Non-crosslinked foam molding comprising polyethylene-based resin

Abstract

To provide a polyethylene-based resin composition which is formed into a non-crosslinked foam molding that has a high expansion ratio and is excellent in compression durability and secondary workability.MEANS FOR SOLVING THE PROBLEM: A non-crosslinked foam molding comprises a polyethylene-based resin which has a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, has, in a dynamic viscoelasticity measurement at a frequency of 0.1 Hz, a ratio of complex viscosity at 110°C to that at 100°C of 5 or less when the temperature is lowered at 1°C / min from 140°C and a loss tangent of 3 or less at 110°C, and has, in DSC, one peak of heat generation of crystallization in the range of 60°C to 130°C when the temperature is lowered at 10°C / min from 180°C and a heat of fusion of 5 J / g or more at 120°C or more when the temperature is raised at 10°C / min from room temperature.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a non-crosslinked foam molded article made of a polyethylene-based resin, and more specifically to a foam made of a polyethylene-based resin having specific melt tension, complex viscosity, loss tangent, crystallization characteristics, and heat of fusion. [Background technology]

[0002] Polyethylene-based resin foams are widely used, primarily as buffer materials, cushioning materials, and shock absorbers, and are broadly classified into non-crosslinked and crosslinked foams. In recent years, there has been growing interest in improving the recyclability of plastic materials from the perspective of reducing environmental impact, and there is also a growing demand for non-crosslinked polyethylene-based resin foams. The production of non-crosslinked polyethylene-based resin foams with a high expansion ratio requires polyethylene with high melt tension, and it is therefore well known that low-density polyethylene with long chain branches produced by a high-pressure process (hereinafter referred to as high-pressure low-density polyethylene) is used. Non-crosslinked foams made from high-pressure low-density polyethylene are flexible and have excellent compression durability, making them suitable for applications that require repeated compression (such as buffer materials). However, they suffer from the drawback of a very narrow molding temperature range due to a sudden change in viscosity during secondary processing such as thermoforming. To address this issue, it has been proposed to use a mixture of high-pressure low-density polyethylene and linear low-density polyethylene or high-density polyethylene (see, for example, Patent Documents 1 and 2). The present inventors have also found that ethylene-α-olefin copolymers that satisfy specific requirements have excellent foaming properties and extrusion foam moldability (see, for example, Patent Documents 3 and 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 60-222222 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-274038 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-096910 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-199872 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the methods proposed in Patent Documents 1 and 2 require the use of linear polyethylene that has low melt tension and does not exhibit foamability, and flexibility is lost during repeated compression, making it difficult to apply the foam to cushioning materials that are frequently subjected to compression.The object of the present invention is to overcome the drawbacks of the prior art and to provide a non-crosslinked polyethylene resin foam that has a high expansion ratio, excellent compression durability, and excellent secondary processability. [Means for solving the problem]

