Non-crosslinked foamed molded body comprising polyethylene-based resin

Abstract

Provided is a polyethylene-based resin composition that is to become a non-crosslinked polyethylene foamed molded body having a high expansion ratio and excellent compression durability and secondary processability.　This non-crosslinked foamed molded body comprises a polyethylene-based resin in which the melt tension is 50 mN or greater at 160°C and a take-up speed of 10 m / min, the ratio of the complex viscosity coefficients at 110°C and 100°C when the temperature has been reduced from 140°C by 1°C / min is 5 or less in a dynamic viscoelasticity measurement at a frequency of 0.1 Hz, the loss tangent at 110°C is 3 or less, according to DSC the heat production of crystallization has a single peak in the range 60°C-130°C when the temperature has been reduced from 180°C by 10°C / min, and the heat of fusion at 120°C or greater when the temperature has been increased from room temperature by 10°C / min is 5 J / g or greater.

Description

Non-crosslinked foam molded article made of polyethylene resin

[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.

[0002] Polyethylene 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, increasing interest in improving the recyclability of plastic materials has led to a growing demand for non-crosslinked polyethylene resin foams. The production of non-crosslinked, high-expansion-ratio polyethylene foams requires polyethylene with high melt tension. Therefore, it is 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 requiring 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, a blend of high-pressure low-density polyethylene with linear low-density polyethylene or high-density polyethylene has been proposed (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).

[0003] Japanese Patent Publication No. 60-222222 Japanese Patent Publication No. 2006-274038 Japanese Patent Publication No. 2006-096910 Japanese Patent Publication No. 2006-199872

[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. An object of the present invention is to overcome the drawbacks of the prior art and to provide a non-crosslinked polyethylene-based resin foam that has a high expansion ratio, excellent compression durability, and excellent secondary processability.

[0005] As a result of intensive research aimed at solving 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 exhibits excellent extrusion foamability, and can give a non-crosslinked polyethylene resin foam having excellent heat resistance and flexibility, thereby completing the present invention. That is, the present invention has the following aspects [1] to [8]. [1] A non-crosslinked foam molded article made of 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, 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-based resin has a melt tension of 50 mN or more at 160°C and a take-up speed of 10 m / min. －１ The non-crosslinked foam molded article according to [1], wherein the polyethylene resin has strain hardening of elongational viscosity at 140°C and 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 of 140°C to 220°C. [4] The non-crosslinked foam molded article according to [1] or [2], wherein 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 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 ３The non-crosslinked foam molded article according to any one of [1] to [3], which is made of a polyethylene-based resin having the following properties: [5] The non-crosslinked foam molded article according to any one of [1] to [4], wherein the polyethylene-based resin has a value, obtained by measuring a dynamic viscoelasticity, of 20 or more when multiplying the ratio of the complex viscosity at a frequency of 100 Hz to that at a frequency of 0.1 Hz at a temperature of 140°C by the 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], wherein 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 cooled 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 cooled 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 heated from room temperature at 10°C / min. [8] A 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 chlorofluorocarbons are used as the blowing agent.

[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.

[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, 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 and 100°C, when decreased from 140°C at a frequency of 0.1 Hz at a rate of 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. 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 undesirable.

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

[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 at least 20, preferably at least 30. 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, the present non-crosslinked foamed molded article has a high closed cell ratio and excellent compression recovery, and therefore, it is possible to obtain a foamed molded article at 140°C and a strain rate of 0.2 sec. －１ In the above, it is preferable that the foamed molded article is 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, since 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 having excellent flexibility and heat resistance, and therefore 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 a temperature range of 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 foam 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 obtained by blending a plurality of polyethylene resins may be used.

[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 a plurality of polyethylene resins are blended and used, a polyethylene resin that can be easily foamed can be obtained if the compatibility is high. Therefore, it is preferable 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 cell 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, since this results in a foam with a higher expansion ratio. The polyethylene resin may also contain 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, or 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, such as mixing using a Henschel mixer, V-blender, ribbon blender, or tumbler blender, or by further melt-kneading and granulating the mixture obtained by such a method using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, or the like.

