JP6298326B2 - Composite resin particles, expandable particles, pre-expanded particles, and expanded molded articles - Google Patents

Description

  The present invention relates to composite resin particles, expandable particles, pre-expanded particles, and expanded molded articles. More specifically, the present invention is a composite that can provide a foamed molded article with improved ball drop impact value and reduced temperature dependence of various physical properties such as mechanical properties (drop impact compression resistance, drop impact resistance, etc.). The present invention relates to resin particles, expandable particles, pre-expanded particles, and a foam-molded product obtained from these particles.

  It is known that a foam molded body made of polystyrene resin is excellent in rigidity, heat insulation, light weight, water resistance and foam moldability. Therefore, this foaming molding is widely used as a buffer material or a heat insulating material for building materials. However, the foamed molded body made of polystyrene resin has a problem of poor chemical resistance and impact resistance.

  On the other hand, it is known that a foam molded article made of a polyethylene resin is excellent in chemical resistance and impact resistance. Therefore, this foaming molding is used for automobile-related parts. However, since polyethylene-based resins have poor foaming agent retention properties, it is necessary to precisely control the foam molding conditions. Therefore, there is a problem that the manufacturing cost is high. In addition, the foam molded body has a problem that the rigidity is inferior to that of a foam molded body made of polystyrene resin.

  In order to solve the problems of the foamed molded article made of the polystyrene resin and the polyethylene resin, a foamed molded article obtained from composite resin particles of a polystyrene resin and a polyethylene resin has been reported. This foam molded article combines the excellent rigidity and foam moldability of polystyrene-based resin with the excellent chemical resistance and impact resistance of polyethylene-based resin. Further, in Japanese Patent No. 4072553 (Patent Document 1) and Japanese Patent No. 4072554 (Patent Document 2), a composite resin particle containing a linear low-density polyethylene-based resin is foam-molded with improved impact resistance. It has been reported to give body.

Japanese Patent No. 4072553 Japanese Patent No. 4072554

  According to the composite resin particles described in the above publication, it is possible to provide a foamed molded article having improved impact resistance. However, it is desired to provide composite resin particles that can further improve the impact resistance of the foamed molded product in a wide temperature range.

As a result of reviewing the raw material of the foamed molded article, the inventors of the present invention have made it possible to incorporate medium density to high density polyethylene and linear low density polyethylene into the composite resin particles at a specific ratio, thereby expanding the foam. Surprisingly, it has been found that the impact resistance of the molded body can be further improved over a wide temperature range, and the present invention has been achieved.
Thus, according to the present invention, composite resin particles containing a polyethylene resin and a polystyrene resin,
The polyethylene-based resin and the polystyrene-based resin are included in a range of 50 to 20% by mass and 50 to 80% by mass, respectively, with respect to the total of these resins,
The polyethylene resin is a first polyethylene resin having a medium density to a high density in a range of 925 to 965 kg / m ³ , and a second polyethylene resin that is linear and has a lower density than the first polyethylene resin. Consisting of
The first polyethylene resin and the second polyethylene resin are included in a range of 90 to 30% by mass and 10 to 70% by mass with respect to the total of these resins ,
The composite resin particles are particles having a gel fraction suppressed to less than 5% by weight,
The composite resin particles, the seed particles made of polyethylene resin, the composite resin particles is provided, wherein Rukoto obtained by impregnating polymerizing a styrene monomer.

Furthermore, according to this invention, the expandable particle | grain characterized by including the said composite resin particle and a physical foaming agent is provided.
The present invention also provides pre-expanded particles obtained by pre-expanding the expandable particles.
Furthermore, there is provided a foam molded article obtained by subjecting the pre-expanded particles to in-mold foam molding.

According to the present invention, fluctuations in mechanical properties (for example, drop impact compression resistance and drop impact resistance) are suppressed in a range from low temperature to high temperature (for example, −35 to 65 ° C.), and impact resistance is improved. It is possible to provide composite resin particles, expandable particles and pre-expanded particles that can give the expanded molded article. Moreover, the foaming molding which the fluctuation | variation of the mechanical characteristic obtained from these particle | grains was suppressed, and the impact resistance improved can be provided.
Furthermore, in any of the following cases, the present invention can provide composite resin particles that can provide a foamed molded article in which fluctuations in mechanical properties are further suppressed and impact resistance is further improved.
(1) The second polyethylene resin has a density that is 15 kg / m ³ or more lower than the first polyethylene resin.
(2) The first polyethylene resin has a crystallization heat quantity of 140 mJ / mg or more, and the second polyethylene resin has a crystallization heat quantity of 120 mJ / mg or less.
(3) The composite resin particles are particles in which the gel fraction is suppressed to less than 5% by weight.
(4) The composite resin particles have an average particle diameter of 1.0 to 2.0 mm.
(5) The first polyethylene resin has two or more peaks in an elution temperature-elution amount curve by a continuous temperature rising elution fractionation method (TREF).
(6) The composite resin particles further contain carbon black in the range of 0.5 to 2.5% by mass.
(7) Composite resin particles are obtained by impregnating and polymerizing seed particles made of polyethylene resin with a styrene monomer.
Furthermore, in any of the following cases, the present invention can provide pre-expanded particles that can provide a foamed molded article in which fluctuations in mechanical properties are further suppressed and impact resistance is further improved.
(1) The polystyrene-based resin has a Z average molecular weight Mz in the range of 600,000 to 1,000,000 according to GPC measurement.
(2) The polystyrene-based resin has a weight average molecular weight Mw in the range of 250,000 to 450,000 as measured by GPC.

It is a typical TREF elution temperature-elution amount curve of the polyethylene-type resin which can be used for this invention. 6 is a molecular weight distribution curve of a first polyethylene resin used in Example 7. 6 is a molecular weight distribution curve of a second polyethylene resin used in Example 7. It is the schematic of the instrument for 50% compression generation load and 50% compression absorption energy measurement. It is the schematic of the instrument for 50% compression generation load and 50% compression absorption energy measurement.

(Composite resin particles)
The composite resin particle of the present invention contains a polyethylene resin and a polystyrene resin.
The method for combining the polyethylene resin and the polystyrene resin is not particularly limited, and various known methods can be used. Examples thereof include a method of kneading a polyethylene resin and a polystyrene resin, and a method of impregnating and polymerizing polyethylene resin particles with a styrene monomer.

(1) Polyethylene resin The polyethylene resin is a first polyethylene resin having a medium density to a high density in the range of 925 to 965 kg / m ³ , and a second resin that is linear and has a lower density than the first polyethylene resin. It is composed of polyethylene resin.
(A) First polyethylene resin The first polyethylene resin has a density in the range of 925 to 965 kg / m ³ . This density range is generally considered to be medium to high density in the polyethylene resin. A polyethylene resin having such a density has a feature that the temperature dependency of mechanical properties is smaller than that of other polyethylene resins. Specifically, mechanical properties hardly deteriorate even at a low temperature of −35 ° C., excellent cold resistance, and higher melting point and Vicat softening point than other polyethylene resins. Therefore, even at a high temperature of 65 ° C. It is possible to provide a foamed molded article that is hardly deteriorated in characteristics and excellent in heat resistance. When the density is less than 925 kg / m ³ , the heat resistance may be insufficient. When it is larger than 965 kg / m ³ , the melting point is too high, and foaming and molding may be difficult. A preferred density range is 935-960 kg / m ³ .

The first polyethylene resin has a number average molecular weight Mn in the range of 25,000 to 50,000, a Z average molecular weight Mz in the range of 700,000 to 1,300,000, and a range of 20 to 50 in terms of polystyrene. You may have Mz / Mn. The first polyethylene resin that can be suitably used in the present invention tends to have a large Mz relative to a general medium density to high density polyethylene resin. For this reason, Mz / Mn also tends to be larger than general medium density to high density polyethylene resins.
When Mn is less than 25,000, the impact resistance may be insufficient. When Mn is larger than 50,000, foaming and molding may be difficult. When Mz is less than 700,000, the heat resistance may be insufficient. When Mz is larger than 1,300,000, foaming and molding may be difficult. When Mz / Mn is less than 20, the temperature dependence of the mechanical properties may increase. When Mz / Mn is larger than 50, foaming and molding may be difficult. The range of preferable Mn is 25,000-48,000, More preferably, it is 28,000-48,000. Moreover, the range of preferable Mz is 80,000-120,000, More preferably, it is 100,000-110,000. Furthermore, the range of preferable Mz / Mn is 25-48, More preferably, it is 28-48.

The first polyethylene resin preferably has a weight average molecular weight Mw in the range of 150,000 to 250,000 and Mw / Mn in the range of 4.5 to 9.0 in terms of polystyrene. When Mw is less than 150,000, the impact resistance may be insufficient. When Mw is larger than 250,000, foaming and molding may be difficult. When Mw / Mn is less than 4.5, the temperature dependence of mechanical properties may increase. When Mw / Mn is greater than 9.0, foaming and molding may be difficult. A preferable range of Mw is 160,000 to 240,000, more preferably 200,000 to 240,000. Moreover, the range of preferable Mw / Mn is 4.5-8.5, More preferably, it is 4.8-7.1.
Further, this resin may have two or more peaks in an elution temperature-elution amount curve by a continuous temperature rising elution fractionation method (TREF). By having two or more peaks, it is possible to provide a foamed molded article in which the temperature dependence of mechanical properties is suppressed and the impact resistance is improved. Furthermore, the polyethylene resin preferably has two peaks. In particular, it is preferable that the peak on the high temperature side is between 85 and 100 ° C and the peak on the low temperature side is between 65 and 80 ° C among the two peaks. In addition, the typical TREF elution temperature-elution amount curve of the polyethylene-type resin described in the said gazette is shown in FIG.

