effect and the addition of the antistatic agent, it is more desirable to mix or copolymerize the polyamine or form an antistatic agent. Layer of thermoplasticity tree A polymer having the same type or compatibility as a fat, particularly a polymer having a number average molecular weight of 800 to 25,000. The polyamine used herein may, for example, be a polyamine and a copolymerized decylamine derived from a diamine and a dicarboxylic acid and/or an aminocarboxylic acid or an equivalent internal amine.

Specifically, it can be exemplified by polyamine 4, polyamine 6, polyamine 6/6, 6/10, 6/9, 6/12, 4/6, 12/12, polyamine 11, and poly An amidamide 12, an aromatic polyamine of m-extended diamine and adipic acid, a polyamine obtained by adding an elastomer from hexamethylenediamine and isononanoic acid and/or citric acid; a copolymer of the above polyamine with the aforementioned polymer, ionic polymer or elastomer, or a block copolymer of polyamine with polyethylene glycol, polypropylene glycol or polybutanediol; and by ethylene-propylene Rubber (EPDM) or ABS denatured polyamide or copolyamide. The content of the polyamine or the like is 50% by weight or less, and preferably 25% by weight or less.

In the present invention, the antistatic layer is composed of a thermoplastic resin constituting the antistatic layer: 25% by weight or more and less than 70% by weight, and an antistatic agent: more than 30% by weight and not more than 75% by weight (the total of the two is 100% by weight). When the amount of the antistatic agent added is 30% by weight or less, the target electrostatic dissipative property cannot be obtained. When the addition amount is a high concentration of more than 75% by weight, the formation of the antistatic layer itself becomes difficult, and the network structure of the antistatic agent cannot be formed, so that the effect of the above electrostatic dissipability cannot be obtained. From the foregoing point of view, the antistatic agent is preferably in the range of 33% by weight to 70% by weight, particularly preferably in the range of 35% by weight to 65% by weight.

Examples of the thermoplastic resin include a polyolefin resin constituting the base resin of the foam layer, a styrene resin, or a mixture thereof. Among these, a polyolefin-based resin and a polypropylene-based resin are preferably used.

In the present invention, in order to obtain electrostatic detachment, it is preferred to use a high concentration of the antistatic agent in the antistatic layer containing the polymer type antistatic agent. On the other hand, the polymer type antistatic agent has a problem that the melt viscosity is low, and when the antistatic layer containing the polymer type antistatic agent is formed by co-extrusion, when the amount of the polymer type antistatic agent is large, The viscosity of the resin melt forming the antistatic layer is lowered, and the pressure in the mold is difficult to maintain during the co-extrusion, and it is difficult to exhibit good static electricity dissipation. Further, in some cases, a line crack which is a non-uniform striped pattern is generated in the direction in which the obtained sheet is extruded. When a laminated foam sheet for thermoforming is used, the line crack may involve a decrease in static electricity dissipation.

Therefore, in the present invention, the blending amount of the thermoplastic resin and the polymer type antistatic agent is adjusted. In this case, it is important to set the melt physical properties of the mixture of the thermoplastic resin and the polymer type antistatic agent to a specific range. That is, the antistatic layer has a melt viscosity of 250 Pa at 190 ° C and a shear rate of 100 s ^-1 . Above s, and should be 350Pa. s above. If the melt viscosity is 250Pa. When s or more, and a specific amount of rice is laminated on the foamed layer, the antistatic property of the target initial voltage of 50 V or less can be obtained. When the melt viscosity is less than 250Pa. In the case of s, the melt viscosity of the molten resin for forming an antistatic layer in the mold is too low, and the target electrostatic dissipative property may not be obtained. The upper limit of the melt viscosity is approximately 1200 Pa. s or so. When the melt viscosity is high, since it is difficult to obtain a laminated foam sheet by co-extrusion, the aforementioned melt viscosity is preferably 400 to 1000 Pa. s, and more preferably 450 to 800 Pa. s.

The melt viscosity of the antistatic layer and the thermoplastic resin and the polymer type antistatic agent for forming the antistatic layer can be measured using, for example, a measuring device such as CAPIROGRAPH 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a cylinder having a cylindrical diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 1.0 mm and a length of 10 mm were used, and the set temperature of the cylinder and the orifice was set to 190 ° C, and about 15 g of the measurement sample was placed. After standing in the cylinder for 5 minutes, the molten resin was extruded from the orifice at a shear rate of 100 sec ^-1 , and the melt viscosity at that time was measured.

Further, when the melt viscosity of the antistatic layer is measured, the antistatic layer can be completely cut from the laminated foam sheet to be used as a measurement sample, or the antistatic layer can be formed only by the same conditions as in the production of the laminated foam sheet. The sample was used for measurement.

Further, the melt-stretching of the antistatic layer at 175 ° C is 60 m / min or more, and more preferably 65 m / min or more, particularly preferably 70 m / min or more. The upper limit is approximately 180 m/min. When the melt-stretching value of the antistatic layer is within the above range, when the laminated foam sheet is produced by the co-extrusion method, the antistatic layer can be favorably elongated, and therefore, the antistatic layer of the laminated foam sheet is not prevented. The layers produce countless holes and show a good appearance. Further, when the laminated foam sheet which has produced numerous holes in the antistatic layer is thermoformed into a shape of a container or the like, the molded body obtained has insufficient static electricity dissipation.

The melt drawing can be measured using, for example, a measuring apparatus such as CAPIROGRAPH 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a cylinder having a cylindrical diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 2.095 mm and a length of 8.0 mm were used, and the set temperature of the cylinder and the orifice was set to 175 ° C, and about 15 g of the measurement sample was placed. Into the cylinder and place it for 5 minutes After that, the piston descending speed was set to 10 mm/min, and the molten resin was taken out from the orifice, and the belt was hung on a pulley having a diameter of 45 mm, and the pulling speed was increased at a certain rate. The drawing speed was brought to a distance of 200 m/min from 0 m/min in 4 minutes, and the belt was pulled by pulling the roller, and the pulling speed at the front of the belt was melt-stretched when the belt was broken. The measurement was carried out for a 10-point measurement sample sampled from any of 10 samples, and the arithmetic mean of these was used for the melt stretching in the invention.