[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 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. In particular, 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 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.

[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 described below. Measurement of MFR: Measurement was performed in accordance with JIS K6922-1 at a temperature of 190°C and a load of 2.16 kg. Density: Measurement was performed using a density gradient tube method in accordance with JIS K6922-1. Measurement of melt tension: A capillary viscometer (product name: Capilograph, manufactured by Toyo Seiki Seisakusho) was used. At 160°C, a strand was lowered from a die with a length (L) of 8 mm and a diameter (D) of 2.095 mm at a piston lowering speed of 10 mm / min and taken up at 10 m / min, and the take-up load was used as the melt tension. Measurement of 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. Samples were prepared by press-molding a 1 mm diameter sheet and cutting it into a 20 mm diameter piece. The sample was placed in the center of the jig, heated to 140°C for 3 minutes, and then the temperature was decreased at a rate of 1°C / min while applying vibration 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 - Using a sheet obtained by press-molding a polyethylene resin to a thickness of 0.2 mm, the sheet was heated at 200°C for 10 minutes and then cooled at a rate of 10°C / min using a heat flux differential scanning calorimeter (DS7000X, manufactured by Hitachi High-Tech Science). From the obtained DSC curve, the exothermic peaks that appear when the polyethylene crystallizes in the range of 60°C to 130°C were counted. Measurement of activation energy and viscosity ratio Using a sheet press-molded from a polyethylene resin to 1.0 mm, a cone plate with a diameter of 25 mm and a cone angle of 2 degrees was attached to a viscoelasticity measuring device (product name MCR 702 MultiDrive, manufactured by Anton Paar), and the storage modulus (G') and loss modulus (G") were measured at temperatures of 140°C, 160°C, 190°C, and 220°C at measurement frequencies ranging from 0.01 rad / sec to 100 rad / sec. Using this, 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 formula (1), where R is the gas constant.

[0031] Activation energy = 2.303 x R x B (1) The ratio of the complex viscosity at a frequency of 0.1 rad / sec measured at a temperature of 140°C to the complex viscosity 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. A sheet cut to a thickness of 0.5 mm, length of 20-15 mm x width of 10 mm was heated to 140°C and elongated at a rate of 0.2 sec. －１ The specimen was uniaxially stretched at 0.01 sec, and the maximum value of the elongational viscosity (ηe-max) was read. －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) + 1.12 G' (0.5 ω) - 0.20 G' (ω) (2) The strain hardening ratio was determined by dividing the maximum value of the extensional viscosity (ηe-max) by the extensional viscosity in the absence of strain hardening (ηe-lin). Evaluation of physical properties and moldability of extruded foam molded products Heat of fusion A 5 mg test piece was cut out from an extruded foam molded product obtained by molding a polyethylene resin, and the test piece was heated 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 of 120°C or higher was determined from the resulting DSC curve.

[0033] ~Closed Cell Ratio~ Using a dry automatic densitometer (product name Accupyc II1340, manufactured by Shimadzu Corporation), the foam was cut into a length of 4 cm, the diameter was measured, and the volume (Vg) was determined. Next, the volume (Vp1) of the foam was measured using the dry automatic densitometer. Next, the foam used for measurement was cut into four pieces with a length of 1 cm, and the volume (Vp2) of the foam was measured. From Vp1 and Vp2, the open cell ratio during the sample preparation process was calculated using the following formula (3):

[0034] Voc = Vg - 2Vp1 + Vp2 (3) Next, the volume of only the closed cells (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) ~Expansion Ratio~ A foamed piece having a length of 5 cm was cut out from an extruded foamed rod obtained by molding a polyethylene-based 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 this 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 ratio was calculated using the following formula (8). Foam molded products with a shrinkage ratio of 5% or less were considered to have good heat resistance.

[0038] Shrinkage rate (%) = (length before test - length after test) / length before test x 100 (8) Compression recovery property The extruded foam was cut into a piece with a side length of 10 cm, and the central part was compressed and deformed with a finger to about half the thickness, and then the recovery property was evaluated visually.