  The first polyethylene resin is preferably a resin having a crystallization heat amount of 140 mJ / mg or more. Here, when the amount of heat of crystallization is less than 140 mJ / mg, the temperature dependence of the mechanical properties of the foamed molded product may increase. The range of the amount of crystallization heat is preferably 150 to 200 mJ / mg, more preferably 160 to 190 mJ / mg.

  The first polyethylene resin is preferably a resin having a melt flow rate in the range of 0.1 to 20 [measured at MFR (g / 10 min), 190 ° C., 2.16 kg load]. Here, a polyethylene resin having an MFR of less than 0.1 g / 10 minutes is not preferable because the expansion ratio is reduced. On the other hand, if it exceeds 20 g / 10 minutes, the melt tension becomes small and the foaming ratio is lowered, and the strength of the foamed molded product is also lowered. More preferable MFR is 1 to 10 g / 10 min, and still more preferable MFR is 2 to 5 g / 10 min.

Any known resin having a density in the above range can be used for the first polyethylene resin. Examples of the first polyethylene resin include an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms. Examples of the α-olefin having 3 to 8 carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcycloalkane). Pentane, vinylcyclohexane), cyclic olefins (eg, norbornene, norbornadiene), dienes (eg, butadiene, 1,4-hexadiene) and the like. The proportion of the component derived from the olefin having 3 to 8 carbon atoms in the polyethylene resin is not particularly limited, but is preferably 50% by mass or less, and more preferably 20% by mass or less. Styrene may be copolymerized with ethylene as long as the invention is not impaired.
Examples of known resins include medium density polyethylene and high density polyethylene such as Novatec HD series manufactured by Nippon Polyethylene, Evolue H series manufactured by Prime Polymer, Nipolon Hard series manufactured by Tosoh Corporation, and TOSOH-HMS series. It is done.

  As the method for producing the first polyethylene resin, any method can be used as long as it is possible to produce a polyethylene resin having a specific density. Examples include a multistage polymerization method in which the polymerization catalyst and / or polymerization conditions are changed in multiple stages, a polymerization method using a catalyst in which a plurality of polymerization catalysts are mixed, a method in which a plurality of polyethylene resins prepared with the same or different polymerization catalysts are blended, etc. be able to.

  Adjustment of the molecular weight, heat of crystallization, and MFR of the polyethylene-based resin can be arbitrarily made according to the manufacturing conditions themselves of the examples described later or minor variations in the condition factors. The minor fluctuation of the condition factor corresponds to, for example, changing a single polymerization catalyst component to a combination of a plurality of polymerization catalyst components, changing polymerization conditions, or the like. For example, it is possible to make different by controlling the polymerization temperature, the partial pressure of ethylene, the amount of molecular weight regulator such as hydrogen to be coexisting, the amount of comonomer to be added, etc. . For example, the molecular weight can be increased by decreasing the amount of a molecular weight modifier such as hydrogen, and can be decreased by increasing the amount of a molecular weight modifier such as hydrogen. Further, the amount of crystallization heat can be increased by increasing the polymerization temperature, and can be decreased by decreasing the polymerization temperature. Furthermore, MFR can be increased by increasing the amount of a molecular weight modifier such as hydrogen, and can be decreased by decreasing the amount of a molecular weight modifier such as hydrogen.

  In the first polyethylene resin, the first polyethylene resin having two peaks in the elution temperature-elution amount curve is available from, for example, Tosoh Corporation. In addition, as shown below, a polyethylene resin produced by the method described in JP 2010-24353 A can also be suitably used.

Examples of the polymerization catalyst used for the production of the first polyethylene resin include, for example, JP-A No. 2004-346304, JP-A No. 2005-248013, JP-A No. 2006-321991, JP-A No. 2007-169341, and 2008-. Examples thereof include polymerization catalysts described in Japanese Patent No. 050278 and polymerization catalysts in which they are combined by a known method.
In the production of the first polyethylene resin, the polymerization temperature is preferably −100 to 120 ° C., and particularly considering productivity, it is preferably 20 to 120 ° C., more preferably 50 to 120 ° C. 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.

  When using the 1st polyethylene resin which consists of ethylene and a C3-C8 alpha olefin, it is preferable that ethylene / C3-C8 alpha-olefin (molar ratio) is 1-200, More Preferably it is 3-100, More preferably, it is 5-50. It is also possible to adjust the molecular weight using hydrogen or the like during polymerization.

  Furthermore, the first polyethylene resin is preferably a resin obtained by polymerizing ethylene in the presence of a macromonomer. Specifically, it is obtained by copolymerizing an ethylene homopolymer having a vinyl group at the terminal or a macromonomer composed of a copolymer of ethylene and an olefin having 3 or more carbon atoms with an olefin having 2 or more carbon atoms. Polyethylene resin.

Here, the macromonomer preferably has 2,000 or more Mn and 2 to 5 Mw / Mn. Examples of the olefin having 3 or more carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcyclopentane, vinyl Cyclohexane) and the like. These olefins may be used alone or in combination of two or more. The olefin having 2 or more carbon atoms is selected from the ethylene and the α-olefin having 3 to 8 carbon atoms.
The Mn of the macromonomer is more preferably 5,000 or more, and further preferably 10,000 or more. The upper limit is preferably 100,000. Further, Mw / Mn is more preferably 2 to 4, and further preferably 2 to 3.5.

Furthermore, when the number of vinyl ends per 1000 methylene carbons as the main chain of the macromonomer is X and the number of saturated ends per 1000 methylene carbons as the main chain of the macromonomer is Y, the formula Z = X / [(( X represented by (X + Y) × 2] is preferably 0.25 to 1. Z is more preferably 0.5 to 1. It is well known to those skilled in the art that the number of vinyl ends and saturated ends can be measured by ¹ H-NMR, ¹³ C-NMR or FT-IR. For example, in the case of ¹³ C-NMR, vinyl ends have peaks at 114 ppm and 139 ppm, and saturated ends have peaks at 32.3 ppm, 22.9 ppm, and 14.1 ppm, and the number can be measured from these peaks.

By copolymerizing the macromonomer and the olefin, a first polyethylene resin suitable for use in the present invention can be obtained. Here, the ratio of the resin (resin A) derived from an olefin having 2 or more carbon atoms other than the macromonomer to the total resin is preferably 1 to 99% by mass, more preferably 5 to 90% by mass, and 30 to 80% by mass. Is more preferable. The ratio of the resin A can be measured by comparing the GPC chart of the resin with the GPC chart of the macromonomer. Specifically, the peak derived from the resin A is determined by comparing both charts, and the ratio of the area of the peak to the area of all the peaks corresponds to the ratio of the resin A.
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. The first polyethylene-based resin can be separated and recovered from the polymerization solvent by a conventionally known method after the polymerization is completed, and can be isolated by drying.

  The polymerization can be performed in a slurry state, a solution state, or a gas phase state. In particular, when the polymerization is performed in a slurry state, it is possible to efficiently and stably produce a first polyethylene resin having a uniform particle shape. it can. 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, and gasoline. Furthermore, olefins such as propylene, 1-butene, 1-hexene and 1-octene can be used as a solvent.

(B) Second polyethylene resin The second polyethylene resin is a linear resin having a lower density than the first polyethylene resin (for example, a linear low density polyethylene resin: LLDPE).
Since many first polyethylene resins have a small tensile fracture strain (for example, less than 500% as measured by JIS K6922-2), a foamed molded article having insufficient impact resistance may be obtained. Since the second polyethylene resin has a high tensile fracture strain, the inventors think that the impact resistance of the foamed molded product can be improved by using it together with the first polyethylene resin. Furthermore, the inventors have found that the effect is limited only by the combined use, and there is a specific range of the combined use.
The density of the second polyethylene resin is preferably in the range of 875 to 929 kg / m ³ . The density of the second polyethylene resin is preferably 15 kg / m ³ or more lower than the density of the first polyethylene resin.

  The second polyethylene-based resin is, in terms of polystyrene, a number average molecular weight Mn in the range of 65,000 to 90,000, a Z average molecular weight Mz in the range of 250,000 to 400,000, and Mz / in the range of 2 to 10. It is preferable to have Mn. When Mn is less than 65,000, the impact resistance may be insufficient. When Mn is larger than 90,000, foaming and molding may be difficult. When Mz is less than 250,000, the mechanical strength may be insufficient. When Mz is larger than 400,000, foaming and molding may be difficult. When Mz / Mn is less than 2, the heat resistance may be insufficient. When Mz / Mn is larger than 10, foaming and molding may be difficult. A more preferable range of Mn is 70,000 to 85,000. A more preferable range of Mz is 300,000-350,000. Furthermore, the more preferable range of Mz / Mn is 3-5.