[0005] As a result of intensive research to solve the above problems, the present inventors have found that a polyethylene resin having a specific melt tension, complex viscosity, crystallization characteristics, and heat of fusion is excellent in extrusion foamability, and a non-crosslinked polyethylene resin foam having excellent heat resistance and flexibility can be obtained, and have thus completed the present invention. That is, the respective aspects of the present invention are as follows [1] to [8]. [1] A non-crosslinked foam molded product made of an ethylene-based resin, which has a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, a dynamic viscoelasticity measurement in which the ratio of the complex viscosity at 110°C to that at 100°C when cooled from 140°C at a frequency of 0.1 Hz and 1°C / min is 5 or less, and a loss tangent at 110°C of 3 or less, a single peak of exothermic heat of crystallization in the range of 60°C to 130°C when cooled from 180°C at 10°C / min when measured by DSC, and a heat of fusion of 5 J / g or more at 120°C or higher when heated from room temperature at 10°C / min. [2] The polyethylene resin is subjected to a test at 140°C and a strain rate of 0.2 sec -1 The non-crosslinked foam molded article according to [1], which has strain hardening of elongational viscosity and has a strain hardening ratio of elongational viscosity of 1.5 or more and 4.0 or less. [3] The non-crosslinked foam molded article according to [1] or [2], wherein the polyethylene resin has a flow activation energy of 30 kJ / mol or more and 45 kJ / mol or less, measured at a temperature range of 140°C to 220°C. [4] The polyethylene resin has a melt flow rate (hereinafter referred to as MFR) of 0.5 g / 10 min or more but less than 8 g / 10 min, measured at 190 °C and a load of 21.2 N, and a density of 930 kg / m 3 More than 945kg / m 3 The non-crosslinked foam molded article according to any one of [1] to [3], which is made of the following polyethylene resin: [5] The non-crosslinked foam molded article according to any one of [1] to [4], wherein the polyethylene resin has a value of 20 or more, calculated by multiplying the ratio of the complex viscosity at a frequency of 100 Hz and a frequency of 0.1 Hz at a temperature of 140°C, as measured by dynamic viscoelasticity measurement, by MFR. [6] The non-crosslinked foam molded article according to any one of [1] to [5], which has a closed cell content of 70% or more. [7] A method for producing a non-crosslinked foam molded article according to any one of [1] to [6], comprising extrusion foam molding an ethylene-based resin having a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, a complex viscosity ratio of 5 or less at 110°C to 100°C when the temperature is decreased from 140°C at a frequency of 0.1 Hz at 1°C / min in dynamic viscoelasticity measurement, and a loss tangent of 3 or less at 110°C, a single peak of exothermic heat of crystallization in the range of 60°C to 130°C when the temperature is decreased from 180°C at 10°C / min in DSC measurement, and a heat of fusion of 5 J / g or more at 120°C or higher when the temperature is increased from room temperature at 10°C / min. [8] The method for producing a non-crosslinked foam molded article according to [7], wherein one or more gases selected from the group consisting of butane, carbon dioxide, nitrogen, and chlorofluorocarbon gases are used as the foaming agent. [Effects of the Invention]

[0006] According to the present invention, a non-crosslinked polyethylene resin foam can be obtained which can provide a foam having a high expansion ratio and excellent heat resistance and secondary processability. DETAILED DESCRIPTION OF THE INVENTION

[0007] The present invention will be described in detail below.

[0008] The non-crosslinked foam molded article according to one embodiment of the present invention is a non-crosslinked foam molded article made of a polyethylene resin having a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, a complex viscosity ratio of 5 or less at 110°C to 100°C when the temperature is decreased from 140°C at a frequency of 0.1 Hz at 1°C / min in dynamic viscoelasticity measurement, and a loss tangent of 3 or less at 110°C, a single peak of exothermic heat of crystallization in the range of 60°C to 130°C when the temperature is decreased from 180°C at 10°C / min in DSC measurement, and a heat of fusion of 5 J / g or more at 120°C or higher when the temperature is increased from room temperature at 10°C / min.

[0009] The non-crosslinked foam molded article is a foam made of a polyethylene resin having a melt tension of 50 mN or more, preferably 60 mN or more, at 160°C and a take-up speed of 10 m / min. If the melt tension is less than 50 mN, the foam molded article will have coalesced cells, will not have uniform fine cells, and will have poor compression recovery, which is undesirable.

[0010] The non-crosslinked foam molded article is a foam made of a polyethylene resin in which, in dynamic viscoelasticity measurement, the ratio of complex viscosities at 110°C to 100°C when the temperature is decreased from 140°C at a frequency of 0.1 Hz at 1°C / min is 5 or less, preferably 3 or less, and the loss tangent at 110°C is 3 or less, preferably 2.5 or less. Here, if the complex viscosity ratio exceeds 5, the molten polyethylene resin will rapidly solidify at the die outlet of the molding machine during foam molding, causing the die to clog, which is undesirable. If the loss tangent at 110°C is greater than 3, the cell diameter will become non-uniform, which is also undesirable.

[0011] This non-crosslinked foam molded product is a foam made from a polyethylene resin that exhibits one peak of exothermic heat due to crystallization in the range of 60 to 130°C when the temperature is decreased from 180°C at a rate of 10°C / min in a DSC. In the case of a polyethylene resin that exhibits multiple exothermic peaks, the crystallization process becomes uneven, with the cell membranes penetrating, resulting in an open-cell foam, and the compression recovery of the foam molded product is poor.

[0012] The present non-crosslinked foam molded article is a non-crosslinked foam molded article made of a polyethylene resin having a heat of fusion of 5 J / g or more, preferably 10 J / g or more, at 120°C or higher when heated from room temperature at a rate of 10°C / min. If the heat of fusion is less than 5 J / g, the foam will have poor heat resistance.