Further, the measurement of the melt-stretched sample is the same as the measurement of the melt viscosity, and the anti-static layer can be completely cut from the laminated foam sheet to be used as a measurement sample, or the same conditions as in the production of the laminated foam sheet, only The antistatic layer was extruded and used as a measurement sample.

Further, in order to avoid the occurrence of the aforementioned line crack of the laminated foam sheet, it is preferable to select a thermoplastic resin having a melt flow rate (MFR) lower than that of a thermoplastic resin which is conventionally used in a resin layer which is co-extruded into a foamed molding. For example, when a resin other than the polymer type antistatic agent constituting the antistatic layer is selected as the polypropylene resin, MFR is preferably used in the range of 0.3 to 14 g/10 minutes, and is 0.6 to 12 g/10 minutes, particularly 1.0 to 8 g/10 minutes of polypropylene resin.

In the antistatic layer of the laminated foam sheet of the present invention, in order to exhibit electrostatic discharge property, it is necessary to have a high concentration of the antistatic agent in the antistatic layer of a specific metering amount described later, and further, since the antistatic layer is necessary Since the specific melt viscosity is mentioned above, the thermoplastic resin which comprises an antistatic layer uses the high viscosity thermoplastic resin. Moreover, when the laminated foam sheet is thermoformed into a shape of a container or the like, the antistatic layer must have a specific melt stretch in order to exhibit electrostatic discharge property in the obtained molded body. So easy The polymer-type antistatic agent that causes lower viscosity is poorly mixed with the high-viscosity thermoplastic resin, and it is difficult to obtain stable melt stretching. Therefore, in order to obtain stable melt stretching, it is necessary to fully mix the antistatic agent and thermoplasticity. Resin. By performing the following treatment, it is possible to obtain stable melt stretching, that is, premixing using a twin-axis extruder. From the above viewpoints, the melt stretch value of all 10 points obtained in the melt tensile measurement is preferably within ±20% of the arithmetic mean value, and more preferably within ±15%, particularly preferably Within ±10%. If the error is more than ±20%, even if the average value satisfies the above range, there is a possibility that perforation or the like occurs. Therefore, in order to obtain the above-mentioned molten antistatic layer, it is not only the choice of materials, but also the ideal aspect of the kneading.

In the present invention, the amount of the rice layer of the antistatic layer containing the antistatic agent must be 5 g/m ² or more on the average single side of the foamed layer. When the amount of the rice flat is less than 5 g/m ² , even if a high-concentration polymer type antistatic agent is used, the static electricity dissipation property cannot be obtained. In order to achieve the electrostatic dissipation property, that is, the initial band voltage is 50 V or less, the type of the polymer type antistatic agent and the concentration in the antistatic layer, the melt viscosity of the mixture of the thermoplastic resin and the polymer type antistatic agent, and the antistatic layer. The amount of the meter is closely related, and the thicker the layer, the easier it is to exhibit electrostatic dissipation. If the amount of the layered polymer is large, even if the amount of the polymer type antistatic agent is relatively reduced within the above-mentioned range, it can be obtained. Electrostatic dissipative property, however, even if the amount of lamination is increased, the effect hardly changes. Therefore, the upper limit is about 80 g/m ^{2 on the} average single side. On the other hand, when the amount of the laminated layer is large, when the laminated foam sheet is thermoformed, the heat balance necessary for thermal deformation of the foamed layer and the resin layer may be excessively different, and thermoforming may become difficult. Therefore, in order to obtain stable static electricity dissipability and thermoformability, the average amount of the single-layered rice is preferably from 10 to 70 g/m ² , and more preferably from 20 to 60 g/m ² .

Further, the antistatic layer may be added with one or more additives such as an antibacterial agent or an elastomer to the base resin constituting the antistatic layer, and the laminated foam sheet of the present invention may be made more functional. Examples of the antibacterial agent include those having antibacterial activity such as silver, copper, and zinc supported on a carrier, such as silver zeolite, copper zeolite, zirconium phosphate supported on silver, and tantalum containing silver. An agent; an antibacterial agent using an oxide photocatalyst represented by anatase type titanium oxide; benzalkonium chloride, polyoxyethylene trialkylammonium chloride, polyhexamethylene biguanide hydrochloride, chlorinated 3- An organic drug or the like such as (trimethoxyindenyl)propyldimethyloctadecyl ammonium. Further, as the elastomer added to the antistatic layer, the same thermoplastic elastomer as used in the foamed layer can be used. The addition of the elastomer adds cushioning 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. At this time, the layer structure is formed such that the antistatic layer is located at the outermost layer of the laminated sheet. The base resin forming the resin layer not containing the antistatic agent is the same as the base resin constituting the foam layer or the antistatic layer, and the base resin may be selected to have high density in order to impart impact resistance. Ethylene or a substrate resin containing a thermoplastic elastomer. In terms of good adhesion to the foam layer or the antistatic layer, the resin constituting the resin layer, the antistatic layer and the foam layer is preferably used to exhibit sufficient thermal adhesion, and the resin is produced in order to obtain an inexpensive laminated foam sheet. The layer may be blended with a base resin phase of the foamed layer The same kind of recycled raw materials.

When a plurality of resin layers composed of an antistatic layer and at least one resin layer (intermediate layer) are formed on at least one side of the foam layer, the total amount of the rice layer of the plurality of resin layers is preferably in the form of a foam layer. The average single-faced rice floor is 20 to 250 g/m ² laminate. If the total amount of the total amount of rice is too large, the closed cell ratio of the foamed layer is liable to lower, and the rigidity of the sheet is lowered. Therefore, the amount of the laminate when forming the plurality of resin layers is preferably in the range of 20 to 250 g/m ² , and more preferably 30 to 210 g/m ² , particularly preferably 40 to 180 g/. m ² .

