WO2021246309A1 - ポリエチレン系樹脂多層発泡シート、ガラス板用間紙及びポリエチレン系樹脂多層発泡シートの製造方法 - Google Patents
ポリエチレン系樹脂多層発泡シート、ガラス板用間紙及びポリエチレン系樹脂多層発泡シートの製造方法 Download PDFInfo
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- WO2021246309A1 WO2021246309A1 PCT/JP2021/020387 JP2021020387W WO2021246309A1 WO 2021246309 A1 WO2021246309 A1 WO 2021246309A1 JP 2021020387 W JP2021020387 W JP 2021020387W WO 2021246309 A1 WO2021246309 A1 WO 2021246309A1
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- Prior art keywords
- polyethylene
- based resin
- layer
- resin
- weight
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Images
Classifications
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- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
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- B29C48/022—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the choice of material
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- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
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- B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
- B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Definitions
- the present invention relates to a multi-layer foam sheet, and more particularly to a polyethylene-based resin multi-layer foam sheet that can be used as a paper or a packaging material for electronic devices and the like, and a method for manufacturing the same.
- Polyethylene resin foam sheet is used in the fields of cushioning materials and packaging materials because it has both flexibility and cushioning properties.
- the polyethylene-based resin foam sheet (hereinafter, also simply referred to as a foam sheet) has a problem that static electricity is easily generated and a problem that dust is easily attached to the packaged object due to static electricity. Therefore, foam sheets with antistatic performance are used for applications that dislike the generation of static electricity and the adhesion of dust.
- Patent Document 1 describes a multilayer foam sheet in which a surface layer made of a polyolefin resin is laminated on one side or both sides of a polyolefin resin foam layer, and the surface layer contains a polymer type antistatic agent.
- the foamed sheet to be used is disclosed.
- the foamed sheet has excellent antistatic properties because the surface layer contains a polymer-type antistatic agent. Therefore, as compared with the foamed sheet using a surfactant as an antistatic agent, the foamed sheet has a significantly reduced amount of contamination due to the transfer of organic substances such as low molecular weight components to the packaged object. Therefore, the foamed sheet is suitably used as a paper or a packaging material for a glass plate for a liquid crystal panel or an object to be packaged such as an electronic device, which dislikes adhesion of dust and low molecular weight components to the surface.
- the foamed sheet when used as a paper between glass plates and the like, the foamed sheet is required to have excellent handleability.
- Excellent handleability is a general term for foamed sheets having excellent slipperiness, blocking prevention, and stiffness (or rigidity).
- excellent slipperiness means that the frictional force generated between the foamed sheet and the object to be packaged is small, and for example, when the foamed sheet is interposed between the glasses as a paper for a glass plate and packaged, the foamed sheet is used. It means that the work of transporting and stacking on the glass plate is performed smoothly.
- blocking means that, for example, when foamed sheets are cut to a desired size and stacked, the foamed sheets stick to each other, so that the work of taking out the foamed sheets one by one can be smoothly performed. It refers to the phenomenon of disappearing, and blocking prevention is a characteristic that can prevent the occurrence of blocking.
- excellent stiffness means that the amount of horizontal sagging when cantilevering the foam sheet is small.
- the foam sheet is used as the interstitial paper, the work of removing the foam sheet sandwiched between the glass plates from the glass plates by vacuum suction is performed. At that time, if the horizontal sagging amount is small, the interleaving paper can be easily removed, but if the horizontal sagging amount when the foam sheet cantilever is large, the efficiency of the removing operation is significantly lowered. Therefore, the foamed sheet used as the interleaving paper is required to have good elasticity.
- Patent Document 2 describes a polyethylene-based resin foamed layer, a polyethylene-based resin laminated and adhered to both sides of the foamed layer, a polystyrene-based resin, and a polymer type. Disclosed is a foamed sheet having a three-layer structure having an antistatic layer containing an antistatic agent.
- the present invention maintains the excellent cushioning property inherent in a polyethylene-based resin foam sheet, and in addition to having good elasticity, it has excellent slipperiness, excellent antistatic property, and a low molecular weight component for an object to be packaged. It is an object of the present invention to provide an antistatic polyethylene-based resin multilayer foamed sheet and a method for producing the same, which can suppress the migration of such substances to an extremely small extent.
- the multilayer foamed sheet shown below is provided.
- a polyethylene-based resin multilayer foamed sheet having a foamed layer and resin layers laminated on both sides of the foamed layer.
- the resin layer has a multi-layer structure including a surface layer located on the outermost surface side of the multi-layer foam sheet and an intermediate layer located between the surface layer and the foam layer.
- the foam layer contains polyethylene-based resin PE2 and contains
- the intermediate layer is composed of an antistatic resin composition containing a polyethylene-based resin PE3 and a polymer-type antistatic agent.
- the surface layer is composed of a mixed resin containing polyethylene-based resin PE4 and polystyrene-based resin.
- the mixed resin is substantially free of polymeric antistatic agents and is free of charge.
- the content of the polystyrene-based resin in the mixed resin is 3% by weight or more and 35% by weight or less.
- the content of the polymer-type antistatic agent in the antistatic mixture is 5% by weight or more and 25% by weight or less with respect to the total weight of the polyethylene-based resin PE3 and the polymer-type antistatic agent.
- the antistatic mixture contains polyalkylene glycol, and the content of the polyalkylene glycol is 0.3 to 6 parts by weight based on 100 parts by weight of the total of polyethylene-based resin PE3 and the polymer-type antistatic agent.
- the content of the polymer-type antistatic agent per 1 m 2 of the intermediate layer is 0.15 g or more and 2 g or less, and the surface of the intermediate layer with respect to the content A [g / m 2] of the polymer-type antistatic agent.
- the polyethylene The polyethylene-based resin multilayer foamed sheet according to any one of 1 to 8, wherein the polyethylene-based resin PE2 is low-density polyethylene and the polyethylene-based resin PE3 is low-density polyethylene.
- the present invention provides the use of the polyethylene-based resin multilayer foamed sheet according to any one of [12] 1 to 11 as a glass plate interleaving paper.
- the present invention [13] has a surface resistivity of 1 ⁇ 10 13 ⁇ or less, and has a first surface layer, a first intermediate layer, a foam layer, a second intermediate layer, and a second.
- an antistatic resin composition containing a foamable melt M2 for forming a foam layer, which contains a polyethylene-based resin PE2 and a physical foaming agent, and a polyethylene-based resin PE3 and a polymer-type antistatic agent.
- the first composition is composed of a mixed resin containing the melt M3 for forming the first and second intermediate layers, a polyethylene-based resin PE4, and a polystyrene-based resin, and substantially free of a polymer-type antistatic agent.
- It comprises the step of co-extruding the laminate from the die to foam the effervescent melt M2.
- a method for producing a polyethylene-based resin multilayer foamed sheet wherein the polystyrene-based resin is contained in the mixed resin composition in an amount of 3% by weight or more and 35% by weight or less based on the weight of the mixed resin composition. I will provide a.
- each of the pair of resin layers laminated and adhered to both sides of the foam layer has a two-layer structure of an outermost surface layer and an intermediate layer, and the intermediate layer contains a polymer type antistatic agent.
- the intermediate layer contains a polymer type antistatic agent.
- the surface layer covering the intermediate layer does not substantially contain the polymer-type antistatic agent, so that the transfer of low molecular weight components and the like to the packaged material is suppressed to an extremely small extent. ..
- the surface layer contains a specific amount of polystyrene resin, it is excellent in handleability (slipperiness, blocking prevention property, stiffness strength).
- FIG. 1 is a schematic cross-sectional view showing an example of a multilayer foamed sheet of the present invention.
- the polyethylene-based resin multilayer foamed sheet 1 of the present invention (hereinafter, also referred to as a multilayer foamed sheet or simply a foamed sheet) is provided on each of the foamed layer 2 and both surfaces of the foamed layer 2. It has a resin layer 5 and a resin layer 5.
- Each of the resin layers 5 is an intermediate layer located between the surface layer 4 (hereinafter, may be simply referred to as a surface layer) located on the outermost surface side of the multilayer foamed sheet 1 and the surface layer 4 and the foamed layer 2. It has a multi-layer structure including 3 and.
- the multilayer foam sheet 1 specifically shown in FIG. 1 has a five-layer structure of a resin layer 5 (surface layer 4 / intermediate layer 3) / foam layer 2 / resin layer 5 (intermediate layer 3 / surface layer 4).
- the foamed sheet 1 of the present invention is not limited to such a five-layer structure.
- a 6-layer structure or a 7-layer structure can be obtained by providing an additional layer made of a polymer such as a resin between one or both resin layers and the foamed layer. (Not shown).
- the following description is made for one of the pair of resin layers 5 for the sake of brevity, but the description also applies to the other resin layer.
- the two resin layers 5 can have the same or different configurations as long as the requirements detailed below are met.
- the physical property values such as the resin component, the type and amount of additives, and the basis weight of one of the two surface layers 4 may be the same as or different from those of the other surface layer.
- the numerical range "A to B" is intended to include the lower limit “A” and the upper limit "B”, and is therefore synonymous with "A or more and B or less”.
- the resin layer 5 (surface layer 4 and / or intermediate layer 3) is not foamed (non-foamed).
- very small bubbles may be present in a range that does not affect the mechanical strength of the obtained foamed sheet 1.
- the stiffness of the multilayer foamed sheet 1 becomes more excellent.
- the multilayer foamed sheet 1 of the present invention exhibits excellent antistatic properties having a surface resistivity of 1 ⁇ 10 13 ⁇ or less because the intermediate layer 3 contains a polymer-type antistatic agent. ..
- the surface layer 4 does not contain the polymer-type antistatic agent, the low molecular weight component contained in the polymer-type antistatic agent is prevented from being transferred to the packaged object.
- the surface layer 4 contains a specific amount of polystyrene-based resin, the handling property (slipperiness, blocking prevention property, stiffness strength, etc.) is excellent.
- the foamed layer 2 is composed of a base polymer containing a polyethylene-based resin PE2, and the intermediate layer 3 is an antistatic resin composition containing a polyethylene-based resin PE3 and a polymer-type antistatic agent (hereinafter, simply a resin).
- the surface layer 4 is composed of a mixed resin containing a polyethylene-based resin PE4 and a polystyrene-based resin (hereinafter, also referred to as a mixed resin R4).
- the polyethylene-based resins PE2, PE3 and PE4 mean polyethylene-based resins containing 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% of ethylene components.
- Specific polyethylene-based resins include, for example, low-density polyethylene (LDPE), ethylene-vinyl acetate copolymer (EVA), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (VLDPE), and mixtures thereof. And so on.
- the low-density polyethylene, a long chain branched structure has a density of say a 910 kg / m 3 or more 930 kg / m 3 than polyethylene resin
- the linear low density polyethylene, ethylene and number from 4 to 8 carbon atoms a copolymer of ⁇ - olefins are substantially molecular chains
- linear density refers to 910 kg / m 3 or more 930 kg / m 3 than polyethylene resin, high density polyethylene, ethylene homopolymer
- the foam layer 2 is composed of a base polymer containing a polyethylene-based resin PE2. That is, the foam layer 2 contains the polyethylene-based resin PE2. Specifically, the content of the polyethylene resin PE2 in the foam layer is 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, and particularly most preferably. 90% by weight or more.
- base polymer is intended to mean any polymer, resin or composition capable of forming a foam with a large number of bubbles by extrusion foaming.
- the polyethylene-based resin PE2 contains low-density polyethylene in an amount of 50% by weight or more because the low-density polyethylene has excellent foamability and gives a multi-layer foamed sheet having more excellent cushioning properties. From this point of view, the polyethylene-based resin PE2 preferably contains low-density polyethylene in an amount of 80% by weight or more, and more preferably 90% by weight or more.
- the melt flow rate (MFR) of the polyethylene resin PE2 is preferably 0.1 to 20 g / 10 min, more preferably 0.1 to 10 g / 10 min, and 0.1 to 0.1 min, because it has excellent foamability. It is more preferably ⁇ 5 g / 10 min.
- the multilayer foamed sheet of the present invention is preferably produced by a coextrusion method, and in that case, it is particularly preferable to use a polyethylene resin (A) having a melt flow rate (MFR) of 0.1 to 1.5 g / 10 min. preferable. The reason will be described in detail in the section of the method for manufacturing a multilayer foamed sheet.
- the melt flow rate (MFR) of the polyethylene resin in the present specification means a melt mass flow rate measured under the conditions of 190 ° C. and a load of 2.16 kg based on JIS K 7210-1 (2014).