[0013] The present non-crosslinked foam molded article is a foam made of a polyethylene resin in which the value obtained by multiplying the viscosity ratio at a frequency of 100 Hz and a frequency of 0.1 Hz at a temperature of 140°C by the MFR in dynamic viscoelasticity measurement is 20 or more, preferably 30 or more. If the value obtained by multiplying the viscosity ratio by the MFR is less than 20, the foam molded article will have poor appearance and its smoothness will be impaired, which is not preferred.

[0014] In addition, this non-crosslinked foamed molded product has a high closed cell ratio and excellent compression recovery, so it can be used at 140°C and a strain rate of 0.2 sec -1 In the above, the foamed molded article is preferably made of a polyethylene resin having strain hardening properties of extensional viscosity and having a strain hardening ratio of extensional viscosity of 1.5 or more and 4.0 or less.

[0015] Furthermore, the present non-crosslinked foam molded article is preferably a foam molded article made of a polyethylene resin having an MFR of 0.5 g / 10 min or more and less than 8.0 g / 10 min, as this foam has good moldability and is excellent in expandability and mechanical strength.

[0016] In addition, the non-crosslinked foamed molded article is a foamed article with excellent flexibility and heat resistance, and has a density of 930 kg / m 3 More than 945kg / m 3 The foamed molded article is preferably made of the following polyethylene resin.

[0017] Since the present non-crosslinked foamed molded article is a foamed molded article with excellent compression recovery, it is preferable that the resin be a polyethylene-based resin having a flow activation energy of 30 kJ / mol or more and 45 kJ / mol or less, measured at temperatures ranging from 140°C to 220°C.

[0018] Furthermore, since the present non-crosslinked foamed molded article is a foamed molded article having particularly excellent compression durability, it is preferable that the closed cell content is 70% or more, and more preferably 80% or more.

[0019] The polyethylene resin of the present non-crosslinked foamed molded product may be any ethylene resin as long as it belongs to the category of polyethylene resins, and particularly preferred are ethylene resins having long chain branches, such as low-density polyethylene having a density of 918 or more, high-density polyethylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, etc. These may be used alone, or a polyethylene resin may be a blend of multiple polyethylene resins.

[0020] From the viewpoint of excellent foaming properties, the ethylene resin preferably contains 30% by weight or more, more preferably 50% by weight or more, of a polyethylene resin having a long-chain branched structure.

[0021] In addition, when multiple polyethylene resins are blended, a polyethylene resin that is good for foam molding can be obtained if the compatibility is high. Therefore, it is recommended that the density difference between the polyethylene resins to be blended is 20 kg / m 3 or less, preferably 15 kg / m 3 It is preferable that:

[0022] The polyethylene resin preferably contains a foam regulator such as sodium bicarbonate, silica, talc, or citric acid, and / or a shrinkage inhibitor such as glycerin monobehenate, glycerin monostearate, or glycerin mono-12-hydroxystearate, in order to produce a foam with a higher expansion ratio. The polyethylene resin may also be blended with known additives such as heat stabilizers, weather stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, lubricants, nucleating agents, pigments, inorganic fillers or reinforcing agents such as carbon black, talc, glass powder, and glass fiber, organic fillers or reinforcing agents, flame retardants, and neutron shielding agents. The polyethylene resin composition can be obtained by a conventionally known method, for example, a method of mixing using a Henschel mixer, V-blender, ribbon blender, tumbler blender, or the like, or by further melt-kneading a mixture obtained by such a method using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, or the like, followed by granulation.

[0023] The polyethylene resin can be extruded and foamed without the addition of a crosslinking agent to form a non-crosslinked foam molded article having excellent heat resistance.

[0024] One embodiment of the present invention involves a method for producing an extruded foam molded product by extrusion foaming the polyethylene resin described above in a non-crosslinked manner. Any method may be used to produce the foam, as long as it produces a foam molded product. Examples include a method in which a polyethylene resin, optionally containing a cell regulator such as talc and a shrinkage inhibitor, is fed into an extruder, heated and melted, and kneaded, followed by adding a foaming agent to produce a foamable molten resin mixture. The resulting mixture is then extruded into a low-pressure region through a die attached to the end of the extruder, adjusting the extrusion resin temperature, the internal pressure of the extrusion die, the output rate, and the like, and foamed. Furthermore, by selecting the die attached to the end of the extruder according to the desired shape of the foam molded product, various shapes of extruded foam molded products, such as rod-shaped foam molded products, sheet-shaped foam molded products, and plate-shaped foam molded products, can be produced. For example, a strand die can be used to produce rod-shaped foam molded products, an annular die can be used to produce sheet-shaped foam molded products, and a slit die can be used to produce plate-shaped foam molded products.

