JP2013112724A - Noncrosslinked polyethylene extruded foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncrosslinked polyethylene extruded foam having high expansion ratio, and excellent mechanical strength and secondary processability.SOLUTION: The noncrosslinked polyethylene extruded foam comprises an ethylene-α-olefin copolymer having ≥0.1 g/10 and <50 g/10 min of a melt flow rate, ≥40 mN of a melt tension at 160°C, strain hardening properties, and ≥920 kg/mand ≤950 kg/mof a density, and has ≥3 times of the expansion ratio.

Description

  The present invention relates to a non-crosslinked polyethylene extruded foam. More specifically, the present invention relates to a non-crosslinked polyethylene extruded foam comprising a specific ethylene / α-olefin copolymer, having a foaming ratio of 3 times or more and excellent in mechanical strength and secondary processability.

  Polyethylene resin foams are widely used mainly for cushioning materials, cushioning materials, impact absorbing materials, and the like, and are roughly classified into non-crosslinked foams and crosslinked foams. In recent years, from the viewpoint of reducing environmental impact, interest in improving the recyclability of plastic materials has increased, and there has been an increasing demand for non-crosslinked crosslinked products even in polyethylene resin foams. When producing a non-crosslinked, high-expanding polyethylene resin foam, a polyethylene having a high melt tension is required. Therefore, a low-density polyethylene having a long chain branch produced by a high-pressure method (hereinafter referred to as a high-pressure method). It is known that low density polyethylene) is used. However, non-crosslinked foams made of high-pressure low-density polyethylene are inferior in rigidity and heat resistance compared to crosslinked foams, and the temperature range of molding is extremely high because the viscosity changes rapidly when thermoformed. There was a drawback of being narrow. In order to solve such a problem, a high-pressure low-density polyethylene and a linear low-density polyethylene or high-density polyethylene excellent in rigidity and heat resistance may be used in combination (for example, see Patent Documents 1 and 2). Proposed. In addition, the present inventors have found that a highly rigid polyethylene extruded foam can be provided by extrusion foaming an ethylene polymer that satisfies specific requirements (see, for example, Patent Documents 3 and 4). ).

JP 60-222222 A JP 2006-274038 A JP 2006-096910 A JP 2006-199872 A

  However, in the methods proposed in Patent Documents 1 and 2, linear polyethylene is blended in a specific ratio with high-pressure low-density polyethylene, and molding must be performed under strict foaming conditions. This raises technical difficulties, and the mechanical strength and secondary workability do not necessarily satisfy the current product requirements. An object of the present invention is to provide a non-crosslinked polyethylene extruded foam that overcomes the above-mentioned drawbacks of the prior art, has a high expansion ratio, and is excellent in mechanical strength and secondary processability.

As a result of intensive studies to solve the above problems, the present inventors have found that the melt flow rate measured at 190 ° C. and a load of 2.16 kg is 0.1 g / 10 min or more and less than 50 g / 10 min according to ASTM 1238. A non-crosslinked polyethylene extrusion foamed ethylene / α-olefin copolymer having a melt tension at 160 ° C. of 40 mN or more, strain hardening, and a density in accordance with JIS K6760 of 920 kg / m ³ or more and 950 kg / m ³ or less. In addition to the excellent properties of conventional non-crosslinked polyethylene extruded foam, it has been found that a non-crosslinked polyethylene extruded foam having particularly high secondary processability can be obtained, and the present invention has been completed. It was. That is, the present invention is based on ASTM 1238, the melt flow rate measured at 190 ° C. under a load of 2.16 kg is 0.1 g / 10 min or more and less than 50 g / 10 min, the melt tension at 160 ° C. is 40 mN or more, The present invention relates to a non-crosslinked polyethylene extruded foam having a curability and comprising an ethylene / α-olefin copolymer having a density of 920 kg / m ³ or more and 950 kg / m ³ or less according to JIS K6760.