  The second polyethylene resin preferably has a weight average molecular weight Mw in the range of 150,000 to 250,000 and Mw / Mn in the range of 1.5 to 8 in terms of polystyrene. When Mw is less than 150,000, the impact resistance may be insufficient. When Mw is larger than 250,000, foaming and molding may be difficult. When Mw / Mn is less than 1.5, the temperature dependence of the mechanical properties may increase. When Mw / Mn is larger than 8, foaming and molding may be difficult. A preferable Mw range is 180,000 to 220,000, and more preferably 180,000 to 200,000. Moreover, the range of preferable Mw / Mn is 2-5, More preferably, it is 2-3.

The second polyethylene resin is preferably a resin having a crystallization heat amount of 120 mJ / mg or less. Here, when the amount of heat of crystallization is greater than 120 mJ / mg, the temperature dependence of the mechanical properties of the foamed molded product may increase. The range of the amount of crystallization heat is preferably 70 to 120 mJ / mg, more preferably 85 to 115 mJ / mg.
The crystallization heat amount of the first polyethylene resin is preferably 30 mJ / mg larger than the crystallization heat amount of the second polyethylene resin. The inventors said that the temperature dependence of the mechanical properties of the foamed molded product can be reduced by adding the first polyethylene resin having a large crystallization heat amount to the second polyethylene resin having a small crystallization heat amount. Is thinking.

The second polyethylene resin is preferably a resin having a melt flow rate in the range of 0.1 to 20 [measured at MFR (g / 10 min), 190 ° C., 2.16 kg load]. Here, a polyethylene resin having an MFR of less than 0.1 g / 10 minutes is not preferable because the expansion ratio is reduced. On the other hand, if it exceeds 20 g / 10 minutes, the melt tension becomes small and the foaming ratio is lowered, and the strength of the foamed molded product is also lowered. More preferable MFR is 1 to 10 g / 10 min, and still more preferable MFR is 2 to 5 g / 10 min.
The inventors consider that the MFR of the second polyethylene resin is preferably close to the MFR of the first polyethylene resin in view of compatibility with the first polyethylene resin.

The second polyethylene resin is usually composed of an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 8 carbon atoms. Examples of the α-olefin having 3 to 8 carbon atoms include propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane (for example, vinylcycloalkane). Pentane, vinylcyclohexane), cyclic olefins (eg, norbornene, norbornadiene), dienes (eg, butadiene, 1,4-hexadiene) and the like. The proportion of the component derived from the olefin having 3 to 8 carbon atoms in the polyethylene resin is not particularly limited, but is preferably 50% by mass or less, and more preferably 20% by mass or less. Styrene may be copolymerized with ethylene as long as the invention is not impaired.
A commercially available resin can be used for the second polyethylene resin.

  The content ratio of the first polyethylene resin and the second polyethylene resin is 90 to 30% by mass for the former and 10 to 70% by mass for the latter with respect to the total of both resins. When the former ratio is larger than 90% by mass, the impact resistance may be insufficient. On the other hand, if it is less than 30% by mass, the temperature dependence of the mechanical properties may increase. The preferred former and latter content ratios are 80 to 40% by mass and 20 to 60% by mass, the more preferred former and latter content ratios are 80 to 50% by mass and 20 to 50% by mass, and the more preferred former and latter contents are. The content ratio is 80 to 60% by mass and 20 to 40% by mass.

(C) Other components The polyethylene resin may contain other resins without departing from the object of the present invention. Examples of other resins include α-olefin homopolymers and copolymers having 2 to 20 carbon atoms. Specifically, polypropylene, poly 1-butene, poly (4-methyl-1-pentene), poly 1-pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, propylene / 1-butene copolymer Polymer, ethylene / propylene / 1-butene copolymer, 4-methyl-1-pentene / ethylene copolymer, ethylene / propylene / polyene copolymer, various propylene block copolymers and propylene random copolymers Examples include coalescence. The blending ratio of these other resins is preferably 50% by mass or less, and more preferably 30% by mass or less, based on the total amount of polyethylene resin.
For polyethylene resins, colorants, stabilizers, fillers (reinforcing materials), higher fatty acid metal salts, flame retardants, antistatic agents, lubricants, natural or synthetic oils, waxes, UV absorbers, weather resistance as required Additives such as stabilizers, anti-fogging agents, anti-blocking agents, slip agents, coating agents, and neutron shielding agents may be included. Among these, as the colorant, both inorganic and organic colorants (pigments or dyes) can be used. In particular, inorganic colorants such as iron oxide and carbon black are preferred.

Examples of carbon black include furnace black, channel black, thermal black, acetylene black, graphite, and carbon fiber.
Carbon black may be present in the composite resin particles by adding it as a so-called masterbatch in which carbon black is dispersed in a base resin during the production of the composite resin particles. The master batch preferably contains carbon black in a proportion of 30 to 50 parts by mass, more preferably 35 to 45 parts by mass with respect to 100 parts by mass of the master batch. The base resin contained in the master batch is preferably a polyethylene resin.
Carbon black is preferably contained in the range of 1 to 25% by mass in the polyethylene resin. If it is less than 1% by mass, the polyethylene resin may not be sufficiently colored. When it is more than 25% by mass, it tends to be difficult to mix in the polyethylene resin. A more preferable content is in the range of 2 to 15% by mass.

A stabilizer plays the role which prevents oxidation deterioration, thermal deterioration, etc., and can use all well-known things. For example, a phenol type stabilizer, an organic phosphite type stabilizer, a thioether type stabilizer, a hindered amine type stabilizer, etc. are mentioned.
Examples of the filler include talc and glass, and the shape is not particularly limited, such as a spherical shape, a plate shape, or a fiber shape.
Examples of higher aliphatic metal salts include salts of higher fatty acids such as stearic acid, oleic acid, and lauric acid with alkaline earth metals (magnesium, calcium, barium, etc.) and alkali metals (sodium, potassium, lithium, etc.). It is done.

(2) Polystyrene resin Examples of the polystyrene resin include resins derived from styrene monomers such as styrene monomer, α-methylstyrene, p-methylstyrene, and t-butylstyrene. Furthermore, the polystyrene resin may be a component composed of a copolymer of a styrene monomer and another monomer copolymerizable with the styrene monomer. Examples of other monomers include polyfunctional monomers such as divinylbenzene, and (meth) acrylic acid alkyl esters that do not contain a benzene ring in the structure such as butyl (meth) acrylate. You may use these other monomers in the range which does not exceed 5 mass% with respect to a polystyrene-type resin.

  The amount of the polyethylene resin and the polystyrene resin is 50 to 20% by mass and 50 to 80% by mass, respectively, where the total of both resins is 100% by mass. In addition, when the amount of the polystyrene resin exceeds 80% by mass, the chemical resistance and impact resistance of the foamed molded product may be deteriorated. When it is less than 50% by mass, the rigidity of the foamed molded product may be lowered. Preferable amounts are 40 to 20% by mass and 60 to 80% by mass, and more preferable amounts are 40 to 30% by mass and 60 to 70% by mass.

(3) Shape The shape of the composite resin particle is preferably cylindrical, substantially spherical or spherical, and the average particle diameter is preferably 1.0 to 2.0 mm. The shape is more preferably substantially spherical or spherical to improve the filling property.
When the average particle diameter is less than 1.0 mm, when used for expandable particles, the retention of the physical foaming agent is lowered and it is difficult to reduce the density. When it exceeds 2.0 mm, when used for pre-expanded particles, the filling property into the mold for molding tends to be deteriorated, and it is also difficult to reduce the thickness of the foam molded article.
(4) Others The composite resin particles preferably have a gel fraction suppressed to 5% by weight or less. By being suppressed, the recyclability of the foam-molded product derived from the particles can be improved.

(Expandable particles)
The expandable particles are particles obtained by impregnating the composite resin particles with a physical foaming agent. Examples of the physical foaming agent include propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane, hexane, dimethyl ether and the like. These physical foaming agents can be used alone or in admixture of two or more. It is preferable that content of a physical foaming agent is 5-25 mass parts with respect to 100 mass parts of composite resin particles.
The average particle diameter of the expandable particles can be approximately the same as that of the composite resin particles. Further, the shape is more preferably approximately spherical or spherical in order to improve the filling property.

(Pre-expanded particles)
Pre-expanded particles are particles obtained by pre-expanding the expandable particles.
The pre-expanded particles preferably have a bulk density of 20 to 200 kg / m ³ . When the bulk density is less than 20 kg / m ³ , the closed cell ratio may be lowered when foamed, and the strength of the foamed molded product obtained from the pre-foamed particles may be lowered. On the other hand, if it is greater than 200 kg / m ³ , the resulting foamed molded product may not be reduced in weight. A more preferable bulk density is 25 to 100 kg / m ³ . The method for measuring the bulk density is described in the column of Examples.