The resin layer (intermediate layer) located between the foam layer and the antistatic layer may be foamed or non-foamed. When foaming, the apparent density is preferably 0.3 g/cm ³ or more, that is, preferably Low foaming. Further, an inorganic filler may be contained in a large amount. The laminated foamed sheet of the present invention has a layer structure as follows, that is, on one side of the foamed layer, it is preferred to laminate an antistatic layer containing an antistatic agent on both sides; one side of the foamed layer; Or a double-layer layer of a plurality of resin layers composed of two or more layers of an antistatic layer and another resin layer not containing an antistatic agent. The laminated foam sheet having a resin layer (intermediate layer) between the foam layer and the antistatic layer can improve the mechanical strength such as rigidity.

The laminated foam sheet of the present invention is suitably used as a sheet for thermoforming. Further, in addition to heating the laminated foam sheet and forming it into a shape of a container or the like using a mold, the thermoforming system of the present invention includes a person who heats and flattens the laminated foam sheet.

When the laminated foam sheet of the present invention is used as a sheet for thermoforming, the average bubble diameter in the width direction of the laminated foam sheet is averaged with respect to the thickness direction. The ratio of the bubble diameter (the average bubble diameter in the width direction/the average bubble diameter in the thickness direction), and the ratio of the average bubble diameter in the extrusion direction to the average bubble in the thickness direction (the average bubble diameter in the extrusion direction/the average bubble diameter in the thickness direction) It is preferably from 1.0 to 2.0, and more preferably from 1.1 to 1.8, particularly preferably from 1.2 to 1.6. When the ratio of the average cell diameter is from 1.0 to 2.0, the strain of the sheet material is small, and deformation of the molded article after thermoforming and the like can be suppressed.

In the present specification, the ratio of the average cell diameter is determined by the following preparation. First, a vertical section in the width direction of the foamed sheet is taken by a microscope or the like. According to the obtained image, the bubble diameters in the width direction and the thickness direction are measured for the entire bubble of the foam layer existing on the image, and the measured bubble diameters are arithmetically averaged, thereby obtaining the width direction. The average cell diameter and the average cell diameter in the thickness direction are divided by the average cell diameter in the width direction by the average cell diameter in the thickness direction, thereby obtaining the average cell diameter in the width direction and the average cell diameter in the thickness direction. ratio. Similarly, according to the image of the vertical cross section in which the direction of the extrusion of the foamed sheet is taken by a microscope or the like, the average bubble diameter in the extrusion direction and the average bubble diameter in the thickness direction are obtained, and the average bubble diameter in the extrusion direction is divided. The average bubble diameter in the thickness direction is used to determine the ratio of the average bubble diameter in the extrusion direction to the average bubble diameter in the thickness direction.

Further, 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 preferably the extrusion direction, The width direction is 0.1 to 2% or less, and more preferably 0.1 to 1.5%, particularly preferably 0.1 to 1.0%. In the laminated foam sheet having a heat shrinkage ratio larger than the above specific range, in the use of a forming mold In the case of hot forming, the mold release property from the mold is poor, and the dimensionality is also poor, and a good molded product cannot be obtained, and the production efficiency is also deteriorated. On the other hand, it is easy to produce warpage at the time of flattening, and it is difficult to produce a good flat plate.

The heat shrinkage ratio in the extrusion direction of the laminated foam sheet in the present specification is the following value (%), that is, the size of the pre-heating direction of the self-assembled foam sheet in the extrusion direction minus the heating direction of the lamination direction of the laminated foam sheet The difference is divided by the pre-heating size of the lamination direction of the laminated foam sheet, and multiplied by 100 to obtain the difference. The heating shrinkage ratio in the width direction orthogonal to the extrusion direction of the laminated foam sheet is the following value (%), that is, the size before heating in the width direction of the laminated foam sheet minus the heated dimension in the width direction of the laminated foam sheet The difference obtained is divided by the pre-heating size in the width direction of the laminated foam sheet, and multiplied by 100 to obtain the difference.

The laminated foam of the present invention preferably has an apparent density of from 0.06 g/cm ³ to 0.6 g/cm ³ , more desirably from 0.07 g/cm ³ to 0.45 g/cm ³ , particularly from 0.10 g/cm ³ to 0.3 g/cm ³ . When the apparent density of the laminated foamed sheet is within the above range, the physical properties and the lightweight properties such as rigidity and compressive strength are excellent, and the formed foamed sheet for thermoforming also exhibits excellent thermoformability.

A method for producing the polyolefin-based resin laminated foam sheet of the present invention will be described. First, in the laminated foam sheet of the present invention, since a polymer type antistatic agent of more than 30% by weight and not more than 75% by weight is used in the antistatic layer, it is necessary to maintain the composition for forming the antistatic layer to be homogeneous. The film forming property of the electrostatic layer and the resulting antistatic layer exhibit sufficient electrostatic dissipation. Therefore, it is important to select a polyolefin-based resin or an antistatic layer constituting the foamed layer of the laminated foam sheet of the present invention to satisfy the specific requirements described so far. Pieces. Further, in order to obtain a laminated foam sheet for thermoforming, the kneading of the composition forming the antistatic layer also constitutes an important factor. When the kneading of the composition forming the antistatic layer is not sufficiently performed, although the static electricity dissipation property is exhibited, the appearance of the surface of the laminated foamed sheet produced may be lowered, and the occurrence of perforation or line cracking may occur. The antistatic property of the antistatic layer of the molding system obtained by thermoforming such a laminate foam sheet is deteriorated, and the static electricity dissipation property cannot be exhibited.