The ethylene / α-olefin copolymer constituting the non-crosslinked polyethylene extruded foam of the present invention has a melt flow rate of 0.1 g / 10 min or more and 50 g measured at 190 ° C. under a load of 2.16 kg in accordance with ASTM 1238. / 10 category, category of ethylene / α-olefin copolymers having a melt tension at 160 ° C. of 40 mN or more, strain hardening, and a density according to JIS K6760 of 920 kg / m ³ or more and 950 kg / m ³ or less Any ethylene / α-olefin copolymer may be used as long as it belongs to the above. For example, (trade name) TOSOH-HMS JK46 (manufactured by Tosoh Corporation), (trade name) TOSOH-HMS JK25 (manufactured by Tosoh Corporation), and the like are listed as commercial products. be able to.

  Moreover, it can manufacture with the following method. For example, JP-A-7-252311, JP-A-2004-346304, JP-A-2005-248013, JP-A-2006-2057, JP-A-2006-321991, JP-A-2007-169341, In the presence of a polymerization catalyst described in JP 2010-43152 A, JP 2011-89019 A, JP 2011-89020 A, ethylene is polymerized, or ethylene and an α-olefin having 3 to 8 carbon atoms. A method of copolymerization can be used.

  More specifically, for example, as a metallocene compound, a bridged bis (substituted or unsubstituted cyclopentadienyl) zirconium complex in which two substituted or unsubstituted cyclopentadienyl groups are bridged by a bridging group and / or a bridged type (Cyclopentadienyl) (indenyl) zirconium complex (hereinafter referred to as component (a)), bridged (cyclopentadienyl) (fluorenyl) zirconium complex and / or bridged (indenyl) (fluorenyl) zirconium complex In the presence of a metallocene catalyst using (hereinafter referred to as component (b)), a method of polymerizing ethylene or a method of copolymerizing ethylene and an α-olefin having 3 to 8 carbon atoms can be used.

  Specific examples of component (a) include dimethylsilylene bis (cyclopentadienyl) zirconium dichloride, dimethylsilylene (cyclopentadienyl) (indenyl) zirconium dichloride, dimethylsilylene (cyclopentadienyl) (2-methylindenyl). ) Zirconium dichloride, dimethylsilylene (cyclopentadienyl) (4,7-dimethylindenyl) zirconium dichloride, dimethylsilylene (cyclopentadienyl) (2,4,7-trimethylindenyl) zirconium dichloride, 1,1, 3,3-tetramethyldisiloxane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride, 1,1-dimethyl-1-silaethane-1,2-diyl-bis (cyclopentadienyl) zirconium Dichloride, propane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride, butane-1,4-diyl-bis (cyclopentadienyl) zirconium dichloride, cis-2-butene-1,4-diyl- Dichlorides such as bis (cyclopentadienyl) zirconium dichloride, 1,1,2,2-tetramethyldisilane-1,2-diyl-bis (cyclopentadienyl) zirconium dichloride, and dimethyl compounds of the above transition metal compounds, diethyl Body, dihydro form, diphenyl form, dibenzyl form. Further, compounds in which the hydrogen of the cyclopentadienyl derivative of the above transition metal compound is substituted with a hydrocarbon group, and compounds in which the zirconium atom of the central metal is substituted with a titanium atom or a hafnium atom can also be exemplified.

  Specific examples of component (b) include diphenylmethylene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (2-trimethylsilyl-1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, Diphenylmethylene (1-cyclopentadienyl) (2,7-dimethyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium Dichloride, isopropylidene (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, isopropylidene (1-cyclopentadienyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, diphenylsila Diyl (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, dimethylsilanediyl (1-cyclopentadienyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (1-indenyl) (9-fluorenyl) zirconium dichloride Diphenylmethylene (2-phenyl-1-indenyl) (9-fluorenyl) zirconium dichloride, diphenylmethylene (2-phenyl-1-indenyl) (2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, etc. Examples thereof include dimethyl, diethyl, dihydro, diphenyl, and dibenzyl isomers of dichloride and the above transition metal compounds. Further, compounds in which the hydrogen of the cyclopentadienyl derivative of the above transition metal compound is substituted with a hydrocarbon group, and compounds in which the zirconium atom of the central metal is substituted with a titanium atom or a hafnium atom can also be exemplified.