It is preferable that Z average molecular weight Mz by the GPC measurement of the polystyrene-type resin which comprises pre-expanded particle is 600,000-1,000,000. When Mz is lower than 600,000, the strength of the foamed molded product may be lowered, which is not preferable. On the other hand, if it is higher than 1,000,000, the secondary foaming property of the pre-foamed particles is lowered, the fusion property between the pre-foamed particles is lowered, and the strength of the foamed molded product may be lowered. A more preferable Z average molecular weight Mz is 700,000 to 900,000.
It is preferable that the weight average molecular weight Mw by GPC measurement of a polystyrene-type resin is 250,000-450,000. When Mw is lower than 250,000, the strength of the foamed molded product may be lowered, which is not preferable. On the other hand, when it is higher than 450,000, the secondary foaming property of the pre-foamed particles is lowered, the fusion property between the pre-foamed particles is lowered, and the strength of the foamed molded product may be lowered. A more preferred weight average molecular weight Mw is 300,000 to 400,000.

(Foamed molded product)
The foam molded article is a molded article obtained by subjecting the above pre-expanded particles to in-mold foam molding. In addition to excellent chemical resistance, impact resistance, and rigidity, the foam molded article has further improved temperature dependency.
As an evaluation test of the temperature dependence of the mechanical characteristics, for example, there is a Dynatap impact compression test based on ASTM D3763-92.
First, in the Dynatap impact compression test, the ratio Q ₋₃₅ / Q ₂₃ of the generated load Q ₋₃₅ and Q ₂₃ at the time of 50% compression when evaluated at −35 ° C. and 23 ° C. can be 1.22 or less. . Further, the ratio Q ₆₅ / Q ₂₃ of the 50% compression generated load Q ₂₃ and Q ₆₅ when evaluated at 23 ° C. and 65 ° C. can be 0.77 or more.
Next, in the Dynatap impact compression test, the ratio E ₋₃₅ / E ₂₃ of 50% compression absorbed energy E ₋₃₅ and E ₂₃ when evaluated at −35 ° C. and 23 ° C. should be 1.22 or less. it can. Furthermore, the ratio E ₆₅ / E ₂₃ of the absorbed energy E ₂₃ and E ₆₅ at the time of 50% compression when evaluated at 23 ° C. and 65 ° C. can be 0.77 or more.
From the above test, according to the present invention, for example, it is possible to provide a foamed molded article having low temperature dependence of mechanical properties in the range of -35 ° C to 65 ° C.

Further, a first polyethylene system having a number average molecular weight Mn in the range of 25,000 to 50,000, a Z average molecular weight Mz in the range of 700,000 to 1,300,000, and Mz / Mn in the range of 20 to 50. The resin is used, and the content ratio of the first polyethylene resin and the second polyethylene resin is 90-30% by mass for the former, 10-70% by mass for the latter (more preferably, the former is 80-50% by mass, the latter 20 to 50% by mass), it is possible to provide a foamed molded article having a lower temperature dependency in the range of −35 ° C. to 65 ° C.
Specifically, first, in the Dynatap impact compression test, the ratio Q ₋₃₅ / Q ₂₃ of the generated load Q ₋₃₅ to Q ₂₃ when evaluated at −35 ° C. and 23 ° C. is 1.20 or less. It can be. Furthermore, the ratio Q ₆₅ / Q ₂₃ of the generated load Q ₂₃ and Q ₆₅ at the time of 50% compression when evaluated at 23 ° C. and 65 ° C. can be 0.80 or more.
Next, in the Dynatap impact compression test, the ratio E ₋₃₅ / E ₂₃ of 50% compression absorbed energy E ₋₃₅ and E ₂₃ when evaluated at −35 ° C. and 23 ° C. should be 1.20 or less. it can. Further, the ratio E ₆₅ / E ₂₃ of 50% compression absorbed energy E ₂₃ and E ₆₅ when evaluated at 23 ° C. and 65 ° C. can be 0.80 or more.

Moreover, according to this invention, the foaming molding which has the falling ball impact value by 25 cm or more by JISK7211 can be provided.
The foamed molded product preferably has a density of 20 to 200 kg / m ³ . When the density is less than 20 kg / m ³ , the strength may be lowered because the closed cell ratio increases. On the other hand, if it is greater than 200 kg / m ³ , the mass may increase. A more preferable density is 25 to 100 kg / m ³ . The method for measuring the density is described in the column of Examples.
The foamed molded product of the present invention can be used for various applications, but it can be used for bumper core materials, automotive cushioning materials such as door interior cushioning materials, electronic parts, various industrial materials including glass, food cushioning materials and transport containers, etc. It can be used for various applications. In particular, it can be suitably used for a vehicle cushioning material.

(Production method of composite resin particles, expandable particles, pre-expanded particles, and expanded molded article)
First, the composite resin particles can be formed by melt-kneading a polyethylene resin and a polystyrene resin, and cutting into particles. For example, the composite resin particles are preferably produced as follows.
That is, seed particles of the polyethylene resin, a styrene monomer, and a polymerization initiator as necessary are dispersed in the aqueous suspension. A styrene monomer and a polymerization initiator may be mixed and used in advance.

  The seed particles can be obtained by a known method. For example, if necessary, a polyethylene resin is melted and kneaded in an extruder together with an inorganic nucleating agent and an additive to obtain a strand, and the obtained strand is cut in air, cut in water, The method of granulating by cutting while heating is mentioned.

  The seed particles of the polyethylene resin are preferably cylindrical, substantially spherical or spherical, and preferably have an average particle diameter of 0.2 to 1.5 mm. Further, the shape is more preferably approximately spherical or spherical in order to improve the filling property. When the average particle diameter is less than 0.2 mm, when used for expandable particles, the retention of the foaming agent becomes low and it is difficult to reduce the density, which is not preferable. When it exceeds 1.5 mm, when it is used for pre-expanded particles, not only the filling property into the molding die is deteriorated, but also the foamed molded product tends to be thin.

Examples of the inorganic nucleating agent include talc, silicon dioxide, mica, clay, zeolite, calcium carbonate and the like. 2 mass parts or less are preferable with respect to 100 mass parts of polyethylene-type resin, and, as for the usage-amount of an inorganic nucleating agent, 0.2-1.5 mass parts is more preferable.
Examples of the aqueous medium constituting the aqueous suspension include water and a mixed medium of water and a water-soluble solvent (for example, lower alcohol).

  As the polymerization initiator, those generally used as an initiator for suspension polymerization of a styrene monomer can be used. For example, benzoyl peroxide, di-t-butyl peroxide, t-butylperoxybenzoate, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxy- Organic peroxides such as 3,5,5-trimethylhexanoate and t-butyl-peroxy-2-ethylhexyl carbonate. These polymerization initiators may be used alone or in combination of two or more.

  As for the usage-amount of a polymerization initiator, 0.1-0.9 mass part is preferable with respect to 100 mass parts of styrene-type monomers. If it is less than 0.1 part by mass, it may take too much time to polymerize the styrene monomer. Use of a polymerization initiator exceeding 0.9 parts by mass may lower the molecular weight of the polystyrene resin. A more preferable usage amount is 0.2 to 0.5 parts by mass.

  A dispersant may be added to the aqueous suspension as necessary. The dispersant is not particularly limited, and any known dispersant can be used. Specific examples include hardly soluble inorganic substances such as calcium phosphate, magnesium pyrophosphate, sodium pyrophosphate, magnesium oxide. Further, a surfactant such as sodium dodecylbenzenesulfonate may be used.

  Next, the obtained dispersion is heated to a temperature at which the styrene monomer does not substantially polymerize to impregnate the seed particles with the styrene monomer. The time for impregnating the styrene monomer inside the seed particles is suitably from 30 minutes to 2 hours. This is because if the polymerization proceeds before sufficient impregnation, a polymer powder of polystyrene resin is produced. The higher the temperature at which the monomer is not substantially polymerized, it is advantageous to increase the impregnation rate, but it is preferable to determine the temperature considering the decomposition temperature of the polymerization initiator.

Next, the styrene monomer is polymerized. The polymerization is not particularly limited, but is preferably performed at 105 to 140 ° C. for 1.5 to 5 hours. The polymerization is usually carried out in an airtight container that can be pressurized.
The impregnation and polymerization of the styrene monomer may be performed in a plurality of times. By dividing into multiple times, the generation of polystyrene polymer powder can be minimized.
Composite resin particles can be obtained by the above process. The inventors believe that the obtained composite resin particles have a polystyrene resin-rich interior and a polyethylene resin-rich outer shell, and thus have a positive influence on the physical properties of the foamed molded product.

Next, the expandable particles can be obtained by impregnating the composite resin particles during or after the polymerization with a physical foaming agent. This impregnation can be performed by a method known per se. For example, the impregnation during the polymerization can be performed by performing the polymerization reaction in a sealed container and press-fitting a physical foaming agent into the container. The impregnation after completion of the polymerization is performed by press-fitting a physical foaming agent in a sealed container.
Furthermore, the pre-expanded particles can be obtained by pre-expanding the expandable particles to a predetermined bulk density by a known method.
Further, the foam molded body can be obtained by filling the foamed particles with heat while fusing the pre-foamed particles by filling the pre-foamed particles into a mold of a foam molding machine and heating the foamed pre-foamed particles again. Water vapor can be suitably used as the heating medium.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, commercially available reagents were used. The preparation of the clay mineral treated with the organic compound, the preparation of the ethylene polymer production catalyst, the production of the ethylene polymer and the solvent purification were all carried out in an inert gas atmosphere. Further, all the solvents used were purified, dried and deoxygenated by a known method in advance. A hexane solution (0.714M) of triisobutylaluminum was manufactured by Tosoh Finechem.