Further, as a standard for the degree of kneading of the composition forming the antistatic layer, whether or not the kneaded material is included in the specific melt viscosity and the range of melt stretching is a standard. As a method of performing sufficient kneading, it is useful to use an L/D elder for an extruder, for example, an L/D of 30 or more, or a helix having a UNIMELT or a squeegee mixing head for improving the kneading degree. Moreover, by using a two-axis extruder and premixing, it is also possible to make up for the lack of mixing.

The laminated foamed sheet of the present invention is a first extruder that forms a foamed layer and a second extruder that forms an antistatic layer, and the polyolefin resin and the bubble are formed in the first extruder. The agent is added with other additives as needed, and is melt-kneaded under heating, and in the melt-kneaded product, the foaming agent injection port of the self-pressing machine is pressed into the foaming agent to be kneaded, and the foaming is prepared. A foaming resin melt of the agent. On the other hand, the thermoplastic resin forming the antistatic layer is melted and kneaded by an antistatic agent under heating by a second extruder, and a molten material for forming an antistatic layer is prepared. Further, when a resin layer as an intermediate layer is laminated except for the antistatic layer, the base resin is melted and kneaded under heating by a third extruder and extruded by a resin layer to form a resin layer. Use a melt. Downstream of the extruder In the merging mold, the foamed resin melt and the melt for forming an antistatic layer, the melted resin melt, the melt for forming an antistatic layer, and the melt for forming a resin layer are laminated. For example, such as an antistatic layer/foam layer/antistatic layer, or an antistatic layer/resin layer/foam layer/resin layer/antistatic layer, the melt for forming an antistatic layer constitutes the outermost layer and is adjusted The foaming temperature of the resin melt is formed for the foamed layer, and is extruded through an annular die at atmospheric pressure to form a cylindrical foam. Then, by the conventionally known method, for example, the cylindrical foam is expanded along the cylindrical cooling device (cooling mandrel) to enlarge the diameter of the cylindrical foam, and the cylindrical foam is cut. A laminated foam sheet was produced by a method of forming a sheet.

In the present invention, a laminated foam sheet having an antistatic layer containing a polymer type antistatic agent at a high concentration is produced by a co-extrusion method using a ring mold, but a polymer type is used at a high concentration. In the antistatic agent, when the laminated foam sheet is produced by the co-extrusion method using a ring die, the resistance of the cylindrical foam body and the surface of the cooling mandrel is increased, and the appearance of the obtained laminated foam sheet is lowered. Or heat shrinkage, especially the shrinkage value of the extrusion direction will become larger. When a molded article such as a container is produced by a thermoforming machine, for example, the laminated foamed sheet has a large shrinkage ratio and is intimately bonded to the mold after being formed by the mold. The mold release is easy, the molding cycle time is greatly prolonged, and the production efficiency is poor, so that a good product cannot be produced. Further, in the step (flattening) in which the laminated foam sheet which has been produced through the cylindrical cooling mandrel is heated and corrected to form a flat plate, strain is left on the foamed sheet, and a good flat plate cannot be produced. In addition, if the concentration of the polymer type antistatic agent of a general antistatic level, for example, the concentration of the antistatic agent in the antistatic layer is 30 weight When the amount is less than or equal to a small amount, such a phenomenon is small. However, when the concentration of the antistatic agent is more than 30% by weight, the above phenomenon is apparent. It is generally speculated that the reason may be that the polymer type antistatic agent contains many metals with high adhesion.

The above problem can be solved and alleviated by performing a composite plating of polytetrafluoroethylene (PTFE) or a metal and PTFE on the surface of a cylindrical cooling mandrel, thereby performing coating treatment and the like. The resistance of the tubular foam and the surface of the cooling mandrel is lowered. Moreover, the diameter of the front side of the cooling pipe (the introduction side of the cylindrical foam body) is reduced, and the diameter of the rear side of the cooling pipe (the outlet side of the cylindrical foam body) is reduced and a taper is provided. Reduce the strain of laminated foam sheets.

By using such a method, in the method of producing a laminated foam sheet by co-extrusion using a ring mold, even when a polymer type antistatic agent is used at a high concentration, a laminate having an excellent appearance can be obtained. Foam sheet. Further, it is possible to reduce the excessive strain of the laminated foam sheet which is problematic in the case of use in the case of thermoforming, and to adjust the heat shrinkability of the laminated foam sheet, even when it is used as a sheet for thermoforming. It may also be included in the range of suitable shrinkage rates described above. Thereby, the following polyolefin-based resin laminated foam sheet for thermoforming can be obtained, that is, the static electricity dissipating property is a matter of course, and the moldability is also excellent.

Example

The invention will be more specifically described by way of examples. Further, the physical properties of the examples and comparative examples were evaluated by the following methods.

[Melting Flow Rate (MFR)]

The measurement of the melt flow rate is carried out in accordance with the method of JIS K7210-1999, A, at a test temperature of 190 ° C and a load of 21.18 N. Determination. Further, in the polypropylene resin and other resins, the measurement was carried out in accordance with the method of AIS of JIS K7210-1999 at a test temperature of 230 ° C and a load of 21.18 N.

[melt viscosity]

The melt viscosity was measured in accordance with the above method and using CAPIROGRAPH 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. The measurement of the melt viscosity of the raw material was carried out by directly using the raw material pellet as a measurement sample. When the melt viscosity of the antistatic layer was measured, the antistatic layer was formed in the same manner as the production conditions of the laminated foam sheet, and a sample for measurement was prepared.

[melt stretching]

The melt drawing was carried out in accordance with the above method, and was measured using CAPIROGRAPH 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. The measurement sample was prepared by the same conditions as those of the laminated foam sheet, and only the antistatic layer was extruded.