  Moreover, the quantity of the component (b) with respect to a component (a) does not have a restriction | limiting in particular, It is preferable that it is 0.0001-100 times mole, Most preferably, it is 0.001-10 times mole.

  And as a metallocene catalyst using component (a) and component (b), for example, a catalyst comprising component (a), component (b) and an organoaluminum compound (hereinafter referred to as component (c)); a catalyst comprising a), component (b) and aluminoxane (hereinafter referred to as component (d)); a catalyst further comprising component (c); component (a), component (b) and protonic acid salt (Hereinafter referred to as component (e)), Lewis acid salt (hereinafter referred to as component (f)) or metal salt (hereinafter referred to as component (g)). Catalyst; catalyst further comprising component (c); catalyst comprising component (a), component (b), component (d) and inorganic oxide (hereinafter referred to as component (h)); component (a ), Component (b), component (h), component (e), component (f), component (g) A catalyst comprising at least one salt; a catalyst further comprising a component (c); a component (a), a component (b), a clay mineral (hereinafter referred to as component (i)), and a component (c). Catalysts: Catalysts comprising a component (a), a component (b), and a clay mineral treated with an organic compound (hereinafter referred to as component (j)) can be exemplified. Preferably, the component (a) and the component ( A catalyst comprising b) and component (j) can be used.

  Here, examples of the clay mineral that can be used as the component (i) and the component (j) include fine particles mainly composed of microcrystalline silicate. As a structural feature, a layered structure is formed, and various layers of negative charges are included in the layer. In this respect, it is greatly different from a metal oxide having a three-dimensional structure such as silica or alumina. These clay minerals are generally of a large layer charge, with pyrophyllite, kaolinite, dickite and talc groups (negative charge per chemical formula is approximately 0), smectite groups (negative charge per chemical formula is from about 0.25). 0.6), vermiculite group (negative charge per chemical formula is approximately 0.6 to 0.9), mica group (negative charge per chemical formula is approximately 1), brittle mica group (negative charge per chemical formula is approximately 2) It is classified. Each group shown here includes various clay minerals, and examples of the clay mineral belonging to the smectite group include montmorillonite, beidellite, saponite, hectorite and the like. Further, a plurality of the above clay minerals can be mixed and used.

  The organic compound treatment in component (j) refers to introducing an organic ion between clay mineral layers to form an ionic complex. Examples of the organic compound used in the organic compound treatment include N, N-dimethyl-n-octadecylamine hydrochloride, N, N-dimethyl-n-eicosylamine hydrochloride, N, N-dimethyl-n-docosylamine hydrochloride, N, N-dimethyloleylamine hydrochloride, N, N-dimethylbehenylamine hydrochloride, N-methyl-bis (n-octadecyl) amine hydrochloride, N-methyl-bis (n-eicosyl) amine hydrochloride, N-methyl -Dioleylamine hydrochloride, N-methyl-dibehenylamine hydrochloride, N, N-dimethylaniline hydrochloride can be exemplified.

  The catalyst comprising component (a), component (b) and component (j) can be obtained by bringing component (a), component (b) and component (j) into contact in an organic solvent, A method of adding component (b) to the contact product of (a) and component (j); a method of adding component (a) to the contact product of component (b) and component (j); and component (a) A method of adding the component (j) to the contact product of the component (b); a method of adding the contact product of the components (a) and (b) to the component (j) can be exemplified.

  As the contact solvent, aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane, nonane, decane, cyclopentane or cyclohexane, aromatic hydrocarbons such as benzene, toluene or xylene, ethyl ether or n-butyl ether And ethers such as halogenated hydrocarbons such as methylene chloride or chloroform, 1,4-dioxane, acetonitrile, or tetrahydrofuran.