  The measuring methods of various physical properties in the following examples are described below.

<Measurement of density of polyethylene resin>
The density is measured by the method described in JIS K6922-1: 1997 “Plastics—Polyethylene (PE) molding and extrusion materials—Part 1: Naming system and specification basis”.
<MFR of polyethylene resin>
MFR is a method described in JIS K6922-1: 1997 “Plastics—Polyethylene (PE) molding and extrusion materials—Part 1: Naming system and basis of specification”. Measure with 16kg load.

<Measurement of elution temperature-elution amount curve by TREF>
An internal mixer (made by Toyo Seiki Seisakusho Co., Ltd., trade name Lab Plast Mill), which is obtained by adding a heat-resistant stabilizer (Ibusanox 1010 ^™ ; 1500 ppm, Irgaphos 168 ^™ ; 1500 ppm, manufactured by Ciba Specialty Chemicals Co., Ltd.) to a polyethylene resin. Is kneaded for 30 minutes at 190 ° C. and 30 rpm in a nitrogen stream. The kneaded product is heated and dissolved in ODCB at 135 ° C. so that its concentration is 0.05 mass%. After 5 ml of this heated solution is injected into a column filled with glass beads, it is cooled to 25 ° C. at a cooling rate of 0.1 ° C./min, and the sample is deposited on the surface of the glass beads. Next, while flowing ODCB through the column at a constant flow rate, the column temperature is raised at a constant rate of 50 ° C./hr, and a sample that can be dissolved in the solution is prepared and eluted at each temperature.
At this time, the concentration of the sample in the solvent can be obtained by continuously detecting the absorption of methylene for the non-target stretching vibration with a wave number of 2925 cm ⁻¹ with an infrared detector. An elution temperature-elution amount curve can be obtained from the continuously detected concentration. TREF analysis is a very small amount of sample, and since it is possible to continuously analyze changes in the elution rate with respect to temperature changes, relatively fine peaks that cannot be detected by the fractionation method can be detected.

<Measurement of Z Average Molecular Weight (Mz), Weight Average Molecular Weight (Mw), Number Average Molecular Weight (Mn), Mz / Mn, and Mw / Mn of Polyethylene Resin>
The said value means the polystyrene (PS) conversion value measured by the internal standard method using the gel permeation chromatography (GPC).
Specifically, 10 mg of a sample is sealed in a filtration container (100 μm pore size) attached to a dissolution filtration apparatus (DF-8020 manufactured by Tosoh Corporation). A test tube was prepared by adding 6 mL of O-dichlorobenzene containing 0.05 wt% BHT (butylhydroxytoluene) to the test tube, sealing it, and dissolving it at 160 ° C. for 5 hours using DF-8020 manufactured by Tosoh Corporation And Measured using a chromatograph under the following measurement conditions, Mz, Mw and Mn were determined from a standard polystyrene calibration curve prepared in advance, and Mz / Mn and Mw / Mn were determined from the obtained average molecular weights. calculate.
Equipment used: HLC-8121GPC / HT manufactured by Tosoh Corporation
Guard column: Tosoh Corporation TSK guard column HHR (S) HT 1 (7.5 mm ID x 7.5 cm) x 1 Column: Tosoh TSKgel GMHHR-H (S) HT (7.8 mm ID) .. x 30 cm) x 2 Mobile phase: O-dichlorobenzene Sample flow rate: 1.0 mL / min
Reference flow rate: 0.5 mL / min
Detector: RI detector Sample concentration: 0.17 wt%
Injection volume: 300 μL
Measurement time: 40 min
Sampling pitch: 300 msec

(Set temperature of each part)
Solvent stocker: 50 ° C., system oven: 40 ° C., pre-oven: 145 ° C., column oven (column temperature): 145 ° C., sample table: 145 ° C., injection valve: 145 ° C., transformer line: 145 ° C., waste line: 145 ° C, detector: 145 ° C
Standard polystyrene samples for calibration curves are manufactured by Showa Denko KK, trade names “shodex” having weight average molecular weights of 5,620,000, 3,120,000, 1,250,000, 442,000, 131,000, 54, 000, 20,000, 7,590, 3,450, 1,320 are used.
The standard polystyrenes for the calibration curve were A (5,620,000, 1,250,000, 131,000, 20,000, 3,450) and B (31,220,000, 442,000, 54,000, 7, 590, 1,320), A is weighed 3 to 10 mg each and then dissolved in 50 mL O-dichlorobenzene, and B is also weighed 3 to 10 mg each and dissolved in 50 mL O-dichlorobenzene. A standard polystyrene calibration curve is obtained by injecting 300 μL of the prepared A and B lysates and preparing a calibration curve (third order equation) from the retention time obtained after measurement. Using the calibration curve, Mz, Mw and Mn is obtained, and Mz / Mn and Mw / Mn are calculated from the obtained average molecular weights.

<Measurement of melting point of polyethylene resin>
Measured by the method described in JIS K7121: 1987 “Method for Measuring Transition Temperature of Plastic”. However, the sampling method and temperature conditions are as follows.
Using a differential scanning calorimeter DSC6220 (made by SII Nanotechnology Inc.), about 6 mg of a sample is filled so that there is no gap at the bottom of an aluminum measurement container, and from 30 ° C. under a nitrogen gas flow rate of 20 mL / min. The temperature is lowered to −40 ° C., held for 10 minutes, heated from −40 ° C. to 220 ° C. (1st Heating), held for 10 minutes, then cooled from 220 ° C. to −40 ° C. (Cooling), held for 10 minutes and then from −40 ° C. A DSC curve is obtained when the temperature is raised to 220 ° C. (2nd Heating). All the temperature increases / decreases are performed at a rate of 10 ° C./min, and alumina is used as a reference material. In the present invention, the melting point is a value obtained by reading the temperature at the top of the melting peak observed in the 2nd Heating process.

<The amount of heat of crystallization of polyethylene resin>
Measured by the method described in JIS K7122: 1987 “Method for measuring the transition heat of plastic”. However, the sampling method and temperature conditions are as follows.
Using a differential scanning calorimeter DSC6220 (made by SII Nanotechnology Inc.), about 6 mg of a sample is filled so that there is no gap at the bottom of an aluminum measurement container, and from 30 ° C. under a nitrogen gas flow rate of 20 mL / min. The temperature is lowered to −40 ° C., held for 10 minutes, heated from −40 ° C. to 220 ° C. (1st Heating), held for 10 minutes, then cooled from 220 ° C. to −40 ° C. (Cooling), held for 10 minutes and then from −40 ° C. A DSC curve is obtained when the temperature is raised to 220 ° C. (2nd Heating). All temperature increases / decreases are performed at a rate of 10 ° C./min, and alumina is used as a reference material. In the present invention, the amount of crystallization heat is a value obtained from the area of the exothermic peak of the DSC curve observed in the cooling process. This amount of heat is calculated from the straight line connecting the point where the exothermic peak separates from the high temperature side baseline and the point where the exothermic peak returns to the low temperature side base line, and the area of the portion surrounded by the DSC curve.

<Gel fraction of composite resin particles>
The gel fraction (wt%) is measured as follows.
In a 200 mL eggplant flask, 1.0 g of composite resin particles are precisely weighed, 100 mL of toluene and 0.03 g of boiling stone are added, a cooling tube is attached, immersed in an oil bath maintained at 130 ° C. and refluxed for 24 hours. The solution is filtered through an 80 mesh (wire diameter φ0.12 mm) wire net before the solution is cooled. The wire mesh with resin insolubles was dried in a vacuum oven at 130 ° C. for 1 hour, then dried at −0.06 MPa at gauge pressure for 2 hours to remove toluene, cooled to room temperature, and then the weight of insoluble resin on the wire mesh Weigh accurately. The gel fraction (wt%) is determined by the following calculation formula.
Gel fraction (wt%) = weight of insoluble resin on wire mesh (g) / sample weight (g) × 100

<Average particle diameter of composite resin particles>
The average particle diameter is a value expressed by D50.
Specifically, using a low-tap type sieve shaker (manufactured by Iida Seisakusho Co., Ltd.), the mesh opening is 4.00 mm, 3.35 mm, 2.80 mm, 2.36 mm, 2.00 mm, 1.70 mm, 1. 40mm, 1.18mm, 1.00mm, 0.85mm, 0.71mm, 0.60mm, 0.50mm, 0.425mm, 0.355mm, 0.300mm, 0.250mm, 0.212mm and 0.180mm About 25 g of the sample is classified for 10 minutes with a JIS standard sieve (JIS Z8801), and the sample weight on the sieve mesh is measured. A cumulative weight distribution curve is created from the obtained results, and the particle diameter (median diameter) at which the cumulative weight is 50% is defined as the average particle diameter.

<Bulk density and bulk multiple of pre-expanded particles>
The bulk density of the pre-expanded particles is measured as follows.
First, pre-expanded particles are filled in a measuring cylinder to a scale of 500 cm ³ . However, the graduated cylinder is visually observed from the horizontal direction, and if at least one pre-expanded particle reaches the scale of 500 cm ³ , the filling is finished. Next, the mass of the pre-expanded particles filled in the graduated cylinder is weighed with two significant figures after the decimal point, and the mass is defined as W (g). The bulk density of the pre-expanded particles is calculated by the following formula.
Bulk density (kg / m ³ ) = W ÷ 500 × 1000
1000 times the reciprocal of the bulk density is the bulk multiple.