[0025] A foamed molded article made of a polyethylene-based resin can be formed by supplying a polyethylene-based resin, additives, a foaming agent, etc. to an extruder, heating and melting the mixture to form a foamable molten resin mixture, and then adjusting the extrusion resin temperature to within an appropriate range and extruding the mixture from the extruder into a low-pressure region.

[0026] Specifically, the extrusion temperature of the foamable molten resin is preferably adjusted within the range of (crystallization temperature of polyethylene resin + 1°C) to (crystallization temperature of polyethylene resin + 10°C) based on the melting point of the polyethylene resin, and more preferably within the range of (crystallization temperature of polyethylene resin + 2°C) to (crystallization temperature of polyethylene resin + 5°C). The crystallization temperature of the polyethylene resin is the apex temperature of the peak determined from a test piece subjected to a certain heat treatment using a heat flux DSC curve in accordance with JIS K7121 (1987). Examples of blowing agents for use in extrusion foam molding include inorganic gas blowing agents such as carbon dioxide, nitrogen, argon, and air; volatile blowing agents such as propane, butane, pentane, hexane, cyclobutane, cyclohexane, trichlorofluoromethane, and dichlorodifluoromethane; and chemical blowing agents that are liquid or solid at room temperature and generate gas upon heating, such as azodicarbonamide, barium azodicarboxylate, N,N-dinitrosopentamethylenetetramine, 4,4'-oxybis(benzenesulfonylhydrazide), diphenylsulfone-3,3'-disulfonylhydrazide, p-toluenesulfonylsemicarbazide, trihydrazinotriazine, biurea, and zinc carbonate. Foams using one or more gases selected from the group consisting of butane, carbon dioxide, nitrogen, and chlorofluorocarbons are preferred, as they produce foamed molded articles with a particularly high expansion ratio.

[0027] The foam has high heat resistance, a high expansion ratio, and excellent compression durability, secondary processability, and heat insulation properties, and therefore can be used for applications such as heat insulating materials and building materials. [Example]

[0028] The present invention will be described in more detail below by showing examples, but the present invention is not limited to these examples.

[0029] The measurement methods used in the examples and comparative examples are shown below. ~MFR measurement~ Measurement was carried out in accordance with JIS K6922-1 at a temperature of 190°C and a load of 2.16 kg. ~Density~ Measurement was carried out by the density gradient tube method in accordance with JIS K6922-1. ~Melt tension measurement~ A capillary viscometer (product name: Capilograph, manufactured by Toyo Seiki Seisakusho) was used. At 160°C, a strand was drawn down from a die having a length (L) of 8 mm and a diameter (D) of 2.095 mm at a piston descending speed of 10 mm / min, and then taken up at 10 m / min. The take-up load was taken as the melt tension. ~Measuring the complex viscosity ratio and loss tangent~ A parallel plate rheometer (product name MR-500, manufactured by Rheology Co., Ltd.) was used. 20 mm diameter parallel plates were used as the jig. The sample was a 1 mm press-molded sheet cut into a 20 mm diameter piece. The sample was placed in the center of the jig and heated to 140°C for 3 minutes. After that, the temperature was lowered at a rate of 1°C / min. Vibrations were applied at a measurement frequency of 0.1 Hz to measure the complex viscosity and loss tangent at 110°C.