  About a contact temperature, it is preferable to select between 0-200 degreeC and to process.

  The amount of each component used is 0.0001 to 100 mmol, preferably 0.001 to 10 mmol of component (a) per 1 g of component (j).

  The contact product of component (a), component (b) and component (j) prepared in this way may be used without washing, or may be used after washing. Further, when the component (a) or the component (b) is a dihalogen, it is preferable to further add the component (c). Further, component (c) can be added for the purpose of removing impurities in component (j), polymerization solvent and olefin.

  When producing the ethylene-based polymer, it is preferably carried out at a polymerization temperature of −100 to 120 ° C., preferably 20 to 120 ° C. in view of productivity, and more preferably in the range of 60 to 120 ° C. preferable. The polymerization time is preferably in the range of 10 seconds to 20 hours, and the polymerization pressure is preferably in the range of normal pressure to 300 MPa. The polymerizable monomer is ethylene alone or ethylene and an α-olefin having 3 to 8 carbon atoms. When ethylene is an α-olefin having 3 to 8 carbon atoms, ethylene and α-olefin having 3 to 8 carbon atoms are used. As the olefin supply ratio, ethylene / C3-C8 α-olefin (molar ratio) of 1 to 200, preferably 3 to 100, and more preferably 5 to 50 can be used. It is also possible to adjust the molecular weight using hydrogen during polymerization. The polymerization can be carried out by any of batch, semi-continuous and continuous methods, and can be carried out in two or more stages by changing the polymerization conditions. In addition, the ethylene copolymer can be obtained by separating and recovering from the polymerization solvent by a conventionally known method after the completion of the polymerization and drying.

  Polymerization can be carried out in a slurry state, a solution state, or a gas phase state. In particular, when the polymerization is performed in a slurry state, an ethylene-based copolymer having a powder particle shape is efficiently and stably produced. Can do. Further, the solvent used for the polymerization may be any organic solvent that is generally used, and specific examples include benzene, toluene, xylene, propane, isobutane, pentane, hexane, heptane, cyclohexane, gasoline, and the like, propylene, Olefin itself such as 1-butene, 1-hexene and 1-octene can also be used as a solvent.

Here, when the MFR of the ethylene / α-olefin copolymer is less than 0.1 g / 10 minutes, the load on the extruder at the time of molding increases, and the productivity decreases. On the other hand, in the case of 50 g / 10 min or more, since foam does not grow uniformly at the time of foam molding, a good foam cannot be obtained. In the case of an ethylene / α-olefin copolymer having a melt tension of less than 40 mN, outgassing during foam molding is increased, the expansion ratio is lowered, and the product shape is difficult to control, and the foam molded product is stable. You will not be able to get. Furthermore, in the case of an ethylene / α-olefin copolymer that does not exhibit strain-hardening properties, when it is an extruded foam molded body, the bubbles are united, and an extruded foam having uniform and fine bubbles is Don't be. When the density is less than 920 kg / m ³ , the obtained extruded foam is inferior in rigidity, and when it is made into a thin-walled foam, the deflection of the foam is large, which causes a problem in secondary processing. On the other hand, when the density exceeds 950 kg / m ³ , the obtained extruded foam is excellent in rigidity but poor in flexibility, and inferior in secondary workability such as various bending workability. As described above, the ethylene / α-olefin copolymer used in the present invention has a specific structure, and becomes an uncrosslinked polyethylene extruded foam excellent in mechanical strength and secondary processability by extrusion foaming. Moreover, the non-crosslinked polyethylene extruded foam of the present invention has a foaming ratio of 3 times or more. Here, when the expansion ratio is less than 3 times, the cushioning property of the foam is inferior, which causes a problem in secondary processability such as bending.