<Measurement of Z-average molecular weight (Mz) and weight-average molecular weight (Mw) of polystyrene resin>
The Z-average molecular weight (Mz) and the weight-average molecular weight (Mw) of the polystyrene-based resin mean polystyrene-converted average molecular weights measured using gel permeation chromatography (GPC). In the following, a method for measuring various average molecular weights of polystyrene-based resin in a foamed molded product is described. However, the foamed molded product is an aggregate of composite resin particles until the foamed molded product is produced from the composite resin particles. Since various average molecular weights do not change depending on the process, the various average molecular weights of the composite resin particles, the expandable particles and the pre-expanded particles are the same as those of the foamed molded product.
First, a foam molded body is sliced into 0.3 mm in thickness, 100 mm in length, and 80 mm in width with a slicer (FK-4N manufactured by Fujishima Koki Co., Ltd.), and this is handled as a sample for molecular weight measurement. Specifically, 3 mg of the sample was allowed to stand for 24 hours in 10 mL of tetrahydrofuran (THF) for complete dissolution, and the resulting solution was filtered through a nonaqueous 0.45 μm chromatodisc (13N) manufactured by GL. Measurement is performed using a chromatograph under the following measurement conditions, and the average molecular weight of the sample is determined from a standard polystyrene calibration curve prepared in advance. If it is not completely dissolved at that time, check whether it is completely dissolved every 24 hours (up to 72 hours in total). Is determined, and the molecular weight of the dissolved component is measured.
(Measurement condition)
Equipment used: Tosoh HLC-8320GPC EcoSEC system (with built-in RI detector)
Guard column: Tosoh TSKguardcolumn SuperHZ-H (4.6 mm ID × 2 cm) × 1 Column: Tosoh TSKgel SuperHZM-H (4.6 mm ID × 15 cm) × 2 Column temperature: 40 ° C.
System temperature: 40 ° C
Mobile phase: THF
Mobile phase flow rate: sample-side pump = 0.175 mL / min
Reference side pump = 0.175mL / min
Detector: RI detector Sample concentration: 0.3 g / L
Injection volume: 50 μL
Measurement time: 0-25min
Runtime: 25min
Sampling pitch: 200 msec

(Create a calibration curve)
The standard polystyrene samples for the calibration curve have a weight average molecular weight of 5,480,000, 3,840,000, 355,000, 102,000, 37,900, 9 manufactured by Tosoh Corporation and trade name “TSK standard POLYSTYRENE”. , 100, 2,630, 500, and those having a weight average molecular weight of 1,030,000, manufactured by Showa Denko KK and trade name “Shodex STANDARD” are used.
The standard polystyrene samples for the calibration curve were group A (1,030,000), group B (3,840,000, 102,000, 9,100, 500) and group C (5,480,000, 355,000). , 37,900, 2,630), Group A was weighed 5 mg and then dissolved in 20 mL of THF, Group B was also weighed 5 to 10 mg and then dissolved in 50 mL of THF, and Group C was also weighed 1 mg to 5 mg and then THF 40 mL. Dissolved in. The standard polystyrene calibration curve was obtained by injecting 50 μL each of the prepared A, B, and C solutions, and using the retention time obtained after the measurement, a calibration curve (tertiary equation) was obtained from the GPC workstation (EcoSEC-WS). The average molecular weight was calculated using the calibration curve.

<Density and multiple of foam molding>
The density of the foamed molded product is measured by the method described in JIS A9511: 1995 “Foamed Plastic Insulating Plate”.
1000 times the reciprocal of the density is a multiple.

<50% compression generated load at each test temperature and 50% compression absorbed energy at each test temperature>
The above values are measured in accordance with ASTM D3763-92 (Standard Test Method for High Speed Puncture Properties of Plastics Usage Load and Displacement Sensors). In the measurement, the following conditions are set.
Test device: Using a Dynatap impact test device GRC 8250 manufactured by General Research, the tip of the tap and the clamp are changed as follows.
The tip 1 of the tap (3500 lbs (15568N)) is formed from a φ1 / 2 inch hemispherical insert into a flat plate for compression test (upper side) 2 (made of stainless steel, length 45 mm × width 45 mm × height 15 mm, weight 225 g). See FIG.
A compression test flat plate (lower side) 3 (made of stainless steel) is attached instead of the clamp. The mounting position of the flat plate is such that the distance between the upper and lower compression test flat plates is 15 mm at the lower limit position of the crosshead. See FIG. In FIG. 5, 4 is a support, 5 is a test piece, and 6 is a tap.
Measurement method: The test piece shall be 35 mm long, 35 mm wide and 35 mm high without a full skin, and stored for at least 16 hours in an environment of -35 ° C ± 2 ° C, 23 ° C ± 2 ° C, 65 ° C ± 2 ° C before testing. To stabilize the product temperature. The thermostatic chamber attached to GRC 8250 is temperature-controlled at each test temperature -35 ° C ± 2 ° C, 23 ° C ± 2 ° C, 65 ° C ± 2 ° C, and the test piece is placed on a flat plate for compression test (lower side). The test is performed by dropping a tap whose tip is changed to a flat plate for compression test (upper side) at a test speed of 3.01 m / sec, a test load of 3.19 kg, and a falling weight distance of 46 cm.
Using the analysis software Impulse Data Acquisition, manually move the cursor on the measurement chart to the displacement of 17.5 mm, read the values of load and absorbed energy displayed on the upper right and upper left of the chart, The absorption energy value at 50% compression is used. Calculate the average of 5 tests.
The ratio Q _-35 / Q ₂₃ and Q ₆₅ and the ratio Q ₆₅ / Q _23, also 50% -compression absorbed energy E _-35 of Q ₂₃ when the resulting 50% compressive load generated Q _-35 and Q ₂₃ and E ₂₃ the ratio E ₆₅ / E ₂₃ of the ratio E _-35 / E ₂₃ and E ₆₅ and E ₂₃ is evaluated in the following criteria.
Q _-35 / Q ₂₃ and E _-35 / E ₂₃
○ (good): ratio is less than 1.20 Δ (possible): range where ratio is 1.20 or more and less than 1.22 × (impossible): ratio is 1.22 or more Q ₆₅ / Q ₂₃ and E ₆₅ / E ₂₃
○ (good): ratio is 0.80 or more Δ (possible): ratio is 0.77 or more and less than 0.80 × (impossible): ratio is less than 0.77

<Falling ball impact value of foam molding>
The falling ball impact strength is measured in accordance with the method described in JIS K7211: 1976 “General Rules for Hard Plastic Drop Weight Impact Test Method”.
The obtained foamed molded article is dried at a temperature of 50 ° C. for 1 day, and then a 40 mm × 215 mm × 20 mm (thickness) test piece (six surfaces are not covered) is cut out from the foamed molded article.
Next, both ends of the test piece are fixed with clamps so that the distance between the fulcrums is 150 mm, and a hard ball having a weight of 321 g is dropped from a predetermined height onto the center of the test piece to check whether the test piece is broken or not. Observe.
The test piece was tested by changing the falling height (test height) of the hard sphere at 5 cm intervals from the lowest height at which all five specimens were destroyed to the highest height at which all were not destroyed, and the falling ball impact value (cm), ie 50% The fracture height is calculated by the following formula.

H50 = Hi + d [Σ (i · ni) /N±0.5]
The symbols in the formula mean the following:
H50: 50% fracture height (cm)
Hi: Test height (cm) when the height level (i) is 0, and the height at which the test piece is expected to break d: Height interval (cm) when the test height is raised or lowered
i: Height level when Hi is 0 and increases or decreases by 1 (i =... -3, -2, -1, 0, 1, 2, 3,...)
ni: Number of test pieces destroyed (or not destroyed) at each level, whichever data is used (in the case of the same number, either may be used)
N: The total number of specimens that were destroyed (or not destroyed) (N = Σni), whichever data is used (in the case of the same number, either may be used)
± 0.5: Use a negative number when using destroyed data, and a positive number when using data that was not destroyed

The obtained falling ball impact value is evaluated according to the following criteria. The larger the falling ball impact value, the greater the impact resistance of the foamed molded product.
◎ (excellent): Falling ball impact value is 40 cm or more. ○ (Good): Falling ball impact value is in the range of 30 cm to less than 40 cm. △ (possible): Falling ball impact value is in the range of 25 cm to less than 30 cm. Less than 25cm

<Compressive strength of foam molding>
Measured by the method described in JIS K6767: 1999 “Foamed Plastics-Polyethylene-Test Method”. That is, using a Tensilon universal testing machine UCT-10T (manufactured by Orientec) and universal testing machine data processing UTPS-237 (manufactured by Softbrain), the specimen size is 50 × 50 × thickness 25 mm and the compression speed is 10. 0 mm / min (the moving speed per minute is as close to 50% of the specimen thickness as possible). The compressive stress (MPa) at the time of compressing 10% of the thickness is measured. The number of test pieces is 3, and the symbol “23/50” (temperature 23 ° C., relative humidity 50%) of JIS K7100: 1999 “Plastic-Conditioning and Testing Standards” (2 degrees standard atmosphere) After adjusting the state for 16 hours, the measurement is performed under the same standard atmosphere.
The compressive stress is calculated by the following formula.
σ ₁₀ = F ₁₀ / A ₀
σ ₁₀ : Compression stress (MPa)
F ₁₀ : Load at 10% deformation (N)
A ₀ : Initial cross-sectional area of the test piece (mm ² )