[0030] The complex viscosity at 100°C was divided by the complex viscosity at 110°C to obtain the complex viscosity ratio. ~Number of crystallization peaks~ A polyethylene resin sheet was press-molded to a thickness of 0.2 mm, and heated to 200°C for 10 minutes using a heat flux differential scanning calorimeter (Hitachi High-Tech Science DS7000X), followed by cooling at a rate of 10°C / min. From the resulting DSC curve, the exothermic peak that appears when polyethylene crystallizes in the range of 60°C to 130°C was measured. ~Measurement of activation energy and viscosity ratio~ A 1.0 mm polyethylene resin sheet was press-molded into a viscoelasticity measuring device (product name: MCR 702 MultiDrive, manufactured by Anton Paar) equipped with a 25 mm diameter cone plate and a 2° cone angle. The storage modulus (G') and loss modulus (G") were measured at temperatures of 140°C, 160°C, 190°C, and 220°C at frequencies ranging from 0.01 rad / sec to 100 rad / sec. The shift factor (aT) was calculated based on the temperature-time conversion rule, with a reference temperature of 140°C. The activation energy was calculated from the slope (B) of the plot of log aT versus the reciprocal of the measurement temperature using the following equation (1). R is the gas constant.

[0031] Activation energy = 2.303 × R × B (1) The ratio of the complex viscosity measured at a temperature of 140°C with a frequency of 0.1 rad / sec to the complex viscosity measured at a frequency of 100 rad / sec was taken as the viscosity ratio. ~Strain hardening of extensional viscosity~ A viscoelasticity measuring device (product name MCR 702 MultiDrive manufactured by Anton Paar) was used. Sheets cut to a thickness of 0.5 mm, length of 20-15 mm, and width of 10 mm were heated to 140°C and stretched at a rate of 0.2 sec. -1 The sample was stretched uniaxially at 100°C, and the maximum value of the elongational viscosity (ηe-max) was read. The elongational viscosity (ηe-lin) without strain hardening is 0.01sec -1 from 100 seconds -1 The storage modulus (G') and loss modulus (G") were calculated using the following formula (2).

[0032] ηe-lin=G“(ω)+1.12G'(0.5ω)-0.20G'(ω) (2) The strain hardening ratio was calculated by dividing the maximum value of the elongational viscosity (ηe-max) by the elongational viscosity without strain hardening (ηe-lin). ~Evaluation of physical properties and moldability of extruded foam~ ~Heat of fusion~ A 5 mg test piece was cut from the extruded foam molded product obtained by molding a polyethylene resin, and the temperature was raised at a rate of 10°C / min using a heat flux differential scanning calorimeter (DS7000X, manufactured by Hitachi High-Tech Science). The heat of fusion at temperatures above 120°C was determined from the obtained DSC curve.

[0033] ~ Closed bubble rate ~ Using a dry-type automatic density meter (product name Accupyc II1340, manufactured by Shimadzu Corporation), the foam was cut into 4 cm lengths, the diameter was measured, and the volume (Vg) was calculated. Next, the volume (Vp1) of the foam was measured using the dry-type automatic density meter. Next, the foam used for measurement was cut into four 1 cm pieces, and the volume (Vp2) of the foam was measured. From Vp1 and Vp2, the open cells during the sample preparation process were calculated using the following formula (3).

[0034] Voc = Vg - 2Vp1 + Vp2 (3) Next, the volume of the closed cells alone (Vc) was calculated from the density (D) and weight (W) of the sample using the following formula (4), and the closed cell ratio (Cc) was calculated using formula (5).

[0035] Vc=Vg-W / D-Voc (4) Cc=Vc / Vg×100 (5) ~Foaming ratio~ A foamed piece 5 cm long was cut out from an extruded foam rod obtained by molding a polyethylene resin, and the diameter, length, and weight (Wg) of the foamed piece were measured. The apparent density was calculated using the following formula (6) in accordance with JIS K 6767.

[0036] Apparent density (g / cm 3 )=W / (radius × radius × π × length) (6) The expansion ratio was calculated from the apparent density using the following formula (7).

[0037] Expansion ratio = 1 / apparent density (7) ~Heat resistance~ The extruded foam molded product was cut into pieces 10 cm on a side and the length was measured. The cut foam was placed in an oven heated to 120°C for 24 hours, then removed and left at room temperature for 24 hours, after which the length of the foam was measured and the shrinkage rate was calculated using the following formula (8). Foam molded products with a shrinkage rate of 5% or less were considered to have good heat resistance.

[0038] Shrinkage rate (%) = (length before test - length after test) / length before test × 100 (8) ~Compression recovery~ The extruded foam was cut into a piece 10 cm on a side, and the center portion was compressed with a finger to about half its thickness, after which the recovery was evaluated visually.