The MFR in the present invention can be measured at a temperature of 190 ° C. and a load of 2.16 kg in accordance with ASTM 1238. In addition, (trade name) Capillograph (manufactured by Toyo Seiki Seisakusho) is used for melt tension. A strand lowered at a piston lowering speed of 10 mm / min is drawn at 10 m / min from a die having a length (L) of 8 mm and a diameter (D) of 2.095 mm at 190 ° C., and the take-up load is measured as a melt tension. Can do. For the strain hardening, the maximum value of the extension viscosity measured at 160 ° C. and the strain rate of 0.07 to 0.1 s ⁻¹ using a Meissner type uniaxial extension viscometer is the extension viscosity in the linear region at that time. The value divided by is defined as a non-linear parameter λ, and when λ exceeds 1, it can be confirmed that there is strain hardening. Note that M.M. Yamaguchi et al. Polymer Journal 32, 164 (2000). As described in, the elongational viscosity in the linear region can be calculated from dynamic viscoelasticity. When λ is 1, it can be determined that there is no strain hardening.

The ratio of the weight average molecular weight (Mw) to Mn (Mw / Mn) of the ethylene / α-olefin copolymer constituting the non-crosslinked polyethylene extruded foam of the present invention is preferably 3.0 to 6.0, more preferably 3.5 to 5.5. It is preferable that Mw / Mn is within this range because good foamability and foam moldability can be obtained. The number average molecular weight (Mn) measured by GPC is preferably 15,000 or more, more preferably 15,000 to 100,000, and particularly preferably 15,000 to 50,000. When Mn is 15,000 or more, the mechanical strength of the obtained foamed molded product is increased.
The ethylene / α-olefin copolymer used in the present invention includes a heat resistance stabilizer, a weather resistance stabilizer, an antistatic agent, an antifogging agent, an antiblocking agent, a slip agent, a lubricant, a nucleating agent, a pigment, carbon black, talc. Further, known additives such as inorganic fillers or reinforcing agents such as glass powder and glass fiber, organic fillers or reinforcing agents, flame retardants, and neutron shielding agents can be blended. Moreover, it can also be used by mixing with other thermoplastic resins. Examples of these include high density polyethylene (HDPE), linear low density polyethylene (L-LDPE), low density polyethylene (LDPE), polypropylene resin, poly-1-butene, poly-4-methyl-1-pentene. And ethylene / vinyl acetate copolymer, ethylene / vinyl alcohol copolymer, polystyrene, and maleic anhydride grafts thereof.

  As a manufacturing method of the non-crosslinked polyethylene extruded foam of the present invention, any method may be used as long as the non-crosslinked polyethylene extruded foam is obtained. For example, the ethylene / α-olefin copolymer and, if necessary, Supply the air conditioner such as talc, shrinkage inhibitor, etc. to the extruder, heat melt, knead, further supply the foaming agent to make a foamable molten resin mixture, then the extrusion resin temperature, extrusion die internal pressure A method of adjusting the discharge amount and the like and extruding from a die attached to the tip of the extruder into a low pressure region to cause foaming is exemplified. Also, extrusion foams of various shapes such as round bar foams, sheet foams, plate foams, etc. are manufactured by selecting a die attached to the extruder tip according to the desired foam shape can do. For example, if a strand die is attached, a round bar-like foam can be obtained; if an annular die is attached, a sheet-like foam can be obtained; and if a slit die is attached, a plate-like foam can be produced. .