[average bubble diameter ratio (bubble flattening ratio)]

The ratio of the average cell diameter in the width direction (TD) of the laminated foam sheet to the average cell diameter in the thickness direction (VD) was determined by the following procedure. First, the cross section of the foam sheet which is perpendicular to the extrusion direction is magnified 100 times by the microscope, and the entire bubble existing in the enlarged image (except that the bubble is broken on the way) is taken as an object. The bubble diameter in the width direction of each bubble and the bubble diameter in the thickness direction were measured, and the measured values were arithmetically averaged, and the average bubble diameter in the width direction and the average bubble diameter in the thickness direction were obtained. The measurement was performed on the cross sections at five intervals at equal intervals in the width direction of the laminated foam sheets, and the average width direction obtained for each cross section was averaged. The average cell diameters in the cell diameter and the thickness direction are arithmetically averaged, whereby 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/average cell diameter in the thickness direction) is obtained. In the same manner, in the direction of the extrusion direction of the laminated foam sheets at equal intervals in the width direction of the laminated foam sheets, the average bubble diameter and the thickness direction (VD) average bubble diameter in the extrusion direction (MD) of the laminated foam sheets were obtained and borrowed. The average bubble diameter in the extrusion direction is obtained by dividing the average bubble diameter in the thickness direction (the average bubble diameter in the extrusion direction/the average bubble diameter in the thickness direction).

[heat shrinkage rate]

The heat shrinkage ratio of the laminated foam sheet was measured by the following procedure. Three test pieces of 200 mm × 10 mm width sheet were cut out from the laminated foam sheets at equal intervals in the width direction of the sheet, and the test pieces were placed on a metal plate which had been covered with talc, and Heat in an oven at 190 ° C for 120 seconds. After the completion of the heating, the heated foamed sheet size in the extrusion direction was measured, and the heat shrinkage ratio of each test piece was determined in accordance with the following formula (2), and the arithmetic mean value of the above was made into the heat shrinkage in the extrusion direction. rate. Further, in the width direction, three test pieces of 10 mm in the extrusion direction and 200 mm in the width direction were cut out from the laminated foam sheets at equal intervals in the width direction of the sheet, and were similarly prepared to obtain heat shrinkage in the width direction. rate.

[Math 2]

Heating shrinkage ratio (%) = {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]

The initial voltage measurement of the laminated foam sheet was carried out by using a static decay tester (STATIC HONESTMETER) manufactured by Sisi Di Shuang (SSD) Electrostatic Co., Ltd., in accordance with JIS L1094-1980. Specifically, five test pieces (40 mm × 40 mm) were cut out at equal intervals in the width direction perpendicular to the extrusion direction of the foam sheet, and the test piece was attached to the mounting frame of the measuring machine, and the turntable was rotated while rotating. After 30 seconds (+) of 10 kV was applied, the application was stopped, and the average value of the residual band voltage at the time of the application stop was set as the initial band voltage.

[surface resistivity]

The surface resistivity of the laminated foam sheet was measured in accordance with 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 piece was placed under an ambient gas of 23 ° C and a humidity of 50%. After standing for 24 hours, the measurement was performed using a resistance measuring instrument (manufactured by HIOKI), and the average value of the measured values was made into a surface resistivity.

〔Exterior〕

The appearance of the laminated foam sheet was evaluated in accordance with the following criteria.

◎: The antistatic layer is uniformly laminated.

○: The antistatic layer was substantially uniformly laminated.

△: In the antistatic layer, a line pattern or perforation which constitutes a problem during thermoforming is seen.

Examples 1 to 5, 7, 9, 10, 14, 15, Comparative Examples 1, 3 to 5

Manufacture of a polypropylene resin foam layer as a laminated foam sheet by using a tandem extruder consisting of two extruders having an inner diameter of 90 mm and an inner diameter of 120 mm The extruder was used, and an extruder having an inner diameter of 40 mm was used as an extruder for manufacturing an antistatic layer, and in order to bond the polypropylene resin foam layer and the antistatic layer together, a ring die having a diameter of 100 mm was used. .

First, in order to form a polypropylene-based resin foamed layer, a bubble adjusting agent (Bai Lingjia, Japan) is blended with 100 parts by weight of a polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., grade: FB3312) (labeled as PP7). 0.5 parts by weight of PO217K, blended with sodium bicarbonate and sodium citrate, supplied to Boehringer Ingelheim Co., Ltd., and supplied to a raw material input port of an extruder having an inner diameter of 90 mm, and heated and kneaded. A molten resin mixture of about 200 ° C is prepared, and carbon dioxide is injected as a foaming agent in the molten resin mixture, and is 0.4 parts by weight with respect to 100 parts by weight of the polypropylene resin, and secondly, is supplied to the above-mentioned 90 mm. An extruder having an inner diameter of 120 mm connected to the downstream side of the machine was used, and a foaming molten resin mixture was obtained by discharging 98 kg/hr.

On the other hand, the polymer composition of the antistatic layer shown in Table 3 was used as the antistatic agent and the polypropylene resin shown in Table 1 as the antistatic agent shown in Table 2, and was supplied to the inner diameter. The extruder of 40 mm was melt-kneaded under heating, and an antistatic molten resin was obtained by discharging 14 kg/hr.

Each of the obtained foamable molten resin mixture and the antistatic molten resin is supplied to a merging die and joined together, and the laminated layer is made of an antistatic molten resin to form two outer layers, and is coextensive from the annular die, and is formed from the outer side. Two types of three-layer cylindrical laminated foams in which the antistatic layer/polypropylene resin foam layer/antistatic layer are laminated in this order. The cylindrical laminated foam which has been extruded is pulled along a cylindrical cooling pipe (diameter: 212 mm, enlargement ratio: 2.12) which has been subjected to sandblasting of the alumite-resistant surface to increase the smoothness by about twice. The target laminated foam sheet was obtained by cutting in the direction of extrusion. The apparent density of the foamed layer was 0.27 g/cm ³ and the thickness was 2.0 mm, and the thickness of the laminated foamed sheet was 2.1 mm, the amount of the rice flat was 640 g/m ² , and the apparent density was 0.31 g/cm ³ . 650mm. Table 4 shows the physical properties of the laminated foam sheet.