- a resin other than the polyethylene resin or another polymer such as an elastomer can be added to the base polymer containing the polyethylene resin PE2 constituting the foam layer.
- the blending amount is preferably 20 parts by weight or less, more preferably 10 parts by weight, based on 100 parts by weight of the polyethylene-based tree resin (PE2) constituting the foam layer. Parts or less, more preferably 5 parts by weight or less, and particularly preferably 3 parts by weight or less.
- the base polymer constituting the foam layer contains a bubble regulator, a nucleating agent, an antioxidant, a heat stabilizer, a weather resistant agent, an ultraviolet absorber, and a flame retardant as long as the object and effect of the present invention are not impaired.
- Antibacterial agents, shrinkage inhibitors, inorganic fillers and other additives can be added.
- the intermediate layer is composed of an antistatic resin composition R3 containing a polyethylene-based resin PE3 and a polymer-type antistatic agent. That is, the intermediate layer includes the polyethylene-based resin PE3 and the polymer-type antistatic agent.
- the polyethylene-based resin PE3 is the main component of the intermediate layer. Specifically, the content of the polyethylene-based resin is preferably 50% by weight or more, more preferably 60% by weight or more, based on the weight of the intermediate layer (that is, the weight of the antistatic resin composition R3). More preferably, it is 70% by weight or more.
- polyethylene-based resin PE3 it is preferable to use the same type of polyethylene-based resin PE3 as the polyethylene-based resin PE2 constituting the foamed layer because it has excellent adhesiveness to the foamed layer.
- low density polyethylene is preferable.
- different types of polyethylene-based resins can also be used.
- the antistatic resin composition (R3) constituting the intermediate layer contains a polymer type antistatic agent
- the surface layer is laminated on the intermediate layer. It is possible to exhibit excellent antistatic properties.
- the surface resistivity of the multilayer foamed sheet needs to be 1 ⁇ 10 13 ⁇ or less, preferably 5 ⁇ 10 12 ⁇ or less, and more preferably 1 ⁇ 10 12 ⁇ or less. Particularly preferably, it is 5 ⁇ 10 11 ⁇ or less.
- the lower limit of the surface resistivity is not particularly limited, it is generally 1 ⁇ 10 7 ⁇ . A multilayer foamed sheet having a surface resistivity in such a range is less likely to accumulate static charges and to be less likely to adhere dust.
- the surface resistivity of the multi-layer foam sheet is a value measured in accordance with JIS K6271 (2001). More specifically, first, a test piece (length 100 mm ⁇ width 100 mm ⁇ thickness: thickness of the object to be measured) cut out from the multilayer foam sheet to be measured is left for 24 hours in an atmosphere having a temperature of 23 ° C and a relative humidity of 50%. The condition of the test piece is adjusted by. Next, a voltage of 500 V is applied to the surface of the test piece in an atmosphere of a temperature of 23 ° C. and a relative humidity of 50%, and the surface resistivity is measured 1 minute after the voltage application is started.
- the polymer-type antistatic agent is made of a resin having a surface resistivity of usually less than 1 ⁇ 10 12 ⁇ , preferably less than 1 ⁇ 10 11 ⁇ , and more preferably less than 1 ⁇ 10 10 ⁇ .
- Specific examples thereof include polyethers, polyether ester amides, block copolymers of polyethers and polyolefins, ionomer resins and the like.
- block copolymers of polyether and polyolefin and ionomer resins are more preferable, and ionomer resins are particularly preferable.
- the ionomer resin has a low surface resistivity, can impart good antistatic performance to a multilayer foamed sheet, and has a low content of low molecular weight components. Therefore, due to the transfer of low molecular weight components to the packaged material. , Contamination of the packaged object can be further suppressed.
- Foamed sheets containing ionomer resin tend to be inferior in slipperiness to foamed sheets containing other polymer-type antistatic agents such as a polyether-polyolefin block copolymer.
- the intermediate layer containing the ionomer resin is covered with the surface layer described later, it is possible to prevent the slipperiness from being lowered even with the foamed sheet containing the ionomer resin.
- Ionomer resin is a resin in which the molecules of a copolymer of an olefin and an unsaturated carboxylic acid are cross-linked with metal ions.
- the olefin include ethylene and propylene.
- unsaturated carboxylic acids include acrylic acid, methacrylic acid, and maleic acid.
- the metal ion include lithium, sodium, potassium and the like.
- an ionomer resin containing potassium as a metal ion, particularly a potassium-containing ionomer resin obtained by a copolymer of ethylene and an unsaturated carboxylic acid is preferable because it can impart good antistatic performance to the foamed sheet.
- the surface resistivity of the ionomer resin is preferably less than 1 ⁇ 10 12 ⁇ .
- the surface resistivity is more preferably 1 ⁇ 10 11 ⁇ or less, further preferably 1 ⁇ 10 10 ⁇ or less, and particularly preferably 1 ⁇ 10 9 ⁇ or less.
- the surface resistivity of the ionomer resin can be measured by the same method as the measurement of the surface resistivity of the multilayer foamed sheet.
- polymer-type antistatic agent examples include "Perestat 300", “Perestat 230", “Perestat HC250", and “Perectron PVH” manufactured by Sanyo Kasei Kogyo Co., Ltd. as block copolymers of polyether and polyolefin.
- Perectron PVL examples include "Perectron HS”, “Perectron LMP”, etc., as ionomer resins, those commercially available under trade names such as "Entila SD100", “Entila MK400” manufactured by Mitsui-DuPont Polychemical Co., Ltd. can be mentioned. ..
- the content of the polymer-type antistatic agent in the antistatic resin composition R3 depends on the performance of the polymer-type antistatic agent itself, but the polyethylene-based resin PE3 and the polymer-type It is preferably 5 to 25% by weight based on 100% by weight of the total with the antistatic agent.
- the content (concentration) of the polymer-type antistatic agent is 5% by weight or more, the conductive network structure of the polymer-type antistatic agent is stably formed in the intermediate layer, so that the surface layer is formed on the intermediate layer. Despite the fact that they are laminated, antistatic performance is evenly exhibited throughout the foamed sheet.
- the content when the content is 25% by weight or less, the contamination of the packaged object due to the migration of the low molecular weight component derived from the high molecular weight antistatic agent can be further reduced. In addition, it is possible to more reliably prevent a decrease in slipperiness due to the polymer-type antistatic agent. For this reason, the lower limit of the content is more preferably 7% by weight, still more preferably 9% by weight. On the other hand, the upper limit of the content is more preferably 20% by weight, still more preferably 15% by weight.
- the content A of the polymer-type antistatic agent per 1 m 2 of the intermediate layer is preferably 0.15 to 2 g / m 2 .
- the content A represents the absolute amount of the polymer-type antistatic agent contained in the unit area of the intermediate layer.
- the lower limit of the content A is more preferably 0.18 g / m 2 , more preferably 0.19 g / m 2 , and particularly preferably 0.2 g / m 2 .
- the content A is 2 g / m 2 or less, organic substances such as low molecular weight components in the polymer-type antistatic agent contained in the intermediate layer 3 are less likely to bleed out to the surface of the surface layer 4.
- the upper limit of the content A is more preferably 1.5 g / m 2 , more preferably 1.0 g / m 2 , and particularly preferably 0.8 g / m 2 .
- the intermediate layer 3 is non-foaming in order to exhibit a sufficient antistatic effect while keeping the value of the content A in the above range.
- the content A is a value per one of the pair of intermediate layers 3 provided on both sides of the foam layer 2.
- the ratio B4 / A of the basis weight B4 [g / m 2 ] of the surface layer 4 to the content A [g / m 2 ] of the polymer-type antistatic agent per 1 m 2 of the intermediate layer 3. is preferably 1 to 30. When the ratio is within this range, the balance between antistatic property and antifouling property becomes better.
- the ratio B4 / A is an index showing the ratio of the basis weight B4 of the surface layer 4 to the weight per unit area of the polymer-type antistatic agent contained in the intermediate layer 3.
- the content A of the high molecular weight antistatic agent may be reduced, or the basis weight B4 of the surface layer 4 may be reduced. It is preferable to increase the number (increase the thickness of the surface layer 4).
- the content A of the high molecular weight antistatic agent is increased, or the basis weight B4 of the surface layer is reduced (the thickness of the surface layer is reduced). ) Is preferable.
- the ratio B4 / A is preferably in the above range in order to suppress the migration of low molecular weight components and exhibit sufficient antistatic performance.
- the lower limit of the ratio B4 / A is preferably 2, more preferably 3, and even more preferably 4.
- the upper limit of the ratio is preferably 25, more preferably 20, still more preferably 15, and particularly preferably 10.
- the intermediate layer 3 When an ionomer resin is used as the polymer type antistatic agent, adding polyalkylene glycol to the intermediate layer 3 can uniformly disperse the ionomer resin in the intermediate layer, whereby the foamed sheet has excellent antistatic properties. It is preferable because the performance can be stably exhibited. That is, when a foamed sheet is produced by coextrusion, if the melt for forming an intermediate layer to be extruded (that is, the melted antistatic resin composition R3) contains polyalkylene glycol, the polyethylene resin PE3 The ionomer resin can be satisfactorily dispersed therein, and a multilayer foamed sheet having excellent antistatic performance can be obtained even though the intermediate layer is coated with a surface layer. Further, since the intermediate layer contains polyalkylene glycol, the humidity dependence of the antistatic performance is reduced, and a multilayer foamed sheet exhibiting good antistatic performance even under low humidity conditions can be obtained. ..
- polyalkylene glycol a polyalkylene glycol having an HLB value of 8 or more can be preferably used.
- polyalkylene glycols include polyethylene glycol, polyoxyethylene polyoxypropylene glycol and the like. Further, two or more kinds of polyalkylene glycols may be used in combination.
- polyethylene glycol is preferably used because it can stably disperse the ionomer resin in the polyethylene resin and can further reduce the humidity dependence of the antistatic performance while enhancing the antistatic performance.
- Mh is the molecular weight of the hydrophilic portion of the hydrophilic compound
- Mw is the molecular weight of the entire hydrophilic compound.
- the content of polyalkylene glycol in the antistatic resin composition R3 (that is, the intermediate layer) is 0.3 to 8 parts by weight with respect to 100 parts by weight of the total of the polyethylene resin PE3 and the polymer type antistatic agent. It is preferable to have.
- the content thereof is preferably 0.3 to 6 parts by weight based on 100 parts by weight of the total of the polyethylene resin PE3 and the polymer-type antistatic agent, and the lower limit thereof. Is more preferably 0.35 parts by weight, still more preferably 0.4 parts by weight.
- the upper limit is more preferably 5 parts by weight, still more preferably 3 parts by weight, and particularly preferably 2 parts by weight.
- the weight ratio of the polyalkylene glycol to the ionomer resin is 0.03 to 0.5 so that the ionomer resin can be better dispersed in the polyethylene resin. It is preferable because it can be used. From this point of view, the weight ratio is more preferably 0.04 to 0.3.
- the antistatic resin composition R3 constituting the intermediate layer may contain other polymers, additives, etc. in addition to the polyethylene-based resin PE3 and the polymer-type antistatic agent as long as the objective effect of the present invention is not impaired. good. It is preferable that the antistatic resin composition R3, that is, the intermediate layer does not substantially contain the polystyrene-based resin. Specifically, the content of the polystyrene-based resin in the antistatic resin composition R3 is preferably 5% by weight or less, more preferably 3% by weight or less, and 2 parts by weight or less. Is more preferable, and it is particularly preferable that the content is 0.
- the closed cell ratio of the multilayer foamed sheet can be further increased, and the stiffness and cushioning properties can be further enhanced. In addition, recyclability can be improved.
- the surface layer is composed of a mixed resin R4 containing a polyethylene-based resin PE4 and a polystyrene-based resin. That is, the surface layer contains polyethylene-based resin PE4 and polystyrene-based resin.
- the polyethylene-based resin PE4 is the main component of the surface layer. Specifically, the content of the polyethylene-based resin PE4 is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 60% by weight or more, based on the weight of the surface layer (that is, the weight of the resin mixture R4). It is 70% by weight or more.
- the polyethylene-based resin PE4 the polyethylene-based resin exemplified as the polyethylene-based resin PE3 can be used. It is preferable to use the same type of polyethylene resin PE 3 as the resin layer 5 having excellent adhesiveness between the surface layer 4 and the intermediate layer 3. Specifically, the polyethylene-based resin PE4 preferably contains low-density polyethylene in an amount of 50% by weight or more. Further, when linear low-density polyethylene is used as the polyethylene-based resin PE4, the amount of migration of low molecular weight components can be further suppressed. However, different types of polyethylene-based resins can also be used.
