WO2016152878A1 - Production method for polyethylene-based resin extruded foam sheets, polyethylene-based resin extruded foam sheet, and interleaving paper for glass plates using same - Google Patents

Production method for polyethylene-based resin extruded foam sheets, polyethylene-based resin extruded foam sheet, and interleaving paper for glass plates using same Download PDF

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Publication number
WO2016152878A1
WO2016152878A1 PCT/JP2016/059055 JP2016059055W WO2016152878A1 WO 2016152878 A1 WO2016152878 A1 WO 2016152878A1 JP 2016059055 W JP2016059055 W JP 2016059055W WO 2016152878 A1 WO2016152878 A1 WO 2016152878A1
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WO
WIPO (PCT)
Prior art keywords
polyethylene
foam sheet
antistatic agent
extruded foam
density polyethylene
Prior art date
Application number
PCT/JP2016/059055
Other languages
French (fr)
Japanese (ja)
Inventor
青木　健
西本　敬
Original Assignee
株式会社ジェイエスピー
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2015108856A external-priority patent/JP6506619B2/en
Application filed by 株式会社ジェイエスピー filed Critical 株式会社ジェイエスピー
Priority to KR1020177027914A priority Critical patent/KR102392965B1/en
Priority to CN201680018140.9A priority patent/CN107428056B/en
Priority to US15/559,148 priority patent/US10717840B2/en
Publication of WO2016152878A1 publication Critical patent/WO2016152878A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
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    • B65D57/00—Internal frames or supports for flexible articles, e.g. stiffeners; Separators for articles packaged in stacks or groups, e.g. for preventing adhesion of sticky articles
    • B65D57/002—Separators for articles packaged in stacks or groups, e.g. stacked or nested
    • B65D57/003—Separators for articles packaged in stacks or groups, e.g. stacked or nested for horizontally placed articles, i.e. for stacked or nested articles
    • B65D57/004—Separators for articles packaged in stacks or groups, e.g. stacked or nested for horizontally placed articles, i.e. for stacked or nested articles the articles being substantially flat panels, e.g. wooden planks
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    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/718—Weight, e.g. weight per square meter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/72—Density
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/732—Dimensional properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/04—Polyethylene
    • B32B2323/046—LDPE, i.e. low density polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
    • B32B2457/202—LCD, i.e. liquid crystal displays
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2457/00—Electrical equipment
    • B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
    • B32B2457/204—Plasma displays
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
    • C08J2201/03—Extrusion of the foamable blend
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/02—CO2-releasing, e.g. NaHCO3 and citric acid
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/20—Ternary blends of expanding agents
    • C08J2203/204—Ternary blends of expanding agents of chemical foaming agent and physical blowing agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2453/00—Characterised by the use of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives of such polymers

Definitions

  • the present invention relates to a novel method for producing a polyethylene-based resin extruded foam sheet, a novel polyethylene-based resin extruded foam sheet, and a glass sheet interleaf using the same.
  • foam sheet Polyethylene resin extruded foam sheet (hereinafter also referred to as foam sheet) has excellent antistatic function, flexibility and cushioning properties, and can prevent damage and damage to the packaged goods. It has been widely used as a material. In recent years, in order to prevent damage to the surface of glass substrates during the packaging and transport of glass substrates for image display devices such as liquid crystal displays, plasma displays, and electroluminescent displays, as development of flat-screen TVs and demand increases. In addition, a foam sheet having an antistatic performance is used as a slip sheet disposed between glass plates (Patent Documents 1 and 2).
  • glass plates with various thicknesses have been developed as glass plates for image display devices such as liquid crystal panels. Recently, from the viewpoints of weight reduction, energy saving, production cost, etc., the thickness is about 0.5 mm.
  • the following extremely thin glass plates are also being produced. If a thick foam sheet having a thickness of about 1 mm to 2 mm as in the conventional case is used as a thin sheet of such a thin glass plate, not only will the loading efficiency be reduced, but the thickness of the interleaf sheet will be too thick for the glass plate. Depending on how the load is applied, the glass plate may be damaged.
  • Patent Document 3 a polyethylene-based resin extruded foam sheet having an average thickness of 0.5 mm or less by using a specific cell regulator or the like. 4).
  • These polyethylene resin extruded foam sheets are high-quality ones that prevent or suppress the generation of small holes and through-holes even when the average thickness is 0.5 mm or less, and have excellent antistatic performance and buffering properties. It is what has.
  • the above polyethylene-based resin extruded foam sheet can be said to be suitable as an interleaving sheet for a thin glass plate, it is also capable of stably producing small holes, through-holes, etc. even in medium- to long-term continuous production over 2 to 7 days.
  • a high-quality polyethylene resin-extruded foamed sheet that is prevented and suppressed from being generated and that exhibits excellent antistatic performance.
  • the present invention has been made in view of the above-described circumstances, and has high quality and excellent strength in which the generation of small holes and through-holes is prevented / suppressed even in the medium- to long-term continuous production despite the extremely small thickness.
  • the present invention provides a novel polyethylene-based resin extruded foam sheet suitable as a glass plate interleaf, which has both buffering properties and sufficient antistatic performance, a novel polyethylene-based resin foam sheet, and a glass plate using the same The purpose is to provide slip sheets.
  • the present invention provides a novel polyethylene resin extruded foam sheet described below, a novel polyethylene resin extruded foam sheet, and a glass sheet interleaf using the same.
  • ⁇ 2> The method for producing a polyethylene resin extruded foam sheet according to ⁇ 1>, wherein the polymer antistatic agent has a melting point of 120 ° C. or lower.
  • the ratio of the melt flow rate of the low density polyethylene to the melt flow rate of the polymer type antistatic agent is 2 or less.
  • ⁇ 1> or ⁇ 2> characterized in that the method for producing a polyethylene resin extruded foam sheet.
  • ⁇ 4> The polyethylene system according to any one of ⁇ 1> to ⁇ 3>, wherein 3 to 25 parts by mass of a polymeric antistatic agent is blended with 100 parts by mass of the low-density polyethylene.
  • the manufacturing method of the present invention not only in a short period of several hours but also in medium to long-term continuous production over several days, it has a high quality and thickness that prevents and suppresses the generation of small holes and through holes. It is possible to obtain a polyethylene resin foam sheet that is extremely thin and exhibits excellent antistatic performance.
  • the novel polyethylene-based resin foam sheet according to the present invention has a high quality in which the generation of small holes and through-holes is prevented / suppressed even though the thickness is extremely thin, and sufficient antistatic performance Is expressed. Therefore, the novel polyethylene-based resin foam sheet of the present invention is used for transporting and packing thin glass plates for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays, in particular where antistatic functions are strongly required. The demand is widely expected to be used as a glass sheet for preventing damage at the time. Moreover, the novel polyethylene-based resin foam sheet of the present invention can be continuously produced over a medium to long term, and is a foam sheet having extremely high production efficiency industrially.
  • the polyethylene resin extruded foam sheet of the present invention (hereinafter also simply referred to as a foam sheet) is produced by extruding and foaming a foamable molten resin composition containing low density polyethylene, a physical foaming agent and an antistatic agent,
  • the method for producing a foamed sheet of the present invention supplies a material for forming the foamed sheet, such as low density polyethylene, an antistatic agent, and other additives such as an air conditioner that are added as necessary, to the extruder. And kneaded at about 200 ° C. to obtain a molten resin composition. Next, a physical foaming agent is press-fitted into the molten resin composition and further kneaded to obtain a foamable molten resin composition in an extruder. Next, the foamable molten resin composition is cooled to an appropriate foaming temperature.
  • a material for forming the foamed sheet such as low density polyethylene, an antistatic agent, and other additives such as an air conditioner that are added as necessary.
  • the appropriate foaming temperature of the foamable molten resin composition is a temperature at which a foamed layer can be easily obtained, and is in the range of [melting point + 0 ° C.] to [melting point + 15 ° C.] of low-density polyethylene. It is preferably in the range of [melting point + 2 ° C.] to [melting point + 10 ° C.].
  • the foamable molten resin composition is introduced into an annular die and extruded from the die tip lip into the atmosphere to foam the foamable molten resin composition, thereby producing a cylindrical extruded foam.
  • a foamed sheet can be obtained by cutting along the extrusion direction while taking up the cylindrical extruded foam while expanding (blowing up) it with a mandrel.
  • Forming material for foam sheet In the production method of the present invention, as described above, a foamable molten resin composition containing low density polyethylene, an antistatic agent, a physical foaming agent, and a cell regulator and other additives as necessary is extruded and foamed. To form. Below, the material used in order to shape
  • the low-density polyethylene having a long chain branching structure, density can be used polyethylene of less than 900 kg / m 3 or more 930 kg / m 3.
  • the resin exhibits good foaming properties, and the foamed sheet obtained is excellent in buffer characteristics.
  • the density of the low density polyethylene is preferably 910 kg / m 3 or more and 925 kg / m 3 or less.
  • the melting point of the low density polyethylene is preferably 100 to 120 ° C, more preferably 105 to 115 ° C.
  • the melting point of the low density polyethylene can be measured by a method according to JIS K7121-1987.
  • the mixture is heated and melted by raising the temperature from 40 ° C. to 200 ° C. at 10 ° C./min, kept at that temperature for 10 minutes, and then 10 ° C./min to 40 ° C.
  • the melting peak is obtained by raising the temperature again from a heating rate of 40 ° C. to 200 ° C. at 10 ° C./min.
  • the temperature of the top of the largest melting peak among the obtained melting peaks is made into melting
  • the melt flow rate of the low density polyethylene is preferably 5 g / 10 minutes or more, more preferably 10 g / 10 minutes or more, and further preferably 15 g / 10 minutes or more.
  • the melt flow rate is a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210-1: 2014.
  • the melting point and melt flow rate of the mixture are specified by the melting point and melt flow rate measured with respect to those previously melt-kneaded with an extruder.
  • Examples of commercially available products of low density polyethylene preferably used in the present invention include “Product name NUC8321” (melt flow rate 1.9 g / 10 min, melting point 112 ° C.) manufactured by NUC.
  • the low-density polyethylene includes other polyethylene resins, polypropylene resins, polystyrene resins, and other thermoplastic resins, ethylene propylene rubber, styrene-butadiene-styrene block copolymer, as long as the objects and effects of the present invention are not impaired.
  • An elastomer such as a polymer may be included.
  • the other polyethylene-based resin is a resin having an ethylene component unit of 50 mol% or more, and specifically includes high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, and ethylene-vinyl acetate copolymer. Ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and the like, and a mixture of two or more thereof.
  • the amount of resin and elastomer other than low-density polyethylene is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of low-density polyethylene.
  • a resin other than the low-density polyethylene and an elastomer can be kneaded together with the low-density polyethylene to form a base resin constituting the foamable molten resin composition.
  • Antistatic agent In the production method of the present invention, it is necessary to use a polymer type antistatic agent as the antistatic agent.
  • This polymer type antistatic agent has a melting point difference from the low density polyethylene in the range of ⁇ 10 ° C. to + 10 ° C. and a melt flow rate of 10 g / 10 min or more.
  • polyethylene-based resin extrusion foam that exhibits high-quality and excellent antistatic function, which prevents and suppresses the generation of small holes and through-holes even in continuous production over the medium to long term A sheet can be obtained.
  • the polymer antistatic agent used in the present invention has a low melting point and a high melt flow rate. In this way, it is considered that the precipitation of crystals that cause the generation of small holes and through holes in the annular die is prevented and suppressed.
  • the difference between the melting point of the polymer antistatic agent used in the present invention and the melting point of the low density polyethylene is ⁇ 10 ° C. to + 10 ° C.
  • the melting point difference is preferably ⁇ 8 ° C. to + 8 ° C., more preferably ⁇ 7 ° C. to + 7 ° C., from the viewpoint of obtaining a high-quality product in further continuous operation.
  • the melting point of the polymer antistatic agent is preferably 125 ° C. or lower, and more preferably 120 ° C. or lower.
  • the lower limit of the melting point is about 100 ° C.
  • the melting point of the polymer antistatic agent is determined by the same method as that for the low density polyethylene.
  • the melt flow rate of the polymer antistatic agent used in the present invention is 10 g / 10 min or more, preferably 20 g / 10 min or more, and more preferably 30 g / 10 min or more.