[0039] Example 1 (1) Manufacture of polyethylene resins Linear low-density polyethylene: Trade name Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 30% by weight of high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 220K (manufactured by Tosoh Corporation, MFR 1.1 g / 10 min, density 931 kg / m 3 ) 40% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 208 (manufactured by Tosoh Corporation, MFR 24 g / 10 min, density 924 kg / m 3 The mixture was dry-blended at a ratio of 30% by weight, and then melt-mixed in a 25 mm diameter twin-screw extruder manufactured by The Japan Steel Works, Ltd. at a screw rotation speed of 250 rpm to obtain pellets. The cylinder temperature was set to 200°C, and the die head temperature was set to 210°C. (2) Manufacturing foam molded articles made from polyethylene resins 100 parts by weight of the polyethylene resin was dry-blended with 1 part by weight of a sodium bicarbonate-based chemical foaming agent (trade name: Polythrene EE275F, manufactured by Eiwa Chemical Industry Co., Ltd.) as a bubble-generating agent and 2 parts by weight of Rikemaster as a shrinkage inhibitor. 3 parts by weight of the blend were forced into the cylinder of a single-screw extruder set at a cylinder temperature of 150°C and a die temperature of 115°C using a constant-volume feeder, and extruded from a nozzle with a diameter of 3 mm to form a rod-shaped foamed molded article.

[0040] The polyethylene resin had a melt tension of 78 mN, a complex viscosity ratio of 1.5, a loss tangent of 1.8, a viscosity ratio × MFR of 34, and one crystallization peak. The extensional viscosity exhibited strain hardening, with a strain hardening ratio of 2.2. The activation energy was 41 kJ / mol, the MFR was 2.6 g / 10 min, and the density was 931 kg / m. 3 The heat of fusion of the polyethylene resin foam molded product at 120°C or higher was 7 J / g, and the closed cell rate was 88%.

[0041] The obtained foamed molded article had excellent foaming moldability, a good surface smoothness, uniform cells, an expansion ratio of 15, a shrinkage rate of 5%, and excellent heat resistance. The results are shown in Table 1.

[0042] Example 2 The polyethylene resin was a linear low-density polyethylene (trade name: Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 , manufactured by Tosoh Corporation) 40% by weight, linear low-density polyethylene: Nipolon (registered trademark)-L M70 (MFR 20 g / 10 min, density 936 kg / m 3 20% by weight of high-pressure low-density polyethylene (trade name: Petrothene® 220K) (MFR 1.1 g / 10 min, density 931 kg / m 3 A foamed molded article was obtained in the same manner as in Example 1, except that the amount of the acrylic resin (manufactured by Tosoh Corporation) was 40% by weight.

[0043] The polyethylene resin had a melt tension of 71 mN, a complex viscosity ratio of 1.5, a loss tangent of 1.9, a viscosity ratio × MFR of 40, and one crystallization peak. The extensional viscosity exhibited strain hardening, with a strain hardening ratio of 2.6. The activation energy was 35 kJ / mol, the MFR was 2.9 g / 10 min, and the density was 932 kg / m. 3 The heat of fusion of the polyethylene resin foam molded product at 120°C or higher was 11 J / g, and the closed cell rate was 86%.

[0044] The obtained foamed molded article had excellent foaming moldability, an expansion ratio of 17 times, a shrinkage rate of 3%, and excellent heat resistance and compression recovery.

[0045] Example 3 The polyethylene resin was a linear low-density polyethylene (trade name: Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 50% by weight of high-pressure low-density polyethylene: Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m 3 40% by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation), trade name Petrothene (registered trademark) 208 (MFR 24 g / 10 min, density 924 kg / m 3 A foamed molded article was obtained in the same manner as in Example 1, except that the amount of the resin used was 10% by weight (manufactured by Tosoh Corporation).

[0046] The polyethylene resin had a melt tension of 76 mN, a complex viscosity ratio of 1.5, a loss tangent of 2.0, a viscosity ratio × MFR of 40, and one crystallization peak. The extensional viscosity exhibited strain hardening, with a strain hardening ratio of 2.2. The activation energy was 43 kJ / mol, the MFR was 2.7 g / 10 min, and the density was 931 kg / m. 3 The heat of fusion of the polyethylene resin foam molded product at 120°C or higher was 13 J / g, and the closed cell rate was 85%.

[0047] The obtained foamed molded article had excellent foaming moldability, an expansion ratio of 16 times, a shrinkage rate of 4%, and excellent heat resistance and compression recovery.