- the mixed resin R4 does not substantially contain a polymer-type antistatic agent. Since the surface layer is located on the outermost surface side of the foamed sheet and comes into direct contact with the packaged object, the mixed resin R4 constituting the surface layer does not contain a polymer-type antistatic agent, so that the surface layer is high. Contamination of the packaged material due to the transfer of low molecular weight components contained in the molecular antistatic agent is prevented. Further, even if the surface layer does not contain a polymer-type antistatic agent, the desired antistatic property can be exhibited by containing the polymer-type antistatic agent in the intermediate layer.
- substantially free of polymer-type antistatic agent means that the content of the polymer-type antistatic agent is the weight of the mixed resin R4 (that is, the surface layer). On the other hand, it means that it is approximately 3% by weight or less (including 0). The content is more preferably 1% by weight or less (including 0). In order to suppress the migration of the low molecular weight component, it is particularly preferable that the mixed resin R4 does not contain the polymer antistatic agent, that is, the content is 0. Further, in the multilayer foamed sheet of the present invention, it is preferable that the surface layer does not substantially contain an antistatic agent other than the polymer type antistatic agent. Examples of the antistatic agent other than the polymer type antistatic agent include a surfactant.
- the mixed resin R4 constituting the surface layer 4 of the multilayer foamed sheet of the present invention contains a specific amount of polystyrene resin (PS).
- PS polystyrene resin
- polystyrene-based resin examples include polystyrene (general-purpose polystyrene), rubber-modified polystyrene (impact-resistant polystyrene), styrene- ⁇ -methylstyrene copolymer, styrene-p-methylstyrene copolymer, and styrene-acrylic acid copolymer.
- Styrene-methacrylic acid copolymer Styrene-maleic anhydride copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer
- examples thereof include a copolymer and a styrene-acrylonitrile copolymer.
- polystyrene or rubber-modified polystyrene is preferable, and polystyrene is more preferable.
- the content of the polystyrene-based resin in the mixed resin R4 (that is, the surface layer) is 3% by weight or more and 35% by weight or less based on the weight of the mixed resin R4. If the content of the polystyrene-based resin in the surface layer is less than 3% by weight, the slipperiness of the foamed sheet may be insufficient depending on the application. In addition, blocking may occur when foamed sheets are stacked and stored. In order to further improve the slipperiness and blocking prevention property of the foamed sheet, it is preferable that the polystyrene-based resin is contained in the mixed resin R4 in an amount of 4% by weight or more.
- the content of the polystyrene-based resin in the mixed resin R4 is preferably 30% by weight or less, and preferably 25% by weight or less. It is more preferably 20% by weight or less, particularly preferably 12% by weight or less, and most preferably 8% by weight or less.
- the content of the polystyrene-based resin in the mixed resin R4 constituting the surface layer 4 is within the above range, the smaller the amount, the higher the stiffness.
- the stiffness tends to decrease. The reason why the stiffness strength decreases when the content of the polystyrene-based resin, which is a resin having a higher rigidity than the polyethylene-based resin PE4, increases is not clear, but is considered as follows.
- the foamed sheet of the present invention when the foamed sheet of the present invention is produced by coextrusion, when the content of the polystyrene-based resin in the mixed resin R4 forming the surface layer becomes large, the polystyrene-based resin has a higher extrusion temperature than the molten polyethylene-based resin PE4. Since the fluidity in the vicinity is low, the melt viscosity of the surface layer forming melt (that is, the melted mixed resin R4) increases. Therefore, the foamable melt for forming the foam layer co-extruded in the co-extruded die generates heat, and the closed cell ratio of the obtained foam layer decreases, and as a result, the stiffness of the multilayer foam sheet decreases. Conceivable.
- the ratio PS (C) / PE (C) of the content (PS (C)) of the polystyrene-based resin (PS) to the content (PE (C)) of the polyethylene-based resin PE4 in the mixed resin R4 is It is preferably 0.03 to 0.6.
- the ratio PS (C) / PE (C) is within this range, it means that the content of the polystyrene-based resin (PS) is smaller than that of the polyethylene-based resin PE4.
- the upper limit of the ratio PS (C) / PE (C) is preferably 0.4, more preferably 0.3, still more preferably 0.2. , Particularly preferably 0.1. Further, in order to improve the slipperiness and blocking prevention property of the foamed sheet, the lower limit of the ratio PS (C) / PE (C) is more preferably 0.04.
- the tensile strength of the mixed resin R4 constituting the surface layer 4 is preferably 10 MPa or more.
- the tensile strength can be adjusted by changing the content of the polystyrene-based resin in the mixed resin R4 within the above range.
- the tensile strength of the mixed resin R4 conforms to JIS K6767: 1999, and is measured and calculated under the condition of a test speed of 500 mm / min using a test piece punched into a dumbbell type No. 1 type, and the calculated value is adopted. ..
- the mixed resin R4 preferably contains a compatibilizer for the polyethylene-based resin PE4 and the polystyrene-based resin. Since the compatibilizer can improve the film-forming property of the mixed resin R4, a good surface layer can be formed even if the basis weight of the surface layer is small.
- the compatibilizer examples include styrene-butadiene copolymers, styrene-isoprene copolymers, and styrene-based elastomers such as hydrogenated products of these copolymers.
- the copolymer is preferably a block copolymer.
- the content of the compatibilizer in the mixed resin R4 is preferably 1 to 20 parts by weight with respect to 100 parts by weight in total of the polyethylene resin PE4, the polystyrene resin and the compatibilizer.
- the lower limit of the content is more preferably 2 parts by weight, and the upper limit thereof is more preferably 15 parts by weight, still more preferably 10 parts by weight.
- the multilayer foamed sheet of the present invention has a higher stiffness than the conventional foamed sheet because the mixed resin R4 constituting the surface layer contains a predetermined amount of polystyrene-based resin. Further, the multilayer foamed sheet is excellent in followability at the time of vacuum suction and the like, and even when the thickness is thin, it can be handled in the same manner as the conventional one having a large thickness.
- the compatibilizer is present in the mixed resin R4
- the dispersibility of the polystyrene-based resin in the polyethylene-based resin PE4 is improved in the mixed resin R4, so that the foamable sheet has a handling property such as stiffness. Improve more. It was
- the total basis weight of the multilayer foamed sheet of the present invention is preferably 5 to 100 g / m 2 , more preferably 10 to 90 g / m 2 , still more preferably 20 to 80 g / m 2 , and particularly preferably 25 to 50 g. / M 2 .
- the basis weight of the multilayer foamed sheet is within this range, the balance between lightness and mechanical properties is good.
- the basis weight B3 of the intermediate layer 3 is preferably 1 to 10 g / m 2.
- the basis weight B3 of the intermediate layer is 1 g / m 2 or more, the variation in the antistatic property (surface resistivity) is small. From this point of view, the basis weight B3 is more preferably 1.5 g / m 2 or more, and further preferably 1.8 g / m 3 or more. Further, when the basis weight B3 is 10 g / m 2 or less, the migration of low molecular weight components derived from the polymer antistatic agent is more likely to be suppressed, and the closed cell ratio of the foamed sheet can be further increased. The stiffness of the foam sheet can be further improved. From this point of view, the basis weight B3 of the intermediate layer is more preferably 8 g / m 2 or less, still more preferably 6 g / m 2 or less.
- the basis weight B4 of the surface layer 4 is preferably 0.5 to 10 g / m 2.
- the basis weight B4 is within this range, bleed-out of the low molecular weight component derived from the polymer-type antistatic agent can be more effectively suppressed, and good antistatic properties are more reliably exhibited. be able to.
- the lower limit of the basis weight B4 is more preferably 0.8 g / m 2 and even more preferably 1.0 g / m 2 .
- the upper limit of the basis weight B4 is more preferably 8 g / m 2 , more preferably 5 g / m 2 , and particularly preferably 3 g / m 2 .
- the ratio B4 / B3 of the basis weight B4 of the surface layer to the basis weight B3 of the intermediate layer is preferably 0.05 to 10, more preferably 0.1 to 3, and further preferably 0.2 to 2. , Particularly preferably 0.3 to 1.5.
- the ratio B4 / B3 is within the above range, it is possible to achieve both suppression of migration of low molecular weight components derived from the polymer-type antistatic agent and antistatic properties in a more balanced manner.
- the basis weight of the resin layer 5 (total of the basis weight B4 of the surface layer and the basis weight B3 of the intermediate layer) is preferably 20 g / m 2 or less. When the basis weight of the resin layer is within this range, the lightness of the foamed sheet is not impaired, and the cushioning property required for use as a blank sheet or the like can be secured. Further, when the resin layer 5 (intermediate layer 3 and surface layer 4) is laminated on the foam layer 2 by coextrusion described later, the foam layer 2 having a good bubble structure can be formed.
- the basis weight of the resin layer is more preferably 15 g / m 2 or less, more preferably 10 g / m 2 or less, and particularly preferably 8 g / m 2 or less.
- the lower limit of the basis weight of the resin layer 5 is preferably 1 g / m 2 and more preferably 2 g / m 2 in consideration of appropriate stiffness strength when used as a paper sheet or the like.
- the above-mentioned basis weight is the basis weight of the resin layer 5, the surface layer 4, and the intermediate layer 3 provided on one of both sides of the foam layer 2.
- the basis weight of one layer is preferably equal to the basis weight of the other corresponding layer, but they may differ from each other.
- the inclusion of the high molecular weight antistatic agent per 1 m 2 of the intermediate layer is 0.15 g or more and 2 g or less, and the ratio (B4 / A) of the basis weight B4 [g / m 2 ] of the surface layer to the content A [g / m 2] of the polymer-type antistatic agent is It is most preferably 1 or more and 30 or less, and the basis weight B4 of the surface layer is 0.5 g / m 2 or more and 10 g / m 2 or less.
- the apparent density of the multilayer foamed sheet 1 of the present invention is preferably 10 to 300 kg / m 3.
- the foamed sheet has an excellent balance between mechanical properties such as high elasticity, light weight, and cushioning property.
- the lower limit of the apparent density is more preferably 15 kg / m 3 and even more preferably 20 kg / m 3 .
- the upper limit of the apparent density is more preferably 200 kg / m 3 and even more preferably 100 kg / m 3 .
- the total thickness of the foamed sheet is preferably 0.05 to 3 mm, more preferably 0.1 to 2 mm, still more preferably 0.3 to 1.8 mm, and particularly preferably 0.5 to 1.5 mm. ..
- the thickness of the foamed sheet is within this range, the balance between cushioning property and flexibility is good. In addition, the stiffness becomes better.
- the thickness, basis weight, and apparent density of the multilayer foamed sheet are measured as follows. First, a multilayer foamed sheet is cut out vertically (that is, in the thickness direction) along its width direction (that is, in a direction perpendicular to the extrusion direction), and a rectangular test having a length equal to the total width [mm] of the sheet and a width of 100 mm. Get a piece. The same operation is repeated at different positions on the foam sheet to obtain a total of 5 test pieces. The thickness of each test piece is measured at 1 cm intervals in the width direction of the foam sheet. The arithmetic mean value of the obtained thickness value is the thickness [mm] of the multilayer foamed sheet.
- the weight [g] of each test piece is measured.
- the measured weight is divided by the area of the test piece [m 2 ] (that is, the width of the sheet [m] ⁇ 100 mm (0.1 m)).
- the arithmetic mean value of the obtained five values is the basis weight [g / m 2 ] of the multilayer foamed sheet.
- the apparent density [kg / m 3 ] of the multilayer foamed sheet is obtained by dividing the basis weight [g / m 2 ] of the foamed sheet obtained above by the thickness [m] of the foamed sheet obtained above (appropriate unit conversion). With).
- the basis weight of the intermediate layer 3 and the surface layer 4 can be obtained from the thickness of each layer and the density of the resin composition constituting each layer. More specifically, the multilayer foam sheet is cut vertically (that is, in the thickness direction) along the width direction, and the vertical cross sections are photographed at 10 positions (per one side of the foam sheet) evenly spaced in the width direction. In each of the 10 magnified photographs of the cut foam sheet in each vertical cross section, the thickness of each of the intermediate layer and the surface layer is measured at 1 cm (actual length) intervals in the width direction. The arithmetic mean value of each of the obtained intermediate layer and surface layer thickness values is the thickness of the intermediate layer and the surface layer on the corresponding surface of the foamed sheet.
- the basis weight of the intermediate layer and the surface layer can be calculated by multiplying the thickness by the density of the resin composition constituting each layer (with appropriate unit conversion).
- resin composition used here is intended to include not only polyethylene-based resin components but also other polymer components and inorganic components used for each layer.