  • an upper limit of about 100 g / 10 minutes is preferable because the antistatic agent has excellent fluidity and exhibits antistatic performance more effectively.
  • the melt flow rate of the polymer antistatic agent is a value measured at a temperature of 190 ° C. and a load of 2.16 kg according to JIS K7210-1: 2014.
  • the ratio of the melt flow rate of the low density polyethylene B to the melt flow rate of the polymer type antistatic agent may be 2 or less. Preferably, it is 1 or less, more preferably 0.8 or less.
  • the ratio is in the above range, the polymer type antistatic agent is dispersed in a network or a layer, and excellent antistatic performance can be exhibited more effectively.
  • the lower limit of the ratio is preferably about 0.01 or more.
  • the polymer type antistatic agent preferably used in the present invention comprises a block copolymer of polyether and polyolefin, and commercially available products include, for example, PELECTRON LMP (melting point: 114 ° C., manufactured by Sanyo Chemical Industries, Ltd.). , Melt flow rate 30 g / 10 min).
  • the number average molecular weight of the polymer type antistatic agent used in the present invention is preferably 2000 or more, more preferably 2000 to 100,000, still more preferably 5000 to 80,000.
  • the upper limit of the number average molecular weight of the polymer type antistatic agent is approximately 500,000.
  • the above number average molecular weight is determined using high temperature gel permeation chromatography.
  • the sample concentration is 3 mg / ml using orthodichlorobenzene as a solvent
  • the column temperature is set to 135 ° C. using polystyrene as a reference substance. Is a measured value.
  • the kind of said solvent and column temperature are suitably changed according to the kind of polymeric antistatic agent.
  • the blending amount of the polymer type antistatic agent in the foam is sufficient with respect to 100 parts by mass of the low density polyethylene constituting the foam in order to obtain a foam sheet having sufficient antistatic properties and high quality.
  • the amount is preferably 2 to 30 parts by mass, more preferably 3 to 25 parts by mass, and still more preferably 5 to 20 parts by mass.
  • the surface resistivity of the surface of the foamed sheet can be set to 1 ⁇ 10 7 to 1 ⁇ 10 13 ⁇ by adding the polymer type antistatic agent. If the surface resistivity is within the above range, the foam sheet exhibits sufficient antistatic properties. From the above viewpoint, the surface resistivity is preferably 5 ⁇ 10 12 ⁇ or less, and more preferably 1 ⁇ 10 12 ⁇ or less.
  • the surface resistivity in the present invention is measured according to JIS K6271: 2008 after adjusting the state of the following test piece. Specifically, by leaving a test piece (length 100 mm ⁇ width 100 mm ⁇ thickness: thickness of measurement object) cut out from a foam sheet as a measurement object for 36 hours in an atmosphere at a temperature of 20 ° C. and a relative humidity of 30%. Condition the specimen. Next, a voltage is applied to the test piece under the condition of an applied voltage of 500 V in an atmosphere of a temperature of 20 ° C. and a relative humidity of 30%. The surface resistivity after 1 minute from the start of voltage application is measured.
  • the physical foaming agent may be an organic or inorganic physical foaming agent.
  • the organic physical foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, and ethyl chloride.
  • chlorohydrocarbons such as 1,1,1,2-tetrafluoroethane, fluorinated hydrocarbons such as 1,1-difluoroethane, ethers such as dimethyl ether and methyl ethyl ether, and alcohols such as methanol and ethanol.
  • Examples of the inorganic physical foaming agent include oxygen, nitrogen, carbon dioxide, air, and water. These physical foaming agents can be used in combination of two or more. Among these, an organic physical foaming agent is preferable from the viewpoint of foaming properties, and among them, those mainly composed of normal butane, isobutane, or a mixture thereof are particularly preferable.
  • the addition amount of the physical foaming agent is adjusted according to the type and the apparent density of the target foam sheet. For example, when a foamed sheet having an apparent density of 20 to 450 kg / m 3 is obtained using a physical foaming agent such as a butane mixture of 30% by mass of isobutane and 70% by mass of normal butane as the physical foaming agent, The amount is 4 to 35 parts by mass, preferably 5 to 30 parts by mass, and more preferably 6 to 25 parts by mass with respect to 100 parts by mass of the base resin.
  • the air conditioner can be supplied to the extruder together with the low density polyethylene.
  • An inorganic powder or a chemical foaming agent can be used as the bubble regulator.
  • the inorganic powder include talc, zeolite, silica, calcium carbonate and the like.
  • Examples of the chemical foaming agent include azodicarbonamide, hydrazodicarbonamide, azobisisobutyronitrile, sodium hydrogen carbonate (sodium bicarbonate), and citric acid monoalkali metal salts such as sodium hydrogen carbonate and citric acid or monosodium citrate.
  • sodium bicarbonate-citric acid based chemical foaming agent a sodium bicarbonate-citric acid based chemical foaming agent is preferable in order to obtain a foamed sheet having a small cell diameter and excellent buffering properties.
  • the average particle size is more preferably 4 to 7 ⁇ m.
  • the maximum particle size of the chemical foaming agent is preferably 100 ⁇ m or less, and more preferably 80 ⁇ m or less.
  • the average particle diameter means a median diameter (d50) measured by laser diffraction / scattering particle size distribution measurement.
  • the maximum particle size of the above chemical foaming agent is about 1 to 3 mg of particles randomly sampled from the chemical foaming agent. Is the maximum particle diameter of the chemical foaming agent.
  • the addition amount of the cell regulator is preferably 0.1 to 3 parts by mass, more preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the base resin constituting the foamable molten resin composition. It is. It is preferable for the amount added to be in the above range because the bubble diameter can be easily adjusted to a desired range.
  • additives In the method of the present invention, in addition to the above components, various additives can be added as long as the effects of the present invention are not impaired.
  • the additive include an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet absorber, a flame retardant, an inorganic filler, an antibacterial agent, and a colorant.
  • the antistatic agent has a melting point difference of + 20 ° C. or more with the low-density polyethylene as the base resin.
  • a polymer antistatic agent having a melting point of about 135 ° C. is used.
  • the polymer type antistatic agent is a foamable molten resin. The polymer melts completely in the composition, and the unmelted polymer antistatic crystal does not precipitate.
  • the foamable molten resin composition when introduced into the annular die as described above, it is cooled to an appropriate foaming temperature, specifically about 120 ° C. (melting point of low-density polyethylene resin + about 10 ° C. or less) ). Since the conventional polymer antistatic agent is about 135 ° C., a part of the polymer antistatic agent melted in the extruder crystallizes and precipitates at such a cooling temperature. Conceivable.
  • the foamable molten resin composition containing the precipitated crystal is extruded in the annular die, the precipitated crystal starts to stay and adhere to the wall surface in the annular die.
  • the amount of residual crystals remaining is small, so the influence on the surface of the foam is small, but in the case of continuous production over a long period of time such as 2 days or 7 days, The amount of residual crystals and the amount of adhered crystals increase drastically, and finally comes into contact with and falls on the surface of the foam, generating small holes and through holes in the foamed sheet, making it impossible to obtain a high-quality foamed sheet.
  • the antistatic agent has a melting point difference within the range of ⁇ 10 ° C. to + 10 ° C. with respect to the low density polyethylene resin, and the melt flow rate is 10 g / 10 min or more. Since the polymer type antistatic agent is used, the extruder is completely melted in the foamable molten resin composition in the same manner as the conventional polymer type antistatic agent, and an unmelted polymer type antistatic agent is used. Crystals do not precipitate.
  • the foamable molten resin composition is cooled to an appropriate foaming temperature as described above, and specifically, the melting point of the low-density polyethylene resin is about + 10 ° C., for example, 120 ° C.
  • the polymer type antistatic agent used in the present invention has a melting point difference within the range of ⁇ 10 ° C. to + 10 ° C. with respect to the low density polyethylene, In the same manner as in the above, it is considered that the polymer melts completely in the annular die and the crystallization of the unmelted polymer antistatic agent is prevented / suppressed.
  • the method for producing a foamed sheet of the present invention prevents and suppresses the generation of small holes and through holes not only in a short period of several hours but also in the medium and long periods of several days. Excellent continuous productivity. Accordingly, in the production of the foamed sheet of the present invention, the foamed sheet can be wound up as a roll having a length of 100 m or more, preferably 300 m or more during production, although it varies depending on the thickness and the length in the width direction.
  • the number of through-holes having a diameter of 1 mm or more present in the polyethylene resin extruded foam sheet is smaller. Specifically, it is preferable that the number of through-holes of 1 mm or more generated in 1 hour after the lapse of 2 days and 7 days from the start of production is less than 3.
  • the thickness (average thickness) of the foamed sheet obtained by the production method of the present invention is 0.05 mm or more and 0.5 mm or less.
  • the lower limit of the average thickness is preferably 0.07 mm, more preferably 0.1 mm, and still more preferably 0.15 mm.
  • the upper limit of the average thickness is preferably 0.4 mm, more preferably 0.35 mm, and still more preferably 0.3 mm.
  • the average thickness of the foam sheet can be measured using an offline thickness measuring machine TOF-4R manufactured by Yamabun Electric Co., Ltd. First, the thickness of the entire width of the foam sheet is measured at intervals of 1 cm. Based on the thickness of the foam sheet measured at intervals of 1 cm, the arithmetic average thickness of the full width is obtained. In addition, the foam sheet used for said measurement uses what adjusted the state for 24 hours or more on conditions of temperature 23 +/- 5 degreeC and relative humidity 50%.
  • the apparent density of the foam sheet obtained by the production method of the present invention is preferably in the range of 20 to 450 kg / m 3 .
  • the apparent density is more preferably 30 to 300 kg / m 3 , and further preferably 50 to 200 kg / m 3 .
  • the apparent density of the foam sheet be determined by the weight per unit area of the foam sheet (g / m 2) divided by the average thickness of the foamed sheet and unit conversion more [kg / m 3] it can.
  • the ratio of the discharge diameter of the annular die to the diameter of the mandrel is preferably 2.2 to 3.8.
  • the above range is preferable because there is no waviness phenomenon in the circumferential direction due to foaming, excellent thickness accuracy, and excellent foamed sheets without excessive flattening of bubbles in the width direction.
  • the novel polyethylene-based resin extruded foam sheet according to the present invention is a high-quality one that prevents and suppresses the generation of small holes and through-holes despite its extremely small thickness, and is sufficient. Expresses antistatic performance.
  • the novel polyethylene-based resin extruded foam sheet of the present invention is used in fields where an antistatic function or the like is strongly required, in particular, for transporting thin glass plates for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays. It is widely and extremely useful as a glass sheet slip for preventing damage during packaging. In addition, it is a foam sheet that can be produced continuously over the medium to long term and is industrially extremely high in production efficiency.
  • Table 1 shows the low-density polyethylene used in the examples and comparative examples.
  • Table 2 shows antistatic agents used in Examples and Comparative Examples.
  • the air conditioner used in Examples and Comparative Examples is a mixture of sodium bicarbonate and monosodium citrate in a weight ratio of 1: 1, and a chemical foaming agent having an average particle diameter (d50) of 6 ⁇ m and a maximum particle diameter of 30 ⁇ m. Using.
  • an extruder having a barrel inner diameter of 115 mm for forming a foam layer and a first extruder (tandem extruder) in which an extruder having a barrel inner diameter of 150 mm was connected to the downstream side thereof were used.
  • the temperature control of the die lip part mold was performed for each of the divided parts obtained by dividing the lip part mold into eight parts.
  • the compounding quantity of the antistatic agent in Table 3, a bubble regulator, and a physical foaming agent represents the mass part of the antistatic agent, a bubble regulator, and a physical foaming agent with respect to 100 mass parts of resin which comprises a foamed layer.
  • Table 4 shows the physical properties of the foam sheets obtained in Examples and Comparative Examples.
  • the foamed sheets obtained in Examples 1 to 3 used a specific polymer type antistatic agent (protection 1: melting point 114 ° C.) having a melting point difference of + 7 ° C. from low density polyethylene.
  • protection 1 melting point 114 ° C.
  • the generation of through-holes on the surface is prevented and suppressed not only in the long-term continuous production of 168 hours (7 days), and in addition, the antistatic performance is improved. It is fully expressed. Therefore, it can be seen that the foamed sheet of the present invention is an industrially extremely valuable foamed sheet that has antistatic performance and can be produced stably and in large quantities.