[0039] Example 1 (1) Production of polyethylene resin 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) 30% by weight, 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) were dry-blended at a ratio of 30% by weight, and the mixture was melt-mixed in a 25mmφ twin-screw extruder manufactured by Japan Steel Works at a screw rotation speed of 250 rpm to obtain pellets. The cylinder temperature was 200°C, and the die head was 210°C. (2) Production of foamed molded articles from polyethylene-based resins: 100 parts by weight of the polyethylene-based 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 was pressurized 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 quantitative feeder, and discharged from a 3mmφ nozzle to form rod-shaped foamed molded articles.

[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 polyethylene resin foam molded article had a heat of fusion of 7 J / g at 120° C. or higher and a closed cell rate of 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: A polyethylene resin was used as 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 , manufactured by Tosoh Corporation) 20% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 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 used 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 polyethylene resin foam molded article had a heat of fusion of 11 J / g at 120° C. or higher and a closed cell rate of 86%.

[0044] The resulting 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: A polyethylene resin was used as 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) 50% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m ３ , manufactured by Tosoh Corporation) 40% by weight, high-pressure low-density polyethylene: 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 acrylic resin used was 10% by weight.

[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 polyethylene resin foam molded article had a heat of fusion of 13 J / g at 120° C. or higher and a closed cell rate of 85%.

[0047] The resulting 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: A polyethylene resin was used as 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) 60% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m ３ , manufactured by Tosoh Corporation) 30% by weight, high-pressure low-density polyethylene: 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 acrylic resin used was 10% by weight.

[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 polyethylene resin foam molded article had a heat of fusion of 14 J / g at 120° C. or higher and a closed cell rate of 82%.

[0050] The resulting 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: A polyethylene resin was used as a linear polyethylene: trade name TOSOH-HMS (registered trademark) 10S53A (MFR 3.0 g / 10 min, density 935 kg / m ３ , manufactured by Tosoh Corporation) 70% by weight, high-pressure low-density polyethylene: 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 used 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 x 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 polyethylene resin foam molded article had a heat of fusion at 120° C. or higher of 17 J / g and a closed cell rate of 84%.

[0053] The resulting 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: A polyethylene resin was used as 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 ratio 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: A polyethylene resin was used as 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 (TOSOH Corporation). The melt tension was 65 mN, the strain hardening ratio was 2.2, and the viscosity ratio × MFR was 64, so the expansion ratio was high. However, because the heat of fusion of the polyethylene resin was 0.1%, the obtained foam molded article melted when the shrinkage rate was measured, and it had poor heat resistance.

[0057] Comparative Example 3: Polyethylene resin was replaced with high-density polyethylene: Nipolon Hard (registered trademark) 5700 (MFR 1.0 g / 10 min, density 957 kg / m ３60% by weight of high-pressure low-density polyethylene (trade name: Petrothene®) 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 ３ An 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 (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: A polyethylene resin was used as 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) 70% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 220K (MFR 1.1 g / 10 min, density 931 kg / m ３ , manufactured by Tosoh Corporation) 20% by weight, high-pressure low-density polyethylene: trade name Petrothene (registered trademark) 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 ratio of 21, and the polyethylene-based resin foam molded article had a closed cell ratio of 30%.

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

[0061] Comparative Example 5: A polyethylene resin was used as a linear low-density polyethylene: trade name Nipolon (registered trademark)-L M50 (MFR 3.0 g / 10 min, density 936 kg / m ３ Foam molding was carried out in the same manner as in Example 1, except that 100% by weight of polyethylene-based resin (manufactured by Tosoh Corporation) was used. 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]

[0064] While the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0065] The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2024-096099, filed on June 13, 2024, are hereby incorporated by reference as the disclosure of the present invention.

[0066] 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

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. 　 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.

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. 　 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:

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, as measured by dynamic viscoelasticity measurement. 　 The non-crosslinked foam molded article according to claim 1, which has a closed cell content of 70% or more.

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. 　 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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