- the basis weight of the intermediate layer and the surface layer can be obtained based on the discharge amount of each layer at the time of manufacturing the multilayer foamed sheet.
- the basis weight B3 [g / m 2 ] of the intermediate layer can be calculated by the following equation.
- B3 [1000 ⁇ X / (L ⁇ W)]
- X is the discharge amount of the intermediate layer [kg / hour]
- L is the take-up speed of the foamed sheet [m / hour]
- W is the width of the foamed sheet [m].
- the basis weight B4 of the surface layer can be calculated by the following equation.
- B4 [1000 ⁇ Y / (L ⁇ W)]
- Y is the discharge amount [kg / hour] of the surface layer
- L and W are as defined above.
- the closed cell ratio of the multilayer foamed sheet of the present invention is preferably 20% or more, more preferably 30% or more, in consideration of the surface protection, cushioning property, appropriate slipperiness, elasticity and the like of the packaged object. It is more preferably 40% or more, particularly preferably 50% or more, and most preferably 60% or more.
- the upper limit of the closed cell ratio is not particularly limited, but is approximately 90%.
- the closed cell ratio is preferably 40% or more from the viewpoint of maintaining good elasticity.
- the closed cell ratio is measured according to procedure C of ASTM-D2856-70. Specifically, the true volume Vx of the multilayer foamed sheet (cut sample) is measured using an air comparison type hydrometer 930 of Toshiba Beckman Co., Ltd. Using the obtained Vx, the closed cell ratio S (%) is calculated by the following formula.
- the cut sample for measurement a plurality of samples having a thickness of 25 mm ⁇ 25 mm ⁇ multi-layer foam sheet are cut out from the multi-layer foam sheet, and the obtained samples are stacked to obtain a cut sample for measurement of 25 mm ⁇ 25 mm ⁇ about 20 mm.
- Vx is the true volume (cm 3 ) of the cut sample measured by the above method and corresponds to the sum of the volume of the resin constituting the cut sample and the total volume of bubbles in the closed cell portion in the cut sample;
- Va is the apparent volume (cm 3 ) of the cut sample calculated from the outer dimensions of the cut sample used for the measurement;
- W is the total weight (g) of the cut sample used for the measurement;
- ⁇ is the density (g / cm 3 ) of the resin composition that constitutes the multi-layer foam sheet obtained by defoaming the multi-layer foam sheet.
- the multilayer foamed sheet of the present invention can be produced by a known method.
- a melt for forming an intermediate layer and a melt for forming a surface layer are laminated on both sides of the foamable melt for forming a foam layer in this order.
- a method of producing a multilayer foamed sheet by co-extruding and foaming a foamable melt is preferable.
- the melt for forming the intermediate layer and the melt for forming the surface layer are laminated using a coextrusion die to obtain a resin layer having a multi-layer structure, and this resin layer is produced by a foam sheet (foam layer) in another step.
- a multilayer foamed sheet can also be manufactured by laminating an intermediate layer on both sides of) toward the foamed sheet side.
- the multi-layer co-extrusion method includes (1) a method of co-extruding into a sheet using a flat die to form a multi-layer foam sheet, and (2) co-extruding into a cylinder using an annular die to produce a tubular multi-layer foam. , There is a method of cutting the obtained tubular multilayer foam along the extrusion direction to obtain a multilayer foam sheet.
- a multilayer coextrusion method using an annular die can be preferably used.
- the polyethylene-based resin PE2 and an additive such as a bubble regulator added as needed are supplied to the extruder and kneaded by heating, and then the physical foaming agent is press-fitted into the extruder and further kneaded. To obtain a foamable melt M2 for forming a foam layer.
- the polyethylene-based resin PE3, the polymer-type antistatic agent, polyethylene glycol added as needed, and the like are supplied to another extruder and kneaded by heating to obtain a melt M3 for forming an intermediate layer. ..
- the polyethylene-based resin PE4 and the polystyrene-based resin (C) are supplied to another extruder and kneaded by heating to obtain a surface layer forming melt M4.
- the obtained foamable melt M2, melt M3, and melt M4 are introduced into a coextrusion annular die, and the melt M3 for an intermediate layer is laminated on both sides of the foamable melt M2 flowing in a tubular shape.
- the surface layer melt M4 is laminated on both sides thereof and extruded and foamed in the atmosphere to form a tubular foam.
- a multilayer foamed sheet can be obtained by cutting open the tubular foam while taking it along a widening device such as a mandrel.
- the two resin layers 5 can have the same or different configurations. Therefore, the composition (type and amount of resin component, additive, etc.) of the melt M3 for one of the two intermediate layers 3 may be the same as or different from that of the other intermediate layer. Similarly, the composition (type and amount of resin component, additive, etc.) of the melt M4 for one surface layer of the two surface layers 4 may be the same as or different from that of the other surface layer.
- the melt flow rate (MFR) of the polyethylene resin PE2 is 0.1 to 1.5 g / 10 min, which reduces the closed cell ratio of the foamed layer. It is preferable because it can effectively suppress the decrease in thickness recovery.
- the melt M4 for the surface layer contains a polystyrene-based resin, so that the melt viscosity tends to be high and the shear heat generation in the die tends to be large. .. As a result, the closed cell ratio and thickness recovery of the foam layer may easily decrease due to shear heat generation.
- the melt flow rate (MFR) of the polyethylene-based resin PE2 in the foam layer is 0.1 to 1.5 g / 10 min, the melt viscosity of the foamable melt M2 becomes large, so that the influence of shear heat generation is mitigated. be able to. Further, it is considered that the bubble structure is easily maintained because the polyethylene-based resin PE2 has an MFR in the above range.
- the thickness of the polyethylene-based resin foam sheet tends to decrease due to the air in the bubbles being released immediately after production. Normally, this decrease in thickness can be recovered by allowing the foamed sheet to stand (curing) at a predetermined temperature for a predetermined time, but the thickness may not increase even if it is cured for some reason. This phenomenon in which the thickness does not recover is called a decrease in thickness recovery.
- One of the causes of the decrease in recoverability is considered to be the decrease in the closed cell ratio.
- the MFR of the polyethylene-based resin PE3 and the polyethylene-based resin PE4 is equal to or larger than that of the polyethylene-based resin PE2 because the film-forming property of the resin layer is improved. Is preferable.
- a volatile plasticizer is added to each of the intermediate layer melt M3 and the surface layer melt M4.
- the volatile plasticizer has a function of lowering the melt viscosity of the melt and, after forming the resin layer (intermediate layer, surface layer), volatilizes from the intermediate layer and the surface layer and exists in the intermediate layer and the surface layer. The one that disappears is used.
- the volatile plasticizer is selected from aliphatic hydrocarbons having 3 to 7 carbon atoms, alicyclic hydrocarbons, aliphatic alcohols having 1 to 4 carbon atoms, and aliphatic ethers having 2 to 8 carbon atoms1. Species or two or more species are preferably used. When a so-called lubricant having low volatility is used instead of the volatile plasticizer, the lubricant may remain in the resin layer and contaminate the surface of the packaged object. On the other hand, the volatile plasticizer is preferable because it efficiently plasticizes the resin in the resin layer and the volatile plasticizer itself does not easily remain in the obtained resin layer.
- the boiling point of the volatile plasticizer is preferably 120 ° C. or lower, more preferably 80 ° C. or lower, because it easily volatilizes from the resin layer. If the boiling point of the volatile plasticizer is within the above range, if the obtained multilayer foamed sheet is left after co-extrusion, it will volatilize due to the heat immediately after co-extrusion and the subsequent gas permeation at room temperature. The plasticizer is naturally volatilized and removed from the resin layer (intermediate layer and surface layer). The lower limit of the boiling point of the volatile plasticizer is approximately ⁇ 50 ° C.
- the volatile plasticizer is preferably added in an amount of 5 parts by weight to 50 parts by weight with respect to 100 parts by weight of each of the melts M3 and M4.
- various additives may be added to the resin forming these melts as long as the object of the present invention is not impaired.
- various additives include antioxidants, heat stabilizers, weather resistant agents, ultraviolet absorbers, flame retardants, fillers, antibacterial agents and the like.
- the amount to be added is appropriately determined according to the purpose and effect of the additive, but is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and 3 parts by weight or less with respect to 100 parts by weight of each melt. Is particularly preferable.
- Examples of the physical foaming agent added to the foamable melt M2 for the foam layer include aliphatic hydrocarbons such as propane, normal butane, isopentane, normal pentane, isopentane, normal hexane and isohexane, cyclopentane and cyclohexane.
- a degradable foaming agent such as azodicarbonamide can also be used.
- Two or more kinds of the above-mentioned physical foaming agents can be used in combination.
- organic physical foaming agents are particularly preferable because they are excellent in compatibility with polyethylene resin and foamability, and among them, those containing normal butane, isobutane, or a mixture thereof as a main component are preferable.
- the amount of the physical foaming agent added is adjusted according to the type of foaming agent and the desired apparent density. For example, in order to obtain a multilayer foamed sheet in the apparent density range using a mixed butane of 30% by weight of isobutane and 70% by weight of normal butane as a foaming agent, the amount of the mixed butane added is per 100 parts by weight of the base material polymer. It is preferably 3 to 30 parts by weight, more preferably 4 to 20 parts by weight, and even more preferably 6 to 18 parts by weight.
- a bubble conditioner is usually added as the main additive added to the effervescent melt M2.
- the bubble adjusting agent either an organic type or an inorganic type can be used.
- the inorganic bubble adjusting agent include boric acid metal salts such as zinc borate, magnesium borate, and borax, sodium chloride, aluminum hydroxide, talc, zeolite, silica, calcium carbonate, and sodium bicarbonate.
- the organic bubble adjusting agent include sodium phosphate-2,2-methylenebis (4,6-tert-butylphenyl), sodium benzoate, calcium benzoate, aluminum benzoate, sodium stearate and the like.
- a combination of citric acid and sodium bicarbonate, an alkali salt of citric acid and sodium bicarbonate and the like can also be used as the bubble adjusting agent. Two or more of these bubble adjusting agents can be used in combination.
- the amount of the bubble adjusting agent added is preferably 0.01 to 3 parts by weight, more preferably 0.03 to 1 part by weight, per 100 parts by weight of the base polymer.
- the multilayer foamed sheet of the present invention has excellent cushioning properties and antistatic properties, and the amount of low molecular weight components transferred to the object to be packaged is extremely small. Therefore, a packaging material for electronic devices, for example, a glass plate for a liquid crystal panel. It can be suitably used as a paper for use.
- polyethylene-based resin, polystyrene-based resin, polymer-type antistatic agent, compatibilizer, and bubble adjusting agent used in Examples and Comparative Examples are as follows.
- Polyethylene resin (1) Abbreviation "LDPE1” NUC Co., Ltd. Low density polyethylene “NUC8321” (density 922 kg / m 3 , MFR 2.4 g / 10 min, melting point 112 ° C, melt viscosity 818 Pa / s (measurement temperature 190 ° C), melting Tension 64mN) (2) Abbreviation “LDPE2” Low density polyethylene “NS-1s” manufactured by NUC Co., Ltd. (density 922 kg / m 3 , MFR 0.4 g / 10 min, melting point 110 ° C., melt viscosity 1468 Pa / s (measurement temperature 190 ° C.), melt tension 199mN)
- Polystyrene resin (1) Abbreviation "GPPS1”: PS Japan Corporation general-purpose polystyrene “680” (density 1050 kg / m 3 , MFR 7.0 g / 10 min, Vicat softening temperature 98 ° C., melt viscosity 927 Pa / s (measurement temperature 200 ° C.) ), Melt tension 73mN)
- Polymer-type antistatic agent (1) Abbreviation "LMP”: Polyolefin-polyolefin block copolymer "Perectron LMP” manufactured by Sanyo Kasei Kogyo Co., Ltd. (MFR 17 g / 10 min, melting point 117 ° C., surface resistivity: 2.0 ⁇ 10) 7 ⁇ ) (2) Abbreviation “SD100”: Ethylene-based potassium ionomer resin "Entila SD100” manufactured by Mitsui-DuPont Polychemical Co., Ltd. (MFR 5 g / 10 min, melting point 92 ° C., surface resistivity: 1.0 x 10 7 ⁇ )
- Compatibility agent (1) Abbreviation "SEBS1” Hydrogenated styrene thermoplastic elastomer “Tuftec H1041” manufactured by Asahi Kasei Corporation, rubber content 70%
- Bubble conditioner Uses a bubble adjuster masterbatch containing 20% of talc (talc "high filler # 12" manufactured by Matsumura Sangyo Co., Ltd.) with 80% by weight of low density polyethylene (manufactured by Japan Polyethylene, "LA500M”). board.