  The non-crosslinked polyethylene extruded foam of the present invention is prepared by supplying the ethylene / α-olefin copolymer, additive, foaming agent and the like to an extruder, heating and kneading to obtain a foamable molten resin mixture, and then extruding resin. It can be formed by adjusting the temperature within an appropriate range and extruding from an extruder to a low pressure region. The specific extrusion resin temperature is based on the melting point of the ethylene polymer, and the extrusion resin temperature of the foamable molten resin is (melting point of the ethylene polymer−10 ° C.) to (melting point of the ethylene polymer + 10. It is preferable to adjust within the range of (degreeC), and it is more preferable to adjust within the range of (melting point of the said ethylene polymer -5 degreeC)-(melting point of the said ethylene polymer +5 degreeC). When the extrusion resin temperature is lower than (the melting point of the melting point of the ethylene-based polymer −10 ° C.), crystallization occurs at the die part and it becomes difficult to obtain a foam. On the other hand, when the extrusion temperature is higher than (the melting point of the ethylene-based polymer + 5 ° C.), the bubbles of the resulting foam break up and become non-uniform. The melting point of the ethylene-based polymer is a peak apex temperature obtained from a test piece subjected to a constant heat treatment by a heat flux DSC curve based on JIS K7121 (1987). When two or more peaks appear, the vertex temperature of the main peak having the largest peak area is defined as the melting point. Examples of the foaming agent in extrusion foam molding include inorganic gas foaming agents such as carbon dioxide, nitrogen, argon, and air; propane, butane, pentane, hexane, cyclobutane, cyclohexane, trichlorofluoromethane, dichlorodifluoromethane, and the like. Volatile foaming agents of: azodicarbonamide, barium azodicarboxylate, N, N-dinitrosopentamethylenetetramine, 4,4′-oxybis (benzenesulfonylhydrazide) which is liquid or solid at room temperature and generates gas upon heating ), Chemical blowing agents such as diphenylsulfone-3,3′-disulfonylhydrazide, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, biurea, zinc carbonate, and the like. Non-crosslinked polyethylene extruded foam of the present invention Preferably 1-20 parts by weight with respect to the ethylene-based polymer 100 parts by weight of formed, particularly preferably in the range of 5 to 15 parts by weight.

  According to the present invention, a non-crosslinked polyethylene extruded foam having a high expansion ratio and excellent mechanical strength and secondary workability can be easily obtained. The use of the non-crosslinked polyethylene extruded foam of the present invention is not particularly limited, and can be suitably used as a heat insulating molded body for food containers, building materials, heating equipment and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  Below, the measuring method used by the Example and the comparative example is shown.

~ Measurement of MFR ~
In accordance with ASTM 1238, the measurement was performed at a temperature of 190 ° C. and a load of 2.16 kg.

~ Measurement of melt tension ~
Capillograph (manufactured by Toyo Seiki Seisakusho) was used. A strand lowered at a piston lowering speed of 10 mm / min was drawn at 10 m / min from a die having a length (L) of 8 mm and a diameter (D) of 2.095 mm at 190 ° C., and the take-up load was taken as melt tension.

~ Measurement of strain hardening ~
The measurement was performed using a Meissner type uniaxial extensional viscometer (manufactured by Toyo Seiki Seisakusho, trade name: Melten Rheometer) set at a temperature of 160 ° C. The non-linear parameter (λ) was obtained as a value obtained by dividing the maximum value of the extensional viscosity measured under the condition of strain rate of 0.07 to 0.1 s ⁻¹ by the extensional viscosity in the linear region at that time. In addition, the value of the extensional viscosity in the linear region is taken by Takeshi Fukuda, New Polymer Experimental Science 1, Basics of Polymer Experiment, Molecular Characteristic Analysis, “3-4. Molecular Shape and Form”, 295 (1994). According to the method described in the above, calculation was performed using an approximate expression from dynamic viscoelasticity. When the obtained λ exceeded 1, it was judged that there was strain hardening.

~density~
The density gradient tube method was used in accordance with JIS K6760 (1995).

-Weight average molecular weight (Mw), number average molecular weight (Mn), ratio of weight average molecular weight to number average molecular weight (Mw / Mn)-
The weight average molecular weight (Mw), the number average molecular weight (Mn), and the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn) were measured by GPC. The column temperature was set to 140 ° C. using a GPC device (Tosoh Corp. (trade name) HLC-8121GPC / HT) and a column (Tosoh Corp. (trade name) TSKgel GMHhr-H (20) HT). The measurement was performed using 1,2,4-trichlorobenzene as an eluent. A measurement sample was prepared at a concentration of 1.0 mg / ml, and 0.3 ml was injected and measured. The calibration curve of molecular weight was calibrated using a polystyrene sample having a known molecular weight. In addition, Mw and Mn were calculated | required as a value of linear polyethylene conversion.