<Bending strength of foamed molded article and displacement at bending breaking point>
The bending strength and the amount of displacement at the bending break point are measured by the method described in JIS K7221-2: 1999 “Rigid foamed plastic—Bending test—Part 2: Determination of bending characteristics”. That is, using Tensilon universal testing machine UCT-10T (manufactured by Orientec Co., Ltd.) and universal testing machine data processing software UTPS-237 (manufactured by Softbrain Co., Ltd.), the test piece size is 75 × width 300 × thickness 25 mm The test surface is 10 mm / min, the pressure wedge is 10R, and the support base is 10R, and the distance between the fulcrums is 200 mm, and the surface of the test piece without skin is stretched and measured. The number of test pieces is five, and the symbol “23/50” (temperature 23 ° C., relative humidity 50%) of JIS K7100: 1999 “Plastic-Conditioning and Testing Standards” (2 degrees standard atmosphere) After adjusting the state for 16 hours, the measurement is performed under the same standard atmosphere.
The bending strength (MPa) is calculated by the following formula.
R = (1.5F _R × L / bd ² ) × 10 ³
R: Bending strength (MPa)
F _R : Maximum load (kN)
L: Distance between supporting points (mm)
b: Width of test piece (mm)
d: Test piece thickness (mm)
In this test, the fracture detection sensitivity was set to 0.5%, and when the decrease exceeded the set value of 0.5% (deflection: 30 mm) compared to the previous load sampling point, the previous sampling point was Measured as the displacement at the bending break point (mm), and the average of 5 tests is obtained.

The obtained bending fracture point displacement is evaluated according to the following criteria. It shows that the flexibility of a foaming molding is so large that a bending fracture point displacement amount is large.
◎ (excellent): Bending fracture point displacement 40 mm or more ○ (good): Bending fracture point displacement 30 mm or more and less than 40 mm △ (possible): Bending fracture point displacement 20 mm or more but less than 30 mm × (impossible) ): Bending fracture point displacement is less than 20 mm <Evaluation of Recyclability>
Recyclability was evaluated by pulverizing the obtained foamed molded article with a pulverizer, and then an extruder (compression kneading single screw extruder: CER40Y 3.7MB-SX, manufactured by Hoshi Plastic Co., Ltd., eye plate: φ2 mm × 1 hole ) And extruded, the number of times the strand is cut per hour is measured, and 5 times / 1 hour is defined as x and less than 5 times / 1 hour as ◯.

Example 1
100 parts by mass of first polyethylene resin (high density polyethylene: manufactured by Nippon Polyethylene, product name Novatec HD, product number HY540), second polyethylene resin (linear low density polyethylene LLDPE: manufactured by Nippon Polyethylene Co., Ltd., product name Harmolex, product number) (NF444A) 233 parts by mass and 36.7 parts by mass (manufactured by Dow Chemical Japan, product name 28E-40) as a carbon black masterbatch were charged into a tumbler mixer and mixed for 10 minutes.

Next, this resin mixture is supplied to a single screw extruder (model: CER40Y 3.7MB-SX, manufactured by Hoshi Plastic Co., Ltd., diameter 40 mmφ, die plate (diameter 1.5 mm)) and melt-kneaded at a temperature of 230 to 250 ° C. Then, it is cut into a cylindrical shape of 0.40 to 0.60 mg / piece (average 0.5 mg / piece) with a fan cutter (manufactured by Hoshi Plastics Co., Ltd., model: FCW-110B / SE1-N) by a strand cutting method, and polyethylene-based Seed particles made of resin were obtained.
Next, 30 g of magnesium pyrophosphate and 0.15 g of sodium dodecylbenzenesulfonate were dispersed in 1.9 kg of pure water in a 5 liter autoclave equipped with a stirrer to obtain a dispersion medium.

The seed particles (600 g) were dispersed in a dispersion medium at 30 ° C. and held for 10 minutes, and then heated to 60 ° C. to obtain a suspension.
Furthermore, 200 g of styrene monomer in which 0.44 g of dicumyl peroxide was dissolved as a polymerization initiator was added dropwise to this suspension over 30 minutes. After dropping, the styrene monomer was impregnated in the high density polyethylene resin particles by holding for 60 minutes. After impregnation, the temperature was raised to 130 ° C., and polymerization was carried out at this temperature for 2 hours (first polymerization).

  Next, an aqueous solution in which 0.65 g of sodium dodecylbenzenesulfonate was dissolved in 0.1 kg of pure water was added to the suspension lowered to 120 ° C., and then styrene unit in which 5.0 g of dicumyl peroxide was dissolved. 1200 g of the monomer was added dropwise over 5 hours. The total amount of styrene monomer was 233 parts by mass with respect to 100 parts by mass of seed particles. After the dropwise addition, 6.0 g of ethylene / bisstearic acid amide was added as a bubble regulator and held at 120 ° C. for 1 hour to impregnate the styrene monomer in the high-density polyethylene resin particles. After impregnation, the temperature was raised to 140 ° C., and this temperature was maintained for 3 hours for polymerization (second polymerization). As a result of this polymerization, composite resin particles could be obtained.

Subsequently, it cooled to 30 degrees C or less, and took out the composite resin particle from the autoclave. 2 kg of composite resin particles, 2 liters of water, and 0.50 g of sodium dodecylbenzenesulfonate were placed in a 5 liter autoclave equipped with a stirrer. Further, 520 ml (300 g) of butane (n-butane: isobutane = 7: 3 (mass ratio)) as a foaming agent was placed in an autoclave. Thereafter, the temperature was raised to 70 ° C., and the stirring was continued for 3 hours to obtain expandable particles.
Thereafter, the mixture was cooled to 30 ° C. or lower, and the expandable particles were taken out from the autoclave and dehydrated and dried.

Next, pre-expanded particles were obtained by pre-expanding the obtained expandable particles to a bulk density of 50 kg / m ³ . The obtained pre-expanded particles were allowed to stand at room temperature (23 ° C.) for 1 day, and then placed in a molding die having a size of 400 mm × 300 mm × 30 mm.
Then, 0.15 MPa water vapor was introduced for 50 seconds and heated, and then cooled until the surface pressure of the foamed molded product decreased to 0.01 MPa, to obtain a foamed molded product having a density of 50 kg / m ³ .
Both the appearance and fusion of the obtained foamed molded article were good.

Example 2
A foam molded article was obtained in the same manner as in Example 1 except that the bulk density and density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Example 3
Change the first polyethylene resin to Prime Polymer Evolu H SP3510, change the addition amount of the second polyethylene resin and carbon black masterbatch to 100 parts by mass and 22 parts by mass, and adjust the pressure during molding to 0 A foamed molded article was obtained in the same manner as in Example 2 except that the pressure was changed to .11 MPa. Both the appearance and fusion of the obtained foamed molded article were good.

Example 4
The mass ratio of the total amount of seed particles and styrene monomer was changed to 100: 400 (the amount of seed particles was 440 g, and the amounts of styrene monomers in the first polymerization and the second polymerization were 145 g and 1415 g). Other than changing the amount of milperoxide to 0.32 g and 5.52 g, respectively, dropping the styrene monomer of the second polymerization over 5 hours, and changing the bulk density and density to 25.0 kg / m ³ Produced a foamed molded article in the same manner as in Example 3. Both the appearance and fusion of the obtained foamed molded article were good.

Comparative Example 1
A foam molded article was obtained in the same manner as in Example 1 except that the first polyethylene resin was not used and the addition amount of the carbon black masterbatch was changed to 11 parts by mass. Both the appearance and fusion of the obtained foamed molded article were good.
Comparative Example 2
A foamed molded article was obtained in the same manner as in Comparative Example 1 except that the second polyethylene resin was changed to Nippon Polyethylene, product number kernel KF270, and the bulk density and density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Comparative Example 3
A foamed molded article was obtained in the same manner as in Example 4 except that the first polyethylene-based resin was not used and the addition amount of the carbon black masterbatch was changed to 11 parts by mass. Both the appearance and fusion of the obtained foamed molded article were good.

Example 5
[Preparation of modified hectorite]
After adding 3 liters of ethanol and 100 ml of 37% concentrated hydrochloric acid to 3 liters of water, 330 g (1.1 mol) of N, N-dimethyl-octadecylamine was added to the resulting solution and heated to 60 ° C. A hydrochloride solution was prepared. 1 kg of hectorite was suspended in this solution. The suspension was stirred at 60 ° C. for 3 hours, the supernatant was removed, and then washed with 50 L of 60 ° C. water. Thereafter, the particles were dried at 60 ° C. and 10 ⁻³ torr for 24 hours, and pulverized with a jet mill to obtain modified hectorite having an average particle diameter of 5.2 μm.
[Preparation of polymerization catalyst (p)]
500 g of the above modified hectorite is suspended in 1.7 liters of hexane, and 8.45 g (20.20 g) of 1,1,3,3-tetramethyldisiloxane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride. 0 mmol) and a hexane solution (0.714 M) of triisobutylaluminum (2.8 liters, 2 mol) was added, and the mixture was stirred at 60 ° C. for 3 hours. Thereafter, 15 mol% of diphenyl (1-cyclopentadienyl) (2,7 based on 1,1,3,3-tetramethyldisiloxane-1,3-diyl-bis (cyclopentadienyl) zirconium dichloride. -Di-tert-butyl-9-fluorenyl) zirconium dichloride 2.36 g (3.53 mmol) was added and stirred at room temperature for 6 hours. The supernatant was removed by standing, and a hexane solution (0.15M) of triisobutylaluminum was further added to finally obtain a catalyst slurry of 100 g / L.