- Extruder for foam layer formation Single extruder with a barrel inner diameter of 115 mm (first extruder)
- Extruder for forming intermediate layer Extruder with barrel inner diameter 65 mm (second extruder)
- Extruder for surface layer formation Extruder with barrel inner diameter of 50 mm (third extruder)
- Die An annular die for coextrusion with an outlet diameter of 96 mm
- Examples 1-9 and Comparative Examples 1-6 A foam sheet (Examples 1 to 9 and Comparative Examples 4 to 6) having a five-layer structure of a resin layer (surface layer / intermediate layer) / foam layer / resin layer (intermediate layer / surface layer) and a surface layer / foam layer / surface. Foamed sheets having a three-layer structure (Comparative Examples 1 to 3) were produced by the following methods.
- the compositions of the layers constituting each multilayer foam sheet are shown in Tables 1 and 2. Since the compositions and physical properties of the two layers (resin layer, surface layer and intermediate layer) provided on both sides of the foam layer of each multilayer foam sheet were the same as each other, only the composition and physical properties of one layer are shown in the table below.
- This kneaded product was adjusted to the extruded resin temperature shown in Table 3 (Example) and Table 4 (Comparative Example) with a first extruder to form a melt M2 for a foam layer.
- the polyethylene resin PE3 of the type and amount shown in Tables 1 and 2 the polymer type antistatic agent of the type and amount shown in Tables 1 and 2, and the polyalkylene glycol of the type and amount shown in Tables 1 and 2.
- the polyethylene resin PE4 of the type and amount shown in Tables 1 and 2 the polystyrene resin of the amount shown in Tables 1 and 2, the compatibilizer of the type and amount shown in Tables 1 and 2, in Table 2.
- Polyalkylene glycols of the type and amount shown (Comparative Examples 1 and 2 only), polymeric antistatic agents of the type and amount shown in Table 2 (Comparative Examples 1-3 only), and 50% by weight talc masterbatch (comparative).
- the blending amounts of the raw materials (excluding the volatile raw materials) shown in Tables 1 and 2 are the surface layer 4 (that is, the mixed resin R4) and the intermediate layer 3 (that is, that is, the mixed resin R4) constituting the obtained multilayer foamed sheet. It is the content in the antistatic resin composition R3).
- the foamable melt M2 for the foam layer, the melt M3 for the intermediate layer, and the melt M4 for the surface layer are placed into the annular die for coextrusion at the discharge amounts shown in Table 3 (Example) and Table 4 (Comparative Example), respectively. Introduced, the melt M3 was merged and laminated on both the inner and outer surfaces of the foamable melt M2, and the melt M4 was merged and laminated on both the inner and outer surfaces of each melt M3. The obtained laminate was co-extruded from an annular die, an intermediate layer was laminated and adhered to both the inner and outer surfaces of the foam layer, and a surface layer was laminated and adhered to each intermediate layer (intermediate layer in Comparative Examples 1 to 3).
- a tubular multi-layer foam (three-layer structure) was formed. While widening the extruded tubular multilayer foam, the basis weight (total basis weight) shown in Table 5 (Example) and Table 6 (Comparative Example) is obtained along with a columnar widening device having a diameter of 340 mm. It was picked up at the pick-up speed shown in Table 3 (Example) and Table 4 (Comparative Example). At the same time, the tubular laminated foam was cut open along the extrusion direction to obtain a multilayer foam sheet having a width of 1050 mm. The obtained multilayer foamed sheet was stored and cured in a curing room at 40 ° C. for 24 hours, and then subjected to the following physical characteristics measurement.
- the melting point of the polyethylene resin used in the examples and comparative examples is based on JIS K7121-1987, the condition (2) is adopted as the state adjustment of the test piece, and the melting peak temperature measured at a heating rate of 10 ° C./min. Is.
- the vicut softening temperature of the polystyrene resin was determined by JIS K7206 (the test load was the A method, and the heating rate of the heat transfer medium was 50 ⁇ 5 ° C./hour).
- the melt flow rate of the polyethylene resin and the polymer type antistatic agent was measured based on JIS K7210-1 (2014) under the conditions of 190 ° C. and a load of 2.16 kg.
- the melt flow rate of the polystyrene-based resin was measured based on JIS K7210-1 (2014) under the conditions of 200 ° C. and a load of 5.0 kg.
- the melt viscosity ( ⁇ ) was measured using Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a cylinder having a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 1.0 mm and a length of 10 mm were used. The cylinder and orifice were set at 190 ° C. for polyethylene resin and 200 ° C. for polystyrene resin. 15 g of the sample for measurement was put in the cylinder and left for 4 minutes. The obtained molten sample was extruded in a string shape from an orifice at a shear rate of 100 sec -1, and the melt viscosity was measured.
- the melt tension was measured by Capillograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd. Specifically, a cylinder having a cylinder diameter of 9.55 mm and a length of 350 mm and an orifice having a nozzle diameter of 2.095 mm and a length of 8.0 mm were used. The cylinder and orifice were set to a temperature of 190 ° C. The required amount of sample was placed in the cylinder and left for 4 minutes. The obtained molten sample was extruded from the orifice in a string shape at a piston speed of 10 mm / min.
- the extruded string is hung on a tension detection pulley with a diameter of 45 mm, and the string is increased with a take-up roller while increasing the take-up speed at a constant speed so that the take-up speed reaches from 0 m / min to 200 m / min in 4 minutes.
- the maximum value of the tension immediately before the string-shaped object was broken was measured by taking the object.
- the reason why the time required for the pick-up speed to reach 200 m / min from 0 m / min is set to 4 minutes is to suppress thermal deterioration of the resin and improve the reproducibility of the obtained value.
- the above operation was performed on 10 different samples. The three largest and three smallest values were removed from the 10 measurements obtained. The arithmetic mean of the remaining four measured values was taken as the melt tension (mN).
- the arithmetic mean value of the obtained thickness value was defined as the thickness [mm] of the multilayer foamed sheet. Moreover, the weight [g] of each test piece was measured. The measured weight was divided by the area of the test piece [m 2 ] (ie, the width of the sheet [m] ⁇ 100 mm (0.1 m)). The arithmetic mean value of the obtained five values was defined as the basis weight [g / m 2 ] of the multilayer foamed sheet. The apparent density [kg / m 3 ] of the multilayer foamed sheet is obtained by dividing the basis weight [g / m 2 ] of the foamed sheet obtained above by the thickness [m] of the foamed sheet obtained above (appropriate unit conversion). With).
- the surface resistivity was measured on both sides of the test piece (3 test pieces x both sides: 6 times in total), and the surface resistivity was obtained from the arithmetic mean value of the obtained measured values.
- a measuring device "TR8601" manufactured by Takeda Riken Kogyo Co., Ltd. was used. Based on the measured value of surface resistivity, the antistatic property of the multilayer foam sheet was evaluated according to the following criteria.
- C Surface resistivity is 1.0 ⁇ 10 Over 13
- the closed cell ratio of the multilayer foam sheet was measured by the above method.
- the true volume Vx of the multilayer foamed sheet (cut sample) was measured using an air comparative hydrometer 930 type of Toshiba Beckman Co., Ltd.
- the closed cell ratio S (%) was calculated by the following formula.
- As the cut sample for measurement a plurality of samples having a thickness of 25 mm ⁇ 25 mm ⁇ multi-layer foam sheet were cut out from the multi-layer foam sheet, and the obtained samples were stacked to obtain a cut sample for measurement of 25 mm ⁇ 25 mm ⁇ about 20 mm.
- Vx is the true volume (cm 3 ) of the cut sample measured by the above method and corresponds to the sum of the volume of the resin constituting the cut sample and the total volume of bubbles in the closed cell portion in the cut sample;
- Va is the apparent volume (cm 3 ) of the cut sample calculated from the outer dimensions of the cut sample used for the measurement;
- W is the total weight (g) of the cut sample used for the measurement;
- ⁇ is the density (g / cm 3 ) of the resin composition that constitutes the multi-layer foam sheet obtained by defoaming the multi-layer foam sheet.
- Glass contamination prevention test Glass for liquid crystal panels was used as the object to be packaged. 10 sheets of this glass and 11 multi-layer foam sheets were laminated to form a glass laminate, and "NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. was used to haze the glass laminate in the thickness direction (glass laminate direction). 1) was measured. A sample (foamed sheet obtained in Examples / Comparative Examples) was allowed to stand on each glass for 168 hours under the conditions of a temperature of 60 ° C. and a relative humidity of 90% while applying a load of a surface pressure of 50 g / cm 2 to bring them into close contact with each other. ..
- test piece was fixed to the bottom surface of a measuring jig having a bottom surface size of 50 mm ⁇ 50 mm and a weight of 125 g (5 g / cm 2 ), and a slide glass (manufactured by Matsunami Glass Industry Co., Ltd., product name “Standard Large White Edge Machining No. 2”). , Part number S91112 "). Then, the test piece was slid on the slide glass by aligning the extrusion direction of the multilayer foam sheet with the pulling direction of the measuring jig and pulling the measuring jig in the horizontal direction at a speed of 100 mm / min. The first maximum point load at this time was defined as the static friction force (N) in the test piece.
- N static friction force
- the static friction force on the mandrel contact surface side was obtained for 3 test pieces, and the static friction force on the opposite surface side to the mandrel contact surface was obtained for the remaining 3 pieces.
- Blocking prevention Two test pieces of multi-layer foam sheet cut out to a size of 40 mm ⁇ 150 mm in peel strength are stacked and stored at 50 ° C. for 168 hours under a load of 33 g / cm 2, and then the test speed is 100 mm / min. The peel strength (gf) between the test pieces was measured in. Based on the measured values, the blocking prevention property of the multilayer foam sheet was evaluated according to the following criteria. The lower the peel strength, the better the blocking prevention property. A: Peeling strength is less than 15gf B: Peeling strength is 15gf or more and less than 20gf C: Peeling strength is 20gf or more
- the amount of sagging is less than 10 mm
- Thickness recovery rate Thickness recovery rate
- a multilayer foamed sheet immediately after extrusion was used as a test piece, and the thickness (initial thickness) thereof was measured in the same manner as in the above method.
- C Thickness recovery rate is 10% or less
- Thickness recovery is an index of the thickness increase rate when the multilayer foamed sheet immediately after production is cured.
- the thickness of the multilayer foamed sheet is adjusted by the amount of foaming agent added, the take-up speed, and the like.
- the thickness of the multi-layer foamed sheet immediately after production decreases due to the dissipation of the foaming agent, but in the foamed sheet with excellent thickness recovery, air substitution progresses and the thickness increases by curing the foamed sheet, which is the target. It is possible to obtain a foamed sheet having a thickness to be increased. If the thickness recovery is low, the thickness does not increase even after curing, and it may be difficult to stably obtain the target thickness.
- a resin layer composed of a surface layer and an intermediate layer is laminated and adhered to both sides of the foam layer, and the surface layer / intermediate layer / foam layer / intermediate layer / surface is adhered. It has a five-layer structure, and the intermediate layer contains a polymer-type antistatic agent and the surface layer does not contain a polymer-type antistatic agent, so that it has excellent antistatic performance and can be used for objects to be packaged. The migration of low molecular weight components and the like was suppressed to an extremely small level. Further, since the surface layer contains the polystyrene-based resin in the specific amount, the handling property (slipperiness, blocking prevention property, stiffness strength) is excellent.
- Examples 6 to 9 are examples in which the blending amount of the polystyrene-based resin is increased as compared with Example 4.
- the obtained multilayer foamed sheet had a reduced closed cell ratio, and as a result, the stiffness strength was slightly lower than that of Example 4, but it could be used as a paper sheet.
- Example 9 is an example in which the polyethylene-based resin of the foam layer is LDPE2 in Example 8.
- the multilayer foamed sheet obtained in Example 8 had an excellent stiffness strength without lowering the closed cell ratio as in Example 8.
- Comparative Example 1 and Comparative Example 3 have a three-layer structure in which the surface layer is the same as that of the intermediate layers of Examples 4 and 5, respectively, without providing an intermediate layer and without adding a polystyrene resin to the surface layer.
- This is an example of forming a foam sheet.
- the obtained multilayer foamed sheet lacks glass contamination prevention property because a polymer-type antistatic agent is blended in the surface layer. Further, since the polystyrene-based resin was not blended in the surface layer, the slipperiness and the blocking prevention property were inferior.
- the multilayer foamed sheet of Comparative Example 1 in which an ionomer resin is blended as a polymer-type antistatic agent in the surface layer has reduced slipperiness.