  • the foamed sheets obtained in Comparative Examples 1 and 2 have a high melting point (135 ° C.) polymer antistatic agent (Band 2 and bamboo 3) having a melting point difference of 28 ° C. from that of low density polyethylene.
  • a high melting point (135 ° C.) polymer antistatic agent Band 2 and bamboo 3 having a melting point difference of 28 ° C. from that of low density polyethylene.
  • the foamed sheet obtained in Comparative Example 3 uses a polymer antistatic agent having a melting point difference of ⁇ 15 ° C. with respect to low density polyethylene (Band prevention 4: melting point 92 ° C.). Although a high-quality foam sheet having no small holes or through holes can be obtained, sufficient antistatic performance is not exhibited. Therefore, as in Comparative Example 4, when the blending amount is increased in order to sufficiently develop the antistatic ability, the foamed sheet is stably produced because the amount of the belt protection 4 having a low melt flow rate is large. It was difficult.
  • the foamed sheet obtained in Comparative Example 5 is in contrast to Example 2, and it can be seen that the antistatic agent having a large melting point difference from the low density polyethylene resin is not suitable for long-term continuous production.
  • the average thickness of the foamed sheet was measured using an offline thickness measuring machine TOF-4R manufactured by Yamabun Electric Co., Ltd. First, the thickness of the foam sheet was measured at intervals of 1 cm. Based on the thickness of the foam sheet measured at intervals of 1 cm, the arithmetic average thickness of the full width was obtained. In addition, the foam sheet used for said measurement used what adjusted the state for 48 hours on the conditions of temperature 23 +/- 5 degreeC and relative humidity 50%.
  • Basis weight of foam sheet The basis weight of the foam sheet is obtained by cutting out a rectangular test piece having a width of 250 mm over the entire width of the foam sheet, and dividing the weight (g) of the test piece by the area of the test piece (sheet width (mm) ⁇ 250 mm). , in terms of the weight of the foamed sheet per 1 m 2 (g), which was used as the basis weight of the foamed sheet (g / m 2).
  • the apparent density of the foam sheet was obtained by dividing the basis weight (g / m 2 ) of the foam sheet obtained by the above method by the average thickness of the foam sheet obtained above.
  • the number of through-holes of 1 mm or more generated in 1 hour is less than 3 poor: The number of through-holes of 1 mm or more generated in 1 hour after 168 hours passed is 3 or more and less than 5 bad: After 168 hours have passed, the number of through-holes of 1 mm or more generated in 1 hour is 5 or more-: cannot be evaluated (foamed sheet cannot be formed)

Abstract

Provided is a production method for polyethylene-based resin extruded foam sheets, in which: a foamable molten resin composition comprising a low-density polyethylene, a physical foaming agent, and an antistatic agent that have been kneaded is extruded and foamed; and polyethylene-based resin extruded foam sheets are formed. The production method for polyethylene-based resin extruded foam sheets is characterized: by the thickness of the foam sheets being 0.05-0.5 mm; and by, using as the antistatic agent, a polymeric antistatic agent that has a melting point within -10-10°C of the low-density polyethylene melting point and a melt flow rate of at least 10 g/10 mins. As a result, a novel polyethylene-based resin extruded foam sheet can be obtained that, regardless of being extremely thin, is high quality, has excellent strength and shock-absorbing properties, prevents/suppresses generation of fine pores or through-holes even after medium to long-term continuous production, exhibits sufficient antistatic properties, and is suitable as an interleaving paper for glass plates.

Description

ポリエチレン系樹脂押出発泡シートの製造方法、ポリエチレン系樹脂押出発泡シート及びそれを用いたガラス板用間紙Production method of polyethylene resin extruded foam sheet, polyethylene resin extruded foam sheet and interleaf paper for glass plate using the same
　本発明は、新規なポリエチレン系樹脂押出発泡シートの製造方法、新規なポリエチレン系樹脂押出発泡シート及びそれを用いたガラス板用間紙に関する。 The present invention relates to a novel method for producing a polyethylene-based resin extruded foam sheet, a novel polyethylene-based resin extruded foam sheet, and a glass sheet interleaf using the same.
　ポリエチレン系樹脂押出発泡シート（以下、発泡シートともいう）は、帯電防止機能、柔軟性及び緩衝性に富み、被包装物の損傷、傷つきを防止できることから、家電製品、ガラス器具、陶器等の包装材料として広く使用されてきた。また、近年、薄型テレビ等の開発、需要拡大に伴い、液晶ディスプレイ、プラズマディスプレイ、エレクトロルミネッセンスディスプレイ等の画像表示機器用のガラス基板の梱包や搬送時における、ガラス基板の表面の損傷を防止するために、ガラス板間に配置される間紙として帯電防止性能を備えた発泡シートが使用されている（特許文献１、２） Polyethylene resin extruded foam sheet (hereinafter also referred to as foam sheet) has excellent antistatic function, flexibility and cushioning properties, and can prevent damage and damage to the packaged goods. It has been widely used as a material. In recent years, in order to prevent damage to the surface of glass substrates during the packaging and transport of glass substrates for image display devices such as liquid crystal displays, plasma displays, and electroluminescent displays, as development of flat-screen TVs and demand increases. In addition, a foam sheet having an antistatic performance is used as a slip sheet disposed between glass plates (Patent Documents 1 and 2).
　これまでに、液晶パネル等の画像表示機器用のガラス板として、種々の厚みのものが開発されてきたが、軽量化、省エネや生産コスト等の面から、最近では、厚みが０．５ｍｍ程度以下という極めて薄いガラス板も生産されるようになってきている。このような薄いガラス板の間紙として、従来のような厚みが１ｍｍ～２ｍｍ程度の厚い発泡シートを用いると、積載効率が低下するだけでなく、ガラス板に対して間紙の厚みが厚くなりすぎるため、荷重のかかり方によってはガラス板が破損するおそれもあった。 Up to now, glass plates with various thicknesses have been developed as glass plates for image display devices such as liquid crystal panels. Recently, from the viewpoints of weight reduction, energy saving, production cost, etc., the thickness is about 0.5 mm. The following extremely thin glass plates are also being produced. If a thick foam sheet having a thickness of about 1 mm to 2 mm as in the conventional case is used as a thin sheet of such a thin glass plate, not only will the loading efficiency be reduced, but the thickness of the interleaf sheet will be too thick for the glass plate. Depending on how the load is applied, the glass plate may be damaged.
　このため、厚みの薄いガラス板に対応する間紙として、厚みの薄い発泡シートの開発が進められているが、厚みが薄い発泡シートを製造しようとすると発泡シートに小穴や貫通孔が発生しやすくなるという問題が生じた。 For this reason, development of a thin foam sheet as a slip sheet corresponding to a thin glass plate is underway. However, if a thin foam sheet is manufactured, small holes and through holes are likely to occur in the foam sheet. The problem of becoming.
　このような問題に対処するために、本発明者等は先に、特有な気泡調整剤等を用いることにより、平均厚みが０．５ｍｍ以下のポリエチレン系樹脂押出発泡シートを開発した（特許文献３、４）。 In order to cope with such a problem, the present inventors have previously developed a polyethylene-based resin extruded foam sheet having an average thickness of 0.5 mm or less by using a specific cell regulator or the like (Patent Document 3). 4).
　これらのポリエチレン系樹脂押出発泡シートは、平均厚みが０．５ｍｍ以下であっても、小孔や貫通孔の発生が防止・抑制された高品質なものであり、優れた帯電防止性能と緩衝性を有するものである。 These polyethylene resin extruded foam sheets are high-quality ones that prevent or suppress the generation of small holes and through-holes even when the average thickness is 0.5 mm or less, and have excellent antistatic performance and buffering properties. It is what has.
特開２００７－２６２４０９号公報JP 2007-262409 A 特開２０１２－２０７６６号公報JP 2012-20766 A 特開２０１４－４３５５３号公報JP 2014-43553 A 国際公開第２０１４／０３０５１３号International Publication No. 2014/030513
　上記ポリエチレン系樹脂押出発泡シートは厚みの薄いガラス板の間紙として好適なものといえるが、さらには、２日～７日等に亘る中長期の連続生産においても安定して小孔や貫通孔等の発生が防止・抑制された高品質で優れた帯電防止性能を発現するポリエチレン系樹脂押出発泡シートの開発が強く求められる。 Although the above polyethylene-based resin extruded foam sheet can be said to be suitable as an interleaving sheet for a thin glass plate, it is also capable of stably producing small holes, through-holes, etc. even in medium- to long-term continuous production over 2 to 7 days. There is a strong demand for the development of a high-quality polyethylene resin-extruded foamed sheet that is prevented and suppressed from being generated and that exhibits excellent antistatic performance.
　本発明は上記した事情に鑑みなされたものであって、厚みが極めて薄いにもかかわらず、中長期の連続生産においても小孔や貫通孔の発生が防止・抑制された高品質で優れた強度と緩衝性を併せ持ち、しかも帯電防止性能も十分に発現する、ガラス板用間紙として好適な新規なポリエチレン系樹脂押出発泡シートの製造方法、新規なポリエチレン系樹脂発泡シート及びそれを用いたガラス板用間紙を提供することを目的とする。 The present invention has been made in view of the above-described circumstances, and has high quality and excellent strength in which the generation of small holes and through-holes is prevented / suppressed even in the medium- to long-term continuous production despite the extremely small thickness. The present invention provides a novel polyethylene-based resin extruded foam sheet suitable as a glass plate interleaf, which has both buffering properties and sufficient antistatic performance, a novel polyethylene-based resin foam sheet, and a glass plate using the same The purpose is to provide slip sheets.
　本発明は、以下に記載の新規なポリエチレン系樹脂押出発泡シートの製造方法、新規なポリエチレン系樹脂押出発泡シート及びそれを用いたガラス板用間紙を提供する。 The present invention provides a novel polyethylene resin extruded foam sheet described below, a novel polyethylene resin extruded foam sheet, and a glass sheet interleaf using the same.
＜１＞低密度ポリエチレン、物理発泡剤及び帯電防止剤を含有する発泡性溶融樹脂組成物を押出して発泡させて、ポリエチレン系樹脂押出発泡シートを製造する方法であって、発泡シートの厚みが０．０５～０．５ｍｍの範囲内であり、帯電防止剤として、低密度ポリエチレンとの融点差が－１０～＋１０℃の範囲内の融点を有し、かつメルトフローレイトが１０ｇ／１０分以上である高分子型帯電防止剤を用いることを特徴とするポリエチレン系樹脂押出発泡シートの製造方法。
＜２＞前記高分子型帯電防止剤の融点が１２０℃以下であることを特徴とする＜１＞に記載のポリエチレン系樹脂押出発泡シートの製造方法。
＜３＞高分子型帯電防止剤のメルトフローレイトに対する低密度ポリエチレンのメルトフローレイトの比（低密度ポリエチレンのメルトフローレイト／高分子型帯電防止剤のメルトフローレイト）が２以下であることを特徴とする＜１＞または＜２＞に記載のポリエチレン系樹脂押出発泡シートの製造方法。
＜４＞前記低密度ポリエチレン１００質量部に対して、高分子型帯電防止剤が３～２５質量部配合されていることを特徴とする＜１＞から＜３＞のいずれかに記載のポリエチレン系樹脂押出発泡シートの製造方法。
＜５＞帯電防止剤を含有し、基材樹脂が低密度ポリエチレンである低密度ポリエチレン系樹脂押出発泡シートであって、厚みが０．０５ｍｍ～０．５ｍｍの範囲内、見掛け密度が２０～４５０ｋｇ／ｍ３の範囲内であり、帯電防止剤が、低密度ポリエチレンとの融点差が－１０℃～＋１０℃の範囲内の融点を有し、かつメルトフローレイトが１０ｇ／１０分以上である高分子型帯電防止剤であることを特徴とするポリエチレン系樹脂押出発泡シート。
＜６＞＜５＞に記載のポリエチレン系樹脂押出発泡シートからなるガラス板用間紙。 <1> A method for producing a polyethylene resin extruded foam sheet by extruding and foaming a foamable molten resin composition containing low-density polyethylene, a physical foaming agent and an antistatic agent, wherein the thickness of the foamed sheet is 0 0.05 to 0.5 mm, and the antistatic agent has a melting point difference from the low density polyethylene of −10 to + 10 ° C. and a melt flow rate of 10 g / 10 min or more. A method for producing a polyethylene-based resin extruded foam sheet, wherein a polymer type antistatic agent is used.