[0048] Example 4 The polyethylene resin was a linear low-density polyethylene (trade name: Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 60% by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation), trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m 330% by weight of high-pressure low-density polyethylene (trade name: Petrothene® 208) (MFR 24 g / 10 min, density 924 kg / m 3 A foamed molded article was obtained in the same manner as in Example 1, except that the amount of the resin used was 10% by weight (manufactured by Tosoh Corporation).

[0049] The polyethylene resin had a melt tension of 68 mN, a complex viscosity ratio of 1.5, a loss tangent of 2.4, a viscosity ratio x MFR of 25, and one crystallization peak. The extensional viscosity exhibited strain hardening, with a strain hardening ratio of 1.9. The activation energy was 39 kJ / mol, the MFR was 2.8 g / 10 min, and the density was 930 g / m. 3 The heat of fusion of the polyethylene resin foam molded product at 120°C or higher was 14 J / g, and the closed cell rate was 82%.

[0050] The obtained foamed molded article had excellent foaming moldability, an expansion ratio of 15 times, a shrinkage rate of 3%, and excellent heat resistance and compression recovery.

[0051] Example 5 The polyethylene resin was a linear polyethylene: trade name TOSOH-HMS (registered trademark) 10S53A (MFR 3.0 g / 10 min, density 935 kg / m 3 70% by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation), trade name Petrothene (registered trademark) 219 (MFR 3.0 g / 10 min, density 934 kg / m 3 A foamed molded article was obtained in the same manner as in Example 1, except that the amount of the acrylic resin (manufactured by Tosoh Corporation) was 30% by weight.

[0052] The polyethylene resin had a melt tension of 72 mN, a complex viscosity ratio of 1.9, a loss tangent of 1.8, a viscosity ratio × MFR of 45, and one crystallization peak. The extensional viscosity exhibited strain hardening, with a strain hardening ratio of 1.8. The activation energy was 40 kJ / mol, the MFR was 3.0 g / 10 min, and the density was 937 g / m. 3 The heat of fusion of the polyethylene resin foam molded product at 120°C or higher was 17 J / g, and the closed cell rate was 84%.

[0053] The obtained foamed molded article had excellent foaming moldability, an expansion ratio of 17 times, a shrinkage rate of 2%, and excellent heat resistance and compression recovery.

[0054] Comparative Example 1 The polyethylene resin was a linear low-density polyethylene (trade name: TOSOH-HMS (registered trademark) 10S53A (MFR 3.0 g / 10 min, density 935 kg / m 3 A foam molded article was produced in the same manner as in Example 1, except that the polyethylene resin was changed to 100% by weight of polyethylene terephthalate (manufactured by Tosoh Corporation). The polyethylene resin had a melt tension of 29 mN, a strain hardening ratio of 1.3, a complex viscosity ratio of 15, and a viscosity ratio × MFR of 36. The polyethylene resin foam molded article had a closed cell ratio of 25%.

[0055] The resulting foamed molded article had excellent heat resistance but poor compression recovery.

[0056] Comparative Example 2 The polyethylene resin was a high-pressure low-density polyethylene (trade name: Petrothene (registered trademark) 219) (MFR 3.0 g / 10 min, density 934 kg / m 3 A foam molded article was molded in the same manner as in Example 1, except that the polyethylene resin used was changed to a polyethylene terephthalate (manufactured by Tosoh Corporation). The melt tension was 65 mN, the strain-hardening ratio was 2.2, and the viscosity ratio × MFR was 64, resulting in a high expansion ratio. However, because the heat of fusion of the polyethylene resin was 0.1%, the resulting foam molded article melted when the shrinkage rate was measured, and it had poor heat resistance.

[0057] Comparative Example 3 Polyethylene resin: High density polyethylene: Trade name: Nipolon Hard (registered trademark) 5700 (MFR 1.0 g / 10 min, density 957 kg / m 3 60% by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation), trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m 3 , manufactured by Tosoh Corporation) 30% by weight, low-density polyethylene: trade name Petrothene (registered trademark) 208 (MFR 24 g / 10 min, density 924 kg / m 3An extruded foam was molded in the same manner as in Example 1, except that the amount of polyethylene resin was changed to 10% by weight (manufactured by Tosoh Corporation). The polyethylene resin had two crystallization peaks. The closed cell ratio of the polyethylene resin foam molded product was 18%.