- Comparative Example 2 is an example in which the surface layer is formed of 40 parts by weight of LDPE1, 50 parts by weight of talc masterbatch, and 10 parts by weight of a polymer-type antistatic agent instead of the compounding of the surface layer of Comparative Example 1. .. Since the obtained multilayer foamed sheet contains talc masterbatch, the slipperiness and blocking prevention property were improved as compared with Comparative Example 1, but the glass contamination prevention property was significantly reduced.
- Comparative Example 4 and Comparative Example 5 are examples of a multi-layer foam sheet having a five-layer structure in which the surface layer is formed only of LDPE1 and the intermediate layer and the foam layer are formed in the same manner as in Examples 4 and 1, respectively.
- the obtained multilayer foamed sheet was inferior in slipperiness and blocking prevention.
- the surface layer was formed of 40 parts by weight of LDPE1, 40 parts by weight of GPPS1 and 20 parts by weight of a compatibilizer, and the intermediate layer and the foamed layer were formed in the same manner as in Example 1, and the whole was 5 layers.
- LDPE1 low density polyethylene
- GPPS1 high density polyethylene
- a compatibilizer a compatibilizer for polystyrene resin
- the intermediate layer and the foamed layer were formed in the same manner as in Example 1, and the whole was 5 layers.
- the closed cell ratio was remarkably lowered, and the stiffness strength was greatly lowered.
- the thickness recovery was also inferior.
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Abstract
Description
ここで、滑り性に優れるとは、発泡シートと被包装物との間に生じる摩擦力が小さく、例えば発泡シートをガラス板用間紙としてガラス間に介在させて包装する際に、発泡シートを搬送し、ガラス板に重ねる作業が円滑に行われることをいう。
[1]発泡層と、該発泡層の両面の各々に積層された樹脂層とを有するポリエチレン系樹脂多層発泡シートであって、
該樹脂層は該多層発泡シートの最表面側に位置する表面層と、該表面層と該発泡層との間に位置する中間層とを含む多層構造を有し、
該発泡層はポリエチレン系樹脂PE2を含み、
該中間層はポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物から構成され、
該表面層はポリエチレン系樹脂PE4とポリスチレン系樹脂とを含む混合樹脂から構成され、
該混合樹脂は高分子型帯電防止剤を実質的に含まず、
該混合樹脂中のポリスチレン系樹脂の含有量が3重量%以上35重量%以下である、
該ポリエチレン系樹脂多層発泡シートの表面抵抗率が1×1013Ω以下である、ポリエチレン系樹脂多層発泡シート。
[2]前記混合樹脂中の、前記ポリエチレン系樹脂PE4に対する前記ポリスチレン系樹脂の重量比が0.03以上0.4以下である、前記1に記載のポリエチレン系多層発泡シート。
[3]前記混合樹脂中のポリスチレン系樹脂の含有量が3重量%以上12重量%以下である、前記1又は2に記載のポリエチレン系樹脂多層発泡シート。
[4]前記帯電防止性混合物中の前記高分子型帯電防止剤の含有量が、前記ポリエチレン系樹脂PE3と該高分子型帯電防止剤との合計重量に対して5重量%以上25重量%以下である、前記1~3のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[5]前記高分子型帯電防止剤がアイオノマー樹脂である、前記1~4のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[6]前記帯電防止性混合物がポリアルキレングリコールを含み、該ポリアルキレングリコールの含有量がポリエチレン系樹脂PE3と高分子型帯電防止剤の合計100重量部に対して0.3~6重量部である、前記5に記載のポリエチレン系樹脂多層発泡シート。
[7]前記中間層の1m2あたりの高分子型帯電防止剤の含有量が0.15g以上2g以下であり、該高分子型帯電防止剤の含有量A〔g/m2〕に対する前記表面層の坪量B4〔g/m2〕の比(B4/A)が1以上30以下である、前記1~6のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[8]前記表面層の坪量B4が0.5g/m2以上10g/m2以下である、、前記1~7のいずれか一項に記載のポリエチレン系樹脂多層発泡シー
[9]前記ポリエチレン系樹脂PE2が低密度ポリエチレンであり、前記ポリエチレン系樹脂PE3が低密度ポリエチレンである、前記1~8のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[10]前記ポリエチレン系樹脂PE2の温度190℃、荷重2.16kgにおけるメルトフローレイトが0.1g/10min以上1.5g/10min以下である、前記1~9のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[11]40%以上の独立気泡率を有する、前記1~10のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
[12]前記1~11のいずれか一項に記載のポリエチレン系樹脂多層発泡シートのガラス板用間紙としての使用を提供する。
更なるアスペクトにおいて、本発明は
[13]表面抵抗率が1×1013Ω以下であり、かつ、第1表面層と、第1中間層と、発泡層と、第2中間層と、第2表面層とがこの順に重ねられ積層された多層構造を有するポリエチレン系樹脂多層発泡シートの製造方法であって、該方法は、
ポリエチレン系樹脂PE2と物理発泡剤とを含む、該発泡層形成用の発泡性溶融物M2と、ポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物から構成される、該第1及び第2中間層形成用の溶融物M3と、ポリエチレン系樹脂PE4とポリスチレン系樹脂とを含み、高分子型帯電防止剤を実質的に含まない混合樹脂から構成される、該第1及び第2表面層形成用の溶融物M4とを用意する工程と、
ダイ内で該溶融物M4、M3、M2、M3及びM4をこの順に積層させて積層物を形成する工程と、
該積層物を該ダイから共押出して該発泡性溶融物M2を発泡させる工程を含み、
ここで該ポリスチレン系樹脂が該混合樹脂組成物中に該混合樹脂組成物の重量に基づき3重量%以上35重量%以下の量で含有されている、ポリエチレン系樹脂多層発泡シートの製造方法。
を提供する。
図1に示すように、本発明のポリエチレン系樹脂多層発泡シート1(以下、多層発泡シート、または単に発泡シートともいう。)は、発泡層2と、該発泡層2の両面の各々に設けられた樹脂層5とを有している。該樹脂層5の各々は、多層発泡シート1の最表面側に位置する表面層4(以下単に表面層ということがある)と該表面層4と該発泡層2との間に位置した中間層3とを含む多層構造を有している。即ち、図1に具体的に示した多層発泡シート1は、樹脂層5(表面層4/中間層3)/発泡層2/樹脂層5(中間層3/表面層4)の5層構造を有している。なお、本発明の発泡シート1はこのような5層構造に限られない。本発明の趣旨、効果を妨げない限り、一方又は双方の樹脂層と発泡層との間に樹脂などのポリマーからなる追加の層を設けることにより、6層構造又は7層構造とすることができる(図示せず。)。
以下の記載は、簡潔にするため、一対の樹脂層5の一方についてなされているが、該記載は他方の樹脂層にも当てはまる。以下に詳説する要件が満たされる限り、二つの樹脂層5は同一もしくは異なる構成を有することができることに注意すべきである。例えば、二つの表面層4の一方の表面層の樹脂成分、添加物等の種類や量および坪量等の物性値は、他方の表面層のものと同一または異なっていても良い。
なお、本明細書において、数値範囲「A~B」は、下限「A」および上限「B」を含むべく意図されており、従って「A以上かつB以下」と同義である。
該発泡層2は、ポリエチレン系樹脂PE2を含有する基材ポリマーから構成され、該中間層3はポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物(以下、単に樹脂組成物R3ともいう。)から構成され、該表面層4はポリエチレン系樹脂PE4とポリスチレン系樹脂とを含む混合樹脂(以下、混合樹脂R4ともいう。)から構成されている。
なお、本明細書におけるポリエチレン系樹脂のメルトフローレイト(MFR)は、JIS K 7210-1(2014)に基づき、190℃、荷重2.16kgの条件で測定されるメルトマスフローレイトを意味する。
該中間層は、ポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物R3から構成されている。すなわち、該中間層はポリエチレン系樹脂PE3と高分子型帯電防止剤とを包含する。該ポリエチレン系樹脂PE3は該中間層の主成分である。具体的には、ポリエチレン系樹脂の含有量が中間層の重量(すなわち帯電防止性樹脂組成物R3の重量)に基づき50重量%以上であることが好ましく、より好ましくは60重量%以上であり、さらに好ましくは70重量%以上である。
該アイオノマー樹脂は、表面抵抗率が小さく、多層発泡シートに良好な帯電防止性能を付与することができることに加え、低分子量成分の含有量が少ないため、被包装物への低分子量成分の移行による、被包装物の汚染をより抑制することができる。
なお、アイオノマー樹脂の表面抵抗率は、前記多層発泡シートの表面抵抗率の測定と同様の方法により測定することができる。
該含有量Aが0.15g/m2以上であれば、多層発泡シートの帯電防止性能を、むらなく安定して発現させることができる。かかる理由から、該含有量Aの下限は、0.18g/m2であることがより好ましく、更に好ましくは0.19g/m2であり、特に好ましくは0.2g/m2である。一方、該含有量Aが2g/m2以下であれば、中間層3に含まれる高分子型帯電防止剤中の低分子量成分等の有機物質が表面層4の表面にブリードアウトしにくくなる。かかる理由から、該含有量Aの上限は、1.5g/m2であることがより好ましく、更に好ましくは1.0g/m2であり、特に好ましくは0.8g/m2である。含有量Aの値を前記範囲としつつ、十分な帯電防止効果を発現させるためには、中間層3は非発泡であることが好ましい。
なお、該含有量Aは、発泡層2の両面に設けられた一対の中間層3の一つ当たりの値である。
該比B4/Aは、中間層3に含まれる高分子型帯電防止剤の単位面積当たりの重量に対する、表面層4の坪量B4の比を表す指標である。高分子型帯電防止剤に含まれる低分子量成分が被包装物へ移行することを抑制するためには、高分子量型帯電防止剤の含有量Aを少なくするか、または表面層4の坪量B4を多くする(表面層4の厚みを厚くする)ことが好ましい。一方、発泡シートが十分な帯電防止性能を発現するためには、高分子量型帯電防止剤の含有量Aを多くするか、または表面層の坪量B4を少なくする(表面層の厚みを薄くする)ことが好ましい。本発明の発泡シートにおいて、低分子量成分の移行を抑制し、かつ十分な帯電防止性能を発現するためには、該比B4/Aが前記範囲であることが好ましい。
帯電防止性と汚染防止性とをよりバランスよく両立させる観点からは、該比B4/Aの下限は、2であることが好ましく、より好ましくは3であり、さらに好ましくは4である。該比の上限は、25であることが好ましく、より好ましくは20であり、さらに好ましくは15であり、特に好ましくは10である。
また、中間層がポリアルキレングリコールを含有していることで、帯電防止性能の湿度依存性が低減され、湿度が低い条件下においても良好な帯電防止性能を発揮する多層発泡シートを得ることができる。