<2> The method for producing a polyethylene resin extruded foam sheet according to <1>, wherein the polymer antistatic agent has a melting point of 120 ° C. or lower.
<3> The ratio of the melt flow rate of the low density polyethylene to the melt flow rate of the polymer type antistatic agent (the melt flow rate of the low density polyethylene / the melt flow rate of the polymer type antistatic agent) is 2 or less. <1> or <2> characterized in that the method for producing a polyethylene resin extruded foam sheet.
<4> The polyethylene system according to any one of <1> to <3>, wherein 3 to 25 parts by mass of a polymeric antistatic agent is blended with 100 parts by mass of the low-density polyethylene. A method for producing a resin extruded foam sheet.
<5> A low density polyethylene resin extruded foam sheet containing an antistatic agent and having a base resin of low density polyethylene, having a thickness in the range of 0.05 mm to 0.5 mm and an apparent density of 20 to 450 kg. / m is in the range of 3, antistatic agent, a high melting point difference between the low-density polyethylene has a melting point in the range of -10 ℃ ~ + 10 ℃, and the melt flow rate is 10 g / 10 min or more A polyethylene resin extruded foam sheet, which is a molecular type antistatic agent.
<6> Interleaving paper for a glass plate comprising the polyethylene resin extruded foam sheet according to <5>.
　本発明の製造方法によれば、数時間といった短期間はもちろんのこと、数日間に亘る中長期間の連続生産においても、小孔や貫通孔の発生が防止・抑制された高品質で、厚みが極めて薄く優れた帯電防止性能を発現する、ポリエチレン系樹脂発泡シートを得ることができる。 According to the manufacturing method of the present invention, not only in a short period of several hours but also in medium to long-term continuous production over several days, it has a high quality and thickness that prevents and suppresses the generation of small holes and through holes. It is possible to obtain a polyethylene resin foam sheet that is extremely thin and exhibits excellent antistatic performance.
　また、本発明に係る新規なポリエチレン系樹脂発泡シートは、厚みが極めて薄いにもかかわらず、小孔や貫通孔の発生が防止・抑制された高品質なものであり、しかも十分な帯電防止性能を発現する。
　したがって、本発明の新規なポリエチレン系樹脂発泡シートは、帯電防止機能等が強く要求される分野、殊に液晶ディスプレイ、プラズマディスプレイ、エレクトロルミネッセンスディスプレイ等の画像表示機器用の薄型ガラス板の搬送や梱包時の損傷を防止するためのガラス板用間紙として広くその需要が見込まれる。
　また、本発明の新規なポリエチレン系樹脂発泡シートは、中長期に亘って連続的に製造することが可能であり、工業的に極めて生産効率の高い発泡シートである。 In addition, the novel polyethylene-based resin foam sheet according to the present invention has a high quality in which the generation of small holes and through-holes is prevented / suppressed even though the thickness is extremely thin, and sufficient antistatic performance Is expressed.
Therefore, the novel polyethylene-based resin foam sheet of the present invention is used for transporting and packing thin glass plates for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays, in particular where antistatic functions are strongly required. The demand is widely expected to be used as a glass sheet for preventing damage at the time.
Moreover, the novel polyethylene-based resin foam sheet of the present invention can be continuously produced over a medium to long term, and is a foam sheet having extremely high production efficiency industrially.
　本発明のポリエチレン系樹脂押出発泡シート（以下、単に発泡シートともいう）の製造方法は、低密度ポリエチレン、物理発泡剤及び帯電防止剤を含有する発泡性溶融樹脂組成物を押出して発泡させて、ポリエチレン系樹脂押出発泡シートを製造する方法であって、発泡シートの厚みが０．０５～０．５ｍｍの範囲内であり、帯電防止剤として、低密度ポリエチレンとの融点差が－１０～＋１０℃の範囲内の融点を有し、かつメルトフローレイトが１０ｇ／１０分以上である高分子型帯電防止剤を用いることを特徴としている。 The polyethylene resin extruded foam sheet of the present invention (hereinafter also simply referred to as a foam sheet) is produced by extruding and foaming a foamable molten resin composition containing low density polyethylene, a physical foaming agent and an antistatic agent, A method for producing a polyethylene resin extruded foam sheet, wherein the thickness of the foam sheet is in the range of 0.05 to 0.5 mm, and the melting point difference from low density polyethylene is −10 to + 10 ° C. as an antistatic agent. It is characterized by using a polymer type antistatic agent having a melting point within the range of 10 and having a melt flow rate of 10 g / 10 min or more.
（発泡シートの製造方法）
　本発明の発泡シートの製造方法は、発泡シートを成形するための材料である、低密度ポリエチレン、帯電防止剤、その他必要に応じて添加される気泡調整剤等の添加剤を押出機に供給して２００℃程度に加熱混練して溶融樹脂組成物とする。ついで、この溶融樹脂組成物に物理発泡剤を圧入して更に混練し、押出機内で発泡性溶融樹脂組成物とする。ついで、この発泡性溶融樹脂組成物を発泡適正温度に冷却する。 (Method for producing foam sheet)
The method for producing a foamed sheet of the present invention supplies a material for forming the foamed sheet, such as low density polyethylene, an antistatic agent, and other additives such as an air conditioner that are added as necessary, to the extruder. And kneaded at about 200 ° C. to obtain a molten resin composition. Next, a physical foaming agent is press-fitted into the molten resin composition and further kneaded to obtain a foamable molten resin composition in an extruder. Next, the foamable molten resin composition is cooled to an appropriate foaming temperature.
　ここで、発泡性溶融樹脂組成物の発泡適正温度とは、発泡層が容易に得られる温度のことであり、低密度ポリエチレンの［融点＋０℃］～［融点＋１５℃］の範囲とすることが好ましく、より好ましくは［融点＋２℃］～［融点＋１０℃］の範囲である。 Here, the appropriate foaming temperature of the foamable molten resin composition is a temperature at which a foamed layer can be easily obtained, and is in the range of [melting point + 0 ° C.] to [melting point + 15 ° C.] of low-density polyethylene. It is preferably in the range of [melting point + 2 ° C.] to [melting point + 10 ° C.].
　そして、上記発泡性溶融樹脂組成物を環状ダイ内に導入しそのダイ先端リップ部から大気中に押出して、発泡性溶融樹脂組成物を発泡させることにより、筒状押出発泡体を製造し、この筒状押出発泡体をマンドレルにて拡張（ブローアップ）しつつ引取りながら押出方向に沿って切り開くことにより発泡シートを得ることができる。 Then, the foamable molten resin composition is introduced into an annular die and extruded from the die tip lip into the atmosphere to foam the foamable molten resin composition, thereby producing a cylindrical extruded foam. A foamed sheet can be obtained by cutting along the extrusion direction while taking up the cylindrical extruded foam while expanding (blowing up) it with a mandrel.
（発泡シートの形成材料）
　本発明の製造方法においては、上記したように、低密度ポリエチレン、帯電防止剤、物理発泡剤、必要に応じて気泡調整剤及びその他の添加剤を配合した発泡性溶融樹脂組成物を押出発泡させることにより形成する。以下に、発泡シートを成形するために用いる材料について詳述する。 (Forming material for foam sheet)
In the production method of the present invention, as described above, a foamable molten resin composition containing low density polyethylene, an antistatic agent, a physical foaming agent, and a cell regulator and other additives as necessary is extruded and foamed. To form. Below, the material used in order to shape | mold a foamed sheet is explained in full detail.
（低密度ポリエチレン）
　低密度ポリエチレンとしては、長鎖分岐構造を有する、密度が９００ｋｇ／ｍ３以上９３０ｋｇ／ｍ３未満のポリエチレンを用いることができる。上記樹脂は、良好な発泡性を示し、得られる発泡シートは緩衝特性において優れたものとなる。上記観点から低密度ポリエチレンの密度は９１０ｋｇ／ｍ３以上９２５ｋｇ／ｍ３以下であることが好ましい。前記低密度ポリエチレンの融点は１００～１２０℃が好ましく、１０５～１１５℃がさらに好ましい。前記低密度ポリエチレンの融点は、ＪＩＳ Ｋ７１２１－１９８７に準拠する方法により測定することができる。具体的には、示差走査熱量計を用いて、４０℃から２００℃まで１０℃／分にて昇温することにより加熱溶融させ、その温度に１０分間保った後、４０℃まで１０℃／分にて冷却する熱処理後、再度、加熱速度４０℃から２００℃まで１０℃／分にて昇温することにより融解ピークを得る。そして得られた融解ピークのうち最も大きな融解ピークの頂点の温度を融点とする。 (Low density polyethylene)
The low-density polyethylene, having a long chain branching structure, density can be used polyethylene of less than 900 kg / m 3 or more 930 kg / m 3. The resin exhibits good foaming properties, and the foamed sheet obtained is excellent in buffer characteristics. From the above viewpoint, the density of the low density polyethylene is preferably 910 kg / m 3 or more and 925 kg / m 3 or less. The melting point of the low density polyethylene is preferably 100 to 120 ° C, more preferably 105 to 115 ° C. The melting point of the low density polyethylene can be measured by a method according to JIS K7121-1987. Specifically, using a differential scanning calorimeter, the mixture is heated and melted by raising the temperature from 40 ° C. to 200 ° C. at 10 ° C./min, kept at that temperature for 10 minutes, and then 10 ° C./min to 40 ° C. After the heat treatment cooled at, the melting peak is obtained by raising the temperature again from a heating rate of 40 ° C. to 200 ° C. at 10 ° C./min. And the temperature of the top of the largest melting peak among the obtained melting peaks is made into melting | fusing point.
　また、低密度ポリエチレンのメルトフローレイトは５ｇ／１０分以上であることが好ましく、１０ｇ／１０分以上であることがより好ましく、１５ｇ／１０分以上であることがさらに好ましい。前記メルトフローレイトは、ＪＩＳ　Ｋ７２１０－１：２０１４に従って、温度１９０℃、荷重２．１６ｋｇにて測定される値である。 Further, the melt flow rate of the low density polyethylene is preferably 5 g / 10 minutes or more, more preferably 10 g / 10 minutes or more, and further preferably 15 g / 10 minutes or more. The melt flow rate is a value measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210-1: 2014.
　なお、低密度ポリエチレンが２種以上の混合物である場合、その混合物の融点及びメルトフローレイトは、押出機で予め溶融混練したものについて測定される融点及びメルトフローレイトにて特定される。 When the low density polyethylene is a mixture of two or more kinds, the melting point and melt flow rate of the mixture are specified by the melting point and melt flow rate measured with respect to those previously melt-kneaded with an extruder.
　本発明で好ましく使用される低密度ポリエチレンの市販品としては、たとえば、ＮＵＣ社製の「製品名ＮＵＣ８３２１」（メルトフローレイト１．９ｇ／１０分、融点１１２℃）などが挙げられる。 Examples of commercially available products of low density polyethylene preferably used in the present invention include “Product name NUC8321” (melt flow rate 1.9 g / 10 min, melting point 112 ° C.) manufactured by NUC.
　上記低密度ポリエチレンには、本発明の目的及び効果を阻害しない範囲において、他のポリエチレン系樹脂やポリプロピレン系樹脂、ポリスチレン系樹脂等の熱可塑性樹脂や、エチレンプロピレンゴム、スチレン－ブタジエン－スチレンブロック共重合体等のエラストマーなどを含んでもよい。 The low-density polyethylene includes other polyethylene resins, polypropylene resins, polystyrene resins, and other thermoplastic resins, ethylene propylene rubber, styrene-butadiene-styrene block copolymer, as long as the objects and effects of the present invention are not impaired. An elastomer such as a polymer may be included.
　前記他のポリエチレン系樹脂としては、エチレン成分単位が５０モル％以上の樹脂であり、具体的には、高密度ポリエチレン、直鎖状低密度ポリエチレン、超低密度ポリエチレン、エチレン－酢酸ビニル共重合体、エチレン－メタクリル酸メチル共重合体、エチレン－アクリル酸エチル共重合体等や、さらにそれらの２種以上の混合物が挙げられる。 The other polyethylene-based resin is a resin having an ethylene component unit of 50 mol% or more, and specifically includes high-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, and ethylene-vinyl acetate copolymer. Ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, and the like, and a mixture of two or more thereof.