[Preparation of polymerization catalyst (q)]
500 g of the modified hectorite was suspended in 1.7 liters of hexane, and 6.63 g (20.0 mmol) of propane-1,3-diylbis (cyclopentadienyl) zirconium dichloride and a hexane solution of triisobutylaluminum (0.714 M ) 2.8 liters (2 mol) of a mixed solution was added, and the mixture was stirred at 60 ° C. for 3 hours, and then 5 mol% of diphenylmethylene (1- 1 mol) with respect to propane-1,3-diylbis (cyclopentadienyl) zirconium dichloride. 0.58 g (1.05 mmol) of cyclopentadienyl) (9-fluorenyl) zirconium dichloride was added and stirred at room temperature for 6 hours. The supernatant was removed by standing, and a hexane solution (0.15M) of triisobutylaluminum was further added to finally obtain a catalyst slurry of 100 g / L.

[Manufacture of polyethylene resin]
Into a polymerization vessel having an internal volume of 540 liters, 300 liters of hexane and 1.6 liters of 1-butene were introduced, and the internal temperature of the autoclave was raised to 80 ° C. Polymerization is carried out by adding 74 ml of the polymerization catalyst (p) and 125 ml of the polymerization catalyst (q) to this autoclave and introducing an ethylene / hydrogen mixed gas (containing hydrogen: 1500 ppm) until the partial pressure becomes 0.9 MPa. Started. During the polymerization, an ethylene / hydrogen mixed gas was continuously introduced so that the partial pressure was maintained at 0.9 MPa. The polymerization temperature was controlled at 80 ° C. After 90 minutes from the start of polymerization, the internal pressure of the polymerization vessel was released, and the contents were filtered and dried to obtain 54 kg of a first polyethylene resin powder. The obtained powder was melt-kneaded and pelletized using a 50 mm diameter single screw extruder set at 200 ° C. to obtain pellets of the first polyethylene resin.

[Production of composite resin particles]
100 parts by mass of the first polyethylene resin pellets obtained above, 11 parts by mass of the second polyethylene resin (linear low density polyethylene LLDPE: manufactured by Nippon Polyethylene Co., Ltd., product name Harmolex, product number NF444A), and carbon black masterbatch Changed to 0 parts by mass, and changed the mass ratio of the seed particles and the total amount of styrene monomer to 100: 150 (the amount of seed particles is 760 g, and the amount of styrene monomer in the first polymerization and the second polymerization is 250 g and 990 g). The amount of dicumyl peroxide as a polymerization initiator was changed to 0.55 g and 4.46 g, respectively, and the styrene monomer of the second polymerization was dropped over 4 hours and 30 minutes, and the pressure during molding was adjusted to 0. A foamed molded article was obtained in the same manner as in Example 1 except that the pressure was changed to 10 MPa. Both the appearance and fusion of the obtained foamed molded article were good.

Example 6
A foamed molded article was obtained in the same manner as in Example 5 except that the bulk density and density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Example 7
Product name: TOSOH-HMS Grade name: 10S65B manufactured by Tosoh Corp. The foamed molded article was the same as in Example 5 except that the amount of the second polyethylene resin was changed to 43 parts by mass. Got. Both the appearance and fusion of the obtained foamed molded article were good.
Example 8
A foam molded article was obtained in the same manner as in Example 7 except that the bulk density and the density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Example 9
The first polyethylene resin was changed to Tosoh Corporation. Product name: TOSOH-HMS Grade name: 09S53B, the second polyethylene resin was changed to Nippon Polyethylene, product name kernel, product number KF270, and the amount added was 67 parts by mass. A foamed molded article was obtained in the same manner as in Example 8 except that the change was made. Both the appearance and fusion of the obtained foamed molded article were good.

Comparative Example 4
A foamed molded article was obtained in the same manner as in Example 5 except that the first polyethylene resin was not used. Both the appearance and fusion of the obtained foamed molded article were good.
Comparative Example 5
A foam molded article was obtained in the same manner as in Comparative Example 4 except that the bulk density and density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Example 10
Product name: TOSOH-HMS Grade name: 10S65B changed from the first polyethylene resin to Tosoh Corporation, and the addition amount of the second polyethylene resin and carbon black masterbatch changed to 25 parts by mass and 13.8 parts by mass, A foamed molded product was obtained in the same manner as in Example 1 except that the pressure during molding was changed to 0.11 MPa. Both the appearance and fusion of the obtained foamed molded article were good.

Example 11
A foamed molded article was obtained in the same manner as in Example 10 except that the bulk density and density were changed to 33.3 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
Example 12
First polyethylene resin made by Tosoh Corporation Product name: TOSOH-HMS Grade name: CK57, second polyethylene resin made by Nippon Polyethylene, product name kernel, product number KF270, second polyethylene resin and carbon black A foamed molded article was obtained in the same manner as in Example 11 except that the addition amount of the master batch was changed to 150 parts by mass and 22 parts by mass, and the pressure adjustment during molding was changed to 0.15 MPa. Both the appearance and fusion of the obtained foamed molded article were good.

Example 13
Changing the second polyethylene resin to Nippon Polyethylene, product name Harmolex, product number NF444A, changing the addition amount of the second polyethylene resin and carbon black masterbatch to 233 parts by mass and 36.7 parts by mass, A foam molded article was obtained in the same manner as in Example 12 except that the density and density were changed to 25.0 kg / m ³ . Both the appearance and fusion of the obtained foamed molded article were good.
In Tables 1 to 9, HDPE, LLDPE, PS and MB mean high density polyethylene (first polyethylene resin), linear low density polyethylene resin (second polyethylene resin), polystyrene and masterbatch, respectively. .

The following can be seen from Tables 5-7.
From an Example, the 1st polyethylene-type resin of medium density to a high density in the range of 925-965 kg / m < ³ > and the 2nd polyethylene-type resin which is linear and has a lower density than the said 1st polyethylene-type resin are included. It can be seen that the composite resin particles can provide a foamed molded article having temperature dependence of small mechanical properties, high falling ball impact value, compressive strength, bending strength and bending break point displacement.

1 Tap tip, 2 flat plate for compression test (upper side), 3 flat plate for compression test (lower side), 4 support, 5 test piece, 6 taps

Claims (11)

Composite resin particles containing a polyethylene resin and a polystyrene resin,
The polyethylene-based resin and the polystyrene-based resin are included in a range of 50 to 20% by mass and 50 to 80% by mass, respectively, with respect to the total of these resins,
The polyethylene resin is a first polyethylene resin having a medium density to a high density in a range of 925 to 965 kg / m ³ , and a second polyethylene resin that is linear and has a lower density than the first polyethylene resin. Consisting of
The first polyethylene resin and the second polyethylene resin are included in a range of 90 to 30% by mass and 10 to 70% by mass with respect to the total of these resins ,
The composite resin particles are particles having a gel fraction suppressed to less than 5% by weight,
Composite resin particles the composite resin particles, the seed particles made of polyethylene resin, characterized by Rukoto obtained by impregnating polymerizing a styrene monomer. 2. The composite resin particle according to claim 1, wherein the second polyethylene resin has a density of 15 kg / m ³ or more lower than that of the first polyethylene resin.   The composite resin particle according to claim 1 or 2, wherein the first polyethylene resin has a crystallization heat amount of 140 mJ / mg or more, and the second polyethylene resin has a crystallization heat amount of 120 mJ / mg or less. The composite resin particle according to any one of claims 1 to 3 , wherein the composite resin particle has an average particle diameter of 1.0 to 2.0 mm. The composite resin particle according to any one of claims 1 to 4 , wherein the first polyethylene-based resin has two or more peaks in an elution temperature-elution amount curve by a continuous temperature rising elution fractionation method (TREF). Composite resin particles according to the composite resin particles is any one of claims 1 to 5 further comprising carbon black in the range of 0.5 to 2.5 wt%. Expandable particles comprising the composite resin particles according to any one of claims 1 to 6 and a physical foaming agent. Pre-expanded particles obtained by pre-expanding the expandable particles according to claim 7 . The pre-expanded particles according to claim 8 , wherein the polystyrene-based resin has a Z average molecular weight Mz in the range of 600,000 to 1,000,000 as measured by GPC. The pre-expanded particles according to claim 9 , wherein the polystyrene-based resin has a weight average molecular weight Mw in the range of 250,000 to 450,000 as measured by GPC. A foam molded article obtained by in-mold foam molding of the pre-expanded particles according to any one of claims 9 to 10 .

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