これらの中でも、安定してポリエチレン系樹脂中にアイオノマー樹脂を分散させることができると共に、帯電防止性能を高めつつ、帯電防止性能の湿度依存性をより低減できることから、ポリエチレングリコールを用いることが好ましい。
HLB=20×Mh/Mw
ここで、Mhは親水性化合物の親水性部分の分子量、Mwは親水性化合物全体の分子量である。
なお、該帯電防止性樹脂組成物R3、すなわち中間層は、ポリスチレン系樹脂を実質的に含有しないことが好ましい。具体的には、該帯電防止性樹脂組成物R3中のポリスチレン系樹脂の含有量が5重量%以下であることが好ましく、3重量%以下であることがより好ましく、2重量部以下であることが更に好ましく、該含有量が0であることが特に好ましい。該帯電防止性樹脂組成物R3中のポリスチレン系樹脂の含有量を少なくすることで多層発泡シートの独立気泡率をより高めることができ、コシ強度や緩衝性をより高めることができる。また、リサイクル性を高めることができる。
該表面層は、ポリエチレン系樹脂PE4とポリスチレン系樹脂を含む混合樹脂R4から構成されている。すなわち、該表面層は、ポリエチレン系樹脂PE4とポリスチレン系樹脂を含む。該ポリエチレン系樹脂PE4は該表面層の主成分である。具体的には、ポリエチレン系樹脂PE4の含有量が表面層の重量(すなわち樹脂混合物R4の重量)に基づき50重量%以上であることが好ましく、より好ましくは60重量%以上であり、さらに好ましくは70重量%以上である。該ポリエチレン系樹脂PE4としては前記ポリエチレン系樹脂PE3として例示したポリエチレン系樹脂を用いることができる。該ポリエチレン系樹脂PE3と同じ種類のものを用いると、表面層4と中間層3との接着性に優れる樹脂層5になるので好ましい。具体的には、ポリエチレン系樹脂PE4は低密度ポリエチレンを50重量%以上の量で含むことが好ましい。また、ポリエチレン系樹脂PE4として直鎖状低密度ポリエチレンを用いると、低分子量成分の移行量をより抑制することができる。但し、異なる種類のポリエチレン系樹脂を用いることもできる。
さらに、本発明の多層発泡シートにおいて、前記表面層は、高分子型帯電防止剤以外の他の帯電防止剤も実質的に含有しないことが好ましい。高分子型帯電防止剤以外の他の帯電防止剤としては、界面活性剤が例示される。
一方、ポリスチレン系樹脂の含有量が35重量%超であると、発泡シートのコシ強度が低下するおそれがある。また、発泡シートが本来有する優れた緩衝性を維持できないおそれがある。発泡シートの優れた緩衝性を維持しつつコシ強度を向上させるためには、混合樹脂R4中のポリスチレン系樹脂の含有量は30重量%以下であることが好ましく、25重量%以下であることがより好ましく、20重量%以下であることが更に好ましく、12重量%以下であることが特に好ましく、8重量%以下であることが最も好ましい。
なお、上述の坪量は、発泡層2の両面の一方に設けられた樹脂層5,表面層4および中間層3の坪量である。二つの樹脂層、二つの表面層及び二つの表面層において、一方の層の坪量は他方の相応する層の坪量と好ましくは等しいが、それらは互いに異なっても良い。
該発泡シートの見掛け密度が前記範囲であれば、高いコシ強度等の機械的物性と軽量性と緩衝性とのバランスに優れた発泡シートとなる。かかる観点から、該見掛け密度の下限はより好ましくは15kg/m3、さらに好ましくは20kg/m3である。一方、該見掛け密度の上限は、より好ましくは200kg/m3、さらに好ましくは100kg/m3である。
まず、多層発泡シートを、垂直(すなわち厚み方向)に、その幅方向(すなわち押出方向と直角な方向)に沿って切り出し、シート全幅[mm]に等しい長さと100mmの幅を有する矩形状の試験片を得る。同様な操作を発泡シートの異なる位置で繰り返し、合計5つの試験片を得る。各々の試験片の厚みを発泡シートの幅方向に1cm間隔ごとに測定する。得られた厚み値の算術平均値が多層発泡シートの厚み[mm]である。また、各々の試験片の重量[g]を測定する。測定した重量を試験片の面積[m2](すなわち、シートの幅[m]×100mm(0.1m))で除す。得られた5つの値の算術平均値が多層発泡シートの坪量[g/m2]である。多層発泡シートの見掛け密度[kg/m3]は、上記で得た発泡シートの坪量[g/m2]を上記で得た発泡シートの厚み[m]で除すこと(適切な単位変換とともに)により求められる。
B3=〔1000×X/(L×W)〕
ここで、Xは中間層の吐出量[kg/時]、Lは発泡シートの引取速度[m/時]、Wは発泡シートの幅[m]である。
表面層の坪量B4は次式により計算できる。
B4=〔1000×Y/(L×W)〕
ここで、Yは表面層の吐出量[kg/時]、LとWは上に定義したとおりである。
特に、発泡シートの坪量が25~50g/m2の範囲内である場合には、良好なコシ強度を維持する観点から、独立気泡率は40%以上であることが好ましい。
ここで、
Vxは前記方法で測定されたカットサンプルの真の体積(cm3)であり、カットサンプルを構成する樹脂の容積と、カットサンプル内の独立気泡部分の気泡全容積との和に相当する;
Vaは測定に使用されたカットサンプルの外寸から計算されたカットサンプルの見かけ上の体積(cm3)である;
Wは測定に使用されたカットサンプル全重量(g)である;および
ρは多層発泡シートを脱泡して求められる多層発泡シートを構成する樹脂組成物の密度(g/cm3)である。
本発明の多層発泡シートは、公知の方法で製造することができる。その代表的な方法としては、例えば、共押出用ダイ内で、発泡層形成用発泡性溶融物の両面に中間層形成用溶融物及び表面層形成用溶融物を、この順で積層し、これらを共押出するとともに、発泡性溶融物を発泡させて、多層発泡シートを製造する方法が好ましく挙げられる。但し、中間層形成用溶融物と表面層形成用溶融物とを共押出用ダイを用いて積層して多層構造の樹脂層を得、この樹脂層を別工程で作製された発泡シート(発泡層)の両面の各々に中間層を発泡シート側に向けて積層することによっても、多層発泡シートを製造することができる。
まず、前記ポリエチレン系樹脂PE2と、必要に応じて添加される気泡調整剤などの添加剤とを押出機に供給し、加熱混練してから、押出機内に物理発泡剤を圧入し、さらに混練して発泡層形成用発泡性溶融物M2を得る。同時に、前記ポリエチレン系樹脂PE3と、前記高分子型帯電防止剤と、必要に応じて添加されるポリエチレングリコールなどを別の押出機に供給し、加熱混練して中間層形成用溶融物M3を得る。さらに、前記ポリエチレン系樹脂PE4と、ポリスチレン系樹脂(C)等とを更なる別の押出機に供給し、加熱混練して表面層形成用溶融物M4を得る。
得られた、発泡性溶融物M2と溶融物M3と溶融物M4とを共押出用環状ダイに導入し、筒状に流動する発泡性溶融物M2の両面に中間層用溶融物M3を積層し、さらにその両面に表面層用溶融物M4を積層し、大気中に押出発泡させて、筒状発泡体を形成する。該筒状発泡体をマンドレル等の拡幅装置に沿わせて引取りながら、切り開くことにより多層発泡シートが得られる。
なお、前に述べたとおり、二つの樹脂層5は同一もしくは異なる構成を有することができる。従って、二つの中間層3の一方の中間層用の溶融物M3の組成(樹脂成分、添加物等の種類や量)は、他方の中間層のものと同一または異なっていても良い。同様に、二つの表面層4の一方の表面層用の溶融物M4の組成(樹脂成分、添加物等の種類や量)は、他方の表面層のものと同一または異なっていても良い。
本発明の発泡シートを積層共押出法により製造する場合、表面層用溶融物M4が、ポリスチレン系樹脂を含有しているため、溶融粘度が高くなり、ダイ内におけるせん断発熱が大きくなる傾向がある。その結果、せん断発熱により発泡層の独立気泡率や厚み回復性が低下しやすくなるおそれがある。一方、発泡層のポリエチレン系樹脂PE2のメルトフローレイト(MFR)が0.1~1.5g/10minであれば、発泡性溶融物M2の溶融粘度が大きくなるため、せん断発熱の影響を緩和することができる。また、ポリエチレン系樹脂PE2が上記範囲のMFRを有することにより、気泡構造が維持されやすいと考えられる。
なお、一般的に、ポリエチレン系樹脂発泡シートの厚みは、製造直後に気泡内の空気が抜けて減少する傾向がある。通常、この厚み減少は、発泡シートを所定温度で所定時間静置(養生)することにより回復させることができるが、何らかの理由で養生しても厚みが増えないことがある。この厚みが回復しない現象を厚み回復性低下という。回復性低下の原因のひとつとしては、独立気泡率の低下が考えられる。
なお、気泡調整剤の添加量は、基材ポリマー100重量部当たり好ましくは0.01~3重量部、より好ましくは0.03~1重量部である。
(1)略称「LDPE1」株式会社NUC製低密度ポリエチレン「NUC8321」(密度922kg/m3、MFR2.4g/10min、融点112℃、溶融粘度818Pa/s(測定温度190℃)、溶融張力64mN)
(2)略称「LDPE2」株式会社NUC製低密度ポリエチレン「NS-1s」(密度922kg/m3、MFR0.4g/10min、融点110℃、溶融粘度1468Pa/s(測定温度190℃)、溶融張力199mN)
(1)略称「GPPS1」:PSジャパン株式会社製汎用ポリスチレン「680」(密度1050kg/m3、MFR7.0g/10min、ビカット軟化温度98℃、溶融粘度927Pa/s(測定温度200℃)、溶融張力73mN)
(1)略称「LMP」:三洋化成工業株式会社製ポリエーテル-ポリオレフィンブロック共重合体「ペレクトロンLMP」(MFR17g/10min、融点117℃、表面抵抗率:2.0×107Ω)
(2)略称「SD100」:三井・デュポンポリケミカル株式会社製エチレン系カリウムアイオノマー樹脂「エンティラSD100」(MFR5g/10min、融点92℃、表面抵抗率:1.0×107Ω)
(1)略称「SEBS1」旭化成社製水添スチレン系熱可塑性エラストマー「タフテックH1041」、ゴム分率70%
以下の押出機とダイを備えた多層発泡シート製造装置を用いた。
発泡層形成用押出機:バレル内径115mmのシングル押出機(第一押出機)
中間層形成用押出機:バレル内径65mmの押出機(第二押出機)
表面層形成用押出機:バレル内径50mmの押出機(第三押出機)
ダイ:出口直径96mmの共押出用環状ダイ
樹脂層(表面層/中間層)/発泡層/樹脂層(中間層/表面層)の5層構造の発泡シート(実施例1~9および比較例4~6)および表面層/発泡層/表面層の3層構造の発泡シート(比較例1~3)を以下の方法で作製した。各多層発泡シートを構成する層の組成を表1及び2に示す。各多層発泡シートの発泡層の両面に設けた2つの層(樹脂層、表面層及び中間層)の組成および物性は互いに同一としたため、以下の表では一方の層の組成および物性のみ示した。表1及び表2において、「%」及び「部」はそれぞれ「重量%」及び「重量部」である。 表1(実施例)および表2(比較例)に示す種類および配合量のポリエチレン系樹脂PE2と、100重量部のポリエチレン系樹脂PE2に対して2重量部の気泡調整剤としてのタルクのマスターバッチとを第一押出機に供給し、これらを約200℃で混錬した後、物理発泡剤として表1および表2に示す量のイソブタンを圧入して、さらに混錬した。この混錬物を第一押出機にて表3(実施例)および表4(比較例)に示す押出樹脂温度に調整して発泡層用溶融物M2を形成した。
同時に、表1および表2に示す種類および量のポリエチレン系樹脂PE3、表1および表2に示す種類および量の高分子型帯電防止剤、表1および表2に示す種類および量のポリアルキレングリコールを第二押出機に供給し、これらを約200℃で混錬した後、揮発性可塑剤として表1および表2に示す量の混合ブタン(ノルマルブタン/イソブタン=65重量%/35重量%)を圧入して、さらに混錬し、表3および表4に示す押出樹脂温度に調整して中間層用溶融物M3を形成した。
なお、表1および表2に示される各原料(揮発性原料を除く)の配合量は、得られた多層発泡シートを構成する各表面層4(すなわち混合樹脂R4)、および中間層3(すなわち帯電防止性樹脂組成物R3)中の含有量となる。
(1)多層発泡シートの見掛け密度、坪量および厚み
多層発泡シートの見掛け密度、坪量および厚みは前述した方法により求めた。
まず、多層発泡シートを、垂直(すなわち厚み方向)に、その幅方向(すなわち押出方向と直角な方向)に沿って切り出し、シート全幅[mm]に等しい長さと100mmの幅を有する矩形状の試験片を得た。同様な操作を発泡シートの異なる位置で繰り返し、合計5つの試験片を得た。各々の試験片の厚みを発泡シートの幅方向に1cm間隔ごとに測定した。得られた厚み値の算術平均値を多層発泡シートの厚み[mm]とした。また、各々の試験片の重量[g]を測定した。測定した重量を試験片の面積[m2](すなわち、シートの幅[m]×100mm(0.1m))で除した。得られた5つの値の算術平均値を多層発泡シートの坪量[g/m2]とした。多層発泡シートの見掛け密度[kg/m3]は、上記で得た発泡シートの坪量[g/m2]を上記で得た発泡シートの厚み[m]で除すこと(適切な単位変換とともに)により求めた。
表面層と中間層の各々の吐出量(すなわち、表面層用溶融物M4と中間層用溶融物M3の吐出量)から、表面層及び中間層の坪量を求めた。具体的には、中間層の片面当たりの吐出量X[kg/時]、表面層の片面当たりの吐出量Y[kg/時]、多層発泡シートの幅W[m]、引取速度L[m/時]から下記式によりそれぞれの坪量[g/m2]を求めた。
また、中間層と表面層との合計を樹脂層の坪量とした。多層発泡シートの一方の面側と他方の面側の表面層及び中間層の坪量が同一となる条件で、多層発泡シートを製造したため、表5、表6中には、片面側のみの坪量を示した。
中間層の坪量B3[g/m2]=〔1000×X/(L×W)〕
表面層の坪量B4[g/m2]=〔1000×Y/(L×W)〕