Example 6

A laminated foam sheet was produced in the same manner as in Example 1 except that the discharge amount of the antistatic molten resin was 3.5 kg/hr, and the amount of the antistatic layer was 10 g/m ² . The thickness of the entire laminated foam sheet was 2.0 mm, the amount of the meter 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 foam sheet was produced in the same manner as in Example 1 except that the amount of the antistatic molten resin discharged was 52.5 kg/hr, and the amount of the antistatic layer was 150 g/m ² . The thickness of the entire laminated foam sheet was 2.3 mm, the amount of the meter 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 produced in the same manner as in Example 1 except that the discharge amount of the antistatic molten resin was changed to 0.7 kg/hr so that the amount of the antistatic layer was 2 g/m ² . The thickness of the entire laminated foam sheet was 2.0 mm, the amount of the meter 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 was produced in the same manner as in Example 1 except that a ring-shaped mold having a diameter of 86 mm was used and a cylindrical cooling device (having a diameter of 212 mm and an amplification ratio of 2.47) having a surface-treated alumite-resistant surface was used. The thickness of the laminated foam sheet was 2.1 mm, the amount of the meter was 640 g/m ² , and the apparent density was 0.31 g/cm ³ . The smoothness of the cylindrical cooling tube is inferior to that of the surface treatment, and it is extended in the extrusion direction, and the sheet width is 624 mm. Table 4 shows the physical properties of the laminated foam sheet.

Examples 11, 12

A tandem extruder consisting of two extruders having an inner diameter of 90 mm and an inner diameter of 120 mm was used as an extruder for producing a polypropylene resin foamed layer of a laminated foam sheet, and an extruder having an inner diameter of 40 mm was used. In the extrusion machine 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 having an inner diameter of 50 mm is used, and a polypropylene resin foam layer and an intermediate layer are used. The antistatic layer was laminated and coextruded, and a ring die having a diameter of 100 mm was used.

First, in order to form a polypropylene-based resin foamed layer, a bubble adjusting agent (Bai Lingjia, Japan) is blended with 100 parts by weight of a polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., grade: FB3312) (labeled as PP7). Manufactured by Ingelheim Co., Ltd., PO217K, blended with sodium bicarbonate, sodium citrate, 0.75 parts by weight, and supplied to a raw material input port of an extruder having an inner diameter of 90 mm, and heated and kneaded, and the finished product has been prepared to be about 200. a molten resin mixture of °C, in which carbon dioxide is injected as a foaming agent, and is made up to 0.4 parts by weight with respect to 100 parts by weight of the polypropylene resin, and secondarily supplied to the downstream side of the above-mentioned 90 mm extruder Inside the link An extruder having a diameter of 120 mm and a discharge amount of 98 kg/hr were used to prepare a foamable molten resin mixture.

On the other hand, a polypropylene resin (manufactured by Nippon Polypropylene Co., Ltd., grade: BC3RA) (labeled as PP4) was supplied to an extruder having an inner diameter of 50 mm, and melt-kneaded, and the amount of discharge was 28 kg/hr. A molten resin for the intermediate layer was obtained.

In addition, the polymer composition of the antistatic layer shown in Table 3 was formed using the polymer type antistatic agent shown in Table 2 as an antistatic agent and the polypropylene resin shown in Table 1, and was supplied to an inner diameter of 40 mm. The extruder was melted and kneaded, and an antistatic molten resin was obtained by discharging 14 kg/hr.

Each of the obtained foamable molten resin mixture and the intermediate layer is supplied to the merging die by a molten resin or an antistatic molten resin, and is joined together, and the laminated layer is an antistatic molten resin to form two outer layers and is coextensive from the annular die. And three kinds of five-layer cylindrical laminated foams which are laminated in the order of the outer surface of the antistatic layer/intermediate layer/polypropylene resin foam layer/intermediate layer/antistatic layer. The cylindrical laminated foam which has been extruded is obtained by pulling along a cylindrical cooling tube (diameter: 212 mm, magnification ratio: 2.12) which has been subjected to the surface treatment to improve the smoothness, and is cut in the extrusion direction. A laminated foam sheet of the target. The thickness of the entire laminated foam sheet was 4.0 mm, the amount of the meter 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 foam sheet was produced in the same manner as in Example 11 except that a ring-shaped mold having a diameter of 86 mm was used and a cylindrical cooling device (diameter: 212 mm, magnification ratio: 2.47) having an austraic surface which was not subjected to surface treatment was used. The thickness of the entire laminated foam sheet was 4.0 mm, the amount of the meter 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, 18

A tandem extruder consisting of two extruders having an inner diameter of 90 mm and an inner diameter of 120 mm was used as an extruder for producing a polyethylene resin foamed layer of a laminated foam sheet, and an extruder having an inner diameter of 40 mm was used. As an extruder for producing an antistatic layer, in order to coextrude a polyethylene resin foamed layer and an antistatic layer, an annular die having a diameter of 100 mm was used.

First, in order to form a polyethylene resin foamed layer, it is adjusted with respect to 100 parts by weight of polyethylene resin (manufactured by Dow Chemical Co., Ltd., grade: NUC8321) (labeled as LD1). 0.5 parts by weight of a product (PO217K, blended with sodium bicarbonate, sodium citrate), and supplied to a raw material input port of an extruder having an inner diameter of 90 mm, and heated and kneaded, and prepared. A molten resin mixture of about 200 ° C is prepared, and carbon dioxide is injected as a foaming agent in the molten resin mixture, and is 0.4 parts by weight with respect to 100 parts by weight of the polyethylene resin, and secondly, supplied to the above-mentioned 90 mm. An extruder having an inner diameter of 120 mm connected to the downstream side of the extruder was used, and a foaming molten resin mixture was obtained by discharging 98 kg/hr.