[0058] The resulting foamed molded article had excellent heat resistance, but had a low expansion ratio and poor moldability.

[0059] Comparative Example 4 The polyethylene resin was a linear low-density polyethylene (trade name: Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 70% by weight of high-pressure low-density polyethylene (manufactured by Tosoh Corporation), trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m 3 20% by weight of high-pressure low-density polyethylene (trade name: Petrothene® 208) (MFR 24 g / 10 min, density 924 kg / m 3 A foam molded article was obtained in the same manner as in Example 1, except that 10% by weight of polyethylene-based resin (manufactured by Tosoh Corporation) was used. The polyethylene-based resin had a loss tangent of 3.1, a viscosity ratio × MFR of 21, and the closed cell rate of the polyethylene-based resin foam molded article was 30%.

[0060] The resulting foamed molded article had poor foam moldability.

[0061] Comparative Example 5 The polyethylene resin was a linear low-density polyethylene (trade name: Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m 3 Except for using 100% by weight of polyethylene-based resin (manufactured by Tosoh Corporation), foam molding was carried out in the same manner as in Example 1. The polyethylene-based resin had a loss tangent of 3.8, a strain hardening ratio of elongational viscosity of 1.0, and an activation energy of 24 kJ / mol.

[0062] No foamed molded article could be obtained with this polyethylene resin.

[0063] [Table 1] [Industrial Applicability]

[0064] The uses of the foamed molded article made of the polyethylene resin of the present invention are not particularly limited, and it can be suitably used as a heat insulating molded article such as a shock absorbing container, a building material, or a heating device.

Claims

1. A non-crosslinked foam molded article made of a polyethylene resin having a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, a complex viscosity ratio of 5 or less at 110°C to 100°C when the temperature is decreased from 140°C at a frequency of 0.1 Hz at 1°C / min in dynamic viscoelasticity measurement and a loss tangent of 3 or less at 110°C, a single peak of exothermic heat of crystallization in the range of 60°C to 130°C when the temperature is decreased from 180°C at 10°C / min in DSC measurement, and a heat of fusion of 5 J / g or more at 120°C or higher when the temperature is increased from room temperature at 10°C / min.

2. The polyethylene resin is subjected to a temperature change of 140°C at a strain rate of 0.2 sec. －１ 2. The non-crosslinked foam molded article according to claim 1, which has strain hardening of extensional viscosity and has a strain hardening ratio of extensional viscosity of 1.5 or more and 4.0 or less.

3. 2. The non-crosslinked foam molded article according to claim 1, wherein the polyethylene resin has a flow activation energy of 30 kJ / mol or more and 45 kJ / mol or less, measured at a temperature range of 140°C to 220°C.

4. The polyethylene resin has a melt flow rate (hereinafter referred to as MFR) of 0.5 g / 10 min or more and less than 8.0 g / 10 min, measured at 190° C. under a load of 21.2 N, and a density of 930 kg / m ３ More than 945kg / m ３ The non-crosslinked foam molded article according to claim 1, wherein:

5. 2. The non-crosslinked foam molded article according to claim 1, wherein the polyethylene resin has a value of 20 or more, calculated by multiplying the ratio of the complex viscosity at a frequency of 100 Hz to the complex viscosity at a frequency of 0.1 Hz at a temperature of 140°C, in a dynamic viscoelasticity measurement, by the MFR.

6. The non-crosslinked foam molded article according to claim 1, which has a closed cell content of 70% or more.

7. 7. The method for producing a non-crosslinked foam molded article according to any one of claims 1 to 6, wherein the polyethylene resin has a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min, a complex viscosity ratio of 5 or less at 110°C to 100°C when the temperature is decreased from 140°C at a frequency of 0.1 Hz at 1°C / min in dynamic viscoelasticity measurement and a loss tangent of 3 or less at 110°C, a single peak of exothermic heat of crystallization in the range of 60°C to 130°C when the temperature is decreased from 180°C at 10°C / min in DSC, and a heat of fusion of 5 J / g or more at 120°C or higher when the temperature is increased from room temperature at 10°C / min.

8. The method for producing a non-crosslinked foam molded article according to claim 7, wherein one or more gases selected from the group consisting of butane, carbon dioxide, nitrogen, and chlorofluorocarbon gases are used as the foaming agent.

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