　低密度ポリエチレン以外の樹脂やエラストマーの配合量は低密度ポリエチレン１００質量部に対して２０質量部以下が好ましく、１０質量部以下がより好ましく、５質量部以下が特に好ましい。低密度ポリエチレンと共に、前記低密度ポリエチレン以外の樹脂やエラストマーを混練して発泡性溶融樹脂組成物を構成する基材樹脂とすることができる。 The amount of resin and elastomer other than low-density polyethylene is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of low-density polyethylene. A resin other than the low-density polyethylene and an elastomer can be kneaded together with the low-density polyethylene to form a base resin constituting the foamable molten resin composition.
（帯電防止剤）
　本発明の製造方法においては、帯電防止剤として、高分子型帯電防止剤を用いることが必要である。この高分子型帯電防止剤は、上記低密度ポリエチレンとの融点差が－１０℃～＋１０℃の範囲内であり、かつメルトフローレイトが１０ｇ／１０分以上のものである。 (Antistatic agent)
In the production method of the present invention, it is necessary to use a polymer type antistatic agent as the antistatic agent. This polymer type antistatic agent has a melting point difference from the low density polyethylene in the range of −10 ° C. to + 10 ° C. and a melt flow rate of 10 g / 10 min or more.
　このような高分子型帯電防止剤を用いると中長期に亘る連続生産においても小孔や貫通孔等の発生が防止・抑制された高品質で優れた帯電防止機能を発現するポリエチレン系樹脂押出発泡シートを得ることができる。 Using such a polymer type antistatic agent, polyethylene-based resin extrusion foam that exhibits high-quality and excellent antistatic function, which prevents and suppresses the generation of small holes and through-holes even in continuous production over the medium to long term A sheet can be obtained.
　この正確な理由は現時点では定かではないが、後述するように、本発明で用いる高分子型帯電防止剤は融点が低くメルトフローレイトが高いため、従来の融点の高い高分子型帯電防止剤のように環状ダイ内での小孔や貫通孔の発生原因となる結晶の析出が防止・抑制されることによるものと考えている。 Although the exact reason is not clear at present, as will be described later, the polymer antistatic agent used in the present invention has a low melting point and a high melt flow rate. In this way, it is considered that the precipitation of crystals that cause the generation of small holes and through holes in the annular die is prevented and suppressed.
　本発明で用いる高分子型帯電防止剤の融点と、上記低密度ポリエチレンの融点との差（［低密度ポリエチレンの融点］－［高分子型帯電防止剤の融点］）が－１０℃～＋１０℃の範囲内であるが、更なる連続運転においても高品質のものを得る観点から、前記融点差は好ましくは－８℃～＋８℃であり、さらに好ましくは－７℃～＋７℃である。また、高分子型帯電防止剤の融点は１２５℃以下であることが好ましく、１２０℃以下であることがより好ましい。一方、融点の下限は概ね１００℃程度である。
　なお、高分子型帯電防止剤の融点は、前記低密度ポリエチレンと同様の方法によって求められる。 The difference between the melting point of the polymer antistatic agent used in the present invention and the melting point of the low density polyethylene ([melting point of low density polyethylene] − [melting point of polymer antistatic agent]) is −10 ° C. to + 10 ° C. However, the melting point difference is preferably −8 ° C. to + 8 ° C., more preferably −7 ° C. to + 7 ° C., from the viewpoint of obtaining a high-quality product in further continuous operation. The melting point of the polymer antistatic agent is preferably 125 ° C. or lower, and more preferably 120 ° C. or lower. On the other hand, the lower limit of the melting point is about 100 ° C.
The melting point of the polymer antistatic agent is determined by the same method as that for the low density polyethylene.
　同様な理由により、本発明で用いる高分子型帯電防止剤のメルトフローレイトが１０ｇ／１０分以上であるが、好ましくは２０ｇ／１０分以上であり、さらに好ましくは３０ｇ／１０分以上である。一方、その上限は概ね１００ｇ／１０分程度である上記範囲であれば、帯電防止剤が流動性に優れ、より効果的に帯電防止性能を発揮することから好ましい。なお、高分子型帯電防止剤のメルトフローレイトはＪＩＳ　Ｋ７２１０－１：２０１４に従って、温度１９０℃、荷重２．１６ｋｇにて測定される値である。 For the same reason, the melt flow rate of the polymer antistatic agent used in the present invention is 10 g / 10 min or more, preferably 20 g / 10 min or more, and more preferably 30 g / 10 min or more. On the other hand, an upper limit of about 100 g / 10 minutes is preferable because the antistatic agent has excellent fluidity and exhibits antistatic performance more effectively. The melt flow rate of the polymer antistatic agent is a value measured at a temperature of 190 ° C. and a load of 2.16 kg according to JIS K7210-1: 2014.
　また、高分子型帯電防止剤のメルトフローレイトに対する低密度ポリエチレンＢのメルトフローレイトの比（低密度ポリエチレンのメルトフローレイト／高分子型帯電防止剤のメルトフローレイト）は２以下であることが好ましく、１以下であることがより好ましく、０．８以下であることがさらに好ましい。該比が上記範囲であると、高分子型帯電防止剤が網状または層状に分散し、優れた帯電防止性能をより効果的に発揮することができる。一方、該比の下限は概ね０．０１以上であることが好ましい。 In addition, the ratio of the melt flow rate of the low density polyethylene B to the melt flow rate of the polymer type antistatic agent (melt flow rate of low density polyethylene / melt flow rate of the polymer type antistatic agent) may be 2 or less. Preferably, it is 1 or less, more preferably 0.8 or less. When the ratio is in the above range, the polymer type antistatic agent is dispersed in a network or a layer, and excellent antistatic performance can be exhibited more effectively. On the other hand, the lower limit of the ratio is preferably about 0.01 or more.
　本発明で好ましく使用される高分子型帯電防止剤としては、ポリエーテルとポリオレフィンのブロック共重合体からなるものであり、市販品としては、たとえば三洋化成工業株式会社製のペレクトロンＬＭＰ（融点１１４℃、メルトフローレイト３０ｇ／１０分）などを挙げることができる。 The polymer type antistatic agent preferably used in the present invention comprises a block copolymer of polyether and polyolefin, and commercially available products include, for example, PELECTRON LMP (melting point: 114 ° C., manufactured by Sanyo Chemical Industries, Ltd.). , Melt flow rate 30 g / 10 min).
　本発明において使用される高分子型帯電防止剤の数平均分子量としては、２０００以上が好ましく、より好ましくは２０００～１０００００、更に好ましくは５０００～８００００である。尚、該高分子型帯電防止剤の数平均分子量の上限は概ね５０００００である。高分子型帯電防止剤の数平均分子量を上記の範囲とすることにより、帯電防止性能が湿度等の環境に左右されずより安定的に発現される。 The number average molecular weight of the polymer type antistatic agent used in the present invention is preferably 2000 or more, more preferably 2000 to 100,000, still more preferably 5000 to 80,000. The upper limit of the number average molecular weight of the polymer type antistatic agent is approximately 500,000. By setting the number average molecular weight of the polymer type antistatic agent within the above range, the antistatic performance is more stably expressed regardless of the environment such as humidity.
　上記の数平均分子量は、高温ゲルパーミエーションクロマトグラフィーを用いて求められる。例えば、高分子型帯電防止剤がポリエーテルエステルアミドやポリエーテルを主成分とするものの場合にはオルトジクロロベンゼンを溶媒として試料濃度３ｍｇ／ｍｌとし、ポリスチレンを基準物質としてカラム温度１３５℃の条件にて測定される値である。なお、上記溶媒の種類、カラム温度は、高分子型帯電防止剤の種類に応じて適宜変更する。 The above number average molecular weight is determined using high temperature gel permeation chromatography. For example, when the polymer type antistatic agent is composed mainly of polyetheresteramide or polyether, the sample concentration is 3 mg / ml using orthodichlorobenzene as a solvent, and the column temperature is set to 135 ° C. using polystyrene as a reference substance. Is a measured value. In addition, the kind of said solvent and column temperature are suitably changed according to the kind of polymeric antistatic agent.
（帯電防止剤の配合量）
　高分子型帯電防止剤の発泡体への配合量は、十分な帯電防止特性を有し、かつ高品質の発泡シートを得る上で、該発泡体を構成する低密度ポリエチレン１００質量部に対して２～３０質量部であることが好ましく、より好ましくは３～２５質量部、更に好ましくは５～２０質量部である。 (Amount of antistatic agent)
The blending amount of the polymer type antistatic agent in the foam is sufficient with respect to 100 parts by mass of the low density polyethylene constituting the foam in order to obtain a foam sheet having sufficient antistatic properties and high quality. The amount is preferably 2 to 30 parts by mass, more preferably 3 to 25 parts by mass, and still more preferably 5 to 20 parts by mass.
（発泡シートの表面抵抗率）
　本発明方法においては、上記高分子型帯電防止剤を添加することにより、発泡シートの表面の表面抵抗率を、１×１０７～１×１０１３Ωにすることができる。該表面抵抗率が上記範囲内であれば、発泡シートは十分な帯電防止特性を示すものとなる。前記観点からは、該表面抵抗率は、５×１０１２Ω以下が好ましく、１×１０１２Ω以下がさらに好ましい。 (Surface resistivity of foam sheet)
In the method of the present invention, the surface resistivity of the surface of the foamed sheet can be set to 1 × 10 7 to 1 × 10 13 Ω by adding the polymer type antistatic agent. If the surface resistivity is within the above range, the foam sheet exhibits sufficient antistatic properties. From the above viewpoint, the surface resistivity is preferably 5 × 10 12 Ω or less, and more preferably 1 × 10 12 Ω or less.
　本発明における表面抵抗率は、下記の試験片の状態調節を行った後、ＪＩＳ　Ｋ６２７１：２００８に準拠して測定される。具体的には、測定対象物である発泡シートから切り出した試験片（縦１００ｍｍ×横１００ｍｍ×厚み：測定対象物厚み）を温度２０℃、相対湿度３０％の雰囲気下に３６時間放置することにより試験片の状態調節を行う。次いで、温度２０℃、相対湿度３０％の雰囲気下において印加電圧５００Ｖの条件にて、試験片に電圧を印加する。電圧印加を開始して１分経過後の表面抵抗率を測定する。 The surface resistivity in the present invention is measured according to JIS K6271: 2008 after adjusting the state of the following test piece. Specifically, by leaving a test piece (length 100 mm × width 100 mm × thickness: thickness of measurement object) cut out from a foam sheet as a measurement object for 36 hours in an atmosphere at a temperature of 20 ° C. and a relative humidity of 30%. Condition the specimen. Next, a voltage is applied to the test piece under the condition of an applied voltage of 500 V in an atmosphere of a temperature of 20 ° C. and a relative humidity of 30%. The surface resistivity after 1 minute from the start of voltage application is measured.
（物理発泡剤）
　本発明方法においては、低密度ポリエチレンを押出機に供給して、加熱、混練して溶融樹脂とし、次いで物理発泡剤を圧入してさらに混練することにより発泡性溶融樹脂組成物を形成する。物理発泡剤は有機系又は無機系物理発泡剤であって良い。有機系物理発泡剤としては、例えば、プロパン、ノルマルブタン、イソブタン、ノルマルペンタン、イソペンタン、ノルマルヘキサン、イソヘキサン等の脂肪族炭化水素、シクロペンタン、シクロヘキサンなどの脂環式炭化水素、塩化メチル、塩化エチル等の塩化炭化水素、１，１，１，２－テトラフロロエタン、１，１－ジフロロエタン等のフッ化炭化水素、ジメチルエーテル、メチルエチルエーテル等のエーテル類、メタノール、エタノール等のアルコール類が挙げられる。 (Physical foaming agent)
In the method of the present invention, low density polyethylene is supplied to an extruder, heated and kneaded to obtain a molten resin, and then a physical foaming agent is injected and further kneaded to form a foamable molten resin composition. The physical foaming agent may be an organic or inorganic physical foaming agent. Examples of the organic physical foaming agent include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, normal hexane, and isohexane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, methyl chloride, and ethyl chloride. And chlorohydrocarbons such as 1,1,1,2-tetrafluoroethane, fluorinated hydrocarbons such as 1,1-difluoroethane, ethers such as dimethyl ether and methyl ethyl ether, and alcohols such as methanol and ethanol. .