On the other hand, the polymer composition of the antistatic layer shown in Table 7 was formed using the polymer type antistatic agent shown in Table 2 as an antistatic agent and the polyethylene resin shown in Table 6, and was supplied to the inner diameter. The extruder of 40 mm was melt-kneaded under heating, and an antistatic molten resin was obtained by discharging 14 kg/hr.

Each of the obtained foamable molten resin mixture and the antistatic molten resin is supplied to a merging die and joined together, and the laminated layer is made of an antistatic molten resin to form two outer layers, and is coextensive from the annular die, and is formed from the outer side. Two types of three-layer cylindrical laminated foams in which the antistatic layer/polyethylene resin foamed layer/antistatic layer are laminated in this order. The cylindrical laminated foam which has been extruded is pulled along a cylindrical cooling pipe (diameter: 212 mm, enlargement ratio: 2.12) which has been subjected to sandblasting of the alumite-resistant surface to increase the smoothness by about twice. The target laminated foam sheet was obtained by cutting in the direction of extrusion. The apparent density of the foamed layer was 0.31 g/cm ³ and the thickness was 2.0 mm, and the thickness of the laminated foamed sheet was 2.1 mm, the amount of the rice flat was 610 g/m ² , and the apparent density was 0.29 g/cm ³ . 650mm. Table 8 shows the physical properties of the laminated foam sheet.

Example 19

In addition to a polyethylene resin (manufactured by Nippon Polyethylene Co., Ltd., grade: HJ560W (labeled as HD2) and a weight ratio of LD1 of 6:4), to form a polyethylene resin foam layer, In the same manner as in Example 17, a laminated foam sheet was obtained. The apparent density of the foamed layer was 0.31 g/cm ³ and the thickness was 2.0 mm, and the thickness of the laminated foamed sheet was 2.1 mm, the amount of the rice flat was 610 g/m ² , and the apparent density was 0.29 g/cm ³ . 650mm. Table 8 shows the physical properties of the laminated foam sheet.

Example 20

A tandem extruder consisting of two extruders having an inner diameter of 90 mm and an inner diameter of 120 mm was used as an extruder for producing a polyethylene resin foamed layer of a laminated foam sheet, and an extruder having an inner diameter of 40 mm was used. As an extruder for manufacturing an antistatic layer, in order to provide a resin layer as an intermediate layer between the antistatic layer and the foam layer, an extruder having an inner diameter of 50 mm is used, and in order to use polyethylene The olefin resin foamed layer, the intermediate layer and the antistatic layered layer were coextruded together, and an annular die having a diameter of 140 mm was used.

First, in order to form a polyethylene resin foamed layer, a bubble conditioner is blended with respect to 100 parts by weight of the polyethylene resin (LD1) (manufactured by Japan Bailingjia Ingelheim Co., Ltd., PO217K, blended with sodium hydrogencarbonate, citric acid 0.75 parts by weight of sodium, and supplied to a raw material input port of an extruder having an inner diameter of 90 mm, and subjected to heat kneading, and a molten resin mixture which has been prepared to have a temperature of about 200 ° C, is pressed into the molten resin mixture. The alkane is used as a foaming agent, and is composed of 2.45 parts by weight based on 100 parts by weight of the polyethylene resin, and then supplied to an extruder having an inner diameter of 120 mm connected to the downstream side of the 90 mm extruder, and the discharge amount is 100 kg. /hr, a foamable molten resin mixture was obtained.

On the other hand, a polyethylene resin (a mixed resin of LD1 and HD2 in a weight ratio of 3:7) was supplied to an extruder having an inner diameter of 50 mm, and melt-kneading was carried out, and an intermediate layer was obtained by discharging 15 kg/hr. Use a molten resin.

In addition, the polymer composition of the antistatic layer shown in Table 7 was used as the antistatic agent and the polyethylene resin shown in Table 6 as the antistatic agent shown in Table 2, and was supplied to an inner diameter of 40 mm. The extruder was melted and kneaded, and an antistatic molten resin was obtained by discharging 18 kg/hr.

Each of the obtained foamable molten resin mixture and the intermediate layer is supplied to the merging die by a molten resin or an antistatic molten resin, and is joined together, and the laminated layer is an antistatic molten resin to form two outer layers and is coextensive from the annular die. Three types of five-layer cylindrical laminated foams which were laminated in the order of the outer surface of the antistatic layer/intermediate layer/polyethylene resin foam layer/intermediate layer/antistatic layer were formed. The cylindrical laminated foam which has been extruded is obtained by pulling along a cylindrical cooling tube (diameter: 350 mm, magnification ratio: 2.5) which has been subjected to the surface treatment to improve the smoothness, and is cut in the extrusion direction. A laminated foam sheet of the target. The thickness of the entire laminated foam sheet was 3.0 mm, the amount of the meter 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 having an inner diameter of 90 mm and an inner diameter of 120 mm was used as an extruder for producing a polyethylene resin foamed layer of a laminated foam sheet, and an extruder having an inner diameter of 40 mm was used. In the extrusion machine 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 having an inner diameter of 65 mm is used, and a polyethylene resin foam layer and an intermediate layer are used. The antistatic layer was laminated and coextruded, and an annular die having a diameter of 180 mm was used.

First, in order to form a polyethylene-based resin foamed layer, a bubble adjusting agent (manufactured by Japan Bailingjia Ingelheim Co., Ltd.) is blended with 100 parts by weight of a polyethylene resin (a mixed resin of a weight ratio of HD2 and LD1 of 6:4). , PO217K, blended with sodium bicarbonate, sodium citrate, 0.75 parts by weight, and supplied to a raw material input port of an extruder having an inner diameter of 90 mm, and subjected to heat kneading, and a molten resin mixture which has been prepared to have a temperature of about 200 ° C. In the molten resin mixture, butane is introduced as a foaming agent, and is made up to 1.3 parts by weight based on 100 parts by weight of the polyethylene resin, and secondarily supplied to the inner diameter connected to the downstream side of the 90 mm extruder. A 120 mm extruder was used, and a foaming molten resin mixture was prepared by discharging 100 kg/hr.