多層発泡シートの幅方向中央部及び両端部付近から、縦100mm×横100mm×厚み:多層発泡シートの厚みのままの試験片を3片切り出した。各試験片を温度23℃、相対湿度50%の雰囲気下に24時間放置した。次いで、JIS K6271-2001に準じて23℃、相対湿度50%の雰囲気下で試験片に500Vの電圧を印加し、印加1分後の試験片の表面抵抗率を測定した。なお、試験片の両面に対して表面抵抗率の測定を行ない(試験片3片×両面:計6回)、得られた測定値の算術平均値から表面抵抗率を求めた。測定装置として、タケダ理研工業株式会社製「TR8601」を用いた。
表面抵抗率の測定値に基づき、多層発泡シートの帯電防止性を以下の基準で評価した。
A:表面抵抗率が、1.0×1012Ω以下
B:表面抵抗率が、1.0×1012Ωを超え、1.0×1013Ω以下
C:表面抵抗率が、1.0×1013を超える
まず、ASTM-D2856-70の手順Cに従い、東芝ベックマン株式会社の空気比較式比重計930型を使用して多層発泡シート(カットサンプル)の真の体積Vxを測定した。得られたVxを用い、下記式により独立気泡率S(%)を計算した。なお、測定用カットサンプルは、多層発泡シートから複数の25mm×25mm×多層発泡シート厚みのサンプルを切り出し、得られたサンプルを重ねて、25mm×25mm×約20mmの測定用カットサンプルとした。
ここで、
Vxは前記方法で測定されたカットサンプルの真の体積(cm3)であり、カットサンプルを構成する樹脂の容積と、カットサンプル内の独立気泡部分の気泡全容積との和に相当する;
Vaは測定に使用されたカットサンプルの外寸から計算されたカットサンプルの見かけ上の体積(cm3)である;
Wは測定に使用されたカットサンプル全重量(g)である;および
ρは多層発泡シートを脱泡して求められる多層発泡シートを構成する樹脂組成物の密度(g/cm3)である。
被包装物として液晶パネル用ガラスを用いた。このガラスを10枚と多層発泡シート11枚を重ねてガラス積層体とし、日本電飾工業(株)社製の「NDH2000」を用いて、ガラス積層体の厚み方向(ガラス積層方向)に対するヘーズ(1)を測定した。それぞれのガラスにサンプル(実施例・比較例で得られた発泡シート)を面圧50g/cm2の荷重をかけて密着させつつ温度60℃、相対湿度90%の条件下で168時間静置した。その後、サンプルをガラスから取り除き、ガラスを10枚重ねて、ガラス積層体のヘーズ(2)をヘーズ(1)と同様に測定した。ヘーズ(2)の値からヘーズ(1)の値を引き算してヘーズの変化量を求め(試験後のガラスヘーズ(%)-試験前のガラスヘーズ(%))、以下の基準で多層発泡シートの汚染防止性を評価した。ヘーズの変化量が小さいほど、ガラスへの多層発泡シートの高分子型帯電防止剤に含まれる低分子量成分の移行が少ないことを意味する。
A:ヘーズ変化量が1未満
B:ヘーズ変化量が1以上1.5未満
C:ヘーズ変化量が1.5以上2.5未満
D:ヘーズ変化量が2.5以上
静摩擦力は、JISK7125:1999に準拠した方法により測定した。まず、多層発泡シートの無作為に選択した箇所から、試験片の1辺を多層発泡シートの押出方向に一致させて50mm×50mmの正方形状の試験片を6片切り出した。次に、試験片を23℃、湿度50%の雰囲気下に24時間載置して試験片の状態調節を行なった。その後、試験片を底面サイズ50mm×50mm、重量125g(5g/cm2)の測定用治具の底面に固定し、スライドガラス(松浪硝子工業株式会社製、品名「標準大型白縁磨No.2」、品番S9112」)上に置いた。そして、多層発泡シートの押出方向と測定用治具の引張方向とを合わせて、測定用治具を100mm/分の速度で水平方向に引張ることにより、試験片をスライドガラス上で滑らせた。このときの第一極大点荷重を試験片における静摩擦力(N)とした。6片の試験片のうち3片の試験片についてはマンドレル当接面側の静摩擦力を求め、残りの3片についてはマンドレル当接面とは反対面側の静摩擦力を求めた。各試験片における静摩擦力の算術平均値(n=6)を多層発泡シートの低荷重下における静摩擦力(N)とした。静摩擦力が小さいほど、滑り性に優れる。
静摩擦力の測定値に基づき、多層発泡シートの滑り性を以下の基準で評価した。
A:静摩擦力が2N未満
B:静摩擦力が2N以上2.5N未満
C:静摩擦力が2.5N以上3N未満
D:静摩擦力が3N以上
40mm×150mmのサイズに切り出した多層発泡シートの試験片を2枚重ねて、荷重33g/cm2をかけて50℃で168hr保管した後、試験速度100mm/minで試験片同士の剥離強度(gf)を測定した。測定値に基づき、多層発泡シートのブロッキング防止性を以下の基準で評価した。剥離強度が低いほど、ブロッキング防止性に優れる。
A:剥離強度が15gf未満
B:剥離強度が15gf以上20gf未満
C:剥離強度が20gf以上
得られた多層発泡シートの押出方向と試験片の長さ方向とを一致させて、多層発泡シートの無作為に選択した10箇所から幅200mm×長さ200mmの測定用試験片をそれぞれ10枚切り出した。得られた試験片の各々を水平な土台上に土台の端から水平方向に試験片の長さ方向を100mm突出させて片持ち状態で固定して、試験片突出部を自重で垂下させた。土台上面と垂れ下がった試験片の先端部との間の垂直方向の距離を測定した。この測定を各試験片に対して行い、得られた10の測定値の算術平均値を多層発泡シートの垂れ下がり量(mm)とした。垂れ下がり量が少ないほどコシ強度が高い。
A:垂れ下がり量が10mm未満
B:垂れ下がり量が10mm以上15mm未満
C:垂れ下がり量が15mm以上20mm未満
D:垂れ下がり量が20mm以上
まず、押出直後の多層発泡シートを試験片とし、その厚み(初期厚み)を前記方法と同様に測定した。次に、該多層発泡シートを40℃の養生室に入れ、24時間保管・養生し、養生直後の多層発泡シートの厚み(養生後の厚み)を測定し、次式により厚み回復率を求めた。
厚み回復率(%)=((養生後の厚み-初期厚み)/初期厚み))×100
得られた回復率に基づき多層発泡シートの厚み回復性を以下の基準で評価した。
A:厚み回復率が20%以上
B:厚み回復率が10%超20%未満
C:厚み回復率が10%以下
2 発泡層
3 中間層
4 表面層
5 樹脂層
Claims (13)
- 発泡層と、該発泡層の両面の各々に積層された樹脂層とを有するポリエチレン系樹脂多層発泡シートであって、
該樹脂層は該多層発泡シートの最表面側に位置する表面層と、該表面層と該発泡層との間に位置する中間層とを含む多層構造を有し、
該発泡層はポリエチレン系樹脂PE2を含み、
該中間層はポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物から構成され、
該表面層はポリエチレン系樹脂PE4とポリスチレン系樹脂とを含む混合樹脂から構成され、
該混合樹脂は高分子型帯電防止剤を実質的に含まず、
該混合樹脂中のポリスチレン系樹脂の含有量が3重量%以上35重量%以下であり、
該ポリエチレン系樹脂多層発泡シートの表面抵抗率が1×1013Ω以下である、ポリエチレン系樹脂多層発泡シート。 - 前記混合樹脂中の、前記ポリエチレン系樹脂PE4に対する前記ポリスチレン系樹脂の重量比が0.03以上0.4以下である、請求項1に記載のポリエチレン系樹脂多層発泡シート。
- 前記混合樹脂中のポリスチレン系樹脂の含有量が3重量%以上12重量%以下である、請求項1又は2に記載のポリエチレン系樹脂多層発泡シート。
- 前記帯電防止性樹脂組成物中の前記高分子型帯電防止剤の含有量が、前記ポリエチレン系樹脂PE3と該高分子型帯電防止剤との合計重量に対して5重量%以上25重量%以下である、請求項1~3のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 前記高分子型帯電防止剤がアイオノマー樹脂である、請求項1~4のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 前記帯電防止性樹脂組成物がポリアルキレングリコールを含み、該ポリアルキレングリコールの含有量がポリエチレン系樹脂PE3と高分子型帯電防止剤の合計100重量部に対して0.3~6重量部である、請求項5に記載のポリエチレン系樹脂多層発泡シート。
- 前記中間層の1m2あたりの高分子型帯電防止剤の含有量が0.15g以上2g以下であり、該高分子型帯電防止剤の含有量A〔g/m2〕に対する前記表面層の坪量B4〔g/m2〕の比(B4/A)が1以上30以下である、請求項1~6のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 前記表面層の坪量B4が0.5g/m2以上10g/m2以下である、請求項1~7のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 前記ポリエチレン系樹脂PE2が低密度ポリエチレンであり、前記ポリエチレン系樹脂PE3が低密度ポリエチレンである、請求項1~8のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 前記ポリエチレン系樹脂PE2の温度190℃、荷重2.16kgにおけるメルトフローレイトが0.1g/10min以上1.5g/10min以下である、請求項1~9のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 40%以上の独立気泡率を有する、請求項1~10のいずれか一項に記載のポリエチレン系樹脂多層発泡シート。
- 請求項1~11のいずれか一項に記載のポリエチレン系樹脂多層発泡シートのガラス板用間紙としての使用。
- 表面抵抗率が1×1013Ω以下であり、かつ、第1表面層と、第1中間層と、発泡層と、第2中間層と、第2表面層とがこの順に重ねられ積層された多層構造を有するポリエチレン系樹脂多層発泡シートの製造方法であって、該方法は、
ポリエチレン系樹脂PE2と物理発泡剤とを含む、該発泡層形成用の発泡性溶融物M2と、ポリエチレン系樹脂PE3と高分子型帯電防止剤とを含む帯電防止性樹脂組成物から構成される、該第1及び第2中間層形成用の溶融物M3と、ポリエチレン系樹脂PE4とポリスチレン系樹脂とを含み、高分子型帯電防止剤を実質的に含まない混合樹脂から構成される、該第1及び第2表面層形成用の溶融物M4とを用意する工程と、
ダイ内で該溶融物M4、M3、M2、M3及びM4をこの順に積層させて積層物を形成する工程と、
該積層物を該ダイから共押出して該発泡性溶融物M2を発泡させる工程を含み、
ここで該ポリスチレン系樹脂が該混合樹脂組成物中に該混合樹脂組成物の重量に基づき3重量%以上35重量%以下の量で含有されている、ポリエチレン系樹脂多層発泡シートの製造方法。
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- 2021-05-28 EP EP21818062.8A patent/EP4163103A1/en active Pending
- 2021-05-28 CN CN202180040447.XA patent/CN115666926A/zh active Pending
- 2021-05-28 WO PCT/JP2021/020387 patent/WO2021246309A1/ja active Application Filing
- 2021-05-28 KR KR1020227045905A patent/KR20230021019A/ko active Search and Examination
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JP2008308695A (ja) | 2002-10-08 | 2008-12-25 | Jsp Corp | 発泡シート |
JP2012035624A (ja) * | 2010-07-12 | 2012-02-23 | Mitsui Chemicals Tohcello Inc | 積層フィルム |
JP2014237770A (ja) * | 2013-06-07 | 2014-12-18 | 株式会社ジェイエスピー | ポリエチレン系樹脂多層発泡シート |
US20160311202A1 (en) | 2015-04-27 | 2016-10-27 | Jsp Corporation | Laminated foam interleaf sheet for glass plates |
JP2016204227A (ja) * | 2015-04-27 | 2016-12-08 | 株式会社ジェイエスピー | ガラス板用間紙 |
JP2019042988A (ja) * | 2017-08-31 | 2019-03-22 | 株式会社ジェイエスピー | 間紙 |
JP2020090026A (ja) * | 2018-12-05 | 2020-06-11 | 株式会社ジェイエスピー | ポリスチレン系樹脂多層発泡シートとそれを用いた間紙 |
JP2020138357A (ja) * | 2019-02-27 | 2020-09-03 | 株式会社ジェイエスピー | 多層発泡シート |
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JPWO2021246309A1 (ja) | 2021-12-09 |
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KR20230021019A (ko) | 2023-02-13 |
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