　無機系物理発泡剤としては、例えば、酸素、窒素、二酸化炭素、空気、水が挙げられる。これらの物理発泡剤は、２種以上を混合して使用することが可能である。これらのうち、発泡性の観点から有機系物理発泡剤が好ましく、中でもノルマルブタン、イソブタン、又はこれらの混合物を主成分とするものが特に好適である。 Examples of the inorganic physical foaming agent include oxygen, nitrogen, carbon dioxide, air, and water. These physical foaming agents can be used in combination of two or more. Among these, an organic physical foaming agent is preferable from the viewpoint of foaming properties, and among them, those mainly composed of normal butane, isobutane, or a mixture thereof are particularly preferable.
　該物理発泡剤の添加量は、その種類、目的とする発泡シートの見掛け密度に応じて調整する。例えば、物理発泡剤としてイソブタン３０質量％とノルマルブタン７０質量％とのブタン混合物などの物理発泡剤を用いて見掛け密度２０～４５０ｋｇ／ｍ３の発泡シートを得る場合、発泡性溶融樹脂組成物を構成する基材樹脂１００質量部に対して４～３５質量部、好ましくは５～３０質量部、より好ましくは６～２５質量部である。 The addition amount of the physical foaming agent is adjusted according to the type and the apparent density of the target foam sheet. For example, when a foamed sheet having an apparent density of 20 to 450 kg / m 3 is obtained using a physical foaming agent such as a butane mixture of 30% by mass of isobutane and 70% by mass of normal butane as the physical foaming agent, The amount is 4 to 35 parts by mass, preferably 5 to 30 parts by mass, and more preferably 6 to 25 parts by mass with respect to 100 parts by mass of the base resin.
（気泡調整剤）
　本発明方法においては、前記低密度ポリエチレンと共に気泡調整剤を押出機に供給することができる。気泡調整剤としては、無機粉体や化学発泡剤を用いることができる。該無機粉体としては、タルク、ゼオライト、シリカ、炭酸カルシウムなどが例示される。 (Bubble conditioner)
In the method of the present invention, the air conditioner can be supplied to the extruder together with the low density polyethylene. An inorganic powder or a chemical foaming agent can be used as the bubble regulator. Examples of the inorganic powder include talc, zeolite, silica, calcium carbonate and the like.
　該化学発泡剤としては、アゾジカルボンアミド、ヒドラゾジカルボンアミド、アゾビスイソブチロニトリル、炭酸水素ナトリウム（重曹）や、炭酸水素ナトリウムとクエン酸又はクエン酸一ナトリウム等のクエン酸モノアルカリ金属塩との混合物である重曹－クエン酸系化学発泡剤などが例示される。前記化学発泡剤の中でも、気泡径が小さく、緩衝性に優れる発泡シートを得るためには、重曹－クエン酸系化学発泡剤が好ましい。 Examples of the chemical foaming agent include azodicarbonamide, hydrazodicarbonamide, azobisisobutyronitrile, sodium hydrogen carbonate (sodium bicarbonate), and citric acid monoalkali metal salts such as sodium hydrogen carbonate and citric acid or monosodium citrate. And sodium bicarbonate-citric acid based chemical foaming agent. Among the chemical foaming agents, a sodium bicarbonate-citric acid based chemical foaming agent is preferable in order to obtain a foamed sheet having a small cell diameter and excellent buffering properties.
　特に、平均粒子径３～８μｍの重曹－クエン酸系化学発泡剤を使用すると、発泡シートを貫く貫通孔の発生をより効果的に防止することができることから好ましい。かかる観点から、該平均粒子径は４～７μｍであることがより好ましい。また、化学発泡剤の最大粒子径は１００μｍ以下であることが好ましく、８０μｍ以下であることがより好ましい。上記の平均粒子径とは、レーザー回折散乱式粒度分布測定にて測定されるメジアン径（ｄ５０）を意味する。また、上記化学発泡剤の最大粒子径は、化学発泡剤から無作為にサンプリングした約１～３ｍｇ程度の粒子群を光学顕微鏡等で拡大観察し、粒子群の中で最も長軸径の長い粒子の長軸径を化学発泡剤の最大粒子径とする。 In particular, it is preferable to use a baking soda-citric acid based chemical foaming agent having an average particle diameter of 3 to 8 μm because it is possible to more effectively prevent the generation of through-holes penetrating the foamed sheet. From this viewpoint, the average particle size is more preferably 4 to 7 μm. Further, the maximum particle size of the chemical foaming agent is preferably 100 μm or less, and more preferably 80 μm or less. The average particle diameter means a median diameter (d50) measured by laser diffraction / scattering particle size distribution measurement. The maximum particle size of the above chemical foaming agent is about 1 to 3 mg of particles randomly sampled from the chemical foaming agent. Is the maximum particle diameter of the chemical foaming agent.
　前記気泡調整剤の添加量は、発泡性溶融樹脂組成物を構成する基材樹脂１００質量部に対して０．１～３質量部であることが好ましく、より好ましくは０．２～２質量部である。該添加量が上記範囲であると、気泡径を所望の範囲に調整しやすいことから好ましい。 The addition amount of the cell regulator is preferably 0.1 to 3 parts by mass, more preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the base resin constituting the foamable molten resin composition. It is. It is preferable for the amount added to be in the above range because the bubble diameter can be easily adjusted to a desired range.
　（その他の添加剤）
　本発明方法においては、上記成分の他、本発明の効果を損なわない範囲で、各種添加剤を添加することができる。添加剤としては、例えば、酸化防止剤、熱安定剤、耐候剤、紫外線吸収剤、難燃剤、無機充填剤、抗菌剤、着色剤等が挙げられる。 (Other additives)
In the method of the present invention, in addition to the above components, various additives can be added as long as the effects of the present invention are not impaired. Examples of the additive include an antioxidant, a heat stabilizer, a weathering agent, an ultraviolet absorber, a flame retardant, an inorganic filler, an antibacterial agent, and a colorant.
　本発明の製造方法において、中長期連続生産においても小孔や貫通孔の発生が防止・抑制され、かつ帯電防止性能も十分に発現する発泡シートが得られる理由は現時点では定かではないが、つぎのように推測している。 In the production method of the present invention, the reason why a foamed sheet that prevents or suppresses the generation of small holes and through-holes and exhibits sufficient antistatic performance even in medium- to long-term continuous production is not clear at this time. I guess that.
　従来この種の帯電防止剤を含有するポリエチレン系樹脂押出発泡シートにおいては、帯電防止剤としては後記比較例に見られるように、基材樹脂である低密度ポリエチレンとの融点差が＋２０℃以上である融点１３５℃程度の高分子型帯電防止剤が用いられている。このような従来の高分子型帯電防止剤を用いた場合、上記したように押出機内の温度は２００℃以程度の高温に保持されているので、該高分子型帯電防止剤は発泡性溶融樹脂組成
物中に完全に溶融し、未溶融の高分子型帯電防止剤の結晶は析出しない。 Conventionally, in the polyethylene-based resin extruded foam sheet containing this type of antistatic agent, as seen in the comparative example described later, the antistatic agent has a melting point difference of + 20 ° C. or more with the low-density polyethylene as the base resin. A polymer antistatic agent having a melting point of about 135 ° C. is used. When such a conventional polymer type antistatic agent is used, since the temperature in the extruder is maintained at a high temperature of about 200 ° C. or more as described above, the polymer type antistatic agent is a foamable molten resin. The polymer melts completely in the composition, and the unmelted polymer antistatic crystal does not precipitate.
　しかしながら、この発泡性溶融樹脂組成物は上記したように環状ダイに導入され際、発泡適正温度となるように冷却され、具体的には１２０℃程度（低密度ポリエチレン系樹脂の融点＋１０℃以下程度）に冷却される。従来の高分子型帯電防止剤は１３５℃程度であるから、このような冷却温度下においては押出機内で溶融していた高分子型帯電防止剤の一部が結晶化して析出してしまうものと考えられる。 However, when the foamable molten resin composition is introduced into the annular die as described above, it is cooled to an appropriate foaming temperature, specifically about 120 ° C. (melting point of low-density polyethylene resin + about 10 ° C. or less) ). Since the conventional polymer antistatic agent is about 135 ° C., a part of the polymer antistatic agent melted in the extruder crystallizes and precipitates at such a cooling temperature. Conceivable.
　そして、この析出結晶を含む発泡性溶融樹脂組成物を環状ダイ内で押出すと、析出結晶が環状ダイ内の壁面に滞留付着し始める。初期の段階（数時間）ではこの残留結晶の滞留付着量は少ないので、発泡体の表面に対する影響は小さいものの、たとえば２日間の連続生産更には７日間といった長期に亘る連続生産の場合には該残留結晶の滞留量や付着量が飛躍的に増大し、ついには発泡体の表面に接触、落下し、発泡シートに小孔や貫通孔が発生し高品質の発泡シートを得ることができない。 Then, when the foamable molten resin composition containing the precipitated crystal is extruded in the annular die, the precipitated crystal starts to stay and adhere to the wall surface in the annular die. In the initial stage (several hours), the amount of residual crystals remaining is small, so the influence on the surface of the foam is small, but in the case of continuous production over a long period of time such as 2 days or 7 days, The amount of residual crystals and the amount of adhered crystals increase drastically, and finally comes into contact with and falls on the surface of the foam, generating small holes and through holes in the foamed sheet, making it impossible to obtain a high-quality foamed sheet.
　これに対して、本発明においては、帯電防止剤として、低密度ポリエチレン系樹脂との融点差が－１０℃～＋１０℃の範囲内の融点を有し、メルトフローレイトが１０ｇ／１０分以上の高分子型帯電防止剤を用いたことから、押出機においては従来の高分子型帯電防止剤と同様に発泡性溶融樹脂組成物中に完全に溶融し、未溶融の高分子型帯電防止剤の結晶は析出しない。 On the other hand, in the present invention, the antistatic agent has a melting point difference within the range of −10 ° C. to + 10 ° C. with respect to the low density polyethylene resin, and the melt flow rate is 10 g / 10 min or more. Since the polymer type antistatic agent is used, the extruder is completely melted in the foamable molten resin composition in the same manner as the conventional polymer type antistatic agent, and an unmelted polymer type antistatic agent is used. Crystals do not precipitate.
　また、この発泡性溶融樹脂組成物は上記したように発泡適正温度になるように冷却され、具体的には低密度ポリエチレン系樹脂の融点＋１０℃程度たとえば１２０℃に冷却される。ここで、本発明で用いる高分子型帯電防止剤は低密度ポリエチレンとの融点差が－１０℃～＋１０℃の範囲内の融点を有するものであるから、このような冷却温度下においては押出機内と同様に環状ダイ内においても完全に溶融し、未溶融の高分子型帯電防止剤の結晶化が防止・抑制されるものと考えられる。 In addition, the foamable molten resin composition is cooled to an appropriate foaming temperature as described above, and specifically, the melting point of the low-density polyethylene resin is about + 10 ° C., for example, 120 ° C. Here, since the polymer type antistatic agent used in the present invention has a melting point difference within the range of −10 ° C. to + 10 ° C. with respect to the low density polyethylene, In the same manner as in the above, it is considered that the polymer melts completely in the annular die and the crystallization of the unmelted polymer antistatic agent is prevented / suppressed.
　したがって、本発明においては、従来の高分子型帯電防止剤を用いた場合とは異なり、厚みが薄いにもかかわらず、数時間の短期間はもちろんのこと、数日間の中長期間に亘っての連続生産においても、高分子型帯電防止剤に起因すると考えられる小孔や貫通孔の発生が防止・抑制された高品質で優れた強度と緩衝性を併せ持ち、かつ帯電防止性能も十分に発現する発泡シートを得ることができる。 Therefore, in the present invention, unlike the case of using a conventional polymer type antistatic agent, although it is thin, not only a short period of several hours but also a medium to long period of several days. Even in continuous production, high-quality, excellent strength and buffering properties that prevent and suppress the generation of small holes and through-holes that are thought to be due to polymer-type antistatic agents are combined, and antistatic performance is fully developed. A foam sheet can be obtained.