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

In addition, the polymer composition of the antistatic layer shown in Table 7 was used as the antistatic agent and the polyethylene resin shown in Table 6 as the antistatic agent shown in Table 2, and was supplied to an inner diameter of 40 mm. The extruder was melted and kneaded, and an antistatic molten resin was obtained by discharging 11 kg/hr.

Each of the obtained foamable molten resin mixture and the intermediate layer is supplied to the merging die by a molten resin or an antistatic molten resin, and is joined together, and the laminated layer is an antistatic molten resin to form two outer layers and is coextensive from the annular die. Three types of five-layer cylindrical laminated foams which were laminated in the order of the outer surface of the antistatic layer/intermediate layer/polyethylene resin foam layer/intermediate layer/antistatic layer were formed. The cylindrical laminated foam which has been extruded is obtained by pulling along a cylindrical cooling tube (diameter: 350 mm, magnification ratio: 1.9) which has been subjected to the surface treatment to improve the smoothness, and is cut in the extrusion direction. A laminated foam sheet of the target. The thickness of the entire laminated foam sheet was 4.0 mm, the amount of the meter 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.

[Thermal formability evaluation 1 (evaluation of formability and mold release property during hot forming)]

By using a single-shot vacuum forming machine (manufactured by Asano Research Co., Ltd.: FSK type), a part disk mold having an outer dimension of 340 mm × 240 mm and a depth of 43 mm is used, and by way of Examples 1 to 10, 13, 17 to 19 and comparison The laminated foam sheets obtained in Examples 3 and 5 were subjected to thermoforming, and a disk-shaped formed body was obtained. In Examples 1 to 10, 17 to 19, the laminated foam sheets of Comparative Examples 3 and 5 were able to obtain a shaped body such as a mold, and there was no uneven stretching, the shape of the molded body, and the formed body was removed from the mold. The modulus is good. The laminated foam sheet of Example 13 was When the molded body is released from the mold, the resistance is large, and the shape of the formed body is incomplete at the time of demolding, and the mold release property is insufficient.

[Thermal Formability Evaluation 2 (Evaluation of Warpage of Plate-Shaped Foam)]

The laminated foam sheets obtained by the examples 11, 12, 16, 20 and 21 were self-assembled in a heating furnace at 250 ° C (however, in a heating furnace of 200 ° C in Examples 20 and 21). The both sides were heated and plated, and a plate-like laminated foam was obtained. The warpage of the obtained plate-like foam was measured, and the thermoformability of the laminated foam sheet was evaluated in accordance with the following criteria. It can be seen that the less the warpage, the more excellent the thermoformability of the laminated foam sheet. Further, the measurement of the warpage of the foam was carried out in the following manner. A square sample having a size of 500 mm × 500 mm was cut out from the vicinity of the center portion of the plate-shaped foam. The cut sample was placed on a water platform, and the distance from the lower surface of the sample to the top of the platform on which the sample was placed was measured at four points in the central portion of each of the four sides of the square at this time. Next, the sample was turned over and the same measurement was performed. In the measurement result of the total of 8 points, the maximum value L (mm) was used, and the warpage (%) of the plate-shaped foam was calculated by the following formula (3).

[Math 3] Warpage (%) = L (mm) / (length of one side of the square (500 mm)) × 100... (3)

The laminated foam sheets of Examples 11, 12, 20 and 21 had a warpage of 1% or less. However, in the laminated foam sheets of Example 16, warpage of warpage of more than 1% was observed.

Industry availability

The polyolefin-based resin laminated foamed sheet of the present invention exhibits excellent static electricity dissipation with little or no charge, and has a beautiful surface and excellent thermoformability, and is only known as an antistatic product. It is useful as a sheet for thermoforming such as an electronic component, particularly a packaged article such as a precision electronic component, which exhibits a high degree of antistatic function.

Claims (6)

A polyolefin-based resin laminated foam sheet in which an antistatic layer is laminated on at least one side of a polyolefin resin foamed layer by a co-extrusion method using a ring-shaped mold to form a laminated foam sheet of a surface layer. The polyolefin resin laminated foam sheet is characterized in that the antistatic layer is made of a thermoplastic resin: 25% by weight or more and less than 70% by weight, and a polymer type antistatic agent: more than 30% by weight and 75% by weight. The composition is as follows (however, the sum of the two is 100% by weight), and the antistatic layer has a melt viscosity of 250 Pa at 190 ° C and a shear rate of 100 s ^-1 . In the above, the amount of the antistatic layer to be laminated is 5 g/m ² or more of the average single-faced rice layer of the foamed layer, and the initial band voltage at the time of application of 10 kV for 30 seconds on the antistatic layer is 50 V or less. The polyolefin resin laminated foam sheet of claim 1, wherein the antistatic layer has a melt viscosity of 350 Pa at 190 ° C and a shear rate of 100 s ^-1 . s or more, and the melt drawing at 175 ° C is 60 m / min or more. The polyolefin resin laminated foam sheet of the second aspect of the invention, wherein the ratio of the average bubble diameter in the width direction of the laminated foam sheet to the average bubble diameter in the thickness direction, and the average bubble diameter in the extrusion direction are relative to the thickness The average bubble diameter ratio of the directions is 1.0 to 2.0. The polyolefin-based resin laminated foam sheet according to the first aspect of the invention, wherein the polyolefin-based resin foamed layer is a polypropylene-based resin foamed layer having an apparent density of from 0.06 g/cm ³ to 0.6 g/cm ³ . The polyolefin-based resin laminated foam sheet of the fourth aspect of the invention, wherein the laminated foam sheet has a heat shrinkage ratio in the extrusion direction and the width direction at 190 ° C of 2% or less. A polyolefin-based resin foam molded article obtained by thermoforming a polyolefin-based resin laminated foam sheet according to item 3 of the above-mentioned patent application.