-Evaluation of physical properties and moldability of extruded foam sheet-
~ Foaming ratio ~
From an extruded foam sheet obtained by molding the ethylene polymer used in the present invention, a foam having a width of 5 cm, a length of 5 cm, and a thickness of about 1.5 cm (which differs slightly depending on the sample) was cut out and weight Wg) Was measured, and the apparent density was calculated by the following formula in accordance with JIS K 6767.

Apparent density (g / cm ³ ) = W / (5 × 5 × 1.5)
The expansion ratio was determined from the apparent density by the following formula.

Foaming ratio = 1 / apparent density-foam sheet properties-
The appearance of the extruded foam sheet obtained by molding the ethylene polymer used in the present invention and the state of bubbles in the cross section were visually evaluated.
○: Smooth surface foam shape, uniform cell state Δ: Smooth surface foam shape, non-uniform cell state ×: Uneven foam shape, non-uniform cell state… ×
~ Foam sheet compression strength ~
A test piece having a width of 10 mm, a length of 50 mm, and a thickness of 10 mm was cut out from an extruded foam sheet obtained by molding the ethylene polymer used in the present invention, and a tensile tester (manufactured by A & D Co., Ltd., product) Name: Tensilon RTE-1210) compression mode, and calculated based on compressive stress at the time of 25% compression in the thickness direction at a compression speed of 10 mm / min.

-Secondary workability (thermoformability)-
Extruded foam sheets obtained by molding the ethylene polymer used in the present invention were each molded with a molding machine having a molding cycle of 10 seconds and a molding heater temperature of 140 ° C. in a vacuum molding machine equipped with a mold having a major axis of 100 mm and a depth of 50 mm. Molding was performed, and the occurrence of tearing and cracking of the container was examined with 10 shots.
○: No shape defect, no tearing or cracking occurred in all 10 shots.
(Triangle | delta): The shape defect, the tear, and the crack do not generate | occur | produce in 1 or more in 10 shots.
X: Shape failure, tearing and cracking occur in all 10 shots.

-Secondary workability (folding workability)-
A test piece having a width of 10 mm and a length of 100 mm was cut out from an extruded foam sheet obtained by molding the ethylene-based polymer used in the present invention, bent by hand, and generation of cracks or cracks in the ten test pieces. The presence or absence was confirmed visually.
○: No cracks or cracks occurred in all 10 pieces.
(Triangle | delta): The crack and the crack have not generate | occur | produced in 1 or more of 10 pieces.
X: Cracks and cracks occur in all 10 pieces.

-Ethylene / α-olefin copolymer-
The ethylene / α-olefin copolymers used in Examples and Comparative Examples are shown below.

PE-1: manufactured by Tosoh Corporation, (trade name) Tosoh HMS CK27 (MFR 2.5 g / 10 min, density 927 kg / m ³ , melt tension 67 mN, Mn 17,000, Mw / Mn 5.3)
PE-2: manufactured by Tosoh Corporation, (trade name) Tosoh HMS CK37 (MFR 3.3 g / 10 min, density 935 kg / m ³ , melt tension 57 mN, Mn 17,000, Mw / Mn 5.6)
PE-3: manufactured by Tosoh Corporation, (trade name) Tosoh HMS CK38 (MFR 0.8 g / 10 min, density 938 kg / m ³ , melt tension 100 mN, Mn 25,000, Mw / Mn 4.4)
PE-4: manufactured by Tosoh Corporation, (trade name) Tosoh HMS CK47 (MFR 4.0 g / 10 min, density 940 kg / m ³ , melt tension 72 mN, Mn 23,000, Mw / Mn 3.7)
Examples 1-4
Foam molding polyethylene containing 0.1 parts by weight of talc (trade name: MS, manufactured by Nippon Talc, average particle size: 8 μm) as a foam nucleating agent with respect to 100 parts by weight of the ethylene / α-olefin copolymer. A system resin composition was prepared by dry blending. And using a foam molding extrusion equipment of a single screw extruder (screw diameter 50 mmφ, L / D = 36, manufactured by Kyodo Machine) having a barrel hole for injecting a volatile liquid in the middle of the barrel, a polyethylene system for foam molding After the resin composition was supplied at 15 kg / hour and melt-kneaded, the compressed liquid butane was pressed through the barrel hole at 1200 g / hour to disperse and dispersed by a slit die (width 500 mm) set at 130 ° C. A sheet-like foamed molded product was extruded.