　上記したように、本発明の発泡シートの製造方法は、数時間といった短期間はもちろんのこと、数日間の中長期間においても小孔や貫通孔の発生が防止・抑制されたものであるため連続生産性に優れたものとなる。したがって、本発明の発泡シートの製造においては、厚み、幅方向長さによっても異なるが、製造時に１００ｍ以上、好ましくは３００ｍ以上の長さのロール状として発泡シートを巻き取ることができる。 As described above, the method for producing a foamed sheet of the present invention prevents and suppresses the generation of small holes and through holes not only in a short period of several hours but also in the medium and long periods of several days. Excellent continuous productivity. Accordingly, in the production of the foamed sheet of the present invention, the foamed sheet can be wound up as a roll having a length of 100 m or more, preferably 300 m or more during production, although it varies depending on the thickness and the length in the width direction.
　これに対して、従来の製造方法においては、数日間という中長期間に亘る連続製造を行なった際に発泡シートに小孔や貫通孔の欠陥が発生するおそれがあり、その場合、一度発泡シートをロールから切り離し、欠陥部分を取り除いた後に、再度発泡シートをロール状に巻き取る作業が必要となるため生産効率が著しく低下してしまう。 On the other hand, in the conventional manufacturing method, there is a possibility that defects in small holes and through holes may occur in the foam sheet when continuous production is performed over a medium to long period of several days. After removing the defect from the roll and removing the defective part, it is necessary to take up the foamed sheet again in a roll shape, so that the production efficiency is remarkably lowered.
　上記観点から、本発明においては、ポリエチレン系樹脂押出発泡シートに存在する径１ｍｍ以上の貫通孔の数が少ないほど好ましい。具体的には、製造開始から２日、７日経過後、１時間に発生する１ｍｍ以上の貫通孔の数が３個未満であることが好ましい。 From the above viewpoint, in the present invention, it is preferable that the number of through-holes having a diameter of 1 mm or more present in the polyethylene resin extruded foam sheet is smaller. Specifically, it is preferable that the number of through-holes of 1 mm or more generated in 1 hour after the lapse of 2 days and 7 days from the start of production is less than 3.
（発泡シートの厚み）
　本発明の製造方法で得られる発泡シートの厚み（平均厚み）は、０．０５ｍｍ以上０．５ｍｍ以下である。間紙としての緩衝性と使用可能性の観点から、平均厚みの下限は好ましくは０．０７ｍｍ、より好ましくは０．１ｍｍ、更に好ましくは０．１５ｍｍである。一方、平均厚みの上限は、好ましくは０．４ｍｍ、より好ましくは０．３５ｍｍ、更に好ましくは０．３ｍｍである。 (Thickness of foam sheet)
The thickness (average thickness) of the foamed sheet obtained by the production method of the present invention is 0.05 mm or more and 0.5 mm or less. From the viewpoints of buffering properties and usability as a slip sheet, the lower limit of the average thickness is preferably 0.07 mm, more preferably 0.1 mm, and still more preferably 0.15 mm. On the other hand, the upper limit of the average thickness is preferably 0.4 mm, more preferably 0.35 mm, and still more preferably 0.3 mm.
　発泡シートの平均厚みは、株式会社山文電気製オフライン厚み測定機ＴＯＦ－４Ｒなどを使用し測定することができる。まず発泡シートの全幅について、１ｃｍ間隔で厚みの測定を行う。この１ｃｍ間隔で測定される発泡シートの厚みを基に、全幅の算術平均厚みを求める。尚、上記の測定に使用する発泡シートは、温度２３±５℃、相対湿度５０％の条件下で２４時間以上状態調整したものを用いる。 The average thickness of the foam sheet can be measured using an offline thickness measuring machine TOF-4R manufactured by Yamabun Electric Co., Ltd. First, the thickness of the entire width of the foam sheet is measured at intervals of 1 cm. Based on the thickness of the foam sheet measured at intervals of 1 cm, the arithmetic average thickness of the full width is obtained. In addition, the foam sheet used for said measurement uses what adjusted the state for 24 hours or more on conditions of temperature 23 +/- 5 degreeC and relative humidity 50%.
（発泡シートの見掛け密度）
　本発明の製造方法で得られる発泡シートの見掛け密度は、好ましくは２０～４５０ｋｇ／ｍ３の範囲内ある。該見掛け密度が上記範囲であると、間紙等の包装材として緩衝性に優れたものとなることから好ましい。かかる観点から、該見掛け密度は３０～３００ｋｇ／ｍ３がより好ましく、さらに好ましくは５０～２００ｋｇ／ｍ３である。
　なお、発泡シートの見掛け密度は、発泡シートの単位面積当たりの重量（ｇ／ｍ２）を発泡シートの平均厚みで割算し、さらに［ｋｇ／ｍ３］に単位換算することにより求めることができる。 (Apparent density of foam sheet)
The apparent density of the foam sheet obtained by the production method of the present invention is preferably in the range of 20 to 450 kg / m 3 . When the apparent density is in the above range, it is preferable because the cushioning property is excellent as a packaging material such as a slip sheet. From this viewpoint, the apparent density is more preferably 30 to 300 kg / m 3 , and further preferably 50 to 200 kg / m 3 .
Incidentally, the apparent density of the foam sheet, be determined by the weight per unit area of the foam sheet (g / m 2) divided by the average thickness of the foamed sheet and unit conversion more [kg / m 3] it can.
　また、環状ダイの吐出口径とマンドレルの直径との比（ブローアップ比：マンドレルの直径／環状ダイのリップ部直径）は、２．２～３．８にすることが好ましい。上記範囲であると、発泡に伴う円周方向への波打ち現象がなく厚み精度に優れ、かつ気泡が幅方向への過度な扁平化がなく良好な発泡シートが得られることから好ましい。 The ratio of the discharge diameter of the annular die to the diameter of the mandrel (blow-up ratio: diameter of the mandrel / lip portion diameter of the annular die) is preferably 2.2 to 3.8. The above range is preferable because there is no waviness phenomenon in the circumferential direction due to foaming, excellent thickness accuracy, and excellent foamed sheets without excessive flattening of bubbles in the width direction.
（発泡シート）
　本発明に係る新規なポリエチレン系樹脂押出発泡シートは、前記したように、厚みが極めて薄いにもかかわらず、小孔や貫通孔の発生が防止・抑制された高品質なものであり、しかも十分な帯電防止性能を発現する。 (Foam sheet)
As described above, the novel polyethylene-based resin extruded foam sheet according to the present invention is a high-quality one that prevents and suppresses the generation of small holes and through-holes despite its extremely small thickness, and is sufficient. Expresses antistatic performance.
　したがって、本発明の新規なポリエチレン系樹脂押出発泡シートは、帯電防止機能等が強く要求される分野、殊に液晶ディスプレイ、プラズマディスプレイ、エレクトロルミネッセンスディスプレイ等の画像表示機器用の薄型ガラス板の搬送や梱包時の損傷を防止するためのガラス板用間紙として広く極めて有用なものである。また、中長期に亘って連続的に製造することが可能であり、工業的に極めて生産効率の高い発泡シートである。 Therefore, the novel polyethylene-based resin extruded foam sheet of the present invention is used in fields where an antistatic function or the like is strongly required, in particular, for transporting thin glass plates for image display devices such as liquid crystal displays, plasma displays, and electroluminescence displays. It is widely and extremely useful as a glass sheet slip for preventing damage during packaging. In addition, it is a foam sheet that can be produced continuously over the medium to long term and is industrially extremely high in production efficiency.
　以下、実施例および比較例にて本発明を更に詳細に説明する。但し、本発明は実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.
［低密度ポリエチレン］
　実施例及び比較例で用いた低密度ポリエチレンを表１に示す。 [Low density polyethylene]
Table 1 shows the low-density polyethylene used in the examples and comparative examples.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　実施例及び比較例で用いた帯電防止剤を表２に示す。 Table 2 shows antistatic agents used in Examples and Comparative Examples.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　［気泡調整剤］
　実施例及び比較例で用いた気泡調整剤は、炭酸水素ナトリウムとクエン酸一ナトリウムとの重量比１：１の混合物であり、平均粒子径（ｄ５０）６μｍ、最大粒子径３０μｍの化学発泡剤を用いた。 [Bubble conditioner]
The air conditioner used in Examples and Comparative Examples is a mixture of sodium bicarbonate and monosodium citrate in a weight ratio of 1: 1, and a chemical foaming agent having an average particle diameter (d50) of 6 μm and a maximum particle diameter of 30 μm. Using.
　［装置］
　発泡シート製造装置として、発泡層形成用のバレル内径１１５ｍｍの押出機とその下流側にバレル内径１５０ｍｍの押出機が連結された第１押出機（タンデム押出機）を用いた。なお、ダイのリップ部金型の温調は、リップ部金型を８分割して分割された部分ごとに行なった。 [apparatus]
As the foam sheet production apparatus, an extruder having a barrel inner diameter of 115 mm for forming a foam layer and a first extruder (tandem extruder) in which an extruder having a barrel inner diameter of 150 mm was connected to the downstream side thereof were used. The temperature control of the die lip part mold was performed for each of the divided parts obtained by dividing the lip part mold into eight parts.
実施例１～３、比較例１～５
　表３に示す低密度ポリエチレン系樹脂、帯電防止剤及び気泡調整剤とを、表３に示す配合で押出機の原料投入口に供給し、加熱混練して、２００℃に調整された樹脂溶融物とした。該樹脂溶融物に物理発泡剤としてノルマルブタン７０質量％とイソブタン３０質量％の混合ブタンを、ポリエチレン系樹脂１００質量部に対して、表３に示す配合量となるように圧入して加熱混練し、次いで冷却して表３に示す樹脂温度の発泡性溶融樹脂組成物とし、該発泡性溶融樹脂組成物を押出用環状ダイに導入した。 Examples 1 to 3, Comparative Examples 1 to 5
Resin melt adjusted to 200 ° C. by supplying the low-density polyethylene resin, antistatic agent and bubble regulator shown in Table 3 to the raw material inlet of the extruder with the formulation shown in Table 3, and kneading by heating. It was. A mixed butane of 70% by weight of normal butane and 30% by weight of isobutane as a physical foaming agent is pressed into the resin melt so as to have a blending amount shown in Table 3 with respect to 100 parts by weight of the polyethylene-based resin, followed by heat-kneading. Then, the mixture was cooled to obtain a foamable molten resin composition having a resin temperature shown in Table 3, and the foamable molten resin composition was introduced into an annular die for extrusion.
　ついで、ダイのリップを通して大気中に押出し、帯電防止剤を含有する単層構成の筒状発泡体を形成した。該筒状発泡体をマンドレルにて表３に示すブローアップ比で拡径しながら、表３に示す速度で引き取り、さらに押出方向に沿って切り開いて、所定長さのロール体に巻き取り、帯電防止剤を含有する単層の発泡シートを得た。 Then, it was extruded into the atmosphere through a lip of a die to form a cylindrical foam having a single layer structure containing an antistatic agent. While expanding the cylindrical foam with a mandrel at the blow-up ratio shown in Table 3, it is taken up at the speed shown in Table 3, further cut along the extrusion direction, wound around a roll body of a predetermined length, and charged. A single-layer foamed sheet containing an inhibitor was obtained.
　なお、表３における帯電防止剤、気泡調整剤及び物理発泡剤の配合量は、発泡層を構成する樹脂１００質量部に対する帯電防止剤、気泡調整剤及び物理発泡剤の質量部を表す。 In addition, the compounding quantity of the antistatic agent in Table 3, a bubble regulator, and a physical foaming agent represents the mass part of the antistatic agent, a bubble regulator, and a physical foaming agent with respect to 100 mass parts of resin which comprises a foamed layer.
　実施例、比較例で得られた発泡シートの物性を表４に示す。 Table 4 shows the physical properties of the foam sheets obtained in Examples and Comparative Examples.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
（表４の検討結果）
　表４から、実施例１～３で得られる発泡シートは、低密度ポリエチレンとの融点差が＋７℃である特有な高分子型帯電防止剤（帯防１：融点１１４℃）を用いたことから、４８時間（２日間）という中期連続生産においてはもとより１６８時間（７日間）という長期の連続生産においてもその表面に貫通孔の発生が防止・抑制されたものであり、加えて帯電防止性能が十分発現するものである。したがって本発明の発泡シートは、帯電防止性能を有し、かつ安定的かつ大量に生産できる工業的に極めて価値のある発泡シートであることが分かる。 (Results of examination in Table 4)
From Table 4, the foamed sheets obtained in Examples 1 to 3 used a specific polymer type antistatic agent (protection 1: melting point 114 ° C.) having a melting point difference of + 7 ° C. from low density polyethylene. In addition, in the medium-term continuous production of 48 hours (2 days), the generation of through-holes on the surface is prevented and suppressed not only in the long-term continuous production of 168 hours (7 days), and in addition, the antistatic performance is improved. It is fully expressed. Therefore, it can be seen that the foamed sheet of the present invention is an industrially extremely valuable foamed sheet that has antistatic performance and can be produced stably and in large quantities.
　これに対して、比較例１～２で得られる発泡シートは低密度ポリエチレンとの融点差が２８℃である高融点（１３５℃）の高分子型帯電防止剤（帯防２、帯防３）を用いたものであるが、４８時間（２日間）という中期連続生産においてすでに貫通孔の発生がみられ、１６８時間（７日間）という長期の連続生産にあってはなおさら貫通孔の発生が著しいものであり、生産効率の低いものであることが分かる。 In contrast, the foamed sheets obtained in Comparative Examples 1 and 2 have a high melting point (135 ° C.) polymer antistatic agent (Band 2 and Bamboo 3) having a melting point difference of 28 ° C. from that of low density polyethylene. However, in the medium-term continuous production of 48 hours (2 days), the generation of through-holes has already been observed, and in the long-term continuous production of 168 hours (7 days), the generation of through-holes is still remarkable. It can be seen that the production efficiency is low.
　比較例３で得られる発泡シートは低密度ポリエチレンとの融点差が－１５℃である高分子帯電防止剤（帯防４：融点９２℃）を用いたものであるが、配合量が少量の場合には小孔や貫通孔のない高品質な発泡シートが得られるものの、十分な帯電防止性能が発現しない。そこで、比較例４のように、帯電防止能を十分に発現させようとしてその配合量を多くすると、こんどはメルトフローレイトが低い帯防４が多量であるため、発泡シートを安定して製造することが困難であった。 The foamed sheet obtained in Comparative Example 3 uses a polymer antistatic agent having a melting point difference of −15 ° C. with respect to low density polyethylene (Band prevention 4: melting point 92 ° C.). Although a high-quality foam sheet having no small holes or through holes can be obtained, sufficient antistatic performance is not exhibited. Therefore, as in Comparative Example 4, when the blending amount is increased in order to sufficiently develop the antistatic ability, the foamed sheet is stably produced because the amount of the belt protection 4 having a low melt flow rate is large. It was difficult.
　比較例５で得られる発泡シートは実施例２と対比されるものであり、低密度ポリエチレン系樹脂との融点差が大きい帯電防止剤では長期連続生産に不向きであることがわかる。 The foamed sheet obtained in Comparative Example 5 is in contrast to Example 2, and it can be seen that the antistatic agent having a large melting point difference from the low density polyethylene resin is not suitable for long-term continuous production.
　なお、表４において各種物性は以下のように測定した。 In Table 4, various physical properties were measured as follows.
（発泡シートの厚み）
　発泡シートの平均厚みは、株式会社山文電気製オフライン厚み測定機ＴＯＦ－４Ｒを使用し測定した。まず発泡シート全幅について、１ｃｍ間隔で厚みの測定を行った。この１ｃｍ間隔で測定される発泡シート厚みを基に、全幅の算術平均厚みを求めた。尚、上記の測定に使用する発泡シートは、温度２３±５℃、相対湿度５０％の条件下で４８時間状態調整したものを用いた。 (Thickness of foam sheet)
The average thickness of the foamed sheet was measured using an offline thickness measuring machine TOF-4R manufactured by Yamabun Electric Co., Ltd. First, the thickness of the foam sheet was measured at intervals of 1 cm. Based on the thickness of the foam sheet measured at intervals of 1 cm, the arithmetic average thickness of the full width was obtained. In addition, the foam sheet used for said measurement used what adjusted the state for 48 hours on the conditions of temperature 23 +/- 5 degreeC and relative humidity 50%.
（発泡シートの坪量）
　発泡シートの坪量は、発泡シート全幅に亘って幅２５０ｍｍの矩形状の試験片を切り出し、該試験片の重量（ｇ）を該試験片の面積（シート幅（ｍｍ）×２５０ｍｍ）で割り算し、１ｍ２当たりの発泡シートの重量（ｇ）に換算し、これを発泡シートの坪量（ｇ／ｍ２）とした。 (Basis weight of foam sheet)
The basis weight of the foam sheet is obtained by cutting out a rectangular test piece having a width of 250 mm over the entire width of the foam sheet, and dividing the weight (g) of the test piece by the area of the test piece (sheet width (mm) × 250 mm). , in terms of the weight of the foamed sheet per 1 m 2 (g), which was used as the basis weight of the foamed sheet (g / m 2).
（発泡シートの見掛け密度）
　発泡シートの見掛け密度は、上記方法により求めた発泡シートの坪量（ｇ／ｍ２）を、上記により求めた発泡シートの平均厚みで割り算して求めた。 (Apparent density of foam sheet)
The apparent density of the foam sheet was obtained by dividing the basis weight (g / m 2 ) of the foam sheet obtained by the above method by the average thickness of the foam sheet obtained above.
（貫通孔等の発生）
　（短期）
発泡シート製造時に欠点検出器を用いて発泡シートの表面を製造開始４８時間経過後、１時間観察し、次の基準により評価した。
good：４８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が３個未満
poor：４８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が３個以上５個未満
bad：４８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が５個以上
　（長期）
発泡シート製造時に欠点検出器を用いて発泡シートの表面を製造開始１６８時間経過後、１時間観察し、次の基準により評価した。
good：１６８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が３個未満
poor：１６８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が３個以上５個未満
bad：１６８時間経過後、１時間に発生した１ｍｍ以上の貫通孔の数が５個以上
－：評価できず（発泡シートが形成できない） (Generation of through holes, etc.)
(Short term)
When the foam sheet was manufactured, the surface of the foam sheet was observed for 1 hour after the start of the production using a defect detector for 48 hours and evaluated according to the following criteria.
good: The number of through-holes of 1 mm or more generated in 1 hour after 48 hours passed is less than 3
poor: 3 or more and less than 5 through-holes of 1 mm or more generated in 1 hour after 48 hours
bad: After 48 hours, the number of 1mm or more through-holes generated in 1 hour is 5 or more (long term)
The surface of the foam sheet was observed for 1 hour after the start of production using a defect detector at the time of production of the foam sheet, and evaluated according to the following criteria.
good: After 168 hours have passed, the number of through-holes of 1 mm or more generated in 1 hour is less than 3
poor: The number of through-holes of 1 mm or more generated in 1 hour after 168 hours passed is 3 or more and less than 5
bad: After 168 hours have passed, the number of through-holes of 1 mm or more generated in 1 hour is 5 or more-: cannot be evaluated (foamed sheet cannot be formed)
（表面抵抗率）
　表面抵抗率は、下記の試験片の状態調節を行った後、ＪＩＳ　Ｋ６２７１：２００８に準拠して測定した。具体的には、測定対象物である発泡シートから無作為に切り出した５片の試験片（縦１００ｍｍ×横１００ｍｍ×厚み：測定対象物厚み）を温度２３℃、相対湿度５０％の雰囲気下に３６時間放置することにより試験片の状態調節を行った。次いで、それぞれの試験片の両面に対して温度２３℃、相対湿度５０％の雰囲気下で印加電圧５００Ｖの条件にて、試験片に電圧を印加した。電圧印加を開始して１分経過後の表面抵抗率を測定し、それらの算術平均値（試験片５片×両面［ｎ＝１０］）を積層発泡シートの表面抵抗率とした。 (Surface resistivity)
The surface resistivity was measured according to JIS K6271: 2008 after adjusting the state of the following test piece. Specifically, five test pieces (length 100 mm × width 100 mm × thickness: thickness of measurement object) randomly cut out from the foamed sheet as the measurement object are placed in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50%. The condition of the test piece was adjusted by leaving it for 36 hours. Next, a voltage was applied to the test piece under the conditions of an applied voltage of 500 V in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50% on both surfaces of each test piece. The surface resistivity after 1 minute from the start of voltage application was measured, and the arithmetic average value (5 test pieces × both sides [n = 10]) was defined as the surface resistivity of the laminated foam sheet.

Claims (6)

  1. 　低密度ポリエチレン、物理発泡剤及び帯電防止剤を含有する発泡性溶融樹脂組成物を押出して発泡させて、ポリエチレン系樹脂押出発泡シートを製造する方法であって、
    　発泡シートの厚みが０．０５～０．５ｍｍの範囲内であり、帯電防止剤として、低密度ポリエチレンとの融点差が－１０～＋１０℃の範囲内の融点を有し、かつメルトフローレイトが１０ｇ／１０分以上である高分子型帯電防止剤を用いることを特徴とするポリエチレン系樹脂押出発泡シートの製造方法。     A method for producing a polyethylene resin extruded foam sheet by extruding and foaming a foamable molten resin composition containing low density polyethylene, a physical foaming agent and an antistatic agent,
    The thickness of the foam sheet is in the range of 0.05 to 0.5 mm, the antistatic agent has a melting point difference in the range of −10 to + 10 ° C. with the low density polyethylene, and the melt flow rate is The manufacturing method of the polyethylene-type resin extrusion foam sheet characterized by using the polymer-type antistatic agent which is 10 g / 10min or more.
  2. 　前記高分子型帯電防止剤の融点が１２０℃以下であることを特徴とする請求項１に記載のポリエチレン系樹脂押出発泡シートの製造方法。 2. The method for producing a polyethylene resin extruded foam sheet according to claim 1, wherein the melting point of the polymer antistatic agent is 120 ° C. or less.
  3. 　高分子型帯電防止剤のメルトフローレイトに対する低密度ポリエチレンのメルトフローレイトの比（低密度ポリエチレンのメルトフローレイト／高分子型帯電防止剤のメルトフローレイト）が２以下であることを特徴とする請求項１または２に記載のポリエチレン系樹脂押出発泡シートの製造方法。 The ratio of the melt flow rate of the low density polyethylene to the melt flow rate of the polymer antistatic agent (the melt flow rate of the low density polyethylene / the melt flow rate of the polymer antistatic agent) is 2 or less. The manufacturing method of the polyethylene-type resin extrusion foam sheet of Claim 1 or 2.
  4. 　前記低密度ポリエチレン１００質量部に対して、高分子型帯電防止剤が３～２５質量部の範囲内で配合されていることを特徴とする請求項１から３のいずれかに記載のポリエチレン系樹脂押出発泡シートの製造方法。 The polyethylene resin according to any one of claims 1 to 3, wherein a polymer type antistatic agent is blended within a range of 3 to 25 parts by mass with respect to 100 parts by mass of the low density polyethylene. A method for producing an extruded foam sheet.
  5. 　帯電防止剤を含有し、基材樹脂が低密度ポリエチレンであるポリエチレン系樹脂押出発泡シートであって、
    　厚みが０．０５ｍｍ～０．５ｍｍの範囲内、見掛け密度が２０～４５０ｋｇ／ｍ３の範囲内であり、帯電防止剤が、低密度ポリエチレンとの融点差が－１０℃～＋１０℃の範囲内の融点を有し、かつメルトフローレイトが１０ｇ／１０分以上である高分子型帯電防止剤であることを特徴とするポリエチレン系樹脂押出発泡シート。     A polyethylene-based resin extruded foam sheet containing an antistatic agent and the base resin is low-density polyethylene,
    The thickness is in the range of 0.05 mm to 0.5 mm, the apparent density is in the range of 20 to 450 kg / m 3 , and the antistatic agent has a melting point difference from the low density polyethylene in the range of −10 ° C. to + 10 ° C. A polyethylene-based resin extruded foam sheet characterized by being a polymer-type antistatic agent having a melting point of 5 and a melt flow rate of 10 g / 10 min or more.
  6. 　請求項５に記載のポリエチレン系樹脂押出発泡シートからなるガラス板用間紙。 A glass sheet interleaf made of the polyethylene resin extruded foam sheet according to claim 5.
PCT/JP2016/059055 2015-03-26 2016-03-22 Production method for polyethylene-based resin extruded foam sheets, polyethylene-based resin extruded foam sheet, and interleaving paper for glass plates using same WO2016152878A1 (en)

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