  The obtained non-crosslinked polyethylene extruded foam sheet had high surface smoothness and uniform fine cells, and the expansion ratio was 35 times. It was confirmed that both the compressive strength and secondary processability were better than the general high pressure method low density polyethylene foam. The results are shown in Table 1.

Example 5
The same procedure as in Example 1 was conducted except that CK27 was used as the ethylene / α-olefin copolymer and the amount of liquid butane during foam molding was changed to 100 g / hr. The results are shown in Table 1.

Comparative Example 1
Commercially available low density polyethylene produced by high pressure method instead of ethylene / α-olefin copolymer (manufactured by Tosoh, (trade name) Petrocene 186; MFR = 3.0 g / 10 min, density = 924 kg / m ³ , melt The test was performed in the same manner as in Example 1 except that the tension was 90 mN, the strain was hardened, and Mn 16,000 and Mw / Mn 3.9) were used. The results are shown in Table 2.

Comparative Example 2
Commercially available low density polyethylene manufactured by high pressure method instead of ethylene / α-olefin copolymer (manufactured by Tosoh, (trade name) Petrocene 172; MFR = 0.3 g / 10 min, density = 920 kg / m ³ , melt This was carried out in the same manner as in Example 1 except that a tension of 230 mN, strain hardening property, Mn 19,000, Mw / Mn 5.5) was used. The results are shown in Table 2.

Comparative Example 3
Commercially available linear low density polyethylene produced by using Ziegler-Natta type catalyst instead of ethylene / α-olefin copolymer (manufactured by Tosoh, (trade name) Nipolon-LM50; MFR = 3.0 g / 10 min. , Density = 936 kg / m ³ , melt tension 9 mN, no strain hardening, Mn 25,000, Mw / Mn 3.5). The results are shown in Table 2.

Comparative Example 4
Commercially available linear low density polyethylene produced by using Ziegler-Natta type catalyst instead of ethylene / α-olefin copolymer (manufactured by Tosoh, (trade name) Nipolon-LF13; MFR = 0.5 g / 10 min. , Density = 920 kg / m ³ , melt tension 45 mN, no strain hardening, Mn 23,000, Mw / Mn 3.7) The results are shown in Table 2.

Comparative Example 5
The same operation as in Example 2 was conducted except that the amount of liquid butane during foam molding was changed to 60 g / hour.

  The results are shown in Table 2.

Claims (2)

According to ASTM 1238, the melt flow rate measured at 190 ° C. under a load of 2.16 kg is 0.1 g / 10 min or more and less than 50 g / 10 min, the melt tension at 160 ° C. is 40 mN or more, and has strain hardening properties. A non-crosslinked polyethylene extruded foam comprising an ethylene / α-olefin copolymer having a density in accordance with JIS K6760 of 920 kg / m ³ or more and 950 kg / m ³ or less and having an expansion ratio of 3 times or more. The non-crosslinked polyethylene extruded foam according to claim 1, wherein Mw / Mn of the ethylene / α-olefin copolymer is in the range of 3.0 to 6.0 and Mn is 15,000 or more.